Application of narrow-band television to industrial and commercial communications

Science.gov (United States)

Embrey, B. C., Jr.; Southworth, G. R.

1974-01-01

The development of narrow-band systems for use in space systems is presented. Applications of the technology to future spacecraft requirements are discussed along with narrow-band television's influence in stimulating development within the industry. The transferral of the technology into industrial and commercial communications is described. Major areas included are: (1) medicine; (2) education; (3) remote sensing for traffic control; and (5) weather observation. Applications in data processing, image enhancement, and information retrieval are provided by the combination of the TV camera and the computer.

Electron correlations in narrow energy bands: modified polar model approach

Directory of Open Access Journals (Sweden)

L. Didukh

2008-09-01

Full Text Available The electron correlations in narrow energy bands are examined within the framework of the modified form of polar model. This model permits to analyze the effect of strong Coulomb correlation, inter-atomic exchange and correlated hopping of electrons and explain some peculiarities of the properties of narrow-band materials, namely the metal-insulator transition with an increase of temperature, nonlinear concentration dependence of Curie temperature and peculiarities of transport properties of electronic subsystem. Using a variant of generalized Hartree-Fock approximation, the single-electron Green's function and quasi-particle energy spectrum of the model are calculated. Metal-insulator transition with the change of temperature is investigated in a system with correlated hopping. Processes of ferromagnetic ordering stabilization in the system with various forms of electronic DOS are studied. The static conductivity and effective spin-dependent masses of current carriers are calculated as a function of electron concentration at various DOS forms. The correlated hopping is shown to cause the electron-hole asymmetry of transport and ferromagnetic properties of narrow band materials.

Narrow band flame emission from dieseline and diesel spray combustion in a constant volume combustion chamber

KAUST Repository

Wu, Zengyang

2016-08-18

In this paper, spray combustion of diesel (No. 2) and diesel-gasoline blend (dieseline: 80% diesel and 20% gasoline by volume) were investigated in an optically accessible constant volume combustion chamber. Effects of ambient conditions on flame emissions were studied. Ambient oxygen concentration was varied from 12% to 21% and three ambient temperatures were selected: 800 K, 1000 K and 1200 K. An intensified CCD camera coupled with bandpass filters was employed to capture the quasi-steady state flame emissions at 430 nm and 470 nm bands. Under non-sooting conditions, the narrow-band flame emissions at 430 nm and 470 nm can be used as indicators of CH∗ (methylidyne) and HCHO∗ (formaldehyde), respectively. The lift-off length was measured by imaging the OH∗ chemiluminescence at 310 nm. Flame emission structure and intensity distribution were compared between dieseline and diesel at wavelength bands. Flame emission images show that both narrow band emissions become shorter, thinner and stronger with higher oxygen concentration and higher ambient temperature for both fuels. Areas of weak intensity are observed at the flame periphery and the upstream for both fuels under all ambient conditions. Average flame emission intensity and area were calculated for 430 nm and 470 nm narrow-band emissions. At a lower ambient temperature the average intensity increases with increasing ambient oxygen concentration. However, at the 1200 K ambient temperature condition, the average intensity is not increasing monotonically for both fuels. For most of the conditions, diesel has a stronger average flame emission intensity than dieseline for the 430 nm band, and similar phenomena can be observed for the 470 nm band with 800 K and 1200 K ambient temperatures. However, for the 1000 K ambient temperature cases, dieseline has stronger average flame emission intensities than diesel for all oxygen concentrations at 470 nm band. Flame emissions for the two bands have a

Head and hand detuning effect study of narrow-band against wide-band mobile phone antennas

DEFF Research Database (Denmark)

Bahramzy, Pevand; Pedersen, Gert Frølund

2014-01-01

Wide-band (WB) and narrow-band (NB) antennas in terms of performance are compared, when interacting with the user’s right head and hand (RHH). The investigations are done through experimental measurements, using standardised head phantom and hand. It is shown that WB antennas detune more than NB ...

Band gap narrowing and fluorescence properties of nickel doped SnO2 nanoparticles

International Nuclear Information System (INIS)

Ahmed, Arham S.; Shafeeq, M. Muhamed; Singla, M.L.; Tabassum, Sartaj; Naqvi, Alim H.; Azam, Ameer

2011-01-01

Nickel-doped tin oxide nanoparticles (sub-5 nm size) with intense fluorescence emission behavior have been synthesized by sol-gel route. The structural and compositional analysis has been carried out by using XRD, TEM, FESEM and EDAX. The optical absorbance spectra indicate a band gap narrowing effect and it was found to increase with the increase in nickel concentration. The band gap narrowing at low dopant concentration ( 2 -SnO 2-x alloying effect and for higher doping it may be due to the formation of defect sub-bands below the conduction band.

Multilayer Photonic Crystal for Spectral Narrowing of Emission

Directory of Open Access Journals (Sweden)

Zhanfang LIU

2017-08-01

Full Text Available Multilayer colloidal crystal has been prepared by the layer-by-layer deposition of silica microspheres on a glass slide. Each layer is a slab consisting of a fcc close-packed colloidal arrays. By properly choosing the sizes of spheres, the whole spectral feature of multilayer colloidal crystal can be tuned. Here, we engineered a multilayer superlattice structure with an effective passband between two stop bands. This gives a strong narrowing effect on emission spectrum. With the stop bands at the shortwave and longwave edges of emission spectrum, the passband in the central wavelength region can be regarded as a strong decrease of suppression effect and enhancement of a narrow wavelength region of emission. The spectral narrowing modification effect of suitably engineered colloidal crystals shows up their importance in potential application as optical filters and lasing devices.DOI: http://dx.doi.org/10.5755/j01.ms.23.3.16320

Nonstationary Narrow-Band Response and First-Passage Probability

DEFF Research Database (Denmark)

Krenk, Steen

1979-01-01

The notion of a nonstationary narrow-band stochastic process is introduced without reference to a frequency spectrum, and the joint distribution function of two consecutive maxima is approximated by use of an envelope. Based on these definitions the first passage problem is treated as a Markov po...

Narrow-band radio flares from red dwarf stars

Science.gov (United States)

White, Stephen M.; Kundu, Mukul R.; Jackson, Peter D.

1986-01-01

VLA observations of narrow-band behavior in 20 cm flares from two red dwarf stars, L726 - 8A and AD Leo, are reported. The flare on L726 - 8A was observed at 1415 and 1515 MHz; the flux and the evolution differed significantly at the two frequencies. The flare on AD Leo lasted for 2 hr at 1415 MHz but did not appear at 1515 MHz. The AD Leo flare appears to rule out a source drifting through the stellar corona and is unlikely to be due to plasma emission. In the cyclotron maser model the narrow-band behavior reflects the range of magnetic fields present within the source. The apparent constancy of this field for 2 hr is difficult to understand if magnetic reconnection is the source of energy for the flare. The consistent polarization exhibited by red dwarf flares at 20 cm may be related to stellar activity cycles, and changes in this polarization will permit measuring the length of these cycles.

Analysis of the outlook for using narrow-band spontaneous emission sources for atmospheric air purification

International Nuclear Information System (INIS)

Boyarchuk, K A; Karelin, A V; Shirokov, R V

2003-01-01

The outlook for using narrow-band spontaneous emission sources for purification of smoke gases from sulphur and nitrogen oxides is demonstrated by calculations based on a nonstationary kinetic model of the N 2 - O 2 - H 2 O - CO 2 - SO 2 mixture. The dependences of the mixture purification efficiency on the UV source power at different wavelengths, the exposure time, and the mixture temperature are calculated. It is shown that the radiation sources proposed in the paper will provide better purification of waste gases in the atmosphere. The most promising is a KrCl* lamp emitting an average power of no less than 100 W at 222 nm. (laser applications and other topics in quantum electronics)

Narrow-band radio flares from red dwarf stars

Energy Technology Data Exchange (ETDEWEB)

White, S.M.; Kundu, M.R.; Jackson, P.D.

1986-12-01

VLA observations of narrow-band behavior in 20 cm flares from two red dwarf stars, L726 - 8A and AD Leo, are reported. The flare on L726 - 8A was observed at 1415 and 1515 MHz; the flux and the evolution differed significantly at the two frequencies. The flare on AD Leo lasted for 2 hr at 1415 MHz but did not appear at 1515 MHz. The AD Leo flare appears to rule out a source drifting through the stellar corona and is unlikely to be due to plasma emission. In the cyclotron maser model the narrow-band behavior reflects the range of magnetic fields present within the source. The apparent constancy of this field for 2 hr is difficult to understand if magnetic reconnection is the source of energy for the flare. The consistent polarization exhibited by red dwarf flares at 20 cm may be related to stellar activity cycles, and changes in this polarization will permit measuring the length of these cycles. 22 references.

1.7  μm band narrow-linewidth tunable Raman fiber lasers pumped by spectrum-sliced amplified spontaneous emission.

Science.gov (United States)

Zhang, Peng; Wu, Di; Du, Quanli; Li, Xiaoyan; Han, Kexuan; Zhang, Lizhong; Wang, Tianshu; Jiang, Huilin

2017-12-10

A 1.7 μm band tunable narrow-linewidth Raman fiber laser based on spectrally sliced amplified spontaneous emission (SS-ASE) and multiple filter structures is proposed and experimentally demonstrated. In this scheme, an SS-ASE source is employed as a pump source in order to avoid stimulated Brillouin scattering. The ring configuration includes a 500 m long high nonlinear optical fiber and a 10 km long dispersion shifted fiber as the gain medium. A segment of un-pumped polarization-maintaining erbium-doped fiber is used to modify the shape of the spectrum. Furthermore, a nonlinear polarization rotation scheme is applied as the wavelength selector to generate lasers. A high-finesse ring filter and a ring filter are used to narrow the linewidth of the laser, respectively. We demonstrate tuning capabilities of a single laser over 28 nm between 1652 nm and 1680 nm by adjusting the polarization controller (PC) and tunable filter. The tunable laser has a 0.023 nm effective linewidth with the high-finesse ring filter. The stable multi-wavelength laser operation of up to four wavelengths can be obtained by adjusting the PC carefully when the pump power increases.

Band gap narrowing and fluorescence properties of nickel doped SnO{sub 2} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Arham S; Shafeeq, M Muhamed [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z. H. College of Engineering and Technology, Aligarh Muslim University, Aligarh-202002 (India); Singla, M L [Central Scientific Instruments Organization (CSIO), Council of Scientific and Industrial Research (CSIR), Materials Research and Bio-Nanotechnology Division, Sector - 30/C, Chandigarh-160030 (India); Tabassum, Sartaj [Department of Chemistry, Aligarh Muslim University, Aligarh-202002 (India); Naqvi, Alim H [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z. H. College of Engineering and Technology, Aligarh Muslim University, Aligarh-202002 (India); Azam, Ameer [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z. H. College of Engineering and Technology, Aligarh Muslim University, Aligarh-202002 (India)

2011-01-15

Nickel-doped tin oxide nanoparticles (sub-5 nm size) with intense fluorescence emission behavior have been synthesized by sol-gel route. The structural and compositional analysis has been carried out by using XRD, TEM, FESEM and EDAX. The optical absorbance spectra indicate a band gap narrowing effect and it was found to increase with the increase in nickel concentration. The band gap narrowing at low dopant concentration (<5%) can be assigned to SnO{sub 2}-SnO{sub 2-x} alloying effect and for higher doping it may be due to the formation of defect sub-bands below the conduction band.

O2 atmospheric band measurements with WINDII: Performance of a narrow band filter/wide angle Michelson combination in space

International Nuclear Information System (INIS)

Ward, W.E.; Hersom, C.H.; Tai, C.C.; Gault, W.A.; Shepherd, G.G.; Solheim, B.H.

1994-01-01

Among the emissions viewed by the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS) are selected lines in the (0-0) transition of the O2 atmospheric band. These lines are viewed simultaneously using a narrow band filter/wide-angle Michelson interferometer combination. The narrow band filter is used to separate the lines on the CCD (spectral-spatial scanning) and the Michelson used to modulate the emissions so that winds and rotational temperatures may be measured from the Doppler shifts and relative intensities of the lines. In this report this technique will be outlined and the on-orbit behavior since launch summarized

f-band narrowing in uranium intermetallics

International Nuclear Information System (INIS)

Dunlap, B.D.; Litterst, F.J.; Malik, S.K.; Kierstead, H.A.; Crabtree, G.W.; Kwok, W.; Lam, D.J.; Mitchell, A.W.

1987-01-01

Although the discovery of heavy fermion behavior in uranium compounds has attracted a great deal of attention, relatively little work has been done which is sufficiently systematic to allow an assessment of the relationship of such behavior to more common phenomena, such as mixed valence, narrow-band effects, etc. In this paper we report bulk property measurements for a number of alloys which form a part of such a systematic study. The approach has been to take relatively simple and well-understood materials and alter their behavior by alloying to produce heavy fermion or Kondo behavior in a controlled way

Predicting soil nitrogen content using narrow-band indices from ...

African Journals Online (AJOL)

Optimal fertiliser applications for sustainable forest stand productivity management, whilst protecting the environment, is vital. This study estimated soil nitrogen content using leaf-level narrow-band vegetation indices derived from a hand-held 350–2 500 nm spectroradiometer. Leaf-level spectral data were collected and ...

Electronic band-gap modified passive silicon optical modulator at telecommunications wavelengths.

Science.gov (United States)

Zhang, Rui; Yu, Haohai; Zhang, Huaijin; Liu, Xiangdong; Lu, Qingming; Wang, Jiyang

2015-11-13

The silicon optical modulator is considered to be the workhorse of a revolution in communications. In recent years, the capabilities of externally driven active silicon optical modulators have dramatically improved. Self-driven passive modulators, especially passive silicon modulators, possess advantages in compactness, integration, low-cost, etc. Constrained by a large indirect band-gap and sensitivity-related loss, the passive silicon optical modulator is scarce and has been not advancing, especially at telecommunications wavelengths. Here, a passive silicon optical modulator is fabricated by introducing an impurity band in the electronic band-gap, and its nonlinear optics and applications in the telecommunications-wavelength lasers are investigated. The saturable absorption properties at the wavelength of 1.55 μm was measured and indicates that the sample is quite sensitive to light intensity and has negligible absorption loss. With a passive silicon modulator, pulsed lasers were constructed at wavelengths at 1.34 and 1.42 μm. It is concluded that the sensitive self-driven passive silicon optical modulator is a viable candidate for photonics applications out to 2.5 μm.

Band Edge Dynamics and Multiexciton Generation in Narrow Band Gap HgTe Nanocrystals.

Science.gov (United States)

Livache, Clément; Goubet, Nicolas; Martinez, Bertille; Jagtap, Amardeep; Qu, Junling; Ithurria, Sandrine; Silly, Mathieu G; Dubertret, Benoit; Lhuillier, Emmanuel

2018-04-11

Mercury chalcogenide nanocrystals and especially HgTe appear as an interesting platform for the design of low cost mid-infrared (mid-IR) detectors. Nevertheless, their electronic structure and transport properties remain poorly understood, and some critical aspects such as the carrier relaxation dynamics at the band edge have been pushed under the rug. Some of the previous reports on dynamics are setup-limited, and all of them have been obtained using photon energy far above the band edge. These observations raise two main questions: (i) what are the carrier dynamics at the band edge and (ii) should we expect some additional effect (multiexciton generation (MEG)) as such narrow band gap materials are excited far above the band edge? To answer these questions, we developed a high-bandwidth setup that allows us to understand and compare the carrier dynamics resonantly pumped at the band edge in the mid-IR and far above the band edge. We demonstrate that fast (>50 MHz) photoresponse can be obtained even in the mid-IR and that MEG is occurring in HgTe nanocrystal arrays with a threshold around 3 times the band edge energy. Furthermore, the photoresponse can be effectively tuned in magnitude and sign using a phototransistor configuration.

Narrow band interference cancelation in OFDM: Astructured maximum likelihood approach

KAUST Repository

Sohail, Muhammad Sadiq; Al-Naffouri, Tareq Y.; Al-Ghadhban, Samir N.

2012-01-01

This paper presents a maximum likelihood (ML) approach to mitigate the effect of narrow band interference (NBI) in a zero padded orthogonal frequency division multiplexing (ZP-OFDM) system. The NBI is assumed to be time variant and asynchronous

Choice of Eye-Safe Radiation Wavelength in UV and Near IR Spectral Bands for Remote Sensing

Directory of Open Access Journals (Sweden)

M. L. Belov

2016-01-01

Full Text Available The introduction of laser remote sensing systems carries a particular risk to the human’s sense of vision. A structure of the eye, and especially the retina, is the main critical organ as related to the laser radiation.The work uses the optical models of the atmosphere, correctly working in both the UV and the near-IR band, to select the eye-safe radiation wavelengths in the UV (0.355 m and near-IR (~ 1.54 and ~ 2 m spectral bands from the point of view of recorded lidar signal value to fulfill the tasks of laser sensing the natural formations and laser aerosol sensing in the atmosphere.It is shown that the remote sensing lasers with appropriate characteristics can be selected both in the UV band (at a wavelength of 0.355 μm and in the near-IR band (at wavelengths of 1.54 ~ or ~ 2 μm.Molecular scattering has its maximum (for the selected wavelength at a wavelength of 0.355 μm in the UV band, and the minimum at the wavelengths of 1.54 and 2.09 μm in the near -IR band. The main contribution to the molecular absorption at a wavelength of 0.355 μm is made by ozone. In the near-IR spectral band the radiation is absorbed due to water vapor and carbon dioxide.Calculations show that the total effect of the molecular absorption and scattering has no influence on radiation transmission for both the wavelength of 0.355 μm in the UV band, and the wavelengths of 1.54 and 2.09 μm in the near-IR band for sensing trails ~ 1 km.One of the main factors of laser radiation attenuation in the Earth's atmosphere is radiation scattering by aerosol particles.The results of calculations at wavelengths of 0.355 μm, 1.54 μm and 2.09 μm for the several models of the atmosphere show that a choice of the most effective (in terms of the recorded signal of lidar and eye-safe radiation wavelength depends strongly on the task of sensing.To fulfill the task of laser sensing the natural formations, among the eye-safe wavelengths there is one significantly advantageous

TES arrays for the short wavelength band of the SAFARI instrument on SPICA

Science.gov (United States)

Khosropanah, P.; Hijmering, R.; Ridder, M.; Gao, J. R.; Morozov, D.; Mauskopf, P. D.; Trappe, N.; O'Sullivan, C.; Murphy, A.; Griffin, D.; Goldie, D.; Glowacka, D.; Withington, S.; Jackson, B. D.; Audley, M. D.; de Lange, G.

2012-09-01

SPICA is an infra-red (IR) telescope with a cryogenically cooled mirror (~5K) with three instruments on board, one of which is SAFARI that is an imaging Fourier Transform Spectrometer (FTS) with three bands covering the wavelength of 34-210 μm. We develop transition edge sensors (TES) array for short wavelength band (34-60 μm) of SAFARI. These are based on superconducting Ti/Au bilayer as TES bolometers with a Tc of about 105 mK and thin Ta film as IR absorbers on suspended silicon nitride (SiN) membranes. These membranes are supported by long and narrow SiN legs that act as weak thermal links between the TES and the bath. Previously an electrical noise equivalent power (NEP) of 4×10-19 W/√Hz was achieved for a single pixel of such detectors. As an intermediate step toward a full-size SAFARI array (43×43), we fabricated several 8×9 detector arrays. Here we describe the design and the outcome of the dark and optical tests of several of these devices. We achieved high yield (<93%) and high uniformity in terms of critical temperature (<5%) and normal resistance (7%) across the arrays. The measured dark NEPs are as low as 5×10-19 W/√Hz with a response time of about 1.4 ms at preferred operating bias point. The optical coupling is implemented using pyramidal horns array on the top and hemispherical cavity behind the chip that gives a measured total optical coupling efficiency of 30±7%.

A high stability wavelength-tunable narrow-linewidth and single-polarization erbium-doped fiber laser using a compound-cavity structure

International Nuclear Information System (INIS)

Feng, Ting; Yan, Fengping; Peng, Wanjing; Liu, Shuo; Tan, Siyu; Liang, Xiao; Wen, Xiaodong

2014-01-01

A high stability wavelength-tunable narrow-linewidth and single-polarization erbium-doped fiber laser using a compound-cavity structure is proposed and demonstrated experimentally. The compound-cavity is composed of a main-linear-cavity and a subring-cavity. Using a pump power of 150 mW, the optical signal to noise ratio of the laser output is as high as ∼67 dB; the wavelength and output power fluctuation are 0.7 pm and 0.07 dBm respectively in an experimental period of 1 h; the linewidth of the laser output is as narrow as 650 Hz; the degree of polarization of the laser output is stable at a value of 100.8% in 15 min and the polarization extinction ratio is as high as 30.57 dB; the wavelength-tunable range is as wide as ∼8.1 nm. The proposed fiber laser can be used in areas where high stability, narrow-linewidth, single-polarization and wide wavelength-tunable range are needed. (letter)

Acquisition and visualization techniques for narrow spectral color imaging.

Science.gov (United States)

Neumann, László; García, Rafael; Basa, János; Hegedüs, Ramón

2013-06-01

This paper introduces a new approach in narrow-band imaging (NBI). Existing NBI techniques generate images by selecting discrete bands over the full visible spectrum or an even wider spectral range. In contrast, here we perform the sampling with filters covering a tight spectral window. This image acquisition method, named narrow spectral imaging, can be particularly useful when optical information is only available within a narrow spectral window, such as in the case of deep-water transmittance, which constitutes the principal motivation of this work. In this study we demonstrate the potential of the proposed photographic technique on nonunderwater scenes recorded under controlled conditions. To this end three multilayer narrow bandpass filters were employed, which transmit at 440, 456, and 470 nm bluish wavelengths, respectively. Since the differences among the images captured in such a narrow spectral window can be extremely small, both image acquisition and visualization require a novel approach. First, high-bit-depth images were acquired with multilayer narrow-band filters either placed in front of the illumination or mounted on the camera lens. Second, a color-mapping method is proposed, using which the input data can be transformed onto the entire display color gamut with a continuous and perceptually nearly uniform mapping, while ensuring optimally high information content for human perception.

Gas-filled cell as a narrow bandwidth bandpass filter in the VUV wavelength range

Energy Technology Data Exchange (ETDEWEB)

Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2011-04-15

We propose a method for spectrally filtering radiation in the VUV wavelength range by means of a monochromator constituted by a cell filled with a resonantly absorbing rare gas. Around particular wavelengths, the gas exhibits narrow-bandwidth absorbing resonances following the Fano profile. In particular, within the photon energy range 60 eV-65 eV, the correlation index of the Fano profiles for the photoionization spectra in Helium is equal to unity, meaning that the minimum of the cross-section is exactly zero. For sufficiently large column density in the gas cell, the spectrum of the incoming radiation will be attenuated by the background cross-section of many orders of magnitude, except for those wavelengths close to the point where the cross-section is zero. Remarkable advantages of a gas monochromator based on this principle are simplicity, efficiency and narrow-bandwidth. A gas monochromator installed in the experimental hall of a VUV SASE FEL facility would enable the delivery of a single-mode VUV laser beam. The design is identical to that of already existing gas attenuator systems for VUV or X-ray FELs. We present feasibility study and exemplifications for the FLASH facility in the VUV regime. (orig.)

A compact O-plus C-band switchable quad-wavelength fiber laser using arrayed waveguide grating

International Nuclear Information System (INIS)

Latif, A A; Zulkifli, M Z; Hassan, N A; Ahmad, H; Harun, S W; Ghani, Z A

2010-01-01

In this paper, a design of a quad-wavelength fiber laser (QWFL) operating in two different regions namely the O-band covering from 1302 nm to1317.4 nm and C-band from 1530.5 nm to 1548.0 nm is presented. Two different ASE sources from semiconductor optical amplifiers (SOAs) are used, one at 1310 nm and the other at1550 nm. By using a 1×24 channels arrayed waveguide grating (AWG) with 100 GHz interchannel spacing, the system is capable of generating 24 different wavelengths in more than 24 ways of quad-wavelength fiber laser with 0.6 nm and 0.8 nm of interval channel for O-band and C-band regions, respectively

Research on mechanism of the large-amplitude and narrow-band vibration of a flexible flat plate in the rectangular channel

Energy Technology Data Exchange (ETDEWEB)

Liu Lifang, E-mail: liu_lifang1106@yahoo.cn [School of Nuclear Science and Engineering, North China Electric Power University, Zhuxinzhuang, Dewai, Beijing 102206 (China); State Nuclear Power Software Development Center, Building 1, Compound No. 29, North Third Ring Road, Xicheng District, Beijing 100029 (China); Lu Daogang [School of Nuclear Science and Engineering, North China Electric Power University, Zhuxinzhuang, Dewai, Beijing 102206 (China)

2012-09-15

Highlights: Black-Right-Pointing-Pointer The large amplitude and narrow-band vibration experiment was performed. Black-Right-Pointing-Pointer The added mass theory was used to analyze the test plates' natural vibration characteristics in static water. Black-Right-Pointing-Pointer The occurring condition of the large amplitude and narrow band vibration was investigated. Black-Right-Pointing-Pointer The large amplitude and narrow-band vibration mechanism was investigated. - Abstract: Further experiments and theoretical analysis were performed to investigate mechanism of the large-amplitude and narrow-band vibration behavior of a flexible flat plate in a rectangular channel. Test plates with different thicknesses were adopted in the FIV experiments. The natural vibration characteristics of the flexible flat plates in air were tested, and the added mass theory of column was used to analyze the flexible flat plates' natural vibration characteristics in static water. It was found that the natural vibration frequency of a certain test plate in static water is approximately within the main vibration frequency band of the plate when it was induced to vibrate with the large-amplitude and narrow-band in the rectangular channel. It can be concluded that the harmonic between the flowing fluid and the vibrating plate is one of the key reasons to induce the large-amplitude and narrow-band vibration phenomenon. The occurring condition of the phenomenon and some important narrow-band vibration characteristics of a foursquare fix-supported flexible flat plate were investigated.

From Narrow to Wide Band Normalizer for LHC

CERN Document Server

Vismara, Giuseppe

1997-01-01

The narrow band normalizer (NBN) based on the phase processor is working to full satisfaction in the LEP BOM system for almost 10 years. Recently a new idea for a wide band normaliser (WBN) based on a time processor exploiting a single oscillation period has been developed. The position information is converted into a time difference between the zero crossing of two recombined and shaped electrode signals. It appears that the NBN can be easily adapted to perform as a wide band processor. To do so, the BP filter and the 90° Hybrid are replaced by low pass filter and delay lines. A prototype based on the present NBN has been developed and tested to prove the feasibility of the new idea. The paper gives an overview of the advantages and limitations of the BOM NB processor. It summarizes the useful LHC parameters and describes the specifications for the beam position acquisition system. After describing the basic principles, it analyzes in detail all the blocks of the processing chain and presents the measurem...

Wide applicability of high-Tc pairing originating from coexisting wide and incipient narrow bands in quasi-one-dimensional systems

Science.gov (United States)

Matsumoto, Karin; Ogura, Daisuke; Kuroki, Kazuhiko

2018-01-01

We study superconductivity in the Hubbard model on various quasi-one-dimensional lattices with coexisting wide and narrow bands originating from multiple sites within a unit cell, where each site corresponds to a single orbital. The systems studied are the two-leg and three-leg ladders, the diamond chain, and the crisscross ladder. These one-dimensional lattices are weakly coupled to form two-dimensional (quasi-one-dimensional) ones, and the fluctuation exchange approximation is adopted to study spin-fluctuation-mediated superconductivity. When one of the bands is perfectly flat and the Fermi level intersecting the wide band is placed in the vicinity of, but not within, the flat band, superconductivity arising from the interband scattering processes is found to be strongly enhanced owing to the combination of the light electron mass of the wide band and the strong pairing interaction due to the large density of states of the flat band. Even when the narrow band has finite bandwidth, the pairing mechanism still works since the edge of the narrow band, due to its large density of states, plays the role of the flat band. The results indicate the wide applicability of the high-Tc pairing mechanism due to coexisting wide and "incipient" narrow bands in quasi-one-dimensional systems.

A tunable and switchable single-longitudinal-mode dual-wavelength fiber laser with a simple linear cavity.

Science.gov (United States)

He, Xiaoying; Fang, Xia; Liao, Changrui; Wang, D N; Sun, Junqiang

2009-11-23

A simple linear cavity erbium-doped fiber laser based on a Fabry-Perot filter which consists of a pair of fiber Bragg gratings is proposed for tunable and switchable single-longitudinal-mode dual-wavelength operation. The single-longitudinal-mode is obtained by the saturable absorption of an unpumed erbium-doped fiber together with a narrow-band fiber Bragg grating. Under the high pump power (>166 mW) condition, the stable dual-wavelength oscillation with uniform amplitude can be realized by carefully adjusting the polarization controller in the cavity. Wavelength selection and switching are achieved by tuning the narrow-band fiber Bragg grating in the system. The spacing of the dual-wavelength can be selected at 0.20 nm (approximately 25.62 GHz), 0.22 nm (approximately 28.19 GHz) and 0.54 nm (approximately 69.19 GHz).

US images encoding envelope amplitude following narrow band filtering

International Nuclear Information System (INIS)

Sommer, F.G.; Stern, R.A.; Chen, H.S.

1986-01-01

Ultrasonic waveform data from phantoms having differing scattering characteristics and from normal and cirrhotic human liver in vivo were recorded within a standardized dynamic range and filtered with narrow band filters either above or below the mean recorded ultrasonic center frequency. Images created by mapping the amplitudes of received ultrasound following such filtration permitted dramatic differentiation, not discernible in conventional US images, of phantoms having differing scattering characteristics, and of normal and cirrhotic human livers

Active halo control through narrow-band excitation with the ADT at injection

CERN Document Server

Wagner, Joschka; Garcia Morales, Hector; Redaelli, Stefano; Valentino, Gianluca; Valuch, Daniel; CERN. Geneva. ATS Department

2016-01-01

During this MD (MD1388), the capabilities of an active halo control for beam tail depletion in the LHC were tested. The studied method relies on using the Transverse Damper (ADT) to perform a narrow-band excitation.

Ultra-narrow band diode lasers with arbitrary pulse shape modulation (Conference Presentation)

Science.gov (United States)

Ryasnyanskiy, Aleksandr I.; Smirnov, Vadim; Mokhun, Oleksiy; Glebov, Alexei L.; Glebov, Leon B.

2017-03-01

Wideband emission spectra of laser diode bars (several nanometers) can be largely narrowed by the usage of thick volume Bragg gratings (VBGs) recorded in photo-thermo-refractive glass. Such narrowband systems, with GHz-wide emission spectra, found broad applications for Diode Pumped Alkali vapor Lasers, optically pumped rare gas metastable lasers, Spin Exchange Optical Pumping, atom cooling, etc. Although the majority of current applications of narrow line diode lasers require CW operation, there are a variety of fields where operation in a different pulse mode regime is necessary. Commercial electric pulse generators can provide arbitrary current pulse profiles (sinusoidal, rectangular, triangular and their combinations). The pulse duration and repetition rate however, have an influence on the laser diode temperature, and therefore, the emitting wavelength. Thus, a detailed analysis is needed to understand the correspondence between the optical pulse profiles from a diode laser and the current pulse profiles; how the pulse profile and duty cycle affects the laser performance (e.g. the wavelength stability, signal to noise ratio, power stability etc.). We present the results of detailed studies of the narrowband laser diode performance operating in different temporal regimes with arbitrary pulse profiles. The developed narrowband (16 pm) tunable laser systems at 795 nm are capable of operating in different pulse regimes while keeping the linewidth, wavelength, and signal-to-noise ratio (>20 dB) similar to the corresponding CW modules.

Assessing the Temperature Dependence of Narrow-Band Raman Water Vapor Lidar Measurements: A Practical Approach

Science.gov (United States)

Whiteman, David N.; Venable, Demetrius D.; Walker, Monique; Cardirola, Martin; Sakai, Tetsu; Veselovskii, Igor

2013-01-01

Narrow-band detection of the Raman water vapor spectrum using the lidar technique introduces a concern over the temperature dependence of the Raman spectrum. Various groups have addressed this issue either by trying to minimize the temperature dependence to the point where it can be ignored or by correcting for whatever degree of temperature dependence exists. The traditional technique for performing either of these entails accurately measuring both the laser output wavelength and the water vapor spectral passband with combined uncertainty of approximately 0.01 nm. However, uncertainty in interference filter center wavelengths and laser output wavelengths can be this large or larger. These combined uncertainties translate into uncertainties in the magnitude of the temperature dependence of the Raman lidar water vapor measurement of 3% or more. We present here an alternate approach for accurately determining the temperature dependence of the Raman lidar water vapor measurement. This alternate approach entails acquiring sequential atmospheric profiles using the lidar while scanning the channel passband across portions of the Raman water vapor Q-branch. This scanning is accomplished either by tilt-tuning an interference filter or by scanning the output of a spectrometer. Through this process a peak in the transmitted intensity can be discerned in a manner that defines the spectral location of the channel passband with respect to the laser output wavelength to much higher accuracy than that achieved with standard laboratory techniques. Given the peak of the water vapor signal intensity curve, determined using the techniques described here, and an approximate knowledge of atmospheric temperature, the temperature dependence of a given Raman lidar profile can be determined with accuracy of 0.5% or better. A Mathematica notebook that demonstrates the calculations used here is available from the lead author.

Fluorene-based narrow-band-gap copolymers for red light- emitting diodes and bulk heterojunction photovoltaic cells

Institute of Scientific and Technical Information of China (English)

Mingliang SUN; Li WANG; Yangjun XIA; Bin DU; Ransheng LIU; Yong CAO

2008-01-01

A series of narrow band-gap conjugated copo-lymers (PFO-DDQ) derived from 9,9-dioctylfluorene (DOF) and 2,3-dimethyl-5,8-dithien-2-yl-quinoxalines (DDQ) is prepaid by the palladium-catalyzed Suzuki coupling reaction with the molar feed ratio of DDQ at around 1%,5%,15%,30% and 50%,respectively.The obtained polymers are readily soluble in common organic solvents.The solutions and the thin solid films of the copolymers absorb light from 300-590 nm with two absorbance.peaks at around 380 and 490 nm.The intens-ity of 490 nm peak increases with the increasing DDQ content in the polymers.Efficient energy transfer due to exciton trapping on narrow-band-gap DDQ sites has been observed.The PL emission consists exclusively of DDQ unit emission at around 591 643 nm depending on the DDQ content in solid film.The EL emission peaks are red-shifted from 580 nm for PFO-DDQ1 to 635 nm for PFO-DDQ50.The highest external quantum efficiency achieved with the device configuration ITO/PEDOT/ PVK/PFO-DDQt5/Ba/A1 is 1.33% with a luminous effi-ciency 1.54 cd/A.Bulk heterojunction photovoltaic cells fabricated from composite films of PFO-DDQ30 copoly-mer and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as electron donor and electron acceptor,respect-ively in device configuration:ITO/PEDOT:PSS/PFO-DDQ30:PCBM/PFPNBr/Al shows power conversion effi-ciencies of 1.18% with open-circuit voltage (Voc) of 0.90 V and short-circuit current density (Jsc) of 2.66 mA/cm2 under an AM1.5 solar simulator (100 mW/cm2).The photocurrent response wavelengths of the PVCs based on PFO-DDQ30/PCBM blends covers 300-700 nm.This indicates that these kinds of low band-gap polymers are promising candidates for polymeric solar cells and red light-emitting diodes.

Band-gap narrowing of TiO2 films induced by N-doping

International Nuclear Information System (INIS)

Nakano, Y.; Morikawa, T.; Ohwaki, T.; Taga, Y.

2006-01-01

N-doped TiO 2 films were deposited on n + -GaN/Al 2 O 3 substrates by reactive magnetron sputtering and subsequently crystallized by annealing at 550 o C in flowing N 2 gas. The N-doping concentration was ∼8.8%, as determined from X-ray photoelectron spectroscopy measurements. Deep-level optical spectroscopy measurements revealed two characteristic deep levels located at 1.18 and 2.48 eV below the conduction band. The 1.18 eV level is probably attributable to the O vacancy state and can be active as an efficient generation-recombination center. Additionally, the 2.48 eV band is newly introduced by the N-doping and contributes to band-gap narrowing by mixing with the O 2p valence band

Therapeutic efficacy of narrow band imaging-assisted transurethral electrocoagulation for ulcer-type interstitial cystitis/painful bladder syndrome.

Science.gov (United States)

Kajiwara, Mitsuru; Inoue, Shougo; Kobayashi, Kanao; Ohara, Shinya; Teishima, Jun; Matsubara, Akio

2014-04-01

Narrow band imaging cystoscopy can increase the visualization and detection of Hunner's lesions. A single-center, prospective clinical trial was carried out aiming to show the effectiveness of narrow band imaging-assisted transurethral electrocoagulation for ulcer-type interstitial cystitis/painful bladder syndrome. A total of 23 patients (19 women and 4 men) diagnosed as having ulcer-type interstitial cystitis/painful bladder syndrome were included. All typical Hunner's lesions and suspected areas identified by narrow band imaging were electrocoagulated endoscopically after the biopsy of those lesions. Therapeutic efficacy was assessed prospectively by using visual analog scale score of pain, O'Leary-Sant's symptom index, O'Leary-Sant's problem index and overactive bladder symptom score. The mean follow-up period was 22 months. All patients (100%) experienced a substantial improvement in pain. The average visual analog scale pain scores significantly decreased from 7.3 preoperatively to 1.2 1 month postoperatively. A total of 21 patients (91.3%) who reported improvement had at least a 50% reduction in bladder pain, and five reported complete resolution. Daytime frequency was significantly decreased postoperatively. O'Leary-Sant's symptom index, O'Leary-Sant's problem index and overactive bladder symptom score were significantly decreased postoperatively. However, during the follow-up period, a total of six patients had recurrence, and repeat narrow band imaging-assisted transurethral electrocoagulation of the recurrent lesions was carried out for five of the six patients, with good response in relieving bladder pain. Our results showed that narrow band imaging-assisted transurethral electrocoagulation could be a valuable therapeutic alternative in patients with ulcer-type interstitial cystitis/painful bladder syndrome, with good efficacy and reduction of recurrence rate. © 2014 The Japanese Urological Association.

Stability of the split-band solution and energy gap in the narrow-band region of the Hubbard model

International Nuclear Information System (INIS)

Arai, T.; Cohen, M.H.

1980-01-01

By inserting quasielectron energies ω calculated from the fully renormalized Green's function of the Hubbard model obtained in the preceding paper into the exact expression of Galitskii and Migdal, the ground-state energy, the chemical potential, and the dynamic- and thermodynamic-stability conditions are calculated in the narrow-band region. The results show that as long as the interaction energy I is finite, electrons in the narrow-band region do not obey the Landau theory of Fermi liquids, and a gap appears between the lowest quasielectron energy ω and the chemical potential μ for any occupation n, regardless of whether the lower band is exactly filled or not. This unusual behavior is possible because, when an electron is added to the system of N electrons, the whole system relaxes due to the strong interaction, introducing a relaxation energy difference between the two quantities. We also show that all previous solutions which exhibit the split-band structure, including Hubbard's work, yield the same conclusion that electrons do not behave like Landau quasiparticles. However, the energy gap is calculated to be negative at least for some occupations n, demonstrating the dynamic instability of those solutions. They also exhibit thermodynamic instability for certain occupations, while the fully renormalized solution, having sufficient electron correlations built in, satisfies the dynamic and thermodynamic stability conditions for all occupations. When the lower band is nearly filled, the nature of the solution is shown to change, making the coherent motion of electrons with fixed k values more difficult. In the pathological limit where I=infinity, however, the gap vanishes, yielding a metallic state

Double symbol error rates for differential detection of narrow-band FM

Science.gov (United States)

Simon, M. K.

1985-01-01

This paper evaluates the double symbol error rate (average probability of two consecutive symbol errors) in differentially detected narrow-band FM. Numerical results are presented for the special case of MSK with a Gaussian IF receive filter. It is shown that, not unlike similar results previously obtained for the single error probability of such systems, large inaccuracies in predicted performance can occur when intersymbol interference is ignored.

Determination of Seed Soundness in Conifers Cryptomeria japonica and Chamaecyparis obtusa Using Narrow-Multiband Spectral Imaging in the Short-Wavelength Infrared Range

Science.gov (United States)

Matsuda, Osamu; Hara, Masashi; Tobita, Hiroyuki; Yazaki, Kenichi; Nakagawa, Toshinori; Shimizu, Kuniyoshi; Uemura, Akira; Utsugi, Hajime

2015-01-01

Regeneration of planted forests of Cryptomeria japonica (sugi) and Chamaecyparis obtuse (hinoki) is the pressing importance to the forest administration in Japan. Low seed germination rate of these species, however, has hampered low-cost production of their seedlings for reforestation. The primary cause of the low germinability has been attributed to highly frequent formation of anatomically unsound seeds, which are indistinguishable from sound germinable seeds by visible observation and other common criteria such as size and weight. To establish a method for sound seed selection in these species, hyperspectral imaging technique was used to identify a wavelength range where reflectance spectra differ clearly between sound and unsound seeds. In sound seeds of both species, reflectance in a narrow waveband centered at 1,730 nm, corresponding to a lipid absorption band in the short-wavelength infrared (SWIR) range, was greatly depressed relative to that in adjacent wavebands on either side. Such depression was absent or less prominent in unsound seeds. Based on these observations, a reflectance index SQI, abbreviated for seed quality index, was formulated using reflectance at three narrow SWIR wavebands so that it represents the extent of the depression. SQI calculated from seed area-averaged reflectance spectra and spatial distribution patterns of pixelwise SQI within each seed area were both proven as reliable criteria for sound seed selection. Enrichment of sound seeds was accompanied by an increase in germination rate of the seed lot. Thus, the methods described are readily applicable toward low-cost seedling production in combination with single seed sowing technology. PMID:26083366

Widely tunable narrow-band coherent Terahertz radiation from an undulator at THU

Science.gov (United States)

Su, X.; Wang, D.; Tian, Q.; Liang, Y.; Niu, L.; Yan, L.; Du, Y.; Huang, W.; Tang, C.

2018-01-01

There is anxious demand for intense widely tunable narrow-band Terahertz (THz) radiation in scientific research, which is regarded as a powerful tool for the coherent control of matter. We report the generation of widely tunable THz radiation from a planar permanent magnet undulator at Tsinghua University (THU). A relativistic electron beam is compressed by a magnetic chicane into sub-ps bunch length to excite THz radiation in the undulator coherently. The THz frequency can be tuned from 0.4 THz to 10 THz continuously with narrow-band spectrums when the undulator gap ranges from 23 mm to 75 mm. The measured pulse THz radiation energy from 220 pC bunch is 3.5 μJ at 1 THz and tens of μJ pulse energy (corresponding peak power of 10 MW) can be obtained when excited by 1 nC beam extrapolated from the property of coherent radiation. The experimental results agree well with theoretical predictions, which demonstrates a suitable THz source for the many applications that require intense and widely tunable THz sources.

A Compact Narrow-Band Bandstop Filter Using Spiral-Shaped Defected Microstrip Structure

Directory of Open Access Journals (Sweden)

J. Wang

2014-04-01

Full Text Available A novel compact narrow-band bandstop filter is implemented by using the proposed spiral-shaped defected microstrip structure (SDMS in this paper. Compared with other DMSs, the presented SDMS exhibits the advantage of compact size and narrow stopband. Meanwhile, an approximate design rule of the SDMS is achieved and the effects of the dimensions on the resonant frequency and 3 dB fractional bandwidth (FBW are analyzed in detail. Both the simulation and measurement results of the fabricated bandstop filter show that it has a 10 dB stopband from 3.4 GHz to 3.6 GHz with more than 45 dB rejection at the center frequency.

Intensities, broadening and narrowing parameters in the ν3 band of methane

KAUST Repository

Es-sebbar, Et-touhami; Farooq, Aamir

2014-01-01

The P-branch of methane's ν3 band is probed to carry out an extensive study of the 2905-2908cm-1 infrared spectral region. Absolute line intensities as well as N2-, O2-, H2-, He-, Ar- and CO2-broadening coefficients are determined for nine transitions at room temperature. Narrowing parameters due to the Dicke effect have also been investigated. A narrow emission line-width (~0.0001cm-1) difference-frequency-generation (DFG) laser system is used as the tunable light source. To retrieve the CH4 spectroscopic parameters, Voigt and Galatry profiles were used to simulate the measured line shape of the individual transitions.

Intensities, broadening and narrowing parameters in the ν3 band of methane

KAUST Repository

Es-sebbar, Et-touhami

2014-12-01

The P-branch of methane\\'s ν3 band is probed to carry out an extensive study of the 2905-2908cm-1 infrared spectral region. Absolute line intensities as well as N2-, O2-, H2-, He-, Ar- and CO2-broadening coefficients are determined for nine transitions at room temperature. Narrowing parameters due to the Dicke effect have also been investigated. A narrow emission line-width (~0.0001cm-1) difference-frequency-generation (DFG) laser system is used as the tunable light source. To retrieve the CH4 spectroscopic parameters, Voigt and Galatry profiles were used to simulate the measured line shape of the individual transitions.

An Optimized, Grid Independent, Narrow Band Data Structure for High Resolution Level Sets

DEFF Research Database (Denmark)

Nielsen, Michael Bang; Museth, Ken

2004-01-01

enforced by the convex boundaries of an underlying cartesian computational grid. Here we present a novel very memory efficient narrow band data structure, dubbed the Sparse Grid, that enables the representation of grid independent high resolution level sets. The key features our new data structure are...

Enhancing Coverage in Narrow Band-IoT Using Machine Learning

OpenAIRE

Chafii , Marwa; Bader , Faouzi; Palicot , Jacques

2018-01-01

International audience; —Narrow Band-Internet of Thing (NB-IoT) is a recently proposed technology by 3GPP in Release-13. It provides low energy consumption and wide coverage in order to meet the requirements of its diverse applications that span social, industrial and environmental aspects. Increasing the number of repetitions of the transmission has been selected as a promising approach to enhance the coverage in NB-IoT up to 164 dB in terms of maximum coupling loss for uplink transmissions,...

Lateralization of narrow-band noise by blind and sighted listeners.

Science.gov (United States)

Simon, Helen J; Divenyi, Pierre L; Lotze, Al

2002-01-01

The effects of varying interaural time delay (ITD) and interaural intensity difference (IID) were measured in normal-hearing sighted and congenitally blind subjects as a function of eleven frequencies and at sound pressure levels of 70 and 90 dB, and at a sensation level of 25 dB (sensation level refers to the pressure level of the sound above its threshold for the individual subject). Using an 'acoustic' pointing paradigm, the subject varied the IID of a 500 Hz narrow-band (100 Hz) noise (the 'pointer') to coincide with the apparent lateral position of a 'target' ITD stimulus. ITDs of 0, +/-200, and +/-400 micros were obtained through total waveform delays of narrow-band noise, including envelope and fine structure. For both groups, the results of this experiment confirm the traditional view of binaural hearing for like stimuli: non-zero ITDs produce little perceived lateral displacement away from 0 IID at frequencies above 1250 Hz. To the extent that greater magnitude of lateralization for a given ITD, presentation level, and center frequency can be equated with superior localization abilities, blind listeners appear at least comparable and even somewhat better than sighted subjects, especially when attending to signals in the periphery. The present findings suggest that blind listeners are fully able to utilize the cues for spatial hearing, and that vision is not a mandatory prerequisite for the calibration of human spatial hearing.

The differences in brain activity between narrow band noise and pure tone tinnitus.

Directory of Open Access Journals (Sweden)

Sven Vanneste

Full Text Available BACKGROUND: Tinnitus is an auditory sensation characterized by the perception of sound or noise in the absence of any external sound source. Based on neurobiological research, it is generally accepted that most forms of tinnitus are attributable to maladaptive plasticity due to damage to auditory system. Changes have been observed in auditory structures such as the inferior colliculus, the thalamus and the auditory cortex as well as in non-auditory brain areas. However, the observed changes show great variability, hence lacking a conclusive picture. One of the reasons might be the selection of inhomogeneous groups in data analysis. METHODOLOGY: The aim of the present study was to delineate the differences between the neural networks involved in narrow band noise and pure tone tinnitus conducting LORETA based source analysis of resting state EEG. CONCLUSIONS: Results demonstrated that narrow band noise tinnitus patients differ from pure tone tinnitus patients in the lateral frontopolar (BA 10, PCC and the parahippocampal area for delta, beta and gamma frequency bands, respectively. The parahippocampal-PCC current density differences might be load dependent, as noise-like tinnitus constitutes multiple frequencies in contrast to pure tone tinnitus. The lateral frontopolar differences might be related to pitch specific memory retrieval.

Widely tunable single-/dual-wavelength fiber lasers with ultra-narrow linewidth and high OSNR using high quality passive subring cavity and novel tuning method.

Science.gov (United States)

Feng, Ting; Ding, Dongliang; Yan, Fengping; Zhao, Ziwei; Su, Hongxin; Yao, X Steve

2016-08-22

High stability single- and dual-wavelength compound cavity erbium-doped fiber lasers (EDFLs) with ultra-narrow linewidth, high optical signal to noise ratio (OSNR) and widely tunable range are demonstrated. Different from using traditional cascaded Type-1/Type-2 fiber rings as secondary cavities, we nest a Type-1 ring inside a Type-2 ring to form a passive subring cavity to achieve single-longitudinal-mode (SLM) lasing with ultra-narrow linewidth for the first time. We also show that the SLM lasing stability can be further improved by inserting a length of polarization maintaining fiber in the Type-2 ring. Using a uniform fiber Bragg grating (FBG) and two superimposed FBGs as mode restricting elements, respectively, we obtain a single-wavelength EDFL with a linewidth as narrow as 715 Hz and an OSNR as high as 73 dB, and a dual-wavelength EDFL with linewidths less than 1 kHz and OSNRs higher than 68 dB for both lasing wavelengths. Finally, by employing a novel self-designed strain adjustment device capable of applying both the compression and tension forces to the FBGs for wavelength tuning, we achieve the tuning range larger than 10 nm for both of the EDFLs.

Wavelength conversion from C- to L-band at 10 Gbit/s including transmission over 80 km of SSMF

DEFF Research Database (Denmark)

Poulsen, Henrik Nørskov; Buxens Azcoaga, Alvaro Juan; Clausen, Anders

2000-01-01

As the need for capacity increases, means to accommodate the growth is getting increasingly important. Hence, higher bit rates and an ever increasing number of WDM channels is being employed. This has led to the introduction of the L-band (ranging from 1570 to 1610 nm) as the new transmission...... window, opening up for-in conjunction with the C-band-an astonishing 80 nm of available bandwidth. However, as the number of wavelength channels increases, the need for wavelength conversion is becoming ever more pronounced. To perform the wavelength conversion, interferometric structures...... such as the monolithically integrated Mach-Zehnder interferometers (SOA-MZI) using semiconductor optical amplifiers as phase-shifting elements have proven excellent candidates. Here we present the conversion and transmission properties of a fully packaged device capable of wavelength conversion from C- to L-band having more...

Perturbation method for calculation of narrow-band impedance and trapped modes

International Nuclear Information System (INIS)

Heifets, S.A.

1987-01-01

An iterative method for calculation of the narrow-band impedance is described for a system with a small variation in boundary conditions, so that the variation can be considered as a perturbation. The results are compared with numeric calculations. The method is used to relate the origin of the trapped modes with the degeneracy of the spectrum of an unperturbed system. The method also can be applied to transverse impedance calculations. 6 refs., 6 figs., 1 tab

Two cases of eczematid-like purpura of Doucas and Kapetanakis responsive to narrow band ultraviolet B treatment.

Science.gov (United States)

Karadag, Ayse Serap; Bilgili, Serap Gunes; Onder, Sevda; Calka, Omer

2013-04-01

Eczematid-like purpura of Doucas and Kapetanakis is a type of pigmented purpuric dermatoses (PPDs) with eczematous changes in the purpuric surface. A 10-year-old male and a 44-year-old male patients were admitted to our clinics for itching and flaking of the skin rashes. Based on the clinical and histopathological evaluations, the rashes were identified as eczematid-like PPDs of Doucas and Kapetanakis. Both patients were treated with narrow band ultraviolet B. The lesions were remarkably regressed following the treatment. These cases reported due its rarity and good response to narrow band ultraviolet B. © 2013 John Wiley & Sons A/S.

On the joint distribution of excursion duration and amplitude of a narrow-band Gaussian process

DEFF Research Database (Denmark)

Ghane, Mahdi; Gao, Zhen; Blanke, Mogens

2018-01-01

of amplitude and period are limited to excursion through a mean-level or to describe the asymptotic behavior of high level excursions. This paper extends the knowledge by presenting a theoretical derivation of probability of wave exceedance amplitude and duration, for a narrow-band Gaussian process......The probability density of crest amplitude and of duration of exceeding a given level are used in many theoretical and practical problems in engineering. The joint density is essential for design of constructions that are subjected to waves and wind. The presently available joint distributions...... distribution, as expected, and that the marginal distribution of excursion duration works both for asymptotic and non-asymptotic cases. The suggested model is found to be a good replacement for the empirical distributions that are widely used. Results from simulations of narrow-band Gaussian processes, real...

Characterization of Low Noise TES Detectors Fabricated by D-RIE Process for SAFARI Short-Wavelength Band

Science.gov (United States)

Khosropanah, P.; Suzuki, T.; Hijmering, R. A.; Ridder, M. L.; Lindeman, M. A.; Gao, J.-R.; Hoevers, H.

2014-08-01

SRON is developing TES detectors based on a superconducting Ti/Au bilayer on a suspended SiN membrane for the short-wavelength band of the SAFARI instrument on SPICA mission. We have recently replaced the wet KOH etching of the Si substrate by deep reactive ion etching. The new process enables us to fabricate the detectors on the substrate and release the membrane at the very last step. Therefore the production of SAFARI large arrays (4343) on thin SiN membrane (250 nm) is feasible. It also makes it possible to realize narrow supporting SiN legs of 1 m, which are needed to meet SAFARI NEP requirements. Here we report the current-voltage characteristics, noise performance and impedance measurement of these devices. The measured results are then compared with the distributed leg model that takes into account the thermal fluctuation noise due to the SiN legs. We measured a dark NEP of 0.7 aW/, which is 1.6 times higher than the theoretically expected phonon noise.

Narrow band interference cancelation in OFDM: Astructured maximum likelihood approach

KAUST Repository

Sohail, Muhammad Sadiq

2012-06-01

This paper presents a maximum likelihood (ML) approach to mitigate the effect of narrow band interference (NBI) in a zero padded orthogonal frequency division multiplexing (ZP-OFDM) system. The NBI is assumed to be time variant and asynchronous with the frequency grid of the ZP-OFDM system. The proposed structure based technique uses the fact that the NBI signal is sparse as compared to the ZP-OFDM signal in the frequency domain. The structure is also useful in reducing the computational complexity of the proposed method. The paper also presents a data aided approach for improved NBI estimation. The suitability of the proposed method is demonstrated through simulations. © 2012 IEEE.

Reconfigurable Radio Access Unit for DWDM to W-Band Wireless Conversion

DEFF Research Database (Denmark)

Chorchos, Łukasz; Rommel, Simon; Turkiewicz, Jarosław P.

2017-01-01

In this letter a reconfigurable Remote Access Unit (RAU) is proposed and demonstrated, interfacing dense wavelength division multiplexed (DWDM) optical and W-band wireless links. The RAU is composed of a tunable local oscillator, a narrow optical filter and a control unit, making it reconfigurable...

Narrowing of band gap at source/drain contact scheme of nanoscale InAs-nMOS

Science.gov (United States)

Mohamed, A. H.; Oxland, R.; Aldegunde, M.; Hepplestone, S. P.; Sushko, P. V.; Kalna, K.

2018-04-01

A multi-scale simulation study of Ni/InAs nano-scale contact aimed for the sub-14 nm technology is carried out to understand material and transport properties at a metal-semiconductor interface. The deposited Ni metal contact on an 11 nm thick InAs channel forms an 8.5 nm thick InAs leaving a 2.5 nm thick InAs channel on a p-type doped (1 × 1016 cm-3) AlAs0.47Sb0.53 buffer. The density functional theory (DFT) calculations reveal a band gap narrowing in the InAs at the metal-semiconductor interface. The one-dimensional (1D) self-consistent Poisson-Schrödinger transport simulations using real-space material parameters extracted from the DFT calculations at the metal-semiconductor interface, exhibiting band gap narrowing, give a specific sheet resistance of Rsh = 90.9 Ω/sq which is in a good agreement with an experimental value of 97 Ω/sq.

Control of fibre laser mode-locking by narrow-band Bragg gratings

International Nuclear Information System (INIS)

Laegsgaard, J

2008-01-01

The use of narrow-band high-reflectivity fibre Bragg gratings (FBGs) as end mirrors in a fibre laser cavity with passive mode-locking provided by a semiconductor saturable absorber mirror (SESAM) is investigated numerically. The FBG is found to control the energy range of stable mode-locking, which may be shifted far outside the regime of SESAM saturation by a suitable choice of FBG and cavity length. The pulse shape is controlled by the combined effects of FBG dispersion and self-phase modulation in the fibres, and a few ps pulses can be obtained with standard uniform FBGs

Narrow Wavelength, Frequency Modulated Source at 1.5 Wavelength, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — Ultrastable, narrow linewidth, tunable, high reliability sources at 1.5 or 2mm are needed for high performance LIDARs for several NASA applications, including wind...

Implementation of Industrial Narrow Band Communication System into SDR Concept

Directory of Open Access Journals (Sweden)

A. Prokes

2008-12-01

Full Text Available The rapid expansion of the digital signal processing has penetrated recently into a sphere of high performance industrial narrow band communication systems which had been for long years dominated by the traditional analog circuit design. Although it brings new potential to even increase the efficiency of the radio channel usage it also forces new challenges and compromises radio designers have to face. In this article we describe the design of the IF sampling industrial narrowband radio receiver, optimize a digital receiver structure implemented in a single FPGA circuit and study the performance of such radio receiver architecture. As an evaluation criterion the communication efficiency in form of maximum usable receiver sensitivity, co-channel rejection, adjacent channel selectivity and radio blocking measurement have been selected.

Laser-based ultrasonics by dual-probe interferometer detection and narrow-band ultrasound generation

Science.gov (United States)

Huang, Jin

1993-01-01

Despite the advantages of laser-based ultrasonic (LBU) systems, the overall sensitivity of LBU systems needs to be improved for practical applications. Progress is reported to achieve better LBU detection accuracy and sensitivity for applications with surface waves and Lamb waves. A novel dual-probe laser interferometer has been developed to measure the same signal at two points. The dual-probe interferometer is a modification of a conventional single-probe interferometer in that the reference beam is guided to a second detecting point on the specimen surface to form a differential measurement mode, which measure the difference of the displacements at the two points. This dual-probe interferometer is particularly useful for accurate measurements of the speed and attenuation of surface waves and Lamb waves. The dual-probe interferometer has been applied to obtain accurate measurements of the surface wave speed and attenuation on surfaces of increasing surface roughness. It has also been demonstrated that with an appropriate signal processing method, namely, the power cepstrum method, the dual-probe interferometer is applicable to measure the local surface wave speed even when the probe separation is so small that the two waveforms in the interferometer output signal overlap in the time domain. Narrow-band signal generation and detection improve the sensitivity of LBU systems. It is proposed to use a diffraction grating to form an array of illuminating strips which form a source of narrowband surface and Lamb waves. The line-array of thermoelastic sources generates narrow-band signals whose frequency and bandwidth can be easily controlled. The optimum line-array parameters, such as width, spacing and the number of lines in the array have been derived theoretically and verified experimentally. Narrow-band signal generation with optimum parameters has been demonstrated. The enhanced LBU system with dual-probe detection and narrowband signal generation has been

Multi-wavelength fiber laser in the S-band region using a Sagnac loop mirror as a comb generator in an SOA gain medium

International Nuclear Information System (INIS)

Zulkifli, M Z; Hassan, N A; Awang, N A; Ahmad, H; Ghani, Z A; Harun, S W

2010-01-01

A simple design of multi-wavelength generation in the S-band region of the optical network transmission is proposed. The design consists of broad-band fiber Bragg grating (BB-FBG), which acts as a filter to enhance operation in the S-band region. A Sagnac loop mirror (SLM) is used to generate multiple wavelength oscillations in the ring cavity. The output consists of 60 lasing wavelengths oscillating simultaneously between 1464 nm and 1521 nm with a spacing of 0.92 nm and an output linewidth of 0.66 nm

Light polarization management via reflection from arrays of sub-wavelength metallic twisted bands

Science.gov (United States)

Nawrot, M.; Haberko, J.; Zinkiewicz, Ł.; Wasylczyk, P.

2017-12-01

With constant progress of nano- and microfabrication technologies, photolithography in particular, a number of sub-wavelength metallic structures have been demonstrated that can be used to manipulate light polarization. Numerical simulations of light propagation hint that helical twisted bands can have interesting polarization properties. We use three-dimensional two-photon photolithography (direct laser writing) to fabricate a few-micrometer-thick arrays of twisted bands and coat them uniformly with metal. We demonstrate that circular polarization can be generated from linear polarization upon reflection from such structures over a broad range of frequencies in the mid infrared.

