Generation of a strong attosecond pulse train with an orthogonally polarized two-color laser field

International Nuclear Information System (INIS)

Kim, Chul Min; Kim, I Jong; Nam, Chang Hee

2005-01-01

We theoretically investigate the high-order harmonic generation from a neon atom irradiated by an intense two-color femtosecond laser pulse, in which the fundamental field and its second harmonic are linearly polarized and orthogonal to each other. In contrast to usual high-harmonic generation with linearly polarized fundamental field alone, a very strong and clean high-harmonic spectrum, consisting of both odd and even orders of harmonics, can be generated in the orthogonally polarized two-color laser field with proper selection of the relative phase between the fundamental and second-harmonic fields. In time domain, this results in a strong and regular attosecond pulse train. The origin of these behaviors is elucidated by analyzing semiclassical electron paths and by simulating high-harmonic generation quantum mechanically

Distilling two-center-interference information during tunneling of aligned molecules with orthogonally polarized two-color laser fields

Science.gov (United States)

Gao, F.; Chen, Y. J.; Xin, G. G.; Liu, J.; Fu, L. B.

2017-12-01

When electrons tunnel through a barrier formed by the strong laser field and the two-center potential of a diatomic molecule, a double-slit-like interference can occur. However, this interference effect can not be probed directly right now, as it is strongly coupled with other dynamical processes during tunneling. Here, we show numerically and analytically that orthogonally polarized two-color (OTC) laser fields are capable of resolving the interference effect in tunneling, while leaving clear footprints of this effect in photoelectron momentum distributions. Moreover, this effect can be manipulated by changing the relative field strength of OTC fields.

Generation of an XUV supercontinuum by optimization of the angle between polarization planes of two linearly polarized pulses in a multicycle two-color laser field

International Nuclear Information System (INIS)

Yao Jinping; Zeng Bin; Fu Yuxi; Chu Wei; Ni Jielei; Li Yao; Xiong Hui; Xu Han; Cheng Ya; Xu Zhizhan; Liu Xiaojun; Chen, J.

2010-01-01

We theoretically investigate the high-order harmonic generation (HHG) in helium using a two-color laser field synthesized by an intense 25-fs laser pulse at 800 nm and a relatively weak ∼43-fs laser pulse at 1400 nm. When the polarization between the two pulses is arranged at an angle of ∼73 deg., supercontinuum spectra are dramatically broadened to 180 eV, which is sufficient to support an isolated ∼73-as pulse without any phase compensation. The physical mechanisms behind the phenomenon are well explained in terms of quantum and classical analyses. Furthermore, in the long-pulse regime, this method of extending the supercontinuum spectrum shows the significant advantage over previous two-color HHG schemes.

Laser color recording unit

Science.gov (United States)

Jung, E.

1984-05-01

A color recording unit was designed for output and control of digitized picture data within computer controlled reproduction and picture processing systems. In order to get a color proof picture of high quality similar to a color print, together with reduced time and material consumption, a photographic color film material was exposed pixelwise by modulated laser beams of three wavelengths for red, green and blue light. Components of different manufacturers for lasers, acousto-optic modulators and polygon mirrors were tested, also different recording methods as (continuous tone mode or screened mode and with a drum or flatbed recording principle). Besides the application for the graphic arts - the proof recorder CPR 403 with continuous tone color recording with a drum scanner - such a color hardcopy peripheral unit with large picture formats and high resolution can be used in medicine, communication, and satellite picture processing.

Terahertz radiation driven by two-color laser pulses at near-relativistic intensities: Competition between photoionization and wakefield effects

Science.gov (United States)

González de Alaiza Martínez, P.; Davoine, X.; Debayle, A.; Gremillet, L.; Bergé, L.

2016-01-01

We numerically investigate terahertz (THz) pulse generation by linearly-polarized, two-color femtosecond laser pulses in highly-ionized argon. Major processes consist of tunneling photoionization and ponderomotive forces associated with transverse and longitudinal field excitations. By means of two-dimensional particle-in-cell (PIC) simulations, we reveal the importance of photocurrent mechanisms besides transverse and longitudinal plasma waves for laser intensities >1015 W/cm2. We demonstrate the following. (i) With two-color pulses, photoionization prevails in the generation of GV/m THz fields up to 1017 W/cm2 laser intensities and suddenly loses efficiency near the relativistic threshold, as the outermost electron shell of ionized Ar atoms has been fully depleted. (ii) PIC results can be explained by a one-dimensional Maxwell-fluid model and its semi-analytical solutions, offering the first unified description of the main THz sources created in plasmas. (iii) The THz power emitted outside the plasma channel mostly originates from the transverse currents. PMID:27255689

Two-color mid-infrared spectroscopy of optically doped semiconductors

International Nuclear Information System (INIS)

Forcales, M.; Klik, M.A.J.; Vinh, N.Q.; Phillips, J.; Wells, J-P.R.; Gregorkiewicz, T.

2003-01-01

Optical doping is an attractive method to tailor photonic properties of semiconductor matrices for development of solid-state electroluminescent structures. For practical applications, thermal stability of emission obtained from these materials is required. Thermal processes can be conveniently investigated by two-color spectroscopy in the visible and the mid-infrared. Free-electron laser is a versatile high-brilliance source of radiation in the latter spectral range. In this contribution, we briefly review some of the results obtained recently by the two-color spectroscopy with a free-electron laser in different semiconductors optically doped with rare earth and transition metal ions. Effects leading to both enhancement and quenching of emission from optical dopants will be presented. For InP:Yb, Si:Er, and Si:Cu activation of particular optically induced non-radiative recombination paths will be shown. For Si:Er and Si:Ag, observation of a low temperature optical memory effect will be reported

Generation and amplification of sub-THz radiation in a rare gases plasma formed by a two-color femtosecond laser pulse

Science.gov (United States)

Bogatskaya, A. V.; Volkova, E. A.; Popov, A. M.

2018-06-01

A new approach to constructing the source of radiation in the sub-THz frequency range is discussed. It is based on the strong-field ionization of heavy rare gases with Ramsauer minimum in the transport cross-section by a two-color () femtosecond laser pulse. Then a four-photon nonlinear process ( are the frequencies from the spectral width of the pulse with frequency ω, and is the frequency from the spectral width of the second harmonic 2ω) with a transition to the initial state results in a low-frequency spontaneous emission that can be amplified in the strongly nonequilibrium laser plasma if the position of the photoelectron peaks is located in the region of growing energy transport cross-section.

Attosecond pulse trains generated using two color laser fields

International Nuclear Information System (INIS)

Mauritsson, J.; Louisiana State University, Baton Rouge, LA; Johnsson, P.; Gustafsson, E.; L'Hullier, A.; Schafer, K.J.; Gaarde, M.B.

2006-01-01

Complete test of publication follows. We present the generation of attosecond pulse trains from a superposition of an infrared (IR) laser field and its second harmonic. Our attosecond pulses are synthesized by selecting a number of synchronized harmonics generated in argon. By adding the second harmonic to the driving field the inversion symmetry of generation process is broken and both odd and even harmonics are generated. Consecutive half cycles in the two color field differ beyond the simple sign change that occurs in a one color field and have very different shapes and amplitudes. This sub-cycle structure of the field, which governs the generation of the attosecond pulses, depends strongly on the relative phase and intensity of the two fields, thereby providing additional control over the generation process. The generation of attosecond pulses is frequently described using the semi-classical three step model where an electron is: (1) ionized through tunneling ionization during one half cycle; (2) reaccelerated back towards the ion core by the next half cycle; where it (3) recombines with the ground-state releasing the access energy in a short burst of light. In the two color field the symmetry between the ionizing and reaccelerating field is broken, which leads to two possible scenarios: the electron can either be ionized during a strong half cycle and reaccelerated by a weaker field or vice versa. The periodicity is a full IR cycle in both cases and hence two trains of attosecond pulses are generated which are offset from each other. The generation efficiency, however, is very different for the two cases since it is determined mainly by the electric field strength at the time of tunneling and one of the trains will therefore dominate the other. We investigate experimentally both the spectral and temporal structure of the generated attosecond pulse trains as a function of the relative phase between the two driving fields. We find that for a wide range of

Generation of an isolated sub-30 attosecond pulse in a two-color laser field and a static electric field

International Nuclear Information System (INIS)

Zhang Gang-Tai; Zhang Mei-Guang; Bai Ting-Ting

2012-01-01

We theoretically investigate high-order harmonic generation (HHG) from a helium ion model in a two-color laser field, which is synthesized by a fundamental pulse and its second harmonic pulse. It is shown that a supercontinuum spectrum can be generated in the two-color field. However, the spectral intensity is very low, limiting the application of the generated attosecond (as) pulse. By adding a static electric field to the synthesized two-color field, not only is the ionization yield of electrons contributing to the harmonic emission remarkably increased, but also the quantum paths of the HHG can be significantly modulated. As a result, the extension and enhancement of the supercontinuum spectrum are achieved, producing an intense isolated 26-as pulse with a bandwidth of about 170.5 eV. In particular, we also analyse the influence of the laser parameters on the ultrabroad supercontinuum spectrum and isolated sub-30-as pulse generation. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Ar 3p photoelectron sideband spectra in two-color XUV + NIR laser fields

Science.gov (United States)

Minemoto, Shinichirou; Shimada, Hiroyuki; Komatsu, Kazma; Komatsubara, Wataru; Majima, Takuya; Mizuno, Tomoya; Owada, Shigeki; Sakai, Hirofumi; Togashi, Tadashi; Yoshida, Shintaro; Yabashi, Makina; Yagishita, Akira

2018-04-01

We performed photoelectron spectroscopy using femtosecond XUV pulses from a free-electron laser and femtosecond near-infrared pulses from a synchronized laser, and succeeded in measuring Ar 3p photoelectron sideband spectra due to the two-color above-threshold ionization. In our calculations of the first-order time-dependent perturbation theoretical model based on the strong field approximation, the photoelectron sideband spectra and their angular distributions are well reproduced by considering the timing jitter between the XUV and the NIR pulses, showing that the timing jitter in our experiments was distributed over the width of {1.0}+0.4-0.2 ps. The present approach can be used as a method to evaluate the timing jitter inevitable in FEL experiments.

Detecting the propagation effect of terahertz wave inside the two-color femtosecond laser filament in the air

Science.gov (United States)

Zhao, J.; Zhang, X.; Li, S.; Liu, C.; Chen, Y.; Peng, Y.; Zhu, Y.

2018-03-01

In this work, to decide the existence of terahertz (THz) wave propagation effect, THz pulses emitted from a blocked two-color femtosecond laser filament with variable length were recorded by a standard electric-optic sampling setup. The phenomenon of temporal advance of the THz waveform's peak with the increasing filament length has been observed. Together with another method of knife-edge measurement which aims at directly retrieving the THz beam diameter, both the experimental approaches have efficiently indicated the same filament range within which THz wave propagated inside the plasma column. At last, a preliminary two-dimensional near-field scanning imaging of the THz spot inside the cross section of the filament has been suggested as the third way to determine the issue of THz wave propagation effect.

Photoionization and trans-to-cis isomerization of β-cyclodextrin-encapsulated azobenzene induced by two-color two-laser-pulse excitation.

Science.gov (United States)

Takeshita, Tatsuya; Hara, Michihiro

2018-03-15

Azobenzene (1) and the complex resulting from the incorporation of 1 with cyclodextrin (1/CD) are attractive for light-driven applications such as micromachining and chemical biology tools. The highly sensitive photoresponse of 1 is crucial for light-driven applications containing both 1 and 1/CD to reach their full potential. In this study, we investigated the photoionization and trans-to-cis isomerization of 1/CD induced by one- and two-color two-laser pulse excitation. Photoionization of 1/CD, which was induced by stepwise two-photon absorption, was observed using laser pulse excitation at 266nm. Additionally, simultaneous irradiation with 266 and 532nm laser pulses increased the trans-to-cis isomerization yield (Υ t→c ) by 27%. It was concluded that the increase in Υ t→c was caused by the occurrence of trans-to-cis isomerization in the higher-energy singlet state (S n ), which was reached by S 1 →S n transition induced by laser pulse excitation at 532nm. The results of this study are potentially applicable in light-driven applications such as micromachining and chemical biology tools. Copyright © 2018 Elsevier B.V. All rights reserved.

Precision improvement of frequency-modulated continuous-wave laser ranging system with two auxiliary interferometers

Science.gov (United States)

Shi, Guang; Wang, Wen; Zhang, Fumin

2018-03-01

The measurement precision of frequency-modulated continuous-wave (FMCW) laser distance measurement should be proportional to the scanning range of the tunable laser. However, the commercial external cavity diode laser (ECDL) is not an ideal tunable laser source in practical applications. Due to the unavoidable mode hopping and scanning nonlinearity of the ECDL, the measurement precision of FMCW laser distance measurements can be substantially affected. Therefore, an FMCW laser ranging system with two auxiliary interferometers is proposed in this paper. Moreover, to eliminate the effects of ECDL, the frequency-sampling method and mode hopping influence suppression method are employed. Compared with a fringe counting interferometer, this FMCW laser ranging system has a measuring error of ± 20 μm at the distance of 5.8 m.

Plasmonic laser printing for ink-free color decoration

DEFF Research Database (Denmark)

Zhu, Xiaolong; Vannahme, Christoph; Højlund-Nielsen, Emil

2016-01-01

Here we show a method of color printing on nanoimprinted plasmonic metasurfaces [1] using laser post-writing. Laser pulses induce transient local heat generation that leads to melting and reshaping of the imprinted nanostructures [2]. This leads to melting and reshaping of the imprinted 20nm Al...... also be used on a larger scale to personify products such as mobile phones with unique decorations, names, etc‥ This laser technology may create environmentally sound color printing solutions and simplify the production for consumer products....... structures embedded in plastics. Depending on the laser pulse energy density, different surface morphologies that support different plasmonic resonances leading to different color appearances can be created. Color printing by this technology has several advantages over dye technology: ink/toner-free, sub...

Scanning laser densitometry and color perimetry demonstrate reduced photopigment density and sensitivity in two patients with retinal degeneration.

Science.gov (United States)

Tornow, R P; Stilling, R; Zrenner, E

1999-10-01

To test the feasibility of scanning laser densitometry with a modified Rodenstock scanning laser ophthalmoscope (SLO) to measure the rod and cone photopigment distribution in patients with retinal diseases. Scanning laser densitometry was performed using a modified Rodenstock scanning laser ophthalmoscope. The distribution of the photopigments was calculated from dark adapted and bleached images taken with the 514 nm laser of the SLO. This wavelength is absorbed by rod and cone photopigments. Discrimination is possible due to their different spatial distribution. Additionally, to measure retinal sensitivity profiles, dark adapted two color static perimetry with a Tübinger manual perimeter was performed along the horizontal meridian with 1 degree spacing. A patient with retinitis pigmentosa had slightly reduced photopigment density within the central +/- 5 degrees but no detectable photopigment for eccentricities beyond 5 degrees. A patient with cone dystrophy had nearly normal pigment density beyond +/- 5 degrees, but considerably reduced photopigment density within the central +/- 5 degrees. Within the central +/- 5 degrees, the patient with retinitis pigmentosa had normal sensitivity for the red stimulus and reduced sensitivity for the green stimulus. There was no measurable function beyond 7 degrees. The patient with cone dystrophy had normal sensitivity for the green stimulus outside the foveal center and reduced sensitivity for the red stimulus at the foveal center. The results of color perimetry for this patient with a central scotoma were probably influenced by eccentric fixation. Scanning laser densitometry with a modified Rodenstock SLO is a useful method to assess the human photopigment distribution. Densitometry results were confirmed by dark adapted two color static perimetry. Photopigment distribution and retinal sensitivity profiles can be measured with high spatial resolution. This may help to measure exactly the temporal development of retinal

Color speckle in laser displays

Science.gov (United States)

Kuroda, Kazuo

2015-07-01

At the beginning of this century, lighting technology has been shifted from discharge lamps, fluorescent lamps and electric bulbs to solid-state lighting. Current solid-state lighting is based on the light emitting diodes (LED) technology, but the laser lighting technology is developing rapidly, such as, laser cinema projectors, laser TVs, laser head-up displays, laser head mounted displays, and laser headlamps for motor vehicles. One of the main issues of laser displays is the reduction of speckle noise1). For the monochromatic laser light, speckle is random interference pattern on the image plane (retina for human observer). For laser displays, RGB (red-green-blue) lasers form speckle patterns independently, which results in random distribution of chromaticity, called color speckle2).

Future of laser electrophotographic technology for color document printing

Science.gov (United States)

Shahin, Michael M.

1997-04-01

Recent years have witnessed the development of laser electrophotography as one of the major technologies for document printing, serving a wide range of market applications. With the evolution of color and market demand for color hard copy, electrophotography is again taking center stage to serve the customer need in quality, cost and convenience. Today, electrophotographic technology is used to offer products for color document printing for desktop, mid-volume and high-speed applications. Total cost of ownership, convenience and quality today favor the use of this technology over alternatives in many applications. Development of higher speed color electrophotographic engines demands very high speed, Raster Input Processors and pre-press applications that are expected to become available in the market during the next five years. This presentation will cover the changing environment of office communication and the continuing role of electrophotography in color document printing.

Silicon isotope separation utilizing infrared multiphoton dissociation of Si2F6 irradiated with two-color CO2 laser light

International Nuclear Information System (INIS)

Yokoyama, Atsushi; Ohba, Hironori; Hashimoto, Masashi; Arai, Shigeyoshi

2002-01-01

Silicon isotope separation has been done by utilizing the Infrared Multiphoton Dissociation (IRMPD) of Si 2 F 6 irradiated with two-color CO 2 laser lights. The two-color excitation method improved the separation efficiency keeping the high enrichment factors. For example, 99.74% of 28 Si was obtained at 49.63% dissociation of Si 2 F 6 after the simultaneous irradiation of 200 pulses with 966.23 cm -1 photons (0.084 J/cm 2 ) and 954.55 cm -1 photons (0.658 J/cm 2 ), while 2000 pulses were needed to obtain 99.35% of 28 Si at 35.6% dissociation in the case of only one-color irradiation at 954.55 cm -1 (0.97 J/cm 2 ). (author)

Laser-induced plasmas in air studied using two-color interferometry

International Nuclear Information System (INIS)

Yang, Zefeng; Wu, Jian; Li, Xingwen; Han, Jiaxun; Jia, Shenli; Qiu, Aici; Wei, Wenfu

2016-01-01

Temporally and spatially resolved density profiles of Cu atoms, electrons, and compressed air, from laser-induced copper plasmas in air, are measured using fast spectral imaging and two-color interferometry. From the intensified CCD images filtered by a narrow-band-pass filter centered at 515.32 nm, the Cu atoms expansion route is estimated and used to determine the position of the fracture surface between the Cu atoms and the air. Results indicate that the Cu atoms density at distances closer to the target (0–0.4 mm) is quite low, with the maximum density appearing at the edge of the plasma's core being ∼4.6 × 10"2"4" m"−"3 at 304 ns. The free electrons are mainly located in the internal region of the plume, which is supposed to have a higher temperature. The density of the shock wave is (4–6) × 10"2"5" m"−"3, corresponding to air compression of a factor of 1.7–2.5.

Laser-induced plasmas in air studied using two-color interferometry

Energy Technology Data Exchange (ETDEWEB)

Yang, Zefeng; Wu, Jian, E-mail: jxjawj@mail.xjtu.edu.cn; Li, Xingwen; Han, Jiaxun; Jia, Shenli; Qiu, Aici [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Shaanxi 710049 (China); Wei, Wenfu [School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

2016-08-15

Temporally and spatially resolved density profiles of Cu atoms, electrons, and compressed air, from laser-induced copper plasmas in air, are measured using fast spectral imaging and two-color interferometry. From the intensified CCD images filtered by a narrow-band-pass filter centered at 515.32 nm, the Cu atoms expansion route is estimated and used to determine the position of the fracture surface between the Cu atoms and the air. Results indicate that the Cu atoms density at distances closer to the target (0–0.4 mm) is quite low, with the maximum density appearing at the edge of the plasma's core being ∼4.6 × 10{sup 24 }m{sup −3} at 304 ns. The free electrons are mainly located in the internal region of the plume, which is supposed to have a higher temperature. The density of the shock wave is (4–6) × 10{sup 25 }m{sup −3}, corresponding to air compression of a factor of 1.7–2.5.

Quantum manipulation of two-color stationary light: Quantum wavelength conversion

International Nuclear Information System (INIS)

Moiseev, S. A.; Ham, B. S.

2006-01-01

We present a quantum manipulation of a traveling light pulse using electromagnetically induced transparency-based slow light phenomenon for the generation of two-color stationary light. We theoretically discuss the two-color stationary light for the quantum wavelength conversion process in terms of pulse area, energy transfer, and propagation directions. The condition of the two-color stationary light pulse generation has been found and the quantum light dynamics has been studied analytically in the adiabatic limit. The quantum frequency conversion rate of the traveling light is dependent on the spatial spreading of the two-color stationary light pulse and can be near unity in an optically dense medium for the optimal frequencies of the control laser fields

Momentum spectra of electrons rescattered from rare-gas targets following their extraction by one- and two-color femtosecond laser pulses

International Nuclear Information System (INIS)

Ray, D.; Chen Zhangjin; De, S.; Cao, W.; Le, A. T.; Lin, C. D.; Cocke, C. L.; Litvinyuk, I. V.; Kling, M. F.

2011-01-01

We have used velocity-map imaging to measure the three-dimensional momenta of electrons rescattered from Xe and Ar following the liberation of the electrons from these atoms by 45 fs, 800 nm intense laser pulses. Strong structure in the rescattering region is observed in both angle and energy, and is interpreted in terms of quantitative rescattering (QRS) theory. Momentum images have also been taken with two-color (800 nm + 400 nm) pulses on Xe targets. A strong dependence of the spectra on the relative phase of the two colors is observed in the rescattering region. Interpretation of the phase dependence using both QRS theory and a full solution to the time-dependent Schroedinger equation shows that the rescattered electrons provide a much more robust method for determining the relative phase of the two colors than do the direct electrons.

Double ionization of nitrogen molecules in orthogonal two-color femtosecond laser fields

Science.gov (United States)

Song, Qiying; Li, Hui; Wang, Junping; Lu, Peifen; Gong, Xiaochun; Ji, Qinying; Lin, Kang; Zhang, Wenbin; Ma, Junyang; Li, Hanxiao; Zeng, Heping; He, Feng; Wu, Jian

2018-04-01

Double ionization of nitrogen molecules in orthogonally polarized two-color femtosecond laser fields is investigated by varying the relative intensity between the fundamental wave (FW) and its second harmonic (SH) components. The yield ratios of the double ionization channels, i.e., the non-dissociative {{{{N}}}2}2+ and Coulomb exploded (N+, N+), to the singly charged N2 + channel exhibit distinct dependences on the relative strength between the FW and SH fields. As the intensity ratio of SH to FW increases, the yield ratio of (N+, N+)/N2 + gradually increases, while the ratio of {{{{N}}}2}2+/N2 + first descends and then increases constituting a valley shape which is similar to the behavior of Ar2+/Ar+ observed in the same experimental condition. Based on the classical trajectory simulations, we found that the different characteristics of the two doubly ionized channels stem from two mechanisms, i.e., the {{{{N}}}2}2+ is mostly accessed by the (e, 2e) impact ionization while the recollision-induced excitation with subsequent ionization plays an important role in producing the (N+, N+) channel.

Ultra-low emittance beam generation using two-color ionization injection in a CO2 laser-driven plasma accelerator

International Nuclear Information System (INIS)

Schroeder, Carl; Benedetti, Carlo; Bulanov, Stepan; Chen, Min; Esarey, Eric; Geddes, Cameron; Vay, J.; Yu, Lule; Leemans, Wim

2015-01-01

Ultra-low emittance (tens of nm) beams can be generated in a plasma accelerator using ionization injection of electrons into a wakefield. An all-optical method of beam generation uses two laser pulses of different colors. A long-wavelength drive laser pulse (with a large ponderomotive force and small peak electric field) is used to excite a large wakefield without fully ionizing a gas, and a short-wavelength injection laser pulse (with a small ponderomotive force and large peak electric field), co-propagating and delayed with respect to the pump laser, to ionize a fraction of the remaining bound electrons at a trapped wake phase, generating an electron beam that is accelerated in the wake. The trapping condition, the ionized electron distribution, and the trapped bunch dynamics are discussed. Expressions for the beam transverse emittance, parallel and orthogonal to the ionization laser polarization, are presented. An example is shown using a 10-micron CO 2 laser to drive the wake and a frequency-doubled Ti:Al 2 O 3 laser for ionization injection.

Single attosecond pulse generation in an orthogonally polarized two-color laser field combined with a static electric field

International Nuclear Information System (INIS)

Xia Changlong; Zhang Gangtai; Wu Jie; Liu Xueshen

2010-01-01

We investigate theoretic high-order harmonic generation and single attosecond pulse generation in an orthogonally polarized two-color laser field, which is synthesized by a mid-infrared (IR) pulse (12.5 fs, 2000 nm) in the y component and a much weaker (12 fs, 800 nm) pulse in the x component. We find that the width of the harmonic plateau can be extended when a static electric field is added in the y component. We also investigate emission time of harmonics in terms of a time-frequency analysis to illustrate the physical mechanism of high-order harmonic generation. We calculate the ionization rate using the Ammosov-Delone-Krainov model and interpret the variation of harmonic intensity for different static electric field strengths. When the ratio of strengths of the static and the y-component laser fields is 0.1, a continuous harmonic spectrum is formed from 220 to 420 eV. By superposing a properly selected range of the harmonic spectrum from 300 to 350 eV, an isolated attosecond pulse with a duration of about 75 as is obtained, which is near linearly polarized.

Two-color visible/vacuum ultraviolet photoelectron imaging dynamics of Br2.

Science.gov (United States)

Plenge, Jürgen; Nicolas, Christophe; Caster, Allison G; Ahmed, Musahid; Leone, Stephen R

2006-10-07

An experimental two-color photoionization dynamics study of laser-excited Br2 molecules is presented, combining pulsed visible laser excitation and tunable vacuum ultraviolet (VUV) synchrotron radiation with photoelectron imaging. The X 1Sigmag + -B 3Pi0+u transition in Br2 is excited at 527 nm corresponding predominantly to excitation of the v' = 28 vibrational level in the B 3Pi0+u state. Tunable VUV undulator radiation in the energy range of 8.40-10.15 eV is subsequently used to ionize the excited molecules to the X 2Pi32,12 state of the ion, and the ionic ground state is probed by photoelectron imaging. Similar experiments are performed using single-photon synchrotron ionization in the photon energy range of 10.75-12.50 eV without any laser excitation. Photoelectron kinetic energy distributions are extracted from the photoelectron images. In the case of two-color photoionization using resonant excitation of the intermediate B 3Pi0+u state, a broad distribution of photoelectron kinetic energies is observed, and in some cases even a bimodal distribution, which depends on the VUV photon energy. In contrast, for single-photon ionization, a single nearly Gaussian-shaped distribution is observed, which shifts to higher energy with photon energy. Simulated spectra based on Franck-Condon factors for the transitions Br2(X 1Sigmag+, v" = 0)-Br2 +(X 2Pi12,32, v+) and Br2(B 3Pi0+u, v' = 28)-Br2 +(X 2Pi12,32, v+) are generated. Comparison of these calculated spectra with the measured images suggests that the differences in the kinetic energy distributions for the two ionization processes reflect the different extensions of the vibrational wave functions in the v" = 0 electronic ground state (X 1Sigmag+) versus the electronically and vibrationally excited state (B 3Pi0+u, v' = 28).

Rovibronically selected and resolved two-color laser photoionization and photoelectron study of cobalt carbide cation.