Fabrication of Ceramic Layer-by-Layer Infrared Wavelength Photonic Band Gap Crystals

Energy Technology Data Exchange (ETDEWEB)

Kang, Henry Hao-Chuan [Iowa State Univ., Ames, IA (United States)

2004-12-19

Photonic band gap (PBG) crystals, also known as photonic crystals, are periodic dielectric structures which form a photonic band gap that prohibit the propagation of electromagnetic (EM) waves of certain frequencies at any incident angles. Photonic crystals have several potential applications including zero-threshold semiconductor lasers, the inhibition of spontaneous emission, dielectric mirrors, and wavelength filters. If defect states are introduced in the crystals, light can be guided from one location to another or even a sharp bending of light in micron scale can be achieved. This generates the potential for optical waveguide and optical circuits, which will contribute to the improvement in the fiber-optic communications and the development of high-speed computers.

First-principles study of direct and narrow band gap semiconducting β-CuGaO2

International Nuclear Information System (INIS)

Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

2015-01-01

Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO 2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the β-CuGaO 2 phase. Our calculations show that the β-CuGaO 2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the Γ point of Brillouin zone. The optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment. (paper)

A test of ν stability using a 200 GeV narrow-band neutrino beam at BEBC

Science.gov (United States)

Deden, H.; Grässler, H.; Kirch, D.; Schultze, K.; Böckmann, K.; Glimpf, W.; Kokott, T. P.; Nellen, B.; Saarikko, H.; Wünsch, B.; Bosetti, P. C.; Cundy, D. C.; Grant, A. L.; Hulth, P. O.; Pape, L.; Peyrou, Ch.; Skjeggestad, O.; Wachsmuth, H.; Mermikides, M.; Vayaki, A.; Barnham, K. W. J.; Butterworth, I.; Chima, J. S.; Clayton, E. F.; Miller, D. B.; Mobayyen, M.; Petrides, A.; Powell, K. J.; Albajar, C.; Lloyd, J. L.; Myatt, G.; Perkins, D. H.; Poppe, M.; Radojicic, D.; Renton, P.; Saitta, B.; Wells, J.; Bloch, M.; Bolognese, T.; Tallini, B.; Velasco, J.; Vignaud, D.; Aachen-Bonn-CERN-Demokritos Athens-I. C. London-Oxford-Saclay Collaboration

1981-01-01

νe induced events obtained in a 200 GeV narrow-band beam have been studied and compared to the number expected from K e3+ decay. Agreement is found between the expected and observed numbers allowing limits to be set on νe → νx mixing.

Generation of tunable narrow-band surface-emitted terahertz radiation in periodically poled lithium niobate.

Science.gov (United States)

Weiss, C; Torosyan, G; Avetisyan, Y; Beigang, R

2001-04-15

Generation of tunable narrow-band terahertz (THz) radiation perpendicular to the surface of periodically poled lithium niobate by optical rectification of femtosecond pulses is reported. The generated THz radiation can be tuned by use of different poling periods and different observation angles, limited only by the available bandwidth of the pump pulse. Typical bandwidths were 50-100 GHz, depending on the collection angle and the number of periods involved.

Wavelength-Dependent Differential Interference Contrast Microscopy: Selectively Imaging Nanoparticle Probes in Live Cells

Energy Technology Data Exchange (ETDEWEB)

Sun, Wei; Wang, Gufeng; Fang, Ning; and Yeung, Edward S.

2009-11-15

Gold and silver nanoparticles display extraordinarily large apparent refractive indices near their plasmon resonance (PR) wavelengths. These nanoparticles show good contrast in a narrow spectral band but are poorly resolved at other wavelengths in differential interference contrast (DIC) microscopy. The wavelength dependence of DIC contrast of gold/silver nanoparticles is interpreted in terms of Mie's theory and DIC working principles. We further exploit this wavelength dependence by modifying a DIC microscope to enable simultaneous imaging at two wavelengths. We demonstrate that gold/silver nanoparticles immobilized on the same glass slides through hybridization can be differentiated and imaged separately. High-contrast, video-rate images of living cells can be recorded both with and without illuminating the gold nanoparticle probes, providing definitive probe identification. Dual-wavelength DIC microscopy thus presents a new approach to the simultaneous detection of multiple probes of interest for high-speed live-cell imaging.

Photonic band gap properties of one-dimensional Thue-Morse all-dielectric photonic quasicrystal

Science.gov (United States)

Yue, Chenxi; Tan, Wei; Liu, Jianjun

2018-05-01

In this paper, the photonic band gap (PBG) properties of one-dimensional (1D) Thue-Morse photonic quasicrystal (PQC) S4 structure are theoretically investigated by using transfer matrix method in Bragg condition. The effects of the center wavelength, relative permittivity and incident angle on PBG properties are elaborately analyzed. Numerical results reveal that, in the case of normal incidence, the symmetry and periodicity properties of the photonic band structure are presented. As the center wavelength increases, the PBG center frequency and PBG width decrease while the photonic band structure is always symmetrical about the central frequency and the photonic band structure repeats periodically in the expanding observation frequency range. With the decrease of relative permittivity contrast, the PBG width and the relative PBG width gradually decreases until PBG disappears while the symmetry of the photonic band structure always exists. In the case of oblique incidence, as the incident angle increases, multiple narrow PBGs gradually merge into a wide PBG for the TE mode while for the TM mode, the number of PBG continuously decreases and eventually disappears, i.e., multiple narrow PBGs become a wide passband for the TM mode. The research results will provide a reference for the choice of the material, the incident angle for the PBG properties and its applications of 1D Thue-Morse PQC.

H-tailored surface conductivity in narrow band gap In(AsN)

Energy Technology Data Exchange (ETDEWEB)

Velichko, A. V., E-mail: amalia.patane@nottingham.ac.uk, E-mail: anton.velychko@nottingham.ac.uk; Patanè, A., E-mail: amalia.patane@nottingham.ac.uk, E-mail: anton.velychko@nottingham.ac.uk; Makarovsky, O. [School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD (United Kingdom); Capizzi, M.; Polimeni, A. [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale A. Moro 2, 00185 Roma (Italy); Sandall, I. C.; Tan, C. H. [Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Giubertoni, D. [Center for Materials and Microsystems—Fondazione Bruno Kessler, via Sommarive 18, 38123 Povo, Trento (Italy); Krier, A.; Zhuang, Q. [Physics Department, Lancaster University, Lancaster LA1 4YB (United Kingdom)

2015-01-12

We show that the n-type conductivity of the narrow band gap In(AsN) alloy can be increased within a thin (∼100 nm) channel below the surface by the controlled incorporation of H-atoms. This channel has a large electron sheet density of ∼10{sup 18 }m{sup −2} and a high electron mobility (μ > 0.1 m{sup 2}V{sup −1}s{sup −1} at low and room temperature). For a fixed dose of impinging H-atoms, its width decreases with the increase in concentration of N-atoms that act as H-traps thus forming N-H donor complexes near the surface.

The effects of narrow-band middle infrared radiation in enhancing the antitumor activity of paclitaxel.

Science.gov (United States)

Tsai, Shang-Ru; Sheu, Bor-Ching; Huang, Pei-Shen; Lee, Si-Chen

2016-01-01

Paclitaxel is used as an adjuvant to enhance the effectiveness of ionization radiation therapy; however, high-energy radiation often damages the healthy cells surrounding cancer cells. Low-energy, middle-infrared radiation (MIR) has been shown to prevent tissue damage, and recent studies have begun combining MIR with paclitaxel. However, the cytotoxic effects of this treatment combination remain unclear, and the mechanism underlying its effects on HeLa cells has yet to be elucidated. This study investigated the effectiveness of treating HeLa human cervical cancer cells with a combination of paclitaxel for 48 h in conjunction with narrow-band MIR from 3.0 to 5.0 μm. This combined treatment significantly inhibited the growth of HeLa cells. Specifically, results from Annexin V-FITC/PI apoptosis detection and cell mitochondrial membrane potential analyses revealed an increase in apoptotic cell death and a collapse of mitochondrial membrane potential. One possible mechanism underlying cellular apoptosis is an increase in oxidative stress. These preliminary findings provide evidence to support the combination of narrow-band MIR with paclitaxel as an alternative approach in the treatment of human cervical cancer.

How narrow-band and broad-band uvb irradiation influences the immunohistochemistry analyses of experimental animals’ skin – a comparative study. Part II

Directory of Open Access Journals (Sweden)

Katarzyna Borowska

2017-09-01

Full Text Available This is the second part of the artcle series impact narrow-band UVB radiation (NB-UVB and broad-band UVB radiation (BB-UVB on experimental animals’ skin (white Wistar female rats. The aim of this comparative study was immunohistochemistry analyses containing expression of p53 protein. Expression of p53 protein was performed on two experimental groups. One – exposed to NB-UVB; the other – exposed to BB-UVB radiation. The results indicate that p53 protein takes an active part in the process of apoptosis that is induced by both NB-UVB and BB-UVB. The results showed an increase in p53 expressing cells following BB-UVB than NB-UVB phototherapy.

High-resolution endoscopy plus chromoendoscopy or narrow-band imaging in Barrett's esophagus: a prospective randomized crossover study

NARCIS (Netherlands)

Kara, M. A.; Peters, F. P.; Rosmolen, W. D.; Krishnadath, K. K.; ten Kate, F. J.; Fockens, P.; Bergman, J. J. G. H.

2005-01-01

Background and study aims: High-resolution endoscopy (HRE) may improve the detection of early neoplasia in Barrett's esophagus. Indigo carmine chromoendoscopy (ICc) and narrow-band imaging (NBI) may be useful techniques to complement HRE. The aim of this study was to compare HRE-ICC with HrE-NBI for

A multicenter validation of an endoscopic classification with narrow band imaging for gastric precancerous and cancerous lesions

NARCIS (Netherlands)

Pimentel-Nunes, P.; Dinis-Ribeiro, M.; Soares, J. B.; Marcos-Pinto, R.; Santos, C.; Rolanda, C.; Bastos, R. P.; Areia, M.; Afonso, L.; Bergman, J.; Sharma, P.; Gotoda, T.; Henrique, R.; Moreira-Dias, L.

2012-01-01

Background and study aim: The reliability and external validity of narrow band imaging (NBI) in the stomach have not been described consistently. The aim of the current study was to describe and estimate the accuracy and reliability of a simplified classification system for NBI in the diagnosis of

Low Noise Quantum Frequency Conversion from Rb Wavelengths to Telecom O-band

Science.gov (United States)

Li, Xiao; Solmeyer, Neal; Stack, Daniel; Quraishi, Qudsia

2015-05-01

Ideal quantum repeaters would be composed of long-lived quantum memories entangled with flying qubits. They are becoming essential elements to achieve quantum communication over long distances in a quantum network. However, quantum memories based on neutral atoms operate at wavelengths in the near infrared, unsuitable for long distance communication. The ability to coherently convert photons entangled with quantum memories into telecom wavelengths reduces the transmission loss in optical fibers and therefore dramatically improves the range of a quantum repeater. Furthermore, quantum frequency conversion (QFC) can enable entanglement and communication between different types of quantum memories, thus creating a versatile hybrid quantum network. A recent experiment has shown the conversion of heralded photons from Rb-based memories to the telecom C-band. We implement a setup using a nonlinear PPLN waveguide for the QFC into a wavelength region where the noise-floor would be limited by dark counts rather than pump photons. Our approach uses a pump laser at a much longer wavelength. It has the advantage that the strong pump itself and the broad background in the PPLN can be nearly completely filtered from the converted signal. Such low background level allows for the conversion to be done on the heralding photon, which enables the generated entanglement to be used in a scalable way to multiple nodes remotely situated and to subsequent protocols.

High thermal stability solution-processable narrow-band gap molecular semiconductors.

Science.gov (United States)

Liu, Xiaofeng; Hsu, Ben B Y; Sun, Yanming; Mai, Cheng-Kang; Heeger, Alan J; Bazan, Guillermo C

2014-11-19

A series of narrow-band gap conjugated molecules with specific fluorine substitution patterns has been synthesized in order to study the effect of fluorination on bulk thermal stability. As the number of fluorine substituents on the backbone increase, one finds more thermally robust bulk structures both under inert and ambient conditions as well as an increase in phase transition temperatures in the solid state. When integrated into field-effect transistor devices, the molecule with the highest degree of fluorination shows a hole mobility of 0.15 cm(2)/V·s and a device thermal stability of >300 °C. Generally, the enhancement in thermal robustness of bulk organization and device performance correlates with the level of C-H for C-F substitution. These findings are relevant for the design of molecular semiconductors that can be introduced into optoelectronic devices to be operated under a wide range of conditions.

Increased polyp detection using narrow band imaging compared with high resolution endoscopy in patients with hyperplastic polyposis syndrome

NARCIS (Netherlands)

Boparai, K. S.; van den Broek, F. J. C.; van Eeden, S.; Fockens, P.; Dekker, E.

2011-01-01

Hyperplastic polyposis syndrome (HPS) is associated with colorectal cancer and is characterized by multiple hyperplastic polyps, sessile serrated adenomas (SSAs) and adenomas. Narrow band imaging (NBI) may improve the detection of polyps in HPS. We aimed to compare polyp miss rates with NBI with

Five years of Project META - An all-sky narrow-band radio search for extraterrestrial signals

Science.gov (United States)

Horowitz, Paul; Sagan, Carl

1993-01-01

We have conducted a five-year search of the northern sky (delta between 30 and 60 deg) for narrow-band radio signals near the 1420 MHz line of neutral hydrogen, and its second harmonic, using an 8.4 x 10 exp 6 channel Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earth's rotation, which provides a characteristic changing Doppler signature for narrow-band signals of extraterrestrial origin. Among the 6 x 10 exp 13 spectral channels searched, we have found 37 candidate events exceeding the average detection threshold of 1.7 x 10 exp -23 W/sq m, none of which was detected upon reobservation. The strongest of these appear to be dominated by rare processor errors. However, the strongest signals that survive culling for terrestrial interference lie in or near the Galactic plane. We describe the search and candidate events, and set limits on the prevalence of supercivilizations transmitting Doppler-precompensated beacons at H I or its second harmonic. We conclude with recommendations for future searches, based upon these findings, and a description of our next-generation search system.

Vibration-tolerant narrow-linewidth semiconductor disk laser using novel frequency-stabilisation schemes

Science.gov (United States)

Hunter, Craig R.; Jones, Brynmor E.; Schlosser, Peter; Sørensen, Simon Toft; Strain, Michael J.; McKnight, Loyd J.

2018-02-01

This paper will present developments in narrow-linewidth semiconductor-disk-laser systems using novel frequencystabilisation schemes for reduced sensitivity to mechanical vibrations, a critical requirement for mobile applications. Narrow-linewidth single-frequency lasers are required for a range of applications including metrology and highresolution spectroscopy. Stabilisation of the laser was achieved using a monolithic fibre-optic ring resonator with free spectral range of 181 MHz and finesse of 52 to act as passive reference cavity for the laser. Such a cavity can operate over a broad wavelength range and is immune to a wide band of vibrational frequency noise due to its monolithic implementation. The frequency noise of the locked system has been measured and compared to typical Fabry-Perotlocked lasers using vibration equipment to simulate harsh environments, and analysed here. Locked linewidths of portable, narrow-linewidth laser system for harsh environments that can be flexibly designed for a range of applications.

Synchrotron Studies of Narrow Band and Low-Dimensional Materials. Final Report for July 1, 1990 --- December 31, 2002

International Nuclear Information System (INIS)

Allen, J. W.

2003-01-01

This report summarizes a 12-year program of various kinds of synchrotron spectroscopies directed at the electronic structures of narrow band and low-dimensional materials that display correlated electron behaviors such as metal-insulator transitions, mixed valence, superconductivity, Kondo moment quenching, heavy Fermions, and non-Fermi liquid properties

Identification and application of the valid wavelength bands for burnt area detection and fire severity classification using Landsat/TM data

International Nuclear Information System (INIS)

Maki, M.; Tamura, M.

2003-01-01

Firstly, by using Landsat Thematic Mapper (TM) imagery before and after forest fire, the valid wavelength bands for detecting burnt areas were examined and compared to NDVI. Secondly, by using the valid wavelength bands, mapping of burnt area and classification of fire severity were examined. The results show that (a) channel 4 and 7 were more sensitive than other channels for detecting burnt area, (b) BAI (Burnt Area Index) [(ch. 4-ch. 7)/(ch. 4+ch. 7)] was more useful than NDVI for detecting burnt areas, and (c) BAI imagery was more useful for classification of burn severity than NDVI imagery

Thermal Loss Becomes an Issue for Tunable Narrow-band Antennas in Fourth Generation Handsets

DEFF Research Database (Denmark)

Barrio, Samantha Caporal Del; Morris, Art; Pedersen, Gert Frølund

2015-01-01

Antenna tuning is a very promising technique to cope with the expansion of the mobile communication frequency spectrum. Tunable antennas can address a wide range of operating frequencies, while being highly integrated. In particular, high-Q antennas (also named narrow-band antennas) are very...... compact, thus are good candidates to be embedded on fourth generation handsets. This study focuses on ‘high-Q’ tunable antennas and contributes with a characterisation of their loss mechanism, which is a major parameter in link-budget calculations. This study shows, through an example, that the tuner loss...

Enhanced dissociation of charge-transfer states in narrow band gap polymer:fullerene solar cells processed with 1,8-octanedithiol

NARCIS (Netherlands)

Moet, D.J.D.; Lenes, M.; Morana, M.; Azimi, H.; Brabec, C.J.; Blom, P.W.M.

2010-01-01

The improved photovoltaic performance of narrow band gap polymer:fullerene solar cells processed from solutions containing small amounts of 1,8-octanedithiol is analyzed by modeling of the experimental photocurrent. In contrast to devices that are spin coated from pristine chlorobenzene, these cells

Enhanced dissociation of charge-transfer states in narrow band gap polymer : fullerene solar cells processed with 1,8-octanedithiol

NARCIS (Netherlands)

Moet, D. J. D.; Lenes, M.; Morana, M.; Azimi, H.; Brabec, C. J.; Blom, P. W. M.

2010-01-01

The improved photovoltaic performance of narrow band gap polymer:fullerene solar cells processed from solutions containing small amounts of 1,8-octanedithiol is analyzed by modeling of the experimental photocurrent. In contrast to devices that are spin coated from pristine chlorobenzene, these cells

Recovering physical properties from narrow-band photometry

Science.gov (United States)

Schoenell, W.; Cid Fernandes, R.; Benítez, N.; Vale Asari, N.

2013-05-01

Our aim in this work is to answer, using simulated narrow-band photometry data, the following general question: What can we learn about galaxies from these new generation cosmological surveys? For instance, can we estimate stellar age and metallicity distributions? Can we separate star-forming galaxies from AGN? Can we measure emission lines, nebular abundances and extinction? With what precision? To accomplish this, we selected a sample of about 300k galaxies with good S/N from the SDSS and divided them in two groups: 200k objects and a template library of 100k. We corrected the spectra to z = 0 and converted them to filter fluxes. Using a statistical approach, we calculated a Probability Distribution Function (PDF) for each property of each object and the library. Since we have the properties of all the data from the STARLIGHT-SDSS database, we could compare them with the results obtained from summaries of the PDF (mean, median, etc). Our results shows that we retrieve the weighted average of the log of the galaxy age with a good error margin (σ ≈ 0.1 - 0.2 dex), and similarly for the physical properties such as mass-to-light ratio, mean stellar metallicity, etc. Furthermore, our main result is that we can derive emission line intensities and ratios with similar precision. This makes this method unique in comparison to the other methods on the market to analyze photometry data and shows that, from the point of view of galaxy studies, future photometric surveys will be much more useful than anticipated.

Optical frequency-domain reflectometry using multiple wavelength-swept elements of a DFB laser array

Science.gov (United States)

DiLazaro, Tom; Nehmetallah, Georges

2017-02-01

Coherent optical frequency-domain reflectometry (C-OFDR) is a distance measurement technique with significant sensitivity and detector bandwidth advantages over normal time-of-flight methods. Although several swept-wavelength laser sources exist, many exhibit short coherence lengths, or require precision mechanical tuning components. Semiconductor distributed feedback lasers (DFBs) are advantageous as a mid-to-long range OFDR source because they exhibit a narrow linewidth and can be rapidly tuned simply via injection current. However, the sweep range of an individual DFB is thermally limited. Here, we present a novel high-resolution OFDR system that uses a compact, monolithic 12-element DFB array to create a continuous, gap-free sweep over a wide wavelength range. Wavelength registration is provided by the incorporation of a HCN gas cell and reference interferometer. The wavelength-swept spectra of the 12 DFBs are combined in post-processing to achieve a continuous total wavelength sweep of more than 40 nm (5.4 THz) in the telecommunications C-Band range.

Choice of Eye-Safe Radiation Wavelength in UV and Near IR Spectral Bands for Remote Sensing

OpenAIRE

M. L. Belov; V. A. Gorodnichev; D. A. Kravtsov; A. A. Cherpakova

2016-01-01

The introduction of laser remote sensing systems carries a particular risk to the human’s sense of vision. A structure of the eye, and especially the retina, is the main critical organ as related to the laser radiation.The work uses the optical models of the atmosphere, correctly working in both the UV and the near-IR band, to select the eye-safe radiation wavelengths in the UV (0.355 m) and near-IR (~ 1.54 and ~ 2 m) spectral bands from the point of view of recorded lidar signal value to ful...

A 1.1-1.9 GHz SETI SURVEY OF THE KEPLER FIELD. I. A SEARCH FOR NARROW-BAND EMISSION FROM SELECT TARGETS

Energy Technology Data Exchange (ETDEWEB)

Siemion, Andrew P. V.; Korpela, Eric; Werthimer, Dan; Cobb, Jeff; Lebofsky, Matt; Marcy, Geoffrey W. [University of California, Berkeley, 110 Sproul Hall, Berkeley, CA 94720 (United States); Demorest, Paul; Maddalena, Ron J.; Langston, Glen [National Radio Astronomy Observatory, 520 Edgemont Rd Charlottesville, VA 22903 (United States); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, 640 North A' ohoku Place, 209 Hilo, HI 96720-2700 (United States); Tarter, Jill [SETI Institute, 189 Bernardo Ave 100 Mountain View, CA 94043 (United States)

2013-04-10

We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T{sub eq} > 230 K, stars with five or more detected candidates or stars with a super-Earth (R{sub p} < 3 R{sub Circled-Plus }) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than {approx}1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of {approx}1.5 Multiplication-Sign 10{sup 21} erg s{sup -1}, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be <10{sup -6} M{sub Sun }{sup -1}. Here we describe our observations, data reduction procedures and results.

Narrow-band 1, 2, 3, 4, 8, 16 and 24 cycles/360o angular frequency filters

Directory of Open Access Journals (Sweden)

Simas M.L.B.

2002-01-01

Full Text Available We measured human frequency response functions for seven angular frequency filters whose test frequencies were centered at 1, 2, 3, 4, 8, 16 or 24 cycles/360º using a supra-threshold summation method. The seven functions of 17 experimental conditions each were measured nine times for five observers. For the arbitrarily selected filter phases, the maximum summation effect occurred at test frequency for filters at 1, 2, 3, 4 and 8 cycles/360º. For both 16 and 24 cycles/360º test frequencies, maximum summation occurred at the lower harmonics. These results allow us to conclude that there are narrow-band angular frequency filters operating somehow in the human visual system either through summation or inhibition of specific frequency ranges. Furthermore, as a general result, it appears that addition of higher angular frequencies to lower ones disturbs low angular frequency perception (i.e., 1, 2, 3 and 4 cycles/360º, whereas addition of lower harmonics to higher ones seems to improve detection of high angular frequency harmonics (i.e., 8, 16 and 24 cycles/360º. Finally, we discuss the possible involvement of coupled radial and angular frequency filters in face perception using an example where narrow-band low angular frequency filters could have a major role.

Enhanced UV light detection using a p-terphenyl wavelength shifter

Science.gov (United States)

Joosten, S.; Kaczanowicz, E.; Ungaro, M.; Rehfuss, M.; Johnston, K.; Meziani, Z.-E.

2017-10-01

UV-glass photomultiplier tubes (PMTs) have poor photon detection efficiency for wavelengths below 300 nm due to the opaqueness of the window material. Costly quartz PMTs could be used to enhance the efficiency below 300 nm. A less expensive solution that dramatically improves this efficiency is the application of a thin film of a p-terphenyl (PT) wavelength shifter on UV-glass PMTs. This improvement was quantified for Photonis XP4500B PMTs for wavelengths between 200 nm and 400 nm. The gain factor ranges up to 5 . 4 ± 0 . 5 at a wavelength of 215 nm, with a material load of 110 ± 10 μg /cm2 (894 nm). The wavelength shifter was found to be fully transparent for wavelengths greater than 300 nm. The resulting gain in detection efficiency, when used in a typical C̆erenkov counter, was estimated to be of the order of 40%. Consistent coating quality was assured by a rapid gain testing procedure using narrow-band UV LEDs. Based on these results, 200 Photonis XP4500B PMTs were treated with PT for the upgraded low-threshold C̆erenkov counter (LTCC) to be used in the CEBAF Large Acceptance Spectrometer upgraded detector (CLAS12) at the Thomas Jefferson National Accelerator Facility.

Full-sky survey searching for ultra-narrow-band artificial CW signals: analysis of the results of Project META

Science.gov (United States)

Lemarchand, Guillermo A.

1996-06-01

Project META (Megachannel ExtraTerrestrial Assay), a full-sky survey for artificial narrow-band signals, has been conducted from the Harvard/Smithsonian 26 m radiotelescope at Agassiz Station and from one of the two 30 m radiotelescopes of the Instituto Argentino de Radioastronomia (IAR). The search was performed near the 1420 MHz line of neutral hydrogen, and its second harmonic, using two 8.4 X 10(superscript 6) channel Fourier spectrometers of 0.05 Hz resolution and 400 kHz of instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earth's rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 6 X 10(superscript 13) spectral channels searched in the northern hemisphere, Horowitz and Sagan reported 37 candidates events exceeding the average threshold of 1.7 X 10(superscript -23) W m(superscript -2), while in the southern hemisphere among 2 X 10(superscript 13) spectral channels analyzed we found 19 events exceeding the same threshold. The strongest signals that survive culling for terrestrial interference lie in or near the Galactic Plane. The first high resolution southern target search around 71 stars (-90 degrees intelligence. It is showed that these narrow-band non-repeating 'events' found by Project META can be generated by (a) radiometer noise fluctuations, (b) a population of constant galactic sources which undergo deep fading and amplification due to interstellar scintillation, consistent with ETI transmissions and (c) real, transient signals of either terrestrial or extraterrestrial origin. The Bayesian test shows that hypothesis (b) and (c) are both highly preferred to (a), but the first two are about equally likely. Using this analysis we discuss the best observing strategies to determine the real origin of these 'events'.

A narrow-band k-distribution model with single mixture gas assumption for radiative flows

Science.gov (United States)

Jo, Sung Min; Kim, Jae Won; Kwon, Oh Joon

2018-06-01

In the present study, the narrow-band k-distribution (NBK) model parameters for mixtures of H2O, CO2, and CO are proposed by utilizing the line-by-line (LBL) calculations with a single mixture gas assumption. For the application of the NBK model to radiative flows, a radiative transfer equation (RTE) solver based on a finite-volume method on unstructured meshes was developed. The NBK model and the RTE solver were verified by solving two benchmark problems including the spectral radiance distribution emitted from one-dimensional slabs and the radiative heat transfer in a truncated conical enclosure. It was shown that the results are accurate and physically reliable by comparing with available data. To examine the applicability of the methods to realistic multi-dimensional problems in non-isothermal and non-homogeneous conditions, radiation in an axisymmetric combustion chamber was analyzed, and then the infrared signature emitted from an aircraft exhaust plume was predicted. For modeling the plume flow involving radiative cooling, a flow-radiation coupled procedure was devised in a loosely coupled manner by adopting a Navier-Stokes flow solver based on unstructured meshes. It was shown that the predicted radiative cooling for the combustion chamber is physically more accurate than other predictions, and is as accurate as that by the LBL calculations. It was found that the infrared signature of aircraft exhaust plume can also be obtained accurately, equivalent to the LBL calculations, by using the present narrow-band approach with a much improved numerical efficiency.

Interface band gap narrowing behind open circuit voltage losses in Cu2ZnSnS4 solar cells

DEFF Research Database (Denmark)

Crovetto, Andrea; Palsgaard, Mattias Lau Nøhr; Gunst, Tue

2017-01-01

We present evidence that bandgap narrowing at the heterointerface may be a major cause of the large open circuit voltage deficit of Cu2ZnSnS4/CdS solar cells. Bandgap narrowing is caused by surface states that extend the Cu2ZnSnS4valence band into the forbidden gap. Those surface states...... are consistently found in Cu2ZnSnS4, but not in Cu2ZnSnSe4, by first-principles calculations. They do not simply arise from defects at surfaces but are an intrinsic feature of Cu2ZnSnS4 surfaces. By including those states in a device model, the outcome of previously published temperature-dependent open circuit...... voltage measurements on Cu2ZnSnS4 solar cells can be reproduced quantitatively without necessarily assuming a cliff-like conduction band offset with the CdS buffer layer. Our first-principles calculations indicate that Zn-based alternative buffer layers are advantageous due to the ability of...

Intercomparison of unmanned aerial vehicle and ground-based narrow band spectrometers applied to crop trait monitoring in organic potato production

NARCIS (Netherlands)

Domingues Franceschini, Marston; Bartholomeus, Harm; Apeldoorn, van Dirk; Suomalainen, Juha; Kooistra, Lammert

2017-01-01

Vegetation properties can be estimated using optical sensors, acquiring data on board of different platforms. For instance, ground-based and Unmanned Aerial Vehicle (UAV)-borne spectrometers can measure reflectance in narrow spectral bands, while different modelling approaches, like regressions

All-mechanical quantum noise cancellation for accelerometry: broadband with momentum measurements, narrow band without

International Nuclear Information System (INIS)

Jacobs, Kurt; Balu, Radhakrishnan; Tezak, Nikolas; Mabuchi, Hideo

2016-01-01

We show that the ability to make direct measurements of momentum, in addition to the usual direct measurements of position, allows a simple configuration of two identical mechanical oscillators to be used for broadband back-action-free force metrology. This would eliminate the need for an optical reference oscillator in the scheme of Tsang and Caves (2010 Phys. Rev. Lett.  105 123601), along with its associated disadvantages. We also show that if one is restricted to position measurements alone then two copies of the same two-oscillator configuration can be used for narrow-band back-action-free force metrology. (paper)

Phototherapy UVB narrow band treatment of psoriasis, mycosis fungoides and vitiligo

International Nuclear Information System (INIS)

Reyes, M.V.; Kutnizky, R.; Bosch, M.P.; Ruiz Lascano, A.

2013-01-01

Introduction: Numerous studies have shown the beneficial effect of ultraviolet radiation for the treatment of lymphoproliferative or inflammatory skin diseases. Objective: To determine the response to UVB narrow band (UVB-nb) in psoriasis, mycosis fungoides stage IA, IB and vitiligo, in the Dermatology Department of Hospital Privado from May 2009 to January 2011. To correlate total energy dose used and the total number of sessions with the response achieved in each disease. To describe adverse reactions; determine demographic characteristics of the population and comorbidities in psoriasis and vitiligo. Material and Methods: We performed a prospective, descriptive, analytical, observational study. We included all patients assessed for initiation of UVB-nb. Regarding the patients who did not start or interrupted the treatment a survey was conducted to assess the causes. We calculated the cumulative dose and number of sessions at the end of treatment. (authors) [es

[Nursing care management in dermatological patient on phototherapy narrow band UVB].

Science.gov (United States)

de Argila Fernández-Durán, Nuria; Blasco Maldonado, Celeste; Martín Gómez, Mónica

2013-01-01

Phototherapy with narrow band ultraviolet B is a treatment used in some dermatology units, and is the first choice in some dermatological diseases due to being comfortable and cheap. The aim of this paper is to describe the management and nursing care by grouping more specific diagnoses, following NANDA-NIC/NOC taxonomy, such as the methodology from application, technique, material, and personnel to space-related aspects, with the aim of avoiding the clinical variability and the possible associated risks for the patients, and for the nurses who administer the treatment. The continuity of the same nurse in the follow-up sessions stimulates the relationship between medical personnel and patients, key points for loyalty and therapeutic adherence. This paper examines a consensus procedure with the Dermatology Unit Team and accredited by the Hospital Quality Unit. Copyright © 2013 Elsevier España, S.L. All rights reserved.

Charge separation dynamics in a narrow band gap polymer-PbS nanocrystal blend for efficient hybrid solar cells

NARCIS (Netherlands)

Piliego, Claudia; Manca, Marianna; Kroon, Renee; Yarema, Maksym; Szendrei, Krisztina; Andersson, Mats R.; Heiss, Wolfgang; Loi, Maria A.

2012-01-01

We have demonstrated efficient hybrid solar cells based on lead sulfide (PbS) nanocrystals and a narrow band gap polymer, poly[{2,5-bis(2-hexyldecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl}-alt-{[2,2'-(1,4-phenylene)bis-thiophene]-5,5'-diyl}], (PDPPTPT). An opportune mixing of

W-band radio-over-fiber propagation of two optically encoded wavelength channels

Science.gov (United States)

Eghbal, Morad Khosravi; Shadaram, Mehdi

2018-01-01

We propose a W-band wavelength-division multiplexing (WDM)-over-optical code-division multiple access radio-over-fiber system. This system offers capacity expansion by increasing the working frequency to millimeter wave region and by introducing optical encoding and multiwavelength multiplexing. The system's functionality is investigated by software modeling, and the results are presented. The generated signals are data modulated at 10 Gb/s and optically encoded for two wavelength channels and transmitted with a 20-km length of fiber. The received signals are optically decoded and detected. Also, encoding has improved the bit error rate (BER) versus the received optical power margin for the WDM setting by about 4 dB. In addition, the eye-diagram shows that the difference between received optical power levels at the BER of 10-12 to 10-3 is about 1.3% between two encoded channels. This method of capacity improvement is significantly important for the next generation of mobile communication, where millimeter wave signals will be widely used to deliver data to small cells.

Narrow-band tunable terahertz emission from ferrimagnetic Mn{sub 3-x}Ga thin films

Energy Technology Data Exchange (ETDEWEB)

Awari, N. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany); University of Groningen, 9747 AG Groningen (Netherlands); Kovalev, S., E-mail: s.kovalev@hzdr.de, E-mail: c.fowley@hzdr.de, E-mail: rodek@tcd.ie; Fowley, C., E-mail: s.kovalev@hzdr.de, E-mail: c.fowley@hzdr.de, E-mail: rodek@tcd.ie; Green, B.; Yildirim, O.; Lindner, J.; Fassbender, J.; Deac, A. M.; Gensch, M. [Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden (Germany); Rode, K., E-mail: s.kovalev@hzdr.de, E-mail: c.fowley@hzdr.de, E-mail: rodek@tcd.ie; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Coey, J. M. D. [CRANN, AMBER and School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Gallardo, R. A. [Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, 2390123 Valparíso (Chile)

2016-07-18

Narrow-band terahertz emission from coherently excited spin precession in metallic ferrimagnetic Mn{sub 3-x}Ga Heusler alloy nanofilms has been observed. The efficiency of the emission, per nanometer film thickness, is comparable or higher than that of classical laser-driven terahertz sources based on optical rectification. The center frequency of the emission from the films can be tuned precisely via the film composition in the range of 0.20–0.35 THz, making this type of metallic film a candidate for efficient on-chip terahertz emitters. Terahertz emission spectroscopy is furthermore shown to be a sensitive probe of magnetic properties of ultra-thin films.

Generation of narrow-band polarization-entangled photon pairs at a rubidium D1 line

International Nuclear Information System (INIS)

Tian Long; Li Shujing; Yuan Haoxiang; Wang Hai

2016-01-01

Using the process of cavity-enhanced spontaneous parametric down-conversion (SPDC), we generate a narrow-band polarization-entangled photon pair resonant on the rubidium (Rb) D1 line (795 nm). The degenerate single-mode photon pair is selected by multiple temperature controlled etalons. The linewidth of generated polarization-entangled photon pairs is 15 MHz which matches the typical atomic memory bandwidth. The measured Bell parameter for the polarization-entangled photons S = 2.73 ± 0.04 which violates the Bell-CHSH inequality by ∼18 standard deviations. The presented entangled photon pair source could be utilized in quantum communication and quantum computing based on quantum memories in atomic ensemble. (author)

Room Temperature Direct Band Gap Emission from Ge p-i-n Heterojunction Photodiodes

Directory of Open Access Journals (Sweden)

E. Kasper

2012-01-01

Full Text Available Room temperature direct band gap emission is observed for Si-substrate-based Ge p-i-n heterojunction photodiode structures operated under forward bias. Comparisons of electroluminescence with photoluminescence spectra allow separating emission from intrinsic Ge (0.8 eV and highly doped Ge (0.73 eV. Electroluminescence stems from carrier injection into the intrinsic layer, whereas photoluminescence originates from the highly n-doped top layer because the exciting visible laser wavelength is strongly absorbed in Ge. High doping levels led to an apparent band gap narrowing from carrier-impurity interaction. The emission shifts to higher wavelengths with increasing current level which is explained by device heating. The heterostructure layer sequence and the light emitting device are similar to earlier presented photodetectors. This is an important aspect for monolithic integration of silicon microelectronics and silicon photonics.

Subharmonic response of a single-degree-of-freedom nonlinear vibro-impact system to a narrow-band random excitation.

Science.gov (United States)

Haiwu, Rong; Wang, Xiangdong; Xu, Wei; Fang, Tong

2009-08-01

The subharmonic response of single-degree-of-freedom nonlinear vibro-impact oscillator with a one-sided barrier to narrow-band random excitation is investigated. The narrow-band random excitation used here is a filtered Gaussian white noise. The analysis is based on a special Zhuravlev transformation, which reduces the system to one without impacts, or velocity jumps, thereby permitting the applications of asymptotic averaging over the "fast" variables. The averaged stochastic equations are solved exactly by the method of moments for the mean-square response amplitude for the case of linear system with zero offset. A perturbation-based moment closure scheme is proposed and the formula of the mean-square amplitude is obtained approximately for the case of linear system with nonzero offset. The perturbation-based moment closure scheme is used once again to obtain the algebra equation of the mean-square amplitude of the response for the case of nonlinear system. The effects of damping, detuning, nonlinear intensity, bandwidth, and magnitudes of random excitations are analyzed. The theoretical analyses are verified by numerical results. Theoretical analyses and numerical simulations show that the peak amplitudes may be strongly reduced at large detunings or large nonlinear intensity.

Stresses and Temperature Stability of Dense Wavelength Division Multiplexing Filters Prepared by Reactive Ion-Assisted E-Gun Evaporation

Science.gov (United States)

Wei, Chao-Tsang; Shieh, Han-Ping D.

2005-10-01

In this paper, we report the in situ measurement of the temperature stability of narrow-band-pass filters on different types of substrate, for dense wavelength division multiplexing (DWDM) filters in optical-fiber transmission systems. The DWDM filters were designed as all-dielectric Fabry-Perot filters and fabricated by reactive ion-assisted deposition. Ta2O5 and SiO2 were used as high- and low-refractive-index layers, respectively, for constructing the DWDM filters. The accuracy and stability of the coating process were evaluated for fabricating the DWDM filters for the temperature stability of the center wavelength. The center wavelength shift was determined to be greatly dependent on the coefficient of thermal expansion of the substrate on which the filter is deposited.

W-Band Real-Time Transmission Utilizing a Reconfigurable RAU for NG-PON Networks

DEFF Research Database (Denmark)

Chorchos, Łukasz; Turkiewicz, Jarosław P.; Rommel, Simon

2016-01-01

In this article, we propose and test a reconfigurable Remote Access Unit (RAU) to interface optical and W-band wireless communication links (75–110 GHz), utilizing optical heterodyne signal upconversion. The RAU is composed of a tunable local oscillator, narrow optical filter and a control unit....... The RAU can be software-reconfigured to select a specific dense wavelength division multiplexed (DWDM) channel. Real-time tests with 100 GHz spaced DWDM signals have been performed. Real-time 2.5 Gbit/s error free radio transmission in the 75 GHz to 95 GHz range of the W-band was achieved after 15 km...

The role of high-resolution endoscopy and narrow-band imaging in the evaluation of upper GI neoplasia in familial adenomatous polyposis

NARCIS (Netherlands)

Lopez-Ceron, Maria; van den Broek, Frank J. C.; Mathus-Vliegen, Elisabeth M.; Boparai, Karam S.; van Eeden, Susanne; Fockens, Paul; Dekker, Evelien

2013-01-01

The Spigelman classification stratifies cancer risk in familial adenomatous polyposis (FAP) patients with duodenal adenomatosis. High-resolution endoscopy (HRE) and narrow-band imaging (NBI) may identify lesions at high risk. To compare HRE and NBI for the detection of duodenal and gastric polyps

Observations of the Galaxy NGC 3077 in the Narrow-Band [S II] and Hα Filters

Directory of Open Access Journals (Sweden)

Andjelić M.

2011-09-01

Full Text Available We present observations of the H I tidal arm near a dwarf galaxy NGC 3077 (member of the M81 galaxy group in the narrow-band [S II] and Hα filters. Observations were carried out in 2011 March with the 2 m RCC telescope at the NAO Rozhen, Bulgaria. Our search for possible supernova remnant candidates (identified as sources with enhanced [S II] emission relative to their Hα emission in this region yielded no sources of this kind. Nevertheless, we found a number of objects with significant Hα emission that probably represent uncatalogued, low brightness H II regions.

Laser-produced lithium plasma as a narrow-band extended ultraviolet radiation source for photoelectron spectroscopy.

Science.gov (United States)

Schriever, G; Mager, S; Naweed, A; Engel, A; Bergmann, K; Lebert, R

1998-03-01

Extended ultraviolet (EUV) emission characteristics of a laser-produced lithium plasma are determined with regard to the requirements of x-ray photoelectron spectroscopy. The main features of interest are spectral distribution, photon flux, bandwidth, source size, and emission duration. Laser-produced lithium plasmas are characterized as emitters of intense narrow-band EUV radiation. It can be estimated that the lithium Lyman-alpha line emission in combination with an ellipsoidal silicon/molybdenum multilayer mirror is a suitable EUV source for an x-ray photoelectron spectroscopy microscope with a 50-meV energy resolution and a 10-mum lateral resolution.

Extreme ultraviolet narrow band emission from electron cyclotron resonance plasmas

International Nuclear Information System (INIS)

Zhao, H. Y.; Zhao, H. W.; Sun, L. T.; Zhang, X. Z.; Wang, H.; Ma, B. H.; Li, X. X.; Zhu, Y. H.; Sheng, L. S.; Zhang, G. B.; Tian, Y. C.

2008-01-01

Extreme ultraviolet lithography (EUVL) is considered as the most promising solution at and below dynamic random access memory 32 nm half pitch among the next generation lithography, and EUV light sources with high output power and sufficient lifetime are crucial for the realization of EUVL. However, there is no EUV light source completely meeting the requirements for the commercial application in lithography yet. Therefore, ECR plasma is proposed as a novel concept EUV light source. In order to investigate the feasibility of ECR plasma as a EUV light source, the narrow band EUV power around 13.5 nm emitted by two highly charged ECR ion sources--LECR2M and SECRAL--was measured with a calibrated EUV power measurement tool. Since the emission lines around 13.5 nm can be attributed to the 4d-5p transitions of Xe XI or the 4d-4f unresolved transition array of Sn VIII-XIII, xenon plasma was investigated. The dependence of the EUV throughput and the corresponding conversion efficiency on the parameters of the ion source, such as the rf power and the magnetic confinement configurations, were preliminarily studied

Stable C-band fiber laser with switchable multi-wavelength output using coupled microfiber Mach-Zehnder interferometer

Science.gov (United States)

Ahmad, H.; Jasim, A. A.

2017-07-01

A compact coupled microfiber Mach-Zehnder interferometer (CM-MZI) is proposed and experimentally demonstrated for C-band region multi-wavelength tuning and switching in a fiber laser. The CM-MZI is fabricated using a 9 μm single tapered silica optical microfiber fabricated by flame-drawing technique and exploits multi-mode interference to produce spatial mode beating and suppress mode competition of the homogeneous gain medium. The output wavelength spacing is immune to changes in the external environment, but can be changed from 1.5 nm to 1.4 nm by slightly modifying the path-length difference of the CM-MZI. The proposed laser is capable of generating single, dual, triple, quintuple, and sextuple stabilize wavelengths outputs over a range of more than 32 nm using polarization rotation (PR) and macro-bending. The lasers having a 3 dB line-width of less than ∼30 pm and peak-to-floor of about 55 dB at a pump power of 38 mW.

HMB-45 Study Before and After Narrow-Band (311 nm Ultraviolet B Treatment in Vitiligo

Directory of Open Access Journals (Sweden)

Moosavi

2015-06-01

Full Text Available Background Vitiligo is an acquired disease in which the loss of functional melanocytes results in depigmented macules and patches. Over the years, wide arrays of markers for melanocytes have been described, including human melanoma black 45 (HMB-45. Narrow-band ultraviolet B (NB-UVB therapy is one of the therapeutic modalities for vitiligo. Objectives We sought to detect HMB-45 staining after 30 sessions of NB-UVB therapy in vitiligo and perivitiliginous skin. Patients and Methods All the participants were planned to have 30 sessions of NB-UVB therapy with 724 lamps (FS, 72 T, 12-HO Daavlin MED at 311 nm wavelengths. The patients underwent skin sampling from lesional and perilesional area before and after 30 sessions of treatment. The skin biopsies were sent to the laboratory for light microscopy and immunohistochemical study. The evaluation of HMB-45 was based on the quantitative method, measuring the number of positive stained cells. Clinical response was defined as repigmentation in three categories: more than 75%; between 40% and 75%; and less than 40%. The data were analyzed using SPSS (version 17. Results Twenty-nine patients completed the study. The Wilcoxon test showed a meaningful relation between HMB-45 staining before and after NB-UVB treatment in perilesional skin. We did not find a meaningful relation between HMB-45 staining before and after treatment regarding the mean age, gender, mean duration of disease, and initial lesional area (P = 0.55, P = 0.41, P = 0.55, and P = 0.87, respectively. After 30 sessions of NB-UVB therapy, repigmentation was less than 40% in 8 (27.6%, 40 - 75% in 7 (24.1%, and more than 75% in 6 patients. Conclusions The HMB-45 stain strength significantly changed after treatment in perilesional skin.

Multi-tap complex-coefficient incoherent microwave photonic filters based on optical single-sideband modulation and narrow band optical filtering.

Science.gov (United States)

Sagues, Mikel; García Olcina, Raimundo; Loayssa, Alayn; Sales, Salvador; Capmany, José

2008-01-07

We propose a novel scheme to implement tunable multi-tap complex coefficient filters based on optical single sideband modulation and narrow band optical filtering. A four tap filter is experimentally demonstrated to highlight the enhanced tuning performance provided by complex coefficients. Optical processing is performed by the use of a cascade of four phase-shifted fiber Bragg gratings specifically fabricated for this purpose.

Effect of band gap narrowing on GaAs tunnel diode I-V characteristics

Energy Technology Data Exchange (ETDEWEB)

Lebib, A.; Hannanchi, R. [Laboratoire d' énergie et de matériaux, LabEM-LR11ES34-Université de sousse (Tunisia); Beji, L., E-mail: lotbej_fr@yahoo.fr [Laboratoire d' énergie et de matériaux, LabEM-LR11ES34-Université de sousse (Tunisia); EL Jani, B. [Unité de Recherche sur les Hétéro-Epitaxies et Applications, Faculté des Sciences, Université de Monastir, 5019 Monastir (Tunisia)

2016-12-01

We report on experimental and theoretical study of current-voltage characteristics of C/Si-doped GaAs tunnel diode. For the investigation of the experimental data, we take into account the band-gap narrowing (BGN) effect due to heavily-doped sides of the tunnel diode. The BGN of the n- and p-sides of tunnel diode was measured by photoluminescence spectroscopy. The comparison between theoretical results and experimental data reveals that BGN effect enhances tunneling currents and hence should be considered to identify more accurately the different transport mechanisms in the junction. For C/Si-doped GaAs tunnel diode, we found that direct tunneling is the dominant transport mechanism at low voltages. At higher voltages, this mechanism is replaced by the rate-controlling tunneling via gap states in the forbidden gap.

ACCURATE LABORATORY WAVELENGTHS OF THE e 3 Σ-(ν' = 5) - X 1 Σ+(ν'' = 0) BAND OF 12C16O

International Nuclear Information System (INIS)

Dickenson, G. D.; Nortje, A. C.; Steenkamp, C. M.; Rohwer, E. G.; Du Plessis, A.

2010-01-01

The forbidden singlet-triplet transitions of carbon monoxide (CO) are important in the interpretation of vacuum ultraviolet interstellar absorption spectra and in particular for the measurement of large CO column densities. Twenty rovibronic lines of the e 3 Σ - (ν' = 5) - X 1 Σ + (ν'' = 0) band of 12 C 16 O for which laboratory wavelengths were previously unavailable were identified in laser-induced fluorescence excitation spectra. Wavelengths were assigned to five rovibronic transitions to an average accuracy of 0.0028 A. A further 15 lines could not be fully resolved and average wavelengths were measured for these groups of closely spaced lines. A wavelength difference of 0.011 ± 0.0028 A between the measured wavelengths and the calculated wavelengths in the atlas of Eidelsberg and Rostas demonstrates the need for more experimental data on CO.

Accurate Laboratory Wavelengths of the e 3 Σ-(ν' = 5) - X 1 Σ+(ν'' = 0) Band of 12C16O

Science.gov (United States)

Dickenson, G. D.; Nortje, A. C.; Steenkamp, C. M.; Rohwer, E. G.; Du Plessis, A.

2010-05-01

The forbidden singlet-triplet transitions of carbon monoxide (CO) are important in the interpretation of vacuum ultraviolet interstellar absorption spectra and in particular for the measurement of large CO column densities. Twenty rovibronic lines of the e 3Σ-(ν' = 5) - X 1Σ+(ν'' = 0) band of 12 C 16O for which laboratory wavelengths were previously unavailable were identified in laser-induced fluorescence excitation spectra. Wavelengths were assigned to five rovibronic transitions to an average accuracy of 0.0028 Å. A further 15 lines could not be fully resolved and average wavelengths were measured for these groups of closely spaced lines. A wavelength difference of 0.011 ± 0.0028 Å between the measured wavelengths and the calculated wavelengths in the atlas of Eidelsberg & Rostas demonstrates the need for more experimental data on CO.

Time-stretch microscopy based on time-wavelength sequence reconstruction from wideband incoherent source

International Nuclear Information System (INIS)

Zhang, Chi; Xu, Yiqing; Wei, Xiaoming; Tsia, Kevin K.; Wong, Kenneth K. Y.

2014-01-01

Time-stretch microscopy has emerged as an ultrafast optical imaging concept offering the unprecedented combination of the imaging speed and sensitivity. However, dedicated wideband and coherence optical pulse source with high shot-to-shot stability has been mandated for time-wavelength mapping—the enabling process for ultrahigh speed wavelength-encoded image retrieval. From the practical point of view, exploiting methods to relax the stringent requirements (e.g., temporal stability and coherence) for the source of time-stretch microscopy is thus of great value. In this paper, we demonstrated time-stretch microscopy by reconstructing the time-wavelength mapping sequence from a wideband incoherent source. Utilizing the time-lens focusing mechanism mediated by a narrow-band pulse source, this approach allows generation of a wideband incoherent source, with the spectral efficiency enhanced by a factor of 18. As a proof-of-principle demonstration, time-stretch imaging with the scan rate as high as MHz and diffraction-limited resolution is achieved based on the wideband incoherent source. We note that the concept of time-wavelength sequence reconstruction from wideband incoherent source can also be generalized to any high-speed optical real-time measurements, where wavelength is acted as the information carrier

Use of narrow-band imaging bronchoscopy in detection of lung cancer.

Science.gov (United States)

Zaric, Bojan; Perin, Branislav

2010-05-01

Narrow-band imaging (NBI) is a new endoscopic technique designed for detection of pathologically altered submucosal and mucosal microvascular patterns. The combination of magnification videobronchoscopy and NBI showed great potential in the detection of precancerous and cancerous lesions of the bronchial mucosa. The preliminary studies confirmed supremacy of NBI over white-light videobronchoscopy in the detection of premalignant and malignant lesions. Pathological patterns of capillaries in bronchial mucosa are known as Shibuya's descriptors (dotted, tortuous and abrupt-ending blood vessels). Where respiratory endoscopy is concerned, the NBI is still a 'technology in search of proper indication'. More randomized trials are necessary to confirm the place of NBI in the diagnostic algorithm, and more trials are needed to evaluate the relation of NBI to autofluorescence videobronchoscopy and to white-light magnification videobronchoscopy. Considering the fact that NBI examination of the tracheo-bronchial tree is easy, reproducible and clear to interpret, it is certain that NBI videobronchoscopy will play a significant role in the future of lung cancer detection and staging.

Development and Validation of a Classification System to Identify High-Grade Dysplasia and Esophageal Adenocarcinoma in Barrett's Esophagus Using Narrow-Band Imaging

NARCIS (Netherlands)

Sharma, Prateek; Bergman, Jacques J. G. H. M.; Goda, Kenichi; Kato, Mototsugu; Messmann, Helmut; Alsop, Benjamin R.; Gupta, Neil; Vennalaganti, Prashanth; Hall, Matt; Konda, Vani; Koons, Ann; Penner, Olga; Goldblum, John R.; Waxman, Irving

2016-01-01

Although several classification systems have been proposed for characterization of Barrett's esophagus (BE) surface patterns based on narrow-band imaging (NBI), none have been widely accepted. The Barrett's International NBI Group (BING) aimed to develop and validate an NBI classification system for

Plant lighting system with five wavelength-band light-emitting diodes providing photon flux density and mixing ratio control

Directory of Open Access Journals (Sweden)

Yano Akira

2012-11-01

Full Text Available Abstract Background Plant growth and development depend on the availability of light. Lighting systems therefore play crucial roles in plant studies. Recent advancements of light-emitting diode (LED technologies provide abundant opportunities to study various plant light responses. The LED merits include solidity, longevity, small element volume, radiant flux controllability, and monochromaticity. To apply these merits in plant light response studies, a lighting system must provide precisely controlled light spectra that are useful for inducing various plant responses. Results We have developed a plant lighting system that irradiated a 0.18 m2 area with a highly uniform distribution of photon flux density (PFD. The average photosynthetic PFD (PPFD in the irradiated area was 438 micro-mol m–2 s–1 (coefficient of variation 9.6%, which is appropriate for growing leafy vegetables. The irradiated light includes violet, blue, orange-red, red, and far-red wavelength bands created by LEDs of five types. The PFD and mixing ratio of the five wavelength-band lights are controllable using a computer and drive circuits. The phototropic response of oat coleoptiles was investigated to evaluate plant sensitivity to the light control quality of the lighting system. Oat coleoptiles irradiated for 23 h with a uniformly distributed spectral PFD (SPFD of 1 micro-mol m–2 s–1 nm–1 at every peak wavelength (405, 460, 630, 660, and 735 nm grew almost straight upwards. When they were irradiated with an SPFD gradient of blue light (460 nm peak wavelength, the coleoptiles showed a phototropic curvature in the direction of the greater SPFD of blue light. The greater SPFD gradient induced the greater curvature of coleoptiles. The relation between the phototropic curvature (deg and the blue-light SPFD gradient (micro-mol m–2 s–1 nm–1 m–1 was 2 deg per 1 micro-mol m–2 s–1 nm–1 m–1. Conclusions The plant lighting system, with a computer with a

The narrow-band imaging examination method in otorhinolaryngology

Directory of Open Access Journals (Sweden)

Robert Šifrer

2013-10-01

Full Text Available Early diagnostics could improve the prognosis of patients with squamous-cell carcinomas of the head and neck. Narrow-Band Imaging (NBI is the latest examination method in the group of biologic endoscopies. NBI improves the distinction between malignant and benign mucosal lesions. Early suspect oncologic lesions that may otherwise be missed by normal white light illumination can also be diagnosed. The biggest benefit of NBI technology is achieved by using it together with a HDTV camera that enables better contrast and higher resolution. NBI is based on better imaging of superficial mucosal vasculature. The biologic potential of mucosal lesions could be predicted from vascular changes. The colour of normal mucosa under NBI is blue and green and the vessels show no pathological features. Well-demarcated brownish areas and scattered thick dark spots and abnormal winding and branching out of vessels on the mucosa are all oncologically suspicious features. Authors report the experience from literature on the use of NBI to identify carcinomas of the oral cavity, epipharynx, oropharynx, hypopharynx and larynx and evaluation of unknown primaries. In addition, the literature reports the benefit of NBI in identifying early stage carcinomas in previously irradiated patients. Persistence and recurrence of carcinoma and the development of new primary tumour could easily be missed by using only standard white-light illumination. The method proved to be highly sensitive and specific for predicting malignant changes in the above-mentioned circumstances. Authors report their own experience with NBI technology as well. For further improvement of the method, new technologic development is expected to enable the connection of NBI and HDTV with flexible endoscopes.

Low-dose narrow-band UVB phototherapy combined with topical therapy is effective in psoriasis and does not inhibit systemic T-cell activation

NARCIS (Netherlands)

de Rie, M. A.; Out, T. A.; Bos, J. D.

1998-01-01

Psoriasis is a chronic T-cell-mediated inflammatory skin disease which can be treated with topical medication, phototherapy or systemic medication. A subgroup of psoriatic patients does not respond to monotherapy and needs combination therapy. We used low-dose narrow-band UVB phototherapy, combined

Deep narrow band imagery of the diffuse ISM in M33

Science.gov (United States)

Hester, J. Jeff; Kulkarni, Shrinivas R.

1990-01-01

Very deep narrow band images were obtained for several fields in the local group spiral galaxy M33 using a wide field reimaging Charge Coupled Device (CCD) camera on the 1.5 m telescope at Palomar Observatory. The reimaging system uses a 306 mm collimator and a 58 mm camera lens to put a 16 minute by 16 minute field onto a Texas Instruments 800 x 800 pixel CCD at a resolution of 1.2 arcseconds pixel (-1). The overall system is f/1.65. Images were obtained in the light of H alpha (S II) lambda lambda 6717, 6731, (O III) lambda 5007, and line-free continuum bands 100A wide, centered at 6450A and 5100A. Assuming a distance of 600 kpc to M33 (Humphreys 1980, Ap. J., 241, 587), this corresponds to a linear scale of 3.5 pc pixel (-1), and a field size of 2.8 kpc x 2.8 kpc. Researchers discuss the H alpha imagery of a field centered approx. equal to 8 minutes NE of the nucleus, including the supergiant HII region complex NGC 604. Two 2000 second H alpha images and two 300 second red continuum images were obtained of two slightly offset fields. The fields were offset to allow for discrimination between real emission and possible artifacts in the images. All images were resampled to align them with one of the H alpha frames. The continuum images were normalized to the line images using the results of aperture photometry on a grid of stars in the field, then the rescaled continuum data were directly subtracted from the line data.

Ionic Potential and Band Narrowing as a Source of Orbital Polarization in Nickelate/Insulator Superlattices

Science.gov (United States)

Georgescu, Alexandru B.; Disa, Ankit S.; Kumah, Divine P.; Ismail-Beigi, Sohrab; Walker, Frederick J.; Ahn, Charles H.

Nickelate interfaces display complex, interacting electronic properties such as thickness dependent metal-insulator transitions. One large body of effort involving nickelates has aimed to split the energies of the Ni 3d orbitals (orbital polarization) to make the resulting band structure resemble that of cuprate superconductors. The most commonly studied interfacial system involves superlattices of alternating nickelate and insulating perovksite-structure layers; the resulting orbital polarization at the nickelate-insulator interface is understood as being due to confinement or structural symmetry breaking. By using first principles theory on the NdNiO3/NdAlO3 superlattice, we show that another important source of orbital polarization stems from electrostatic effects: the more ionic nature of the cations in the insulator (when compared to the nickelate) can shift the relative orbital energies of the Ni. We use density functional theory (DFT) and add electronic correlations via slave-bosons to describe the effect of correlation-induced band narrowing on the orbital polarization. Work supported by NSF Grant MRSEC DMR-1119826.

Design of an S band narrow-band bandpass BAW filter

Science.gov (United States)

Gao, Yang; Zhao, Kun-li; Han, Chao

2017-11-01

An S band narrowband bandpass filter BAW with center frequency 2.460 GHz, bandwidth 41MHz, band insertion loss - 1.154 dB, the passband ripple 0.9 dB, the out of band rejection about -42.5dB@2.385 GHz; -45.5dB@2.506 GHz was designed for potential UAV measurement and control applications. According to the design specifications, the design is as follows: each FBAR's stack was designed in BAW filter by using Mason model. Each FBAR's shape was designed with the method of apodization electrode. The layout of BAW filter was designed. The acoustic-electromagnetic cosimulation model was built to validate the performance of the designed BAW filter. The presented design procedure is a common one, and there are two characteristics: 1) an A and EM co-simulation method is used for the final BAW filter performance validation in the design stage, thus ensures over-optimistic designs by the bare 1D Mason model are found and rejected in time; 2) An in-house developed auto-layout method is used to get compact BAW filter layout, which simplifies iterative error-and-try work here and output necessary in-plane geometry information to the A and EM cosimulation model.

Optical observations of the nearby galaxy IC342 with narrow band [SII] and Hα filters. I

Directory of Open Access Journals (Sweden)

Vučetić M.M.