Science.gov (United States)

Huang, Huang; Chang, Yih Chung; Luo, Zhihong; Shi, Xiaoyu; Lam, Chow-Shing; Lau, Kai-Chung; Ng, C Y

2013-03-07

We have conducted a two-color visible-ultraviolet (VIS-UV) resonance-enhanced laser photoionization efficiency and pulsed field ionization-photoelectron (PFI-PE) study of gaseous cobalt carbide (CoC) near its ionization onset in the total energy range of 61,200-64,510 cm(-1). The cold gaseous CoC sample was prepared by a laser ablation supersonically cooled beam source. By exciting CoC molecules thus generated to single N' rotational levels of the intermediate CoC∗((2)Σ(+); v') state using a VIS dye laser prior to UV laser photoionization, we have obtained N(+) rotationally resolved PFI-PE spectra for the CoC(+)(X(1)Σ(+); v(+) = 0 and 1) ion vibrational bands free from interference by impurity species except Co atoms produced in the ablation source. The rotationally selected and resolved PFI-PE spectra have made possible unambiguous rotational assignments, yielding accurate values for the adiabatic ionization energy of CoC(X(2)Σ(+)), IE(CoC) = 62,384.3 ± 0.6 cm(-1) (7.73467 ± 0.00007 eV), the vibrational frequency ωe (+) = 985.6 ± 0.6 cm(-1), the anharmonicity constant ωe (+)χe (+) = 6.3 ± 0.6 cm(-1), the rotational constants (Be (+) = 0.7196 ± 0.0005 cm(-1), αe (+) = 0.0056 ± 0.0008 cm(-1)), and the equilibrium bond length re (+) = 1.534 Å for CoC(+)(X(1)Σ(+)). The observation of the N(+) = 0 level in the PFI-PE measurement indicates that the CoC(+) ground state is of (1)Σ(+) symmetry. Large ΔN(+) = N(+) - N' changes up to 6 are observed for the photoionization transitions CoC(+)(X(1)Σ(+); v(+) = 0-2; N(+)) ← CoC∗((2)Σ(+); v'; N' = 6, 7, 8, and 9). The highly precise energetic and spectroscopic data obtained in the present study have served as a benchmark for testing theoretical predictions based on state-of-the-art ab initio quantum calculations at the CCSDTQ∕CBS level of theory as presented in the companion article.

Stability diagrams for continuous wide-range control of two mutually delay-coupled semiconductor lasers

International Nuclear Information System (INIS)

Junges, Leandro; Gallas, Jason A C

2015-01-01

The dynamics of two mutually delay-coupled semiconductor lasers has been frequently studied experimentally, numerically, and analytically either for weak or strong detuning between the lasers. Here, we present a systematic numerical investigation spanning all detuning ranges. We report high-resolution stability diagrams for wide ranges of the main control parameters of the laser, as described by the Lang–Kobayashi model. In particular, we detail the parameter influence on dynamical performance and map the distribution of chaotic pulsations and self-generated periodic spiking with arbitrary periodicity. Special attention is given to the unfolding of regular pulse packages for both symmetric and non-symmetric configurations with respect to detuning. The influence of the delay –time on the self-organization of periodic and chaotic laser phases as a function of the coupling and detuning is also described in detail. (paper)

Blue and Orange Two-Color CW Laser Based on Single-Pass Second-Harmonic and Sum-Frequency Generation in MgO:PPLN

Directory of Open Access Journals (Sweden)

Dismas K. Choge

2018-04-01

Full Text Available We demonstrate a compact blue and orange-two color continuous wave laser source emitting at 487 nm and from 597.4 to 600.3 nm, respectively. The temperature tunable coherent orange radiation is achieved by frequency mixing 974 nm laser diode (LD and a C-band amplified spontaneous emission laser source while the temperature insensitive blue radiation is generated by second-order quasi-phase-matching frequency doubling of 974 nm LD. We implement the simultaneous nonlinear processes in a single magnesium oxide doped periodically poled lithium niobate bulk crystal without the need of an aperiodic design.

Event-Based Color Segmentation With a High Dynamic Range Sensor

Directory of Open Access Journals (Sweden)

Alexandre Marcireau

2018-04-01

Full Text Available This paper introduces a color asynchronous neuromorphic event-based camera and a methodology to process color output from the device to perform color segmentation and tracking at the native temporal resolution of the sensor (down to one microsecond. Our color vision sensor prototype is a combination of three Asynchronous Time-based Image Sensors, sensitive to absolute color information. We devise a color processing algorithm leveraging this information. It is designed to be computationally cheap, thus showing how low level processing benefits from asynchronous acquisition and high temporal resolution data. The resulting color segmentation and tracking performance is assessed both with an indoor controlled scene and two outdoor uncontrolled scenes. The tracking's mean error to the ground truth for the objects of the outdoor scenes ranges from two to twenty pixels.

Experimental investigations on fiber laser color marking of steels

Energy Technology Data Exchange (ETDEWEB)

Amara, E.H., E-mail: amara@cdta.dz; Haïd, F.; Noukaz, A.

2015-10-01

Highlights: • We develop an experimental approach with the aim to bring a contribution to the comprehension of the occurring phenomena during laser color marking of steels. • We have used a home-made marking device composed of a pulsed fiber laser and galvanometric mirrors. • Both commercial and elaborated in laboratory steels have been used as samples. • The experiments have been performed for different laser beam operating parameters, under normal atmospheric conditions. • The treated samples were analyzed either by optical and scanning electronic microscopy, as well as by energy dispersion spectroscopy. - Abstract: We develop an experimental approach with the aim to bring a contribution to the comprehension of the occurring phenomena during laser color marking of steels. A home-made marking device using a pulsed fiber laser has been used to treat steel samples under different laser beam operating parameters, for different compositions of the processed steel, and at normal atmospheric conditions. The treated samples were analyzed either by optical and scanning electronic microscopy, as well as by energy dispersion spectroscopy. The results show the influence of the operating parameters on the obtained colors.

Experimental investigations on fiber laser color marking of steels

International Nuclear Information System (INIS)

Amara, E.H.; Haïd, F.; Noukaz, A.

2015-01-01

Highlights: • We develop an experimental approach with the aim to bring a contribution to the comprehension of the occurring phenomena during laser color marking of steels. • We have used a home-made marking device composed of a pulsed fiber laser and galvanometric mirrors. • Both commercial and elaborated in laboratory steels have been used as samples. • The experiments have been performed for different laser beam operating parameters, under normal atmospheric conditions. • The treated samples were analyzed either by optical and scanning electronic microscopy, as well as by energy dispersion spectroscopy. - Abstract: We develop an experimental approach with the aim to bring a contribution to the comprehension of the occurring phenomena during laser color marking of steels. A home-made marking device using a pulsed fiber laser has been used to treat steel samples under different laser beam operating parameters, for different compositions of the processed steel, and at normal atmospheric conditions. The treated samples were analyzed either by optical and scanning electronic microscopy, as well as by energy dispersion spectroscopy. The results show the influence of the operating parameters on the obtained colors

Range and stability of structural colors generated by Morpho-inspired color reflectors.

Science.gov (United States)

Chung, Kyungjae; Shin, Jung H

2013-05-01

The range and stability of structural colors generated by Morpho-inspired color reflectors are investigated. We find that despite the internal randomness of such structures that gives rise to their Morpho-like angle-independent iridescence, their colors under ambient lighting condition can be predicted by simple transfer-matrix calculations of corresponding planar multilayer structures. By calculating the possible range of colors generated by multilayers of different structures and material combinations using such transfer-matrix methods, we find that low-refractive index multilayers with intrastructure absorption, such as the melanin-containing chitin/air multilayer structure from the Morpho butterflies, can provide not only the most pure structural colors with the largest color gamut, but also the highest stability of color against variations in multilayer structure.

Gamut mapping in a high-dynamic-range color space

Science.gov (United States)

Preiss, Jens; Fairchild, Mark D.; Ferwerda, James A.; Urban, Philipp

2014-01-01

In this paper, we present a novel approach of tone mapping as gamut mapping in a high-dynamic-range (HDR) color space. High- and low-dynamic-range (LDR) images as well as device gamut boundaries can simultaneously be represented within such a color space. This enables a unified transformation of the HDR image into the gamut of an output device (in this paper called HDR gamut mapping). An additional aim of this paper is to investigate the suitability of a specific HDR color space to serve as a working color space for the proposed HDR gamut mapping. For the HDR gamut mapping, we use a recent approach that iteratively minimizes an image-difference metric subject to in-gamut images. A psychophysical experiment on an HDR display shows that the standard reproduction workflow of two subsequent transformations - tone mapping and then gamut mapping - may be improved by HDR gamut mapping.

Selective appearance of several laser-induced periodic surface structure patterns on a metal surface using structural colors produced by femtosecond laser pulses

Energy Technology Data Exchange (ETDEWEB)

Yao Jianwu; Zhang Chengyun; Liu Haiying; Dai Qiaofeng; Wu Lijun [Laboratory of Photonic Information Technology, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China); Lan, Sheng, E-mail: slan@scnu.edu.cn [Laboratory of Photonic Information Technology, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006 (China); Gopal, Achanta Venu [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Trofimov, Vyacheslav A.; Lysak, Tatiana M. [Department of Computational Mathematics and Cybernetics, M. V. Lomonosov Moscow State University, Moscow 119992 (Russian Federation)

2012-07-15

Ripples with a subwavelength period were induced on the surface of a stainless steel (301 L) foil by femtosecond laser pulses. By optimizing the irradiation fluence of the laser pulses and the scanning speed of the laser beam, ripples with large amplitude ({approx}150 nm) and uniform period could be obtained, rendering vivid structural colors when illuminating the surface with white light. It indicates that these ripples act as a surface grating that diffracts light efficiently. The strong dependence of the ripple orientation on the polarization of laser light offers us the opportunity of decorating different regions of the surface with different types of ripples. As a result, different patterns can be selectively displayed with structural color when white light is irradiated on the surface from different directions. More interestingly, we demonstrated the possibility of decorating the same region with two or more types of ripples with different orientations. In this way, different patterns with spatial overlapping can be selectively displayed with structural color. This technique may find applications in the fields of anti-counterfeiting, color display, decoration, encryption and optical data storage.

Color center lasers passively mode locked by quantum wells

International Nuclear Information System (INIS)

Islam, M.N.; Soccolich, C.E.; Bar-Joseph, I.; Sauer, N.; Chang, T.Y.; Miller, B.I.

1989-01-01

This paper describes how, using multiple quantum well (MQW) saturable absorbers, the authors passively mode locked a NaCl color center laser to produce 275 fs transform-limited, pedestal-free pulses with as high as 3.7 kW peak power. The pulses are tunable from λ = 1.59 to 1.7 μm by choosing MQW's with different bandgaps. They shortened the output pulses from the laser to 25 fs using the technique of soliton compression in a fiber. The steady-state operation of the laser requires the combination of a fast saturable absorber and gain saturation. In addition to the NaCl laser, they passively mode locked a Tl 0 (1):KCl color center laser and produced -- 22 ps pulses. Although the 275 fs pulses from the NaCl laser are Gaussian, when broadened, the pulses acquire an asymmetric spectrum because of carrier-induced refractive index changes

Full-color laser cathode ray tube (L-CRT) projector

Science.gov (United States)

Kozlovskiy, Vladimir; Nasibov, Alexander S.; Popov, Yuri M.; Reznikov, Parvel V.; Skasyrsky, Yan K.

1995-04-01

A full color TV projector based on three laser cathode-ray tubes (L-CRT) is described. A water-cooled laser screen (LS) is the radiation element of the L-CRT. We have produced three main colors (blue, green and red) by using the LS made of three II-VI compounds: ZnSe ((lambda) equals 475 nm), CdS ((lambda) equals 530 nm) and ZnCdSe (630 nm). The total light flow reaches 1500 Lm, and the number of elements per line is not less than 1000. The LS efficiency may be about 10 Lm/W. In our experiments we have tested new electron optics: - (30 - 37) kV are applied to the cathode unit of the electron gun; the anode of the e-gun and the e-beam intensity modulator are under low potential; the LS has a potential + (30 - 37) kV. The accelerating voltage is divided into two parts, and this enables us to diminish the size and weight of the projector.

Evaluation of color encodings for high dynamic range pixels

Science.gov (United States)

Boitard, Ronan; Mantiuk, Rafal K.; Pouli, Tania

2015-03-01

Traditional Low Dynamic Range (LDR) color spaces encode a small fraction of the visible color gamut, which does not encompass the range of colors produced on upcoming High Dynamic Range (HDR) displays. Future imaging systems will require encoding much wider color gamut and luminance range. Such wide color gamut can be represented using floating point HDR pixel values but those are inefficient to encode. They also lack perceptual uniformity of the luminance and color distribution, which is provided (in approximation) by most LDR color spaces. Therefore, there is a need to devise an efficient, perceptually uniform and integer valued representation for high dynamic range pixel values. In this paper we evaluate several methods for encoding colour HDR pixel values, in particular for use in image and video compression. Unlike other studies we test both luminance and color difference encoding in a rigorous 4AFC threshold experiments to determine the minimum bit-depth required. Results show that the Perceptual Quantizer (PQ) encoding provides the best perceptual uniformity in the considered luminance range, however the gain in bit-depth is rather modest. More significant difference can be observed between color difference encoding schemes, from which YDuDv encoding seems to be the most efficient.