2013-01-01

Full Text Available We present observations of a portion of the nearby spiral galaxy IC342 using narrow band [SII] and Hα filters. These observations were carried out in November 2011 with the 2m RCC telescope at Rozhen National Astronomical Observatory in Bulgaria. In this paper we report coordinates, diameters, Hα and [SII] fluxes for 203 HII regions detected in two fields of view in IC342 galaxy. The number of detected HII regions is 5 times higher than previously known in these two parts of the galaxy. [Projekat Ministarstva nauke Republike Srbije, br. 176005: Emission nebulae: structure and evolution

Generation of narrow energy spread ion beams via collisionless shock waves using ultra-intense 1 um wavelength laser systems

Science.gov (United States)

Albert, Felicie; Pak, A.; Kerr, S.; Lemos, N.; Link, A.; Patel, P.; Pollock, B. B.; Haberberger, D.; Froula, D.; Gauthier, M.; Glenzer, S. H.; Longman, A.; Manzoor, L.; Fedosejevs, R.; Tochitsky, S.; Joshi, C.; Fiuza, F.

2017-10-01

In this work, we report on electrostatic collisionless shock wave acceleration experiments that produced proton beams with peak energies between 10-17.5 MeV, with narrow energy spreads between Δ E / E of 10-20%, and with a total number of protons in these peaks of 1e7-1e8. These beams of ions were created by driving an electrostatic collisionless shock wave in a tailored near critical density plasma target using the ultra-intense ps duration Titan laser that operates at a wavelength of 1 um. The near critical density target was produced through the ablation of an initially 0.5 um thick Mylar foil with a separate low intensity laser. A narrow energy spread distribution of carbon / oxygen ions with a similar velocity to the accelerated proton distribution, consistent with the reflection and acceleration of ions from an electrostatic field, was also observed. This work was supported by Lawrence Livermore National Laboratory's Laboratory Directed Research and Development program under project 15-LW-095, and the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA2734.

Peritoneal vascular density assessment using narrow-band imaging and vascular analysis software, and cytokine analysis in women with and without endometriosis.

Science.gov (United States)

Kuroda, Keiji; Kitade, Mari; Kikuchi, Iwaho; Kumakiri, Jun; Matsuoka, Shozo; Kuroda, Masako; Takeda, Satoru

2010-01-01

The development and onset of endometriosis is associated with angiogenesis and angiogenic factors including cytokines. We analyzed intrapelvic conditions in women with endometriosis via vascular density assessment of grossly normal peritoneum and determination of cytokine levels in peritoneal fluid. Seventy-three patients underwent laparoscopic surgery because of gynecologic disease including endometriosis in our department using a narrow-band imaging system. Each patient was analyzed for peritoneal vascular density using commercially available vascular analysis software (SolemioENDO ProStudy; Olympus Corp, Tokyo, Japan). Each patient was also subjected to analysis of interleukin 6 (IL-6), IL-8, tumor necrosis factor-alpha, and vascular endothelial growth factor concentrations in peritoneal fluid. We defined 4 groups as follows: group 1, endometriosis: gonadotropin-releasing hormone (GnRH) agonist administration group (n=27); group 2, endometriosis: GnRH agonist nonadministration group (n=15); group 3, no endometriosis: GnRH agonist administration group (n=18); and group 4, no endometriosis: GnRH agonist nonadministration group (n=13). No significant differences in peritoneal vascular density between the 4 groups were found under conventional light; however, under narrow-band light, vascular density in the endometriosis groups (groups 1 and 2) was significantly higher. Cytokine analysis of the 4 groups determined that IL-6 and IL-8 concentrations were significantly higher compared with the no endometriosis groups (groups 3 and 4). Tumor necrosis factor-alpha and vascular endothelial growth factor concentrations were not significantly different between groups. In endometriosis, peritoneal vascular density was significantly higher as assessed using the narrow-band imaging system and SolemioENDO ProStudy, whereas GnRH agonist did not obviously decrease vascular density but IL-6 concentration was lower in the GnRH agonist administration group. Copyright (c) 2010 AAGL

Study of Oxidative Stress in Vitiligo and Use of Narrow Band UVB-311 as a Method of Treatment

International Nuclear Information System (INIS)

Fawzy, N.; Rashed, L.

2012-01-01

Vitiligo is an acquired depigmenting disease characterized by circumscribed depigmenting macules devoid of identifiable melanocytes. The disease has uncertain aetiopathogenesis. The aim of this research is to estimate the level of superoxide dismutase (SOD) and catalase (CAT) as antioxidants and Nitric oxide and superoxide anion as oxidants in vitiligo patients and evaluate the clinical effectiveness of narrow band UVB (NB-UVB-311) as a method of treatment and repairing the oxidative stress-induced damage. This study included twenty vitiligo patients and fifteen-age and sex matched control. There was statistically significant increase in the levels of SOD in active vitiligo lesions compared to control (P<0.001). There was statistically significant decrease in the level of CAT in vitiligo skin lesions compared to skin of control. After using NB-UVB- 311 the level of SOD was significantly decreased and CAT level was significantly increased (P<0.001). There was statistically significant increase in the level of nitric oxide and superoxide in vitiligo patients compared to control. After using NB-UVB-311 as treatment, the level of nitric oxide and superoxide anion was significantly decreased (P<0.001) in vitiligo patients. These results provide some evidence regarding the oxidant /antioxidant balance in vitiligo patients and the positive role of narrow band UVB- 311 as a treatment of vitiligo

Bright Single InAsP Quantum Dots at Telecom Wavelengths in Position-Controlled InP Nanowires: The Role of the Photonic Waveguide.

Science.gov (United States)

Haffouz, Sofiane; Zeuner, Katharina D; Dalacu, Dan; Poole, Philip J; Lapointe, Jean; Poitras, Daniel; Mnaymneh, Khaled; Wu, Xiaohua; Couillard, Martin; Korkusinski, Marek; Schöll, Eva; Jöns, Klaus D; Zwiller, Valery; Williams, Robin L

2018-05-09

We report on the site-selected growth of bright single InAsP quantum dots embedded within InP photonic nanowire waveguides emitting at telecom wavelengths. We demonstrate a dramatic dependence of the emission rate on both the emission wavelength and the nanowire diameter. With an appropriately designed waveguide, tailored to the emission wavelength of the dot, an increase in the count rate by nearly 2 orders of magnitude (0.4 to 35 kcps) is obtained for quantum dots emitting in the telecom O-band, showing high single-photon purity with multiphoton emission probabilities down to 2%. Using emission-wavelength-optimized waveguides, we demonstrate bright, narrow-line-width emission from single InAsP quantum dots with an unprecedented tuning range of 880 to 1550 nm. These results pave the way toward efficient single-photon sources at telecom wavelengths using deterministically grown InAsP/InP nanowire quantum dots.

On a business cycle model with fractional derivative under narrow-band random excitation

International Nuclear Information System (INIS)

Lin, Zifei; Li, Jiaorui; Li, Shuang

2016-01-01

This paper analyzes the dynamics of a business cycle model with fractional derivative of order  α (0 < α < 1) subject to narrow-band random excitation, in which fractional derivative describes the memory property of the economic variables. Stochastic dynamical system concepts are integrated into the business cycle model for understanding the economic fluctuation. Firstly, the method of multiple scales is applied to derive the model to obtain the approximate analytical solution. Secondly, the effect of economic policy with fractional derivative on the amplitude of the economic fluctuation and the effect on stationary probability density are studied. The results show macroeconomic regulation and control can lower the stable amplitude of economic fluctuation. While in the process of equilibrium state, the amplitude is magnified. Also, the macroeconomic regulation and control improves the stability of the equilibrium state. Thirdly, how externally stochastic perturbation affects the dynamics of the economy system is investigated.

Narrow band quantitative and multivariate electroencephalogram analysis of peri-adolescent period.

Science.gov (United States)

Martinez, E I Rodríguez; Barriga-Paulino, C I; Zapata, M I; Chinchilla, C; López-Jiménez, A M; Gómez, C M

2012-08-24

The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0-20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages.

Long wavelength approximation of transport processes in a single-band crystal

International Nuclear Information System (INIS)

Ferrari, Loris

2014-01-01

The single band, long wavelength approximation (SBA–LWA) is currently used in textbooks as a quasi-free-particle picture of the motion in a quantum crystal. The resulting transport process might thereby look a trivial issue. In contrast, we shall show that the SBA–LWA hides some controversial aspects that should be clarified at the level of an advanced course of condensed matter physics, and refer to the incompleteness of the SBA representation. In particular, it will be shown that the single-band velocity v 1B , expressed in terms of the projectors on the Bloch states, cannot be a transport velocity in a full sense, since the resulting current violates the continuity equation. The drawback manifests itself as a ‘lost’ current J lost , which provides a non conventional estimate of the limits of accuracy of SBA–LWA. The vanishing of J lost corresponds to the effective mass approximation in which the dispersion relation can be reduced to a quadratic form in the (pseudo) momentum components. In practice, the quantity transported by v 1B is not the bare mass, but the effective mass, until this notion does make sense. Recalling that the non-quadratic expression of the relativistic kinetic energy leads to a difference between the rest and moving mass, the notion of the lost current is finally used as a non-conventional approach to relativistic quantum mechanics, with special reference to Dirac’s theory. (paper)

Highly accurate Michelson type wavelength meter that uses a rubidium stabilized 1560 nm diode laser as a wavelength reference

International Nuclear Information System (INIS)

Masuda, Shin; Kanoh, Eiji; Irisawa, Akiyoshi; Niki, Shoji

2009-01-01

We investigated the accuracy limitation of a wavelength meter installed in a vacuum chamber to enable us to develop a highly accurate meter based on a Michelson interferometer in 1550 nm optical communication bands. We found that an error of parts per million order could not be avoided using famous wavelength compensation equations. Chromatic dispersion of the refractive index in air can almost be disregarded when a 1560 nm wavelength produced by a rubidium (Rb) stabilized distributed feedback (DFB) diode laser is used as a reference wavelength. We describe a novel dual-wavelength self-calibration scheme that maintains high accuracy of the wavelength meter. The method uses the fundamental and second-harmonic wavelengths of an Rb-stabilized DFB diode laser. Consequently, a highly accurate Michelson type wavelength meter with an absolute accuracy of 5x10 -8 (10 MHz, 0.08 pm) over a wide wavelength range including optical communication bands was achieved without the need for a vacuum chamber.

Can optical diagnosis of small colon polyps be accurate? Comparing standard scope without narrow banding to high definition scope with narrow banding.

Science.gov (United States)

Ashktorab, Hassan; Etaati, Firoozeh; Rezaeean, Farahnaz; Nouraie, Mehdi; Paydar, Mansour; Namin, Hassan Hassanzadeh; Sanderson, Andrew; Begum, Rehana; Alkhalloufi, Kawtar; Brim, Hassan; Laiyemo, Adeyinka O

2016-07-28

To study the accuracy of using high definition (HD) scope with narrow band imaging (NBI) vs standard white light colonoscope without NBI (ST), to predict the histology of the colon polyps, particularly those high definition colonoscopes with NBI. The histopathologic diagnosis was reported by pathologists as part of routine care. Of participants in the study, 55 (37%) were male and median (interquartile range) of age was 56 (19-80). Demographic, clinical characteristics, past medical history of patients, and the data obtained by two instruments were not significantly different and two methods detected similar number of polyps. In ST scope 89% of polyps were scope (P = 0.7). The ST scope had a positive predictive value (PPV) and positive likelihood ratio (PLR) of 86% and 4.0 for adenoma compared to 74% and 2.6 for HD scope. There was a trend of higher sensitivity for HD scope (68%) compare to ST scope (53%) with almost the same specificity. The ST scope had a PPV and PLR of 38% and 1.8 for hyperplastic polyp (HPP) compared to 42% and 2.2 for HD scope. The sensitivity and specificity of two instruments for HPP diagnosis were similar. Our results indicated that HD scope was more sensitive in diagnosis of adenoma than ST scope. Clinical diagnosis of HPP with either scope is less accurate compared to adenoma. Colonoscopy diagnosis is not yet fully matched with pathologic diagnosis of colon polyp. However with the advancement of both imaging and training, it may be possible to increase the sensitivity and specificity of the scopes and hence save money for eliminating time and the cost of Immunohistochemistry/pathology.

Polarization filtering in the visible wavelength range using surface plasmon resonance and a sunflower-type photonic quasi-crystal fiber

Science.gov (United States)

Yan, Bei; Wang, Anran; Liu, Exian; Tan, Wei; Xie, Jianlan; Ge, Rui; Liu, Jianjun

2018-04-01

A novel polarization filter based on a sunflower-type photonic quasi-crystal fiber (PQF) is proposed in this paper. We also discuss different methods to tune the filter wavelength. The proposed filter can efficiently produce polarized light with visible wavelengths by using the resonance between the second-order surface plasmon polariton mode and the core mode of the PQF. The filtered wavelength can be tuned between 0.55 µm and 0.68 µm by adjusting the thickness of the gold film. When the thickness of the gold film is 25.3 nm, the resonance loss in the y-polarized direction reaches 11707 dB m‑1 for a wavelength of 0.6326 µm, and the full width at half maximum is only 5 nm. Due to the flexible design and absence of both polarization coupling and polarization dispersion, this polarization filter can be used in devices that require narrow-band filtering.

Micro-Bunched Beam Production at FAST for Narrow Band THz Generation Using a Slit-Mask

Energy Technology Data Exchange (ETDEWEB)

Hyun, J. [Sokendai, Tsukuba; Crawford, D. [Fermilab; Edstrom Jr, D. [Fermilab; Ruan, J. [Fermilab; Santucci, J. [Fermilab; Thurman-Keup, R. [Fermilab; Sen, T. [Fermilab; Thangaraj, J. C. [Fermilab

2018-04-01

We discuss simulations and experiments on creating micro-bunch beams for generating narrow band THz radiation at the Fermilab Accelerator Science and Technology (FAST) facility. The low-energy electron beamline at FAST consists of a photoinjector-based RF gun, two Lband superconducting accelerating cavities, a chicane, and a beam dump. The electron bunches are lengthened with cavity phases set off-crest for better longitudinal separation and then micro-bunched with a slit-mask installed in the chicane. We carried out the experiments with 30 MeV electron beams and detected signals of the micro-bunching using a skew quadrupole magnet in the chicane. In this paper, the details of micro-bunch beam production, the detection of micro-bunching and comparison with simulations are described.

Optical Observations of M81 Galaxy Group in Narrow Band [SII] and H_alpha Filters: Holmberg IX

Directory of Open Access Journals (Sweden)

Arbutina, B.

2009-12-01

Full Text Available We present observations of the nearby tidal dwarf galaxy Holmberg IX in M81 galaxy group in narrow band [SII] and H$alpha$ filters, carried out in March and November 2008 with the 2m RCC telescope at NAO Rozhen, Bulgaria. Our search for resident supernova remnants (identified as sources with enhanced [SII] emission relative to their H$alpha$ emission in this galaxy yielded no sources of this kind, besides M&H 10-11 or HoIX X-1. Nevertheless, we found a number of objects with significant H$alpha$ emission that probably represent uncatalogued HII regions.

Mitigation of Unwanted Forward Narrow-band Radiation from PCBs with a Metamaterial Unit Cell

DEFF Research Database (Denmark)

Ruaro, Andrea; Thaysen, Jesper; Jakobsen, Kaj Bjarne

2013-01-01

Mitigation of EMI from a PCB is obtained through the use of a metamaterial unit cell. The focus is on the reduction of narrow-band radiation in the forward hemisphere when the resonant element is etched on a layer located between the source of radiation and the ground plane. As opposed to previous...... publications in the literature, the aim of this work is the application of a filter to scattered radiation, generalizing the former characterizations based solely upon transmission lines’ insertion loss. The radiating area accounts for traces and components placed on the top layer of a PCB and is simulated via...... a patch antenna. The study exhibits how the radiation pattern and the electric field on the patch antenna change within and outside the resonance bandwidth of the parasitic element. An EMC assessment provides experimental verification of the operating principle....

Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train

International Nuclear Information System (INIS)

Piot, P.; Maxwell, T. J.; Sun, Y.-E; Ruan, J.; Lumpkin, A. H.; Thurman-Keup, R.; Rihaoui, M. M.

2011-01-01

We experimentally demonstrate the production of narrow-band (δf/f≅20% at f≅0.5THz) transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. The bunch train is generated via a transverse-to-longitudinal phase space exchange technique. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.

Charge separation dynamics in a narrow band gap polymer-PbS nanocrystal blend for efficient hybrid solar cells

OpenAIRE

Piliego, Claudia; Manca, Marianna; Kroon, Renee; Yarema, Maksym; Szendrei, Krisztina; Andersson, Mats R.; Heiss, Wolfgang; Loi, Maria A.

2012-01-01

We have demonstrated efficient hybrid solar cells based on lead sulfide (PbS) nanocrystals and a narrow band gap polymer, poly[{2,5-bis(2-hexyldecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl}-alt-{[2,2'-(1,4-phenylene)bis-thiophene]-5,5'-diyl}], (PDPPTPT). An opportune mixing of the two materials led to the formation of an energetically favorable bulk hetero-junction with a broad spectral response. Using a basic device structure, we reached a power conversion efficiency of s...

UWB Filtering Power Divider with Two Narrow Notch-bands and Wide Stop-band

Science.gov (United States)

Wei, Feng; Wang, Xin-Yi; Zou, Xin Tong; Shi, Xiao Wei

2017-12-01

A compact filtering ultra-wideband (UWB) microstrip power divider (PD) with two sharply rejected notch-bands and wide stopband is analyzed and designed in this paper. The proposed UWB PD is based on a conventional Wilkinson power divider, while two stub loaded resonators (SLRs) are coupled into two symmetrical output ports to achieve a bandpass filtering response. The simplified composite right/left-handed (SCRLH) resonators are employed to generate the dual notched bands. Defected ground structure (DGS) is introduced to improve the passband performance. Good insertion/return losses, isolation and notch-band rejection are achieved as demonstrated in both simulation and experiment.

The Low Band Observatory (LOBO): Expanding the VLA Low Frequency Commensal System for Continuous, Broad-band, sub-GHz Observations

Science.gov (United States)

Kassim, Namir E.; Clarke, Tracy E.; Helmboldt, Joseph F.; Peters, Wendy M.; Brisken, Walter; Hyman, Scott D.; Polisensky, Emil; Hicks, Brian

2015-01-01

The Naval Research Laboratory (NRL) and the National Radio Astronomy Observatory (NRAO) are currently commissioning the VLA Low Frequency Ionosphere and Transient Experiment (VLITE) on a subset of JVLA antennas at modest bandwidth. Its bounded scientific goals are to leverage thousands of JVLA on-sky hours per year for ionospheric and transient studies, and to demonstrate the practicality of a prime-focus commensal system on the JVLA. Here we explore the natural expansion of VLITE to a full-antenna, full-bandwidth Low Band Observatory (LOBO) that would follow naturally from a successful VLITE experience. The new Low Band JVLA receivers, coupled with the existing primary focus feeds, can access two frequency bands: 4 band (54 - 86 MHz) and P band (236-492 MHz). The 4 band feeds are newly designed and now undergoing testing. If they prove successful then they can be permanently mounted at the primary focus, unlike their narrow band predecessors. The combination of Low Band receivers and fixed, primary-focus feeds could provide continuous, broad-band data over two complimentary low-frequency bands. The system would also leverage the relatively large fields-of-view of ~10 degrees at 4 band, and ~2.5 degrees at P band, coupling an excellent survey capability with a natural advantage for serendipitous discoveries. We discuss the compelling science case that flows from LOBO's robust imaging and time domain capabilities coupled with thousands of hours of wide-field, JVLA observing time each year. We also touch on the possibility to incorporate Long Wavelength Array (LWA) stations as additional 'dishes' through the LOBO backend, to improve calibration and sensitivity in LOBO's 4 band.

Multi-band emission in a wide wavelength range from tin oxide/Au nanocomposites grown on porous anodic alumina substrate (AAO)

International Nuclear Information System (INIS)

Norek, Małgorzata; Michalska-Domańska, Marta; Stępniowski, Wojciech J.; Ayala, Israel; Bombalska, Aneta; Budner, Bogusław

2013-01-01

The photoluminescence (PL) properties of tin oxide nanostructures are investigated. Three samples of different morphology, induced by deposition process and various geometrical features of nanoporous anodic aluminum oxide (AAO) substrate, are analyzed. X-ray photoelectronic spectroscopy (XPS) analysis reveals the presence of two forms of tin oxide on the surface of all studied samples: SnO and SnO 2 . The former form is typical for reduced surface with bridging oxygen atoms and every other row of in-plane oxygen atoms removed. The oxygen defects give rise to a strong emission in visible region. Two intense PL peaks are observed centered at about 540 (band I) and 620 (band II) nm. The origin of these bands was ascribed to the recombination of electrons from the conduction band (band I) and shallow traps levels (band II) to the surface oxygen vacancy levels. Upon deposition of Au nanoparticles on the top of tin oxide nanostructures the emission at 540 and 620 nm disappears and a new band (band III) occurs in the range >760 nm. The PL mechanism operating in the studied systems is discussed. The tin oxide/Au nanocomposites can be used as efficient multi-band light emitters in a wide (from visible to near infrared) wavelength range.

Ultrabright, narrow-band photon-pair source for atomic quantum memories

Science.gov (United States)

Tsai, Pin-Ju; Chen, Ying-Cheng

2018-06-01

We demonstrate an ultrabright, narrow-band and frequency-tunable photon-pair source based on cavity-enhanced spontaneous parametric down conversion (SPDC) which is compatible with atomic transition of rubidium D 2-line (780 nm) or cesium D 2-line (852 nm). With the pump beam alternating between a high and a low power phase, the output is switching between the optical parametric oscillator (OPO) and photon-pair generation mode. We utilize the OPO output light to lock the cavity length to maintain the double resonances of signal and idler, as well as to lock the signal frequency to cesium atomic transition. With a type-II phase matching and a double-passed pump scheme such that the cluster frequency spacing is larger than the SPDC bandwidth, the photon-pair output is in a nearly single-mode operation as confirmed by a scanning Fabry–Perot interferometer with its output detected by a photomultiplier. The achieved generation and detection rates are 7.24× {10}5 and 6142 s‑1 mW‑1, respectively. The correlation time of the photon pair is 21.6(2.2) ns, corresponding to a bandwidth of 2π × 6.6(6) MHz. The spectral brightness is 1.06× {10}5 s‑1 mW‑1 MHz‑1. This is a relatively high value under a single-mode operation with the cavity-SPDC scheme. The generated single photons can be readily used in experiments related to atomic quantum memories.

A stable wavelength-tunable single frequency and single polarization linear cavity erbium-doped fiber laser

International Nuclear Information System (INIS)

Feng, T; Yan, F P; Li, Q; Peng, W J; Tan, S Y; Feng, S C; Wen, X D; Liu, P

2013-01-01

We report the configuration and operation of a wavelength-tunable single frequency and single polarization erbium-doped fiber laser (EDFL) with a stable and high optical signal to noise ratio (OSNR) laser output. A narrow-band fiber Bragg grating (NBFBG), a FBG-based Fabry–Perot (FP) filter, a polarization controller (PC) and an unpumped erbium-doped fiber (EDF) as a saturable absorber (SA) are employed to realize stable single frequency lasing operation. An all-fiber polarizer (AFP) is introduced to suppress mode hopping and ensure the single polarization mode operation. By adjusting the length of the NBFBG using a stress adjustment module (SAM), four stable single frequency and single polarization laser outputs at wavelengths of 1544.946, 1545.038, 1545.118 and 1545.182 nm are obtained. At room temperature, performance with an OSNR of larger than 60 dB, power fluctuation of less than 0.04 dB, wavelength variation of less than 0.01 nm for about 5 h measurement, and degree of polarization (DOP) of close to 100% has been experimentally demonstrated for the fiber laser operating at these four wavelengths. (paper)

A highly efficient Ho:YAG laser in-band pumped by a linewidth-narrowed Tm:YLF laser

International Nuclear Information System (INIS)

Duan, X M; Yang, C H; Yao, B Q; Wang, Y Z; Zhang, W S

2013-01-01

A highly efficient Tm:YLF-Ho:YAG laser system is presented in this paper. To obtain the narrow linewidth 1908 nm laser output, a volume Bragg grating combined with a Fabry–Perot (FP) etalon were used as wavelength selection devices. The maximum output power of 28.7 W was obtained with a slope efficiency of 42.3% in the Tm:YLF laser. An output wavelength of 1908.1 nm and FWHM linewidth of 60 pm were achieved at the maximum output level. Using this Tm:YLF laser as the pump source, high efficiency continuous wave and Q-switched operation of a Ho:YAG laser was demonstrated. Operating at continuous wave mode, up to 73.3% slope efficiency and 67.4% optical conversion efficiency were obtained in the Ho:YAG laser, corresponding to a diode-to-Ho optical conversion efficiency of 23.7%. For the Q-switched mode, when the incident Tm power was 27.3 W, the maximum single pulse energy of 3.4 mJ, pulse width of 15 ns and peak power of 229.3 kW were achieved at the pulse repetition rate of 5 kHz. The maximum average power of 18.3 W, pulse width of 18 ns and peak power of 103.6 kW were obtained at the pulse repetition rate of 10 kHz. (paper)

Omnidirectional narrow optical filters for circularly polarized light in a nanocomposite structurally chiral medium.

Science.gov (United States)

Avendaño, Carlos G; Palomares, Laura O

2018-04-20

We consider the propagation of electromagnetic waves throughout a nanocomposite structurally chiral medium consisting of metallic nanoballs randomly dispersed in a structurally chiral material whose dielectric properties can be represented by a resonant effective uniaxial tensor. It is found that an omnidirectional narrow pass band and two omnidirectional narrow band gaps are created in the blue optical spectrum for right and left circularly polarized light, as well as narrow reflection bands for right circularly polarized light that can be controlled by varying the light incidence angle and the filling fraction of metallic inclusions.

Experimental studies of narrow band effects in the actinides

Energy Technology Data Exchange (ETDEWEB)

Brodsky, M.B.

1976-01-01

In many actinide metallic systems the f-electrons exhibit band behavior. This is a consequence of direct f-f wave function overlap or hybridization of f-electrons with s-, p-, and d-electrons. The f-bands can be responsible for large electronic densities of states at the Fermi level which may lead to band magnetism of various types. Although the concept of valence instabilities must be approached cautiously especially in the light actinides, it would not be surprising to observe them in the future, especially in Am compounds.

Experimental studies of narrow band effects in the actinides

International Nuclear Information System (INIS)

Brodsky, M.B.

1976-01-01

In many actinide metallic systems the f-electrons exhibit band behavior. This is a consequence of direct f-f wave function overlap or hybridization of f-electrons with s-, p-, and d-electrons. The f-bands can be responsible for large electronic densities of states at the Fermi level which may lead to band magnetism of various types. Although the concept of valence instabilities must be approached cautiously especially in the light actinides, it would not be surprising to observe them in the future, especially in Am compounds

Narrow-band imaging of the inner R Aquarii nebula - Further evidence for shock excitation

International Nuclear Information System (INIS)

Burgarella, D.; Paresce, F.

1991-01-01

The jetlike nebulosity in the inner regions of the symbiotic variable R Aqr was imaged through narrow-band interference filters. A high spatial resolution image in the forbidden N II 6583 A line shows that the relative fluxes of features B and D defined by Paresce et al. (1988) have changed in the sense of a higher D/B brightness ratio at this line in a little over a year with respect to that observed previously in similar seeing conditions. The overall morphology of the jet has remained stable in this period. Line ratios for feature B are presented which can be best understood in terms of excitation of gas clumps surrounding R Aqr by a moving shock. Comparison of the observed fluxes with theoretical expectations yields shock velocity of order 90-100 km/s, a preshock gas density of roughly 10/cu cm, and a gas temperature of roughly 10,000 K. 26 refs

Multispectral Detection with Metal-Dielectric Filters: An Investigation in Several Wavelength Bands with Temporal Coupled-Mode Theory

Science.gov (United States)

Lesmanne, Emeline; Espiau de Lamaestre, Roch; Boutami, Salim; Durantin, Cédric; Dussopt, Laurent; Badano, Giacomo

2016-09-01

Multispectral infrared (IR) detection is of great interest to enhance our ability to gather information from a scene. Filtering is a low-cost alternative to the complex multispectral device architectures to which the IR community has devoted much attention. Multilayer dielectric filters are standard in industry, but they require changing the thickness of at least one layer to tune the wavelength. Here, we pursue an approach based on apertures in a metallic layer of fixed thickness, in which the filtered wavelengths are selected by varying the aperture geometry. In particular, we study filters made of at least one sheet of resonating apertures in metal embedded in dielectrics. We will discuss two interesting problems that arise when one attempts to design such filters. First, metallic absorption must be taken into account. Second, the form and size of the pattern is limited by lithography. We will present some design examples and an attempt at explaining the filtering behavior based on the temporal coupled mode theory. That theory models the filter as a resonator interacting with the environment via loss channels. The transmission is solely determined by the loss rates associated with those channels. This model allows us to give a general picture of the filtering performance and compare their characteristics at different wavelength bands.

Office-based narrow band imaging-guided flexible laryngoscopy tissue sampling: A cost-effectiveness analysis evaluating its impact on Taiwanese health insurance program

OpenAIRE

Fang, Tuan-Jen; Li, Hsueh-Yu; Liao, Chun-Ta; Chiang, Hui-Chen; Chen, I-How

2015-01-01

Narrow band imaging (NBI)-guided flexible laryngoscopy tissue sampling for laryngopharyngeal lesions is a novel technique. Patients underwent the procedure in an office-based setting without being sedated, which is different from the conventional technique performed using direct laryngoscopy. Although the feasibility and effects of this procedure were established, its financial impact on the institution and Taiwanese National Health Insurance program was not determined. Methods: This is a ...

Polyp Detection, Characterization, and Management Using Narrow-Band Imaging with/without Magnification

Directory of Open Access Journals (Sweden)

Takahiro Utsumi

2015-11-01

Full Text Available Narrow-band imaging (NBI is a new imaging technology that was developed in 2006 and has since spread worldwide. Because of its convenience, NBI has been replacing the role of chromoendoscopy. Here we review the efficacy of NBI with/without magnification for detection, characterization, and management of colorectal polyps, and future perspectives for the technology, including education. Recent studies have shown that the next-generation NBI system can detect significantly more colonic polyps than white light imaging, suggesting that NBI may become the modality of choice from the beginning of screening. The capillary pattern revealed by NBI, and the NBI International Colorectal Endoscopic classification are helpful for prediction of histology and for estimating the depth of invasion of colorectal cancer. However, NBI with magnifying colonoscopy is not superior to magnifying chromoendoscopy for estimation of invasion depth. Currently, therefore, chromoendoscopy should also be performed additionally if deep submucosal invasive cancer is suspected. If endoscopists become able to accurately estimate colorectal polyp pathology using NBI, this will allow adenomatous polyps to be resected and discarded; thus, reducing both the risk of polypectomy and costs. In order to achieve this goal, a suitable system for education and training in in vivo diagnostics will be necessary.

A theory for narrow-banded radio bursts at Uranus - MHD surface waves as an energy driver

Science.gov (United States)

Farrell, W. M.; Curtis, S. A.; Desch, M. D.; Lepping, R. P.

1992-01-01

A possible scenario for the generation of the narrow-banded radio bursts detected at Uranus by the Voyager 2 planetary radio astronomy experiment is described. In order to account for the emission burstiness which occurs on time scales of hundreds of milliseconds, it is proposed that ULF magnetic surface turbulence generated at the frontside magnetopause propagates down the open/closed field line boundary and mode-converts to kinetic Alfven waves (KAW) deep within the polar cusp. The oscillating KAW potentials then drive a transient electron stream that creates the bursty radio emission. To substantiate these ideas, Voyager 2 magnetometer measurements of enhanced ULF magnetic activity at the frontside magnetopause are shown. It is demonstrated analytically that such magnetic turbulence should mode-convert deep in the cusp at a radial distance of 3 RU.

Water vapor transmittance models for narrow bands in the 13 to 19 μm spectral region

International Nuclear Information System (INIS)

Weichel, R.L.

1983-10-01

The purpose of this report is to document the development of water vapor transmittance models for narrow bands (satellite sensor channels) in the 13 to 19 μm spectral region. The models are the result of research efforts of the author in 1971-1972 while on active duty with the US Air Force at the Air Force Global Weather Central (AFGWC). The models were developed for application in studies involving a temperature profiling sensor system carried aboard the satellites of the Defense Meteorological Satellite Program (DMSP), formerly DAPP. Recently, (Lovill et al., 1978; Luther et al., 1981) the models were implemented for studies concerned with methodologies to retrieve total atmospheric column ozone from measurements of newer DMSP Block 5D series satellite sensors with similar channels (see Nichols, 1975)

Wavelength dependence four-wave mixing spectroscopy in a micrometric atomic vapour

International Nuclear Information System (INIS)

Yuan-Yuan, Li; Li, Li; Yan-Peng, Zhang; Si-Wen, Bi

2010-01-01

This paper presents a theoretical study of wavelength dependence four-wave-mixing (FWM) spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke-narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour. (general)

Infrared diffuse interstellar bands

Science.gov (United States)

Galazutdinov, G. A.; Lee, Jae-Joon; Han, Inwoo; Lee, Byeong-Cheol; Valyavin, G.; Krełowski, J.

2017-05-01

We present high-resolution (R ˜ 45 000) profiles of 14 diffuse interstellar bands in the ˜1.45 to ˜2.45 μm range based on spectra obtained with the Immersion Grating INfrared Spectrograph at the McDonald Observatory. The revised list of diffuse bands with accurately estimated rest wavelengths includes six new features. The diffuse band at 15 268.2 Å demonstrates a very symmetric profile shape and thus can serve as a reference for finding the 'interstellar correction' to the rest wavelength frame in the H range, which suffers from a lack of known atomic/molecular lines.

Wavelength selection in traveling-wave convection in a fluid mixture

International Nuclear Information System (INIS)

Surko, C.M.; Eaton, K.D.; Baxter, G.W.; Iwata, K.

1993-01-01

The mechanisms by which a one-dimensional pattern of traveling waves changes wavelength (i.e. the Eckhaus instability) is studied in a binary fluid mixture. Propagating wavelength modulations develop when the Rayleigh number of the system is decreased below a wavelength-dependent threshold, commonly referred to as the Eckhaus boundary. These wavelength modulations increase in amplitude and narrow in spatial extent until they trigger the creation or annihilation of convection roll pairs and thereby change the average wavelength of the system. The authors find qualitatively different dynamics for wavelength-increasing events and wavelength-decreasing events; these differences are due to the strong wavelength dependence of the group velocity

Narrow Bandwidth Top-Emitting OLEDs Designed for Rhodamine 6G Excitation in Biological Sensing Applications

Directory of Open Access Journals (Sweden)

Matthias Jahnel

2015-11-01

Full Text Available Organic light emitting diodes (OLED are promising candidates offering in optical sensor applications to detect different gas compositions and excitable optical marker groups in chemical and biological processes. They enable attractive solutions for monitoring the gas phase composition of e.g., dissolved molecular oxygen (O2 species in bio reactors or excitation of fluorescent markers. In this work, we investigate different OLED devices for biomedical applications to excite the fluorescent dye rhodamine 6G (R6G. The OLED devices are built in top emission geometry comprising a distributed Bragg reflector (DBR acting as optical mirror. The OLED is optimized to provide a very narrow emission characteristic to excite the R6G at 530 nm wavelength and enabling the possibility to minimize the optical crosstalk between the OLED electroluminescence and the fluorescence of R6G. The DBR includes a thin film encapsulation and enables the narrowing of the spectral emission band depending on the number of DBR pairs. The comparison between optical simulation data and experimental results exhibits good agreement and proves process stability.

Single frequency narrow linewidth 2 micron laser, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — NASA needs narrow linewidth lasers in the 1.5 or 2 micron wavelength regime for coherent Lidar applications. The laser should be tunable by several nm and frequency...

Josephson frequency meter for millimeter and submillimeter wavelengths

Energy Technology Data Exchange (ETDEWEB)

Anischenko, S.E.; Larkin, S.Y.; Chaikovsky, V.I. [State Research Center, Kiev (Ukraine)] [and others

1994-12-31

Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoff for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decreases with the increase of wavelength due to diffraction losses. That requires the apriori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is the one based on frequency conversion, resonance and interferrometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain panoramic display of the results as well as full automation of the measuring process.

Josephson frequency meter for millimeter and submillimeter wavelengths

International Nuclear Information System (INIS)

Anischenko, S.E.; Larkin, S.Y.; Chaikovsky, V.I.

1994-01-01

Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoff for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decreases with the increase of wavelength due to diffraction losses. That requires the apriori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is the one based on frequency conversion, resonance and interferrometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain panoramic display of the results as well as full automation of the measuring process

Multiwavelength Monitoring of the Enigmatic Narrow-Line Seyfert 1 PMN J0948 0022 in March-July 2009

Energy Technology Data Exchange (ETDEWEB)

Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R. /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E. /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, T.H.; /Washington U., Seattle; Caliandro, G.A.; /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /NASA, Goddard /NASA, Goddard /CSST, Baltimore /SISSA, Trieste /Naval Research Lab, Wash., D.C. /George Mason U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Garching, Max Planck Inst., MPE /Stockholm U. /Stockholm U., OKC /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /ASDC, Frascati /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Ecole Polytechnique /Brera Observ. /INFN, Trieste /Bonn, Max Planck Inst., Radioastron. /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors..

2012-03-29

Following the recent discovery of {gamma} rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z = 0.5846), we started a multiwavelength campaign from radio to {gamma} rays, which was carried out between the end of 2009 March and the beginning of July. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to {gamma}-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the {gamma}-ray emission. The largest flux change, about a factor of about 4, occurred in the X-ray band. The smallest was at ultraviolet and near-infrared frequencies, where the rate of the detected photons dropped by a factor 1.6-1.9. At optical wavelengths, where the sampling rate was the highest, it was possible to observe day scale variability, with flux variations up to a factor of about 3. The behavior of PMN J0948+0022 observed in this campaign and the calculated power carried out by its jet in the form of protons, electrons, radiation, and magnetic field are quite similar to that of blazars, specifically of flat-spectrum radio quasars. These results confirm the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.

MULTIWAVELENGTH MONITORING OF THE ENIGMATIC NARROW-LINE SEYFERT 1 PMN J0948+0022 IN 2009 MARCH-JULY

International Nuclear Information System (INIS)

Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Bloom, E. D.; Borgland, A. W.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bonamente, E.; Brigida, M.; Bruel, P.; Burnett, T. H.

2009-01-01

Following the recent discovery of γ rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z = 0.5846), we started a multiwavelength campaign from radio to γ rays, which was carried out between the end of 2009 March and the beginning of July. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to γ-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the γ-ray emission. The largest flux change, about a factor of about 4, occurred in the X-ray band. The smallest was at ultraviolet and near-infrared frequencies, where the rate of the detected photons dropped by a factor 1.6-1.9. At optical wavelengths, where the sampling rate was the highest, it was possible to observe day scale variability, with flux variations up to a factor of about 3. The behavior of PMN J0948+0022 observed in this campaign and the calculated power carried out by its jet in the form of protons, electrons, radiation, and magnetic field are quite similar to that of blazars, specifically of flat-spectrum radio quasars. These results confirm the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.

Simulation of the Application Layer in NarrowBand Networks with Conditional Data Injection XML Scheme Based on Universal Data Generator

Directory of Open Access Journals (Sweden)

Ondrej Vondrous

2017-01-01

Full Text Available In this article, we would like to deal with challenges and analysis approaches in the area of narrow band communication networks. Especially those networks which use TCP/IP protocol family. We also present a new universal data generator for OMNeT++ simulation environment. We created this generator to satisfy the evaluation, stress testing and benchmarking demands of more and more complex industrial and the Internet of Things networks. We also present the methods for evaluation and comparison of results obtained from simulated and real TCP/IP based networks in this article.

GROUND-BASED Paα NARROW-BAND IMAGING OF LOCAL LUMINOUS INFRARED GALAXIES. I. STAR FORMATION RATES AND SURFACE DENSITIES

Energy Technology Data Exchange (ETDEWEB)

Tateuchi, Ken; Konishi, Masahiro; Motohara, Kentaro; Takahashi, Hidenori; Kato, Natsuko Mitani; Kitagawa, Yutaro; Todo, Soya; Toshikawa, Koji; Sako, Shigeyuki; Uchimoto, Yuka K.; Ohsawa, Ryou; Asano, Kentaro; Kamizuka, Takafumi; Nakamura, Tomohiko; Okada, Kazushi [Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Ita, Yoshifusa [Astronomical Institute, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Komugi, Shinya [Division of Liberal Arts, Kogakuin University, 2665-1, Hachioji, Tokyo 192-0015 (Japan); Koshida, Shintaro [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); Manabe, Sho [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan); Nakashima, Asami, E-mail: tateuchi@ioa.s.u-tokyo.ac.jp [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); and others

2015-03-15

Luminous infrared galaxies (LIRGs) are enshrouded by a large amount of dust produced by their active star formation, and it is difficult to measure their activity in optical wavelengths. We have carried out Paα narrow-band imaging observations of 38 nearby star forming galaxies including 33 LIRGs listed in the IRAS Revised Bright Galaxy Sample catalog with the Atacama Near InfraRed camera on the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope (miniTAO). Star formation rates (SFRs) estimated from the Paα fluxes, corrected for dust extinction using the Balmer decrement method (typically A{sub V} ∼ 4.3 mag), show a good correlation with those from the bolometric infrared luminosity of the IRAS data within a scatter of 0.27 dex. This suggests that the correction of dust extinction for the Paα flux is sufficient in our sample. We measure the physical sizes and surface densities of infrared luminosities (Σ{sub L(IR)}) and the SFR (Σ{sub SFR}) of star forming regions for individual galaxies, and we find that most of the galaxies follow a sequence of local ultra-luminous or luminous infrared galaxies (U/LIRGs) on the L(IR)-Σ{sub L(IR)} and SFR-Σ{sub SFR} plane. We confirm that a transition of the sequence from normal galaxies to U/LIRGs is seen at L(IR) = 8 × 10{sup 10} L {sub ☉}. Also, we find that there is a large scatter in physical size, different from normal galaxies or ULIRGs. Considering the fact that most U/LIRGs are merging or interacting galaxies, this scatter may be caused by strong external factors or differences in their merging stages.

Detection Range Estimation of UV Spectral Band Laser Radar

Directory of Open Access Journals (Sweden)

V. A. Gorodnichev

2014-01-01

Full Text Available Recently, has come into existence an interest in the systems operating in the ultra-violet (UF band of wavelengths, which use other spectral information (coefficients of reflection or radiation in UF range about location objects, than laser systems in the visible, near or average infrared bands. Thus, a point is not only to receive additional (in another spectral range information on location objects. Laser radiation in the UF spectral band of 0.315 – 0.4 microns is safer than laser radiation with the wavelengths of 0.38 – 1.4 microns.The work presents a comparative estimation of the detection systems range of laser radars in the UV and visible spectral bands for the following wavelengths of radiation:- UF band: 0.266 microns (the fourth harmonic of YAG-laser activated by neodymium ions, 0.308 microns (the XeCl-excimer laser, 0.355 microns (the third harmonic of YAG-laser activated by neodymium ions;- visible band: 0.532 microns (the second harmonic of YAG-laser activated by neodymium ions.Results of calculations show that for the horizontal pathway in the terrestrial atmosphere at the selected radiation wavelengths a detection range is in the range of 2510m – 5690 m.The maximum range of detection corresponds to the visible spectral band. A sweep range decreases with transition to the UF band. This is caused by the fact that with transition to the UF band there is a rise of atmosphere attenuation (generally, because of absorption by ozone, this effect being smoothed by reducing background radiation.In the UF band a wavelength of 0.355 microns is the most acceptable. For this wavelength a detection range is about 1,5 times less (in comparison with the visible band of 0.532 microns. However, this is the much more eye-safe wavelength. With transition to the UV band a detection range decreases not that much and can be compensated by changing parameters of transmitting or receiving channels of laser radar.

Effect of combination of fractional CO2 laser and narrow-band ultraviolet B versus narrow-band ultraviolet B in the treatment of non-segmental vitiligo.

Science.gov (United States)

El-Zawahry, Mohamed Bakr; Zaki, Naglaa Sameh; Wissa, Marian Youssry; Saleh, Marwah Adly

2017-12-01

The present study was designed to evaluate the effect of combining fractional CO 2 laser with narrow-band ultraviolet B (NB-UVB) versus NB-UVB in the treatment of non-segmental vitiligo. The study included 20 patients with non-segmental stable vitiligo. They were divided into two groups. Group I received a single session of fractional CO 2 laser therapy on the right side of the body followed by NB-UVB phototherapy twice per week for 8 weeks. Group II received a second session of fractional CO 2 laser therapy after 4 weeks from starting treatment with NB-UVB. The vitiligo lesions were assessed before treatment and after 8 weeks of treatment by VASI. At the end of the study period, the vitiligo area score index (VASI) in group I decreased insignificantly on both the right (-2.6%) and left (-16.4%) sides. In group II, VASI increased insignificantly on the right (+14.4%) and left (+2.5%) sides. Using Adobe Photoshop CS6 extended program to measure the area of vitiligo lesions, group I showed a decrease of -1.02 and -6.12% in the mean area percentage change of vitiligo lesions on the right and left sides, respectively. In group II the change was +9.84 and +9.13% on the right and left sides, respectively. In conclusion, combining fractional CO 2 laser with NB-UVB for the treatment of non-segmental vitiligo did not show any significant advantage over treatment with NB-UVB alone. Further study of this combination for longer durations in the treatment of vitiligo is recommended.

A fast switch, combiner and narrow-band filter for high-power millimetre wave beams

Science.gov (United States)

Kasparek, W.; Petelin, M. I.; Shchegolkov, D. Yu; Erckmann, V.; Plaum, B.; Bruschi, A.; ECRH Groups at IPP Greifswald; Karlsruhe, FZK; Stuttgart, IPF

2008-05-01

A fast directional switch (FADIS) is described, which allows controlled switching of high-power microwaves between two outputs. A possible application could be synchronous stabilization of neoclassical tearing modes (NTMs). Generally, the device can be used to share the installed EC power between different types of launchers or different applications (e.g. in ITER, midplane/upper launcher). The switching is performed electronically without moving parts by a small frequency-shift keying of the gyrotron (some tens of megahertz), and a narrow-band diplexer. The device can be operated as a beam combiner also, which offers attractive transmission perspectives in multi-megawatt ECRH systems. In addition, these diplexers are useful for plasma diagnostic systems employing high-power sources due to their filter characteristics. The principle and the design of a four-port quasi-optical resonator diplexer is presented. Low-power measurements of switching contrast, mode purity and efficiency show good agreement with theory. Preliminary frequency modulation characteristics of gyrotrons are shown, and first results from high-power switching experiments using the ECRH system for W7-X are presented.

A fast switch, combiner and narrow-band filter for high-power millimetre wave beams

International Nuclear Information System (INIS)

Kasparek, W.; Plaum, B.; Petelin, M.I.; Shchegolkov, D.Yu; Erckmann, V.; Bruschi, A.

2008-01-01

A fast directional switch (FADIS) is described, which allows controlled switching of high-power microwaves between two outputs. A possible application could be synchronous stabilization of neoclassical tearing modes (NTMs). Generally, the device can be used to share the installed EC power between different types of launchers or different applications (e.g. in ITER, midplane/upper launcher). The switching is performed electronically without moving parts by a small frequency-shift keying of the gyrotron (some tens of megahertz), and a narrow-band diplexer. The device can be operated as a beam combiner also, which offers attractive transmission perspectives in multi-megawatt ECRH systems. In addition, these diplexers are useful for plasma diagnostic systems employing high-power sources due to their filter characteristics. The principle and the design of a four-port quasi-optical resonator diplexer is presented. Low-power measurements of switching contrast, mode purity and efficiency show good agreement with theory. Preliminary frequency modulation characteristics of gyrotrons are shown, and first results from high-power switching experiments using the ECRH system for W7-X are presented

Multiple-wavelength Variability and Quasi-periodic Oscillation of PMN J0948+0022

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jin [Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Zhang, Hai-Ming; Zhu, Yong-Kai; Lu, Rui-Jing; Liang, En-Wei [Guangxi Key Laboratory for Relativistic Astrophysics, Department of Physics, Guangxi University, Nanning 530004 (China); Yi, Ting-Feng [Department of Physics, Yunnan Normal University, Kunming 650500 (China); Yao, Su, E-mail: jinzhang@bao.ac.cn [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

2017-11-01

We present a comprehensive analysis of multiple-wavelength observational data of the first GeV-selected narrow-line Seyfert 1 galaxy PMN J0948+0022. We derive its light curves in the γ -ray and X-ray bands from the data observed with Fermi /LAT and Swift /XRT, and generate the optical and radio light curves by collecting the data from the literature. These light curves show significant flux variations. With the LAT data we show that this source is analogous to typical flat spectrum radio quasars in the L {sub γ} –Γ {sub γ} plane, where L {sub γ} and Γ {sub γ} are the luminosity and spectral index in the LAT energy band. The γ -ray flux is correlated with the V-band flux with a lag of ∼44 days, and a moderate quasi-periodic oscillation (QPO) with a periodicity of ∼490 days observed in the LAT light curve. A similar QPO signature is also found in the V-band light curve. The γ -ray flux is not correlated with the radio flux in 15 GHz, and no similar QPO signature is found at a confidence level of 95%. Possible mechanisms of the QPO are discussed. We propose that gravitational-wave observations in the future may clarify the current plausible models for the QPO.

A Compact UWB Antenna with a Quarter-Wavelength Strip in a Rectangular Slot for 5.5 GHz Band Notch

Directory of Open Access Journals (Sweden)

Pichet Moeikham

2013-01-01

Full Text Available The limitation of the electromagnetic interferences (EMIs caused by UWB radiating sources into WLAN/WiMAX communication systems operating in the frequency band located around 5.5 GHz requires the adoption of appropriate design features. To this purpose, a notch filter integrated into an UWB antenna, which is able to ensure a better electrical insulation between the two mentioned communication systems with respect to that already presented by the authors Moeikham et al. (2011, is proposed in this paper. The proposed filter, consisting in a rectangular slot including a quarter-wavelength strip integrated on the lower inner edge of the UWB radiating patch, is capable of reducing the energy emission in the frequency range between 5.1 and 5.75 GHz resulting in lower EMIs with sensible electronic equipments working in this frequency band. The antenna structure has no need to be tuned after inserting the rectangle slot with a quarter-wavelength strip. The proposed antenna has potential to minimize the EMIs at a frequency range from 5.1 to 5.75 GHz. The radiation patterns are given nearly omnidirectional in plane and likely bidirectional in plane at all frequencies by the proposed antenna. Therefore, this antenna is suitable to apply for various UWB applications.

Photonic generation of FCC-compliant UWB pulses based on modified Gaussian quadruplet and incoherent wavelength-to-time conversion

Science.gov (United States)

Mu, Hongqian; Wang, Muguang; Tang, Yu; Zhang, Jing; Jian, Shuisheng

2018-03-01

A novel scheme for the generation of FCC-compliant UWB pulse is proposed based on modified Gaussian quadruplet and incoherent wavelength-to-time conversion. The modified Gaussian quadruplet is synthesized based on linear sum of a broad Gaussian pulse and two narrow Gaussian pulses with the same pulse-width and amplitude peak. Within specific parameter range, FCC-compliant UWB with spectral power efficiency of higher than 39.9% can be achieved. In order to realize the designed waveform, a UWB generator based on spectral shaping and incoherent wavelength-to-time mapping is proposed. The spectral shaper is composed of a Gaussian filter and a programmable filter. Single-mode fiber functions as both dispersion device and transmission medium. Balanced photodetection is employed to combine linearly the broad Gaussian pulse and two narrow Gaussian pulses, and at same time to suppress pulse pedestals that result in low-frequency components. The proposed UWB generator can be reconfigured for UWB doublet by operating the programmable filter as a single-band Gaussian filter. The feasibility of proposed UWB generator is demonstrated experimentally. Measured UWB pulses match well with simulation results. FCC-compliant quadruplet with 10-dB bandwidth of 6.88-GHz, fractional bandwidth of 106.8% and power efficiency of 51% is achieved.

Superconductivity in narrow-band systems with local nonretarded attractive interactions

International Nuclear Information System (INIS)

Micnas, R.; Ranninger, J.; Robaszkiewicz, S.

1990-01-01

In narrow-band systems electrons can interact with each other via a short-range nonretarded attractive potential. The origin of such an effective local attraction can be polaronic or it can be due to a coupling between electrons and excitons or plasmons. It can also result from purely chemical (electronic) mechanisms, especially in compounds with elements favoring disproportionation of valent states. These mechanisms are discussed and an exhaustive list of materials in which such local electron pairing occurs is given. The authors review the thermodynamic and electromagnetic properties of such systems in several limiting scenarios: (i) Systems with on-site pairing which can be described by the extended negative-U Hubbard model. The strong-attraction limit of this model, at which it reduces to a system of tightly bound electron pairs (bipolarons) on a lattice, is extensively discussed. These electron pairs behaving as hard-core charged bosons can exhibit a superconducting state analogous to that of superfluid 4 He II. The changeover from weak-attraction BCS-like superconductivity to the superfluidity of charged hard-core bosons is examined. (ii) Systems with intersite pairing described by an extended Hubbard model with U>0 and nearest-neighbor attraction and/or nearest-neighbor spin exchange as well as correlated hopping. (iii) A mixture of local pairs and itinerant electrons interacting via a charge-exchange mechanism giving rise to a mutually induced superconductivity in both subsystems. The authors discuss to what extent the picture of local pairing, and in particular superfluidity of hard-core charged bosons on a lattice, can be an explanation for the superconducting and normal-state properties of the high-T c oxides: doped BaBiO 3 and the cuprates

Competitive behavior of photons contributing to junction voltage jump in narrow band-gap semiconductor multi-quantum-well laser diodes at lasing threshold

Energy Technology Data Exchange (ETDEWEB)

Feng, Liefeng, E-mail: fengliefeng@tju.edu.cn, E-mail: lihongru@nankai.edu.cn; Yang, Xiufang; Wang, Cunda; Yao, Dongsheng [Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Faculty of Science, Tianjin University, Tianjin 300072 (China); Li, Yang [Business and Vocational College of Hainan, Haikou 570203 (China); Li, Ding; Hu, Xiaodong [Research Center for Wide Band Gap Semiconductors, State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Li, Hongru, E-mail: fengliefeng@tju.edu.cn, E-mail: lihongru@nankai.edu.cn [State Key Laboratory for Medicinal Chemistry and Biology, College of Pharmacy, Nankai University, Tianjin 300071 (China)

2015-04-15

The junction behavior of different narrow band-gap multi-quantum-well (MQW) laser diodes (LDs) confirmed that the jump in the junction voltage in the threshold region is a general characteristic of narrow band-gap LDs. The relative change in the 1310 nm LD is the most obvious. To analyze this sudden voltage change, the threshold region is divided into three stages by I{sub th}{sup l} and I{sub th}{sup u}, as shown in Fig. 2; I{sub th}{sup l} is the conventional threshold, and as long as the current is higher than this threshold, lasing exists and the IdV/dI-I plot drops suddenly; I{sub th}{sup u} is the steady lasing point, at which the separation of the quasi-Fermi levels of electron and holes across the active region (V{sub j}) is suddenly pinned. Based on the evolutionary model of dissipative structure theory, the rate equations of the photons in a single-mode LD were deduced in detail at I{sub th}{sup l} and I{sub th}{sup u}. The results proved that the observed behavior of stimulated emission suddenly substituting for spontaneous emission, in a manner similar to biological evolution, must lead to a sudden increase in the injection carriers in the threshold region, which then causes the sudden increase in the junction voltage in this region.

Competitive behavior of photons contributing to junction voltage jump in narrow band-gap semiconductor multi-quantum-well laser diodes at lasing threshold

International Nuclear Information System (INIS)

Feng, Liefeng; Yang, Xiufang; Wang, Cunda; Yao, Dongsheng; Li, Yang; Li, Ding; Hu, Xiaodong; Li, Hongru

2015-01-01

The junction behavior of different narrow band-gap multi-quantum-well (MQW) laser diodes (LDs) confirmed that the jump in the junction voltage in the threshold region is a general characteristic of narrow band-gap LDs. The relative change in the 1310 nm LD is the most obvious. To analyze this sudden voltage change, the threshold region is divided into three stages by I th l and I th u , as shown in Fig. 2; I th l is the conventional threshold, and as long as the current is higher than this threshold, lasing exists and the IdV/dI-I plot drops suddenly; I th u is the steady lasing point, at which the separation of the quasi-Fermi levels of electron and holes across the active region (V j ) is suddenly pinned. Based on the evolutionary model of dissipative structure theory, the rate equations of the photons in a single-mode LD were deduced in detail at I th l and I th u . The results proved that the observed behavior of stimulated emission suddenly substituting for spontaneous emission, in a manner similar to biological evolution, must lead to a sudden increase in the injection carriers in the threshold region, which then causes the sudden increase in the junction voltage in this region

Narrow Band Imaging Enhances the Detection Rate of Penetration and Aspiration in FEES.

Science.gov (United States)

Nienstedt, Julie C; Müller, Frank; Nießen, Almut; Fleischer, Susanne; Koseki, Jana-Christiane; Flügel, Till; Pflug, Christina

2017-06-01

Narrow band imaging (NBI) is widely used in gastrointestinal, laryngeal, and urological endoscopy. Its original purpose was to visualize vessels and epithelial irregularities. Based on our observation that adding NBI to common white light (WL) improves the contrast of the test bolus in fiberoptic endoscopic evaluation of swallowing (FEES), we now investigated the potential value of NBI in swallowing disorders. 148 FEES images were analyzed from 74 consecutive patients with swallowing disorders, including 74 with and 74 without NBI. All images were evaluated by four dysphagia specialists. Findings were classified according to Rosenbek's penetration-aspiration scale modified for evaluating these FEES images. Intra- and inter-rater reliability was determined as well as observer confidence. A better visualization of the bolus is the main advantage of NBI in FEES. This generally leads to sharper optical contrasts and better detection of small bolus quantities. Accordingly, NBI enhances the detection rate of penetration and aspiration. On average, identification of laryngeal penetration increased from 40 to 73% and of aspiration from 13 to 24% (each p dysphagia evaluation and shortening FEES evaluation time. It leads to a markedly higher detection rate of pathological findings. The significantly better intra- and inter-rater reliability argues further for a better overall reproducibly of FEES interpretation.

Tuning the band gap of PbCrO{sub 4} through high-pressure: Evidence of wide-to-narrow semiconductor transitions

Energy Technology Data Exchange (ETDEWEB)

Errandonea, D., E-mail: daniel.errandonea@uv.es [Departamento de Física Aplicada-ICMUV, Universitat de València, MALTA ConsoliderTeam, C/Dr. Moliner 50, 46100 Burjassot (Spain); Bandiello, E.; Segura, A. [Departamento de Física Aplicada-ICMUV, Universitat de València, MALTA ConsoliderTeam, C/Dr. Moliner 50, 46100 Burjassot (Spain); Hamlin, J.J.; Maple, M.B. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Rodriguez-Hernandez, P.; Muñoz, A. [Departamento de Física Fundamental II, Instituto de Materiales y Nanotecnología, Universidad de La Laguna, MALTA ConsoliderTeam, La Laguna, 38205 Tenerife (Spain)

2014-02-25

Highlights: • Electronic and optical properties of PbCrO{sub 4} are studied under compression. • Band-gap collapses are observed and correlated with structural phase transitions. • PbCrO{sub 4} band-gap is reduced from 2.3 to 0.8 eV in a 20 GPa range. • PbCrO{sub 4} is an n-type semiconductor with donor levels associated to Frenkel defects. • A deep-to-shallow donor transformation at HP induces a large resistivity decrease. -- Abstract: The electronic transport properties and optical properties of lead(II) chromate (PbCrO{sub 4}) have been studied at high pressure by means of resistivity, Hall-effect, and optical-absorption measurements. Band-structure first-principle calculations have been also performed. We found that the low-pressure phase is a direct band-gap semiconductor (Eg = 2.3 eV) that shows a high resistivity. At 3.5 GPa, associated to a structural phase transition, a band-gap collapse takes place, becoming Eg = 1.8 eV. At the same pressure the resistivity suddenly decreases due to an increase of the carrier concentration. In the HP phase, PbCrO{sub 4} behaves as an n-type semiconductor, with a donor level probably associated to the formation of oxygen vacancies. At 15 GPa a second phase transition occurs to a phase with Eg = 1.2 eV. In this phase, the resistivity increases as pressure does probably due to the self-compensation of donor levels and the augmentation of the scattering of electrons with ionized impurities. In the three phases the band gap red shifts under compression. At 20 GPa, Eg reaches a value of 0.8 eV, behaving PbCrO{sub 4} as a narrow-gap semiconductor.