Silicon isotope separation utilizing infrared multiphoton dissociation of Si{sub 2}F{sub 6} irradiated with two-color CO{sub 2} laser light

Energy Technology Data Exchange (ETDEWEB)

Yokoyama, Atsushi; Ohba, Hironori; Hashimoto, Masashi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Ishii, Takeshi; Ohya, Akio [Nuclear Development Corp., Tokai, Ibaraki (Japan); Arai, Shigeyoshi [Hill Research Co. Ltd., Tokyo (Japan)

2002-08-01

Silicon isotope separation has been done by utilizing the Infrared Multiphoton Dissociation (IRMPD) of Si{sub 2}F{sub 6} irradiated with two-color CO{sub 2} laser lights. The two-color excitation method improved the separation efficiency keeping the high enrichment factors. For example, 99.74% of {sup 28}Si was obtained at 49.63% dissociation of Si{sub 2}F{sub 6} after the simultaneous irradiation of 200 pulses with 966.23 cm{sup -1} photons (0.084 J/cm{sup 2}) and 954.55 cm{sup -1} photons (0.658 J/cm{sup 2}), while 2000 pulses were needed to obtain 99.35% of {sup 28}Si at 35.6% dissociation in the case of only one-color irradiation at 954.55 cm{sup -1} (0.97 J/cm{sup 2}). (author)

Factors affecting color strength of printing on film-coated tablets by UV laser irradiation: TiO2 particle size, crystal structure, or concentration in the film, and the irradiated UV laser power.

Science.gov (United States)

Hosokawa, Akihiro; Kato, Yoshiteru

2011-08-01

The purpose of this article is to study factors affecting color strength of printing on film-coated tablets by ultraviolet (UV) laser irradiation: particle size, crystal structure, or concentration of titanium dioxide (TiO2) in film, and irradiated UV laser power. Hydroxypropylmethylcellulose films containing 4.0% of TiO2, of which BET particle sizes were ranging from 126.1 to 219.8 nm, were irradiated 3.14W of UV laser at a wavelength 355 nm to study effects of TiO2 particle size and crystal structure on the printing. The films containing TiO2 concentration ranging from 1.0 to 7.7% were irradiated 3.14 or 5.39W of the UV laser to study effect of TiO2 concentration on the printing. The film containing 4.0% of TiO2, was irradiated the UV laser up to 6.42W to study effect of the UV laser power on the printing. The color strength of the printed films was estimated by a spectrophotometer as total color difference (dE). Particle size, crystal structure, and concentration of TiO2 in the films did not affect the printing. In the relationship between the irradiated UV laser power and dE, there found an inflection point (1.6W). When the UV laser power was below 1.6W, the films were not printed. When it was beyond the point, total color difference increased linearly in proportion with the irradiated laser power. The color strength of the printing on film was not changed by TiO2 particle size, crystal structure, and concentration, but could be controlled by regulating the irradiated UV laser power beyond the inflection point.

Rational choices for the wavelengths of a two color interferometer

International Nuclear Information System (INIS)

Jobes, F.C.

1995-07-01

If in a two color interferometer for plasma density measurements, the two wavelengths are chosen to have a ratio that is a rational number, and if the signals from each of the wavelengths are multiplied in frequency by the appropriate integer of the rational number and then heterodyned together, the resultant signal will have all effects of component motion nulled out. A phase measurement of this signal will have only plasma density information in it. With CO 2 lasers, it is possible to find suitable wavelength pairs which are close enough to rational numbers to produce an improvement of about 100 in density resolution, compared to standard two color interferometers

Polarimetric, Two-Color, Photon-Counting Laser Altimeter Measurements of Forest Canopy Structure

Science.gov (United States)

Harding, David J.; Dabney, Philip W.; Valett, Susan

2011-01-01

Laser altimeter measurements of forest stands with distinct structures and compositions have been acquired at 532 nm (green) and 1064 nm (near-infrared) wavelengths and parallel and perpendicular polarization states using the Slope Imaging Multi-polarization Photon Counting Lidar (SIMPL). The micropulse, single photon ranging measurement approach employed by SIMPL provides canopy structure measurements with high vertical and spatial resolution. Using a height distribution analysis method adapted from conventional, 1064 nm, full-waveform lidar remote sensing, the sensitivity of two parameters commonly used for above-ground biomass estimation are compared as a function of wavelength. The results for the height of median energy (HOME) and canopy cover are for the most part very similar, indicating biomass estimations using lidars operating at green and near-infrared wavelengths will yield comparable estimates. The expected detection of increasing depolarization with depth into the canopies due to volume multiple-scattering was not observed, possibly due to the small laser footprint and the small detector field of view used in the SIMPL instrument. The results of this work provide pathfinder information for NASA's ICESat-2 mission that will employ a 532 nm, micropulse, photon counting laser altimeter.

Design study for a two-color beta measurement system

Science.gov (United States)

1982-01-01

Design analysis of the beam splitter combined two color beta system is presented. Conventional and dichroic beam splitters are discussed. Design analysis of the beta system employing two beams with focusing at separate points is presented. Alterations and basic parameters of the two beam system are discussed. Alterations in the focus of the initial laser and the returning beams are also discussed. Heterodyne efficiencies for the on axis and off axis reflected radiation are included.

Long-range predissociation in two-color photoassociation of ultracold Na atoms

NARCIS (Netherlands)

Molenaar, P.A.; Straten, P. van der; Heideman, H.G.M.

1997-01-01

We report two-color photo-associative ionization of sodium in a Magneto-Optical Trap. The experimental results yield information on both singly and doubly excited states. We find that the highest bound vibrational levels (v > 20) of the singly-excited 0^- g state predissociate into the 3²P3/2

Colorizing metals with femtosecond laser pulses

International Nuclear Information System (INIS)

Vorobyev, A. Y.; Guo Chunlei

2008-01-01

For centuries, it had been the dream of alchemists to turn inexpensive metals into gold. Certainly, it is not enough from an alchemist's point of view to transfer only the appearance of a metal to gold. However, the possibility of rendering a certain metal to a completely different color without coating can be very interesting in its own right. In this work, we demonstrate a femtosecond laser processing technique that allows us to create a variety of colors on a metal that ultimately leads us to control its optical properties from UV to terahertz

Eye safe laser range finders

International Nuclear Information System (INIS)

Snir, M.; Margaliot, M.; Amitzi, A.

2004-01-01

During the 1970's, Ruby (Q switched) laser based range finders with a wavelength of 694nm were first used. These lasers operated in a pulse mode within the visible light range and produced a risk for the eye retina. The laser beam striking the macula could damage the eye and might cause blindness. Over the years, Nd:YAG (Q switched) lasers were developed (operating at 1064nm) for range finding and designation uses. The wavelength of these lasers, operating in the near Infra-Red range (invisible), is also focused tightly on the retina. The human eye does not respond to the invisible light so there is no natural protection (eye blink reflex) as in the visible light. The operation of these lasers worldwide, especially when the laser beam is exposed, causes occasional eye accidents. Another risk is stemming from the use of observation systems with a high optical gain, in the laser operation areas, which enlarge the range of risk quite significantly. Therefore, research and development efforts were invested in order to introduce eye safe lasers. One of the solutions for this problem is presented in following document

Tunneling ionization and harmonic generation in two-color fields

International Nuclear Information System (INIS)

Kondo, K.; Kobayashi, Y.; Sagisaka, A.; Nabekawa, Y.; Watanabe, S.

1996-01-01

Tunneling ionization and harmonic generation in two-color fields were studied with a fundamental beam (ω) and its harmonics (2ω,3ω), which were generated by a 100-fs Ti:sapphire laser. Ion yields of atoms and molecules were successfully controlled by means of a change in the relative phase between ω and 3ω pulses. Two-color interference was clearly observed in photoelectron spectra and harmonic spectra. In the ω endash 2ω field even-order harmonics were observed in which the intensity was almost equal to that of the odd harmonics because of an asymmetric optical field. These results were compared with the quasi-static model for ionization and with the quantum theory for harmonic generation. copyright 1996 Optical Society of America

Memory effects, two color percolation, and the temperature dependence of Mott variable-range hopping

Science.gov (United States)

Agam, Oded; Aleiner, Igor L.

2014-06-01

There are three basic processes that determine hopping transport: (a) hopping between normally empty sites (i.e., having exponentially small occupation numbers at equilibrium), (b) hopping between normally occupied sites, and (c) transitions between normally occupied and unoccupied sites. In conventional theories all these processes are considered Markovian and the correlations of occupation numbers of different sites are believed to be small (i.e., not exponential in temperature). We show that, contrary to this belief, memory effects suppress the processes of type (c) and manifest themselves in a subleading exponential temperature dependence of the variable-range hopping conductivity. This temperature dependence originates from the property that sites of type (a) and (b) form two independent resistor networks that are weakly coupled to each other by processes of type (c). This leads to a two-color percolation problem which we solve in the critical region.

A new approach to dual-color two-photon microscopy with fluorescent proteins

Directory of Open Access Journals (Sweden)

Rebane Aleks

2010-02-01

Full Text Available Abstract Background Two-photon dual-color imaging of tissues and cells labeled with fluorescent proteins (FPs is challenging because most two-photon microscopes only provide one laser excitation wavelength at a time. At present, methods for two-photon dual-color imaging are limited due to the requirement of large differences in Stokes shifts between the FPs used and their low two-photon absorption (2PA efficiency. Results Here we present a new method of dual-color two-photon microscopy that uses the simultaneous excitation of the lowest-energy electronic transition of a blue fluorescent protein and a higher-energy electronic transition of a red fluorescent protein. Conclusion Our method does not require large differences in Stokes shifts and can be extended to a variety of FP pairs with larger 2PA efficiency and more optimal imaging properties.

New methods of generation of ultrashort laser pulses for ranging

Science.gov (United States)

Jelinkova, Helena; Hamal, Karel; Kubecek, V.; Prochazka, Ivan

1993-01-01

To reach the millimeter satellite laser ranging accuracy, the goal for nineties, new laser ranging techniques have to be applied. To increase the laser ranging precision, the application of the ultrashort laser pulses in connection with the new signal detection and processing techniques, is inevitable. The two wavelength laser ranging is one of the ways to measure the atmospheric dispersion to improve the existing atmospheric correction models and hence, to increase the overall system ranging accuracy to the desired value. We are presenting a review of several nonstandard techniques of ultrashort laser pulses generation, which may be utilized for laser ranging: compression of the nanosecond pulses using stimulated Brillouin and Raman backscattering; compression of the mode-locked pulses using Raman backscattering; passive mode-locking technique with nonlinear mirror; and passive mode-locking technique with the negative feedback.

Femtosecond laser ablation of polymethylmethacrylate via dual-color synthesized waveform

International Nuclear Information System (INIS)

Yang, Chan-Shan; Zaytsev, Alexey; Lin, Chih-Hsuan; Teng, Kuei-Chung; Her, Tsing-Hua; Pan, Ci-Ling

2015-01-01

We have demonstrated the laser ablation of PMMA using dual-color waveform synthesis of the fundamental (ω) and its second-harmonic (2ω) of a femtosecond Ti:Sapphire laser. A modest and yet clear modulation (∼22%) in ablated area versus relative phase between the 2ω and ω beams with a power-ratio of 15% (28/183 mW) is revealed. This is explained qualitatively by the dependence of ablation on multiphoton ionization of which the rate is related to the relative phase of the synthesized waveform. At higher peak power ratios, the modulation decreases rapidly, as the two-photon-ionization rate of the 2ω dominates over that of the three- to four- photon ionization of the ω beam. This technique demonstrates the feasibility of phase-controlled laser processing of materials

Generation of Bright, Spatially Coherent Soft X-Ray High Harmonics in a Hollow Waveguide Using Two-Color Synthesized Laser Pulses.

Science.gov (United States)

Jin, Cheng; Stein, Gregory J; Hong, Kyung-Han; Lin, C D

2015-07-24

We investigate the efficient generation of low-divergence high-order harmonics driven by waveform-optimized laser pulses in a gas-filled hollow waveguide. The drive waveform is obtained by synthesizing two-color laser pulses, optimized such that highest harmonic yields are emitted from each atom. Optimization of the gas pressure and waveguide configuration has enabled us to produce bright and spatially coherent harmonics extending from the extreme ultraviolet to soft x rays. Our study on the interplay among waveguide mode, atomic dispersion, and plasma effect uncovers how dynamic phase matching is accomplished and how an optimized waveform is maintained when optimal waveguide parameters (radius and length) and gas pressure are identified. Our analysis should help laboratory development in the generation of high-flux bright coherent soft x rays as tabletop light sources for applications.

Simple approach to three-color two-photon microscopy by a fiber-optic wavelength convertor.

Science.gov (United States)

Li, Kuen-Che; Huang, Lynn L H; Liang, Jhih-Hao; Chan, Ming-Che

2016-11-01

A simple approach to multi-color two-photon microscopy of the red, green, and blue fluorescent indicators was reported based on an ultra-compact 1.03-μm femtosecond laser and a nonlinear fiber. Inside the nonlinear fiber, the 1.03-μm laser pulses were simultaneously blue-shifted to 0.6~0.8 μm and red-shifted to 1.2~1.4 μm region by the Cherenkov radiation and fiber Raman gain effects. The wavelength-shifted 0.6~0.8 μm and 1.2~1.4 μm radiations were co-propagated with the residual non-converted 1.03-μm pulses inside the same nonlinear fiber to form a fiber-output three-color femtosecond source. The application of the multi-wavelength sources on multi-color two-photon fluorescence microscopy were also demonstrated. Overall, due to simple system configuration, convenient wavelength conversion, easy wavelength tunability within the entire 0.7~1.35 μm bio-penetration window and less requirement for high power and bulky light sources, the simple approach to multi-color two-photon microscopy could be widely applicable as an easily implemented and excellent research tool for future biomedical and possibly even clinical applications.

Atmospheric Error Correction of the Laser Beam Ranging

Directory of Open Access Journals (Sweden)

J. Saydi

2014-01-01

Full Text Available Atmospheric models based on surface measurements of pressure, temperature, and relative humidity have been used to increase the laser ranging accuracy by ray tracing. Atmospheric refraction can cause significant errors in laser ranging systems. Through the present research, the atmospheric effects on the laser beam were investigated by using the principles of laser ranging. Atmospheric correction was calculated for 0.532, 1.3, and 10.6 micron wavelengths through the weather conditions of Tehran, Isfahan, and Bushehr in Iran since March 2012 to March 2013. Through the present research the atmospheric correction was computed for meteorological data in base of monthly mean. Of course, the meteorological data were received from meteorological stations in Tehran, Isfahan, and Bushehr. Atmospheric correction was calculated for 11, 100, and 200 kilometers laser beam propagations under 30°, 60°, and 90° rising angles for each propagation. The results of the study showed that in the same months and beam emission angles, the atmospheric correction was most accurate for 10.6 micron wavelength. The laser ranging error was decreased by increasing the laser emission angle. The atmospheric correction with two Marini-Murray and Mendes-Pavlis models for 0.532 nm was compared.

Research on range-gated laser active imaging seeker

Science.gov (United States)

You, Mu; Wang, PengHui; Tan, DongJie

2013-09-01

Compared with other imaging methods such as millimeter wave imaging, infrared imaging and visible light imaging, laser imaging provides both a 2-D array of reflected intensity data as well as 2-D array of range data, which is the most important data for use in autonomous target acquisition .In terms of application, it can be widely used in military fields such as radar, guidance and fuse. In this paper, we present a laser active imaging seeker system based on range-gated laser transmitter and sensor technology .The seeker system presented here consist of two important part, one is laser image system, which uses a negative lens to diverge the light from a pulse laser to flood illuminate a target, return light is collected by a camera lens, each laser pulse triggers the camera delay and shutter. The other is stabilization gimbals, which is designed to be a rotatable structure both in azimuth and elevation angles. The laser image system consists of transmitter and receiver. The transmitter is based on diode pumped solid-state lasers that are passively Q-switched at 532nm wavelength. A visible wavelength was chosen because the receiver uses a Gen III image intensifier tube with a spectral sensitivity limited to wavelengths less than 900nm.The receiver is image intensifier tube's micro channel plate coupled into high sensitivity charge coupled device camera. The image has been taken at range over one kilometer and can be taken at much longer range in better weather. Image frame frequency can be changed according to requirement of guidance with modifiable range gate, The instantaneous field of views of the system was found to be 2×2 deg. Since completion of system integration, the seeker system has gone through a series of tests both in the lab and in the outdoor field. Two different kinds of buildings have been chosen as target, which is located at range from 200m up to 1000m.To simulate dynamic process of range change between missile and target, the seeker system has

A comparative study of the effect of low laser radiation on mast cells in inflammatory fibrous hyperplasia colored and not colored by the toluidine blue

International Nuclear Information System (INIS)

Sawazaki, Iris

2001-01-01

THIS STUDY SHOWS A COMPARATIVE ANALYSIS OF THE EFFECTS OF THE LASER RADIATION IN LOW INTENSITY ON THE MAST CELL DEGRANULATION IN INFLAMMATORY FIBROUS HYPERPLASIA WHEN THEY ARE COLORED OR NOT BY THE TOLUIDINE BLUE. THE DYE WAS USED IN ORDER TO INCREASE THE ABSORPTION OF THE LASER LIGHT BY THE TISSUE. THE INJURE WAS DIVIDED IN THREE EQUAL PARTS, AND EACH PART RECEIVED A DIFFERENT KIND OF TREATMENT. ONE OF THEM WAS REMOVED TO BE THE CONTROL, THE SECOND PART WAS LASER TREATED AND THEN IMMEDIATELY REMOVED AND THE LAST ONE, AFTER BEING SUPERFICIALLY COLORED, WAS LASER TREATED AND THEN IMMEDIATELY REMOVED . THE ORDER OF THE STAGES WAS RANDOMLY CHANGED , THEN THE TIME BETWEEN THE STAGES WOULD NOT INTERFERE IN THE STATISTICAL ANALYSIS OF THE MAST CELL DEGRANULATION RATES. IT WAS FOUND THAT THE MAST CELL DEGRANULATION RATES WERE 49% FOR THE CONTROL GROUP, 87% FOR THE LASER GROUP AND 88% FOR THE COLORED/LASER GROUP. THERE WAS NO SIGNIFICANT STATISTICAL DIFFERENCES BETWEEN THE GROUP LASER TREATED AND THE ONE COLORED/LASER TREATED. HOWEVER, THERE WAS A SIGNIFICANT DIFFERENCE BETWEEN THE CONTROL AND THE TREATED GROUP (PS ≤ 0,01). (AUTHOR)

Phase-matching properties of yellow color HgGa2S4 for SHG and SFG in the 0.944-10.5910  μm range.

Science.gov (United States)

Kato, Kiyoshi; Petrov, Valentin; Umemura, Nobuhiro

2016-04-20

We report new experimental results on the phase-matching properties of yellow color HgGa2S4 crystals for harmonic generation of an Nd:YAG laser-pumped KTiOPO4 (KTP) optical parametric oscillator (OPO) and CO2 lasers in the 0.944-10.5910 μm range. In addition, we present new Sellmeier equations that provide a good reproduction of the present experimental results as well as the published data points for second-harmonic generation of CO2 laser radiation at 9.2197-9.6392 μm and Nd:YAG laser-pumped OPOs at 1.205-1.725 μm and 2.77-9.10 μm that were achieved with the orange and yellow color crystals.

The watercolor effect: quantitative evidence for luminance-dependent mechanisms of long-range color assimilation.

Science.gov (United States)

Devinck, Frédéric; Delahunt, Peter B; Hardy, Joseph L; Spillmann, Lothar; Werner, John S

2005-05-01

When a dark chromatic contour delineating a figure is flanked on the inside by a brighter chromatic contour, the brighter color will spread into the entire enclosed area. This is known as the watercolor effect (WCE). Here we quantified the effect of color spreading using both color-matching and hue-cancellation tasks. Over a wide range of stimulus chromaticities, there was a reliable shift in color appearance that closely followed the direction of the inducing contour. When the contours were equated in luminance, the WCE was still present, but weak. The magnitude of the color spreading increased with increases in luminance contrast between the two contours. Additionally, as the luminance contrast between the contours increased, the chromaticity of the induced color more closely resembled that of the inside contour. The results support the hypothesis that the WCE is mediated by luminance-dependent mechanisms of long-range color assimilation.

Comparison of two Q-switched lasers and a short-pulse erbium-doped yttrium aluminum garnet laser for treatment of cosmetic tattoos containing titanium and iron in an animal model.

Science.gov (United States)

Wang, Chia-Chen; Huang, Chuen-Lin; Yang, An-Hang; Chen, Chih-Kang; Lee, Shao-Chen; Leu, Fur-Jiang

2010-11-01

Cosmetic tattoos contain titanium and ferric oxide and darken through reduction after Q-switched laser irradiation. The optimal treatment for removing these pigments remains unknown. To compare the effects of two Q-switched lasers and a short-pulse erbium-doped yttrium aluminum garnet (SP Er:YAG) laser to remove cosmetic tattoos in an animal model. Rats were tattooed using white, flesh-colored, and brown inks (4 bands of each color) on their backs. For each color, one band was left untreated, and one each was treated with a Q-switched neodymium-doped YAG laser, a Q-switched alexandrite laser, and a SP Er:YAG laser every 3 weeks until the pigments were clear. The two Q-switched lasers were equally effective; all three pigments darkened initially and then resolved gradually. Up to 20, 18, and 10 sessions were required to remove white, flesh-colored, and brown tattoos, respectively. Only six sessions were required with the SP Er:YAG laser. Minimal scarring was observed with all lasers. Skin biopsies confirmed pigment granule fragmentation after Q-switched laser treatment and a decrease in the amount of pigment after SP Er:YAG laser treatment. The SP Er:YAG laser was superior to the Q-switched lasers for removing cosmetic tattoos. © 2010 by the American Society for Dermatologic Surgery, Inc.

An overview of the laser ranging method of space laser altimeter

Science.gov (United States)

Zhou, Hui; Chen, Yuwei; Hyyppä, Juha; Li, Song

2017-11-01

Space laser altimeter is an active remote sensing instrument to measure topographic map of Earth, Moon and planetary. The space laser altimeter determines the range between the instrument and laser footprint by measuring round trip time of laser pulse. The return pulse reflected from ground surface is gathered by the receiver of space laser altimeter, the pulsewidth and amplitude of which are changeable with the variability of the ground relief. Meantime, several kinds of noise overlapped on the return pulse signal affect its signal-to-noise ratio. To eliminate the influence of these factors that cause range walk and range uncertainty, the reliable laser ranging methods need to be implemented to obtain high-precision range results. Based on typical space laser altimeters in the past few decades, various ranging methods are expounded in detail according to the operational principle of instruments and timing method. By illustrating the concrete procedure of determining time of flight of laser pulse, this overview provides the comparison of the employed technologies in previous and undergoing research programs and prospect innovative technology for space laser altimeters in future.

Observations of strain accumulation across the san andreas fault near palmdale, california, with a two-color geodimeter.

Science.gov (United States)

Langbein, J O; Linker, M F; McGarr, A; Slater, L E

1982-12-17

Two-color laser ranging measurements during a 15-month period over a geodetic network spanning the San Andreas fault near Palmdale, California, indicate that the crust expands and contracts aseismically in episodes as short as 2 weeks. Shear strain parallel to the fault has accumulated monotonically since November 1980, but at a variable rate. Improvements in measurement precision and temporal resolution over those of previous geodetic studies near Palmdale have resulted in the definition of a time history of crustal deformation that is much more complex than formerly realized.

Analysis of oxide formation induced by UV laser coloration of stainless steel

Energy Technology Data Exchange (ETDEWEB)

Li, Z.L., E-mail: zlli@SIMTech.a-star.edu.sg [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Zheng, H.Y.; Teh, K.M.; Liu, Y.C.; Lim, G.C. [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Seng, H.L.; Yakovlev, N.L. [Institute of Materials Research and Engineering, 3 Research Link, 117602 (Singapore)

2009-12-15

Laser-induced coloration on metal surfaces has important applications in product identification, enhancing styles and aesthetics. The color generation is the result of controlled surface oxidation during laser beam interaction with the metal surfaces. In this study, we aim to obtain in-depth understanding of the oxide formation process when an UV laser beam interacts with stainless steel in air. The oxide layer is analysed by means of optical microscopy, scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometer (TOF-SIMS). TOF-SIMS results clearly show the formation of duplex oxide structures. The duplex structure includes an inner layer of Cr oxide solution and an outer layer of Fe oxide solution. The oxide layer thickness increased as the results of Fe diffusion to surface during multiple laser scanning passes.

Analysis of oxide formation induced by UV laser coloration of stainless steel

International Nuclear Information System (INIS)

Li, Z.L.; Zheng, H.Y.; Teh, K.M.; Liu, Y.C.; Lim, G.C.; Seng, H.L.; Yakovlev, N.L.

2009-01-01

Laser-induced coloration on metal surfaces has important applications in product identification, enhancing styles and aesthetics. The color generation is the result of controlled surface oxidation during laser beam interaction with the metal surfaces. In this study, we aim to obtain in-depth understanding of the oxide formation process when an UV laser beam interacts with stainless steel in air. The oxide layer is analysed by means of optical microscopy, scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometer (TOF-SIMS). TOF-SIMS results clearly show the formation of duplex oxide structures. The duplex structure includes an inner layer of Cr oxide solution and an outer layer of Fe oxide solution. The oxide layer thickness increased as the results of Fe diffusion to surface during multiple laser scanning passes.

The design of two color interferometer system for the 3-dimensional analysis of plasma density evolution on KSTAR

Energy Technology Data Exchange (ETDEWEB)

Lee, K.C., E-mail: kclee@nfri.re.kr [National Fusion Research Institute, Daejeon 34133 (Korea, Republic of); Juhn, J.-W.; Nam, Y.U.; Kim, Y.S.; Wi, H.M. [National Fusion Research Institute, Daejeon 34133 (Korea, Republic of); Kim, S.W.; Ghim, Y.-C. [Korea Advanced Institute of Science and Technology, Daejeon 34141 (Korea, Republic of)

2016-12-15

Highlights: • A Two Color Interferometer (TCI) system is designed for 3-D measurement of KSTAR. • TCI is consists of 10.6 μm CO2 laser and 0.63 μm HeNe laser with tangential 5 channels. • 2 channels are installed in 2016 and 5 channel operation is planned in 2017. - Abstract: A 5-channel two color interferometer (TCI) system has been designed on KSTAR. TCI system is designed for tangential beam paths, which will combine with two existing interferometer systems of vertical and radial beam paths, so that it will provide 3-dimensional measurement of electron density evolution. TCI system uses wavelengths of 10.6 μm by a CO{sub 2} laser and 0.633 μm by a HeNe laser. The system compensates the vibrational noise by using two colors and avoids refraction by short wavelengths. The main purpose of the TCI is to generate routine measurement of the line integrated plasma density for the real time density control on KSTAR. The 5-channels will provide profile data for the density. Time resolution of the system is expected to be 500 kHz or higher in order to measure 3-dimensional density fluctuations for ELMs and other MHD activities including TAE modes. The system is planned to be working on KSTAR 2016 campaign with 1–2 channels.

The design of two color interferometer system for the 3-dimensional analysis of plasma density evolution on KSTAR

International Nuclear Information System (INIS)

Lee, K.C.; Juhn, J.-W.; Nam, Y.U.; Kim, Y.S.; Wi, H.M.; Kim, S.W.; Ghim, Y.-C.

2016-01-01

Highlights: • A Two Color Interferometer (TCI) system is designed for 3-D measurement of KSTAR. • TCI is consists of 10.6 μm CO2 laser and 0.63 μm HeNe laser with tangential 5 channels. • 2 channels are installed in 2016 and 5 channel operation is planned in 2017. - Abstract: A 5-channel two color interferometer (TCI) system has been designed on KSTAR. TCI system is designed for tangential beam paths, which will combine with two existing interferometer systems of vertical and radial beam paths, so that it will provide 3-dimensional measurement of electron density evolution. TCI system uses wavelengths of 10.6 μm by a CO 2 laser and 0.633 μm by a HeNe laser. The system compensates the vibrational noise by using two colors and avoids refraction by short wavelengths. The main purpose of the TCI is to generate routine measurement of the line integrated plasma density for the real time density control on KSTAR. The 5-channels will provide profile data for the density. Time resolution of the system is expected to be 500 kHz or higher in order to measure 3-dimensional density fluctuations for ELMs and other MHD activities including TAE modes. The system is planned to be working on KSTAR 2016 campaign with 1–2 channels.