Band gap effects of hexagonal boron nitride using oxygen plasma

International Nuclear Information System (INIS)

Sevak Singh, Ram; Leong Chow, Wai; Yingjie Tay, Roland; Hon Tsang, Siu; Mallick, Govind; Tong Teo, Edwin Hang

2014-01-01

Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6 eV of pristine h-BN to 4.31 eV when exposed to oxygen plasma for 12 s. The narrowing of band gap causes the reduction in electrical resistance by ∼100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing

Band gap effects of hexagonal boron nitride using oxygen plasma

Energy Technology Data Exchange (ETDEWEB)

Sevak Singh, Ram; Leong Chow, Wai [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Yingjie Tay, Roland [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Hon Tsang, Siu [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Mallick, Govind [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); Tong Teo, Edwin Hang, E-mail: htteo@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

2014-04-21

Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6 eV of pristine h-BN to 4.31 eV when exposed to oxygen plasma for 12 s. The narrowing of band gap causes the reduction in electrical resistance by ∼100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

MRI of surgically created pulmonary artery narrowing in the dog

Energy Technology Data Exchange (ETDEWEB)

Hernandez, R.J.; Rocchini, A.P.; Bove, E.L.; Chenevert, T.L.; Gubin, B. (Michigan Univ., Ann Arbor (USA). Dept. of Radiology)

1989-11-01

Narrowing of the pulmonary arteries was created surgically in twelve dogs. In six of the dogs the narrowing was central (main pulmonary artery), and in the remaining six the narrowing was located peripherally at the hilar level of the right pulmonary artery beyond the pericardial reflection. MRI and angiography were performed in all dogs. MRI clearly delineated the site of the pulmonary band and the caliber of the pulmonary artery at the site of the band in all dogs (N=6). MRI was not able to visualize any of the stenosis of the right pulmonary arteries at the hila, beyond the pericardial reflection. In addition, optimal imaging planes to depict each segment of the central pulmonary arteries were determined. The capability to image in oblique planes is essential in evaluating the morphology of the central pulmonary arteries. (orig.).

MRI of surgically created pulmonary artery narrowing in the dog

International Nuclear Information System (INIS)

Hernandez, R.J.; Rocchini, A.P.; Bove, E.L.; Chenevert, T.L.; Gubin, B.

1989-01-01

Narrowing of the pulmonary arteries was created surgically in twelve dogs. In six of the dogs the narrowing was central (main pulmonary artery), and in the remaining six the narrowing was located peripherally at the hilar level of the right pulmonary artery beyond the pericardial reflection. MRI and angiography were performed in all dogs. MRI clearly delineated the site of the pulmonary band and the caliber of the pulmonary artery at the site of the band in all dogs (N=6). MRI was not able to visualize any of the stenosis of the right pulmonary arteries at the hila, beyond the pericardial reflection. In addition, optimal imaging planes to depict each segment of the central pulmonary arteries were determined. The capability to image in oblique planes is essential in evaluating the morphology of the central pulmonary arteries. (orig.)

Thermal tuning On narrow linewidth fiber laser

Science.gov (United States)

Han, Peiqi; Liu, Tianshan; Gao, Xincun; Ren, Shiwei

2010-10-01

At present, people have been dedicated to high-speed and large-capacity optical fiber communication system. Studies have been shown that optical wavelength division multiplexing (WDM) technology is an effective means of communication to increase the channel capacity. Tunable lasers have very important applications in high-speed, largecapacity optical communications, and distributed sensing, it can provide narrow linewidth and tunable laser for highspeed optical communication. As the erbium-doped fiber amplifier has a large gain bandwidth, the erbium-doped fiber laser can be achieved lasing wavelength tunable by adding a tunable filter components, so tunable filter device is the key components in tunable fiber laser.At present, fiber laser wavelength is tuned by PZT, if thermal wavelength tuning is combined with PZT, a broader range of wavelength tuning is appearance . Erbium-doped fiber laser is used in the experiments,the main research is the physical characteristics of fiber grating temperature-dependent relationship and the fiber grating laser wavelength effects. It is found that the fiber laser wavelength changes continuously with temperature, tracking several temperature points observed the self-heterodyne spectrum and found that the changes in spectra of the 3dB bandwidth of less than 1kHz, and therefore the fiber laser with election-mode fiber Bragg grating shows excellent spectral properties and wavelength stability.

Chronic exposure of Sk-1 hairless mice to narrow-band ultraviolet A (320-355 nm)

International Nuclear Information System (INIS)

Menter, J.M.; Sayre, R.M.; Etemadi, A.A.; Agin, P.P.; Wills, I.

1996-01-01

Several recent investigations collectively suggest that the role of ultraviolet A (UVA) in chronic actinic skin damage may be greater than originally thought. In the present work, the output of a xenon-arc solar-simulator passed through a Bausch and Lomb monochromator in conjunction with a 2-mm Schott WG-320 filter produced narrow-band UVA centered at 338 nm, half-band width 24 nm, I 0 =3.4±0.3 mW/cm 2 . We chronically irradiated 10 SK-1 albino hairless mice 5 times per week for 18 weeks, starting with 1.25 J/cm 2 , for 33 irradiation days, sequentially followed by 1.50 J/cm 2 (34 days), 1.8 J/cm 2 (10 days), 2.0 J/cm 2 (22 days) to afford a total UVA dose of 154.3 J/cm 2 over 99 irradiation days. Erythema was noted clinically by day 6, which persisted throughout the irradiation. During the irradiation period, some scaling, consistent with mild epidermal hyperplasia was noted during irradiation days 37-56. This response later regressed despite continued chronic irradiation. Hematoxylin and eosin examination immediately after the final irradiation revealed a mild inflammatory response, with some dermal restructuring. At the end of the experiment, no significant signs of epidermal hyperplasia or (pre)malignant lesions were seen, although some stratum corneum thickening was noted. Marked dermal collagen damage and moderate elastosis was also evident. We believe that the observed differences in results reported in previous studies are in large part due to differences in light sources and irradiation protocols. (au)

Cascaded Mach-Zehnder wavelength filters in silicon photonics for low loss and flat pass-band WDM (de-)multiplexing.

Science.gov (United States)

Horst, Folkert; Green, William M J; Assefa, Solomon; Shank, Steven M; Vlasov, Yurii A; Offrein, Bert Jan

2013-05-20

We present 1-to-8 wavelength (de-)multiplexer devices based on a binary tree of cascaded Mach-Zehnder-like lattice filters, and manufactured using a 90 nm CMOS-integrated silicon photonics technology. We demonstrate that these devices combine a flat pass-band over more than 50% of the channel spacing with low insertion loss of less than 1.6 dB, and have a small device size of approximately 500 × 400 µm. This makes this type of filters well suited for application as WDM (de-)multiplexer in silicon photonics transceivers for optical data communication in large scale computer systems.

Three-Dimensional Simulation of DRIE Process Based on the Narrow Band Level Set and Monte Carlo Method

Directory of Open Access Journals (Sweden)

Jia-Cheng Yu

2018-02-01

Full Text Available A three-dimensional topography simulation of deep reactive ion etching (DRIE is developed based on the narrow band level set method for surface evolution and Monte Carlo method for flux distribution. The advanced level set method is implemented to simulate the time-related movements of etched surface. In the meanwhile, accelerated by ray tracing algorithm, the Monte Carlo method incorporates all dominant physical and chemical mechanisms such as ion-enhanced etching, ballistic transport, ion scattering, and sidewall passivation. The modified models of charged particles and neutral particles are epitomized to determine the contributions of etching rate. The effects such as scalloping effect and lag effect are investigated in simulations and experiments. Besides, the quantitative analyses are conducted to measure the simulation error. Finally, this simulator will be served as an accurate prediction tool for some MEMS fabrications.

Suppression of narrow-band interference in a PN spread-spectrum receiver using a CTD-based adaptive filter

Science.gov (United States)

Saulnier, G. J.; Das, P.; Milstein, L. B.

1984-11-01

Analytical results have shown that adaptive filtering can be a powerful tool for the rejection of narrow-band interference in a spread-spectrum receiver. However, the complexity of adaptive filtering hardware has hindered the experimental verification of these results. This paper describes a new adaptive filter architecture for implementing the Widrow-Hoff LMS algorithm while using only two multipliers regardless of filter order. This hardware simplification is achieved through the use of a burst processing technique. A 16-tap version of this adaptive filter constructed using charge-transfer devices (CTD's) is used to suppress a single tone jammer in a direct sequence spread-spectrum receiver. Probability of error measurements demonstrating the effectiveness of the adaptive filter for suppressing the single tone jammer along with simulation results for the optimal Weiner-Hopf filter are presented and discussed.

Application of an improved band-gap narrowing model to the numerical simulation of recombination properties of phosphorus-doped silicon emitters

Energy Technology Data Exchange (ETDEWEB)

Schumacher, J.O. [Fraunhofer Institute for Solar Energy Systems ISE, Oltmannsstr, 5, D-79100 Freiburg (Germany); Altermatt, P.P.; Heiser, G.; Aberle, A.G. [Photovoltaics Special Research Centre, University of NSW, 2052 Sydney (Australia)

2001-01-01

The commonly used band-gap narrowing (BGN) models for crystalline silicon do not describe heavily doped emitters with desirable precision. One of the reasons for this is that the applied BGN models were empirically derived from measurements assuming Boltzmann statistics. We apply a new BGN model derived by Schenk from quantum mechanical principles and demonstrate that carrier degeneracy and the new BGN model both substantially affect the electron-hole product within the emitter region. Simulated saturation current densities of heavily phosphorus-doped emitters, calculated with the new BGN model, are lower than results obtained with the widely used empirical BGN model of del Alamo.

Psoralen-mediated virus photoinactivation in platelet concentrates: enhanced specificity of virus kill in the absence of shorter UVA wavelengths

International Nuclear Information System (INIS)

Margolis-Nunno, Henrietta; Robinson, Richard; Horowitz, Bernard; Ben-Hur, Ehud; Geacintov, N.E.

1995-01-01

Treatments with psoralens and long-wavelength ultraviolet radiation (UVA, 320-400 nm; PUVA) have shown efficacy for virus sterilization of platelet concentrates (PC). We have employed the psoralen derivative 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT), and have found that platelet integrity is best preserved when rutin, a flavonoid that quenches multiple reactive oxygen species, is present during AMT/UVA treatment of PC. In this report, we examine the effects of different UVA spectra under our standard PC treatment conditions (i.e. 50 μg/mL AMT, 0.35 mM rutin and 38 J/cm 2 UVA). Added vesicular stomatitis virus (VSV; ≥ 5.5 log 10 ) was completely inactivated with the simultaneous maintenance of the platelet aggregation response (> 90% of control) when a UVA light source with transmission mainly between 360 and 370 nm (narrow UVA1) was used. In contrast, with a broad-band UVA (320-400 nm; broad UVA) light source, the aggregation response was greatly compromised (< 50% of control) with only a minor increase in the rate of VSV kill. With this lamp, platelet function could be improved to about 75% of the control by adding a long-pass filter, which reduced the transmission of shorter (≤ 345 nm) UVA wavelengths (340-400 nm; UVA1). At equivalent levels of virus kill, aggregation function was always best preserved when narrow UVA1 was used for PUVA treatment. Even in the absence of AMT, and with or without rutin present, narrow UVA1 irradiation was better tolerated by platelets than was broad UVA. (author)

Spectrally narrowed emissions in 2,5-bis(4-biphenylyl)thiophene crystals pumped by fs laser pulse

International Nuclear Information System (INIS)

Kobayashi, S.; Sasaki, F.; Yanagi, H.; Hotta, S.; Ichikawa, M.; Taniguchi, Y.

2005-01-01

Spectrally narrowed emission (SNE) in 2,5-bis(4-biphenylyl)thiophene (BP1T) crystals is investigated using fs laser pulse. Two different types of narrowing are observed at different vibronic emission bands with increasing pump intensities. Based on their pump intensity dependence and illumination area dependence, we assign the SNE at 20,200 cm -1 (β-band) to amplified spontaneous emission (ASE) and the SNE at 21,600 cm -1 (α-band) to superfluorescence rather than ASE

Acceptor-modulated optical enhancements and band-gap narrowing in ZnO thin films

Science.gov (United States)

Hassan, Ali; Jin, Yuhua; Irfan, Muhammad; Jiang, Yijian

2018-03-01

Fermi-Dirac distribution for doped semiconductors and Burstein-Moss effect have been correlated first time to figure out the conductivity type of ZnO. Hall Effect in the Van der Pauw configuration has been applied to reconcile our theoretical estimations which evince our assumption. Band-gap narrowing has been found in all p-type samples, whereas blue Burstein-Moss shift has been recorded in the n-type films. Atomic Force Microscopic (AFM) analysis shows that both p-type and n-type films have almost same granular-like structure with minor change in average grain size (˜ 6 nm to 10 nm) and surface roughness rms value 3 nm for thickness ˜315 nm which points that grain size and surface roughness did not play any significant role in order to modulate the conductivity type of ZnO. X-ray diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS) have been employed to perform the structural, chemical and elemental analysis. Hexagonal wurtzite structure has been observed in all samples. The introduction of nitrogen reduces the crystallinity of host lattice. 97% transmittance in the visible range with 1.4 × 107 Ω-1cm-1 optical conductivity have been detected. High absorption value in the ultra-violet (UV) region reveals that NZOs thin films can be used to fabricate next-generation high-performance UV detectors.

Acceptor-modulated optical enhancements and band-gap narrowing in ZnO thin films

Directory of Open Access Journals (Sweden)

Ali Hassan

2018-03-01

Full Text Available Fermi-Dirac distribution for doped semiconductors and Burstein-Moss effect have been correlated first time to figure out the conductivity type of ZnO. Hall Effect in the Van der Pauw configuration has been applied to reconcile our theoretical estimations which evince our assumption. Band-gap narrowing has been found in all p-type samples, whereas blue Burstein-Moss shift has been recorded in the n-type films. Atomic Force Microscopic (AFM analysis shows that both p-type and n-type films have almost same granular-like structure with minor change in average grain size (∼ 6 nm to 10 nm and surface roughness rms value 3 nm for thickness ∼315 nm which points that grain size and surface roughness did not play any significant role in order to modulate the conductivity type of ZnO. X-ray diffraction (XRD, Energy Dispersive X-ray Spectroscopy (EDS and X-ray Photoelectron Spectroscopy (XPS have been employed to perform the structural, chemical and elemental analysis. Hexagonal wurtzite structure has been observed in all samples. The introduction of nitrogen reduces the crystallinity of host lattice. 97% transmittance in the visible range with 1.4 × 107 Ω-1cm-1 optical conductivity have been detected. High absorption value in the ultra-violet (UV region reveals that NZOs thin films can be used to fabricate next-generation high-performance UV detectors.

Narrow line width operation of a 980 nm gain guided tapered diode laser bar

DEFF Research Database (Denmark)

Vijayakumar, Deepak; Jensen, Ole Bjarlin; Barrientos-Barria, Jessica

2011-01-01

We demonstrate two different schemes for the spectral narrowing of a 12 emitter 980 nm gain guided tapered diode laser bar. In the first scheme, a reflective grating has been used in a Littman Metcalf configuration and the wavelength of the laser emission could be narrowed down from more than 5.......5 nm in the free running mode to 0.04 nm (FWHM) at an operating current of 30 A with an output power of 8 W. The spectrum was found to be tunable within a range of 16 nm. In the second scheme, a volume Bragg grating has been used to narrow the wavelength of the laser bar from over 5 nm to less than 0.......2 nm with an output of 5 W at 20 A. To our knowledge, this is the first time spectral narrowing has been performed on a gain guided tapered diode laser bar. In the Littman Metcalf configuration, the spectral brightness has been increased by 86 times and in the volume Bragg grating cavity the spectral...

Strongly correlated impurity band superconductivity in diamond: X-ray spectroscopic evidence

Directory of Open Access Journals (Sweden)

G. Baskaran

2006-01-01

Full Text Available In a recent X-ray absorption study in boron doped diamond, Nakamura et al. have seen a well isolated narrow boron impurity band in non-superconducting samples and an additional narrow band at the chemical potential in a superconducting sample. We interpret the beautiful spectra as evidence for upper Hubbard band of a Mott insulating impurity band and an additional metallic 'mid-gap band' of a conducting 'self-doped' Mott insulator. This supports the basic framework of a recent theory of the present author of strongly correlated impurity band superconductivity (impurity band resonating valence bond, IBRVB theory in a template of a wide-gap insulator, with no direct involvement of valence band states.

Broadband transmission grating spectrometer for measuring the emission spectrum of EUV sources

NARCIS (Netherlands)

Bayraktar, Muharrem; Bastiaens, Hubertus M.J.; Bruineman, Caspar; Vratzov, Boris; Bijkerk, Frederik

2016-01-01

Extreme ultraviolet (EUV) light sources and their optimization for emission within a narrow wavelength band are essential in applications such as photolithography. Most light sources however also emit radiation outside this wavelength band and have a spectrum extending up to deep ultraviolet (DUV)

HIGH RESOLUTION He i 10830 Å NARROW-BAND IMAGING OF AN M-CLASS FLARE. I. ANALYSIS OF SUNSPOT DYNAMICS DURING FLARING

Energy Technology Data Exchange (ETDEWEB)

Wang, Ya; Su, Yingna; Hong, Zhenxiang; Ji, Haisheng [Key Laboratory of DMSA, Purple Mountain Observatory, CAS, Nanjing, 210008 (China); Zeng, Zhicheng; Goode, Philip R.; Cao, Wenda [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 (United States); Ji, Kaifan [Yunnan Astronomical Observatories, Kunming 650011 (China)

2016-12-20

In this paper, we report our first-step results of high resolution He i 10830 Å narrow-band imaging (bandpass: 0.5 Å) of an M1.8 class two-ribbon flare on 2012 July 5. The flare was observed with the 1.6 m aperture New Solar Telescope at Big Bear Solar Observatory. For this unique data set, sunspot dynamics during flaring were analyzed for the first time. By directly imaging the upper chromosphere, running penumbral waves are clearly seen as an outward extension of umbral flashes; both take the form of absorption in the 10830 Å narrow-band images. From a space–time image made of a slit cutting across a flare ribbon and the sunspot, we find that the dark lanes for umbral flashes and penumbral waves are obviously broadened after the flare. The most prominent feature is the sudden appearance of an oscillating absorption strip inside the ribbon when it sweeps into the sunspot’s penumbral and umbral regions. During each oscillation, outwardly propagating umbral flashes and subsequent penumbral waves rush out into the inwardly sweeping ribbon, followed by a return of the absorption strip with similar speed. We tentatively explain the phenomena as the result of a sudden increase in the density of ortho-helium atoms in the area of the sunspot being excited by the flare’s extreme ultraviolet illumination. This explanation is based on the observation that 10830 Å absorption around the sunspot area gets enhanced during the flare. Nevertheless, questions are still open and we need further well-devised observations to investigate the behavior of sunspot dynamics during flares.

Laterally Spreading Tumors of the Colon During High Resolution Colonoscopy with Narrow Band Imaging and Acetic Acid Chromoscopy

Directory of Open Access Journals (Sweden)

V.A. Yakovenko

2015-02-01

Materials and Methods. 1632 colonoscopy protocols were studied: 735 — by using video colonoscope Olympus CF-HQ190L and 897 — Olympus CF-150. Results and Discussion. In study group, adenoma detection rate was higher than in control one: 0.78 (571/735 vs. 0.47 (422/897, p < 0.00001; c2 = 157.9. Adenoma detection index was 3.6 times higher in study group than in control one: 2.9 (2,104/735 vs. 0.8 (708/897. Laterally spreading tumors were diagnosed 2.2 times more often in study group than in control one: 22 % (187/735 vs. 10 % (85/897, p < 0.00001; c2 = 53.6. Conclusions. High resolution colonoscopy with narrow band imaging and acetic acid chromoscopy has a high diagnostic value for detection of laterally spreading tumors of the colon.

Unidentified bands lambda lambda 6830, 7088 in symbiotic stars

Energy Technology Data Exchange (ETDEWEB)

Allen, D A [Anglo-Australian Observatory, Epping (Australia)

1980-01-01

About 60 stars are known which show broad emission bands centred at wavelengths of 6830 and 7088 A. The stars are all classified as symbiotic, since they combine high-excitation emission and M-type absorption spectra. From the behaviour of the bands in the evolution of slow novae as they approach the symbiotic phase, and from the occurrence of the bands in stars of different excitation, it is concluded that the ions responsible have ionization potentials near 100 eV. The similarity of behaviour and profile of the two suggests that both arise in the same species. No suitable identification appears possible at this time, because of the lack of data on highly ionized species. Arguments are presented which narrow the range of possibilities, the most notable argument being the absence of O VI emission. It is suggested that Fe VII or Fe VI may be responsible. In particular, it is recommended that transitions from the z/sup 3/P/sup 0/ and z/sup 1/F/sup 0/ levels of Fe VII be examined in detail. The differing, and time-varying profiles of the 6830 and 7088 bands in the stars observed are best explained in terms of velocity broadening. Velocities in excess of 1000 km s/sup -1/ are present. Rotation is a more credible form of the mass motion than expansion, because of the tendency to double profiles in these bands. If rotation is responsible, these velocities imply that the objects central to the emission nebulae are more compact than main sequence stars.

Narrow-band modulation of semiconductor lasers at millimeter wave frequencies (7100 GHz) by mode locking

International Nuclear Information System (INIS)

Lau, K.Y.

1990-01-01

This paper reports on the possibility of mode locking a semiconductor laser at millimeter wave frequencies approaching and beyond 100 GHz which was investigated theoretically and experimentally. It is found that there are no fundamental theoretical limitations in mode locking at frequencies below 100 GHz. AT these high frequencies, only a few modes are locked and the output usually takes the form of a deep sinusoidal modulation which is synchronized in phase with the externally applied modulation at the intermodal heat frequency. This can be regarded for practical purposes as a highly efficient means of directly modulating an optical carrier over a narrow band at millimeter wave frequencies. Both active and passive mode locking are theoretically possible. Experimentally, predictions on active mode locking have been verified in prior publications up to 40 GHz. For passive mode locking, evidence consistent with passive mode locking was observed in an inhomogeneously pumped GaAIAs laser at a frequency of approximately 70 GHz. A large differential gain-absorption ratio such as that present in an inhomogeneously pumped single quantum well laser is necessary for pushing the passive mode-locking frequency beyond 100 GHz

Laser linewidth narrowing using transient spectral hole burning

Energy Technology Data Exchange (ETDEWEB)

Thiel, Charles W.; Cone, Rufus L. [Department of Physics, Montana State University, Bozeman, MT 59715 (United States); Böttger, Thomas, E-mail: tbottger@usfca.edu [Department of Physics and Astronomy, 2130 Fulton Street, University of San Francisco, San Francisco, CA 94117 (United States)

2014-08-01

We demonstrate significant narrowing of laser linewidths by high optical density materials with inhomogeneously broadened absorption. As a laser propagates through the material, the nonlinear spectral hole burning process causes a progressive self-filtering of the laser spectrum, potentially reaching values less than the homogeneous linewidth. The transient spectral hole dynamically adjusts itself to the instantaneous frequency of the laser, passively suppressing laser phase noise and side modes over the entire material absorption bandwidth without the need for electronic or optical feedback to the laser. Wide bandwidth laser phase noise suppression was demonstrated using Er{sup 3+} doped Y{sub 2}SiO{sub 5} and LiNbO{sub 3} at 1.5 μm by employing time-delayed self-heterodyne detection of an external cavity diode laser to study the spectral narrowing effect. Our method is not restricted to any particular wavelength or laser system and is attractive for a range of applications where ultra-low phase noise sources are required. - Highlights: • We demonstrate significant laser linewidths narrowing by high optical density materials. • Nonlinear spectral hole burning causes progressive self-filtering of laser spectrum. • Filter dynamically adjusts itself to the instantaneous frequency of the laser. • Demonstrated at 1.5 μm in Er{sup 3+} doped Y{sub 2}SiO{sub 5} and LiNbO{sub 3}. • Linewidth filtering is not restricted to any particular wavelength or laser system.

Picosecond thermometer in the amide I band of myoglobin

DEFF Research Database (Denmark)

Austin, R.H.; Xie, A.; Meer, L. van der

2005-01-01

The amide I and II bands in myoglobin show a heterogeneous temperature dependence, with bands at 6.17 and 6.43 mu m which are more intense at low temperatures. The amide I band temperature dependence is on the long wavelength edge of the band, while the short wavelength side has almost...... can be used to determine the time it takes vibrational energy to flow into the hydration shell. We determine that vibrational energy flow to the hydration shell from the amide I takes approximately 20 ps to occur....

S – C – L triple wavelength superluminescent source based on an ultra-wideband SOA and FBGs

Energy Technology Data Exchange (ETDEWEB)

Ahmad, H; Zulkifli, M Z; Hassan, N A; Muhammad, F D; Harun, S W [Photonics Research Center (Department of Physics), University of Malaya, 50603 Kuala Lumpur (Malaysia)

2013-10-31

We propose and demonstrate a wide-band semiconductor optical amplifier (SOA) based triple-wavelength superluminescent source with the output in the S-, C- and L-band regions. The proposed systems uses an ultra-wideband SOA with an amplification range from 1440 to 1620 nm as the linear gain medium. Three fibre Bragg gratings (FBGs) with centre wavelengths of 1500, 1540 and 1580 nm are used to generate the lasing wavelengths in the S-, Cand L-bands respectively, while a variable optical attenuator is used to finely balance the optical powers of the lasing wavelengths. The ultra-wideband SOA generates an amplified spontaneous emission (ASE) spectrum with a peak power of -33 dBm at the highest SOA drive current, and also demonstrates a down-shift in the centre wavelength of the generated spectrum due to the spatial distribution of the carrier densities. The S-band wavelength is the dominant wavelength at high drive currents, with an output power of -6 dBm as compared to the C- and L-bands, which only have powers of -11 and -10 dBm, respectively. All wavelengths have a high average signal-to-noise ratio more than 60 dB at the highest drive current of 390 mA, and the system also shows a high degree of stability, with power fluctuations of less than 3 dB within 70 min. The proposed system can find many applications where a wide-band and stable laser source is crucial, such as in communications and sensing. (control of laser radiation parameters)

S – C – L triple wavelength superluminescent source based on an ultra-wideband SOA and FBGs

International Nuclear Information System (INIS)

Ahmad, H; Zulkifli, M Z; Hassan, N A; Muhammad, F D; Harun, S W

2013-01-01

We propose and demonstrate a wide-band semiconductor optical amplifier (SOA) based triple-wavelength superluminescent source with the output in the S-, C- and L-band regions. The proposed systems uses an ultra-wideband SOA with an amplification range from 1440 to 1620 nm as the linear gain medium. Three fibre Bragg gratings (FBGs) with centre wavelengths of 1500, 1540 and 1580 nm are used to generate the lasing wavelengths in the S-, Cand L-bands respectively, while a variable optical attenuator is used to finely balance the optical powers of the lasing wavelengths. The ultra-wideband SOA generates an amplified spontaneous emission (ASE) spectrum with a peak power of -33 dBm at the highest SOA drive current, and also demonstrates a down-shift in the centre wavelength of the generated spectrum due to the spatial distribution of the carrier densities. The S-band wavelength is the dominant wavelength at high drive currents, with an output power of -6 dBm as compared to the C- and L-bands, which only have powers of -11 and -10 dBm, respectively. All wavelengths have a high average signal-to-noise ratio more than 60 dB at the highest drive current of 390 mA, and the system also shows a high degree of stability, with power fluctuations of less than 3 dB within 70 min. The proposed system can find many applications where a wide-band and stable laser source is crucial, such as in communications and sensing. (control of laser radiation parameters)

Long-wavelength (red) light produces hyperopia in juvenile and adolescent tree shrews.

Science.gov (United States)

Gawne, Timothy J; Ward, Alexander H; Norton, Thomas T

2017-11-01

In infant tree shrews, exposure to narrow-band long-wavelength (red) light, that stimulates long-wavelength sensitive cones almost exclusively, slows axial elongation and produces hyperopia. We asked if red light produces hyperopia in juvenile and adolescent animals, ages when plus lenses are ineffective. Animals were raised in fluorescent colony lighting (100-300 lux) until they began 13days of red-light treatment at 11 (n=5, "infant"), 35 (n=5, "juvenile") or 95 (n=5, "adolescent") days of visual experience (DVE). LEDs provided 527-749 lux on the cage floor. To control for the higher red illuminance, a fluorescent control group (n=5) of juvenile (35 DVE) animals was exposed to ∼975 lux. Refractions were measured daily; ocular component dimensions at the start and end of treatment and end of recovery in colony lighting. These groups were compared with normals (n=7). In red light, the refractive state of both juvenile and adolescent animals became significantly (Prefractions (0.6±0.3D) were normal. In red-treated juveniles the vitreous chamber was significantly smaller than normal (Plight-induced slowed growth and hyperopia in juvenile and adolescent tree shrews demonstrates that the emmetropization mechanism is still capable of restraining eye growth at these ages. Copyright © 2017 Elsevier Ltd. All rights reserved.

High-frequency response and the possibilities of frequency-tunable narrow-band terahertz amplification in resonant tunneling nanostructures

International Nuclear Information System (INIS)

Kapaev, V. V.; Kopaev, Yu. V.; Savinov, S. A.; Murzin, V. N.

2013-01-01

The characteristics of the high-frequency response of single- and double-well resonant tunneling structures in a dc electric field are investigated on the basis of the numerical solution of a time-dependent Schrödinger equation with open boundary conditions. The frequency dependence of the real part of high frequency conductivity (high-frequency response) in In 0.53 Ga 0.47 As/AlAs/InP structures is analyzed in detail for various values of the dc voltage V dc in the negative differential resistance (NDR) region. It is shown that double-well three-barrier structures are promising for the design of terahertz-band oscillators. The presence of two resonant states with close energies in such structures leads to a resonant (in frequency) response whose frequency is determined by the energy difference between these levels and can be controlled by varying the parameters of the structure. It is shown that, in principle, such structures admit narrow-band amplification, tuning of the amplification frequency, and a fine control of the amplification (oscillation) frequency in a wide range of terahertz frequencies by varying a dc electric voltage applied to the structure. Starting from a certain width of the central intermediate barrier in double-well structures, one can observe a collapse of resonances, where the structure behaves like a single-well system. This phenomenon imposes a lower limit on the oscillation frequency in three-barrier resonant tunneling structures.

Junction-type photonic crystal waveguides for notch- and pass-band filtering

KAUST Repository

Shahid, Naeem

2011-01-01

Evolution of the mode gap and the associated transmission mini stop-band (MSB) as a function of photonic crystal (PhC) waveguide width is theoretically and experimentally investigated. The change of line-defect width is identified to be the most appropriate way since it offers a wide MSB wavelength tuning range. A high transmission narrow-band filter is experimentally demonstrated in a junction-type waveguide composed of two PhC waveguides with slightly different widths. The full width at half maximum is 5.6 nm; the peak transmission is attenuated by only ∼5 dB and is ∼20 dB above the MSBs. Additionally, temperature tuning of the filter were also performed. The results show red-shift of the transmission peak and the MSB edges with a gradient of dλ/dT = 0.1 nm/°C. It is proposed that the transmission MSBs in such junction-type cascaded PhC waveguides can be used to obtain different types of filters. © 2011 Optical Society of America.

Biexcitonic photocurrent induced by two-photon process at a telecommunication band

International Nuclear Information System (INIS)

Kodera, Tetsuo; Miyazawa, Toshiyuki; Kumagai, Naoto; Watanabe, Katsuyuki; Suzuki, Ayako; Takagi, Hiroyuki; Nakaoka, Toshihiro; Arakawa, Yasuhiko

2009-01-01

We report on photocurrent (PC) measurements of biexciton in a single self-assembled InAs quantum dot (QD) at a telecommunication wavelength of 1.3μm. We use shadow mask technique on an n-i Schottky photodiode structure with QDs to excite a single QD resonantly. Coherent pulse excitation is realized in two types of setups utilizing (i) an optical parametric oscillator and (ii) a stable semiconductor laser diode. In both setups we observe the biexcitonic PC peaks induced by a coherent two-photon process. Especially in the latter setups, the narrower pulse linewidth in energy provides a clearer biexcitonic PC peak because of reduced unwanted excitation. We estimate the binding energy ΔE B of our telecom-band biexciton to be 0.9 meV from the splitting between excitonic and biexcitonic resonances. The result suggests our telecom-band exciton-biexciton system is a good candidate for the building block of fiber-based controlled-rotation quantum logic operation. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Quantum Dot Detector Enhancement for Narrow Band Multispectral Applications

Science.gov (United States)

2013-12-01

22 Figure 22: (a) 4 Silver Nanospheres in Ring Formation; (b) Quality Factor for a 4 and 6 Nanosphere Ring Centered on...centered on. Here, the radius of the ring is varied from 60 to 400 nm. Figure 22:(a) 4 Silver Nanospheres in Ring Formation; (b) Quality Factor...QE )Iα at the resonant wavelength. From Figure 22 highest Q≈ 0.8 for the nanorings , but for there to be an increase in the I , Q must be greater

A novel facility for ageing materials with narrow-band ultraviolet radiation exposure

International Nuclear Information System (INIS)

Kaerhae, Petri; Ruokolainen, Kimmo; Heikkilae, Anu; Kaunismaa, Merja

2011-01-01

A facility for exploring wavelength dependencies in ultraviolet (UV) radiation induced degradation in materials has been designed and constructed. The device is essentially a spectrograph separating light from a lamp to spectrally resolved UV radiation. It is based on a 1 kW xenon lamp and a flat-field concave holographic grating 10 cm in diameter. Radiation at the wavelength range 250-500 nm is dispersed onto the sample plane of 1.5 cm in height and 21 cm in width. The optical performance of the device has been characterized by radiometric measurements. Using the facility, test samples prepared of regular newspaper have been irradiated from 1 to 8 h. Color changes on the different locations of the aged samples have been quantified by color measurements. Yellowness indices computed from the color measurements demonstrate the capability of the facility in revealing wavelength dependencies of the material property changes in reasonable time frames.

Endoscopic tri-modal imaging for detection of early neoplasia in Barrett's oesophagus: a multi-centre feasibility study using high-resolution endoscopy, autofluorescence imaging and narrow band imaging incorporated in one endoscopy system

NARCIS (Netherlands)

Curvers, W. L.; Singh, R.; Song, L.-M. Wong-Kee; Wolfsen, H. C.; Ragunath, K.; Wang, K.; Wallace, M. B.; Fockens, P.; Bergman, J. J. G. H. M.

2008-01-01

OBJECTIVE: To investigate the diagnostic potential of endoscopic tri-modal imaging and the relative contribution of each imaging modality (i.e. high-resolution endoscopy (HRE), autofluorescence imaging (AFI) and narrow-band imaging (NBI)) for the detection of early neoplasia in Barrett's oesophagus.

Design alternatives for wavelength routing networks

Science.gov (United States)

Miliotis, K.; Papadimitriou, G. I.; Pomportsis, A. S.

2003-03-01

This paper attempts to provide a high level overview of many of the technologies employed in optical networks with a focus on wavelength-routing networks. Optical networks involve a number of technologies from the physics of light through protocols and networks architectures. In fact there is so much technology and know-how that most people involved with optical networks only have a full understanding of the narrow area they deal with. We start first examining the principles that govern light and its use as a wave guide, and then turn our focus to the various components that constitute an optical network and conclude with the description of all optical networks and wavelength-routed networks in greater detail.

Wavelength dependence of interstellar polarization

International Nuclear Information System (INIS)

Mavko, G.E.

1974-01-01

The wavelength dependence of interstellar polarization was measured for twelve stars in three regions of the Milky Way. A 120A bandpass was used to measure the polarization at a maximum of sixteen wavelengths evenly spaced between 2.78μ -1 (3600A) and 1.28μ -1 (7800A). For such a wide wavelength range, the wavelength resolution is superior to that of any previously reported polarization measurements. The new scanning polarimeter built by W. A. Hiltner of the University of Michigan was used for the observations. Very broad structure was found in the wavelength dependence of the polarization. Extensive investigations were carried out to show that the structure was not caused by instrumental effects. The broad structure observed is shown to be in agreement with concurrent extinction measurements for the same stars. Also, the observed structure is of the type predicted when a homogeneous silicate grain model is fitted to the observed extinction. The results are in agreement with the hypothesis that the very broad band structure seen in the extinction is produced by the grains. (Diss. Abstr. Int., B)

Surface correlation effects in two-band strongly correlated slabs.

Science.gov (United States)

Esfahani, D Nasr; Covaci, L; Peeters, F M

2014-02-19

Using an extension of the Gutzwiller approximation for an inhomogeneous system, we study the two-band Hubbard model with unequal band widths for a slab geometry. The aim is to investigate the mutual effect of individual bands on the spatial distribution of quasi-particle weight and charge density, especially near the surface of the slab. The main effect of the difference in band width is the presence of two different length scales corresponding to the quasi-particle profile of each band. This is enhanced in the vicinity of the critical interaction of the narrow band where an orbitally selective Mott transition occurs and a surface dead layer forms for the narrow band. For the doped case, two different regimes of charge transfer between the surface and the bulk of the slab are revealed. The charge transfer from surface/center to center/surface depends on both the doping level and the average relative charge accumulated in each band. Such effects could also be of importance when describing the accumulation of charges at the interface between structures made of multi-band strongly correlated materials.

Absorptive reduction and width narrowing in λ-type atoms confined between two dielectric walls

International Nuclear Information System (INIS)

Li Yuanyuan; Hou Xun; Bai Jintao; Yan Junfeng; Gan Chenli; Zhang Yanpeng

2008-01-01

This paper investigates the absorptive reduction and the width narrowing of electromagnetically induced transparency (EIT) in a thin vapour film of λ-type atoms confined between two dielectric walls whose thickness is comparable with the wavelength of the probe field. The absorptive lines of the weak probe field exhibit strong reductions and very narrow EIT dips, which mainly results from the velocity slow-down effects and transient behaviour of atoms in a confined system. It is also shown that the lines are modified by the strength of the coupling field and the ratio of L/λ, with L the film thickness and λ the wavelength of the probe field. A simple robust recipe for EIT in a thin medium is achievable in experiment. (general)

Coded excitation and sub-band processing for blood velocity estmation in medical ultrasound

DEFF Research Database (Denmark)

Gran, Fredrik; Udesen, Jesper; Jensen, Jørgen Arendt

2007-01-01

This paper investigates the use of broadband coded excitation and subband processing for blood velocity estimation in medical ultrasound. In conventional blood velocity estimation a long (narrow-band) pulse is emitted and the blood velocity is estimated using an auto-correlation based approach....... However, the axial resolution of the narrow-band pulse is too poor for brightness-mode (B-mode) imaging. Therefore, a separate transmission sequence is used for updating the B-mode image, which lowers the overall frame-rate of the system. By using broad-band excitation signals, the backscattered received...... signal can be divided into a number of narrow frequency bands. The blood velocity can be estimated in each of the bands and the velocity estimates can be averaged to form an improved estimate. Furthermore, since the excitation signal is broadband, no secondary B-mode sequence is required, and the frame...

Design and implementation of a dual-wavelength intrinsic fluorescence camera system

Science.gov (United States)

Ortega-Martinez, Antonio; Musacchia, Joseph J.; Gutierrez-Herrera, Enoch; Wang, Ying; Franco, Walfre

2017-03-01

Intrinsic UV fluorescence imaging is a technique that permits the observation of spatial differences in emitted fluorescence. It relies on the fluorescence produced by the innate fluorophores in the sample, and thus can be used for marker-less in-vivo assessment of tissue. It has been studied as a tool for the study of the skin, specifically for the classification of lesions, the delimitation of lesion borders and the study of wound healing, among others. In its most basic setup, a sample is excited with a narrow-band UV light source and the resulting fluorescence is imaged with a UV sensitive camera filtered to the emission wavelength of interest. By carefully selecting the excitation/emission pair, we can observe changes in fluorescence associated with physiological processes. One of the main drawbacks of this simple setup is the inability to observe more than a single excitation/emission pair at the same time, as some phenomena are better studied when two or more different pairs are studied simultaneously. In this work, we describe the design and the hardware and software implementation of a dual wavelength portable UV fluorescence imaging system. Its main components are an UV camera, a dual wavelength UV LED illuminator (295 and 345 nm) and two different emission filters (345 and 390 nm) that can be swapped by a mechanical filter wheel. The system is operated using a laptop computer and custom software that performs basic pre-processing to improve the image. The system was designed to allow us to image fluorescent peaks of tryptophan and collagen cross links in order to study wound healing progression.

Characterization of FBG sensor interrogation based on a FDML wavelength swept laser

Science.gov (United States)

Jung, Eun Joo; Kim, Chang-Seok; Jeong, Myung Yung; Kim, Moon Ki; Jeon, Min Yong; Jung, Woonggyu; Chen, Zhongping

2012-01-01

In this study, we develop an ultra-fast fiber Bragg grating sensor system that is based on the Fourier domain mode-locked (FDML) swept laser. A FDML wavelength swept laser has many advantages compared to the conventional wavelength swept laser source, such as high-speed interrogation, narrow spectral sensitivity, and high phase stability. The newly developed FDML wavelength swept laser shows a superior performance of a high scan rate of 31.3 kHz and a broad scan range of over 70 nm simultaneously. The performance of the grating sensor interrogating system using a FDML wavelength swept laser is characterized in both static and dynamic strain responses. PMID:18852764

SDSS J211852.96-073227.5: a new γ-ray flaring narrow-line Seyfert 1 galaxy

Science.gov (United States)

Yang, Hui; Yuan, Weimin; Yao, Su; Li, Ye; Zhang, Jin; Zhou, Hongyan; Komossa, S.; Liu, He-Yang; Jin, Chichuan

2018-04-01

We report on the identification of a new γ-ray-emitting narrow-line Seyfert 1 (NLS1) galaxy, SDSS J211852.96-073227.5 (hereafter J2118-0732). The galaxy, at a redshift of 0.26, is associated with a radio source of flat/inverted spectrum at high radio frequencies. The analysis of its optical spectrum obtained in the Sloan Digital Sky Survey revealed a small linewidth of the broad component of the Hβ line (FWHM = 1585 km s-1), making it a radio-loud NLS1 galaxy - an intriguing class of active galactic nuclei with exceptional multi-wavelength properties. A new γ-ray source centred at J2118-0732 was sporadically detected during 2009-2013 in form of flares by the Fermi-LAT. Our XMM-Newton observations revealed a flat X-ray spectrum described by a simple power law, and a flux variation by a factor of ˜2.5 in 5 months. The source also shows intraday variability in the infrared band. Its broad-band spectral energy distribution can be modelled by emission from a simple one-zone leptonic jet model, and the flux drop from infrared to X-rays in five months can be explained by changes of the jet parameters, though the exact values may be subject to relatively large uncertainties. With the NLS1-blazar composite nucleus, the clear detection of the host galaxy and the synchronous variations in the multi-wavelength fluxes, J2118-0732 provides a new perspective on the formation and evolution of relativistic jets under the regime of relatively small black hole masses and high accretion rates.

Efektivitas Terapi Kortikosteroid Intranasal pada Hipertrofi Adenoid Usia Dewasa berdasarkan Pemeriksaan Narrow Band Imaging

Directory of Open Access Journals (Sweden)

Sinta Sari Ratunanda

2016-12-01

Full Text Available Adenoid hypertrophy is a process in which adenoid size becomes enlarged and causes clinical symptoms, especially nasal obstruction. Adenoid hypertrophy can be due to physiological, inflammatory, or malignancy processes. Adenoid inflammatory process can be assessed using a flexible fiberoptic nasoendoscopy with narrow band imaging (NBI. Intranasal corticosteroid is one of the choices to treat adenoid hypertrophy in children; however, more experiments are needed to use it in adults. This study was performed in the period of November 2012 to January 2013 at the outpatient clinic of the Otorhinolaryngology-Head and Neck Surgery Department of Dr. Hasan Sadikin General Hospital Bandung, using pre- and post-test open-labeled quasiexperimental design. Sample was selected through consecutive sampling, involving 11 subjects. Diagnosis was based on research subject’s anamnesis, ear nose and throat (ENT physical examination, NBI-equipped fiberoptic nasoendocopy examination, and adenoid mucosal biopsy. Subjects were given intranasal corticosteroid therapy for four weeks. NBI-equipped fiberoptic nasoendocopy examination and biopsy examination were performed after therapy. Data were analyzed using Wilcoxon test, showing significant improvement of the adenoid inflammation after intranasal corticosteroids therapy (p<0.05. McNemar test results showed a significant reduction in adenoid size (p<0.05. Spearman rank test showed a significant correlation between histopathologic findings and NBI examination result (p<0.05. In conclusion, intranasal corticosteroids are effective for adult adenoid hypertrophy treatment based on NBI examination. [MKB. 2016;48(4:228–33

Design of multi-wavelength tunable filter based on Lithium Niobate

Science.gov (United States)

Zhang, Ailing; Yao, Yuan; Zhang, Yue; Song, Hongyun

2018-05-01

A multi-wavelength tunable filter is designed. It consists of multiple waveguides among multiple waveguide gratings. A pair of electrodes were placed on both sides of each waveguide. The tunable filter uses the electro-optic effect of Lithium Niobate to tune the phase caused by each waveguide. Consequently, the wavelength and wavelength spacing of the filter are tuned by changing external voltages added on the electrode pairs. The tunable property of the filter is analyzed by phase matching condition and transfer-matrix method. Numerical results show that not only multiple wavelengths with narrow bandwidth are tuned with nearly equal spacing by synchronously changing the voltages added on all electrode pairs, but also the number of wavelengths is determined by the number of phase shifts caused by electrode pairs. Furthermore, due to the electro-optic effect of Lithium Niobate, the tuning speed of the filter can reach the order of ns.

Lunar Noise-Temperature Increase Measurements at S-Band, X-Band, and Ka-Band Using a 34-Meter-Diameter Beam-Waveguide Antenna

Science.gov (United States)

Morabito, D. D.

2006-08-01

The Moon radiates energy at infrared and microwave wavelengths, in addition to reflecting sunlight at optical wavelengths. As a result, an antenna pointed at or near the Moon will cause an increase in receiver noise temperature that needs to be accounted for in telemetry, radio science, or ranging link budgets. The Deep Space Network may be required to use its antennas in future lunar robotic or human missions, and thus it is important to understand the nature of this temperature increase as a function of observing frequency, lunar phase, and angular offset of the antenna beam from the center of the lunar disk. This article quantifies such a set of measurements acquired at DSS 13, a 34-m-diameter research and development beam-waveguide antenna located at Goldstone, California, at three different telecommunication frequencies, S-band (2.3 GHz), X-band (8.4 GHz), and Ka-band (32 GHz), over a wide range of lunar phase, for both disk-centered and limb-centered positions of the antenna beam.

A Compact Band-Pass Filter with High Selectivity and Second Harmonic Suppression.

Science.gov (United States)

Hadarig, Ramona Cosmina; de Cos Gomez, Maria Elena; Las-Heras, Fernando

2013-12-03

The design of a novel band-pass filter with narrow-band features based on an electromagnetic resonator at 6.4 GHz is presented. A prototype is manufactured and characterized in terms of transmission and reflection coefficient. The selective passband and suppression of the second harmonic make the filter suitable to be used in a C band frequency range for radar systems and satellite/terrestrial applications. To avoid substantial interference for this kind of applications, passive components with narrow band features and small dimensions are required. Between 3.6 GHz and 4.2 GHz the band-pass filter with harmonic suppression should have an attenuation of at least 35 dB, whereas for a passband, less than 10% is sufficient.

Fabrication of dense wavelength division multiplexing filters with large useful area

Science.gov (United States)

Lee, Cheng-Chung; Chen, Sheng-Hui; Hsu, Jin-Cherng; Kuo, Chien-Cheng

2006-08-01

Dense Wavelength Division Multiplexers (DWDM), a kind of narrow band-pass filter, are extremely sensitive to the optical thickness error in each composite layer. Therefore to have a large useful coating area is extreme difficult because of the uniformity problem. To enlarge the useful coating area it is necessary to improve their design and their fabrication. In this study, we discuss how the tooling factors at different positions and for different materials are related to the optical performance of the design. 100GHz DWDM filters were fabricated by E-gun evaporation with ion-assisted deposition (IAD). To improve the coating uniformity, an analysis technique called shaping tooling factor (STF) was used to analyze the deviation of the optical thickness in different materials so as to enlarge the useful coating area. Also a technique of etching the deposited layers with oxygen ions was introduced. When the above techniques were applied in the fabrication of 100 GHz DWDM filters, the uniformity was better than +/-0.002% over an area of 72 mm in diameter and better than +/-0.0006% over 20mm in diameter.

OLGA- and OLGIM-based staging of gastritis using narrow-band imaging magnifying endoscopy.

Science.gov (United States)

Saka, Akiko; Yagi, Kazuyoshi; Nimura, Satoshi

2015-11-01

As atrophic gastritis and intestinal metaplasia as a result of Helicobacter pylori are considered risk factors for gastric cancer, it is important to assess their severity. In the West, the operative link for gastritis assessment (OLGA) and operative link for gastric intestinal metaplasia assessment (OLGIM) staging systems based on biopsy have been widely adopted. In Japan, however, narrow-band imaging (NBI)-magnifying endoscopic diagnosis of gastric mucosal inflammation, atrophy, and intestinal metaplasia has been reported to be fairly accurate. Therefore, we investigated the practicality of NBI-magnifying endoscopy (NBI-ME) for gastritis staging. We enrolled 55 patients, in whom NBI-ME was used to score the lesser curvature of the antrum (antrum) and the lesser curvature of the lower body (corpus). The NBI-ME score classification was established from images obtained beforehand, and then biopsy specimens taken from the observed areas were scored according to histological findings. The NBI-ME and histology scores were then compared. Furthermore, we assessed the NBI-ME and histology stages using a combination of scores for the antrum and corpus, and divided the stages into two risk groups: low and high. The degree to which the stage assessed by NBI-ME approximated that assessed by histology was then ascertained. Degree of correspondence between the NBI-ME and histology scores was 69.1% for the antrum and 72.7% for the corpus, and that between the high- and low-risk groups was 89.1%. Staging of gastritis using NBI-ME approximates that based on histology, and would be a practical alternative to the latter. © 2015 The Authors. Digestive Endoscopy © 2015 Japan Gastroenterological Endoscopy Society.

Wavelength-tunable prism-coupled external cavity passively mode-locked quantum-dot laser

International Nuclear Information System (INIS)

Wu Yan-Hua; Jian Wu; Jin Peng; Wang Fei-Fei; Hu Fa-Jie; Wei Heng; Wang Zhan-Guo

2015-01-01

A wavelength-tunable mode-locked quantum dot laser using an InAs/GaAs quantum-dot gain medium and a discrete semiconductor saturable absorber mirror is demonstrated. A dispersion prism, which has lower optical loss and less spectral narrowing than a blazed grating, is used for wavelength selection and tuning. A wavelength tuning range of 45.5 nm (from 1137.3 nm to 1182.8 nm) under 140-mA injection current in the passive mode-locked regime is achieved. The maximum average power of 19 mW is obtained at the 1170.3-nm wavelength, corresponding to the single pulse energy of 36.5 pJ. (paper)

Active Multispectral Band Selection and Reflectance Measurement System

National Research Council Canada - National Science Library

Rennich, Bradley

1999-01-01

.... To aid in the selection of these bands, a novel multispectral band selection technique is presented based on the cross-correlation of the material class reflectance spectra over a wavelength range of 1 - 5 microns...

Energy correlations for mixed rotational bands

International Nuclear Information System (INIS)

Doessing, T.

1985-01-01

A schematic model for the mixing of rotational bands above the yrast line in well deformed nuclei is considered. Many-particle configurations of a rotating mean field form basis bands, and these are subsequently mixed due to a two body residual interaction. The energy interval over which a basis band is spread out increases with increasing excitation energy above the yrast line. Conversely, the B(E2) matrix element for rotational decay out of one of the mixed band states is spread over an interval which is predicted to become more narrow with increasing excitation energy. Finally, the implication of band mixing for γ-ray energy correlations is briefly discussed. (orig.)

Valuing spectrum at mm wavelengths for cellular networks

OpenAIRE

Shaw, B. A.; Beltrán, H. F.; Sowerby, K. W.

2017-01-01

This paper investigates the economic value of spectrum at mm wavelengths. The analysis uses four techniques to value spectrum, namely a benchmarking comparison, a discounted cash flow analysis, a real options approach and a deprival method. The methods to calculate spectrum value presented in this paper can be used for any spectrum band and in any country. However, to determine the value of mm wavelengths for cellular networks, we have used data from New Zealand, specifically for the existing...

Narrow in-gap states in doped Al2O3

KAUST Repository

Casas-Cabanas, Montse; Fré sard, Marion; Lü ders, Ulrike; Fré sard, Raymond; Schuster, Cosima B.; Schwingenschlö gl, Udo

2011-01-01

Based on XRD data testifying that the M ions occupy substitutional sites, transmittance measurement are discussed in comparison to electronic structure calculations for M-doped Al2O3 with M = V, Mn, and Cr. The M 3d states are found approximatively 2 eV above the top of the host valence band. The fundamental band gap of Al2O3 is further reduced in the V and Mn cases due to a splitting of the narrow band at the Fermi energy. Nevertheless the measured transmittance in the visible range remains high in all three cases. © 2011 Elsevier B.V. All rights reserved.

Narrow in-gap states in doped Al2O3

KAUST Repository

Casas-Cabanas, Montse

2011-10-01

Based on XRD data testifying that the M ions occupy substitutional sites, transmittance measurement are discussed in comparison to electronic structure calculations for M-doped Al2O3 with M = V, Mn, and Cr. The M 3d states are found approximatively 2 eV above the top of the host valence band. The fundamental band gap of Al2O3 is further reduced in the V and Mn cases due to a splitting of the narrow band at the Fermi energy. Nevertheless the measured transmittance in the visible range remains high in all three cases. © 2011 Elsevier B.V. All rights reserved.

Monolithic all-PM femtosecond Yb-fiber laser stabilized with a narrow-band fiber Bragg grating and pulse-compressed in a hollow-core photonic crystal fiber

DEFF Research Database (Denmark)

Turchinovich, Dmitry; Liu, Xiaomin; Lægsgaard, Jesper

2008-01-01

. The laser output is compressed in a spliced-on hollow-core PM photonic crystal fiber, thus providing direct end-of-the-fiber delivery of pulses of around 370 fs duration and 4 nJ energy with high mode quality. Tuning the pump power of the end amplifier of the laser allows for the control of output pulse......We report on an environmentally stable self-starting monolithic (i.e. without any free-space coupling) all-polarization-maintaining (PM) femtosecond Yb-fiber laser, stabilized against Q-switching by a narrow-band fiber Bragg grating and modelocked using a semiconductor saturable absorber mirror...

Characterisation results of the CMOS VISNIR spectral band detector for the METimage instrument

Science.gov (United States)

Pratlong, Jérôme; Schmuelling, Frank; Benitez, Victor; Breart De Boisanger, Michel; Skegg, Michael; Simpson, Robert; Bowring, Steve; Krzizok, Natalie

2017-09-01

The METimage instrument is part of the EPS-SG (EUMETSAT Polar System Second Generation) program. It will be situated on the MetOp-SG platform which in operation has an objective of collecting data for meteorology and climate monitoring as well as their forecasting. Teledyne e2v has developed and characterised the CMOS VISNIR detector flight module part of the METimage instrument. This paper will focus on the silicon results obtained from the CMOS VISNIR detector flight model. The detector is a large multi-linear device composed of 7 spectral bands covering a wavelength range from 428 nm to 923 nm (some bands are placed twice and added together to enhance the signal-to-noise performance). This detector uses a 4T pixel, with a size of 250μm square, presenting challenges to achieve good charge transfer efficiency with high conversion factor and good linearity for signal levels up to 2M electrons and with high line rates. Low noise has been achieved using correlated double sampling to suppress the read-out noise and give a maximum dynamic range that is significantly larger than in standard commercial devices. The photodiode occupies a significant fraction of the large pixel area. This makes it possible to meet the detection efficiency when front illuminated. A thicker than standard epitaxial silicon is used to improve NIR response. However, the dielectric stack on top of the sensor produces Fabry-Perot étalon effects, which are problematic for narrow band illumination as this causes the detection efficiency to vary significantly over a small wavelength range. In order to reduce this effect and to meet the specification, the silicon manufacturing process has been modified. The flight model will have black coating deposited between each spectral channel, onto the active silicon regions.

Detection of Mucosal Recurrent Nasopharyngeal Carcinomas After Radiotherapy With Narrow-Band Imaging Endoscopy

International Nuclear Information System (INIS)

Wang, Wen-Hung; Lin, Yen-Chun; Chen, Wen-Cheng; Chen, Miao-Fen; Chen, Chih-Cheng; Lee, Kam-Fai

2012-01-01

Purpose: This study evaluated the feasibility of screening mucosal recurrent nasopharyngeal carcinoma with narrow-band imaging (NBI) endoscopy. Methods and Materials: One hundred and six patients were enrolled. All patients underwent conventional white-light (WL) endoscopic examination of the nasopharynx followed by NBI endoscopy. Biopsies were performed if recurrence was suspected. Results: We identified 32 suspected lesions by endoscopy in WL and/or NBI mode. Scattered brown spots (BS) were identified in 22 patients, and 4 of the 22 who had negative MRI findings were histopathologically confirmed to be neoplasias that were successfully removed via endoscopy. A comparison of the visualization in NBI closer view corresponded to histopathological findings in 22 BS, and the prevalence rates of neoplasias in tail signs, round signs, and irregularities signs were 0% (0/6), 0% (0/7), and 44.4% (4/9), respectively (p = 0.048). The sensitivity, specificity, and diagnostic capability were 37.5%, 92.9% and 0.652 for WL, 87.5%, 74.5% and 0.810 for NBI, and 87.5%, 87.8%, and 0.876 for NBI closer view, respectively. NBI closer view was effective in increasing specificity compared with NBI alone (87.8% vs. 74.5%, p < 0.05), and in increasing sensitivity and diagnostic capability compared to WL alone (87.5% vs. 37.5%, p < 0.05; 0.876 vs. 0.652, p = 0.0001). Conclusions: Although NBI in endoscopy can improve sensitivity of mucosal recurrent nasopharyngeal neoplasias, false-positive (nonneoplasia BS) results may be obtained in areas with nonspecific inflammatory changes due to postradiation effects. NBI closer view not only can offer a timely, convenient, and highly reliable assessment of mucosal recurrent nasopharyngeal carcinoma, it can also make endoscopic removal possible.

Diode-pumped Alexandrite laser with passive SESAM Q-switching and wavelength tunability

Science.gov (United States)

Parali, Ufuk; Sheng, Xin; Minassian, Ara; Tawy, Goronwy; Sathian, Juna; Thomas, Gabrielle M.; Damzen, Michael J.

2018-03-01

We report the first experimental demonstration of a wavelength tunable passively Q-switched red-diode-end pumped Alexandrite laser using a semiconductor saturable absorber mirror (SESAM). We present the results of the study of passive SESAM Q-switching and wavelength-tuning in continuous diode-pumped Alexandrite lasers in both linear cavity and X-cavity configurations. In the linear cavity configuration, pulsed operation up to 27 kHz repetition rate in fundamental TEM00 mode was achieved and maximum average power was 41 mW. The shortest pulse generated was 550 ns (FWHM) and the Q-switched wavelength tuning band spanned was between 740 nm and 755 nm. In the X-cavity configuration, a higher average power up to 73 mW, and obtained with higher pulse energy 6 . 5 μJ at 11.2 kHz repetition rate, in fundamental TEM00 mode with excellent spatial quality M2 < 1 . 1. The Q-switched wavelength tuning band spanned was between 775 nm and 781 nm.

A dual-polarized broadband planar antenna and channelizing filter bank for millimeter wavelengths

Science.gov (United States)

O'Brient, Roger; Ade, Peter; Arnold, Kam; Edwards, Jennifer; Engargiola, Greg; Holzapfel, William L.; Lee, Adrian T.; Myers, Michael J.; Quealy, Erin; Rebeiz, Gabriel; Richards, Paul; Suzuki, Aritoki

2013-02-01

We describe the design, fabrication, and testing of a broadband log-periodic antenna coupled to multiple cryogenic bolometers. This detector architecture, optimized here for astrophysical observations, simultaneously receives two linear polarizations with two octaves of bandwidth at millimeter wavelengths. The broad bandwidth signal received by the antenna is divided into sub-bands with integrated in-line frequency-selective filters. We demonstrate two such filter banks: a diplexer with two sub-bands and a log-periodic channelizer with seven contiguous sub-bands. These detectors have receiver efficiencies of 20%-40% and percent level polarization isolation. Superconducting transition-edge sensor bolometers detect the power in each sub-band and polarization. We demonstrate circularly symmetric beam patterns, high polarization isolation, accurately positioned bands, and high optical efficiency. The pixel design is applicable to astronomical observations of intensity and polarization at millimeter through sub-millimeter wavelengths. As compared with an imaging array of pixels measuring only one band, simultaneous measurements of multiple bands in each pixel has the potential to result in a higher signal-to-noise measurement while also providing spectral information. This development facilitates compact systems with high mapping speeds for observations that require information in multiple frequency bands.

Organic wavelength selective mirrors for luminescent solar concentrators

NARCIS (Netherlands)

Verbunt, P.P.C.; Debije, M.G.; Broer, D.J.; Bastiaansen, C.W.M.; Boer, de D.K.G.; Wehrspohn, R.; Gombert, A.

2012-01-01

Organic polymeric chiral nematic liquid crystalline (cholesteric) wavelength selective mirrors can increase the efficiency of luminescent solar concentrators (LSCs) when they are illuminated with direct sunlight normal to the device. However, due to the angular dependence of the reflection band, at

Reliable Operation for 14500 h of a Wavelength-Stabilized Diode Laser System on a Microoptical Bench at 671 nm

DEFF Research Database (Denmark)

Sumpf, Bernd; Maiwald, Martin; Müller, André

2012-01-01

Reliability tests for wavelength-stabilized compact diode laser systems emitting at 671 nm are presented. The devices were mounted on microoptical benches with the dimensions of 13 mm $\\times\\,$4 mm. Reflecting Bragg gratings were used for wavelength stabilization and emission width narrowing...