Simultaneous two-phase flow measurement of spray mixing process by means of high-speed two-color PIV

International Nuclear Information System (INIS)

Zhang, Ming; Xu, Min; Hung, David L S

2014-01-01

In this article, a novel high-speed two-color PIV optical diagnostic technique has been developed and applied to simultaneously measure the velocity flow-fields of a multi-hole spark-ignition direct injection (SIDI) fuel injector spray and its ambient gas in a high-pressure constant volume chamber. To allow for the phase discrimination between the fuel droplets and ambient gas, a special tracer-filter system was designed. Fluorescent seeding particles with Sauter mean diameter (SMD) of 4.8 µm were used to trace the gas inside the chamber. With a single high-speed Nd:YLF laser sheet (527 nm) as the incident light source, the Mie-scattering signal marked the phase of the fuel spray, while the fluorescent signal generated from the seeding particles tracked the phase of ambient gas. A high-speed camera, with an image-doubler (mounted in front of the camera lens) that divided the camera pixels into two parts focusing on the same field of view, was used to collect the Mie-scattering signal and LIF (laser induced fluorescence) signal simultaneously with two carefully selected optical filters. To accommodate the large dynamic range of velocities in the two phases (1–2 orders of magnitude difference), two separation times (dt) were introduced. This technique was successfully applied to the liquid spray and ambient gas two-phase flow measurement. The measurement accuracy was compared with those from LDV (laser Doppler velocimetry) measurement and good agreement was obtained. Ambient gas motion surrounding the fuel spray was investigated and characterized into three zones. The momentum transfer process between the fuel spray and ambient gas in each zone was analyzed. The two-phase flow interaction under various superheated conditions was investigated. A strengthened momentum transfer from the liquid spray to the ambient was observed with increased superheat degree. (paper)

Short-Range Sensor for Underwater Robot Navigation using Line-lasers and Vision

DEFF Research Database (Denmark)

Hansen, Peter Nicholas; Nielsen, Mikkel Cornelius; Christensen, David Johan

2015-01-01

This paper investigates a minimalistic laser-based range sensor, used for underwater inspection by Autonomous Underwater Vehicles (AUV). This range detection system system comprise two lasers projecting vertical lines, parallel to a camera’s viewing axis, into the environment. Using both lasers...

Gold nanoshell photomodification under a single-nanosecond laser pulse accompanied by color-shifting and bubble formation phenomena

International Nuclear Information System (INIS)

Akchurin, Garif; Khlebtsov, Boris; Akchurin, Georgy; Tuchin, Valery; Zharov, Vladimir; Khlebtsov, Nikolai

2008-01-01

Laser-nanoparticle interaction is crucial for biomedical applications of lasers and nanotechnology to the treatment of cancer or pathogenic microorganisms. We report on the first observation of laser-induced coloring of gold nanoshell solution after a one nanosecond pulse and an unprecedentedly low bubble formation (as the main mechanism of cancer cell killing) threshold at a laser fluence of about 4 mJ cm -2 , which is safe for normal tissue. Specifically, silica/gold nanoshell (140/15 nm) suspensions were irradiated with a single 4 ns (1064 nm) or 8 ns (900 nm) laser pulse at fluences ranging from 0.1 mJ cm -2 to 50 J cm -2 . Solution red coloring was observed by the naked eye confirmed by blue-shifting of the absorption spectrum maximum from the initial 900 nm for nanoshells to 530 nm for conventional colloidal gold nanospheres. TEM images revealed significant photomodification of nanoparticles including complete fragmentation of gold shells, changes in silica core structure, formation of small 20-30 nm isolated spherical gold nanoparticles, gold nanoshells with central holes, and large and small spherical gold particles attached to a silica core. The time-resolved monitoring of bubble formation phenomena with the photothermal (PT) thermolens technique demonstrated that after application of a single 8 ns pulse at fluences 5-10 mJ cm -2 and higher the next pulse did not produce any PT response, indicating a dramatic decrease in absorption because of gold shell modification. We also observed a dependence of the bubble expansion time on the laser energy with unusually very fast PT signal rising (∼3.5 ns scale at 0.2 J cm -2 ). Application of the observed phenomena to medical applications is discussed, including a simple visual color test for laser-nanoparticle interaction

Long-Range Predissociation in Two-Color Photoassociation of Ultracold Na Atoms

International Nuclear Information System (INIS)

Molenaar, P.A.; van der Straten, P.; Heideman, H.G.

1996-01-01

We report two-color photoassociative ionization of sodium in a magneto-optical trap. The experimental results yield information on both singly and doubly excited states. We find that the highest bound vibrational levels (v approx-gt 20) of the singly excited 0 g - state predissociate into the 3 2 P 3/2 +3 2 S 1/2 (F g =1) dissociation continuum due to avoided crossings of the hyperfine components of this potential with other molecular symmetries. Based on symmetry and energy consideration we argue that a doubly excited 1 u state remains autoionizing even when only a few GHz above the dissociation continuum. copyright 1996 The American Physical Society

Laser Ranging in Solar System: Technology Developments and New Science Measurement Capabilities

Science.gov (United States)

Sun, X.; Smith, D. E.; Zuber, M. T.; Mcgarry, J.; Neumann, G. A.; Mazarico, E.

2015-12-01

Laser Ranging has played a major role in geodetic studies of the Earth over the past 40 years. The technique can potentially be used in between planets and spacecrafts within the solar system to advance planetary science. For example, a direct measurement of distances between planets, such as Mars and Venus would make significant improvements in understanding the dynamics of the whole solar system, including the masses of the planets and moons, asteroids and their perturbing interactions, and the gravity field of the Sun. Compared to the conventional radio frequency (RF) tracking systems, laser ranging is potentially more accurate because it is much less sensitive to the transmission media. It is also more efficient because the laser beams are much better focused onto the targets than RF beams. However, existing laser ranging systems are all Earth centric, that is, from ground stations on Earth to orbiting satellites in near Earth orbits or lunar orbit, and to the lunar retro-reflector arrays deployed by the astronauts in the early days of lunar explorations. Several long distance laser ranging experiments have been conducted with the lidar in space, including a two-way laser ranging demonstration between Earth and the Mercury Laser Altimeter (MLA) on the MESSENGER spacecraft over 24 million km, and a one way laser transmission and detection experiment over 80 million km between Earth and the Mars Orbiting Laser Altimeter (MOLA) on the MGS spacecraft in Mars orbit. A one-way laser ranging operation has been carried out continuously from 2009 to 2014 between multiple ground stations to LRO spacecraft in lunar orbit. The Lunar Laser Communication Demonstration (LLCD) on the LADEE mission has demonstrated that a two way laser ranging measurements, including both the Doppler frequency and the phase shift, can be obtained from the subcarrier or the data clocks of a high speed duplex laser communication system. Plans and concepts presently being studied suggest we may be

Investigation of dynamic of unconsolidated materials using two-color digital holography

Directory of Open Access Journals (Sweden)

Boileau J.-P.

2010-06-01

Full Text Available The paper presents a two-color digital holographic interferometer. The set-up is devoted to the study of the fundamental dynamic of unconsolidated materials. Optical configuration and algorithms to recover the optical phase of two-color digitally encoded holograms are described. The method is based on a spatial-color-multiplexing scheme in which holographic reconstruction is performed using adapted wavelength zero-padding and reconstructing distance. Experimental results are presented in the case of granular media excited in the frequency range 400Hz-3000Hz and exhibits the 3D movement.

Precise Range Determination Using Laser Ranging Data of LAGEOS

Directory of Open Access Journals (Sweden)

Kwang-Ryul Kim

1993-12-01

Full Text Available Satellite laser ranging observation of LAGEOS ¥± has been performed using the SLR System at Sheshan Laser Ranging Station, Shanghai Observatory. And we obtained 1,838 observational points The observed range data is corrected by means of system delay correction using ground target observation, atmospheric refraction delay correction, offset correction, general relativistic correction and tide correction including solid tide, polar tide and ocean tide. As a result, the determined range delay mean value is 19.12m and the mean internal accuracy by means of polynomial fitting and least square method is ¡¾7cm. Corrected observational points are 1,340 and noise ratio to total observational points is 27.1%

IceBridge Riegl Laser Altimeter L1B Time-Tagged Laser Ranges

Data.gov (United States)

National Aeronautics and Space Administration — The NASA IceBridge Riegl Laser Altimeter L1B Time-Tagged Laser Ranges (ILUTP1B) data set contains laser ranges, returned pulses, and deviation for returned pulses in...

A contribution to laser range imaging technology

Science.gov (United States)

Defigueiredo, Rui J. P.; Denney, Bradley S.

1991-01-01

The goal of the project was to develop a methodology for fusion of a Laser Range Imaging Device (LRID) and camera data. Our initial work in the project led to the conclusion that none of the LRID's that were available were sufficiently adequate for this purpose. Thus we spent the time and effort on the development of the new LRID with several novel features which elicit the desired fusion objectives. In what follows, we describe the device developed and built under contract. The Laser Range Imaging Device (LRID) is an instrument which scans a scene using a laser and returns range and reflection intensity data. Such a system would be extremely useful in scene analysis in industry and space applications. The LRID will be eventually implemented on board a mobile robot. The current system has several advantages over some commercially available systems. One improvement is the use of X-Y galvonometer scanning mirrors instead of polygonal mirrors present in some systems. The advantage of the X-Y scanning mirrors is that the mirror system can be programmed to provide adjustable scanning regions. For each mirror there are two controls accessible by the computer. The first is the mirror position and the second is a zoom factor which modifies the amplitude of the position of the parameter. Another advantage of the LRID is the use of a visible low power laser. Some of the commercial systems use a higher intensity invisible laser which causes safety concerns. By using a low power visible laser, not only can one see the beam and avoid direct eye contact, but also the lower intensity reduces the risk of damage to the eye, and no protective eyeware is required.

The algorithm to generate color point-cloud with the registration between panoramic image and laser point-cloud

International Nuclear Information System (INIS)

Zeng, Fanyang; Zhong, Ruofei

2014-01-01

Laser point cloud contains only intensity information and it is necessary for visual interpretation to obtain color information from other sensor. Cameras can provide texture, color, and other information of the corresponding object. Points with color information of corresponding pixels in digital images can be used to generate color point-cloud and is conducive to the visualization, classification and modeling of point-cloud. Different types of digital cameras are used in different Mobile Measurement Systems (MMS).the principles and processes for generating color point-cloud in different systems are not the same. The most prominent feature of the panoramic images is the field of 360 degrees view angle in the horizontal direction, to obtain the image information around the camera as much as possible. In this paper, we introduce a method to generate color point-cloud with panoramic image and laser point-cloud, and deduce the equation of the correspondence between points in panoramic images and laser point-clouds. The fusion of panoramic image and laser point-cloud is according to the collinear principle of three points (the center of the omnidirectional multi-camera system, the image point on the sphere, the object point). The experimental results show that the proposed algorithm and formulae in this paper are correct

All Fiber-Coupled OH Planar Laser-Induced-Fluorescence (OH-PLIF)-Based Two-Dimensional Thermometry.

Science.gov (United States)

Hsu, Paul S; Jiang, Naibo; Patnaik, Anil K; Katta, Vish; Roy, Sukesh; Gord, James R

2018-04-01

Two-color, planar laser-induced fluorescence (PLIF)-based two-dimensional (2D) thermometry techniques for reacting flows, which are typically developed in the laboratory conditions, face a stiff challenge in their practical implementation in harsh environments such as combustion rigs. In addition to limited optical access, the critical experimental conditions (i.e., uncontrolled humidity, vibration, and large thermal gradients) often restrict sensitive laser system operation and cause difficulties maintaining beam-overlap. Thus, an all fiber-coupled, two-color OH-PLIF system has been developed, employing two long optical fibers allowing isolation of the laser and signal-collection systems. Two OH-excitation laser beams (∼283 nm and ∼286 nm) are delivered through a common 6 m long, 400 µm core, deep ultraviolet (UV)-enhanced multimode fiber. The fluorescence signal (∼310 nm) is collected by a 3 m long, UV-grade imaging fiber. Proof-of-principle temperature measurements are demonstrated in atmospheric pressure, near adiabatic, CH 4 /O 2 /N 2 jet flames. The effects of the excitation pulse interval on fiber transmission are investigated. The proof-of-principle measurements show significant promise for thermometry in harsh environments such as gas turbine engine tests.

Compressive laser ranging.

Science.gov (United States)

Babbitt, Wm Randall; Barber, Zeb W; Renner, Christoffer

2011-12-15

Compressive sampling has been previously proposed as a technique for sampling radar returns and determining sparse range profiles with a reduced number of measurements compared to conventional techniques. By employing modulation on both transmission and reception, compressive sensing in ranging is extended to the direct measurement of range profiles without intermediate measurement of the return waveform. This compressive ranging approach enables the use of pseudorandom binary transmit waveforms and return modulation, along with low-bandwidth optical detectors to yield high-resolution ranging information. A proof-of-concept experiment is presented. With currently available compact, off-the-shelf electronics and photonics, such as high data rate binary pattern generators and high-bandwidth digital optical modulators, compressive laser ranging can readily achieve subcentimeter resolution in a compact, lightweight package.

Laser Based Color Film Recorder System With GaAs Microlaser

Science.gov (United States)

Difrancesco, David J.

1989-07-01

In 1984 Pixar's research and development group built and applied to the motion-picture arts at Lucasfilm's ILM facility a three color laser based film scanner/recorder system. The digital film printer is capable of reading and writing 35mm film formats on a variety of film stocks. The system has been used in award-winning special-effects work, and has been operated in a normal production environment since that time. The primary objective was to develop a full color high resolution system, free from scan artifacts, enabling traditionally photographed motion-picture film to be inter-cut with digital raster image photography. Its use is applied to the art of blue-screen traveling-matte cinematography for motion pic-ture special effects. The system was designed using the Pixar Image Computer and conventional gas laser technology as the illumination source. This paper will discuss recent experimental work in the application of GaAs microlaser technology to a digital film printing system of the future.

Surface color perception under two illuminants: the second illuminant reduces color constancy

Science.gov (United States)

Yang, Joong Nam; Shevell, Steven K.

2003-01-01

This study investigates color perception in a scene with two different illuminants. The two illuminants, in opposite corners, simultaneously shine on a (simulated) scene with an opaque dividing wall, which controls how much of the scene is illuminated by each source. In the first experiment, the height of the dividing wall was varied. This changed the amount of each illuminant reaching objects on the opposite side of the wall. Results showed that the degree of color constancy decreased when a region on one side of the wall had cues to both illuminants, suggesting that cues from the second illuminant are detrimental to color constancy. In a later experiment, color constancy was found to improve when the specular highlight cues from the second illuminant were altered to be consistent with the first illuminant. This corroborates the influence of specular highlights in surface color perception, and suggests that the reduced color constancy in the first experiment is due to the inconsistent, though physically correct, cues from the two illuminants.

Poisson filtering of laser ranging data

Science.gov (United States)

Ricklefs, Randall L.; Shelus, Peter J.

1993-01-01

The filtering of data in a high noise, low signal strength environment is a situation encountered routinely in lunar laser ranging (LLR) and, to a lesser extent, in artificial satellite laser ranging (SLR). The use of Poisson statistics as one of the tools for filtering LLR data is described first in a historical context. The more recent application of this statistical technique to noisy SLR data is also described.

PROBABILISTIC MODEL OF LASER RANGE FINDER FOR THREE DIMENSIONAL GRID CELL IN CLOSE RANGE ENVIRONMENT

Directory of Open Access Journals (Sweden)

Hafiz b Iman

2016-04-01

Full Text Available The probabilistic model of a laser scanner presents an important aspect for simultaneous localization and map-building (SLAM. However, the characteristic of the beam of the laser range finder under extreme incident angles approaching 900 has not been thoroughly investigated. This research paper reports the characteristic of the density of the range value coming from a laser range finder under close range circumstances where the laser is imposed with a high incident angle. The laser was placed in a controlled environment consisting of walls at a close range and 1000 iteration of scans was collected. The assumption of normal density of the metrical data collapses when the beam traverses across sharp edges in this environment. The data collected also shows multimodal density at instances where the range has discontinuity. The standard deviation of the laser range finder is reported to average at 10.54 mm, with 0.96 of accuracy. This significance suggests that under extreme incident angles, a laser range finder reading behaves differently compared to normal distribution. The use of this information is crucial for SLAM activity in enclosed environments such as inside piping grid or other cluttered environments.KEYWORDS:   Hokuyo UTM-30LX; kernel density estimation; probabilistic model  

Current Trends and Challenges in Satellite Laser Ranging

Science.gov (United States)

Appleby, Graham M.; Bianco, Giuseppe; Noll, Carey E.; Pavlis, Erricos C.; Pearlman, Michael R.

2016-12-01

Satellite Laser Ranging (SLR) is used to measure accurately the distance from ground stations to retro-reflectors on satellites and on the Moon. SLR is one of the fundamental space-geodetic techniques that define the International Terrestrial Reference Frame (ITRF), which is the basis upon which many aspects of global change over space, time, and evolving technology are measured; with VLBI the two techniques define the scale of the ITRF; alone the SLR technique defines its origin (geocenter). The importance of the reference frame has recently been recognized at the inter-governmental level through the United Nations, which adopted in February 2015 the Resolution "Global Geodetic Reference Frame for Sustainable Development." Laser Ranging provides precision orbit determination and instrument calibration and validation for satellite-borne altimeters for the better understanding of sea level change, ocean dynamics, ice mass-balance, and terrestrial topography. It is also a tool to study the dynamics of the Moon and fundamental constants and theories. With the exception of the currently in-orbit GPS constellation, all GNSS satellites now carry retro-reflectors for improved orbit determination, harmonization of reference frames, and in-orbit co-location and system performance validation; the next generation of GPS satellites due for launch from 2019 onwards will also carry retro-reflectors. The ILRS delivers weekly realizations that are accumulated sequentially to extend the ITRF and the Earth Orientation Parameter series with a daily resolution. SLR technology continues to evolve towards the next-generation laser ranging systems and it is expected to successfully meet the challenges of the GGOS2020 program for a future Global Space Geodetic Network. Ranging precision is improving as higher repetition rate, narrower pulse lasers, and faster detectors are implemented within the network. Automation and pass interleaving at some stations is expanding temporal coverage and

Determination of self generated magnetic field and the plasma density using Cotton Mouton polarimetry with two color probes

Directory of Open Access Journals (Sweden)

Joshi A.S.

2013-11-01

Full Text Available Self generated magnetic fields (SGMF in laser produced plasmas are conventionally determined by measuring the Faraday rotation angle of a linearly polarized laser probe beam passing through the plasma along with the interferogram for obtaining plasma density. In this paper, we propose a new method to obtain the plasma density and the SGMF distribution from two simultaneous measurements of Cotton Mouton polarimetry of two linearly polarized probe beams of different colors that pass through plasma in a direction normal to the planar target. It is shown that this technique allows us to determine the distribution of SGMF and the plasma density without doing interferometry of laser produced plasmas.

The differing magnitude distributions of the two Jupiter Trojan color populations

Energy Technology Data Exchange (ETDEWEB)

Wong, Ian; Brown, Michael E. [Division of Geological and Planetary Sciences, California Institute of Technology Pasadena, CA 91125 (United States); Emery, Joshua P., E-mail: iwong@caltech.edu [Department of Earth and Planetary Sciences, University of Tennessee Knoxville, TN 37996 (United States)

2014-12-01

The Jupiter Trojans are a significant population of minor bodies in the middle solar system that have garnered substantial interest in recent years. Several spectroscopic studies of these objects have revealed notable bimodalities with respect to near-infrared spectra, infrared albedo, and color, which suggest the existence of two distinct groups among the Trojan population. In this paper, we analyze the magnitude distributions of these two groups, which we refer to as the red and less red color populations. By compiling spectral and photometric data from several previous works, we show that the observed bimodalities are self-consistent and categorize 221 of the 842 Trojans with absolute magnitudes in the range H<12.3 into the two color populations. We demonstrate that the magnitude distributions of the two color populations are distinct to a high confidence level (>95%) and fit them individually to a broken power law, with special attention given to evaluating and correcting for incompleteness in the Trojan catalog as well as incompleteness in our categorization of objects. A comparison of the best-fit curves shows that the faint-end power-law slopes are markedly different for the two color populations, which indicates that the red and less red Trojans likely formed in different locations. We propose a few hypotheses for the origin and evolution of the Trojan population based on the analyzed data.

10.23  Mcps laser pseudo-code ranging system with 0.33  mm (1σ) pseudo-range measurement precision.

Science.gov (United States)

Yu, Xiaonan; Tong, Shoufeng; Zhang, Lei; Dong, Yan; Zhao, Xin; Qiao, Yue

2017-07-01

The inter-satellite laser link is the backbone of the next inter-satellite information network, and ranging and communication are the main functions of the inter-satellite laser link. This study focuses on the inter-satellite laser ranging based on the pseudo-code correlation technology. In this paper, several typical laser-ranging methods have been compared and we determined that the laser pseudo-code ranging architecture is more suitable for the inter-satellite laser communication link. The pseudo-code ranging system is easy to combine with a digital communication system, and we used it to calculate integer ambiguity by modulating the time information. The main challenge of the ranging system is range precision, which is the main focus of this paper. First, the framework of the pseudo-code ranging system is introduced; the ranging architecture of dual one-way ranging is used to eliminate the clock error between the two transceivers, and then the uncertainty of the phase detector is analyzed. In the analysis, the carrier to noise ratio and the ranging code rate are constrained by the laser communication link margin and the electronic hardware limitation. Therefore, the relationship between the sampling depth and the phase detector uncertainty is verified. A series of optical fiber channel laser pseudo-code ranging experiments demonstrated the effects of sampling depth on the ranging precision. By adjusting the depth of storage, such as the depth of 1.6 Mb, we obtained a pseudo-range measurement precision of 0.33 mm (1σ), which is equivalent to 0.0001 times code subdivision of 10.23 Mcps pseudo-code. This paper has achieved high precision in a pseudo-range measurements, which is the foundation of the inter-satellite laser link.

A comparative study of the effect of low laser radiation on mast cells in inflammatory fibrous hyperplasia colored and not colored by the toluidine blue; Estudo comparativo do efeito da radiacao laser em baixa intensidade sobre mastocitos de hiperplasias fibrosas inflamatorias coradas e nao coradas por azul de toluidina

Energy Technology Data Exchange (ETDEWEB)

Sawazaki, Iris

2001-07-01

THIS STUDY SHOWS A COMPARATIVE ANALYSIS OF THE EFFECTS OF THE LASER RADIATION IN LOW INTENSITY ON THE MAST CELL DEGRANULATION IN INFLAMMATORY FIBROUS HYPERPLASIA WHEN THEY ARE COLORED OR NOT BY THE TOLUIDINE BLUE. THE DYE WAS USED IN ORDER TO INCREASE THE ABSORPTION OF THE LASER LIGHT BY THE TISSUE. THE INJURE WAS DIVIDED IN THREE EQUAL PARTS, AND EACH PART RECEIVED A DIFFERENT KIND OF TREATMENT. ONE OF THEM WAS REMOVED TO BE THE CONTROL, THE SECOND PART WAS LASER TREATED AND THEN IMMEDIATELY REMOVED AND THE LAST ONE, AFTER BEING SUPERFICIALLY COLORED, WAS LASER TREATED AND THEN IMMEDIATELY REMOVED . THE ORDER OF THE STAGES WAS RANDOMLY CHANGED , THEN THE TIME BETWEEN THE STAGES WOULD NOT INTERFERE IN THE STATISTICAL ANALYSIS OF THE MAST CELL DEGRANULATION RATES. IT WAS FOUND THAT THE MAST CELL DEGRANULATION RATES WERE 49% FOR THE CONTROL GROUP, 87% FOR THE LASER GROUP AND 88% FOR THE COLORED/LASER GROUP. THERE WAS NO SIGNIFICANT STATISTICAL DIFFERENCES BETWEEN THE GROUP LASER TREATED AND THE ONE COLORED/LASER TREATED. HOWEVER, THERE WAS A SIGNIFICANT DIFFERENCE BETWEEN THE CONTROL AND THE TREATED GROUP (PS {<=} 0,01). (AUTHOR)

Opportunities for two-color experiments at the SASE3 undulator line of the European XFEL

Energy Technology Data Exchange (ETDEWEB)

Geloni, Gianluca; Mazza, Tommaso; Meyer, Michael; Serkez, Svitozar [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2017-06-15

X-ray Free Electron Lasers (XFELs) have been proven to generate short and powerful radiation pulses allowing for a wide class of novel experiments. If an XFEL facility supports the generation of two X-ray pulses with different wavelengths and controllable delay, the range of possible experiments is broadened even further to include X-ray-pump/X-ray-probe applications. In this work we discuss the possibility of applying a simple and cost-effective method for producing two-color pulses at the SASE3 soft X-ray beamline of the European XFEL. The technique is based on the installation of a magnetic chicane in the baseline undulator and can be accomplished in several steps. We discuss the scientific interest of this upgrade for the Small Quantum Systems (SQS) instrument, in connection with the high-repetition rate of the European XFEL, and we provide start-to-end simulations up to the radiation focus on the sample, proving the feasibility of our concept.

Properties of the generation of radiation in the near infrared part of the spectrum with a sapphire crystal laser having radiation-induced color centers

International Nuclear Information System (INIS)

Voitovich, A.P.; Grinkevich, V.E.; Kononov, V.A.; Kromskii, G.I.

1986-01-01

This paper investigates the spectral stability of the color centers in sapphire and the energy of lasers in which the active elements were colored with various techniques. Color centers were produced by neutron irradiation. The absorption spectra of the color centers are shown. The transformation of the spectra shows that the mutual conversions of color centers takes place during the thermal annealing of the sapphire; most of the color centers formed have luminescence. Generation or radiation with a tunable frequency was obtained in the case of transverse or quasi-longitudinal excitation by a ruby laser. The results show that ways for increasing the stability of the energy generated by a sapphire laser with color centers can be found

The solid state detector technology for picosecond laser ranging

Science.gov (United States)

Prochazka, Ivan

1993-01-01

We developed an all solid state laser ranging detector technology, which makes the goal of millimeter accuracy achievable. Our design and construction philosophy is to combine the techniques of single photon ranging, ultrashort laser pulses, and fast fixed threshold discrimination while avoiding any analog signal processing within the laser ranging chain. The all solid state laser ranging detector package consists of the START detector and the STOP solid state photon counting module. Both the detectors are working in an optically triggered avalanche switching regime. The optical signal is triggering an avalanche current buildup which results in the generation of a uniform, fast risetime output pulse.

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.

Nonlinear optical response of a gold surface in the visible range: A study by two-color sum-frequency generation spectroscopy. I. Experimental determination.

Science.gov (United States)

Dalstein, L; Revel, A; Humbert, C; Busson, B

2018-04-07

We experimentally determine the effective nonlinear second-order susceptibility of gold over the visible spectral range. To reach that goal, we probe by vibrational two-color sum-frequency generation spectroscopy the methyl stretching region of a dodecanethiol self-assembled monolayer adsorbed on a gold film. The sum-frequency generation spectra show a remarkable shape reversal when the visible probe wavelength is tuned from 435 to 705 nm. After correcting from Fresnel effects, the methyl stretching vibrations serve as an internal reference, allowing to extract the dispersion of the absolute phase and relative amplitude of the effective nonlinear optical response of gold in the visible range.

Young's double-slit interference with two-color biphotons.