Gas Distributions in Comet ISON’s Coma: Concurrent Integral-Field Spectroscopy and Narrow-band Imaging.

Science.gov (United States)

Schmidt, Carl; Johnson, Robert E.; Baumgardner, Jeffrey; Mendillo, Michael

2014-11-01

At a solar distance of 0.44 AU, Oort cloud comet C/2012 S1 (ISON) exhibited an outburst phase that was observed by small telescopes at the McDonald Observatory. In conjunction with narrow-band (14Å) imaging over a wide-field, an image-slicer spectrograph ( 20,000) simultaneously measured the spatial distribution of ISON’s coma over a 1.6 x 2.7 arcminute field made up of 246 individual spectra. More than fifty emission lines from C2, NH2, CO, H2O+ and Na were observed within a single Echelle order spanning 5868Å to 5930Å. Spatial reconstructions of these species reveal that ISON’s coma was quite elongated several thousand km along the axis perpendicular to its motion. The ion tail appeared distinctly broader than the neutral Na tail, providing strong evidence that Na in the coma did not originate by dissociative recombination of a sodium bearing molecular ion. Production rates increased from 1.6 ± 0.3 x 1023 to 5.8 ± 1 x 1023 Na atoms/s within 24 hours, outgassing much less than comparable comets relative to ISON’s water production. The anti-sunward Na tail was imaged >106 km from the nucleus. Its distribution indicates origins both near the nucleus and in the dust tail, with the ratio of these Na sources varying on hourly timescales due to outburst activity.

"Leopard skin sign": the use of narrow-band imaging with magnification endoscopy in celiac disease.

Science.gov (United States)

Tchekmedyian, Asadur J; Coronel, Emmanuel; Czul, Frank

2014-01-01

Celiac Disease (CD) is an immune reaction to gluten containing foods such as rye, wheat and barley. This condition affects individuals with a genetic predisposition; it targets the small bowel and may cause symptoms including diarrhea, malabsorption, weight loss, abdominal pain and bloating. The diagnosis is made by serologic testing of celiac-specific antibodies and confirmed by histology. Certain endoscopic characteristics, such as scalloping, reduction in the number of folds, mosaic-pattern mucosa or nodular mucosa, are suggestive of CD and can be visualized under white light endoscopy. Due to its low sensitivity, endoscopy alone is not recommended to diagnose CD; however, enhanced visual identification of suspected mucosal abnormalities through the use of new technologies, such as narrow band imaging with magnification (NBI-ME), could assist in targeting biopsies and thereby increasing the sensitivity of endoscopy. This is a case series of seven patients with serologic and histologic diagnoses of CD who underwent upper endoscopies with NBI-ME imaging technology as part of their CD evaluation. By employing this imaging technology, we could identify patchy atrophy sites in a mosaic pattern, with flattened villi and alteration of the central capillaries of the duodenal mucosa. We refer to this epithelial pattern as "Leopard Skin Sign". Since epithelial lesions are easily seen using NBI-ME, we found it beneficial for identifying and targeting biopsy sites. Larger prospective studies are warranted to confirm our findings.

Wavelength stabilized multi-kW diode laser systems

Science.gov (United States)

Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens

2015-03-01

We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.

Wavelength dependence of superhumps in VW Hyi

International Nuclear Information System (INIS)

Amerongen, S. van; Bovenschen, H.; Paradijs, J. van

1987-01-01

Results are presented of five-colour photometric observations of the SU UMa system VW Hyi, made on six nights during the November 1984 superoutburst. The light curve is dominated by superhump variations, whose amplitude in all passbands decreases with time (in the V-band from 0.16 mag about 4.5 day after the superoutburst reached maximum brightness, to 0.10 mag about 5 day later). The superhump light curve depends strongly on wavelength. In particular it appears that the light curves in different passbands are mutually shifted: the larger the wavelength, the more the light curve is delayed. (author)

Colour evaluation in scars: tristimulus colorimeter, narrow-band simple reflectance meter or subjective evaluation?

Science.gov (United States)

Draaijers, Lieneke J; Tempelman, Fenike R H; Botman, Yvonne A M; Kreis, Robert W; Middelkoop, Esther; van Zuijlen, Paul P M

2004-03-01

The evaluation of scar colour is, at present, usually limited to an assessment according to a scar assessment scale. Although useful, these assessment scales only evaluate subjectively the degree of scar colour. In this study, the reliability of the subjective assessment of scar colour by observers is compared to the reliability of the measurements of two objective colour measurement instruments. Four independent observers subjectively assessed the vascularisation and pigmentation of 49 scar areas in 20 patients. The degree of vascularisation and pigmentation was scored according to a scale ranging from '1', when it appeared to be like healthy skin, to '10', which corresponds to the worst imaginable outcome of vascularisation or pigmentation. The observers also scored the pigmentation categories of the scar (hypopigmention, hyperpigmention or mixed pigmentation). Finally, each observer measured the scar areas with a tristimulus colorimeter (Minolta Chromameter) and a narrow-band simple reflectance meter (DermaSpectrometer). A single observer could reliably carry out measurements of the DermaSpectrometer and the Minolta Chromameter for the evaluation of scar colour (r = 0.72). The vascularisation of scars could also be assessed reliably with a single observer (r = 0.76) whereas for a reliable assessment of pigmentation at least three observers were necessary (r > or = 0.77). The agreement between the observers for the pigmentation categories also turned out to be unacceptably low (k = 0.349). This study shows that an overall evaluation of scar colour with the DermaSpectrometer and the Minolta Chromameter is more reliable than the evaluation of scar colour with observers. Of both instruments for measuring scar colour, we prefer, because of its feasibility, the DermaSpectrometer.

Use of a reflective semiconductor optical amplifier and dual-ring architecture design to produce a stable multi-wavelength fiber laser

International Nuclear Information System (INIS)

Yeh, Chien-Hung; Chow, Chi-Wai; Lu, Shao-Sheng

2014-01-01

In this work, we propose and demonstrate a multi-wavelength laser source produced by utilizing a C-band reflective semiconductor optical amplifier (RSOA) with a dual-ring fiber cavity. Here, the laser cavity consists of an RSOA, a 1 × 2 optical coupler, a 2 × 2 optical coupler and a polarization controller. As a result, thirteen to eighteen wavelengths around the L band could be generated simultaneously when the bias current of the C-band RSOA was driven at 30–70 mA. In addition, the output stabilities of the power and wavelength are also discussed. (paper)

Use of a reflective semiconductor optical amplifier and dual-ring architecture design to produce a stable multi-wavelength fiber laser

Science.gov (United States)

Yeh, Chien-Hung; Chow, Chi-Wai; Lu, Shao-Sheng

2014-05-01

In this work, we propose and demonstrate a multi-wavelength laser source produced by utilizing a C-band reflective semiconductor optical amplifier (RSOA) with a dual-ring fiber cavity. Here, the laser cavity consists of an RSOA, a 1 × 2 optical coupler, a 2 × 2 optical coupler and a polarization controller. As a result, thirteen to eighteen wavelengths around the L band could be generated simultaneously when the bias current of the C-band RSOA was driven at 30-70 mA. In addition, the output stabilities of the power and wavelength are also discussed.

Estimation of photonic band gap in the hollow core cylindrical multilayer structure

Science.gov (United States)

Chourasia, Ritesh Kumar; Singh, Vivek

2018-04-01

The propagation characteristic of two hollow core cylindrical multilayer structures having high and low refractive index contrast of cladding regions have been studied and compared at two design wavelengths i.e. 1550 nm and 632.8 nm. With the help of transfer matrix method a relation between the incoming light wave and outgoing light wave has been developed using the boundary matching technique. In high refractive index contrast, small numbers of layers are sufficient to provide perfect band gap in both design wavelengths. The spectral position and width of band gap is highly depending on the optical path of incident light in all considered cases. For sensing application, the sensitivity of waveguide can be obtained either by monitoring the width of photonic band gap or by monitoring the spectral shift of photonic band gap. Change in the width of photonic band gap with the core refractive index is larger in high refractive index contrast of cladding materials. However, in the case of monitoring the spectral shift of band gap, the obtained sensitivity is large for low refractive index contrast of cladding materials and further it increases with increase of design wavelength.

Theoretical study on the ultra-narrow bandwidth tunable atomic filter with electromagnetically induced transparency

Science.gov (United States)

Liu, Yang; Li, Shu-qing; Feng, Zhong-ying; Liu, Xiao-fei; Gao, Jin-yue

2016-12-01

To obtain the weak signal light detection from the high background noise, we present a theoretical study on the ultra-narrow bandwidth tunable atomic filter with electromagnetically induced transparency. In a three-level Λ -type atomic system in the rubidium D1 line, the bandwidth of the EIT atomic filter is narrowed to ~6.5 \\text{MHz} . And the single peak transmission of the filter can be up to 86% . Moreover, the transmission wavelength can be tuned by changing the coupling light frequency. This theoretical scheme can also be applied to other alkali atomic systems.

Efficient high-power narrow-linewidth all-fibred linearly polarized ytterbium laser source

Science.gov (United States)

Bertrand, Anthony; Liégeois, Flavien; Hernandez, Yves; Giannone, Domenico

2012-06-01

We report on experimental results on a high power, all-fibred, linearly polarized, mode-locked laser at 1.03 μm. The laser generates pulses of 40 ps wide at a repetition rate of 52 MHz, exhibiting 12 kW peak power. Dispersion in optical fibres is controlled to obtain both high power and narrow spectral linewidth. The average output power reached is 25 W with a spectral linewidth of 380 pm and a near diffraction limit beam (M2 < 1.2). This laser is an ideal candidate for applications like IR spectroscopy, where high peak power and narrow linewidth are required for subsequent wavelength conversion.

Astigmatism-free high-brightness 1060 nm edge-emitting lasers with narrow circular beam profile.

Science.gov (United States)

Miah, Md Jarez; Kalosha, Vladimir P; Bimberg, Dieter; Pohl, Johannes; Weyers, Markus

2016-12-26

1060 nm high-brightness vertical broad-area edge-emitting lasers providing anastigmatic high optical power into a narrow circular beam profile are demonstrated. Ridge-waveguide (RW) lasers yield record 2.2 W single-transverse mode power in the 1060-nm wavelength range under continuous-wave (cw) operation at room temperature with excellent beam quality factor M2 ≤ 2. Independent of operating current the astigmatism is only 2.5 µm. 3 mm long broad-area (BA) lasers produce a θvert as narrow as 9° full width at half maximum, which agrees well with our simulation results, being insensitive to drive current. 5 mm long BA lasers deliver highest ever reported cw 12 W multimode output power among lasers showing θvert <10° in the 1060-nm wavelength range. The emitted laser beams from both RW and BA lasers show a perfect circular shape with ≤10° divergence angle at record 2.1 W and 4.2 W cw-mode output power, respectively.

High-temperature superconducting coplanar-waveguide quarter-wavelength resonator with odd- and even-mode resonant frequencies for dual-band bandpass filter

Energy Technology Data Exchange (ETDEWEB)

Satoh, Kei; Takagi, Yuta; Narahashi, Shoichi [Research Laboratories, NTT DOCOMO, INC., 3-6 Hikari-no-oka Yokosuka, Kanagawa 239-8536 Japan (Japan); Nojima, Toshio, E-mail: satokei@nttdocomo.co.j [Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo, Hokkaido 060-0814 Japan (Japan)

2010-06-01

This paper presents a high-temperature superconducting coplanar-waveguide quarter-wavelength resonator that has two different resonant modes for use in a dual-band bandpass filter (DBPF). An RF filter with multiple passbands such as the DBPF is a basic element that is expected to achieve broadband transmission by using separated frequency bands aggregately and simultaneously in future mobile communication systems. The proposed resonator has a folded center conductor and two open stubs that are aligned close to it. The odd- and even-mode resonant frequencies are configured using the space between the folded center conductor and the open stubs. It is easy to configure the odd- and even-mode coupling coefficients independently because the two resonant modes have different current density distributions. Consequently, a DBPF with two different bandwidths can be easily designed. This paper presents three design examples for a four-pole Chebyshev DBPF with different combinations of fractional bandwidths in order to investigate the validity of the proposed resonator. This paper also presents measured results of the DBPF based on the design examples from the standpoint of experimental investigation. The designed and measured frequency responses confirm that the proposed resonator is effective in achieving DBPFs not only with two of the same bandwidths but also with two different bandwidths.

Exposure measuring techniques for wide band mobile radio-communications

International Nuclear Information System (INIS)

Trinchero, S.; Benedetto, A.; Anglesio, L.; D'Amore, G.; Trinchero, D.

2004-01-01

The paper illustrates the limits and performances of different experimental monitoring techniques, which are applied to digitally modulated radiofrequency electromagnetic fields used for mobile telecommunications. Different experimental set-ups have been developed, verified and applied for the analysis and characterisation of wide band probes and narrow band measuring procedures. (authors)

Thermally controlled mid-IR band-gap engineering in all-glass chalcogenide microstructured fibers: a numerical study

DEFF Research Database (Denmark)

Barh, Ajanta; Varshney, Ravi K.; Pal, Bishnu P.

2017-01-01

Presence of photonic band-gap (PBG) in an all-glass low refractive index (RI) contrast chalcogenide (Ch) microstructured optical fibers (MOFs) is investigated numerically. The effect of external temperature on the position of band-gap is explored to realize potential fiber-based wavelength filters....... Then the temperature sensitivity of band-gaps is investigated to design fiber-based mid-IR wavelength filters/sensors....

Panchromatic cooperative hyperspectral adaptive wide band deletion repair method

Science.gov (United States)

Jiang, Bitao; Shi, Chunyu

2018-02-01

In the hyperspectral data, the phenomenon of stripe deletion often occurs, which seriously affects the efficiency and accuracy of data analysis and application. Narrow band deletion can be directly repaired by interpolation, and this method is not ideal for wide band deletion repair. In this paper, an adaptive spectral wide band missing restoration method based on panchromatic information is proposed, and the effectiveness of the algorithm is verified by experiments.

Next-generation narrow band imaging system for colonic polyp detection: a prospective multicenter randomized trial.

Science.gov (United States)

Horimatsu, Takahiro; Sano, Yasushi; Tanaka, Shinji; Kawamura, Takuji; Saito, Shoichi; Iwatate, Mineo; Oka, Shiro; Uno, Koji; Yoshimura, Kenichi; Ishikawa, Hideki; Muto, Manabu; Tajiri, Hisao

2015-07-01

Previous studies have yielded conflicting results on the colonic polyp detection rate with narrow-band imaging (NBI) compared with white-light imaging (WLI). We compared the mean number of colonic polyps detected per patient for NBI versus WLI using a next-generation NBI system (EVIS LUCERA ELITE; Olympus Medical Systems) used with standard-definition (SD) colonoscopy and wide-angle (WA) colonoscopy. this study is a 2 × 2 factorial, prospective, multicenter randomized controlled trial. this study was conducted at five academic centers in Japan. patients were allocated to one of four groups: (1) WLI with SD colonoscopy (H260AZI), (2) NBI with SD colonoscopy (H260AZI), (3) WLI with WA colonoscopy (CF-HQ290), and (4) NBI with WA colonoscopy (CF-HQ290). the mean numbers of polyps detected per patient were compared between the four groups: WLI with/without WA colonoscopy and NBI with/without WA colonoscopy. Of the 454 patients recruited, 431 patients were enrolled. The total numbers of polyps detected by WLI with SD, NBI with SD, WLI with WA, and NBI with WA were 164, 176, 188, and 241, respectively. The mean number of polyps detected per patient was significantly higher in the NBI group than in the WLI group (2.01 vs 1.56; P = 0.032). The rate was not higher in the WA group than in the SD group (1.97 vs 1.61; P = 0.089). Although WA colonoscopy did not improve the polyp detection, next-generation NBI colonoscopy represents a significant improvement in the detection of colonic polyps.

Wavelength-Dependent PSFs and their Impact on Weak Lensing Measurements

Science.gov (United States)

Carlsten, S. G.; Strauss, Michael A.; Lupton, Robert H.; Meyers, Joshua E.; Miyazaki, Satoshi

2018-06-01

We measure and model the wavelength dependence of the point spread function (PSF) in the Hyper Suprime-Cam Subaru Strategic Program survey. We find that PSF chromaticity is present in that redder stars appear smaller than bluer stars in the g, r, and i-bands at the 1-2 per cent level and in the z and y-bands at the 0.1-0.2 per cent level. From the color dependence of the PSF, we fit a model between the monochromatic PSF size based on weighted second moments, R, and wavelength of the form R(λ)∝λ-b. We find values of b between 0.2 and 0.5, depending on the epoch and filter. This is consistent with the expectations of a turbulent atmosphere with an outer scale length of ˜10 - 100 m, indicating that the atmosphere is dominating the chromaticity. In the best seeing data, we find that the optical system and detector also contribute some wavelength dependence. Meyers & Burchat (2015b) showed that b must be measured to an accuracy of ˜0.02 not to dominate the systematic error budget of the Large Synoptic Survey Telescope (LSST) weak lensing (WL) survey. Using simple image simulations, we find that b can be inferred with this accuracy in the r and i-bands for all positions in the LSST focal plane, assuming a stellar density of 1 star arcmin-2 and that the optical component of the PSF can be accurately modeled. Therefore, it is possible to correct for most, if not all, of the bias that the wavelength-dependent PSF will introduce into an LSST-like WL survey.

The split symbol moments SNR estimator in narrow-band channels

Science.gov (United States)

Shah, Biren; Hinedi, Sami

1990-01-01

The split symbol moments estimator is an algorithm that is designed to estimate symbol SNR in the presence of additive white Gaussian noise. The performance of the algorithm in band-limited channels is examined, and the effects of the resulting intersymbol interference are quantified. All results obtained are in closed form and can be easily evaluated numerically for performance-prediction purposes. The results are also validated through digital simulations.

Selected area growth integrated wavelength converter based on PD-EAM optical logic gate

International Nuclear Information System (INIS)

Niu Bin; Zhou Daibing; Zhang Can; Liang Song; Lu Dan; Zhao Lingjuan; Wang Wei; Qiu Jifang; Wu Jian

2014-01-01

A selected area growth wavelength converter based on a PD-EAM optical logic gate for WDM application is presented, integrating an EML transmitter and a SOA-PD receiver. The design, fabrication, and DC characters were analyzed. A 2 Gb/s NRZ signal based on the C-band wavelength converted to 1555 nm with the highest extinction ratio of 7 dB was achieved and wavelength converted eye diagrams with eyes opened were presented. (semiconductor devices)

The role of rare earths in narrow energy gap semiconductors

International Nuclear Information System (INIS)

Partin, D.L.; Heremans, J.; Morelli, D.T.; Thrush, C.M.

1991-01-01

Narrow energy band gap semiconductors are potentially useful for various devices, including infrared detectors and diode lasers. Rare earth elements have been introduced into lead chalcogenide semiconductors using the molecular beam epitaxy growth process. Europium and ytterbium increase the energy band gap, and nearly lattice-matched heterojunctions have been grown. In some cases, valence changes in the rare earth element cause doping of the alloy. In this paper some initial investigations of the addition of europium to indium antimonide are reported, including the variation of lattice parameter and optical transmission with composition and a negative magnetoresistance effect

Enhanced Plasmonic Wavelength Selective Infrared Emission Combined with Microheater

Directory of Open Access Journals (Sweden)

Hiroki Ishihara

2017-09-01

Full Text Available The indirect wavelength selective thermal emitter that we have proposed is constructed using a new microheater, demonstrating the enhancement of the emission peak generated by the surface plasmon polariton. The thermal isolation is improved using a 2 μm-thick Si membrane having 3.6 and 5.4 mm outer diameter. The emission at around the wavelength of the absorption band of CO2 gas is enhanced. The absorption signal increases, confirming the suitability for gas sensing. Against input power, the intensity at the peak wavelength shows a steeper increasing ratio than the background intensity. The microheater with higher thermal isolation gives larger peak intensity and its increasing ratio against the input power.

Dual-band infrared camera

Science.gov (United States)

Vogel, H.; Schlemmer, H.

2005-10-01

Every year, numerous accidents happen on European roads due to bad visibility (fog, night, heavy rain). Similarly, the dramatic aviation accidents of year 2001 in Milan and Zurich have reminded us that aviation safety is equally affected by reduced visibility. A dual-band thermal imager was developed in order to raise human situation awareness under conditions of reduced visibility especially in the automotive and aeronautical context but also for all transportation or surveillance tasks. The chosen wavelength bands are the Short Wave Infrared SWIR and the Long Wave Infrared LWIR band which are less obscured by reduced visibility conditions than the visible band. Furthermore, our field tests clearly show that the two different spectral bands very often contain complementary information. Pyramidal fusion is used to integrate complementary and redundant features of the multi-spectral images into a fused image which can be displayed on a monitor to provide more and better information for the driver or pilot.

Stable narrow spacing dual-wavelength Q-switched graphene oxide embedded in a photonic crystal fiber

International Nuclear Information System (INIS)

Ahmad, H; Soltanian, M R K; Alimadad, M; Harun, S W

2014-01-01

An ultra-stable dual-wavelength saturable absorber based on a cladding-embedded commercial graphene oxide (GO) solution by capillary action in a solid core photonic crystal fiber (PCF) is demonstrated for the first time. The saturation absorption property is achieved through evanescent coupling between the guided light and the cladding-filled graphene layers. Stable spacing dual-wavelength fiber lasing is attained by controlling the polarization state of a simple 0.9 m long ring of highly doped Leikki Er80-8/125 erbium-doped fiber as the primary gain medium with PCF, polarization controller and tunable bandpass filter. Embedded GO is used to generate the desired pulsed output, and the laser is capable of generating pulses having a repetition rate of 24 kHz with an average output power and pulse energy of 0.167 mW and 8.98 nJ, respectively, at the maximum pump power of 220 mW. (paper)

Kinetic energy dependence of carrier diffusion in a GaAs epilayer studied by wavelength selective PL imaging

Energy Technology Data Exchange (ETDEWEB)

Zhang, S. [University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Providence High School, Charlotte, NC 28270 (United States); Su, L.Q.; Kon, J. [University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Gfroerer, T. [Davidson College, Davidson, NC 28035 (United States); Wanlass, M.W. [National Renewable Energy Laboratory, Golden, CO 80401 (United States); Zhang, Y., E-mail: yong.zhang@uncc.edu [University of North Carolina at Charlotte, Charlotte, NC 28223 (United States)

2017-05-15

Photoluminescence (PL) imaging has been shown to be an efficient technique for investigating carrier diffusion in semiconductors. In the past, the measurement was typically carried out by measuring at one wavelength (e.g., at the band gap) or simply the whole emission band. At room temperature in a semiconductor like GaAs, the band-to-band PL emission may occur in a spectral range over 200 meV, vastly exceeding the average thermal energy of about 26 meV. To investigate the potential dependence of the carrier diffusion on the carrier kinetic energy, we performed wavelength selective PL imaging on a GaAs double hetero-structure in a spectral range from about 70 meV above to 50 meV below the bandgap, extracting the carrier diffusion lengths at different PL wavelengths by fitting the imaging data to a theoretical model. The results clearly show that the locally generated carriers of different kinetic energies mostly diffuse together, maintaining the same thermal distribution throughout the diffusion process. Potential effects related to carrier density, self-absorption, lateral wave-guiding, and local heating are also discussed.

Optofluidic tuning of photonic crystal band edge lasers

DEFF Research Database (Denmark)

Bernal, Felipe; Christiansen, Mads Brøkner; Gersborg-Hansen, Morten

2007-01-01

We demonstrate optofluidic tuning of polymer photonic crystal band edge lasers with an imposed rectangular symmetry. The emission wavelength depends on both lattice constant and cladding refractive index. The emission wavelength is shown to change 1 nm with a cladding refractive index change of 10......−2. The rectangular symmetry modification alters the emission characteristics of the devices and the relative emission intensities along the symmetry axes depend on cladding refractive index, suggesting a sensor concept based on detection of intensity rather than wavelength....

The Role of Narrow Band Imaging in the Detection of Recurrent Laryngeal and Hypopharyngeal Cancer after Curative Radiotherapy

Directory of Open Access Journals (Sweden)

Michal Zabrodsky

2014-01-01

Full Text Available Narrow band imaging is considered a significant improvement in the possibility of detecting early mucosal lesion of the upper aerodigestive tract. Early detection of mucosal neoplastic lesions is of utmost importance for patients survival. There is evidence that, especially in patients previously treated by means of curative radiotherapy or chemoradiotherapy, the early detection rate of recurrent disease is quite low. The aim of this study was to prove whether the videoendoscopy coupled with NBI might help detect recurrent or secondary tumors of the upper aerodigestive tract. 66 patients previously treated by means of RT or CRT with curative intent were enrolled in the study. All patients underwent transnasal flexible videoendoscopy with NBI mode under local anesthesia. When a suspicious lesion was identified in an ambulatory setting, its nature was proved histologically. Many of these changes were not identifiable by means of conventional white light (WL endoscopy. The accuracy, sensitivity, specificity, and positive and negative predictive value of the method are very high (88%, 92%, 76%, 96%, and 91%, resp.. Results demonstrate that outpatient transnasal endoscopy with NBI is an excellent method for the follow-up of patients with carcinomas of the larynx and the hypopharynx primarily treated with radiotherapy.

Diagnostic Performance of Narrow Band Imaging for Laryngeal Cancer: A Systematic Review and Meta-analysis.

Science.gov (United States)

Sun, Changling; Han, Xue; Li, Xiaoying; Zhang, Yayun; Du, Xiaodong

2017-04-01

Objective To evaluate the performance of narrow band imaging (NBI) for the diagnosis of laryngeal cancer and to compare the diagnostic value of NBI with that of white light endoscopy. Data Sources PubMed, Embase, Cochrane Library, and CNKI databases. Review Methods Data analyses were performed with Meta-DiSc. The updated Quality Assessment of Diagnostic Accuracy Studies-2 tool was used to assess study quality and potential bias. Publication bias was assessed with the Deeks's asymmetry test. The protocol used in this article has been published on PROSPERO and is in accordance with the PRISMA checklist. The registry number for this study is CRD42015025866. Results Six studies including 716 lesions were included in this meta-analysis. The pooled sensitivity, specificity, and diagnostic odds ratio for the NBI diagnosis of laryngeal cancer were 0.94 (95% confidence interval [95% CI]: 0.91-0.96), 0.89 (95% CI: 0.85-0.92), and 142.12 (95% CI: 46.42-435.15), respectively, and the area under receiver operating characteristics curve was 0.97. Among the 6 studies, 3 evaluated the diagnostic value of white light endoscopy, with a sensitivity of 0.81 (95% CI: 0.76-0.86), a specificity of 0.92 (95% CI: 0.88-0.95), and a diagnostic odds ratio of 33.82 (95% CI: 14.76-77.49). The evaluation of heterogeneity, calculated per the diagnostic odds ratio, gave an I 2 of 66%. No marked publication bias ( P = .84) was detected in this meta-analysis. Conclusion The sensitivity of NBI is superior to white light endoscopy, and the potential value of NBI needs to be validated in future studies.

Diagnostic efficacy of magnifying endoscopy with narrow-band imaging for gastric neoplasms: a meta-analysis.

Directory of Open Access Journals (Sweden)

Xiuhe Lv

Full Text Available Magnifying endoscopy with narrow-band imaging (ME-NBI is a novel, image-enhanced endoscopic technique for differentiating gastrointestinal neoplasms and potentially enabling pathological diagnosis.The aim of this analysis was to assess the diagnostic performance of ME-NBI for gastric neoplasms.We performed a systematic search of the PubMed, EMbase, Web of Science, and Cochrane Library databases for relevant studies. Meta-DiSc (version 1.4 and STATA (version 11.0 software were used for the data analysis. Random effects models were used to assess diagnostic efficacy. Heterogeneity was tested by the Q statistic and I2 statistic. Meta-regression was used to analyze the sources of heterogeneity.A total of 10 studies, with 2151 lesions, were included. The pooled characteristics of these studies were as follows: sensitivity 0.85 (95% confidence interval [CI]: 0.81-0.89, specificity 0.96 (95% confidence interval [CI]: 0.95-0.97, and area under the curve (AUC 0.9647. In the subgroup analysis, which compared the diagnostic efficacy of ME-NBI and white light imaging (WLI, the pooled sensitivity and specificity of ME-NBI were 0.87 (95% CI: 0.80-0.92 and 0.93 (95% CI: 0.90-0.95, respectively, and the area under the curve (AUC was 0.9556. In contrast, the pooled sensitivity and specificity of WLI were 0.61 (95% CI: 0.53-0.69 and 0.65 (95% CI: 0.60-0.69, respectively, and the area under the curve (AUC was 0.6772.ME-NBI presents a high diagnostic value for gastric neoplasms and has a high specificity.

Evaluation of a color fused dual-band NVG

NARCIS (Netherlands)

Hogervorst, M.A.; Toet, A.

2009-01-01

We have tested a prototype dual-band NVG system consisting of two NVGs fitted with filters that split the NVG sensitive range into a short (visual) and a long wavelength (NIR) band. The Color-the-night technique (see Hogervorst & Toet, SPIE D&S ‘08) was used to fuse the images of the two sensors. We

MULTI-WAVELENGTH RADIO CONTINUUM EMISSION STUDIES OF DUST-FREE RED GIANTS

International Nuclear Information System (INIS)

O'Gorman, Eamon; Harper, Graham M.; Brown, Alexander; Drake, Stephen; Richards, Anita M. S.

2013-01-01

Multi-wavelength centimeter continuum observations of non-dusty, non-pulsating K spectral-type red giants directly sample their chromospheres and wind acceleration zones. Such stars are feeble emitters at these wavelengths, however, and previous observations have provided only a small number of modest signal-to-noise measurements slowly accumulated over three decades. We present multi-wavelength Karl G. Jansky Very Large Array thermal continuum observations of the wind acceleration zones of two dust-free red giants, Arcturus (α Boo: K2 III) and Aldebaran (α Tau: K5 III). Importantly, most of our observations of each star were carried out over just a few days, so that we obtained a snapshot of the different stellar atmospheric layers sampled at different wavelengths, independent of any long-term variability. We report the first detections at several wavelengths for each star including a detection at 10 cm (3.0 GHz: S band) for both stars and a 20 cm (1.5 GHz: L band) detection for α Boo. This is the first time single (non-binary) luminosity class III red giants have been detected at these continuum wavelengths. Our long-wavelength data sample the outer layers of α Boo's atmosphere where its wind velocity is approaching (or possibly has reached) its terminal value and the ionization balance is becoming frozen-in. For α Tau, however, our long-wavelength data are still sampling its inner atmosphere, where the wind is still accelerating probably due to its lower mass-loss rate. We compare our data with published semi-empirical models based on ultraviolet data, and the marked deviations highlight the need for new atmospheric models to be developed. Spectral indices are used to discuss the possible properties of the stellar atmospheres, and we find evidence for a rapidly cooling wind in the case of α Boo. Finally, we develop a simple analytical wind model for α Boo based on our new long-wavelength flux measurements

Multi-wavelength Radio Continuum Emission Studies of Dust-free Red Giants

Science.gov (United States)

O'Gorman, Eamon; Harper, Graham M.; Brown, Alexander; Dranke, Stephen; Richards, Anita M. S.

2013-01-01

Multi-wavelength centimeter continuum observations of non-dusty, non-pulsating K spectral-type red giants directly sample their chromospheres and wind acceleration zones. Such stars are feeble emitters at these wavelengths, however, and previous observations have provided only a small number of modest signal-to-noise measurements slowly accumulated over three decades. We present multi-wavelength Karl G. Jansky Very Large Array thermal continuum observations of the wind acceleration zones of two dust-free red giants, Arcturus (alpha Boo: K2 III) and Aldebaran (alpha Tau: K5 III). Importantly, most of our observations of each star were carried out over just a few days, so that we obtained a snapshot of the different stellar atmospheric layers sampled at different wavelengths, independent of any long-term variability. We report the first detections at several wavelengths for each star including a detection at 10 cm (3.0 GHz: S band) for both stars and a 20 cm (1.5 GHz: L band) detection for alpha Boo. This is the first time single (non-binary) luminosity class III red giants have been detected at these continuum wavelengths. Our long-wavelength data sample the outer layers of alpha Boo's atmosphere where its wind velocity is approaching (or possibly has reached) its terminal value and the ionization balance is becoming frozen-in. For alpha Tau, however, our long-wavelength data are still sampling its inner atmosphere, where the wind is still accelerating probably due to its lower mass-loss rate. We compare our data with published semi-empirical models based on ultraviolet data, and the marked deviations highlight the need for new atmospheric models to be developed. Spectral indices are used to discuss the possible properties of the stellar atmospheres, and we find evidence for a rapidly cooling wind in the case of alpha Boo. Finally, we develop a simple analytical wind model for alpha Boo based on our new long-wavelength flux measurements.

MULTI-WAVELENGTH RADIO CONTINUUM EMISSION STUDIES OF DUST-FREE RED GIANTS

Energy Technology Data Exchange (ETDEWEB)

O' Gorman, Eamon; Harper, Graham M. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Brown, Alexander [Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309 (United States); Drake, Stephen [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Richards, Anita M. S. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom)

2013-10-01

Multi-wavelength centimeter continuum observations of non-dusty, non-pulsating K spectral-type red giants directly sample their chromospheres and wind acceleration zones. Such stars are feeble emitters at these wavelengths, however, and previous observations have provided only a small number of modest signal-to-noise measurements slowly accumulated over three decades. We present multi-wavelength Karl G. Jansky Very Large Array thermal continuum observations of the wind acceleration zones of two dust-free red giants, Arcturus (α Boo: K2 III) and Aldebaran (α Tau: K5 III). Importantly, most of our observations of each star were carried out over just a few days, so that we obtained a snapshot of the different stellar atmospheric layers sampled at different wavelengths, independent of any long-term variability. We report the first detections at several wavelengths for each star including a detection at 10 cm (3.0 GHz: S band) for both stars and a 20 cm (1.5 GHz: L band) detection for α Boo. This is the first time single (non-binary) luminosity class III red giants have been detected at these continuum wavelengths. Our long-wavelength data sample the outer layers of α Boo's atmosphere where its wind velocity is approaching (or possibly has reached) its terminal value and the ionization balance is becoming frozen-in. For α Tau, however, our long-wavelength data are still sampling its inner atmosphere, where the wind is still accelerating probably due to its lower mass-loss rate. We compare our data with published semi-empirical models based on ultraviolet data, and the marked deviations highlight the need for new atmospheric models to be developed. Spectral indices are used to discuss the possible properties of the stellar atmospheres, and we find evidence for a rapidly cooling wind in the case of α Boo. Finally, we develop a simple analytical wind model for α Boo based on our new long-wavelength flux measurements.

Narrow-band emission with 0.5 to 3.5 Hz varying frequency in the background of the main phase of the 17 March 2013 magnetic storm

Directory of Open Access Journals (Sweden)

Potapov A.S.

2016-12-01

Full Text Available We present results of the analysis of an unusually long narrow-band emission in the Pc1 range with increasing carrier frequency. The event was observed against the background of the main phase of a strong magnetic storm caused by arrival of a high-speed solar wind stream with a shock wave in the stream head and a long interval of negative vertical component of the interplanetary magnetic field. Emission of approximately 9-hour duration had a local character, appearing only at three stations located in the range of geographical longitude λ=100–130 E and magnetic shells L=2.2–3.4. The signal carrier frequency grew in a stepped mode from 0.5 to 3.5 Hz. We propose an emission interpretation based on the standard model of the generation of ion cyclotron waves in the magnetosphere due to the resonant wave-particle interaction with ion fluxes of moderate energies. We suppose that a continuous shift of the generation region, located in the outer area of the plasmasphere, to smaller L-shell is able to explain both the phenomenon locality and the range of the frequency increase. A narrow emission frequency band is associated with the formation of nose-like structures in the energy spectrum of ion fluxes penetrating from the geomagnetic tail into the magnetosphere. We offer a possible scenario of the processes leading to the generation of the observed emission. The scenario contains specific values of the generation region position, plasma density, magnetic field, and resonant proton energies. We discuss morphological differences of the emissions considered from known types of geomagnetic pulsations, and reasons for the occurrence of this unusual event.

SPLASH-SXDF Multi-wavelength Photometric Catalog

Science.gov (United States)

Mehta, Vihang; Scarlata, Claudia; Capak, Peter; Davidzon, Iary; Faisst, Andreas; Hsieh, Bau Ching; Ilbert, Olivier; Jarvis, Matt; Laigle, Clotilde; Phillips, John; Silverman, John; Strauss, Michael A.; Tanaka, Masayuki; Bowler, Rebecca; Coupon, Jean; Foucaud, Sébastien; Hemmati, Shoubaneh; Masters, Daniel; McCracken, Henry Joy; Mobasher, Bahram; Ouchi, Masami; Shibuya, Takatoshi; Wang, Wei-Hao

2018-04-01

We present a multi-wavelength catalog in the Subaru/XMM-Newton Deep Field (SXDF) as part of the Spitzer Large Area Survey with Hyper-Suprime-Cam (SPLASH). We include the newly acquired optical data from the Hyper-Suprime-Cam Subaru Strategic Program, accompanied by IRAC coverage from the SPLASH survey. All available optical and near-infrared data is homogenized and resampled on a common astrometric reference frame. Source detection is done using a multi-wavelength detection image including the u-band to recover the bluest objects. We measure multi-wavelength photometry and compute photometric redshifts as well as physical properties for ∼1.17 million objects over ∼4.2 deg2, with ∼800,000 objects in the 2.4 deg2 HSC-Ultra-Deep coverage. Using the available spectroscopic redshifts from various surveys over the range of 0 fraction of 3.2%. The SPLASH-SXDF catalog is a valuable, publicly available resource, perfectly suited for studying galaxies in the early universe and tracing their evolution through cosmic time.

Narrow line-width Tm3+ doped double-clad silica fiber laser based on in-line cascade biconical tapers filter

International Nuclear Information System (INIS)

Tian, Y; Zhao, J Q; Wang, W; Wang, Y Z; Gao, W

2010-01-01

Narrow line-width 793 nm laser diode cladding pumped Tm 3+ doped double cladding silica fiber laser with in-line four concatenated tapers filter was reported for the first time to our knowledge. These cascade tapers located 3.6 cm from the output end of the fiber laser was fabricated by heating and stretching method. The taper's transmitted power response as a function of wavelength was described by using local mode coupling theory and successive tapers filter model. The wavelength filter function of the in-line cascade tapers in a linear cavity fiber laser was demonstrated, and the experimental result agreed with these theories. The maximum output laser power was 736 mW, corresponding to single peak of laser spectrum with narrow line-width of ∼ 60 pm

Wavelength tuning of porous silicon microcavities

International Nuclear Information System (INIS)

Mulders, J.; Reece, P.; Zheng, W.H.; Lerondel, G.; Sun, B.; Gal, M.

2002-01-01

Full text: In the last decade much attention has been given to porous silicon (PS) for optoelectronic applications, which include efficient room temperature light emission as well as microcavity formation. Due to the large specific surface area, the use of porous silicon microcavities (PSMs) has been proposed for chemical sensing. Large wavelength shifts have indicated that the optical properties of PSMs are indeed strongly dependent on the environment. In this paper, we report the shifting of the resonance frequency of high quality PSMs, with the aim of tuning a future PS device to a certain required wavelength. The PSM samples were prepared by anodically etching p + -doped (5mΩcm) bulk silicon wafer in a solution (25%) of aqueous HF and ethanol. The device structure consisted of a PS layer sandwiched between 2 stacks of thin PS layers with alternating high and low effective refractive indices (RI), i.e. distributed Bragg mirrors (DBM). The layer thickness depends on the etch time while the porosity and hence refractive index is determined by the current density as the Si is etched. The position and the width of the stop-band can be fully controlled by the design of the DBMs, with the microcavity resonance mode sitting within the stop-band. We achieved tuning of the microcavity resonance by a number of methods, including temperature dependent tuning. The temperature induced wavelength shift was found to be of the order of 10 -15 nm. Computer modeling of these changes in the reflectivity spectra allowed us to quantify the changes of the effective refractive index and the respective layer thicknesses

Continuously tunable S and C+L bands ultra wideband erbium-doped fiber ring laser

International Nuclear Information System (INIS)

Wang, Q; Yu, Q X

2009-01-01

This paper presents an ultra wideband tunable silica-based erbium doped fiber ring laser (EDFRL) that can be continuously tuned in S and C+L bands from 1475 to 1619 nm. It is the first time that a fiber ring laser's tuning range reaches 144 nm using a standard silica-based C-band erbium-doped fiber as gain media. In the laser configuration two isolators are used in the fiber loop for suppressing the ASE in C-band and elevating the lasing gain in S-band. As a result the available lasing wavelength is extended toward the shorter wavelength of the gain bandwidth. The optimized erbium-doped fiber length, output coupling ratio and pumping laser power have been obtained through experimental study. This ring fiber laser has simple configuration, low threshold, flat laser spectral distribution and high signal-to-ASE-noise ratio. The laser will have many potential applications in fiber sensor wavelength interrogation, high-resolution spectroscopy and fiber optic communications

Wavelength calibration of an imaging spectrometer based on Savart interferometer

Science.gov (United States)

Li, Qiwei; Zhang, Chunmin; Yan, Tingyu; Quan, Naicheng; Wei, Yutong; Tong, Cuncun

2017-09-01

The basic principle of Fourier-transform imaging spectrometer (FTIS) based on Savart interferometer is outlined. The un-identical distribution of the optical path difference which leads to the wavelength drift of each row of the interferogram is analyzed. Two typical methods for wavelength calibration of the presented system are described. The first method unifies different spectral intervals and maximum spectral frequencies of each row by a reference monochromatic light with known wavelength, and the dispersion compensation of Savart interferometer is also involved. The second approach is based on the least square fitting which builds the functional relation between recovered wavelength, row number and calibrated wavelength by concise equations. The effectiveness of the two methods is experimentally demonstrated with monochromatic lights and mixed light source across the detecting band of the system, and the results indicate that the first method has higher precision and the mean root-mean-square error of the recovered wavelengths is significantly reduced from 19.896 nm to 1.353 nm, while the second method is more convenient to implement and also has good precision of 2.709 nm.

Strain induced tunable wavelength filters based on flexible polymer waveguide Bragg reflector.

Science.gov (United States)

Kim, Kyung-Jo; Seo, Jun-Kyu; Oh, Min-Cheol

2008-02-04

A tunable wavelength filter is demonstrated by imposing a strain on a polymeric Bragg reflection waveguide fabricated on a flexible substrate. The highly elastic property of flexible polymer device enables much wider tuning than the silica fiber. To produce a uniform grating pattern on a flexible plastic substrate, a post lift-off process along with an absorbing layer is incorporated. The flexible Bragg reflector shows narrow bandwidth, which is convincing the uniformity of the grating structure fabricated on plastic film. By stretching the flexible polymer device, the Bragg reflection wavelength is tuned continuously up to 45 nm for the maximum strain of 31,690 muepsilon, which is determined by the elastic expansion limit of waveguide polymer. From the linear wavelength shift proportional to the strain, the photoelastic coefficient of the ZPU polymer is found.

High gain L-band erbium-doped fiber amplifier with two-stage ...

Indian Academy of Sciences (India)

stage erbium-doped fiber amplifier; amplified spontaneous emission. Abstract. An experiment on gain enhancement in the long wavelength band erbium-doped fiber amplifier (L-band EDFA) is demonstrated using dual forward pumping scheme ...

SUPRATHERMAL ELECTRON STRAHL WIDTHS IN THE PRESENCE OF NARROW-BAND WHISTLER WAVES IN THE SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Kajdič, P. [Instituto de Geofísica, Universidad Nacional Autónoma de México, Mexico City (Mexico); Alexandrova, O.; Maksimovic, M.; Lacombe, C. [LESIA, Observatoire de Paris, PSL Research University, CNRS, UPMC UniversitéParis 06, Université Paris-Diderot, 5 Place Jules Janssen, F-92190 Meudon (France); Fazakerley, A. N., E-mail: primoz@geofisica.unam.mx [Mullard Space Science Laboratory, University College London (United Kingdom)

2016-12-20

We perform the first statistical study of the effects of the interaction of suprathermal electrons with narrow-band whistler mode waves in the solar wind (SW). We show that this interaction does occur and that it is associated with enhanced widths of the so-called strahl component. The latter is directed along the interplanetary magnetic field away from the Sun. We do the study by comparing the strahl pitch angle widths in the SW at 1 AU in the absence of large scale discontinuities and transient structures, such as interplanetary shocks, interplanetary coronal mass ejections, stream interaction regions, etc. during times when the whistler mode waves were present and when they were absent. This is done by using the data from two Cluster instruments: Spatio Temporal Analysis of Field Fluctuations experiment (STAFF) data in the frequency range between ∼0.1 and ∼200 Hz were used for determining the wave properties and Plasma Electron And Current Experiment (PEACE) data sets at 12 central energies between ∼57 eV (equivalent to ∼10 typical electron thermal energies in the SW, E{sub T}) and ∼676 eV (∼113 E{sub T}) for pitch angle measurements. Statistical analysis shows that, during the intervals with the whistler waves, the strahl component on average exhibits pitch angle widths between 2° and 12° larger than during the intervals when these waves are not present. The largest difference is obtained for the electron central energy of ∼344 eV (∼57 ET).

SUPRATHERMAL ELECTRON STRAHL WIDTHS IN THE PRESENCE OF NARROW-BAND WHISTLER WAVES IN THE SOLAR WIND

International Nuclear Information System (INIS)

Kajdič, P.; Alexandrova, O.; Maksimovic, M.; Lacombe, C.; Fazakerley, A. N.

2016-01-01

We perform the first statistical study of the effects of the interaction of suprathermal electrons with narrow-band whistler mode waves in the solar wind (SW). We show that this interaction does occur and that it is associated with enhanced widths of the so-called strahl component. The latter is directed along the interplanetary magnetic field away from the Sun. We do the study by comparing the strahl pitch angle widths in the SW at 1 AU in the absence of large scale discontinuities and transient structures, such as interplanetary shocks, interplanetary coronal mass ejections, stream interaction regions, etc. during times when the whistler mode waves were present and when they were absent. This is done by using the data from two Cluster instruments: Spatio Temporal Analysis of Field Fluctuations experiment (STAFF) data in the frequency range between ∼0.1 and ∼200 Hz were used for determining the wave properties and Plasma Electron And Current Experiment (PEACE) data sets at 12 central energies between ∼57 eV (equivalent to ∼10 typical electron thermal energies in the SW, E T ) and ∼676 eV (∼113 E T ) for pitch angle measurements. Statistical analysis shows that, during the intervals with the whistler waves, the strahl component on average exhibits pitch angle widths between 2° and 12° larger than during the intervals when these waves are not present. The largest difference is obtained for the electron central energy of ∼344 eV (∼57 ET).

Volume Bragg grating narrowed high-power and highly efficient cladding-pumped Raman fiber laser.

Science.gov (United States)

Liu, Jun; Yao, Weichao; Zhao, Chujun; Shen, Deyuan; Fan, Dianyuan

2014-12-10

High-power and highly efficient operation of a single-mode cladding-pumped Raman fiber laser with narrow lasing bandwidth is demonstrated. The spectral narrowing was realized by an external cavity containing a volume Bragg grating with a center wavelength of 1658 nm. A maximum output power of 10.4 W at 1658.3 nm with a spectral linewidth (FWHM) of ∼0.1  nm was obtained for the launched pump power of 18.4 W, corresponding to a slope efficiency of 109% with respect to the launched pump power. Lasing characteristics of free-running operation are also evaluated and discussed.

Photonic bandgap narrowing in conical hollow core Bragg fibers

Energy Technology Data Exchange (ETDEWEB)

Ozturk, Fahri Emre; Yildirim, Adem; Kanik, Mehmet [UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey); Bayindir, Mehmet, E-mail: bayindir@nano.org.tr [UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey); Department of Physics, Bilkent University, 06800 Ankara (Turkey)

2014-08-18

We report the photonic bandgap engineering of Bragg fibers by controlling the thickness profile of the fiber during the thermal drawing. Conical hollow core Bragg fibers were produced by thermal drawing under a rapidly alternating load, which was applied by introducing steep changes to the fiber drawing speed. In conventional cylindrical Bragg fibers, light is guided by omnidirectional reflections from interior dielectric mirrors with a single quarter wave stack period. In conical fibers, the diameter reduction introduced a gradient of the quarter wave stack period along the length of the fiber. Therefore, the light guided within the fiber encountered slightly smaller dielectric layer thicknesses at each reflection, resulting in a progressive blueshift of the reflectance spectrum. As the reflectance spectrum shifts, longer wavelengths of the initial bandgap cease to be omnidirectionally reflected and exit through the cladding, which narrows the photonic bandgap. A narrow transmission bandwidth is particularly desirable in hollow waveguide mid-infrared sensing schemes, where broadband light is coupled to the fiber and the analyte vapor is introduced into the hollow core to measure infrared absorption. We carried out sensing simulations using the absorption spectrum of isopropyl alcohol vapor to demonstrate the importance of narrow bandgap fibers in chemical sensing applications.

Solar Prominence Modelling and Plasma Diagnostics at ALMA Wavelengths

Science.gov (United States)

Rodger, Andrew; Labrosse, Nicolas

2017-09-01

Our aim is to test potential solar prominence plasma diagnostics as obtained with the new solar capability of the Atacama Large Millimeter/submillimeter Array (ALMA). We investigate the thermal and plasma diagnostic potential of ALMA for solar prominences through the computation of brightness temperatures at ALMA wavelengths. The brightness temperature, for a chosen line of sight, is calculated using the densities of electrons, hydrogen, and helium obtained from a radiative transfer code under non-local thermodynamic equilibrium (non-LTE) conditions, as well as the input internal parameters of the prominence model in consideration. Two distinct sets of prominence models were used: isothermal-isobaric fine-structure threads, and large-scale structures with radially increasing temperature distributions representing the prominence-to-corona transition region. We compute brightness temperatures over the range of wavelengths in which ALMA is capable of observing (0.32 - 9.6 mm), however, we particularly focus on the bands available to solar observers in ALMA cycles 4 and 5, namely 2.6 - 3.6 mm (Band 3) and 1.1 - 1.4 mm (Band 6). We show how the computed brightness temperatures and optical thicknesses in our models vary with the plasma parameters (temperature and pressure) and the wavelength of observation. We then study how ALMA observables such as the ratio of brightness temperatures at two frequencies can be used to estimate the optical thickness and the emission measure for isothermal and non-isothermal prominences. From this study we conclude that for both sets of models, ALMA presents a strong thermal diagnostic capability, provided that the interpretation of observations is supported by the use of non-LTE simulation results.

Plasmonic distributed feedback lasers at telecommunications wavelengths.

Science.gov (United States)

Marell, Milan J H; Smalbrugge, Barry; Geluk, Erik Jan; van Veldhoven, Peter J; Barcones, Beatrix; Koopmans, Bert; Nötzel, Richard; Smit, Meint K; Hill, Martin T

2011-08-01

We investigate electrically pumped, distributed feedback (DFB) lasers, based on gap-plasmon mode metallic waveguides. The waveguides have nano-scale widths below the diffraction limit and incorporate vertical groove Bragg gratings. These metallic Bragg gratings provide a broad bandwidth stop band (~500 nm) with grating coupling coefficients of over 5000/cm. A strong suppression of spontaneous emission occurs in these Bragg grating cavities, over the stop band frequencies. This strong suppression manifests itself in our experimental results as a near absence of spontaneous emission and significantly reduced lasing thresholds when compared to similar length Fabry-Pérot waveguide cavities. Furthermore, the reduced threshold pumping requirements permits us to show strong line narrowing and super linear light current curves for these plasmon mode devices even at room temperature.

Wavelength dependence for the photoreactions of DNA-Psoralen monoadducts. 1. Photoreversal of monoadducts

International Nuclear Information System (INIS)

Shi, Y.; Hearst, J.E.

1987-01-01

The authors have studied the wavelength dependence for the photoreversal of a monoadducted psoralen derivative, HMT [4'(hydroxymethyl)-4,5',8-trimethylpsoralen], in a single-stranded deoxyoligonucleotide (5'-GAAGCTACGAGC-3'). The psoralen was covalently attached to the thymidine residue in the oligonucleotide as either a furan-side monoadduct, which is formed through the cycloaddition between the 4',5' double bond of the psoralen and the 5,6 double bond of the thymidine, or a pyrone-side monoadduct, which is formed through the cycloaddition between the 3,4 double bond of the psoralen and the 5,6 double bond of the thymidine. As a comparison, they have also investigated the wavelength-dependent photoreversal of the isolated thymidine-HMT monoadducts. All photoreversal action spectra correlate with the extinction spectra of the isolate monoadducts. In the case of the pyrone-side monoadduct, two absorption bands contribute to the photoreversal with a quantum yield of 2 x 10 -2 at wavelengths below 250 nm and 7 x 10 -3 at wavelengths from 287 to 314 nm. The incorporation of the monoadduct into the DNA oligomer had little effect upon the photoreversal rate. For the furan-side monoadduct at least three absorption bands contribute to the photoreversal. The quantum yield varied from 5 x 10 -2 at wavelengths below 250 nm to 7 x 10 -4 at wavelengths between 295 and 365 nm. In contrast to the case of the pyrone-side monoadduct, the incorporation of the furan-side monoadduct into the DNA oligomer reduced the photoreversal rate constant at wavelengths above 285 nm

Diagnostic Performance of Narrow Band Imaging for Nasopharyngeal Cancer: A Systematic Review and Meta-analysis.

Science.gov (United States)

Sun, Changling; Zhang, Yayun; Han, Xue; Du, Xiaodong

2018-03-01

Objective The purposes of this study were to verify the effectiveness of the narrow band imaging (NBI) system in diagnosing nasopharyngeal cancer (NPC) as compared with white light endoscopy. Data Sources PubMed, Cochrane Library, EMBASE, CNKI, and Wan Fang databases. Review Methods Data analyses were performed with Meta-Disc. The updated Quality Assessment of Diagnostic Accuracy Studies-2 tool was used to assess study quality and potential bias. Publication bias was assessed with a Deeks asymmetry test. The registry number of the protocol published on PROSPERO is CRD42015026244. Results This meta-analysis included 10 studies of 1337 lesions. For NBI diagnosis of NPC, the pooled values were as follows: sensitivity, 0.83 (95% CI, 0.80-0.86); specificity, 0.91 (95% CI, 0.89-0.93); positive likelihood ratio, 8.82 (95% CI, 5.12-15.21); negative likelihood ratio, 0.18 (95% CI, 0.12-0.27); and diagnostic odds ratio, 65.73 (95% CI, 36.74-117.60). The area under the curve was 0.9549. For white light endoscopy in diagnosing NPC, the pooled values were as follows: sensitivity, 0.79 (95% CI, 0.75-0.83); specificity, 0.87 (95% CI, 0.84-0.90); positive likelihood ratio, 5.02 (95% CI, 1.99-12.65); negative likelihood ratio, 0.34 (95% CI, 0.24-0.49); and diagnostic odds ratio, 16.89 (95% CI, 5.98-47.66). The area under the curve was 0.8627. The evaluation of heterogeneity, calculated per the diagnostic odds ratio, gave an I 2 of 0.326. No marked publication bias ( P = .68) existed in this meta-analysis. Conclusion The sensitivity and specificity of NBI for the diagnosis of NPC are similar to those of white light endoscopy, and the potential value of NBI for the diagnosis of NPC needs to be validated further.

Narrow-band imaging can increase the visibility of fibrin caps after bleeding of esophageal varices: a case with extensive esophageal candidiasis.

Science.gov (United States)

Furuichi, Yoshihiro; Kasai, Yoshitaka; Takeuchi, Hirohito; Yoshimasu, Yuu; Kawai, Takashi; Sugimoto, Katsutoshi; Kobayashi, Yoshiyuki; Nakamura, Ikuo; Itoi, Takao

2017-08-01

A 58-year-old man with hepatitis B cirrhosis noticed black stools and underwent an endoscopy at a community hospital. The presence of esophageal varices (EVs) was confirmed, but the bleeding point was not found. He was referred to our institution and underwent a second endoscopy. Extensive white patches of esophageal candidiasis were visible on endoscopy by white-light imaging (WLI), but it was difficult to find the fibrin cap of the EVs. This was easier under narrow-band imaging (NBI), however, as the color turned red from absorption by hemoglobin adhered to it. We retrospectively measured the color differences (CD) between the fibrin cap and the surrounding mucosa 10 times using the CIE (L*a*b*) color space method. The median value of CD increased after NBI (13.9 → 43.0, p candidiasis, but the increased visibility of the fibrin cap by NBI enabled it to be found more easily. This is the first report of a case in which NBI was helpful in locating a fibrin cap of EVs.

Impedance self-matching ultra-narrow linewidth fiber resonator by use of a tunable π-phase-shifted FBG.

Science.gov (United States)

Jing, Mingyong; Yu, Bo; Hu, Jianyong; Hou, Huifang; Zhang, Guofeng; Xiao, Liantuan; Jia, Suotang

2017-05-15

In this paper, we present a novel ultra-narrow linewidth fiber resonator formed by a tunable polarization maintaining (PM) π-phase-shifted fiber Bragg grating and a PM uniform fiber Bragg grating with a certain length of PM single mode fiber patch cable between them. Theoretical prediction shows that this resonator has ultra-narrow linewidth resonant peaks and is easy to realize impedance matching. We experimentally obtain 3 MHz narrow linewidth impedance matched resonant peak in a 7.3 m ultra-long passive fiber cavity. The impedance self-matching characteristic of this resonator also makes itself particularly suitable for use in ultra-sensitive sensors, ultra-narrow band rejection optical filters and fiber lasers applications.

Mini-stop bands in single heterojunction photonic crystal waveguides

KAUST Repository

Shahid, N.; Amin, M.; Naureen, S.; Anand, S.

2013-01-01

Spectral characteristics of mini-stop bands (MSB) in line-defect photonic crystal (PhC) waveguides and in heterostructure PhC waveguides having one abrupt interface are investigated. Tunability of the MSB position by air-fill factor heterostructure PhC waveguides is utilized to demonstrate different filter functions, at optical communication wavelengths, ranging from resonance-like to wide band pass filters with high transmission. The narrowest filter realized has a resonance-like transmission peak with a full width at half maximum of 3.4 nm. These devices could be attractive for coarse wavelength selection (pass and drop) and for sensing applications. 2013 Copyright 2013 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License.

Sensitivity and specificity of narrow-band imaging nasoendoscopy compared to histopathology results in patients with suspected nasopharyngeal carcinoma

Science.gov (United States)

Adham, M.; Musa, Z.; Lisnawati; Suryati, I.

2017-08-01

Nasopharyngeal carcinoma (NPC) is a disease which is prevalent in developing countries like Indonesia. There were 164 new cases of nasopharyngeal carcinoma in the ear, nose, and throat (ENT) oncology outpatient clinic of the Cipto Mangunkusumo hospital in 2014, and 142 cases in 2015. Unfortunately, almost all of these cases presented at an advanced stage. The success of nasopharyngeal carcinoma treatment is largely determined by the stage when patients are diagnosed; it is critical to diagnose NPC as early as possible. Narrow-band imaging (NBI) is an endoscopic instrument with a light system that can improve the visualization of blood vessels of mucosal epithelial malignant tumors. NBI is expected to help clinicians to assess whether a lesion is malignant or not; to do so, it is important to know the value of sensitivity and specificity. This study is a cross-sectional form of a diagnostic test which was performed in the outpatient clinic of the ENT Head and Neck Surgery Department for the Cipto Mangunkusumo Hospital, from January to June 2016, and involved 56 subjects. Patients with a nasopharyngeal mass discovered by physical examination or imaging, and a suspected nasopharyngeal carcinoma were included as a subject. An NBI examination and biopsy was performed locally. Based on this research, NBI could be used as a screening tool for nasopharyngeal carcinoma with high sensitivity (100%), but with a low specificity result (6.7%).

Using narrow-band imaging with conventional hysteroscopy increases the detection of chronic endometritis in abnormal uterine bleeding and postmenopausal bleeding.

Science.gov (United States)

Ozturk, Mustafa; Ulubay, Mustafa; Alanbay, Ibrahim; Keskin, Uğur; Karasahin, Emre; Yenen, Müfit Cemal

2016-01-01

A preliminary study was designed to evaluate whether a narrow-band imaging (NBI) endoscopic light source could detect chronic endometritis that was not identifiable with a white light hysteroscope. A total of 86 patients with endometrial pathology (71 abnormal uterine bleeding and 15 postmenopausal bleeding) were examined by NBI endoscopy and white light hysteroscopy between February 2010 and February 2011. The surgeon initially observed the uterine cavity using white light hysteroscopy and made a diagnostic impression, which was recorded. Subsequently, after pressing a button on the telescope, NBI was used to reevaluate the endometrial mucosa. The median age of the patients was 40 years (range: 30-60 years). Endometritis was diagnosed histologically. Six cases of abnormal uterine bleeding (6/71, 8.4%, 95% confidence interval [CI] 0.03-0.17) and one case of postmenopausal bleeding (1/15, 6%, 95%CI 0.01-0.29) were only diagnosed with chronic endometritis by NBI (7/86, 8.1%, 95%CI 0.04-0.15). Capillary patterns of the endometrium can be observed by NBI and this method can be used to assess chronic endometritis. © 2015 Japan Society of Obstetrics and Gynecology.

Two-band model with off-diagonal occupation dependent hopping rate

International Nuclear Information System (INIS)

Zawadowski, A.

1989-01-01

In this paper two-band hopping model is treated on a two-dimensional square lattice. The atoms are located at the corners and the middles of the edges of the squares. In addition to the strongly overlapping orbitals of the atoms, there are extra orbitals at the corners, which are weakly hybridized. The assumption is made that the Fermi level is inside the broad band and is every near to the narrow band formed by the extra orbitals. The hamiltonian is Hubbard type, but the off-diagonal part of the two-site interaction t is kept also where one creation or annihilation operator acts on the extra orbital and the others on one of its neighbors. The weak coupling t is enhanced by the on-site Coulomb repulsion at the corners, which enhancement is a power function of the ratio of the broad band width and the narrow bank position measured from the Fermi level. That enhancement is obtained by summation of logarithmic Kondo-type corrections of orbital origin, which reflects the formation of a ground state of new type with strong orbital and spin correlations. Interaction between the particles of the broad band is generated by processes with one heavy and one light particle in the intermediate state

Utility of the cromoendoscopy and the narrow band image at colon polyps; Utilidad de la cromoendoscopia y la imagen de banda estrecha en los polipos de colon

Energy Technology Data Exchange (ETDEWEB)

Perez Gonzalez, Teresita; Chao Gonzalez, Lissette; Tusen Toledo, Yunia, E-mail: teresitaperez@infomed.sld.cu [Centro de Investigaciones Medico Quirurgicas, La Habana (Cuba); others, and

2013-07-01

Colorrectal adenomas constitute the best characterized pre-malignancy injury in the development of the cancer in the colon. Colonoscopy with diagnostic and therapeutic aims is essential to prevent the cancer appearance. A prospective, descriptive and observational study was carried out in patients that assisted for colonoscopy at Medical Surgical Research Center from September 2010 to July 2011 The Kudo and the Sano-Emura classifications were used to determine the importance of the cromoendoscopy and the narrow band image at the time to identify histological nature of the polyps in the colon. Sensibility, specificity, positive and negative predictable values and the concordance degree were estimated. The morfology and the dysplasia degree were associated.

Transmission of electromagnetic waves through sub-wavelength channels

DEFF Research Database (Denmark)

Zhang, Jingjing; Luo, Yu; Mortensen, Asger

2010-01-01

We propose a method of tunneling electromagnetic (EM) waves through a channel with sub-wavelength cross section. By filling the channel with high-ε isotropic material and implementing two matching layers with uniaxial metamterial substrates, the guided waves can go through the narrow channel...... without being cut off, as if it has just passed through the original empty waveguide. Both the magnitude and phase information of the EM fields can be effectively restored after passing this channel, regardless of the polarization of the incoming wave. The performance of this subwavelength channel, which...

Dual-Wavelength Sensitized Photopolymer for Holographic Data Storage

Science.gov (United States)

Tao, Shiquan; Zhao, Yuxia; Wan, Yuhong; Zhai, Qianli; Liu, Pengfei; Wang, Dayong; Wu, Feipeng

2010-08-01

Novel photopolymers for holographic storage were investigated by combining acrylate monomers and/or vinyl monomers as recording media and liquid epoxy resins plus an amine harder as binder. In order to improve the holographic performances of the material at blue-green wavelength band two novel dyes were used as sensitizer. The methods of evaluating the holographic performances of the material, including the shrinkage and noise characteristics, are described in detail. Preliminary experiments show that samples with optimized composite have good holographic performances, and it is possible to record dual-wavelength hologram simultaneously in this photopolymer by sharing the same optical system, thus the storage density and data rate can be doubly increased.

Improvement of the fringe analysis algorithm for wavelength scanning interferometry based on filter parameter optimization.

Science.gov (United States)

Zhang, Tao; Gao, Feng; Muhamedsalih, Hussam; Lou, Shan; Martin, Haydn; Jiang, Xiangqian

2018-03-20

The phase slope method which estimates height through fringe pattern frequency and the algorithm which estimates height through the fringe phase are the fringe analysis algorithms widely used in interferometry. Generally they both extract the phase information by filtering the signal in frequency domain after Fourier transform. Among the numerous papers in the literature about these algorithms, it is found that the design of the filter, which plays an important role, has never been discussed in detail. This paper focuses on the filter design in these algorithms for wavelength scanning interferometry (WSI), trying to optimize the parameters to acquire the optimal results. The spectral characteristics of the interference signal are analyzed first. The effective signal is found to be narrow-band (near single frequency), and the central frequency is calculated theoretically. Therefore, the position of the filter pass-band is determined. The width of the filter window is optimized with the simulation to balance the elimination of the noise and the ringing of the filter. Experimental validation of the approach is provided, and the results agree very well with the simulation. The experiment shows that accuracy can be improved by optimizing the filter design, especially when the signal quality, i.e., the signal noise ratio (SNR), is low. The proposed method also shows the potential of improving the immunity to the environmental noise by adapting the signal to acquire the optimal results through designing an adaptive filter once the signal SNR can be estimated accurately.

Ultra-narrow bandpass filters for long range optical telecommunications at 1064nm and 1550nm, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Ultra-narrow bandpass filters with high off-band rejection are needed to maximize signal to noise for free space communications. Omega Optical is developing NIR...

Oligothiophene-Indandione-Linked Narrow-Band Gap Molecules: Impact of π-Conjugated Chain Length on Photovoltaic Performance.

Science.gov (United States)

Komiyama, Hideaki; To, Takahiro; Furukawa, Seiichi; Hidaka, Yu; Shin, Woong; Ichikawa, Takahiro; Arai, Ryota; Yasuda, Takuma

2018-04-04

Solution-processed organic solar cells (OSCs) based on narrow-band gap small molecules hold great promise as next-generation energy-converting devices. In this paper, we focus on a family of A-π-D-π-A-type small molecules, namely, BDT- nT-ID ( n = 1-4) oligomers, consisting of benzo[1,2- b:4,5- b']dithiophene (BDT) as the central electron-donating (D) core, 1,3-indandione (ID) as the terminal electron-accepting (A) units, and two regioregular oligo(3-hexylthiophene)s ( nT) with different numbers of thiophene rings as the π-bridging units, and elucidate their structure-property-function relationships. The effects of the length of the π-bridging nT units on the optical absorption, thermal behavior, morphology, hole mobility, and OSC performance were systematically investigated. All oligomers exhibited broad and intense visible photoabsorption in the 400-700 nm range. The photovoltaic performances of bulk heterojunction OSCs based on BDT- nT-IDs as donors and a fullerene derivative as an acceptor were studied. Among these oligomers, BDT-2T-ID, incorporating bithiophene as the π-bridging units, showed better photovoltaic performance with a maximum power conversion efficiency as high as 6.9% under AM 1.5G illumination without using solvent additives or postdeposition treatments. These favorable properties originated from the well-developed interpenetrating network morphology of BDT-2T-ID, with larger domain sizes in the photoactive layer. Even though all oligomers have the same A-D-A main backbone, structural modulation of the π-bridging nT length was found to impact their self-organization and nanostructure formation in the solid state, as well as the corresponding OSC device performance.

Advantages of magnifying narrow-band imaging for diagnosing colorectal cancer coexisting with sessile serrated adenoma/polyp.

Science.gov (United States)

Chino, Akiko; Osumi, Hiroki; Kishihara, Teruhito; Morishige, Kenjiro; Ishikawa, Hirotaka; Tamegai, Yoshiro; Igarashi, Masahiro

2016-04-01

In the present study, we investigated the advantages of narrow-band imaging (NBI) for efficient diagnosis of sessile serrated adenoma/polyp (SSA/P). The main objective of this study was to analyze the characteristic features of cancer coexisting with serrated lesion by carrying out NBI. We evaluated 264 non-malignant serrated lesions by using three modalities (conventional white light colonoscopy, magnifying chromoendoscopy, and magnifying NBI). Of the evaluated cancer cases with serrated lesions, 37 fulfilled the inclusion criteria. In diagnosing non-malignant SSA/P, an expanded crypt opening (ECO) under magnifying NBI is a useful sign. One hundred and twenty-five lesions (87%) of observed ECO were, at the same time, detected to have type II open pit pattern, which is known to be a valuable indicator when using magnifying chromoendoscopy. ECO had high sensitivity of 80% for identifying SSA/P, with 62% specificity and 83% positive predictive value (PPV). In detecting the cancer with SSA/P, irregular vessels under magnifying NBI were frequently observed with 100% sensitivity and 99% specificity, 86% PPV and 100% negative predictive value. A focus on irregular vessels in serrated lesions might be useful for identification of cancer with SSA/P. This is an advantage of carrying out magnifying NBI in addition to being used simultaneously with other modalities by switching, and observations can be made by using wash-in water alone. We can carry out advanced examinations for selected lesions with irregular vessels. To confirm cancerous demarcation and invasion depth, a combination of all three aforementioned modalities should be done. © 2016 The Authors Digestive Endoscopy © 2016 Japan Gastroenterological Endoscopy Society.

Photo-Induced Electron Spin Polarization in a Narrow Band Gap Semiconductor Nanostructure

International Nuclear Information System (INIS)

Peter, A. John; Lee, Chang Woo

2012-01-01

Photo-induced spin dependent electron transmission through a narrow gap InSb/InGa x Sb 1−x semiconductor symmetric well is theoretically studied using transfer matrix formulism. The transparency of electron transmission is calculated as a function of electron energy for different concentrations of gallium. Enhanced spin-polarized photon assisted resonant tunnelling in the heterostructure due to Dresselhaus and Rashba spin-orbit coupling induced splitting of the resonant level and compressed spin-polarization are observed. Our results show that Dresselhaus spin-orbit coupling is dominant for the photon effect and the computed polarization efficiency increases with the photon effect and the gallium concentration

Determination of Primary Spectral Bands for Remote Sensing of Aquatic Environments

Directory of Open Access Journals (Sweden)

MingXia He

2007-12-01

Full Text Available About 30 years ago, NASA launched the first ocean-color observing satellite:the Coastal Zone Color Scanner. CZCS had 5 bands in the visible-infrared domain with anobjective to detect changes of phytoplankton (measured by concentration of chlorophyll inthe oceans. Twenty years later, for the same objective but with advanced technology, theSea-viewing Wide Field-of-view Sensor (SeaWiFS, 7 bands, the Moderate-ResolutionImaging Spectrometer (MODIS, 8 bands, and the Medium Resolution ImagingSpectrometer (MERIS, 12 bands were launched. The selection of the number of bands andtheir positions was based on experimental and theoretical results achieved before thedesign of these satellite sensors. Recently, Lee and Carder (2002 demonstrated that foradequate derivation of major properties (phytoplankton biomass, colored dissolved organicmatter, suspended sediments, and bottom properties in both oceanic and coastalenvironments from observation of water color, it is better for a sensor to have ~15 bands inthe 400 – 800 nm range. In that study, however, it did not provide detailed analysesregarding the spectral locations of the 15 bands. Here, from nearly 400 hyperspectral (~ 3-nm resolution measurements of remote-sensing reflectance (a measure of water colortaken in both coastal and oceanic waters covering both optically deep and optically shallowwaters, first- and second-order derivatives were calculated after interpolating themeasurements to 1-nm resolution. From these derivatives, the frequency of zero values foreach wavelength was accounted for, and the distribution spectrum of such frequencies wasobtained. Furthermore, the wavelengths that have the highest appearance of zeros wereidentified. Because these spectral locations indicate extrema (a local maximum orminimum of the reflectance spectrum or inflections of the spectral curvature, placing the bands of a sensor at these wavelengths maximizes the potential of capturing (and then restoring

Wavelength-modulated spectroscopy of the sub-bandgap response of solar cell devices

Energy Technology Data Exchange (ETDEWEB)

Mandanirina, N.H., E-mail: s213514095@nmmu.ac.za; Botha, J.R.; Wagener, M.C.

2016-01-01

A wavelength-modulation setup for measuring the differential photo-response of a GaSb/GaAs quantum ring solar cell structure is reported. The pseudo-monochromatic wavelength is modulated at the output of a conventional monochromator by means of a vibrating slit mechanism. The vibrating slit was able to modulate the excitation wavelength up to 33 nm. The intensity of the light beam was kept constant through a unique flux correction module, designed and built in-house. The setup enabled measurements in the near-infrared range (from 1000 to 1300 nm), which is specifically used to probe the sub-band gap differential photo-response of GaAs solar cells.

Single-photon generator for optical telecommunication wavelength

International Nuclear Information System (INIS)

Usuki, T; Sakuma, Y; Hirose, S; Takemoto, K; Yokoyama, N; Miyazawa, T; Takatsu, M; Arakawa, Y

2006-01-01

We report on the generation of single-photon pulses from a single InAs/InP quantum dot in telecommunication bands (1.3-1.55 μm: higher transmittance through an optical fiber). First we prepared InAs quantum dots on InP (0 0 1) substrates in a low-pressure MOCVD by using a so-called InP 'double-cap' procedure. The quantum dots have well-controlled photo emission wavelength in the telecommunication bands. We also developed a single-photon emitter in which quantum dots were embedded. Numerical simulation designed the emitter to realize efficient injection of the emitted photons into a single-mode optical fiber. Using a Hanbury-Brown and Twiss technique has proved that the photons through the fiber were single photons

Investigation of the effects of metal-wire resonators in sub-wavelength array based on time-reversal technique

International Nuclear Information System (INIS)

Tu, Hui-Lin; Xiao, Shao-Qiu

2016-01-01

The resonant metalens consisting of metal-wire resonators with equally finite length can break the diffraction barrier well suited for super-resolution imaging. In this study, a basic combination constructed by two metal-wire resonators with different lengths is proposed, and its resonant characteristics is analyzed using the method of moments (MoM). Based on the time reversal (TR) technique, this kind of combination can be applied to a sub-wavelength two-element antenna array with a 1/40-wavelength interval to make the elements work simultaneously with little interference in the frequency band of 1.0-1.5 GHz and 1.5-2.0 GHz, respectively. The simulations and experiments show that analysis of MoM and the application of the resonators can be used to design multi-frequency sub-wavelength antenna arrays efficiently. This general design method is convenient and can be used for many applications, such as weakening jamming effectiveness in communication systems, and sub-wavelength imaging in a broad frequency band.

Interband emission energy in a dilute nitride quaternary semiconductor quantum dot for longer wavelength applications

Science.gov (United States)

Mageshwari, P. Uma; Peter, A. John; Lee, Chang Woo; Duque, C. A.

2016-07-01

Excitonic properties are studied in a strained Ga1-xInxNyAs1-y/GaAs cylindrical quantum dot. The optimum condition for the desired band alignment for emitting wavelength 1.55 μm is investigated using band anticrossing model and the model solid theory. The band gap and the band discontinuities of a Ga1-xInxNyAs1-y/GaAs quantum dot on GaAs are computed with the geometrical confinement effect. The binding energy of the exciton, the oscillator strength and its radiative life time for the optimum condition are found taking into account the spatial confinement effect. The effects of geometrical confinement and the nitrogen incorporation on the interband emission energy are brought out. The result shows that the desired band alignment for emitting wavelength 1.55 μm is achieved for the inclusion of alloy contents, y=0.0554% and x=0.339% in Ga1-xInxNyAs1-y/GaAs quantum dot. And the incorporation of nitrogen and indium shows the red-shift and the geometrical confinement shows the blue-shift. And it can be applied for fibre optical communication networks.

Performance Enhancement in L-Band Edfa Through Dual Stage Technique

Directory of Open Access Journals (Sweden)

S. W. Harun and H. Ahmad

2012-10-01

Full Text Available An experiment on gain enhancement in the long wavelength band erbium doped fiber amplifier (L-band EDFA is demonstrated. It uses a dual stage technique with dual forward pumping scheme. Compared to a conventional single stage amplifier, the small signal gain for 1580nm signal can be improved by 5.5dB without paying much noise figure penalty. The corresponding noise figure penalty was 0.3dB due to the insertion loss of the optical isolator. The optimum pump power ratio for the first pump is experimentally determined to be 33%. The maximum gain improvement of 8.3dB was obtained at a signal wavelength of 1568nm while signal and total pump powers were fixed at -30dBm and 92mW, respectively. The employment of dual stage amplifier system seems to play an important role in the development of practical L-band EDFA from the perspective of economical usage of pump power.Key Words:  erbium doped fibre; optical amplifier; L-band EDFA; dual stage EDFA; amplified spontaneous emission

An ultra-wideband tunable multi-wavelength Brillouin fibre laser based on a semiconductor optical amplifier and dispersion compensating fibre in a linear cavity configuration

International Nuclear Information System (INIS)

Zulkifli, M Z; Ahmad, H; Hassan, N A; Jemangin, M H; Harun, S W

2011-01-01

A multi-wavelength Brillouin fibre laser (MBFL) with an ultra-wideband tuning range from 1420 nm to 1620 nm is demonstrated. The MBFL uses an ultra-wideband semiconductor optical amplifier (SOA) and a dispersion compensating fibre (DCF) as the linear gain medium and nonlinear gain medium, respectively. The proposed MBFL has a wide tuning range covering the short (S-), conventional (C-) and long (L-) bands with a wavelength spacing of 0.08 nm, making it highly suitable for DWDM system applications. The output power of the observed Brillouin Stokes ranges approximately from -5.94 dBm to -0.41 dBm for the S-band, from -4.34 dBm to 0.02 dBm for the C-band and from -2.19 dBm to 0.39 dBm for the L-band. The spacing between each adjacent wavelengths of all the three bands is about 0.08 nm, which is approximately 10.7 GHz for the frequency domain. (lasers)

Multi-layer monochromator

International Nuclear Information System (INIS)

Schoenborn, B.P.; Caspar, D.L.D.

1975-01-01

This invention provides an artificial monochromator crystal for efficiently selecting a narrow band of neutron wavelengths from a neutron beam having a Maxwellian wavelength distribution, by providing on a substrate a plurality of germanium layers, and alternate periodic layers of a different metal having tailored thicknesses, shapes, and volumetric and neutron scattering densities. (U.S.)

Narrow-band imaging (NBI for improving the assessment of vocal fold leukoplakia and overcoming the umbrella effect.

Directory of Open Access Journals (Sweden)

H Klimza

Full Text Available It is crucial to find a balance between functional and oncological outcome when choosing an adequate method for the management of vocal fold leukoplakia. Therefore, a detailed examination is a milestone in the decision-making process.To examine whether narrow-band imaging (NBI can be helpful in vocal fold assessment in the case of leukoplakia and how to overcome the "umbrella effect"- understood as the submucosal vascular pattern hidden under the plaque.Prospective cohort of 41 consecutive patients. Inclusion criteria: vocal fold leukoplakia, no previous procedures (surgery, radiotherapy, and preoperative endoscopy with an optical filter for NBI. Two groups: "suspicious" and "normal", according to the submucosal microvascular pattern of peripheral regions of the mucosa surrounding the plaque, were distinguished. Patients were qualified for a full-thickness or partial-thickness biopsy, respectively. Criteria defining suspected characters were well-demarcated brownish areas with scattered brown spots corresponding to type IV, Va, Vb, and Vc NI classifications.In 22/41 (53.7% patients with "suspected" microvascular pattern, full-thickness biopsy was performed. Moderate and severe dysplasia was revealed in 15 type IV and 7 type Va NI patients. In 19/41 (46.3% patients with proper NBI vessel pattern treated by partial-thickness biopsy, hyperkeratosis was diagnosed. There was a strong correlation between the NBI pattern and final histology: Chi2 (2 = 41.0 (p = 0.0000.The results demonstrate that NBI endoscopic assessment of the submucosal microvascular pattern of mucosa surrounding the plaque can be an effective method to categorise the risk in vocal fold leukoplakia prior to treatment.

Narrow Field of View Zenith Radiometer (NFOV) Handbook

Energy Technology Data Exchange (ETDEWEB)

Chiu, C; Marshak, A; Hodges, G; Barnard, JC; Schmelzer, J

2008-11-01

The two-channel narrow field-of-view radiometer (NFOV2) is a ground-based radiometer that looks straight up and measures radiance directly above the instrument at wavelengths of 673 and 870 nm. The field-of-view of the instrument is 1.2 degrees, and the sampling time resolution is one second. Measurements of the NFOV2 have been used to retrieve optical properties for overhead clouds that range from patchy to overcast. With a one-second sampling rate of the NFOV2, faster than almost any other ARM Climate Research Facility (ACRF) instrument, we are able, for the first time, to capture changes in cloud optical properties at the natural time scale of cloud evolution.

Emission bands of phosphorus and calculation of band structure of rare earth phosphides

International Nuclear Information System (INIS)

Al'perovich, G.I.; Gusatinskij, A.N.; Geguzin, I.I.; Blokhin, M.A.; Torbov, V.I.; Chukalin, V.I.; AN SSSR, Moscow. Inst. Novykh Khimicheskikh Problem)

1977-01-01

The method of x-ray emission spectroscopy has been used to investigate the electronic structure of monophosphides of rare-earth metals (REM). The fluorescence K bands of phosphorus have been obtained in LaP, PrP, SmP, GdP, TbP, DyP, HoP, ErP, TmP, YbP, and LuP and also the Lsub(2,3) bands of phosphorus in ErP, TmP, YbP, and LuP. Using the Green function technique involving the muffin-tin potential, the energy spectrum for ErP has been calculated in the single-electron approximation. The hystogram of electronic state distribution N(E) is compared with the experimental K and Lsub(2,3) bands of phosphorus in ErP. The agreement between the main details of N(E) and that of x-ray spectra allows to state that the model used provides a good description of the electron density distribution in crystals of REM monophosphides. In accordance with the character of the N(E) distribution the compounds under study are classified as semimetals or semiconductors with a very narrow forbidden band

Superconducting correlations in the one- and two-band Hubbard models

International Nuclear Information System (INIS)

Jain, K.P.; Ramakumar, R.; Chancey, C.C.

1989-01-01

An approximate expression is derived for the generalized energy gap function Δ kμ for a system of interacting electrons in a narrow s-band. This function has the virtue that it interpolates between the weak interaction limit (BCS) and the intermediate coupling regime. Starting from the Cooper pairing state, the authors investigate the build-up of pairing correlations and study the properties of the generalized gap in these two regimes as a function of the band filling. The coupled equations for the gap and the band filling define the self-consistency conditions. A recent extension of this analysis to the two-band model is also discussed

The band gap variation of a two dimensional binary locally resonant structure in thermal environment

Directory of Open Access Journals (Sweden)

Zhen Li

2017-01-01

Full Text Available In this study, the numerical investigation of thermal effect on band gap dynamical characteristic for a two-dimensional binary structure composed of aluminum plate periodically filled with nitrile rubber cylinder is presented. Initially, the band gap of the binary structure variation trend with increasing temperature is studied by taking the softening effect of thermal stress into account. A breakthrough is made which found the band gap being narrower and shifting to lower frequency in thermal environment. The complete band gap which in higher frequency is more sensitive to temperature that it disappears with temperature increasing. Then some new transformed models are created by changing the height of nitrile rubber cylinder from 1mm to 7mm. Simulations show that transformed model can produce a wider band gap (either flexure or complete band gap. A proper forbidden gap of elastic wave can be utilized in thermal environment although both flexure and complete band gaps become narrower with temperature. Besides that, there is a zero-frequency flat band appearing in the first flexure band, and it becomes broader with temperature increasing. The band gap width decreases trend in thermal environment, as well as the wider band gap induced by the transformed model with higher nitrile rubber cylinder is useful for the design and application of phononic crystal structures in thermal environment.

Gain-clamping techniques in two-stage double-pass L-band EDFA

Indian Academy of Sciences (India)

Two designs of long-wavelength band erbium-doped fiber amplifier (L-band. EDFA) for gain clamping in double-pass systems are demonstrated and compared. The first design is based on ring laser technique where a backward amplified spontaneous emis- sion (ASE) from the second stage is routed into the feedback loop ...

Spontaneous emission spectrum from a V-type three-level atom in a double-band photonic crystal

International Nuclear Information System (INIS)

Zhang Han Zhuang; Tang Sing Hai; Dong Po; He Jun

2002-01-01

The spontaneous emission spectrum from a V-type three-level atom embedded in a double-band photonic band gap (PBG) material has been investigated for the first time. Most interestingly it is shown that there is not only a black dark line, but also a narrow spontaneous line near the edges of the double photonic band. The positions of the dark line and narrow spontaneous line are near the transition from an empty upper level to a lower level. The lines stem from destructive and constructive quantum interferences, which induce population transfer between the two upper levels, in the PBG reservoirs. The effects of system parameters on the interference have been discussed in detail

Wavelength selection for portable noninvasive blood component measurement system based on spectral difference coefficient and dynamic spectrum

Science.gov (United States)

Feng, Ximeng; Li, Gang; Yu, Haixia; Wang, Shaohui; Yi, Xiaoqing; Lin, Ling

2018-03-01

Noninvasive blood component analysis by spectroscopy has been a hotspot in biomedical engineering in recent years. Dynamic spectrum provides an excellent idea for noninvasive blood component measurement, but studies have been limited to the application of broadband light sources and high-resolution spectroscopy instruments. In order to remove redundant information, a more effective wavelength selection method has been presented in this paper. In contrast to many common wavelength selection methods, this method is based on sensing mechanism which has a clear mechanism and can effectively avoid the noise from acquisition system. The spectral difference coefficient was theoretically proved to have a guiding significance for wavelength selection. After theoretical analysis, the multi-band spectral difference coefficient-wavelength selection method combining with the dynamic spectrum was proposed. An experimental analysis based on clinical trial data from 200 volunteers has been conducted to illustrate the effectiveness of this method. The extreme learning machine was used to develop the calibration models between the dynamic spectrum data and hemoglobin concentration. The experiment result shows that the prediction precision of hemoglobin concentration using multi-band spectral difference coefficient-wavelength selection method is higher compared with other methods.

Huge operation by energy gap of novel narrow band gap Tl1-x In1-x B x Se2 (B = Si, Ge): DFT, x-ray emission and photoconductivity studies

Science.gov (United States)

Piasecki, M.; Myronchuk, G. L.; Zamurueva, O. V.; Khyzhun, O. Y.; Parasyuk, O. V.; Fedorchuk, A. O.; Albassam, A.; El-Naggar, A. M.; Kityk, I. V.

2016-02-01

It is shown that narrow band gap semiconductors Tl1-x In1-x GexSe2 are able effectively to vary the values of the energy gap. DFT simulations of the principal bands during the cationic substitutions is done. Changes of carrier transport features is explored. Relation with the changes of the near the surface states is explored . Comparison on a common energy scale of the x-ray emission Se Kβ 2 bands, representing energy distribution of the Se 4p states, indicates that these states contribute preliminary to the top of the valence band. The temperature dependence of electrical conductivity and spectral dependence photoconductivity for the Tl1-x In1-x Ge x Se2 and Tl1-x In1-x Si x Se2 single crystals were explored and compared with previously reported Tl1-x In1-x Sn x Se2. Based on our investigations, a model of centre re-charging is proposed. Contrary to other investigated crystals in Tl1-x In1-x Ge x Se2 single crystals for x = 0.1 we observe extraordinarily enormous photoresponse, which exceed more than nine times the dark current. X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated surfaces of Tl1-x In1-x GexSe2 (x = 0.1 and 0.2) single crystals have been studied. These results indicate that the relatively low hygroscopicity of the studied single crystals is typical for the Tl1-x In1-x Ge x Se2 crystals, a property that is very important for handling these quaternary selenides as infrared materials operating at ambient conditions.

Dual-wavelength phase-shifting digital holography selectively extracting wavelength information from wavelength-multiplexed holograms.

Science.gov (United States)

Tahara, Tatsuki; Mori, Ryota; Kikunaga, Shuhei; Arai, Yasuhiko; Takaki, Yasuhiro

2015-06-15

Dual-wavelength phase-shifting digital holography that selectively extracts wavelength information from five wavelength-multiplexed holograms is presented. Specific phase shifts for respective wavelengths are introduced to remove the crosstalk components and extract only the object wave at the desired wavelength from the holograms. Object waves in multiple wavelengths are selectively extracted by utilizing 2π ambiguity and the subtraction procedures based on phase-shifting interferometry. Numerical results show the validity of the proposed technique. The proposed technique is also experimentally demonstrated.

Clamped seismic metamaterials: ultra-low frequency stop bands

International Nuclear Information System (INIS)

Achaoui, Y; Enoch, S; Guenneau, S; Antonakakis, T; Brûlé, S; Craster, R V

2017-01-01

The regularity of earthquakes, their destructive power, and the nuisance of ground vibration in urban environments, all motivate designs of defence structures to lessen the impact of seismic and ground vibration waves on buildings. Low frequency waves, in the range 1–10 Hz for earthquakes and up to a few tens of Hz for vibrations generated by human activities, cause a large amount of damage, or inconvenience; depending on the geological conditions they can travel considerable distances and may match the resonant fundamental frequency of buildings. The ultimate aim of any seismic metamaterial, or any other seismic shield, is to protect over this entire range of frequencies; the long wavelengths involved, and low frequency, have meant this has been unachievable to date. Notably this is scalable and the effects also hold for smaller devices in ultrasonics. There are three approaches to obtaining shielding effects: bragg scattering, locally resonant sub-wavelength inclusions and zero-frequency stop-band media. The former two have been explored, but the latter has not and is examined here. Elastic flexural waves, applicable in the mechanical vibrations of thin elastic plates, can be designed to have a broad zero-frequency stop-band using a periodic array of very small clamped circles. Inspired by this experimental and theoretical observation, all be it in a situation far removed from seismic waves, we demonstrate that it is possible to achieve elastic surface (Rayleigh) wave reflectors at very large wavelengths in structured soils modelled as a fully elastic layer periodically clamped to bedrock. We identify zero frequency stop-bands that only exist in the limit of columns of concrete clamped at their base to the bedrock. In a realistic configuration of a sedimentary basin 15 m deep we observe a zero frequency stop-band covering a broad frequency range of 0–30 Hz. (paper)

Architecture and design of optical path networks utilizing waveband virtual links

Science.gov (United States)

Ito, Yusaku; Mori, Yojiro; Hasegawa, Hiroshi; Sato, Ken-ichi

2016-02-01

We propose a novel optical network architecture that uses waveband virtual links, each of which can carry several optical paths, to directly bridge distant node pairs. Future photonic networks should not only transparently cover extended areas but also expand fiber capacity. However, the traversal of many ROADM nodes impairs the optical signal due to spectrum narrowing. To suppress the degradation, the bandwidth of guard bands needs to be increased, which degrades fiber frequency utilization. Waveband granular switching allows us to apply broader pass-band filtering at ROADMs and to insert sufficient guard bands between wavebands with minimum frequency utilization offset. The scheme resolves the severe spectrum narrowing effect. Moreover, the guard band between optical channels in a waveband can be minimized, which increases the number of paths that can be accommodated per fiber. In the network, wavelength path granular routing is done without utilizing waveband virtual links, and it still suffers from spectrum narrowing. A novel network design algorithm that can bound the spectrum narrowing effect by limiting the number of hops (traversed nodes that need wavelength path level routing) is proposed in this paper. This algorithm dynamically changes the waveband virtual link configuration according to the traffic distribution variation, where optical paths that need many node hops are effectively carried by virtual links. Numerical experiments demonstrate that the number of necessary fibers is reduced by 23% compared with conventional optical path networks.

Photophysical and laser characteristics of pyrromethene 567 dye ...

Indian Academy of Sciences (India)

Narrow-band laser performance of alcohol solutions of pyrromethene 567 ... curves of each dye solution were obtained by scanning the wavelength of the dye ... solutions, using ethanol and methanol solvents, are summarized in table 1.

A multi-wavelength (u.v. to visible) laser system for early detection of oral cancer

Science.gov (United States)

Najda, S. P.; Perlin, P.; Leszczyński, M.; Slight, T. J.; Meredith, W.; Schemmann, M.; Moseley, H.; Woods, J. A.; Valentine, R.; Kalra, S.; Mossey, P.; Theaker, E.; Macluskey, M.; Mimnagh, G.; Mimnagh, W.

2015-03-01

A multi-wavelength (360nm - 440nm), real-time Photonic Cancer Detector (PCD) optical system based on GaN semiconductor laser technology is outlined. A proof of concept using blue laser technology for early detection of cancer has already been tested and proven for esophageal cancer. This concept is expanded to consider a wider range of wavelengths and the PCD will initially be used for early diagnosis of oral cancers. The PCD creates an image of the oral cavity (broad field white light detection) and maps within the oral cavity any suspicious lesions with high sensitivity using a narrow field tunable detector.

Quad-Band U-Slot Antenna for Mobile Applications

Directory of Open Access Journals (Sweden)

R. L. Ruiz

2006-06-01

Full Text Available In this paper, two different planar quad-band antennas are designed, modeled, fabricated and measured. Subsequently, the antennas are redesigned using an electromagnetic band gap substrate (EBG. Those new planar antennas operate in four frequency bands: 900 MHz, 1 800 MHz (both GSM, 1 900 MHz (USA and 2 400 to 2 500 MHz (Bluetooth The antenna has four narrow U-shaped slots etched to the patch. Using software, CST Microwave Studio [1], Zeland IE3D [2], and FEMLAB [3], simulations have been carried out to investigate the antenna's performance and characteristics. The antennas designed have been also built and measured to compare the real results with those obtained from the simulations.

Continuous-wave dual-wavelength operation of a distributed feedback laser diode with an external cavity using a volume Bragg grating

Science.gov (United States)

Zheng, Yujin; Sekine, Takashi; Kurita, Takashi; Kato, Yoshinori; Kawashima, Toshiyuki

2018-03-01

We demonstrate continuous-wave dual-wavelength operation of a broad-area distributed feedback (DFB) laser diode with a single external-cavity configuration. This high-power DFB laser has a narrow bandwidth (current and temperature ranges.

Ka-band InSAR Imaging and Analysis Based on IMU Data

Directory of Open Access Journals (Sweden)

Shi Jun

2014-02-01

Full Text Available Compared with other bands, the millimeter wave Interferometric Synthetic Aperture Radar (InSAR has high accuracy and small size, which is a hot topic in InSAR research. On the other hand, shorter wavelength causes difficulties in 2D imaging and interferometric phase extraction. In this study, the imaging and phase performance of the streaming Back Projection (BP method combined with IMU data are analyzed and discussed on the basis of actual Ka-band InSAR data. It is found that because the wavelength of the Ka-band is short, it is more sensitive to the antenna phase-center history. To ensure the phase-preserving capacity, the IMU data must be used with accurate motion error compensation. Furthermore, during data processing, we verify the flat-earth-removing capacity of the BP algorithm that calculates and compensates the master and slave antenna phase centers individually.

Tunable band gap emission and surface passivation of germanium nanocrystals synthesized in the gas phase

NARCIS (Netherlands)

Wheeler, LM; Levij, L.M.; Kortshagen, U.R.

2013-01-01

The narrow bulk band gap and large exciton Bohr radius of germanium (Ge) make it an attractive material for optoelectronics utilizing band-gap-tunable photoluminescence (PL). However, realization of PL due to quantum confinement remains scarcely reported. Instead, PL is often observed from surface

Electron and hole states in quantum dot quantum wells within a spherical eight-band model

NARCIS (Netherlands)

Pokatilov, E.P.; Fonoberov, V.A.; Fomin, V.; Devreese, J.T.

2001-01-01

In order to study heterostructures composed both of materials with strongly different parameters and of materials with narrow band gaps, we have developed an approach [E. P. Pokatilov [etal], Phys. Rev. B 64, 245328 (2001), (preceding paper)], which combines the spherical eight-band effective-mass

Wavelength dependence of the efficiency of singlet oxygen generation upon photoexcitation of photosensitizers

Directory of Open Access Journals (Sweden)

Starukhin A.

2017-01-01

Full Text Available The dependence of the efficiency of singlet oxygen (1Δg generation upon excitation of photosensitizer at different wavelength was observed for several derivatives of palladium porphyrin in carbon tetrachloride. The efficiency of singlet oxygen generation upon excitation in a blue region of the spectrum (Soret band exceeds by several times the efficiency at excitation in the red spectral region (Q band. The effect of enhancement of singlet oxygen generation upon CW photoexcitation to Soret band of photosensitizer may be explained by influence of high laying triplet states of a donor molecule on the triplet-triplet energy transfer.

Wavelength selectivity of on-axis surface plasmon laser filters

International Nuclear Information System (INIS)

Harmer, S W; Townsend, P D

2002-01-01

Excitation of surface plasmons on a metal substrate, via the attenuated total reflection method can theoretically offer preferential absorption of light at one particular wavelength, whilst reflecting the nearby spectrum. Normally this 'filtering' action is limited to removal of p-polarized light, and the acceptance angle of such a filtering device is very narrow, which limits practical applications, such as separation of fundamental and laser harmonics. The possibility of avoiding this angular precision is explored by considering the complex permittivity of metal composites. By using a two or more layer structure, as opposed to a single metal substrate, the acceptance angle of the device can be broadened, by a factor of about 15 times. An example is discussed for separation of the fundamental and harmonics from a Nd : YAG laser. Variants of the structure allow the design of an in-line transmission filter for the various wavelengths with sufficient angular tolerance to include focusing lenses. Avoidance of laser ablation of the metal is discussed

Intercomparison of Unmanned Aerial Vehicle and Ground-Based Narrow Band Spectrometers Applied to Crop Trait Monitoring in Organic Potato Production

Directory of Open Access Journals (Sweden)

Marston Héracles Domingues Franceschini

2017-06-01

Full Text Available Vegetation properties can be estimated using optical sensors, acquiring data on board of different platforms. For instance, ground-based and Unmanned Aerial Vehicle (UAV-borne spectrometers can measure reflectance in narrow spectral bands, while different modelling approaches, like regressions fitted to vegetation indices, can relate spectra with crop traits. Although monitoring frameworks using multiple sensors can be more flexible, they may result in higher inaccuracy due to differences related to the sensors characteristics, which can affect information sampling. Also organic production systems can benefit from continuous monitoring focusing on crop management and stress detection, but few studies have evaluated applications with this objective. In this study, ground-based and UAV spectrometers were compared in the context of organic potato cultivation. Relatively accurate estimates were obtained for leaf chlorophyll (RMSE = 6.07 µg·cm−2, leaf area index (RMSE = 0.67 m2·m−2, canopy chlorophyll (RMSE = 0.24 g·m−2 and ground cover (RMSE = 5.5% using five UAV-based data acquisitions, from 43 to 99 days after planting. These retrievals are slightly better than those derived from ground-based measurements (RMSE = 7.25 µg·cm−2, 0.85 m2·m−2, 0.28 g·m−2 and 6.8%, respectively, for the same period. Excluding observations corresponding to the first acquisition increased retrieval accuracy and made outputs more comparable between sensors, due to relatively low vegetation cover on this date. Intercomparison of vegetation indices indicated that indices based on the contrast between spectral bands in the visible and near-infrared, like OSAVI, MCARI2 and CIg provided, at certain extent, robust outputs that could be transferred between sensors. Information sampling at plot level by both sensing solutions resulted in comparable discriminative potential concerning advanced stages of late blight incidence. These results indicate that optical

Selenium, zinc, copper, Cu/Zn ratio and total antioxidant status in the serum of vitiligo patients treated by narrow-band ultraviolet-B phototherapy.

Science.gov (United States)

Wacewicz, Marta; Socha, Katarzyna; Soroczyńska, Jolanta; Niczyporuk, Marek; Aleksiejczuk, Piotr; Ostrowska, Jolanta; Borawska, Maria H

2018-03-01

Vitiligo is a chronic, depigmenting skin disorder, whose pathogenesis is still unknown. Narrow band ultraviolet-B (NB-UVB) is now one of the most widely used treatment of vitiligo. It was suggested that trace elements may play a role in pathogenesis of vitiligo. The aim of this study was to estimate the concentration of selenium (Se), zinc (Zn), copper (Cu) and Cu/Zn ratio as well as total antioxidant status (TAS) in the serum of patients with vitiligo. We assessed 50 patients with vitiligo and 58 healthy controls. Serum levels of Se, Zn and Cu were determined by the atomic absorption spectrometry method, and the Cu/Zn ratio was also calculated. TAS in serum was measured spectrophotometrically. Serum concentration of Se in patients with vitiligo before and after phototherapy was significantly lower as compared to the control group. Zn level in the serum of patients decreased significantly after phototherapy. We observed higher Cu/Zn ratio (p vitiligo patients after NB-UVB. The current study showed some disturbances in the serum levels of trace elements and total antioxidant status in vitiligo patients.

Band alignment of type I at (100ZnTe/PbSe interface

Directory of Open Access Journals (Sweden)

Igor Konovalov

2016-06-01

Full Text Available A junction of lattice-matched cubic semiconductors ZnTe and PbSe results in a band alignment of type I so that the narrow band gap of PbSe is completely within the wider band gap of ZnTe. The valence band offset of 0.27 eV was found, representing a minor barrier during injection of holes from PbSe into ZnTe. Simple linear extrapolation of the valence band edge results in a smaller calculated band offset, but a more elaborate square root approximation was used instead, which accounts for parabolic bands. PbSe was electrodeposited at room temperature with and without Cd2+ ions in the electrolyte. Although Cd adsorbs at the surface, the presence of Cd in the electrolyte does not influence the band offset.

Band gap determination of Ni–Zn ferrites

Indian Academy of Sciences (India)

Nanocomposites of Ni–Zn with copolymer matrix of aniline and formaldehyde in presence of varying concentrations of zinc ions have been studied at room temperature and normal pressure. The energy band gap of these materials are determined by reflection spectra in the wavelength range 400–850 nm by ...

Nanoscale resonant-cavity-enhanced germanium photodetectors with lithographically defined spectral response for improved performance at telecommunications wavelengths.

Science.gov (United States)

Balram, Krishna C; Audet, Ross M; Miller, David A B

2013-04-22

We demonstrate the use of a subwavelength planar metal-dielectric resonant cavity to enhance the absorption of germanium photodetectors at wavelengths beyond the material's direct absorption edge, enabling high responsivity across the entire telecommunications C and L bands. The resonant wavelength of the detectors can be tuned linearly by varying the width of the Ge fin, allowing multiple detectors, each resonant at a different wavelength, to be fabricated in a single-step process. This approach is promising for the development of CMOS-compatible devices suitable for integrated, high-speed, and energy-efficient photodetection at telecommunications wavelengths.

Multi-Wavelength Polarimetry of Isolated Neutron Stars

Directory of Open Access Journals (Sweden)

Roberto P. Mignani

2018-03-01

Full Text Available Isolated neutron stars are known to be endowed with extreme magnetic fields, whose maximum intensity ranges from 10 12 – 10 15 G, which permeates their magnetospheres. Their surrounding environment is also strongly magnetized, especially in the compact nebulae powered by the relativistic wind from young neutron stars. The radiation from isolated neutron stars and their surrounding nebulae is, thus, supposed to bring a strong polarization signature. Measuring the neutron star polarization brings important information about the properties of their magnetosphere and of their highly magnetized environment. Being the most numerous class of isolated neutron stars, polarization measurements have been traditionally carried out for radio pulsars, hence in the radio band. In this review, I summarize multi-wavelength linear polarization measurements obtained at wavelengths other than radio both for pulsars and other types of isolated neutron stars and outline future perspectives with the upcoming observing facilities.

Endogenously generated gamma-band oscillations in early visual cortex: A neurofeedback study.

Science.gov (United States)

Merkel, Nina; Wibral, Michael; Bland, Gareth; Singer, Wolf

2018-04-26

Human subjects were trained with neurofeedback (NFB) to enhance the power of narrow-band gamma oscillations in circumscribed regions of early visual cortex. To select the region and the oscillation frequency for NFB training, gamma oscillations were induced with locally presented drifting gratings. The source and frequency of these induced oscillations were determined using beamforming methods. During NFB training the power of narrow band gamma oscillations was continuously extracted from this source with online beamforming and converted into the pitch of a tone signal. We found that seven out of ten subjects were able to selectively increase the amplitude of gamma oscillations in the absence of visual stimulation. One subject however failed completely and two subjects succeeded to manipulate the feedback signal by contraction of muscles. In all subjects the attempts to enhance visual gamma oscillations were associated with an increase of beta oscillations over precentral/frontal regions. Only successful subjects exhibited an additional marked increase of theta oscillations over precentral/prefrontal and temporal regions whereas unsuccessful subjects showed an increase of alpha band oscillations over occipital regions. We argue that spatially confined networks in early visual cortex can be entrained to engage in narrow band gamma oscillations not only by visual stimuli but also by top down signals. We interpret the concomitant increase in beta oscillations as indication for an engagement of the fronto-parietal attention network and the increase of theta oscillations as a correlate of imagery. Our finding support the application of NFB in disease conditions associated with impaired gamma synchronization. © 2018 Wiley Periodicals, Inc.

Performance Analysis of a Hybrid Raman Optical Parametric Amplifier in the O- and E-Bands for CWDM PONs

Directory of Open Access Journals (Sweden)

Sasanthi Peiris

2014-12-01

Full Text Available We describe a hybrid Raman-optical parametric amplifier (HROPA operating at the O- and E-bands and designed for coarse wavelength division multiplexed (CWDM passive optical networks (PONs. We present the mathematical model and simulation results for the optimization of this HROPA design. Our analysis shows that separating the two amplification processes allows for optimization of each one separately, e.g., proper selection of pump optical powers and wavelengths to achieve maximum gain bandwidth and low gain ripple. Furthermore, we show that the proper design of optical filters incorporated in the HROPA architecture can suppress idlers generated during the OPA process, as well as other crosstalk that leaks through the passive optical components. The design approach enables error free performance for all nine wavelengths within the low half of the CWDM band, assigned to upstream traffic in a CWDM PON architecture, for all possible transmitter wavelength misalignments (±6 nm from the center wavelength of the channel band. We show that the HROPA can achieve error-free performance with a 170-nm gain bandwidth (e.g., 1264 nm–1436 nm, a gain of >20 dB and a gain ripple of <4 dB.

Ultraviolet out-of-band radiation studies in laser tin plasma sources

Science.gov (United States)

Parchamy, Homaira; Szilagyi, John; Masnavi, Majid; Richardson, Martin

2017-11-01

Out-of-band long wavelength emission measurements from high power, high-repetition-rate extreme-ultra-violet lithography (EUVL) laser plasma sources are imperative to estimating heat deposition in EUV mirrors, and the impact of short wavelength light transported through the imaging system to the wafer surface. This paper reports a series of experiments conducted to measure the absolute spectral irradiances of laser-plasmas produced from planar tin targets over the wavelength region of 124 to 164 nm by 1.06 μm wavelength, 10 ns full-width-at-half-maximum Gaussian laser pulses. The use of spherical targets is relevant to the EUVL source scenario. Although plasmas produced from planar surfaces evolve differently, there is a close similarity to the evolution of current from 10.6 μm CO2 laser EUVL sources, which use a pre-pulse from a lower energy solid-state laser to melt and reform an initial spherical droplet into a thin planar disc target. The maximum of radiation conversion efficiency in the 124-164 nm wavelength band (1%/2πsr) occurs at the laser intensity of 1010 W cm-2. A developed collisional-radiative model reveals the strong experimental spectra that originate mainly from the 4d105p2-4d105s5p, 4d105p-4d105s resonance lines, and 4d95p-4d95s unresolved transition arrays from Sn III, Sn IV, and Sn V ions, respectively. The calculated conversion efficiencies using a 2D radiation-hydrodynamics model are in agreement with the measurements. The model predicts the out-of-band (100-400 nm) radiation conversion efficiencies generated by both 1.06 and 10.6 μm pulses. The 10.6 μm laser pulse produces a higher conversion efficiency (12%/2πsr) at the lower laser intensity of 109 W cm-2.

O-band quantum-confined Stark effect optical modulator from Ge/Si0.15Ge0.85 quantum wells by well thickness tuning

International Nuclear Information System (INIS)

Chaisakul, Papichaya; Marris-Morini, Delphine; Vakarin, Vladyslav; Vivien, Laurent; Frigerio, Jacopo; Chrastina, Daniel; Isella, Giovanni

2014-01-01

We report an O-band optical modulator from a Ge/Si 0.15 Ge 0.85 multiple quantum well (MQW). Strong O-band optical modulation in devices commonly operating within E-band wavelength range can be achieved by simply decreasing the quantum well thickness. Both spectral photocurrent and optical transmission studies are performed to evaluate material characteristics and device performance from a surface-illuminated diode and a waveguide modulator, respectively. These results demonstrate the potential of using Ge/Si 0.15 Ge 0.85 MQWs for the realization of future on-chip wavelength-division multiplexing systems with optical modulators operating at different wavelengths over a wide spectral range

Multi-Wavelength Interferometric Observations of YSO Disks

Science.gov (United States)

Ragland, Sam; Akeson, R.; Armandroff, T.; Colavita, M.; Cotton, W.; Danchi, W.; Hillenbrand, L.; Millan-Gabet, R.; Ridgway, S. T.; Traub, W.; Wizinowich, P.

2010-01-01

We initiated a multi-color interferometric study of YSO disks in the K, L and N bands using the Keck Interferometer. The initial results on two Herbig Ae/Be stars will be presented. Our observations are sensitive to the radial distribution of temperature in the inner region of the YSO disks. The geometric models show that the apparent size increases linearly with wavelength, suggesting that the disk is extended with a temperature gradient. We will discuss our results in conjunction with the previous measurements of these targets.

Multiple infrared bands absorber based on multilayer gratings

Science.gov (United States)

Liu, Xiaoyi; Gao, Jinsong; Yang, Haigui; Wang, Xiaoyi; Guo, Chengli

2018-03-01

The present study offers an Ag/Si multilayer-grating microstructure based on an Si substrate. The microstructure exhibits designable narrowband absorption in multiple infrared wavebands, especially in mid- and long-wave infrared atmospheric windows. We investigate its resonance mode mechanism, and calculate the resonance wavelengths by the Fabry-Perot and metal-insulator-metal theories for comparison with the simulation results. Furthermore, we summarize the controlling rules of the absorption peak wavelength of the microstructure to provide a new method for generating a Si-based device with multiple working bands in infrared.

Detailed characterization of complex banding in air-cooled bainitic steels

Directory of Open Access Journals (Sweden)

Morales-Rivas L.

2015-01-01

Full Text Available The presence of banding in a hot-rolled air-cooled bainitic steel has been thoroughly characterized. The banded microstructure was observed due to distinctive sensitivities to the etching agent. Microstructural and crystallographic studies by means of Scanning Electron Microscopy and Electron Backscatter Diffraction did not reveal any substantial differences between bands and matrix. However, solute segregation of some alloying elements was detected by Wavelength- Dispersive Spectroscopy, being found that bands are enriched in Cr, Mo and Si and depleted in Mn. Finally, a set of theoretical calculations suggested that the solidification mode is responsible for such unusual partitioning behavior, which is beneficial in terms of the bainitic transformation.

Alignment control of columnar liquid crystals with wavelength tunable CO2 laser irradiation

International Nuclear Information System (INIS)

Monobe, Hirosato; Awazu, Kunio; Shimizu, Yo

2008-01-01

Infrared-induced alignment change with wavelength tunable CO 2 laser irradiation for columnar liquid crystal domains was investigated for a liquid crystalline triphenylene derivative. A uniformly aligned alignment change of domains was observed when a chopped linearly polarized infrared laser light corresponding to the wavelength of the aromatic C-O-C stretching vibration band (9.65 μm) was irradiated. The results strongly imply that the infrared irradiation is a possible technique for device fabrication by use of columnar mesophase as a liquid crystalline semiconductor

VIIRS Reflective Solar Band Radiometric and Stability Evaluation Using Deep Convective Clouds

Science.gov (United States)

Chang, Tiejun; Xiong, Xiaoxiong; Mu, Qiaozhen

2016-01-01

This work takes advantage of the stable distribution of deep convective cloud (DCC) reflectance measurements to assess the calibration stability and detector difference in Visible Infrared Imaging Radiometer Suite (VIIRS) reflective bands. VIIRS Sensor Data Records (SDRs) from February 2012 to June 2015 are utilized to analyze the long-term trending, detector difference, and half angle mirror (HAM) side difference. VIIRS has two thermal emissive bands with coverage crossing 11 microns for DCC pixel identification. The comparison of the results of these two processing bands is one of the indicators of analysis reliability. The long-term stability analysis shows downward trends (up to approximately 0.4 per year) for the visible and near-infrared bands and upward trends (up to 0.5per year) for the short- and mid-wave infrared bands. The detector difference for each band is calculated as the difference relative to the average reflectance overall detectors. Except for the slightly greater than 1 difference in the two bands at 1610 nm, the detector difference is less than1 for other solar reflective bands. The detector differences show increasing trends for some short-wave bands with center wavelengths from 400 to 600 nm and remain unchanged for the bands with longer center wavelengths. The HAM side difference is insignificant and stable. Those short-wave bands from 400 to 600 nm also have relatively larger HAM side difference, up to 0.25.Comparing the striped images from SDR and the smooth images after the correction validates the analyses of detector difference and HAM side difference. These analyses are very helpful for VIIRS calibration improvement and thus enhance product quality

Dual-wavelength external cavity laser device for fluorescence suppression in Raman spectroscopy

Science.gov (United States)

Zhang, Xuting; Cai, Zhijian; Wu, Jianhong

2017-10-01

Raman spectroscopy has been widely used in the detection of drugs, pesticides, explosives, food additives and environmental pollutants, for its characteristics of fast measurement, easy sample preparation, and molecular structure analyzing capability. However, fluorescence disturbance brings a big trouble to these applications, with strong fluorescence background covering up the weak Raman signals. Recently shifted excitation Raman difference spectroscopy (SERDS) not only can completely remove the fluorescence background, but also can be easily integrated into portable Raman spectrometers. Usually, SERDS uses two lasers with small wavelength gap to excite the sample, then acquires two spectra, and subtracts one to the other to get the difference spectrum, where the fluorescence background will be rejected. So, one key aspects of successfully applying SERDS method is to obtain a dual-wavelength laser source. In this paper, a dual-wavelength laser device design based on the principles of external cavity diode laser (ECDL) is proposed, which is low-cost and compact. In addition, it has good mechanical stability because of no moving parts. These features make it an ideal laser source for SERDS technique. The experiment results showed that the device can emit narrow-spectral-width lasers of two wavelengths, with the gap smaller than 2 nanometers. The laser power corresponding to each wavelength can be up to 100mW.

Step width alters iliotibial band strain during running.

Science.gov (United States)

Meardon, Stacey A; Campbell, Samuel; Derrick, Timothy R

2012-11-01

This study assessed the effect of step width during running on factors related to iliotibial band (ITB) syndrome. Three-dimensional (3D) kinematics and kinetics were recorded from 15 healthy recreational runners during overground running under various step width conditions (preferred and at least +/- 5% of their leg length). Strain and strain rate were estimated from a musculoskeletal model of the lower extremity. Greater ITB strain and strain rate were found in the narrower step width condition (p running, especially in persons whose running style is characterized by a narrow step width, may be beneficial in the treatment and prevention of running-related ITB syndrome.

Effect of correlation on the band structure of α-cerium

International Nuclear Information System (INIS)

Rao, R.S.; Singh, R.P.

1975-01-01

The electronic band structure of f.c.c. phase of the rare earth metal cerium (α-cerium) has been calculated using a formulation of the crystal potential where correlation also has been included in addition to exchange. The Green's function method of Korringa-Kohn and Rostoker has been used due to obvious advantages in calculation. The calculations indicate that the s-d bands are hybridized with the f-levels but the f-bands are fairly narrow and lie slightly above the Fermi level. The structure of the bands is qualitatively similar to those of calculations by others except for a general shift of the entire set of bands by about 0.1 Ryd. Thd density of states has also been calculated from the bands obtained. The spin susceptibility of α-cerium has also been calculated using the Kohn-Sham method. However, the calculated additional contributions to the band structure values cannot still explain the large experimental values reported in the literature. (author)

Efficient color-tunable multiexcitonic dual wavelength emission from Type II semiconductor tetrapods.

Science.gov (United States)

Wu, Wen-Ya; Li, Mingjie; Lian, Jie; Wu, Xiangyang; Yeow, Edwin K L; Jhon, Mark H; Chan, Yinthai

2014-09-23

We synthesized colloidal InP/ZnS seeded CdS tetrapods by harnessing the structural stability of the InP/ZnS seed nanocrystals at the high reaction temperatures needed to grow the CdS arms. Because of an unexpected Type II band alignment at the interface of the InP/ZnS core and CdS arms that enhanced the occurrence of radiative excitonic recombination in CdS, these tetrapods were found to be capable of exhibiting highly efficient multiexcitonic dual wavelength emission of equal intensity at spectrally distinct wavelengths of ∼485 and ∼675 nm. Additionally, the Type II InP/ZnS seeded CdS tetrapods displayed a wider range of pump-dependent emission color-tunability (from red to white to blue) within the context of a CIE 1931 chromaticity diagram and possessed higher photostability due to suppressed multiexcitonic Auger recombination when compared to conventional Type I CdSe seeded CdS tetrapods. By employing time-resolved spectroscopy measurements, we were able to attribute the wide emission color-tunability to the large valence band offset between InP and CdS. This work highlights the importance of band alignment in the synthetic design of semiconductor nanoheterostructures, which can exhibit color-tunable multiwavelength emission with high efficiency and photostability.

The first multi-wavelength campaign of AXP 4U 0142+61 from radio to hard X-rays

NARCIS (Netherlands)

den Hartog, P.R.; Kuiper, L.; Hermsen, W.; Rea, N.; Durant, M.; Stappers, B.; Kaspi, V.M.; Dib, R.

2007-01-01

For the first time a quasi-simultaneous multi-wavelength campaign has been performed on an Anomalous X-ray Pulsar from the radio to the hard X-ray band. 4U 0142+61 was an INTEGRAL target for 1 Ms in July 2005. During these observations it was also observed in the X-ray band with Swift and RXTE, in

OFDM techniques for narrow-band power line communications; OFDM-Verfahren fuer die schmalbandige Datenuebertragung im elektrischen Energieversorgungsnetz

Energy Technology Data Exchange (ETDEWEB)

Hoch, Martin

2012-07-01

In Power Line Communications (PLC) the power distribution grid is modelled by a frequency-selective time-variant channel. Therefore, OFDM techniques are suited very well for this application since they equalize the frequency-selective behaviour in a simple fashion. For narrow-band PLC, where only little amounts of data are to be transmitted, it is advantageous to employ a non-coherent system that does not need a training sequence for channel estimation. Such type of system can be brought up with CyclicPrefix OFDM in combination with Differential Phase-Shift Keying (DPSK). In an alternative, Unique-Word OFDM, the guard interval is not filled by a cyclic prefix, but a ''unique word'', which can be deployed for channel estimation. However, there is a loss in signal-to-noise power ratio due to the special type of signal generation. This loss can be more than regained in principle, but only by applying expensive detection. Another interesting technique is Wavelet-OFDM as its transmit spectrum can be formed outstandingly because of extended transmit pulses. This implies a large overhead when short packets of data are transmitted - additionally to a training sequence, for non-coherent detection is not possible. Cyclic-Prefix OFDM and DPSK are the basis of the Physical Layers of the PLC systems ''PLC G3'' and ''PRIME''. Comparing their specifications and analyzing simulation results ''PLC G3'' turns out to be the more reliable system. In order to equalize the time-variant behaviour of the power line channel, linear equalization and Multiple Symbol Differential Detection is studied as well as algorithms to estimate the time-variant envelope. (orig.)

Competition between SFG and two SHGs in broadband type-I QPM

Science.gov (United States)

Dang, Weirui; Chen, Yuping; Gong, Mingjun; Chen, Xianfeng

2013-03-01

In this paper, we have studied the characteristics of second-order nonlinear interactions with band-overlapped type-I quasi-phase-matching (QPM) second harmonic generation (SHG) and sum-frequency generation (SFG), and predicted a blue-shift with a band-narrowing of their bands and a sunken response in the SFG curve, which are due to the phase-matching-dependent competition between band-overlapped SHG and SFG processes. This prediction is then verified by the experiment in an 18-mm-long bulk MgO-doped periodically poled lithium niobate crystal (MgO:PPLN) and may provide the candidate solution to output controlling for flexible broadcast wavelength conversion, channel-selective wavelength conversion and all-optical logic gates by cascaded QPM second-order nonlinear processes.

Spin excitation and band-narrowing in AlxGa1-xAs heterostructures

International Nuclear Information System (INIS)

Miah, M. Idrish

2010-01-01

We studied the spin excitation in dependences of the applied electric field and lattice temperature (LT) via the measurements of the circularly polarized photoluminescence (CPPL) in Al x Ga 1-x As heterostructures (HSs). The intensity of CPPL was found to strongly depend on the electric field applied to the HSs. The CPPL was also found to enhance with decreasing LT. It was demonstrated that the observed LT dependence might be due to the LT-dependent band-gap shift of the HS materials.

Effect of conduction band nonparabolicity on the optical properties in ...

Indian Academy of Sciences (India)

the bulk conduction band edge, the correction due to nonparabolicity can be important. [9,10]. In a narrow QW under a strong magnetic field, the optical absorption coefficients calculated with the nonparabolicity correction shows remarkable deviation from results obtained using parabolic energy approximation [11].

Optical properties of ZnTe epilayers with submonolayer planar narrow gap inclusions

Energy Technology Data Exchange (ETDEWEB)

Agekian, V. F.; Filosofov, N. G., E-mail: n.filosofov@spbu.ru; Serov, A. Yu. [St. Petersburg State University, Universitetskaya nab. 7 – 9, 199034 Si. Petersburg (Russian Federation); Shtrom, I. V. [St. Petersburg State University, Universitetskaya nab. 7 – 9, 199034 Si. Petersburg (Russian Federation); Ioffe Physicotechnical Institute, Russian Academy of Sciences, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); St. Petersburg Academic University — Nanotechnology Research and Education Centre, Russian Academy of Sciences, Khlopina 8/3, 194021 St. Petersburg (Russian Federation); Karczewski, G. [Institute of Physics Polish Academy of Science, Ał. Lotnikov 32/46, 02-668 Warsaw (Poland)

2016-06-17

The exciton luminescence of ZnTe matrices with the embedded CdTe submonolayer inclusions is investigated. It is shown that the exciton localized by CdTe narrow gap component dominates in the emission spectrum. These localized excitons are coupled mainly with the phonons belonging to the cadmium enriched layers. The real distribution of cadmium in the direction of the heterostructure growth is determined from the energy position of the localized exciton emission bands.

MULTI-WAVELENGTH AFTERGLOWS OF FAST RADIO BURSTS

International Nuclear Information System (INIS)

Yi, Shuang-Xi; Gao, He; Zhang, Bing

2014-01-01

The physical origin of fast radio bursts (FRBs) is unknown. Detecting electromagnetic counterparts to FRBs in other wavelengths is essential to measure their distances and to determine their physical origin. Assuming that at least some of them are of cosmological origin, we calculate their afterglow light curves in multiple wavelengths (X-rays, optical, and radio) by assuming a range of total kinetic energies and redshifts. We focus on forward shock emission, but also consider the possibility that some of the FRBs might have bright reverse shock emission. In general, FRB afterglows are too faint to be detected by current detectors. Only if an FRB has a very low radiative efficiency in radio (hence, a very large kinetic energy), and when it is close enough to observe can its afterglow be detected in the optical and radio bands. We discuss observational strategies for detecting these faint afterglows using future telescopes such as Large Synoptic Survey Telescope and Expanded Very Large Array

Diode laser in-band pumped, efficient 1645 nm continuous-wave and Q-switched Er:YLuAG lasers with near-diffraction-limited beam quality

International Nuclear Information System (INIS)

Li, Jing; Yang, SuHui; He, Tao

2014-01-01

Fiber-like Er:YLuAG laser rods were tested for continuous-wave (CW) and Q-switched operation. Two narrow-band laser diodes emitting at 1532 nm were used as pump sources. The pump power was confined in the laser rods via total internal reflection. In CW mode, a maximum output power of 7.2 W was measured from a 30 mm long Er:YLuAG laser rod, corresponding to an optical–optical efficiency of 26% and a slope efficiency of 78%. Er:YLuAG and Er:YAG lasers were compared experimentally and exhibited comparable performance, while the measured central wavelength of the Er:YLuAG laser was 1644.75 nm, slightly longer than the central wavelength of the Er:YAG laser in the same experimental circumstances. In Q-switched mode, an output energy of 3.5 mJ was obtained from a 25 mm Er:YLuAG laser rod with a pulse duration of 100 ns and a pulse repetition frequency of 100 Hz. The pulsed output had near-diffraction-limited beam quality with M 2 values of 1.13 and 1.11 in the x and y directions, respectively. (letter)

Wavelength modulation spectroscopy of semiconductors

Energy Technology Data Exchange (ETDEWEB)

Kohn, S.E.

1977-10-01

The use of modulation spectroscopy to study the electronic properties of solids has been very productive. The construction of a wide range Wavelength Modulation Spectrometer to study the optical properties of solids is described in detail. Extensions of the working range of the spectrometer into the vacuum ultraviolet are discussed. Measurements of the reflectivity and derivative reflectivity spectra of the lead chalcogenides, the chalcopyrite ZnGeP/sub 2/, the layer compounds GaSe and GaS and their alloys, the ferroelectric SbSI, layer compounds SnS/sub 2/ and SnSe/sub 2/, and HfS/sub 2/ were made. The results of these measurements are presented along with their interpretation in terms of band structure calculations.

Dual-band absorber for multispectral plasmon-enhanced infrared photodetection

International Nuclear Information System (INIS)

Yu, Peng; Ashalley, Eric; Wang, Zhiming; Wu, Jiang; Govorov, Alexander

2016-01-01

For most of the reported metamaterial absorbers, the peak absorption only occurs at one single wavelength. Here, we investigated a dual-band absorber which is based on simple gold nano-rings. Two absorption peaks can be readily achieved in 3–5 µ m and 8–14 µ m via tuning the width and radius of gold nano-rings and dielectric constant. The average maximum absorption of two bands can be as high as 95.1% (−0.22 dB). Based on the simulation results, the perfect absorber with nano-rings demonstrates great flexibility to create dual-band or triple-band absorption, and thus holds potential for further applications in thermophotovoltaics, multicolor infrared focal plane arrays, optical filters, and biological sensing applications. (paper)

Information retrieval from wide-band meteorological data - An example

Science.gov (United States)

Adelfang, S. I.; Smith, O. E.

1983-01-01

The methods proposed by Smith and Adelfang (1981) and Smith et al. (1982) are used to calculate probabilities over rectangles and sectors of the gust magnitude-gust length plane; probabilities over the same regions are also calculated from the observed distributions and a comparison is also presented to demonstrate the accuracy of the statistical model. These and other statistical results are calculated from samples of Jimsphere wind profiles at Cape Canaveral. The results are presented for a variety of wavelength bands, altitudes, and seasons. It is shown that wind perturbations observed in Jimsphere wind profiles in various wavelength bands can be analyzed by using digital filters. The relationship between gust magnitude and gust length is modeled with the bivariate gamma distribution. It is pointed out that application of the model to calculate probabilities over specific areas of the gust magnitude-gust length plane can be useful in aerospace design.

A chip-scale, telecommunications-band frequency conversion interface for quantum emitters.

Science.gov (United States)

Agha, Imad; Ates, Serkan; Davanço, Marcelo; Srinivasan, Kartik

2013-09-09

We describe a chip-scale, telecommunications-band frequency conversion interface designed for low-noise operation at wavelengths desirable for common single photon emitters. Four-wave-mixing Bragg scattering in silicon nitride waveguides is used to demonstrate frequency upconversion and downconversion between the 980 nm and 1550 nm wavelength regions, with signal-to-background levels > 10 and conversion efficiency of ≈ -60 dB at low continuous wave input pump powers ( 25 % in existing geometries. Finally, we present waveguide designs that can be used to connect shorter wavelength (637 nm to 852 nm) quantum emitters with 1550 nm.

Double wavelength differential absorption as a technique for early diagnosis of breast cancer

Science.gov (United States)

Liger, Vladimir V.; Zybin, Alexander V.; Niemax, Kay; Kuritsyn, Yuri A.; Bolshov, Mikhail A.

2005-08-01

The double-wavelength differential molecular absorption technique with diode lasers is proposed for sensitive detection of functional status of breast tissues. The method is based on the measurement of the transmitted intensity differences of the two beams of diode lasers tuned to selected wavelengths within a broad absorption band of a human breast tissue within 700 - 800 nm spectral range. The strategy for the optimum selection of the diode laser wavelengths and initial adjustment of the detection scheme is developed. The method is demonstrated by the detection of the relative concentrations of two dyes, the optical properties of which are similar to those of a mixture of oxy- and deoxy- hemoglobin. The results of the first clinical tests of the proposed technique are briefly described.

Fan-shaped antennas: Realization of wideband characteristics and generation of stop bands

Science.gov (United States)

Nakano, H.; Morishita, K.; Iitsuka, Y.; Mimaki, H.; Yoshida, T.; Yamauchi, J.

2008-08-01

This paper presents four fan-shaped antennas: U.S.-FAN, CROSS-FAN, CROSS-FAN-W, and CROSS-FAN-S. Each of these antennas stands upright above a ground plane, and has edges expressed by an exponential function and a circle function. The four antennas are investigated using frequencies from 1.5 GHz to 11 GHz. The CROSS-FAN is found to have a lower VSWR over a wide frequency band compared to the U.S.-FAN. The CROSS-FAN-W and CROSS-FAN-S are modified versions of the CROSS-FAN, each designed to have a stop band (a high VSWR frequency range) for interference cancellation. The stop band for the CROSS-FAN-W is controlled by a wire (total length 4Lwire) that connects the fan-shaped elements. The center frequency of the stop band fstop is close to the frequency corresponding to a wire segment length Lwire of half the wavelength. It is also found that the stop band in the CROSS-FAN-S can be controlled by four slots, one cut into each of the fan-shaped elements. The center frequency of the stop band fstop is close to the frequency corresponding to a slot length Lslot of one-quarter of the wavelength. Experimental work is performed to confirm the theoretical results, using the CROSS-FAN-S.

Ozone and ultraviolet-B irradiances: experimental determination of the radiation amplification factor

International Nuclear Information System (INIS)

Blumthaler, M.; Salzgeber, M.; Ambach, W.

1995-01-01

During the period 1981-1993, measurements of solar UV irradiances were made at the High-Alpine Research Station Jungfraujoch (Switzerland, 3576 m a.s.l.) to determine the radiation amplification factor (RAF) for the Robertson-Berger sunburn meter and for the narrow-band wavelength ranges of the Eppley filter spectrometer. The Robertson-Berger sunburn meter model 500 showed a RAF of 1.07 ± 0.15 at solar elevations between 20 o and 60 o . The RAF for human erythema is 1.1 in comparison. Therefore the Robertson-Berger sunburn meter is suitable to measure the influence of total atmospheric ozone variations on the effective erythemal irradiance. In the narrow-band wavelength ranges of the Eppley filter spectrometer the RAF increases greatly at shorter wavelengths with RAF of 1.06, 1.40 and 2.35 for the optical centers 315.1 nm, 311.1 nm and 305.2 nm, evaluated at 30 o solar elevation. In order to minimize perturbations by aerosol optical depth and albedo in the evaluation of the RAF the ratios of UV irradiances to total irradiances were evaluated. (Author)

Model Development for MODIS Thermal Band Electronic Crosstalk

Science.gov (United States)

Chang, Tiejun; Wu, Aisheng; Geng, Xu; Li, Yonghonh; Brinkman, Jake; Keller, Graziela; Xiong, Xiaoxiong

2016-01-01

MODerate-resolution Imaging Spectroradiometer (MODIS) has 36 bands. Among them, 16 thermal emissive bands covering a wavelength range from 3.8 to 14.4 m. After 16 years on-orbit operation, the electronic crosstalk of a few Terra MODIS thermal emissive bands developed substantial issues that cause biases in the EV brightness temperature measurements and surface feature contamination. The crosstalk effects on band 27 with center wavelength at 6.7 m and band 29 at 8.5 m increased significantly in recent years, affecting downstream products such as water vapor and cloud mask. The crosstalk effect is evident in the near-monthly scheduled lunar measurements, from which the crosstalk coefficients can be derived. The development of an alternative approach is very helpful for independent verification.In this work, a physical model was developed to assess the crosstalk impact on calibration as well as in Earth view brightness temperature retrieval. This model was applied to Terra MODIS band 29 empirically to correct the Earth brightness temperature measurements. In the model development, the detectors nonlinear response is considered. The impact of the electronic crosstalk is assessed in two steps. The first step consists of determining the impact on calibration using the on-board blackbody (BB). Due to the detectors nonlinear response and large background signal, both linear and nonlinear coefficients are affected by the crosstalk from sending bands. The second step is to calculate the effects on the Earth view brightness temperature retrieval. The effects include those from affected calibration coefficients and the contamination of Earth view measurements. This model links the measurement bias with crosstalk coefficients, detector non-linearity, and the ratio of Earth measurements between the sending and receiving bands. The correction of the electronic cross talk can be implemented empirically from the processed bias at different brightness temperature. The implementation

Narrow-band light emission from a single carbon nanotube p-n diode

Science.gov (United States)

Kinoshita, Megumi; Mueller, Thomas; Steiner, Mathias; Perebeinos, Vasili; Bol, Ageeth; Farmer, Damon; Avouris, Phaedon

2010-03-01

We present the first observation of electroluminescence from electrostatically-generated carbon nanotube (CNT) p-n junctions[1]. While CNT optoelectronics has made much progress in recent years, observations of emission from electrically excited CNT devices have been limited to the high-bias regime and with low efficiency. Furthermore, the resulting broad linewidths are broad, making it difficult to investigate electronic levels and carrier dynamics. We find that p-n junctions allow for better carrier control at lower power inputs, resulting in emission with near-zero threshold, low self-heating and efficiency two to three orders of magnitude greater compared to previous device configurations. This yields higher signal-to-noise ratio and narrower linewidths (down to ˜35 meV) that allows us to identify localized excitonic transitions that have previously been observed only in photoluminescent studies. [1] T. Mueller, M. Kinoshita, M. Steiner, V. Perebeinos, A. Bol, D. Farmer, and Ph. Avouris, Nature Nanotech., web publication, November 15 2009.

Temperature dependence of active photonic band gap in bragg-spaced quantum wells

Energy Technology Data Exchange (ETDEWEB)

Hu Zhiqiang; Wang Tao; Yu Chunchao; Xu Wei, E-mail: huzhiqianghzq@163.com [Wuhan National Laboratory for Optoelectronics, College of Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China)

2011-02-01

A novel all-optical polarization switch of active photonic band gap structure based on non-resonant optical Stark effect bragg-spaced quantum wells was investigated and it could be compatible with the optical communication system. The theory is based on InGaAsP/InP Bragg-spaced quantum wells (BSQWs). Mainly through the design of the InGaAsP well layer component and InP barrier thickness to make the quantum-period cycle meet the bragg condition and the bragg frequency is equal to re-hole exciton resonance frequency. When a spectrally narrow control pulse is tuned within the forbidden gap, such BSQWs have been shown to exhibit large optical nonlinearities and ps recovery times, which can form T hz switch. However, the exciton binding energy of InGaAsP will be automatically separate at room temperature, so the effect of all-optical polarization switching of active photonic band gap bragg structure quantum wells can only be studied at low temperature. By a large number of experiments, we tested part of the material parameters of BSQWs in the temperature range 10-300K. On this basis, the InGaAsP and InP refractive index changes with wavelength, InP thermal expansion coefficient are studied and a relationship equation is established. Experimental results show that the bragg reflection spectra with temperature mainly is effected by InP refractive index changes with temperature. Our theoretical study and experiment are an instruction as a reference in the designs and experiments of future practical optical switches.

Temperature dependence of active photonic band gap in bragg-spaced quantum wells

International Nuclear Information System (INIS)

Hu Zhiqiang; Wang Tao; Yu Chunchao; Xu Wei

2011-01-01

A novel all-optical polarization switch of active photonic band gap structure based on non-resonant optical Stark effect bragg-spaced quantum wells was investigated and it could be compatible with the optical communication system. The theory is based on InGaAsP/InP Bragg-spaced quantum wells (BSQWs). Mainly through the design of the InGaAsP well layer component and InP barrier thickness to make the quantum-period cycle meet the bragg condition and the bragg frequency is equal to re-hole exciton resonance frequency. When a spectrally narrow control pulse is tuned within the forbidden gap, such BSQWs have been shown to exhibit large optical nonlinearities and ps recovery times, which can form T hz switch. However, the exciton binding energy of InGaAsP will be automatically separate at room temperature, so the effect of all-optical polarization switching of active photonic band gap bragg structure quantum wells can only be studied at low temperature. By a large number of experiments, we tested part of the material parameters of BSQWs in the temperature range 10-300K. On this basis, the InGaAsP and InP refractive index changes with wavelength, InP thermal expansion coefficient are studied and a relationship equation is established. Experimental results show that the bragg reflection spectra with temperature mainly is effected by InP refractive index changes with temperature. Our theoretical study and experiment are an instruction as a reference in the designs and experiments of future practical optical switches.

Colloid bands in silver chloride induced by reactor irradiation at low temperature

International Nuclear Information System (INIS)

Atobe, K.; Okada, M.; Nakagawa, M.

1978-01-01

It is well known that no trapped electron center exists stably in irradiated silver chlorides even at low temperatures. On the other hand, irradiation by ultra-violet light at room temperature produces a broad absorption (colloid bands) on the long wavelength side of the fundamental absorption. In this report, it is shown that one of the colloid bands appears in undoped AgCl crystals by reactor irradiation at low temperature (20 K) and the other colloid band by thermal annealing after the irradiation. The relation between the bands, which correspond to two types of colloidal silver, is represented. (author)

Investigation of mucosal pattern of gastric antrum using magnifying narrow-band imaging in patients with chronic atrophic fundic gastritis.

Science.gov (United States)

Yamasaki, Yasushi; Uedo, Noriya; Kanzaki, Hiromitsu; Kato, Minoru; Hamada, Kenta; Aoi, Kenji; Tonai, Yusuke; Matsuura, Noriko; Kanesaka, Takashi; Yamashina, Takeshi; Akasaka, Tomofumi; Hanaoka, Noboru; Takeuchi, Yoji; Higashino, Koji; Ishihara, Ryu; Tomita, Yasuhiko; Iishi, Hiroyasu

2017-01-01

Magnifying narrow-band imaging (M-NBI) can reportedly help predict the presence and distribution of atrophy and intestinal metaplasia in the gastric corpus. However, the micro-mucosal pattern of the antrum shown by M-NBI differs from that of the corpus. We studied the distribution and histology of the micro-mucosal pattern in the antrum based on magnifying endoscopy. Endoscopic images of the greater curvature of the antrum were evaluated in 50 patients with chronic atrophic fundic gastritis (CAFG). The extent of CAFG was evaluated by autofluorescence imaging. The micro-mucosal pattern was evaluated by M-NBI and classified into groove and white villiform types. The localization of white villiform type mucosa was classified into three types in relation to the areae gastricae : null, central, and segmental types. Biopsies were taken from regions showing different micro-mucosal patterns. Associations among the extent of CAFG, micro-mucosal pattern, and histology were examined. As the extent of CAFG increased, the proportion of white villiform type mucosa increased, whereas that of groove type mucosa decreased (P=0.022). In patients with extensive CAFG, most of the areae gastricae was composed of the segmental or central type of white villiform type mucosa (P=0.044). The white villiform type mucosa had significantly higher grades of atrophy (P=0.002) and intestinal metaplasia (P<0.001) than did the groove type mucosa. White villiform type mucosa is indicative of atrophy and intestinal metaplasia in the gastric antrum. It extends to the whole or central part of the areae gastricae as CAFG becomes more extensive.

Experimental study of shear bands formation in a granular material

Directory of Open Access Journals (Sweden)

Nguyen Thai Binh

2017-01-01

Full Text Available We present an experimental investigation of the formation of shear bands in a granular sample submitted to a biaxial test. Our principal result is the direct observation of the bifurcation at the origin of the localization process in the material. At the bifurcation, the shear band is spatially extended: we observe a breaking of symmetry without any sudden localization of the deformation in a narrow band. Our work thus allows to clearly distinguish different phenomena: bifurcation which is a ponctual event which occurs before the peak, localization which is a process that covers a range of deformation of several percents during which the peak occurs and finally stationary shear bands which are well-defined permanent structures that can be observed at the end of the localization process, after the peak.

Spectral narrowing of a 980 nm tapered diode laser bar

Science.gov (United States)

Vijayakumar, Deepak; Jensen, Ole Bjarlin; Lucas Leclin, Ga"lle; Petersen, Paul Michael; Thestrup, Birgitte

2011-03-01

High power diode laser bars are interesting in many applications such as solid state laser pumping, material processing, laser trapping, laser cooling and second harmonic generation. Often, the free running laser bars emit a broad spectrum of the order of several nanometres which limit their scope in wavelength specific applications and hence, it is vital to stabilize the emission spectrum of these devices. In our experiment, we describe the wavelength narrowing of a 12 element 980 nm tapered diode laser bar using a simple Littman configuration. The tapered laser bar which suffered from a big smile has been "smile corrected" using individual phase masks for each emitter. The external cavity consists of the laser bar, both fast and slow axis micro collimators, smile correcting phase mask, 6.5x beam expanding lens combination, a 1200 lines/mm reflecting grating with 85% efficiency in the first order, a slow axis focusing cylindrical lens of 40 mm focal length and an output coupler which is 10% reflective. In the free running mode, the laser emission spectrum was 5.5 nm wide at an operating current of 30A. The output power was measured to be in excess of 12W. Under the external cavity operation, the wavelength spread of the laser could be limited to 0.04 nm with an output power in excess of 8 W at an operating current of 30A. The spectrum was found to be tuneable in a range of 16 nm.

A Unifying Perspective on Oxygen Vacancies in Wide Band Gap Oxides.

Science.gov (United States)

Linderälv, Christopher; Lindman, Anders; Erhart, Paul

2018-01-04

Wide band gap oxides are versatile materials with numerous applications in research and technology. Many properties of these materials are intimately related to defects, with the most important defect being the oxygen vacancy. Here, using electronic structure calculations, we show that the charge transition level (CTL) and eigenstates associated with oxygen vacancies, which to a large extent determine their electronic properties, are confined to a rather narrow energy range, even while band gap and the electronic structure of the conduction band vary substantially. Vacancies are classified according to their character (deep versus shallow), which shows that the alignment of electronic eigenenergies and CTL can be understood in terms of the transition between cavity-like localized levels in the large band gap limit and strong coupling between conduction band and vacancy states for small to medium band gaps. We consider both conventional and hybrid functionals and demonstrate that the former yields results in very good agreement with the latter provided that band edge alignment is taken into account.

Negative refraction by a planar Ag/SiO2 multilayer at ultraviolet wavelength to the limit of silver

Directory of Open Access Journals (Sweden)

J. Zhao

2014-04-01

Full Text Available For planar structured hyperbolic metamaterial, the shortest wavelength achievable for negative refraction is often limited by dielectric layers, which are usually wide band gap semiconductors that absorb light strongly at wavelength shorter than their absorption edge. Here we proposed that using SiO2 may break such limitation based on effective medium theory. Through calculation and simulation we demonstrated broad angle negative refraction by a planar Ag/SiO2 layered structure at wavelength down to 326 nm. Its imaging and focusing abilities were also presented. The lower limit of wavelength here is defined by the property of silver, whose permittivity turns positive below 324 nm.

Band structure of Mgsub(x)Znsub(1-x)Te alloys

International Nuclear Information System (INIS)

Laugier, A.; Montegu, B.; Barbier, D.; Chevallier, J.; Guillaume, J.C.; Somogyi, K.

1980-01-01

The band structure of Mgsub(x)Znsub(1-x)Te alloys is studied using a double beam wavelength modulated system in first derivative mode. Modulated reflectivity measurements are made from 82 to 300 K within spectral range 2500 to 5400 A. Structures corresponding to the E 0 , E 0 + Δ 0 , E 1 , E 1 + Δ 1 , e 1 and e 1 + Δ 1 critical points are indexed on the basis of existing band calculations for ZnTe. (author)

A Multi-Wavelength Thermal Infrared and Reflectance Scene Simulation Model

Science.gov (United States)

Ballard, J. R., Jr.; Smith, J. A.; Smith, David E. (Technical Monitor)

2002-01-01

Several theoretical calculations are presented and our approach discussed for simulating overall composite scene thermal infrared exitance and canopy bidirectional reflectance of a forest canopy. Calculations are performed for selected wavelength bands of the DOE Multispectral Thermal Imagery and comparisons with atmospherically corrected MTI imagery are underway. NASA EO-1 Hyperion observations also are available and the favorable comparison of our reflective model results with these data are reported elsewhere.

Optimization of band-pass filtering parameters of a Raman lidar detecting atmospheric water vapor

International Nuclear Information System (INIS)

Cao, Kai-Fa; Hu, Shun-Xing; Wang, Ying-jian

2012-01-01

It is very important for daytime Raman lidar measurement of water vapor to determine the parameters of a band-pass filter, which are pertinent to the lidar signal to noise ratio (SNR). The simulated annealing (SA) algorithm method has an advantage in finding the extremum of a certain cost function. In this paper, the Raman spectrum of water vapor is simulated and then a first realization of a simulated annealing algorithm in the optimization of a band-pass filter of a Raman lidar system designed to detect daytime water vapor is presented. The simulated results indicate that the narrow band-pass filter has higher SNR than the wide filter does but there would be an increase in the temperature sensitivity of a narrowband Raman water vapor lidar in the upper troposphere. The numerical simulation indicates that the magnitude of the temperature dependent effect can reach 3.5% or more for narrow band-pass Raman water vapor measurements so it is necessary to consider a new water vapor Raman lidar equation that permits the temperature sensitivity of these equations to be confined to a single term. (paper)

Frequency-bin entanglement of ultra-narrow band non-degenerate photon pairs

Science.gov (United States)

Rieländer, Daniel; Lenhard, Andreas; Jime`nez Farìas, Osvaldo; Máttar, Alejandro; Cavalcanti, Daniel; Mazzera, Margherita; Acín, Antonio; de Riedmatten, Hugues

2018-01-01

We demonstrate frequency-bin entanglement between ultra-narrowband photons generated by cavity enhanced spontaneous parametric down conversion. Our source generates photon pairs in widely non-degenerate discrete frequency modes, with one photon resonant with a quantum memory material based on praseodymium doped crystals and the other photon at telecom wavelengths. Correlations between the frequency modes are analyzed using phase modulators and narrowband filters before detection. We show high-visibility two photon interference between the frequency modes, allowing us to infer a coherent superposition of the modes. We develop a model describing the state that we create and use it to estimate optimal measurements to achieve a violation of the Clauser-Horne (CH) Bell inequality under realistic assumptions. With these settings we perform a Bell test and show a significant violation of the CH inequality, thus proving the entanglement of the photons. Finally we demonstrate the compatibility with a quantum memory material by using a spectral hole in the praseodymium (Pr) doped crystal as spectral filter for measuring high-visibility two-photon interference. This demonstrates the feasibility of combining frequency-bin entangled photon pairs with Pr-based solid state quantum memories.

The 14 mu m band of carbon stars

NARCIS (Netherlands)

Yamamura, [No Value; de Jong, T; Waters, LBFM; Cami, J; Justtanont, K; LeBertre, T; Lebre, A; Waelkens, C

1999-01-01

We have studied the absorption bands around 14 mum in the spectra of 11 carbon stars with mass-loss rates ranging from 10(-8) to 10(-4) M-circle dot yr(-1), based on data obtained with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). All stars clearly show a

Quantitative analysis of X-band weather radar attenuation correction accuracy

NARCIS (Netherlands)

Berne, A.D.; Uijlenhoet, R.

2006-01-01

At short wavelengths, especially C-, X-, and K-band, weather radar signals arc attenuated by the precipitation along their paths. This constitutes a major source of error for radar rainfall estimation, in particular for intense precipitation. A recently developed stochastic simulator of range

Long wavelength stimulated emission up to 9.5 μm from HgCdTe quantum well heterostructures

Energy Technology Data Exchange (ETDEWEB)

Morozov, S. V.; Rumyantsev, V. V., E-mail: rumyantsev@ipmras.ru; Dubinov, A. A.; Kudryavtsev, K. E.; Antonov, A. V.; Gavrilenko, V. I. [Institute for Physics of Microstructures of Russian Academy of Sciences, 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Kadykov, A. M. [Institute for Physics of Microstructures of Russian Academy of Sciences, 603950 Nizhny Novgorod (Russian Federation); UMR CNRS 5221, GIS-TERALAB, Université Montpellier II, 34095 Montpellier (France); Mikhailov, N. N. [A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Dvoretskii, S. A. [A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk (Russian Federation)

2016-02-29

Stimulated emission from waveguide HgCdTe structures with several quantum wells inside waveguide core is demonstrated at wavelengths up to 9.5 μm. Photoluminescence line narrowing down to kT energy, as well as superlinear rise in its intensity evidence the onset of the stimulated emission, which takes place under optical pumping with intensity as small as ∼0.1 kW/cm{sup 2} at 18 K and 1 kW/cm{sup 2} at 80 K. One can conclude that HgCdTe structures potential for long-wavelength lasers is not exhausted.

MIT wavelength tables. Volume 2. Wavelengths by element

International Nuclear Information System (INIS)

Phelps, F.M. III.

1982-01-01

This volume is the first stage of a project to expand and update the MIT wavelength tables first compiled in the 1930's. For 109,325 atomic emission lines, arranged by element, it presents wavelength in air, wavelength in vacuum, wave number and intensity. All data are stored on computer-readable magnetic tape

DTPA: Bis benzimidazole as multi model imaging agent

International Nuclear Information System (INIS)

Srivastava, Vikas; Tiwari, A.K.; Sharma, H.; Sharma, R.; Mishra, A.K.

2010-01-01

Full text: The DTPA bis benzimidazole analogue has been tested for radiopharmaceutical efficacy. The radiolabelling was found more then 98% after 8 hrs and blood kinetics was fast. The compound was also tested for optical imaging agent. The Eu 3+ ion has an absorption band in the visible spectrum (578-582 nm) whose wavelength is very sensitive to even small changes in the coordination environment. Although the intensity of this 7F0 → 5D0 transition is low, the bands are relatively narrow, which allows distinguishing different coordination states of the metal. For Eu 3+ complexes which have two differently hydrated forms in aqueous solution, one observes two absorption bands belonging to the two species. High-resolution UV-visible spectra were recorded in aqueous solutions which show a temperature invariant absorption with two distinct, temperature-dependent absorption bands. The intensity ratio of these two bands changes with temperature: the band at shorter wavelengths is decreasing very slightly, while that at longer wavelengths is increasing with the temperature. The ratio of the integrals of the two bands is related to the equilibrium constant, and its temperature dependence yields the reaction enthalpy and entropy

Narrow band gap and visible light-driven photocatalysis of V-doped Bi{sub 6}Mo{sub 2}O{sub 15} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Xu, Jian; Qin, Chuanxiang; Huang, Yanlin [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Wang, Yaorong, E-mail: yrwang@suda.edu.cn [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Qin, Lin [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

2017-02-28

Highlights: • V{sup 5+}-doped Bi{sub 6}Mo{sub 2}O{sub 15} was synthesized by the electrospinning preparation. • The band gap energy of Bi{sub 6}Mo{sub 2}O{sub 15} was greatly reduced by V-doping in the lattices. • V-doped Bi{sub 6}Mo{sub 2}O{sub 15} shows high activity in RhB degradation under visible light. • Crystal structure of Bi{sub 6}Mo{sub 2}O{sub 15} is favorable for high photocatalytic capacity. - Abstract: Pure and V{sup 5+}-doped Bi{sub 6}Mo{sub 2}O{sub 15} (3Bi{sub 2}O{sub 3}·2MoO{sub 3}) photocatalysts were synthesized through electrospinning, followed by low-temperature heat treatment. The samples developed into nanoparticles with an average size of approximately 50 nm. The crystalline phases were verified via X-ray powder diffraction measurements (XRD). The surface properties of the photocatalysts were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses. The UV–vis spectra showed that V doping in Bi{sub 6}Mo{sub 2}O{sub 15} shifted the optical absorption from the UV region to the visible-light wavelength region. The energy of the band gap of Bi{sub 6}Mo{sub 2}O{sub 15} was reduced by V doping in the lattices. The photocatalytic activities of the pure and V-doped Bi{sub 6}Mo{sub 2}O{sub 15} were tested through photodegradation of rhodamine B (RhB) dye solutions under visible light irradiation. Results showed that 20 mol% V-doped Bi{sub 6}Mo{sub 2}O{sub 15} achieved efficient photocatalytic ability. RhB could be degraded by V-doped Bi{sub 6}Mo{sub 2}O{sub 15} in 2 h. The photocatalytic activities and mechanisms were discussed according to the characteristics of the crystal structure and the results of EIS and XPS measurements.

The new MQ/AAO/Strasbourg multi-wavelength and spectroscopic PNe database: MASPN

Science.gov (United States)

Parker, Quentin Andrew; Bojicic, Ivan; Frew, David; Acker, Agnes; Ochsenbein, Francois; MASPN Database Team

2015-01-01

We are in a new golden age of PN discovery. This is thanks in particular to high sensitivity, wide-field, narrow-band surveys of the Galactic plane undertaken on the UKST in Australia and the Isaac Newton telescope on La Palma. Together these telescopes and their H-alpha surveys have provided very significant Planetary Nebulae (PNe) discoveries that have more than doubled the totals accrued by all telescopes over the previous 250 years. However, these PNe are not simply more of the same found in previous catalogues. Most new PNe are more obscured, evolved and of lower surface brightness than previous compilations while others are faint but compact and more distant. This has required an extensive and time-consuming programme of spectroscopic confirmation on a variety of 2m and 4m telescopes that is now largely complete. The scope of any future large-scale PNe studies, particularly those of a statistical nature or undertaken to understand true PNe diversity and evolution should now reflect this fresh PN population landscape of the combined sample of ~3500 Galactic PNe now available. Such studies should be coloured and nuanced by these recent major discoveries and the massive, high sensitivity, high resolution, multi-wavelength imaging surveys now available across much of the electromagnetic spectrum.Following this motivation we provide, for the first time, an accessible, reliable, on-line "one-stop" SQL database for essential, up-to date information for all known Galactic PN. We have attempted to: i) Reliably remove the many PN mimics/false ID's that have biased previous compilations and subsequent studies; ii) Provide accurate, updated positions, sizes, morphologies, radial velocities, fluxes, multi-wavelength imagery and spectroscopy; iii) Link to CDS/Vizier and hence provide archival history for each object; iv) Provide an interface to sift, select, browse, collate, investigate, download and visualise the complete currently known Galactic PNe diaspora and v

Wavelength converter technology

DEFF Research Database (Denmark)

Kloch, Allan; Hansen, Peter Bukhave; Poulsen, Henrik Nørskov

1999-01-01

Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on all-optical wavelength converter types based on semiconductor optical amplifiers.......Wavelength conversion is important since it ensures full flexibility of the WDM network layer. Progress in optical wavelength converter technology is reviewed with emphasis on all-optical wavelength converter types based on semiconductor optical amplifiers....

Multi-wavelength mid-IR light source for gas sensing

Science.gov (United States)

Karioja, Pentti; Alajoki, Teemu; Cherchi, Matteo; Ollila, Jyrki; Harjanne, Mikko; Heinilehto, Noora; Suomalainen, Soile; Viheriälä, Jukka; Zia, Nouman; Guina, Mircea; Buczyński, Ryszard; Kasztelanic, Rafał; Kujawa, Ireneusz; Salo, Tomi; Virtanen, Sami; Kluczyński, Paweł; Sagberg, Hâkon; Ratajczyk, Marcin; Kalinowski, Przemyslaw

2017-02-01

Cost effective multi-wavelength light sources are key enablers for wide-scale penetration of gas sensors at Mid-IR wavelength range. Utilizing novel Mid-IR Si-based photonic integrated circuits (PICs) filter and wide-band Mid-IR Super Luminescent Light Emitting Diodes (SLEDs), we show the concept of a light source that covers 2.5…3.5 μm wavelength range with a resolution of price can be lowered in high volumes by utilizing tailored molded IR lens technology and automated packaging and assembling technologies. The status of the development of the key components of the light source are reported. The PIC is based on the use of micron-scale SOI technology, SLED is based on AlGaInAsSb materials and the lenses are tailored heavy metal oxide glasses fabricated by the use of hot-embossing. The packaging concept utilizing automated assembly tools is depicted. In safety and security applications, the Mid-IR wavelength range covered by the novel light source allows for detecting several harmful gas components with a single sensor. At the moment, affordable sources are not available. The market impact is expected to be disruptive, since the devices currently in the market are either complicated, expensive and heavy instruments, or the applied measurement principles are inadequate in terms of stability and selectivity.

Fractal Based Triple Band High Gain Monopole Antenna

Science.gov (United States)

Pandey, Shashi Kant; Pandey, Ganga Prasad; Sarun, P. M.

2017-10-01

A novel triple-band microstrip fed planar monopole antenna is proposed and investigated. A fractal antenna is created by iterating a narrow pulse (NP) generator model at upper side of modified ground plane, which has a rhombic patch, for enhancing the bandwidth and gain. Three iterations are carried out to study the effects of fractal geometry on the antenna performance. The proposed antenna can operate over three frequency ranges viz, 3.34-4.8 GHz, 5.5-10.6 GHz and 13-14.96 GHz suitable for WLAN 5.2/5.8 GHz, WiMAX 3.5/5.5 GHz and X band applications respectively. Simulated and measured results are in good agreements with each others. Results show that antenna provides wide/ultra wide bandwidths, monopole like radiation patterns and very high antenna gains over the operating frequency bands.

Determination of band-structure parameters of Pbsub(1-x)Snsub(x)Te narrow-gap semiconductor from infrared Faraday rotation

International Nuclear Information System (INIS)

Sizov, F.F.; Lashkarev, G.V.; Martynchuk, E.K.

1977-01-01

The temeprature dependences of Faraday rotation in Pbsub(1-x)Snsub(x)Te of p type with the hole density 3x10 16 -2.2x10 18 cm -3 are studied in the range 40-370 K and in the spectral interval 4-16 μm. The analysis of interband Faraday rotation confirms a conclusion made by the authors earlier that the g factor for the c band (gsub(c)) is positive, for the v band (gsub(v))-negative and that [gsub(c)] > [gsub(v)]. The temperature dependences of carrier effective masses are investigated on the basis of the two-band model. It is demonstrated that for T < 200 K the Faraday effective mass of holes near the ceiling of the valency band varies in direct proportion to the width of the forbidden band. The temperature increase of the Faraday effective mass of current carriers, which is faster than that of the effective electron mass, is discovered, and this is related to the effect of the heavy hole band

Long-wavelength stimulated emission and carrier lifetimes in HgCdTe-based waveguide structures with quantum wells

Energy Technology Data Exchange (ETDEWEB)

Rumyantsev, V. V., E-mail: rumyantsev@ipm.sci-nnov.ru; Fadeev, M. A.; Morozov, S. V.; Dubinov, A. A.; Kudryavtsev, K. E.; Kadykov, A. M. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Tuzov, I. V. [Lobachevsky State University of Nizhny Novgorod (NNSU) (Russian Federation); Dvoretskii, S. A.; Mikhailov, N. N. [Russian Academy of Sciences, Institute for Semiconductor Physics, Siberian Branch (Russian Federation); Gavrilenko, V. I. [Novosibirsk State University (Russian Federation); Teppe, F. [Universite Montpellier II, Laboratoire Charles Coulomb (L2C) (France)

2016-12-15

The interband photoconductivity and photoluminescence in narrow-gap HgCdTe-based waveguide structures with quantum wells (QWs) (designed for long-wavelength stimulated emission under optical pumping) are investigated. The photoconductivity relaxation times in n-type structures reach several microseconds, due to which stimulated emission at a wavelength of 10.2 μm occurs at a low threshold pump intensity (~100 W/cm{sup 2}) at 20 K. In the p-type structures obtained by annealing (to increase the mercury vacancy concentration), even spontaneous emission from the QWs is not detected because of a dramatic decrease in the carrier lifetime with respect to Shockley–Read–Hall nonradiative recombination.

Infrared studies of galactic nebulae. IV - Continuum and line radiation from planetary nebulae.

Science.gov (United States)

Gillett, F. C.; Merrill, K. M.; Stein, W. A.

1972-01-01

Observations are reported of the detection of IR radiation from several planetary nebulae not previously known to be radiating at these wavelengths. Broad spectral bandwidth observations indicate that ir radiation in excess of that expected from atomic processes is a common phenomenon among these objects. Investigations with narrow spectral bandwidth show that in a few cases the energy in the 10.52-micron line is a significant fraction of the total energy observed in the broad-band measurements and in other cases a relatively small fraction of the total radiation. Other observations on two sources with narrow spectral bandwidth adjacent to the 10.52-micron line indicate that at these wavelengths a true continuum of radiation exists as well as lines. The results are discussed in relation to visual and radio-wavelength data.

A Very Compact and Low Profile UWB Planar Antenna with WLAN Band Rejection.

Science.gov (United States)

Syed, Avez; Aldhaheri, Rabah W

2016-01-01

A low-cost coplanar waveguide fed compact ultrawideband (UWB) antenna with band rejection characteristics for wireless local area network (WLAN) is proposed. The notch band characteristic is achieved by etching half wavelength C-shaped annular ring slot in the radiating patch. By properly choosing the radius and position of the slot, the notch band can be adjusted and controlled. With an overall size of 18.7 mm × 17.6 mm, the antenna turns out to be one of the smallest UWB antennas with band-notched characteristics. It has a wide fractional bandwidth of 130% (2.9-13.7 GHz) with VSWR applications.

A three-color absorption/scattering imaging technique for simultaneous measurements on distributions of temperature and fuel concentration in a spray

Science.gov (United States)

Qi, Wenyuan; Zhang, Yuyin

2018-04-01

A three-color imaging technique was proposed for simultaneous measurements on distributions of fuel/air mixture temperature and fuel vapor/liquid concentrations in evaporating sprays. The idea is based on that the vapor concentration is proportional to the absorption of vapor to UV light, the liquid-phase concentration is related to the light extinction due to scattering of droplet to visible light, and the mixture temperature can be correlated to the absorbance ratio at two absorbing wavelengths or narrow bands. For verifying the imaging system, the molar absorption coefficients of p-xylene at the three narrow bands, which were centered respectively at 265, 289, and 532 nm with FWHM of 10 nm, were measured in a specially designed calibration chamber at different temperatures (423-606 K) and pressure of 3.6 bar. It was found that the ratio of the molar absorption coefficients of p-xylene at the two narrow bands centered at the two UV wavelengths is sensitive to the mixture temperature. On the other hand, the distributions of fuel vapor/liquid concentrations can be obtained by use of absorbance due to ultraviolet absorption of vapor and visible light scattering of droplets. Combining these two methods, a simultaneous measurement on distributions of mixture temperature and fuel vapor/liquid concentrations can be realized. In addition, the temperature field obtained from the ratio of the two absorbing narrow bands can be further used to improve the measurement accuracy of vapor/liquid concentrations, because the absorption coefficients depend on temperature. This diagnostic was applied to an evaporating spray inside a high-temperature and high-pressure constant volume chamber.

A Raman spectroscopic study of organic matter in interplanetary dust particles and meteorites using multiple wavelength laser excitation

Science.gov (United States)

Starkey, N. A.; Franchi, I. A.; Alexander, C. M. O'd.

2013-10-01

Raman spectroscopy was used to investigate insoluble organic matter (IOM) from a range of chondritic meteorites, and a suite of interplanetary dust particles (IDPs). Three monochromatic excitation wavelengths (473 nm, 514 nm, 632 nm) were applied sequentially to assess variations in meteorite and IDP Raman peak parameters (carbon D and G bands) as a function of excitation wavelength (i.e., dispersion). Greatest dispersion occurs in CVs > OCs > CMs > CRs with type 3 chondrites compared at different excitation wavelengths displaying conformable relationships, in contrast to type 2 chondrites. These findings indicate homogeneity in the structural nature of type 3 chondrite IOM, while organic matter (OM) in type 2 chondrites appears to be inherently more heterogeneous. If type 2 and type 3 chondrite IOM shares a common source, then thermal metamorphism may have a homogenizing effect on the originally more heterogeneous OM. IDP Raman G bands fall on an extension of the trend displayed by chondrite IOM, with all IDPs having Raman parameters indicative of very disordered carbon, with almost no overlap with IOM. The dispersion effect displayed by IDPs is most similar to CMs for the G band, but intermediate between CMs and CRs for the D band. The existence of some overlapping Raman features in the IDPs and IOM indicates that their OM may share a common origin, but the IDPs preserve more pristine OM that may have been further disordered by ion irradiation. H, C, and N isotopic data for the IDPs reveal that the disordered carbon in IDPs corresponds with higher δ15N and lower δ13C.

Energy band dispersion in photoemission spectra of argon clusters

International Nuclear Information System (INIS)

Foerstel, Marko; Mucke, Melanie; Arion, Tiberiu; Lischke, Toralf; Barth, Silko; Ulrich, Volker; Ohrwall, Gunnar; Bjoerneholm, Olle; Hergenhahn, Uwe; Bradshaw, Alex M.

2011-01-01

Using photoemission we have investigated free argon clusters from a supersonic nozzle expansion in the photon energy range from threshold up to 28 eV. Measurements were performed both at high resolution with a hemispherical electrostatic energy analyser and at lower resolution with a magnetic bottle device. The latter experiments were performed for various mean cluster sizes. In addition to the ∼1.5 eV broad 3p-derived valence band seen in previous work, there is a sharper feature at ∼15 eV binding energy. Surprisingly for non-oriented clusters, this peak shifts smoothly in binding energy over the narrow photon energy range 15.5-17.7 eV, indicating energy band dispersion. The onset of this bulk band-like behaviour could be determined from the cluster size dependence.

Photonic band gap structures for long-range surface plasmon polaritons

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Boltasseva, Alexandra; Søndergaard, Thomas

2005-01-01

Propagation of long-range surface plasmon polaritons (LR-SPPs) along periodically thickness-modulated metal stripes embedded in dielectric is studied both theoretically and experimentally for light wavelengths in the telecom range. We demonstrate that symmetric (with respect to the film surface) nm......-size thickness variations result in the pronounced band gap effect, and obtain very good agreement between measured and simulated (transmission and reflection) spectra. This effect is exploited to realize a compact wavelength add-drop filter with the bandwidth of ~20 nm centered at 1550 nm. The possibilities...

Tunable excimer lasers

International Nuclear Information System (INIS)

Sze, R.C.

1990-01-01

The wide bandwidth nature of the rare-gas halide excimer transitions allow reasonable tuning of the laser oscillation wavelength that makes it useful for a number of applications. At the same time this wide bandwidth makes narrow band operation difficult and special techniques are needed to insure narrow frequency lasing as well as absolute frequency resettability. The author discusses briefly some of the classical frequency narrowing techniques and then goes on to some recent work that require lasers of special frequency characteristics for special applications including KrF laser fusion

The Keenan and Wing bands in S stars

International Nuclear Information System (INIS)

Lambert, D.L.; Clegg, R.E.S.

1980-01-01

New observations of the near infrared spectra of S stars are presented as part of a survey of the unidentified Keenan and Wing bands. Bandhead wavelengths accurate to 0.5 A are presented. A new band is found at 9014 A. The bands are not present in normal M giants and dwarfs. Laboratory spectroscopy of heavy element oxides is reported. Several new identifications are proposed. The 10 300 A Wing band is identified with the Δv = - 1 sequence of the ZrO 9300 A Δv = 0 bands. The ZrO B 1 PI-A 1 Δ (Δv = 0) system may be responsible for either the 9736 A or the 10 515 A Wing bands. Two new bands in the near infrared at 8219 and 8235 A are provided by CeO. A new band with heads at 7503 and 7509 A in a spectrum of R And is tentatively attributed to YS. A band at 8268 A in M stars is the TiO delta(2-1) head. The 8610 A Keenan band is not due to CrH. Potential carriers of the Keenan and Wing bands are reviewed. It is suggested that the heavy element sulphides and, perhaps, chlorides are leading candidates. Identification of YS in R And may provide the first evidence for these sulphides. ZrS is a leading candidate for which laboratory spectroscopy is needed. (author)

Calculation of electrostatic multipoles of electron localized in narrow-band InSb spherical nanolayer

International Nuclear Information System (INIS)

Amirkhanyan, S.M.; Kazaryan, E.M.; Sarkisyan, H.A.

2015-01-01

Behavior of electron in narrow-gap spherical nanolayer of InSb is considered. Dispersion law of electron is described within the double-gap Kane model, when arises a necessity for considering of Klein-Gordon equation for description of behavior of electrons and light holes. Dipole and quadrupole momentums of electron in specified systems are defined on the base of the obtained expressions. It is shown, that average value of dipole momentum equals to zero and that for definition of average value of tensor of quadrupole momentum it is enough to calculate the average value of diagonal z-component of this tensor. Electrostatic potentials and tensions of fields created by electron located in different quantum states are defined

Mass measurements on neutron-deficient nuclides at SHIPTRAP and commissioning of a cryogenic narrow-band FT-ICR mass spectrometer

Energy Technology Data Exchange (ETDEWEB)

Ferrer Garcia, R.

2007-07-01

The dissertation presented here deals with high-precision Penning trap mass spectrometry on short-lived radionuclides. Owed to the ability of revealing all nucleonic interactions, mass measurements far off the line of {beta}-stability are expected to bring new insight to the current knowledge of nuclear properties and serve to test the predictive power of mass models and formulas. In nuclear astrophysics, atomic masses are fundamental parameters for the understanding of the synthesis of nuclei in the stellar environments. This thesis presents ten mass values of radionuclides around A=90 interspersed in the predicted rp-process pathway. Six of them have been experimentally determined for the first time. The measurements have been carried out at the Penning-trap mass spectrometer SHIPTRAP using the destructive time-of-flight ion-cyclotron-resonance (TOF-ICR) detection technique. Given the limited performance of the TOF-ICR detection when trying to investigate heavy/superheavy species with small production cross sections ({sigma} <1 {mu}b), a new detection system is found to be necessary. Thus, the second part of this thesis deals with the commissioning of a cryogenic double-Penning trap system for the application of a highly-sensitive, narrow-band Fourier-transform ion-cyclotron-resonance (FT-ICR) detection technique. With the non-destructive FT-ICR detection method a single singly-charged trapped ion will provide the required information to determine its mass. First off-line tests of a new detector system based on a channeltron with an attached conversion dynode, of a cryogenic pumping barrier, to guarantee ultra-high vacuum conditions during mass determination, and of the detection electronics for the required single-ion sensitivity are reported. (orig.)

An alternative option for "resect and discard" strategy, using magnifying narrow-band imaging: a prospective "proof-of-principle" study.

Science.gov (United States)

Takeuchi, Yoji; Hanafusa, Masao; Kanzaki, Hiromitsu; Ohta, Takashi; Hanaoka, Noboru; Yamamoto, Sachiko; Higashino, Koji; Tomita, Yasuhiko; Uedo, Noriya; Ishihara, Ryu; Iishi, Hiroyasu

2015-10-01

The "resect and discard" strategy is beneficial for cost savings on screening and surveillance colonoscopy, but it has the risk to discard lesions with advanced histology or small invasive cancer (small advanced lesion; SALs). The aim of this study was to prove the principle of new "resect and discard" strategy with consideration for SALs using magnifying narrow-band imaging (M-NBI). Patients undergoing colonoscopy at a tertiary center were involved in this prospective trial. For each detected polyp <10 mm, optical diagnosis (OD) and virtual management ("leave in situ", "discard" or "send for pathology") were independently made using non-magnifying NBI (N-NBI) and M-NBI, and next surveillance interval were predicted. Histological and optical diagnosis results of all polyps were compared. While the management could be decided in 82% of polyps smaller than 10 mm, 24/31 (77%) SALs including two small invasive cancers were not discarded based on OD using M-NBI. The sensitivity [90% confidence interval (CI)] of M-NBI for SALs was 0.77 (0.61-0.89). The risk for discarding SALs using N-NBI was significantly higher than that using M-NBI (53 vs. 23%, p = 0.02). The diagnostic accuracy (95% CI) of M-NBI in distinguishing neoplastic from non-neoplastic lesions [0.88 (0.86-0.90)] was significantly better than that of N-NBI [0.84 (0.82-0.87)] (p = 0.005). The results of our study indicated that our "resect and discard" strategy using M-NBI could work to reduce the risk for discarding SALs including small invasive cancer (UMIN-CTR, UMIN000003740).

Antarctic krill under sea ice: elevated abundance in a narrow band just south of ice edge.

Science.gov (United States)

Brierley, Andrew S; Fernandes, Paul G; Brandon, Mark A; Armstrong, Frederick; Millard, Nicholas W; McPhail, Steven D; Stevenson, Peter; Pebody, Miles; Perrett, James; Squires, Mark; Bone, Douglas G; Griffiths, Gwyn

2002-03-08

We surveyed Antarctic krill (Euphausia superba) under sea ice using the autonomous underwater vehicle Autosub-2. Krill were concentrated within a band under ice between 1 and 13 kilometers south of the ice edge. Within this band, krill densities were fivefold greater than that of open water. The under-ice environment has long been considered an important habitat for krill, but sampling difficulties have previously prevented direct observations under ice over the scale necessary for robust krill density estimation. Autosub-2 enabled us to make continuous high-resolution measurements of krill density under ice reaching 27 kilometers beyond the ice edge.

Compact 35μm fiber coupled diode laser module based on dense wavelength division multiplexing of NBA mini-bars

Science.gov (United States)

Witte, U.; Traub, M.; Di Meo, A.; Hamann, M.; Rubel, D.; Hengesbach, S.; Hoffmann, D.

2016-03-01

We present a compact, modular and cross talk free approach for dense wavelength division multiplexing of high power diode lasers based on ultra-steep dielectric filters. The mini bars consist of 5 narrow stripe broad area emitters with a beam parameter product in the range of 2 mm mrad and a wavelength spacing of 2.5 nm between 2 adjacent emitters. Experimental results for fiber coupling (35 μm core diameter, NA < 0.2) of internally and externally stabilized diode lasers are presented. Optical losses are analyzed and alternative optical designs to overcome the current limitations of the setup are discussed.

Wide and Fast Wavelength-Swept Fiber Laser Based on Dispersion Tuning for Dynamic Sensing

Directory of Open Access Journals (Sweden)

Shinji Yamashita

2009-01-01

Full Text Available We have developed a unique wide and fast wavelength-swept fiber laser for dynamic and accurate fiber sensing. The wavelength tuning is based on the dispersion tuning technique, which simply modulates the loss/gain in the dispersive laser cavity. By using wideband semiconductor optical amplifiers (SOAs, the sweep range could be as wide as ∼180 nm. Since the cavity contains no mechanical components, such as tunable filters, we could achieve very high sweep rate, as high as ∼200 kHz. We have realized the swept lasers at three wavelength bands, 1550 nm, 1300 nm, and 800 nm, using SOAs along with erbium-doped fiber amplifiers (EDFAs, and in two laser configurations, ring and linear ones. We also succeeded in applying the swept laser for a dynamic fiber-Bragg grating (FBG sensor system. In this paper, we review our researches on the wide and fast wavelength-swept fiber lasers.

All-Optical Wavelength Conversion by Picosecond Burst Absorption in Colloidal PbS Quantum Dots.

Science.gov (United States)

Geiregat, Pieter; Houtepen, Arjan J; Van Thourhout, Dries; Hens, Zeger

2016-01-26

All-optical approaches to change the wavelength of a data signal are considered more energy- and cost-effective than current wavelength conversion schemes that rely on back and forth switching between the electrical and optical domains. However, the lack of cost-effective materials with sufficiently adequate optoelectronic properties hampers the development of this so-called all-optical wavelength conversion. Here, we show that the interplay between intraband and band gap absorption in colloidal quantum dots leads to a very strong and ultrafast modulation of the light absorption after photoexcitation in which slow components linked to exciton recombination are eliminated. This approach enables all-optical wavelength conversion at rates matching state-of-the-art convertors in speed, yet with cost-effective solution-processable materials. Moreover, the stronger light-matter interaction allows for implementation in small-footprint devices with low switching energies. Being a generic property, the demonstrated effect opens a pathway toward low-power integrated photonics based on colloidal quantum dots as the enabling material.

An Unusual Strong Visible-Light Absorption Band in Red Anatase TiO2 Photocatalyst Induced by Atomic Hydrogen-Occupied Oxygen Vacancies.

Science.gov (United States)

Yang, Yongqiang; Yin, Li-Chang; Gong, Yue; Niu, Ping; Wang, Jian-Qiang; Gu, Lin; Chen, Xingqiu; Liu, Gang; Wang, Lianzhou; Cheng, Hui-Ming

2018-02-01

Increasing visible light absorption of classic wide-bandgap photocatalysts like TiO 2 has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry of these photocatalysts is essential to narrow their bandgap for a strong visible-light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail-like absorption band in hydrogen-free oxygen-deficient TiO 2 , an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO 2 by intentionally introducing atomic hydrogen-mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo-electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide-bandgap semiconductors to fully capture solar light. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multi-wavelength copper vapour lasers for novel materials processing application

International Nuclear Information System (INIS)

Knowles, M.; Foster-Turner, R.; Kearsley, A.; Evans, J.

1995-01-01

The copper vapour laser (CVL) is a high average power, short pulse laser with a multi-kilohertz pulse repetition rate. The CVL laser lines (511 nm and 578 nm) combined with the good beam quality and high peak power available from these lasers allow it to operate in a unique parameter space. Consequently, it has demonstrated many unique and advantageous machining characteristics. We have also demonstrated efficient conversion of CVL radiation to other wavelengths using non-linear frequency conversion, dye lasers and Ti:AL 2 O 3 . Output powers of up to 4 W at 255 nm have been achieved by frequency doubling. The frequency doubled CVL is inherently narrow linewidth and frequency locked making it a suitable source for UV photolithography. Slope efficiencies in excess of 25 % have been achieved with CVL pumped Ti:Al 2 O 3 and dye lasers. These laser extend the wavelengths options into the red and infrared regions of the spectrum. The near diffraction limited beams from these tunable lasers can be efficiently frequency doubled into the blue and near UV. The wide range of wavelength options from the CVL enable a wide variety of materials processing and material interactions to be explored. A European consortium for Copper Laser Applications in Manufacture and Production (CLAMP) has been set up under the EUREKA scheme to coordinate the commercial and technical expertise currently available in Europe. (author)

Monolithically integrated quantum dot optical modulator with semiconductor optical amplifier for thousand and original band optical communication

Science.gov (United States)

Yamamoto, Naokatsu; Akahane, Kouichi; Umezawa, Toshimasa; Matsumoto, Atsushi; Kawanishi, Tetsuya

2016-04-01

A monolithically integrated quantum dot (QD) optical gain modulator (OGM) with a QD semiconductor optical amplifier (SOA) was successfully developed with T-band (1.0 µm waveband) and O-band (1.3 µm waveband) QD optical gain materials for Gbps-order, high-speed optical data generation. The insertion loss due to coupling between the device and the optical fiber was effectively compensated for by the SOA section. It was also confirmed that the monolithic QD-OGM/SOA device enabled >4.8 Gbps optical data generation with a clear eye opening in the T-band. Furthermore, we successfully demonstrated error-free 4.8 Gbps optical data transmissions in each of the six wavelength channels over a 10-km-long photonic crystal fiber using the monolithic QD-OGM/SOA device in multiple O-band wavelength channels, which were generated by the single QD gain chip. These results suggest that the monolithic QD-OGM/SOA device will be advantageous in ultra-broadband optical frequency systems that utilize the T+O-band for short- and medium-range optical communications.

The Optimal Wavelengths for Light Absorption Spectroscopy Measurements Based on Genetic Algorithm-Particle Swarm Optimization

Science.gov (United States)

Tang, Ge; Wei, Biao; Wu, Decao; Feng, Peng; Liu, Juan; Tang, Yuan; Xiong, Shuangfei; Zhang, Zheng

2018-03-01

To select the optimal wavelengths in the light extinction spectroscopy measurement, genetic algorithm-particle swarm optimization (GAPSO) based on genetic algorithm (GA) and particle swarm optimization (PSO) is adopted. The change of the optimal wavelength positions in different feature size parameters and distribution parameters is evaluated. Moreover, the Monte Carlo method based on random probability is used to identify the number of optimal wavelengths, and good inversion effects of the particle size distribution are obtained. The method proved to have the advantage of resisting noise. In order to verify the feasibility of the algorithm, spectra with bands ranging from 200 to 1000 nm are computed. Based on this, the measured data of standard particles are used to verify the algorithm.

Prediction of Helicobacter pylori status by conventional endoscopy, narrow-band imaging magnifying endoscopy in stomach after endoscopic resection of gastric cancer.

Science.gov (United States)

Yagi, Kazuyoshi; Saka, Akiko; Nozawa, Yujiro; Nakamura, Atsuo

2014-04-01

To reduce the incidence of metachronous gastric carcinoma after endoscopic resection of early gastric cancer, Helicobacter pylori eradication therapy has been endorsed. It is not unusual for such patients to be H. pylori negative after eradication or for other reasons. If it were possible to predict H. pylori status using endoscopy alone, it would be very useful in clinical practice. To clarify the accuracy of endoscopic judgment of H. pylori status, we evaluated it in the stomach after endoscopic submucosal dissection (ESD) of gastric cancer. Fifty-six patients treated by ESD were enrolled. The diagnostic criteria for H. pylori status by conventional endoscopy and narrow-band imaging (NBI)-magnifying endoscopy were decided, and H. pylori status was judged by two endoscopists. Based on the H. pylori stool antigen test as a diagnostic gold standard, conventional endoscopy and NBI-magnifying endoscopy were compared for their sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Interobserver agreement was assessed in terms of κ value. Interobserver agreement was moderate (0.56) for conventional endoscopy and substantial (0.77) for NBI-magnifying endoscopy. The sensitivity, specificity, PPV, and NPV were 0.79, 0.52, 0.70, and 0.63 for conventional endoscopy and 0.91, 0.83, 0.88, and 0.86 for NBI-magnifying endoscopy, respectively. Prediction of H. pylori status using NBI-magnifying endoscopy is practical, and interobserver agreement is substantial. © 2013 John Wiley & Sons Ltd.

Clicking in a killer whale habitat: narrow-band, high-frequency biosonar clicks of harbour porpoise (Phocoena phocoena and Dall's porpoise (Phocoenoides dalli.

Directory of Open Access Journals (Sweden)

Line A Kyhn

Full Text Available Odontocetes produce a range of different echolocation clicks but four groups in different families have converged on producing the same stereotyped narrow band high frequency (NBHF click. In microchiropteran bats, sympatric species have evolved the use of different acoustic niches and subtly different echolocation signals to avoid competition among species. In this study, we examined whether similar adaptations are at play among sympatric porpoise species that use NBHF echolocation clicks. We used a six-element hydrophone array to record harbour and Dall's porpoises in British Columbia (BC, Canada, and harbour porpoises in Denmark. The click source properties of all porpoise groups were remarkably similar and had an average directivity index of 25 dB. Yet there was a small, but consistent and significant 4 kHz difference in centroid frequency between sympatric Dall's (137±3 kHz and Canadian harbour porpoises (141±2 kHz. Danish harbour porpoise clicks (136±3 kHz were more similar to Dall's porpoise than to their conspecifics in Canada. We suggest that the spectral differences in echolocation clicks between the sympatric porpoises are consistent with evolution of a prezygotic isolating barrier (i.e., character displacement to avoid hybridization of sympatric species. In practical terms, these spectral differences have immediate application to passive acoustic monitoring.

Optical constants and band edge of amorphous zinc oxide thin films

International Nuclear Information System (INIS)

Khoshman, Jebreel M.; Kordesch, Martin E.

2007-01-01

The optical characteristics of amorphous zinc oxide (a-ZnO) thin films grown by radio frequency reactive magnetron sputtering on various substrates at temperature -8 -0.32, respectively. The band edge of the films on Si (100) and quartz has been determined by spectroscopic ellipsometry (3.39 ± 0.05 eV) and spectrophotometric (3.35 ± 0.05 eV) methods, respectively. From the angle dependence of the p-polarized reflectivity we deduce a Brewster angle of 60.5 deg. Measurement of the polarized optical properties shows a high transmissivity (81%-99%) and low absorptivity (< 5%) in the visible and near infrared regions at different angles of incidence. Also, we found that there was a higher absorptivity for wavelength < 370 nm. This wavelength, ∼ 370 nm, therefore indicated that the band edge for a-ZnO thin films is about 3.35 eV

Illumination wavelength and time dependent nano gold photo-deposition and CO oxidation

Directory of Open Access Journals (Sweden)

Siewhui Chong

Full Text Available In this study, nano gold (Au was deposited on titanium dioxide (TiO2 of different morphologies and crystallinities by photo-deposition method under LED irradiation with various wavelengths and irradiation times. The reactivity of carbon monoxide (CO oxidation of the as-prepared catalysts was examined and correlated with the characteristics of TiO2 support and gold particles. Characterization and activity tests showed that the effective illumination wavelength of photo-deposition is strongly determined by the band-gap of TiO2. Au/Cubic-TiO2 (450 nm, 5 min yielded comparatively highest CO conversion of 71%, followed by Au/P25 (375 nm, 1 min and Au/ST21 (340 nm, 1 min. When the photon energy of the LED is lower than the band-gap of TiO2, CO conversion rate increases with the irradiation time due to the decrease in gold particle size which could possibly due to the lower speed of photo-deposition compared to that of concentration diffusion. Keywords: Gold, Catalyst, TiO2, Photodeposition, Carbon monoxide, Oxidation

Enhancement of broadband optical absorption in photovoltaic devices by band-edge effect of photonic crystals.

Science.gov (United States)

Tanaka, Yoshinori; Kawamoto, Yosuke; Fujita, Masayuki; Noda, Susumu

2013-08-26

We numerically investigate broadband optical absorption enhancement in thin, 400-nm thick microcrystalline silicon (µc-Si) photovoltaic devices by photonic crystals (PCs). We realize absorption enhancement by coupling the light from the free space to the large area resonant modes at the photonic band-edge induced by the photonic crystals. We show that multiple photonic band-edge modes can be produced by higher order modes in the vertical direction of the Si photovoltaic layer, which can enhance the absorption on multiple wavelengths. Moreover, we reveal that the photonic superlattice structure can produce more photonic band-edge modes that lead to further optical absorption. The absorption average in wavelengths of 500-1000 nm weighted to the solar spectrum (AM 1.5) increases almost twice: from 33% without photonic crystal to 58% with a 4 × 4 period superlattice photonic crystal; our result outperforms the Lambertian textured structure.

Design of a Short/Open-Ended Slot Antenna with Capacitive Coupling Feed Strips for Hepta-Band Mobile Application

Directory of Open Access Journals (Sweden)

Kyoseung Keum

2018-01-01

Full Text Available In this paper, a planar printed hybrid short/open-ended slot antenna with capacitive coupling feed strips is proposed for hepta-band mobile applications. The proposed antenna is comprised of a slotted ground plane on the top plane and two capacitive coupling feed strips with a chip inductor on the bottom plane. At the low frequency band, the short-ended long slot fed by strip 1 generates its half-wavelength resonance mode, whereas the T-shaped open ended slot fed by strip 2 generates its quarter-wavelength resonance mode for the high frequency band. The antenna provides a wide bandwidth covering GSM850/GSM900/DCS/PCS/UMTS/LTE2300/LTE2500 operation bands. Moreover, the antenna occupies a small volume of 15 mm × 50 mm × 1 mm. The operating principle of the proposed antenna and the simulation/measurement results are presented and discussed.

Tailoring Chirped Moiré Fiber Bragg Gratings for Wavelength-Division-Multiplexing and Optical Code-Division Multiple-Access Applications

Science.gov (United States)

Chen, Lawrence R.; Smith, Peter W. E.

The design and fabrication of chirped Moiré fiber Bragg gratings (CMGs) are presented, which can be used in either (1) transmission as passband filters for providing wavelength selectivity in wavelength-division-multiplexed (WDM) systems or (2) reflection as encoding/decoding elements to decompose short broadband pulses in both wavelength and time in order to implement an optical code-division multiple-access (OCDMA) system. In transmission, the fabricated CMGs have single or multiple flattened passbands ( 12 dB isolation and near constant in-band group delay. It is shown that these filters do not produce any measurable dispersion-induced power penalties when used to provide wavelength selectivity in 2.5 Gbit/s systems. It is also demonstrated how CMGs can be used in reflection to encode/decode short pulses from a wavelength-tunable mode-locked Er-doped fiber laser.

Enabling Searches on Wavelengths in a Hyperspectral Indices Database

Science.gov (United States)

Piñuela, F.; Cerra, D.; Müller, R.

2017-10-01

Spectral indices derived from hyperspectral reflectance measurements are powerful tools to estimate physical parameters in a non-destructive and precise way for several fields of applications, among others vegetation health analysis, coastal and deep water constituents, geology, and atmosphere composition. In the last years, several micro-hyperspectral sensors have appeared, with both full-frame and push-broom acquisition technologies, while in the near future several hyperspectral spaceborne missions are planned to be launched. This is fostering the use of hyperspectral data in basic and applied research causing a large number of spectral indices to be defined and used in various applications. Ad hoc search engines are therefore needed to retrieve the most appropriate indices for a given application. In traditional systems, query input parameters are limited to alphanumeric strings, while characteristics such as spectral range/ bandwidth are not used in any existing search engine. Such information would be relevant, as it enables an inverse type of search: given the spectral capabilities of a given sensor or a specific spectral band, find all indices which can be derived from it. This paper describes a tool which enables a search as described above, by using the central wavelength or spectral range used by a given index as a search parameter. This offers the ability to manage numeric wavelength ranges in order to select indices which work at best in a given set of wavelengths or wavelength ranges.

Selective UV radiation detection on the basis of low-dimensional ZnCdS/ZnMgS/GaP and ZnCdS/ZnS/GaP heterostructures

Energy Technology Data Exchange (ETDEWEB)

Averin, S. V., E-mail: sva278@ire216.msk.su; Kuznetzov, P. I.; Zhitov, V. A.; Zakharov, L. Yu.; Kotov, V. M.; Alkeev, N. V. [Russian Academy of Sciences, Fryazino Branch, Kotel’nikov Institute of Radio Engineering and Electronics (Russian Federation); Gladisheva, N. B. [Pulsar State Plant (Russian Federation)

2015-11-15

The detecting properties of periodic heterostructures with ZnCdS quantum wells separated by ZnMgS or ZnS barrier layers are studied. Heterostructures are grown on semi-insulating GaP substrates by metal organic vapor-phase epitaxy (MOVPE). On their basis, metal–semiconductor–metal (MSM) diodes with interdigital Schottky contacts 3 μm, distances between them of 3 μm, and a total detector area of 100 × 100 μm are fabricated. The detectors have low dark currents (10{sup –12} A); at low bias voltages, they provide a narrow- band response (full-width at half-maximum of FWHM = 18 nm at a wavelength of 350 nm) which is controlled by the ZnCdS quantum-well composition. As bias is increased to 70 V, the maximum detector sensitivity shifts by a wavelength of 450 nm, which is caused by penetration of the external-bias electric field into the semi-insulating GaP substrate. In this case, the narrow-band response of the detector at a wavelength of 350 nm is retained, i.e., the two-color detection of light is provided.

Studies on omnidirectional enhancement of giga-hertz radiation by sub-wavelength plasma modulation

Science.gov (United States)

Fanrong, KONG; Qiuyue, NIE; Shu, LIN; Zhibin, WANG; Bowen, LI; Shulei, ZHENG; Binhao, JIANG

2018-01-01

The technology of radio frequency (RF) radiation intensification for radio compact antennas based on modulation and enhancement effects of sub-wavelength plasma structures represents an innovative developing strategy. It exhibits important scientific significance and promising potential of broad applications in various areas of national strategic demands, such as electrical information network and microwave communication, detection and control technology. In this paper, laboratory experiments and corresponding analyses have been carried out to investigate the modulation and enhancement technology of sub-wavelength plasma structure on the RF electromagnetic radiation. An application focused sub-wavelength plasma-added intensification up to ∼7 dB higher than the free-space radiation is observed experimentally in giga-hertz (GHz) RF band. The effective radiation enhancement bandwidth covers from 0.85 to 1.17 GHz, while the enhanced electromagnetic signals transmitted by sub-wavelength plasma structures maintain good communication quality. Particularly, differing from the traditional RF electromagnetic radiation enhancement method characterized by focusing the radiation field of antenna in a specific direction, the sub-wavelength plasma-added intensification of the antenna radiation presents an omnidirectional enhancement, which is reported experimentally for the first time. Corresponding performance characteristics and enhancement mechanism analyses are also conducted in this paper. The results have demonstrated the feasibility and promising potential of sub-wavelength plasma modulation in application focused RF communication, and provided the scientific basis for further research and development of sub-wavelength plasma enhanced compact antennas with wide-range requests and good quality for communication.

High-Pressure Band-Gap Engineering in Lead-Free Cs ₂ AgBiBr ₆ Double Perovskite

Energy Technology Data Exchange (ETDEWEB)

Li, Qian [Department of Chemistry, Southern University of Science and Technology, SUSTech, Shenzhen Guangdong 518055 P.R. China; College of Chemistry, Nankai University, Tianjin 300071 P.R. China; Wang, Yonggang [High Pressure Synergetic Consortium, HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL 60439 USA; Pan, Weicheng [Wuhan National Laboratory for Optoelectronics, WNLO and School of Optical and Electronic Information, Huazhong University of Science and Technology, HUST, Wuhan 430074 P.R. China; Yang, Wenge [High Pressure Synergetic Consortium, HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL 60439 USA; Zou, Bo [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 P.R. China; Tang, Jiang [Wuhan National Laboratory for Optoelectronics, WNLO and School of Optical and Electronic Information, Huazhong University of Science and Technology, HUST, Wuhan 430074 P.R. China; Quan, Zewei [Department of Chemistry, Southern University of Science and Technology, SUSTech, Shenzhen Guangdong 518055 P.R. China

2017-11-15

Novel inorganic lead-free double perovskites with improved stability are regarded as alternatives to state-of-art hybrid lead halide perovskites in photovoltaic devices. The recently discovered Cs2AgBiBr6 double perovskite exhibits attractive optical and electronic features, making it promising for various optoelectronic applications. However, its practical performance is hampered by the large band gap. In this work, remarkable band gap narrowing of Cs2AgBiBr6 is, for the first time, achieved on inorganic photovoltaic double perovskites through high pressure treatments. Moreover, the narrowed band gap is partially retainable after releasing pressure, promoting its optoelectronic applications. This work not only provides novel insights into the structure–property relationship in lead-free double perovskites, but also offers new strategies for further development of advanced perovskite devices.

Method for calibration-free scanned-wavelength modulation spectroscopy for gas sensing

Science.gov (United States)

Hanson, Ronald K.; Jeffries, Jay B.; Sun, Kai; Sur, Ritobrata; Chao, Xing

2018-04-10

A method of calibration-free scanned-wavelength modulation spectroscopy (WMS) absorption sensing is provided by obtaining absorption lineshape measurements of a gas sample on a sensor using 1f-normalized WMS-2f where an injection current to an injection current-tunable diode laser (TDL) is modulated at a frequency f, where a wavelength modulation and an intensity modulation of the TDL are simultaneously generated, extracting using a numerical lock-in program and a low-pass filter appropriate band-width WMS-nf (n=1, 2, . . . ) signals, where the WMS-nf signals are harmonics of the f, determining a physical property of the gas sample according to ratios of the WMS-nf signals, determining the zero-absorption background using scanned-wavelength WMS, and determining non-absorption losses using at least two of the harmonics, where a need for a non-absorption baseline measurement is removed from measurements in environments where collision broadening has blended transition linewidths, where calibration free WMS measurements without knowledge of the transition linewidth is enabled.

Diode laser spectroscopy of oxygen electronic band at 760 nm

International Nuclear Information System (INIS)

Lucchesini, A.; De Rosa, M.; Gozzini, S.

1998-01-01

Collisional broadening and shift coefficients have been obtained by analyzing the line shapes of oxygen absorptions in the 760 nm electronic band. By using a diode laser spectrometer with commercially available etherostructure Al x Ga 1-x As diode lasers operating in 'free-running mode', line shape parameters have been collected at room temperature by varying the gas pressure. A systematic study has been carried on seven absorption lines by scanning the diode laser emission wavelength around the gas resonances. The weak absorption lines have been detected by using the wavelength modulation (WM) spectroscopy technique with second-harmonic detection

Plasmonic Band-Pass Microfilters for LWIR Absorption Spectroscopy

Directory of Open Access Journals (Sweden)

J. M. Banks

2012-01-01

Full Text Available Absorption spectroscopy in the long wave infrared provides an effective method for identification of various hazardous chemicals. We present a theoretical design for plasmonic band-pass filters that can be used to provide wavelength selectivity for uncooled microbolometer sensors. The microfilters consist of a pair of input reflection gratings that couple light into a plasmonic waveguide with a central resonant waveguide cavity. An output transmission grating on the other side of the structure pulls light out of the waveguide where it is detected by a closely spaced sensor. Fabrication of the filters can be performed using standard photolithography procedures. A spectral bandpass with a full-width at half-maximum (FWHM of 100 nm can be obtained with a center wavelength spanning the entire 8–12 μm atmospheric transmission window by simple geometric scaling of only the lateral dimensions. This allows the simultaneous fabrication of all the wavelength filters needed for a full spectrometer on a chip.

Swift Multi-wavelength Observing Campaigns: Strategies and Outcomes

Science.gov (United States)

Krimm, Hans A.

2007-01-01

The Swift gamma-ray burst explorer has been operating since December 2004 as both a gamma-ray burst (GRB) monitor and telescope and a multi-wavelength observatory, covering the energy range from V band and near UV to hard X rays above 150 keV. It is designed to rapidly repoint to observe newly discovered GRBs, and this maneuverability, combined with an easily changed observing program, allows Swift to also be an effective multiwavelength observatory for non-GRB targets, both as targets of opportunity and pre-planned multi-wavelength observing campaigns. Blazars are particularly attractive targets for coordinated campaigns with TeV experiments since many blazars are bright in both the hard X-ray and TeV energy ranges. Successful coordinated campaigns have included observations of 3C454.3 during its 2005 outburst. The latest Swift funding cycles allow for non- GRB related observations to be proposed. The Burst Alert Telescope on Swift also serves as a hard X-ray monitor with a public web page that includes light curves for over 400 X-ray sources and is used to alert the astronomical community about increased activity from both known and newly discovered sources. This presentation mill include Swift capabilities, strategies and policies for coordinated multi-wavelength observations as well as discussion of the potential outcomes of such campaigns.

Band gap tuning of amorphous Al oxides by Zr alloying

DEFF Research Database (Denmark)

Canulescu, Stela; Jones, N. C.; Borca, C. N.

2016-01-01

minimum changes non-linearly as well.Fitting of the energy band gap values resulted in a bowing parameter of 2 eV. The band gap bowing of themixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction bandminimum of anodized Al2O3.......The optical band gap and electronic structure of amorphous Al-Zr mixed oxides, with Zr content ranging from4.8 to 21.9% were determined using vacuum ultraviolet (VUV) and X-ray absorption spectroscopy (XAS). Thelight scattering by the nano-porous structure of alumina at low wavelengths...... was estimated based on the Miescattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on Zr content deviatesfrom linearity and decreases from 7.3 eV for pure anodized Al2O3 to 6.45 eV for Al-Zr mixed oxide with Zrcontent of 21.9%. With increasing Zr content, the conduction band...

Intracavity Cr3+:LiCAF + PPSLT optical parametric oscillator with self-injection-locked pump wave

International Nuclear Information System (INIS)

Maestre, H; Torregrosa, A J; Capmany, J

2013-01-01

In this letter we present an intracavity pumped continuous wave (CW) doubly resonant optical parametric oscillator (OPO) based on Cr 3+ :LiCaAlF 6 (Cr:LiCAF) as the material generating the OPO pump wave and periodically poled stoichiometric lithium tantalate (PPSLT) as the nonlinear material. The OPO pump wave is spectrally narrowed and tuned by means of an external cavity, thus allowing self-injection locking of the OPO pump wavelength. When operated near degeneracy, the constructed OPO enables a fast tuning of the parametrically generated wavelengths in response to small perturbations of the phase-matching condition. The Cr:LiCAF emission band is especially well suited to provide dual-wavelength oscillation in the optical communications 1550 nm band as a result of the parametric oscillation in PPSLT. (letter)

A high-speed, eight-wavelength visible light-infrared pyrometer for shock physics experiments

Science.gov (United States)

Wang, Rongbo; Li, Shengfu; Zhou, Weijun; Luo, Zhen-Xiong; Meng, Jianhua; Tian, Jianhua; He, Lihua; Cheng, Xianchao

2017-09-01

An eight-channel, high speed pyrometer for precise temperature measurement is designed and realized in this work. The addition of longer-wavelength channels sensitive at lower temperatures highly expands the measured temperature range, which covers the temperature of interest in shock physics from 1500K-10000K. The working wavelength range is 400-1700nm from visible light to near-infrared (NIR). Semiconductor detectors of Si and InGaAs are used as photoelectric devices, whose bandwidths are 50MHz and 150MHz respectively. Benefitting from the high responsivity and high speed of detectors, the time resolution of the pyrometer can be smaller than 10ns. By combining the high-transmittance beam-splitters and narrow-bandwidth filters, the peak spectrum transmissivity of each channel can be higher than 60%. The gray-body temperatures of NaI crystal under shock-loading are successfully measured by this pyrometer.

Optimization problems of QW-SCH heterostructures AlGaAs/GaAs designed for working at 808 nm band

International Nuclear Information System (INIS)

Malag, A.; Kozlowska, A.; Strupinski, W.; Mozdzonek, M.; Dobrzanski, L.; Teodorczyk, M.; Mroziewicz, B.

1999-01-01

Semiconductor laser diodes (LDs) emitting in the 808 nm range found main field of application in the pumping systems of Nd 3+ :YAG lasers. Because of narrow absorption line of YAG material, narrow emission line of the laser pump exactly at the 808 nm wavelength is expected at the temperature optimised from the viewpoint of its stabilization (usually it is about 15 o C). To meet these requirements, an optimisation of the laser (AlGa)As heterostructure because of the composition and thickness of the constituent layers is necessary. In the communicate the design foundations, the characteristics of the manufactured LDs based on this design and intrinsic limitations of the possibility of 'tuning' the lasers to desired wavelength in the technological process are presented. The reported LDs are of the wide-stripe type with the Schottky-junction-isolation and have been manufactured from the MOVPE grown (Alga)As heterostructure. (author)

High-pressure band-gap engineering in lead-free Cs{sub 2}AgBiBr{sub 6} double perovskite

Energy Technology Data Exchange (ETDEWEB)

Li, Qian [Department of Chemistry, Southern University of Science and Technology, SUSTech, Shenzhen, Guangdong (China); College of Chemistry, Nankai University, Tianjin (China); Wang, Yonggang; Yang, Wenge [High Pressure Synergetic Consortium, HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL (United States); Pan, Weicheng; Tang, Jiang [Wuhan National Laboratory for Optoelectronics, WNLO and School of Optical and Electronic Information, Huazhong University of Science and Technology, HUST, Wuhan (China); Zou, Bo [State Key Laboratory of Superhard Materials, Jilin University, Changchun (China); Quan, Zewei [Department of Chemistry, Southern University of Science and Technology, SUSTech, Shenzhen, Guangdong (China)

2017-12-11

Novel inorganic lead-free double perovskites with improved stability are regarded as alternatives to state-of-art hybrid lead halide perovskites in photovoltaic devices. The recently discovered Cs{sub 2}AgBiBr{sub 6} double perovskite exhibits attractive optical and electronic features, making it promising for various optoelectronic applications. However, its practical performance is hampered by the large band gap. In this work, remarkable band gap narrowing of Cs{sub 2}AgBiBr{sub 6} is, for the first time, achieved on inorganic photovoltaic double perovskites through high pressure treatments. Moreover, the narrowed band gap is partially retainable after releasing pressure, promoting its optoelectronic applications. This work not only provides novel insights into the structure-property relationship in lead-free double perovskites, but also offers new strategies for further development of advanced perovskite devices. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

A Raman spectroscopic study of organic matter in interplanetary dust particles and meteorites using multiple wavelength laser excitation

OpenAIRE

Starkey, N. A.; Franchi, I. A.; Alexander, C. M. O'D.

2013-01-01

Raman spectroscopy was used to investigate insoluble organic matter (IOM) from a range of chondritic meteorites, and a suite of interplanetary dust particles (IDPs). Three monochromatic excitation wavelengths (473 nm, 514 nm, 632 nm) were applied sequentially to assess variations in meteorite and IDP Raman peak parameters (carbon D and G bands) as a function of excitation wavelength (i.e., dispersion). Greatest dispersion occurs in CVs > OCs > CMs > CRs with type 3 chondrites compared at diff...

Narrow-line, cw orange light generation in a diode-pumped Nd:YVO4 laser using volume Bragg gratings.

Science.gov (United States)

Chen, Y L; Chen, W W; Du, C E; Chang, W K; Wang, J L; Chung, T Y; Chen, Y H

2009-12-07

We report on the demonstration of a narrow-line, cw orange 593-nm laser achieved via intracavity sum-frequency generation (SFG) of a diode-pumped dual-wavelength (1064 and 1342 nm) Nd:YVO(4) laser using two volume Bragg grating (VBG) reflectors. At diode pump power of up to 3.6 W, the 593-nm intracavity SFG laser radiates at the single longitudinal mode of spectral linewidth as narrow as approximately 15 MHz. More than 23-mW single-longitudinal-mode or 40-mW, diode pump power) 593-nm orange lights can be obtained from this compact laser system. Spectral tuning of the orange light was performed via the temperature tuning of the two VBGs in this system, achieving an effective tuning rate of ~5 pm/degrees C.

Fabrication of sub-wavelength photonic structures by nanoimprint lithography

Energy Technology Data Exchange (ETDEWEB)

Kontio, J.

2013-11-01

Nanoimprint lithography (NIL) is a novel but already a mature lithography technique. In this thesis it is applied to the fabrication of nanophotonic devices using its main advantage: the fast production of sub-micron features in high volume in a cost-effective way. In this thesis, fabrication methods for conical metal structures for plasmonic applications and sub-wavelength grating based broad-band mirrors are presented. Conical metal structures, nanocones, with plasmonic properties are interesting because they enable concentrating the energy of light in very tight spots resulting in very high local intensities of electromagnetic energy. The nanocone formation process is studied with several metals. Enhanced second harmonic generation using gold nanocones is presented. Bridged-nanocones are used to enhance Raman scattering from a dye solution. The sub-wavelength grating mirror is an interesting structure for photonics because it is very simple to fabricate and its reflectivity can be extended to the far infrared wavelength range. It also has polarization dependent properties which are used in this thesis to stabilize the output beam of infrared semiconductor disk laser. NIL is shown to be useful a technique in the fabrication of nanophotonic devices in the novel and rapidly growing field of plasmonics and also in more traditional, but still developing, semiconductor laser applications (orig.)

Inefficiency of intervalley transfer in narrow InGaAs/AlAsSb quantum wells

International Nuclear Information System (INIS)

Tribuzy, C.V.B.; Ohser, S.; Priegnitz, M.; Winnerl, S.; Schneider, H.; Helm, M.; Neuhaus, J.; Dekorsy, T.; Biermann, K.; Kuenzel, H.

2008-01-01

By using femtosecond pump-probe spectroscopy we investigate the intersubband relaxation dynamics in narrow InGaAs/AlAsSb quantum wells. A biexponential behavior is an indication of intervalley scattering, which is, however, much slower than known from bulk material. This may be the reason why quantum cascade lasers at wavelengths as short as 3 μm are actually functioning In addition, when pumping slightly below resonance we observe an induced transient absorption, which can be interpreted in terms of electron heating within the first subband. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Band-engineering of TiO2 as a wide-band gap semiconductor using organic chromophore dyes

Science.gov (United States)

Wahyuningsih, S.; Kartini, I.; Ramelan, A. H.; Saputri, L. N. M. Z.; Munawaroh, H.

2017-07-01

Bond-engineering as applied to semiconductor materials refers to the manipulation of the energy bands in order to control charge transfer processes in a device. When the device in question is a photoelectrochemical cell, the charges affected by drift become the focus of the study. The ideal band gap of semiconductors for enhancement of photocatalyst activity can be lowered to match with visible light absorption and the location of conduction Band (CB) should be raised to meet the reducing capacity. Otherwise, by the addition of the chromofor organic dyes, the wide-band gab can be influences by interacation resulting between TiO2 surface and the dyes. We have done the impruvisation wide-band gap of TiO2 by the addition of organic chromophore dye, and the addition of transition metal dopand. The TiO2 morphology influence the light absorption as well as the surface modification. The organic chromophore dye was syntesized by formation complexes compound of Co(PAR)(SiPA)(PAR)= 4-(2-piridylazoresorcinol), SiPA = Silyl propil amine). The result showed that the chromophore groups adsorbed onto TiO2 surface can increase the visible light absorption of wide-band gab semiconductor. Initial absorption of a chromophore will affect light penetration into the material surfaces. The use of photonic material as a solar cell shows this phenomenon clearly from the IPCE (incident photon to current conversion efficiency) measurement data. Organic chromophore dyes of Co(PAR)(SiPA) exhibited the long wavelength absorption character compared to the N719 dye (from Dyesol).

Hyperspectral band selection based on consistency-measure of neighborhood rough set theory

International Nuclear Information System (INIS)

Liu, Yao; Xie, Hong; Wang, Liguo; Tan, Kezhu; Chen, Yuehua; Xu, Zhen

2016-01-01

Band selection is a well-known approach for reducing dimensionality in hyperspectral imaging. In this paper, a band selection method based on consistency-measure of neighborhood rough set theory (CMNRS) was proposed to select informative bands from hyperspectral images. A decision-making information system was established by the reflection spectrum of soybeans’ hyperspectral data between 400 nm and 1000 nm wavelengths. The neighborhood consistency-measure, which reflects not only the size of the decision positive region, but also the sample distribution in the boundary region, was used as the evaluation function of band significance. The optimal band subset was selected by a forward greedy search algorithm. A post-pruning strategy was employed to overcome the over-fitting problem and find the minimum subset. To assess the effectiveness of the proposed band selection technique, two classification models (extreme learning machine (ELM) and random forests (RF)) were built. The experimental results showed that the proposed algorithm can effectively select key bands and obtain satisfactory classification accuracy. (paper)

Band gap engineering of BC2N for nanoelectronic applications

Science.gov (United States)

Lim, Wei Hong; Hamzah, Afiq; Ahmadi, Mohammad Taghi; Ismail, Razali

2017-12-01

The BC2N as an example of boron-carbon-nitride (BCN), has the analogous structure as the graphene and boron nitride. It is predicted to have controllable electronic properties. Therefore, the analytical study on the engineer-able band gap of the BC2N is carried out based on the schematic structure of BC2N. The Nearest Neighbour Tight Binding (NNTB) model is employed with the dispersion relation and the density of state (DOS) as the main band gap analysing parameter. The results show that the hopping integrals having the significant effect on the band gap, band structure and DOS of BC2N nanowire (BC2NNW) need to be taken into consideration. The presented model indicates consistent trends with the published computational results around the Dirac points with the extracted band gap of 0.12 eV. Also, it is distinguished that wide energy gap of boron nitride (BN) is successfully narrowed by this carbon doped material which assures the application of BC2N on the nanoelectronics and optoelectronics in the near future.

Strong coupling between a permalloy ferromagnetic contact and helical edge channel in a narrow HgTe quantum well

Energy Technology Data Exchange (ETDEWEB)

Kononov, A.; Egorov, S. V. [Russian Academy Sciences, Institute of Solid State Physics (Russian Federation); Kvon, Z. D.; Mikhailov, N. N.; Dvoretsky, S. A. [Institute of Semiconductor Physics (Russian Federation); Deviatov, E. V., E-mail: dev@issp.ac.ru [Russian Academy Sciences, Institute of Solid State Physics (Russian Federation)

2016-11-15

We experimentally investigate spin-polarized electron transport between a permalloy ferromagnet and the edge of a two-dimensional electron system with band inversion, realized in a narrow, 8 nm wide, HgTe quantum well. In zero magnetic field, we observe strong asymmetry of the edge potential distribution with respect to the ferromagnetic ground lead. This result indicates that the helical edge channel, specific for the structures with band inversion even at the conductive bulk, is strongly coupled to the ferromagnetic side contact, possibly due to the effects of proximity magnetization. This allows selective and spin-sensitive contacting of helical edge states.

Band gap tuning of amorphous Al oxides by Zr alloying

Energy Technology Data Exchange (ETDEWEB)

Canulescu, S., E-mail: stec@fotonik.dtu.dk; Schou, J. [Department of Photonics Engineering, Technical University of Denmark, 4000 Roskilde (Denmark); Jones, N. C.; Hoffmann, S. V. [ISA, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus (Denmark); Borca, C. N.; Piamonteze, C. [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Rechendorff, K.; Nielsen, L. P.; Almtoft, K. P. [Danish Technological Institute, Kongsvang Alle 29, 8000 Aarhus (Denmark); Gudla, V. C.; Bordo, K.; Ambat, R. [Department of Mechanical Engineering, Technical University of Denmark, 2800 Kgs-Lyngby (Denmark)

2016-08-29

The optical band gap and electronic structure of amorphous Al-Zr mixed oxides with Zr content ranging from 4.8 to 21.9% were determined using vacuum ultraviolet and X-ray absorption spectroscopy. The light scattering by the nano-porous structure of alumina at low wavelengths was estimated based on the Mie scattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on the Zr content deviates from linearity and decreases from 7.3 eV for pure anodized Al{sub 2}O{sub 3} to 6.45 eV for Al-Zr mixed oxides with a Zr content of 21.9%. With increasing Zr content, the conduction band minimum changes non-linearly as well. Fitting of the energy band gap values resulted in a bowing parameter of ∼2 eV. The band gap bowing of the mixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction band minimum of anodized Al{sub 2}O{sub 3}.

Solar-blind ultraviolet band-pass filter based on metal—dielectric multilayer structures

International Nuclear Information System (INIS)

Wang Tian-Jiao; Xu Wei-Zong; Lu Hai; Ren Fang-Fang; Chen Dun-Jun; Zhang Rong; Zheng You-Dou

2014-01-01

Solar-blind ultraviolet (UV) band-pass filter has significant value in many scientific, commercial, and military applications, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of “transparent metal”. The filter consisting of Al/SiO 2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

High Power OPO Laser and wavelength-controlled system for 1.6μm CO2-DIAL

Science.gov (United States)

Abo, M.; Nagasawa, C.; Shibata, Y.

2009-12-01

Unlike the existing 2.0μm CO2-DIAL, a high-energy pulse laser operating in the 1.6μm absorption band of CO2 has not been realized. Quasi phase matching (QPM) devices have high conversion efficiency and high beam quality due to their higher nonlinear optical coefficient. We adapt the PPMgLT crystal as the QPM device. The PPMgLT crystal had 3mm × 3mm apertures, and the periodically poled period was 30.9 μm, with the duty ratio close to the ideal value of 0.5. The beam quality of the pumping laser was exceed M2 ≥1.2. The repetition rate was 400 Hz and the energy was 35 mJ. The pumping laser pulse was injection-seeded by the continuous-wave (CW) fiber laser, which had a narrow spectrum. The pulse pumped the PPMgLT crystal in the ring cavity with a single pass through the dielectric mirror. The PPMgLT crystal was mounted on a copper holder, and the temperature was maintained at 40 °C using a Peltier module. The holder’s temperature was stabilized to within 0.01 °C when the copper holder was covered with a plastic case. The OPO ring cavity was a singly resonant oscillator optimized for the signal wave. Single-frequency oscillation of the PPMgLT OPO was achieved by injection seeding, as described in the following. The injection seeder was a DFB laser having a power of 30mW with a 1MHz oscillation spectrum. Their oscillation wavelength was coarse tuned by temperature and fine tuned by adjusting injection currents. The partial power of the online wavelength was split in the wavelength control unit. We locked the DFB laser as an injection seeder of the online wavelength onto the line center by referencing the fiber coupled multipath gas cell (path length 800mm) containing pure CO2 at a pressure of 700 Torr. Stabilization was estimated to within 1.8MHz rms of the line center of the CO2 absorption line by monitoring the feedback signal of a wavelength-controlled unit. Injection seeding of the PPMgLT OPO was performed by matching the cavity length to the seeder

RAPID INFRARED VARIABILITY OF THREE RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES: A VIEW FROM THE WIDE-FIELD INFRARED SURVEY EXPLORER

Energy Technology Data Exchange (ETDEWEB)

Jiang Ning; Zhou Hongyan; Wang Tinggui; Dong Xiaobo; Jiang Peng [Key Laboratory for Research in Galaxies and Cosmology, University of Science and Technology of China, Chinese Academy of Science, Hefei, Anhui 230026 (China); Ho, Luis C. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Yuan Weimin [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Ji Tuo; Tian Qiguo, E-mail: jnac@mail.ustc.edu.cn [Polar Research Institute of China, 451 Jinqiao Road, Pudong, Shanghai 200136 (China)

2012-11-10

Using newly released data from the Wide-field Infrared Survey Explorer, we report the discovery of rapid infrared variability in three radio-loud narrow-line Seyfert 1 galaxies (NLS1s) selected from the 23 sources in the sample of Yuan et al. J0849+5108 and J0948+0022 clearly show intraday variability, while J1505+0326 has a longer measurable timescale within 180 days. Their variability amplitudes, corrected for measurement errors, are {approx}0.1-0.2 mag. The detection of intraday variability restricts the size of the infrared-emitting region to {approx}10{sup -3} pc, significantly smaller than the scale of the torus but consistent with the base of a jet. The three variable sources are exceptionally radio-loud, have the highest radio brightness temperature among the whole sample, and all show detected {gamma}-ray emission in Fermi/LAT observations. Their spectral energy distributions resemble those of low-energy-peaked blazars, with a synchrotron peak around infrared wavelengths. This result strongly confirms the view that at least some radio-loud NLS1s are blazars with a relativistic jet close to our line of sight. The beamed synchrotron emission from the jet contributes significantly to and probably dominates the spectra in the infrared and even optical bands.

Spectroscopic evidence for 5f bands at room temperature in uranium-based heavy fermions

International Nuclear Information System (INIS)

Arko, A.J.; Koelling, D.D.; Dunlap, B.D.; Capasso, C.; del Giudice, M.

1988-01-01

We present data on the alloy system UPd/sub 3-x/Pt/sub x/ and show that in the double hexagonal phase (x 2.4) as well, except that the low-binding energy feature is locked in at E/sub F/ and shows evidence of energy dispersion at room temperature/endash/consistent with well-defined bands. Conversely, we show that even in well-behaved narrow band systems (USn 3 there is evidence for satellite formation. 44 refs., 8 figs

Travelling-wave resonant four-wave mixing breaks the limits of cavity-enhanced all-optical wavelength conversion.

Science.gov (United States)

Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea

2011-01-01

Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-μm-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s(-1).

Raman imaging using fixed bandpass filter

Science.gov (United States)

Landström, L.; Kullander, F.; Lundén, H.; Wästerby, P.

2017-05-01

By using fixed narrow band pass optical filtering and scanning the laser excitation wavelength, hyperspectral Raman imaging could be achieved. Experimental, proof-of-principle results from the Chemical Warfare Agent (CWA) tabun (GA) as well as the common CWA simulant tributyl phosphate (TBP) on different surfaces/substrates are presented and discussed.

Band gap engineering of indium zinc oxide by nitrogen incorporation

Energy Technology Data Exchange (ETDEWEB)

Ortega, J.J., E-mail: jjosila@hotmail.com [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esq. Paseo la Bufa, Fracc. Progreso, C.P. 98060 Zacatecas (Mexico); Doctorado Institucional de Ingeniería y Ciencia de Materiales, Universidad Autónoma de San Luis Potosí, Av. Salvador Nava, Zona Universitaria, C.P. 78270 San Luis Potosí (Mexico); Aguilar-Frutis, M.A.; Alarcón, G. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del Instituto Politécnico Nacional, Unidad Legaría, Calz. Legaría No. 694, Col. Irrigación, C.P. 11500 México D.F. (Mexico); Falcony, C. [Departamento de Física, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional campus Zacatenco, Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, C.P. 07360 México D.F. (Mexico); and others

2014-09-15

Highlights: • IZON thin films were deposited by RF reactive sputtering at room temperature. • The effects of nitrogen on physical properties of IZO were analyzed. • Optical properties of IZON were studied by SE and UV–vis spectroscopy. • Adachi and classical parameters were quantitative and qualitatively congruent. • Nitrogen induces a gradual narrowing band gap from 3.5 to 2.5 eV on IZON films. - Abstract: The effects of nitrogen incorporation in indium zinc oxide films, as grown by RF reactive magnetron sputtering, on the structural, electrical and optical properties were studied. It was determined that the variation of the N{sub 2}/Ar ratio, in the reactive gas flux, was directly proportional to the nitrogen percentage measured in the sample, and the incorporated nitrogen, which substituted oxygen in the films induces changes in the band gap of the films. This phenomenon was observed by measurement of absorption and transmission spectroscopy in conjunction with spectral ellipsometry. To fit the ellipsometry spectra, the classical and Adachi dispersion models were used. The obtained optical parameters presented notable changes related to the increment of the nitrogen in the film. The band gap narrowed from 3.5 to 2.5 eV as the N{sub 2}/Ar ratio was increased. The lowest resistivity obtained for these films was 3.8 × 10{sup −4} Ω cm with a carrier concentration of 5.1 × 10{sup 20} cm{sup −3}.

Band gap engineering of indium zinc oxide by nitrogen incorporation

International Nuclear Information System (INIS)

Ortega, J.J.; Aguilar-Frutis, M.A.; Alarcón, G.; Falcony, C.

2014-01-01

Highlights: • IZON thin films were deposited by RF reactive sputtering at room temperature. • The effects of nitrogen on physical properties of IZO were analyzed. • Optical properties of IZON were studied by SE and UV–vis spectroscopy. • Adachi and classical parameters were quantitative and qualitatively congruent. • Nitrogen induces a gradual narrowing band gap from 3.5 to 2.5 eV on IZON films. - Abstract: The effects of nitrogen incorporation in indium zinc oxide films, as grown by RF reactive magnetron sputtering, on the structural, electrical and optical properties were studied. It was determined that the variation of the N 2 /Ar ratio, in the reactive gas flux, was directly proportional to the nitrogen percentage measured in the sample, and the incorporated nitrogen, which substituted oxygen in the films induces changes in the band gap of the films. This phenomenon was observed by measurement of absorption and transmission spectroscopy in conjunction with spectral ellipsometry. To fit the ellipsometry spectra, the classical and Adachi dispersion models were used. The obtained optical parameters presented notable changes related to the increment of the nitrogen in the film. The band gap narrowed from 3.5 to 2.5 eV as the N 2 /Ar ratio was increased. The lowest resistivity obtained for these films was 3.8 × 10 −4 Ω cm with a carrier concentration of 5.1 × 10 20 cm −3

Soliton-based ultrafast multi-wavelength nonlinear switching in dual-core photonic crystal fibre

International Nuclear Information System (INIS)

Stajanca, P; Pysz, D; Michalka, M; Bugar, I; Andriukaitis, G; Balciunas, T; Fan, G; Baltuska, A

2014-01-01

Systematic experimental study of ultrafast multi-wavelength all-optical switching performance in a dual-core photonic crystal fibre is presented. The focus is on nonlinearly induced switching between the two output ports at non-excitation wavelengths, which are generated during nonlinear propagation of femtosecond pulses in the anomalous dispersion region of a dual-core photonic crystal fibre made of multicomponent glass. Spatial and spectral characteristics of the fibre output radiation were measured separately for both fibre cores under various polarization and intensity conditions upon selective, individual excitation of each fibre core. Polarization-controlled nonlinear switching performance at multiple non-excitation wavelengths was demonstrated in the long-wavelength optical communication bands and beyond. Depending on the input pulse polarization, narrowband switching operation at 1560 nm and 1730 nm takes place with double core extinction ratio contrasts of 9 dB and 14.5 dB, respectively. Moreover, our approach allows switching with simultaneous wavelength shift from 1650 to 1775 nm with extinction ratio contrast larger than 18 dB. In addition, non-reciprocal behaviour of the soliton fission process under different fibre core excitations was observed and its effect on the multi-wavelength nonlinear switching performance was explained, taking into account the slight dual-core structure asymmetry. The obtained results represent ultrafast all-optical switching with an extended dimension of wavelength shift, controllable with both the input radiation intensity and the polarization by simple propagation along a 14 mm long fibre. (paper)

Physical properties and analytical models of band-to-band tunneling in low-bandgap semiconductors

International Nuclear Information System (INIS)

Shih, Chun-Hsing; Dang Chien, Nguyen

2014-01-01

Low-bandgap semiconductors, such as InAs and InSb, are widely considered to be ideal for use in tunnel field-effect transistors to ensure sufficient on-current boosting at low voltages. This work elucidates the physical and mathematical considerations of applying conventional band-to-band tunneling models in low-bandgap semiconductors, and presents a new analytical alternative for practical use. The high-bandgap tunneling generates most at maximum field region with shortest tunnel path, whereas the low-bandgap generations occur dispersedly because of narrow tunnel barrier. The local electrical field associated with tunneling-electron numbers dominates in low-bandgap materials. This work proposes decoupled electric-field terms in the pre-exponential factor and exponential function of generation-rate expressions. Without fitting, the analytical results and approximated forms exhibit great agreements with the sophisticated forms both in high- and low-bandgap semiconductors. Neither nonlocal nor local field is appropriate to be used in numerical simulations for predicting the tunneling generations in a variety of low- and high-bandgap semiconductors

Variable pattern of high-order harmonic spectra from a laser-produced plasma by using the chirped pulses of narrow-bandwidth radiation

International Nuclear Information System (INIS)

Ganeev, R. A.; Suzuki, M.; Baba, M.; Kuroda, H.; Redkin, P. V.

2007-01-01

Various plasmas prepared by laser ablation of the surfaces of solid targets were examined by the narrow-bandwidth radiation of different chirp and pulse durations. The high-order harmonics generated during laser-plasma interaction showed different brightness, wavelength shift, harmonic cutoff, and efficiency by using variable chirps of pump radiation. An analysis of harmonic optimization at these conditions is presented. The blueshifted and redshifted harmonics observed in this case were analyzed and attributed to the abundance of free electrons and self-phase modulation of the driving pulse. The resonance-induced enhancement of the 15th harmonic from GaN-nanoparticle-containing plasma caused by the tuning of harmonic wavelength close to the ionic transition was demonstrated

Gain claming in single-pass and double-pass L-band erbium-doped fiber amplifiers

International Nuclear Information System (INIS)

Harun, S.W.; Ahmad, H.

2004-01-01

Gain clamping is demonstrated in single-pass and double-pass long wavelength band erbium-doped fiber amplifiers. A C/L-band wavelength division multiplexing coupler is used in single-pass system to generate a laser at 1566 nm. The gain for the amplifier is clamped at 15.5 dB with gain variation of less than 0.2 dB from input signal power of -40 to -14 dBm with almost negligible noise figure penalty. However, the flatness of gain spectrum is slightly degraded due to the un-optimisation of erbium-doped fiber length. The advantage of this configuration is that the oscillating light does not appear at the output of the amplifier. A highly efficient gain-clamped long wavelength band erbium-doped fiber amplifiers with improved noise figure characteristic is demonstrated by simply adding a broadband conventional band fiber Bragg grating in double pass system. The combination of the fiber Bragg grating and optical circulator has created laser in the cavity for gain clamping. By adjusting the power combination of pumps 1 and 2, the clamped gain level can be controlled. The amplifier gain is clamped at 28.1 dB from -40 to -25 dBm with gain variation of less than 0.5 dB by setting the pumps 1 and 2 at 59.5 and 50.6 mW, respectively. The gain is also flat from 1574 nm to 1604 nm with gain variation of less than 3 dB. The corresponding noise figure varies from 5.6 to 7.6 dB, which is 0.8 to 2.6 dB reduced compared to those of unclamped amplifier (Authors)

Time-Dependent Response Versus Scan Angle for MODIS Reflective Solar Bands

Science.gov (United States)

Sun, Junqiang; Xiong, Xiaoxiong; Angal, Amit; Chen, Hongda; Wu, Aisheng; Geng, Xu

2014-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments currently operate onboard the National Aeronautics and Space Administration (NASA's) Terra and Aqua spacecraft, launched on December 18, 1999 and May 4, 2002, respectively. MODIS has 36 spectral bands, among which 20 are reflective solar bands (RSBs) covering a spectral range from 0.412 to 2.13 µm. The RSBs are calibrated on orbit using a solar diffuser (SD) and an SD stability monitor and with additional measurements from lunar observations via a space view (SV) port. Selected pseudo-invariant desert sites are also used to track the RSB on-orbit gain change, particularly for short-wavelength bands. MODIS views the Earth surface, SV, and the onboard calibrators using a two-sided scan mirror. The response versus scan angle (RVS) of the scan mirror was characterized prior to launch, and its changes are tracked using observations made at different angles of incidence from onboard SD, lunar, and Earth view (EV) measurements. These observations show that the optical properties of the scan mirror have experienced large wavelength-dependent degradation in both the visible and near infrared spectral regions. Algorithms have been developed to track the on-orbit RVS change using the calibrators and the selected desert sites. These algorithms have been applied to both Terra and Aqua MODIS Level 1B (L1B) to improve the EV data accuracy since L1B Collection 4, refined in Collection 5, and further improved in the latest Collection 6 (C6). In C6, two approaches have been used to derive the time-dependent RVS for MODIS RSB. The first approach relies on data collected from sensor onboard calibrators and mirror side ratios from EV observations. The second approach uses onboard calibrators and EV response trending from selected desert sites. This approach is mainly used for the bands with much larger changes in their time-dependent RVS, such as the Terra MODIS bands 1-4, 8, and 9 and the Aqua MODIS bands 8- and 9

Carbon dioxide on the satellites of Saturn: Results from the Cassini VIMS investigation and revisions to the VIMS wavelength scale

Science.gov (United States)

Cruikshank, D.P.; Meyer, A.W.; Brown, R.H.; Clark, R.N.; Jaumann, R.; Stephan, K.; Hibbitts, C.A.; Sandford, S.A.; Mastrapa, R.M.E.; Filacchione, G.; Ore, C.M.D.; Nicholson, P.D.; Buratti, B.J.; McCord, T.B.; Nelson, R.M.; Dalton, J.B.; Baines, K.H.; Matson, D.L.

2010-01-01

Several of the icy satellites of Saturn show the spectroscopic signature of the asymmetric stretching mode of C-O in carbon dioxide (CO2) at or near the nominal solid-phase laboratory wavelength of 4.2675 ??m (2343.3 cm-1), discovered with the Visible-Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft. We report here on an analysis of the variation in wavelength and width of the CO2 absorption band in the spectra of Phoebe, Iapetus, Hyperion, and Dione. Comparisons are made to laboratory spectra of pure CO2, CO2 clathrates, ternary mixtures of CO2 with other volatiles, implanted and adsorbed CO2 in non-volatile materials, and ab initio theoretical calculations of CO2 * nH2O. At the wavelength resolution of VIMS, the CO2 on Phoebe is indistinguishable from pure CO2 ice (each molecule's nearby neighbors are also CO2) or type II clathrate of CO2 in H2O. In contrast, the CO2 band on Iapetus, Hyperion, and Dione is shifted to shorter wavelengths (typically ???4.255 ??m (???2350.2 cm-1)) and broadened. These wavelengths are characteristic of complexes of CO2 with different near-neighbor molecules that are encountered in other volatile mixtures such as with H2O and CH3OH, and non-volatile host materials like silicates, some clays, and zeolites. We suggest that Phoebe's CO2 is native to the body as part of the initial inventory of condensates and now exposed on the surface, while CO2 on the other three satellites results at least in part from particle or UV irradiation of native H2O plus a source of C, implantation or accretion from external sources, or redistribution of native CO2 from the interior. The analysis presented here depends on an accurate VIMS wavelength scale. In preparation for this work, the baseline wavelength calibration for the Cassini VIMS was found to be distorted around 4.3 ??m, apparently as a consequence of telluric CO2 gas absorption in the pre-launch calibration. The effect can be reproduced by convolving a sequence of model detector

MULTI-WAVELENGTH PROBES OF OBSCURATION TOWARD THE NARROW-LINE REGION IN SEYFERT GALAXIES

International Nuclear Information System (INIS)

Kraemer, S. B.; Schmitt, H.R.; Crenshaw, D. M.; Melendez, M.; Turner, T.J.; Guainazzi, M.; Mushotzky, R.F.

2011-01-01

We present a study of reddening and absorption toward the narrow line regions (NLRs) in active galactic nuclei (AGNs) selected from the Revised Shapley-Ames, 12 μm, and Swift/Burst Alert Telescope samples. For the sources in host galaxies with inclinations of b/a > 0.5, we find that the mean ratio of [O III] λ5007, from ground-based observations, and [O IV] 28.59 μm, from Spitzer/Infrared Spectrograph observations, is a factor of two lower in Seyfert 2s than Seyfert 1s. The combination of low [O III]/[O IV] and [O III] λ4363/λ5007 ratios in Seyfert 2s suggests more extinction of emission from the NLR than in Seyfert 1s. Similar column densities of dusty gas, N H ∼ several x 10 21 cm -2 , can account for the suppression of both [O III] λ5007 and [O III] λ4363, as compared to those observed in Seyfert 1s. Also, we find that the X-ray line O VII λ22.1 A is weaker in Seyfert 2s, consistent with absorption by the same gas that reddens the optical emission. Using a Hubble Space Telescope/Space Telescope Imaging Spectrograph slitless spectrum of the Seyfert 1 galaxy NGC 4151, we estimate that only ∼30% of the [O III] λ5007 comes from within 30 pc of the central source, which is insufficient to account for the low [O III]/[O IV] ratios in Seyfert 2s. If Seyfert 2 galaxies have similar intrinsic [O III] spatial profiles, the external dusty gas must extend further out along the NLR, perhaps in the form of nuclear dust spirals that have been associated with fueling flows toward the AGN.

QUANTITATIVE ANALYSIS OF BANDED STRUCTURES IN DUAL-PHASE STEELS

Directory of Open Access Journals (Sweden)

Benoit Krebs

2011-05-01

Full Text Available Dual-Phase (DP steels are composed of martensite islands dispersed in a ductile ferrite matrix, which provides a good balance between strength and ductility. Current processing conditions (continuous casting followed by hot and cold rolling generate 'banded structures' i.e., irregular, parallel and alternating bands of ferrite and martensite, which are detrimental to mechanical properties and especially for in-use properties. We present an original and simple method to quantify the intensity and wavelength of these bands. This method, based on the analysis of covariance function of binary images, is firstly tested on model images. It is compared with ASTM E-1268 standard and appears to be more robust. Then it is applied on real DP steel microstructures and proves to be sufficiently sensitive to discriminate samples resulting from different thermo-mechanical routes.

A High-resolution Multi-wavelength Simultaneous Imaging System with Solar Adaptive Optics

Energy Technology Data Exchange (ETDEWEB)

Rao, Changhui; Zhu, Lei; Gu, Naiting; Rao, Xuejun; Zhang, Lanqiang; Bao, Hua; Kong, Lin; Guo, Youming; Zhong, Libo; Ma, Xue’an; Li, Mei; Wang, Cheng; Zhang, Xiaojun; Fan, Xinlong; Chen, Donghong; Feng, Zhongyi; Wang, Xiaoyun; Wang, Zhiyong, E-mail: gunaiting@ioe.ac.cn [The Key Laboratory on Adaptive Optics, Chinese Academy of Sciences, P.O. Box 350, Shuangliu, Chengdu 610209, Sichuan (China)

2017-10-01

A high-resolution multi-wavelength simultaneous imaging system from visible to near-infrared bands with a solar adaptive optics system, in which seven imaging channels, including the G band (430.5 nm), the Na i line (589 nm), the H α line (656.3 nm), the TiO band (705.7 nm), the Ca ii IR line (854.2 nm), the He i line (1083 nm), and the Fe i line (1565.3 nm), are chosen, is developed to image the solar atmosphere from the photosphere layer to the chromosphere layer. To our knowledge, this is the solar high-resolution imaging system with the widest spectral coverage. This system was demonstrated at the 1 m New Vaccum Solar Telescope and the on-sky high-resolution observational results were acquired. In this paper, we will illustrate the design and performance of the imaging system. The calibration and the data reduction of the system are also presented.

Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers

Science.gov (United States)

Palaferri, Daniele; Todorov, Yanko; Bigioli, Azzurra; Mottaghizadeh, Alireza; Gacemi, Djamal; Calabrese, Allegra; Vasanelli, Angela; Li, Lianhe; Davies, A. Giles; Linfield, Edmund H.; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme; Sirtori, Carlo

2018-04-01

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data

Measurement of flow fluctuations in single longitudinal mode pulsed ...

Indian Academy of Sciences (India)

2014-02-12

Feb 12, 2014 ... Page 1 ... Keywords. Dye lasers; single longitudinal mode; flow fluctuations. PACS Nos 42.55.Mv; 42.60.Mi; 42.60.By. 1. Introduction. Narrow-band dye lasers offer ... stabilized tunable laser source plays an important role for many applications as mentioned above [1]. For tight wavelength control, the ...

Narrow, duplicated internal auditory canal

Energy Technology Data Exchange (ETDEWEB)

Ferreira, T. [Servico de Neurorradiologia, Hospital Garcia de Orta, Avenida Torrado da Silva, 2801-951, Almada (Portugal); Shayestehfar, B. [Department of Radiology, UCLA Oliveview School of Medicine, Los Angeles, California (United States); Lufkin, R. [Department of Radiology, UCLA School of Medicine, Los Angeles, California (United States)

2003-05-01

A narrow internal auditory canal (IAC) constitutes a relative contraindication to cochlear implantation because it is associated with aplasia or hypoplasia of the vestibulocochlear nerve or its cochlear branch. We report an unusual case of a narrow, duplicated IAC, divided by a bony septum into a superior relatively large portion and an inferior stenotic portion, in which we could identify only the facial nerve. This case adds support to the association between a narrow IAC and aplasia or hypoplasia of the vestibulocochlear nerve. The normal facial nerve argues against the hypothesis that the narrow IAC is the result of a primary bony defect which inhibits the growth of the vestibulocochlear nerve. (orig.)

Flooding correlations in narrow channel

International Nuclear Information System (INIS)

Kim, S. H.; Baek, W. P.; Chang, S. H.

1999-01-01

Heat transfer in narrow gap is considered as important phenomena in severe accidents in nuclear power plants. Also in heat removal of electric chip. Critical heat flux(CHF) in narrow gap limits the maximum heat transfer rate in narrow channel. In case of closed bottom channel, flooding limited CHF occurrence is observed. Flooding correlations will be helpful to predict the CHF in closed bottom channel. In present study, flooding data for narrow channel geometry were collected and the work to recognize the effect of the span, w and gap size, s were performed. And new flooding correlations were suggested for high-aspect-ratio geometry. Also, flooding correlation was applied to flooding limited CHF data

Volume and surface photoemission from tungsten. I. Calculation of band structure and emission spectra

DEFF Research Database (Denmark)

Christensen, N. Egede; Feuerbacher, B.

1974-01-01

is obtained from an ad hoc potential based on a Dirac-Slater atomic calculation for the ground-state configuration and with full Slater exchange in the atomic as well as in the crystal potential. The selection of this best potential is justified by comparing the calculated band structure to Fermi...... of states. The present work includes a crude estimate of this surface density of states, which is derived from the bulk band structure by narrowing the d bands according to an effective number of neighbors per surface atom. Estimates of surface relaxation effects are also included.......The electronic energy-band structure of tungsten has been calculated by means of the relativistic-augmented-plane-wave method. A series of mutually related potentials are constructed by varying the electronic configuration and the amount of Slater exchange included. The best band structure...

Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

Energy Technology Data Exchange (ETDEWEB)

Bilguun, Amarsaikhan, E-mail: bilguun@pes.ee.tut.ac.jp; Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi, E-mail: takikawa@ee.tut.ac.jp [Toyohashi University of Technology, 1-1 Habarigaoka, Tempaku, Toyohashi 441-8580 (Japan); Tanoue, Hideto [Kitakyushu National College of Technology, 5-20-1, Kokuraminami, Kitakyushu, Fukuoka 802-0985 (Japan)

2016-02-01

In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD.

Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

Science.gov (United States)

Bilguun, Amarsaikhan; Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto

2016-02-01

In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD.

Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

International Nuclear Information System (INIS)

Bilguun, Amarsaikhan; Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto

2016-01-01

In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD

Superelastic NiTi memory alloy micro-tube under tension - nucleation and propagation of martensite band

International Nuclear Information System (INIS)

Li, Z.Q.; Sun, Q.P.

2000-01-01

The superelastic behavior of polycrystalline NiTi shape memory alloy micro-tube under tension is studied experimentally. The nominal stress-strain curve of the micro-tube is recorded. By using a special surface coating it is found that the deformation of the tube is via the nucleation and propagation of stress-induced martensite band. The experiments show that the martensite nucleates in the form of a spiral lens-shaped narrow band that is inclined at 61 to the axis of loading when the stress reaches the peak of stress-strain curve. The width and the length of the band grew gradually with increase of loading and finally joined and merged into a single band. The subsequent deformation of the tube is realized by the propagation of this cylindrical martensite band. (orig.)

Intercomparison of characterization techniques of filter radiometers in the ultraviolet region

International Nuclear Information System (INIS)

Abu-Kassem, I.; Karha, P.; Harrison, N. J.; Nevas, S.; Hartree, W. S.

2008-01-01

Narrow-band filter radiometers at 248 nm, 313 nm, 330 nm and 368 nm wavelengths were used to compare calibration facilities of spectral (irradiance) responsivity at HUT, NPL and BNM-INM. The results are partly in agreement within the stated uncertainties. Use of demanding artefacts in the intercomparison revealed that the wavelength scales of the participating institutes deviate more than expected. Such effects cannot be seen in typical intercomparisons of spectral responsivity or spectral transmittance, where spectrally neutral samples are used.(author)

Experimental performance assessment of the sub-band minimum variance beamformer for ultrasound imaging

DEFF Research Database (Denmark)

Diamantis, Konstantinos; Greenaway, Alan H.; Anderson, Tom

2017-01-01

Recent progress in adaptive beamforming techniques for medical ultrasound has shown that current resolution limits can be surpassed. One method of obtaining improved lateral resolution is the Minimum Variance (MV) beamformer. The frequency domain implementation of this method effectively divides...... the broadband ultrasound signals into sub-bands (MVS) to conform with the narrow-band assumption of the original MV theory. This approach is investigated here using experimental Synthetic Aperture (SA) data from wire and cyst phantoms. A 7 MHz linear array transducer is used with the SARUS experimental...

Smartphone snapshot mapping of skin chromophores under triple-wavelength laser illumination

Science.gov (United States)

Spigulis, Janis; Oshina, Ilze; Berzina, Anna; Bykov, Alexander

2017-09-01

Chromophore distribution maps are useful tools for skin malformation severity assessment and for monitoring of skin recovery after burns, surgeries, and other interactions. The chromophore maps can be obtained by processing several spectral images of skin, e.g., captured by hyperspectral or multispectral cameras during seconds or even minutes. To avoid motion artifacts and simplify the procedure, a single-snapshot technique for mapping melanin, oxyhemoglobin, and deoxyhemoglobin of in-vivo skin by a smartphone under simultaneous three-wavelength (448-532-659 nm) laser illumination is proposed and examined. Three monochromatic spectral images related to the illumination wavelengths were extracted from the smartphone camera RGB image data set with respect to crosstalk between the RGB detection bands. Spectral images were further processed accordingly to Beer's law in a three chromophore approximation. Photon absorption path lengths in skin at the exploited wavelengths were estimated by means of Monte Carlo simulations. The technique was validated clinically on three kinds of skin lesions: nevi, hemangiomas, and seborrheic keratosis. Design of the developed add-on laser illumination system, image-processing details, and the results of clinical measurements are presented and discussed.