Science.gov (United States)

Zhang, De-Jian; Wu, Shuang; Li, Hong-Guo; Wang, Hai-Bo; Xiong, Jun; Wang, Kaige

2017-12-12

In classical optics, Young's double-slit experiment with colored coherent light gives rise to individual interference fringes for each light frequency, referring to single-photon interference. However, two-photon double-slit interference has been widely studied only for wavelength-degenerate biphoton, known as subwavelength quantum lithography. In this work, we report double-slit interference experiments with two-color biphoton. Different from the degenerate case, the experimental results depend on the measurement methods. From a two-axis coincidence measurement pattern we can extract complete interference information about two colors. The conceptual model provides an intuitional picture of the in-phase and out-of-phase photon correlations and a complete quantum understanding about the which-path information of two colored photons.

Colloidal-Quantum-Dot Ring Lasers with Active Color Control.

Science.gov (United States)

le Feber, Boris; Prins, Ferry; De Leo, Eva; Rabouw, Freddy T; Norris, David J

2018-02-14

To improve the photophysical performance of colloidal quantum dots for laser applications, sophisticated core/shell geometries have been developed. Typically, a wider bandgap semiconductor is added as a shell to enhance the gain from the quantum-dot core. This shell is designed to electronically isolate the core, funnel excitons to it, and reduce nonradiative Auger recombination. However, the shell could also potentially provide a secondary source of gain, leading to further versatility in these materials. Here we develop high-quality quantum-dot ring lasers that not only exhibit lasing from both the core and the shell but also the ability to switch between them. We fabricate ring resonators (with quality factors up to ∼2500) consisting only of CdSe/CdS/ZnS core/shell/shell quantum dots using a simple template-stripping process. We then examine lasing as a function of the optical excitation power and ring radius. In resonators with quality factors >1000, excitons in the CdSe cores lead to red lasing with thresholds at ∼25 μJ/cm 2 . With increasing power, green lasing from the CdS shell emerges (>100 μJ/cm 2 ) and then the red lasing begins to disappear (>250 μJ/cm 2 ). We present a rate-equation model that can explain this color switching as a competition between exciton localization into the core and stimulated emission from excitons in the shell. Moreover, by lowering the quality factor of the cavity we can engineer the device to exhibit only green lasing. The mechanism demonstrated here provides a potential route toward color-switchable quantum-dot lasers.

Nonvolatile two-step, two-color holography with continuous-wave lights for both congruent and near-stoichiometric LiNbO3:Fe

International Nuclear Information System (INIS)

Shen Yan; Zhang Guoquan; Fu Bo; Xu Qingjun; Xu Jingjun

2004-01-01

We have studied theoretically the steady-state nonvolatile two-step, two-color holographic recording performance for both the congruent and the near-stoichiometric LiNbO 3 :Fe based on the two-center model (the deep-trap and the shallow-trap centers are Fe 2+ /Fe 3+ and Nb Li 4+ /Nb Li 5+ , respectively). The results show that the direct electron exchange between the Fe 2+ /Fe 3+ centers and the Nb Li 4+ /Nb Li 5+ centers due to the tunneling effect dominates the charge-transfer process during the nonvolatile two-step, two-color holography and determines the two-step, two-color holography performance in LiNbO 3 :Fe. We have further studied the effects of the crystal stoichiometry on the performance of the two-step, two-color holography. It is shown that, as far as the total space-charge field is considered, the nonvolatile two-step, two-color holography performance in the near-stoichiometric LiNbO 3 :Fe is much better than that in the congruent LiNbO 3 :Fe within the intensity range reachable by the continuous-wave lights

Unsynchronized scanning with a low-cost laser range finder for real-time range imaging

Science.gov (United States)

Hatipoglu, Isa; Nakhmani, Arie

2017-06-01

Range imaging plays an essential role in many fields: 3D modeling, robotics, heritage, agriculture, forestry, reverse engineering. One of the most popular range-measuring technologies is laser scanner due to its several advantages: long range, high precision, real-time measurement capabilities, and no dependence on lighting conditions. However, laser scanners are very costly. Their high cost prevents widespread use in applications. Due to the latest developments in technology, now, low-cost, reliable, faster, and light-weight 1D laser range finders (LRFs) are available. A low-cost 1D LRF with a scanning mechanism, providing the ability of laser beam steering for additional dimensions, enables to capture a depth map. In this work, we present an unsynchronized scanning with a low-cost LRF to decrease scanning period and reduce vibrations caused by stop-scan in synchronized scanning. Moreover, we developed an algorithm for alignment of unsynchronized raw data and proposed range image post-processing framework. The proposed technique enables to have a range imaging system for a fraction of the price of its counterparts. The results prove that the proposed method can fulfill the need for a low-cost laser scanning for range imaging for static environments because the most significant limitation of the method is the scanning period which is about 2 minutes for 55,000 range points (resolution of 250x220 image). In contrast, scanning the same image takes around 4 minutes in synchronized scanning. Once faster, longer range, and narrow beam LRFs are available, the methods proposed in this work can produce better results.

Modeling the color perception of port wine stains and its relation to the depth of laser coagulated blood vessels

NARCIS (Netherlands)

Lakmaker, O.; Pickering, J. W.; van Gemert, M. J.

1993-01-01

To find the maximal depth of an ecstatic vessel in the dermis that contributes to the abnormal color of a port wine stain (PWS), "normal" and "laser treated PWS skin" are modeled, respectively, as a two-layer plane parallel geometry consisting of an epidermis and a dermis, and as a three-layer

Note: Digital laser frequency auto-locking for inter-satellite laser ranging.

Science.gov (United States)

Luo, Yingxin; Li, Hongyin; Yeh, Hsien-Chi

2016-05-01

We present a prototype of a laser frequency auto-locking and re-locking control system designed for laser frequency stabilization in inter-satellite laser ranging system. The controller has been implemented on field programmable gate arrays and programmed with LabVIEW software. The controller allows initial frequency calibrating and lock-in of a free-running laser to a Fabry-Pérot cavity. Since it allows automatic recovery from unlocked conditions, benefit derives to automated in-orbit operations. Program design and experimental results are demonstrated.

Note: Digital laser frequency auto-locking for inter-satellite laser ranging

International Nuclear Information System (INIS)

Luo, Yingxin; Yeh, Hsien-Chi; Li, Hongyin

2016-01-01

We present a prototype of a laser frequency auto-locking and re-locking control system designed for laser frequency stabilization in inter-satellite laser ranging system. The controller has been implemented on field programmable gate arrays and programmed with LabVIEW software. The controller allows initial frequency calibrating and lock-in of a free-running laser to a Fabry-Pérot cavity. Since it allows automatic recovery from unlocked conditions, benefit derives to automated in-orbit operations. Program design and experimental results are demonstrated.

Note: Digital laser frequency auto-locking for inter-satellite laser ranging

Energy Technology Data Exchange (ETDEWEB)

Luo, Yingxin; Yeh, Hsien-Chi, E-mail: yexianji@mail.hust.edu.cn [MOE Key Laboratory of Fundamental Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Li, Hongyin [MOE Key Laboratory of Fundamental Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Automation, Huazhong University of Science and Technology, Wuhan 430074 (China)

2016-05-15

We present a prototype of a laser frequency auto-locking and re-locking control system designed for laser frequency stabilization in inter-satellite laser ranging system. The controller has been implemented on field programmable gate arrays and programmed with LabVIEW software. The controller allows initial frequency calibrating and lock-in of a free-running laser to a Fabry-Pérot cavity. Since it allows automatic recovery from unlocked conditions, benefit derives to automated in-orbit operations. Program design and experimental results are demonstrated.

Extended analysis of benchmark datasets for Agilent two-color microarrays

Directory of Open Access Journals (Sweden)

Kerr Kathleen F

2007-10-01

Full Text Available Abstract Background As part of its broad and ambitious mission, the MicroArray Quality Control (MAQC project reported the results of experiments using External RNA Controls (ERCs on five microarray platforms. For most platforms, several different methods of data processing were considered. However, there was no similar consideration of different methods for processing the data from the Agilent two-color platform. While this omission is understandable given the scale of the project, it can create the false impression that there is consensus about the best way to process Agilent two-color data. It is also important to consider whether ERCs are representative of all the probes on a microarray. Results A comparison of different methods of processing Agilent two-color data shows substantial differences among methods for low-intensity genes. The sensitivity and specificity for detecting differentially expressed genes varies substantially for different methods. Analysis also reveals that the ERCs in the MAQC data only span the upper half of the intensity range, and therefore cannot be representative of all genes on the microarray. Conclusion Although ERCs demonstrate good agreement between observed and expected log-ratios on the Agilent two-color platform, such an analysis is incomplete. Simple loess normalization outperformed data processing with Agilent's Feature Extraction software for accurate identification of differentially expressed genes. Results from studies using ERCs should not be over-generalized when ERCs are not representative of all probes on a microarray.

Study of the spectral and energy characteristics of lasing in the green spectral region by lithium fluoride with radiation color centers

Energy Technology Data Exchange (ETDEWEB)

Voitovich, A.P.; Kalinov, V.S.; Mikhnov, S.A.; Ovseichuk, S.I.

1987-06-01

The spectral and energy characteristics of lasers utilizing lithium fluoride with F2 and F3(+) color centers in transverse and longitudinal pumping schemes are studied. The feasibility of obtaining stable narrow-band radiation in the 510-570 nm range using a selective resonator is demonstrated. Consideration is given to the effect of lithium-fluoride crystal processing by excimer laser radiation at a wavelength of 308 nm on the spectroscopic and lasing characteristics of the F3(+) color center. After this processing, the laser efficiency in the green spectral region increases by more than a factor of two (reaching an efficiency of 14 percent). 7 references.

Photonic band gap effect and structural color from silver nanoparticle gelatin emulsion

Science.gov (United States)

Kok, Mang Hin; Ma, Rui; Lee, Jeffrey Chi Wai; Tam, Wing Yim; Chan, C. T.; Sheng, Ping; Cheah, Kok Wai

2005-10-01

We have fabricated planar structures of silver nanoparticles in monochromatic gelatin emulsion with a continuous spacing ranging from 0.15-0.40 micron using a two-beam interference of a single laser source. Our planar holograms display a colorful “rainbow” pattern and photonic bandgaps covering the visible and IR ranges. We model the planar silver nanoparticle-gelatin composite system using an effective medium approach and good agreement is obtained between theory and experiment.

Visualization of Two-Phase Fluid Distribution Using Laser Induced Exciplex Fluorescence

Science.gov (United States)

Kim, J. U.; Darrow, J.; Schock, H.; Golding, B.; Nocera, D.; Keller, P.

1998-03-01

Laser-induced exciplex (excited state complex) fluorescence has been used to generate two-dimensional images of dispersed liquid and vapor phases with spectrally resolved two-color emissions. In this method, the vapor phase is tagged by the monomer fluorescence while the liquid phase is tracked by the exciplex fluorescence. A new exciplex visualization system consisting of DMA and 1,4,6-TMN in an isooctane solvent was developed.(J.U. Kim et al., Chem. Phys. Lett. 267, 323-328 (1997)) The direct ca

Morphology and phase structures of CW laser-induced oxide layers on iron surface with evolving reflectivity and colors

Energy Technology Data Exchange (ETDEWEB)

Wu, Taotao, E-mail: wutaotao@nint.ac.cn; Wang, Lijun; Wei, Chenghua; Zhou, Menglian; He, Minbo; Wu, Lixiong

2016-11-30

Highlights: • Firstly, iron samples with different color features were obtained by continuous wave laser irradiation depending on progressive durations. The real-time reflectivity and temperature of samples were measured. The color and the reflectivity evolution were related. They were both caused by the forming oxide films. • Secondly, laser-induced oxidation process of iron was studied by microscope, X-ray diffraction and Raman spectrum. The first formed magnetite made the surface reflectivity decline rapidly and caused the “positive feedback” effect because of molecular absorption. The later formed hematite oscillated the reflectivity by interference effect. • Lastly, the laser-induced oxide films were thin, orientated and badly crystallized. The Wagner oxidation theory was incapable of describing the non-isothermal and early stage oxidation process. So we emphasized that a precise oxidation model depending on the experiment and the optical constants of the laser-induced oxides must be studied. - Abstract: Laser-induced oxidation will change the laser reflectivity and color features of metal surface. Both changes can be theoretically calculated based on the oxidation kinetics and the optical constants of oxides. For the purpose of calculation, the laser-induced oxidation process of pure polycrystalline iron was studied. Samples with various color features were obtained by continuous wave Nd:YAG fiber laser (1.06 μm) irradiation depending on progressive durations in the intensity of 1.90 W/cm{sup 2}. The real-time reflectivity and temperature were measured with integral sphere and thermocouples. The irradiated surface morphology and phase structures were characterized by microscope, X-ray diffraction and Raman spectrum. It was found that the first formed magnetite made the surface reflectivity decline rapidly and caused the “positive feedback” effect because of molecular absorption. The later formed hematite oscillated the reflectivity by

Auxiliary functions of the LISA laser link: ranging, clock noise transfer and data communication

International Nuclear Information System (INIS)

Heinzel, Gerhard; Esteban, Juan Jose; Barke, Simon; Otto, Markus; Wang Yan; Garcia, Antonio F; Danzmann, Karsten

2011-01-01

The Laser Interferometer Space Antenna (LISA) is required to reduce two important noise sources by post-processing on the ground using time-delay interferometry (TDI): phase noise of the on-board reference clocks and laser frequency noise. To achieve the desired suppression, the TDI algorithm needs measurements of the differential clock noise between any two spacecraft and inter-spacecraft ranging measurements with at least 1 m accuracy, which is beyond the precision of ground-based measurements for deep space missions. Therefore, we need on-board measurements by transmitting clock noise and ranging information between the spacecraft as auxiliary functions of the laser link. This paper reports our current experimental results in clock noise transfer and ranging for noise subtraction via post-processing as well as additional data transfer.

A four-color beam smoothing irradiation system for laser-plasma interaction experiments at LLNL

International Nuclear Information System (INIS)

Pennington, D.M.; Henesian, M.A.; Wilcox, R.B.; Weiland, T.L.; Eimerl, D.; Ehrlich, R.B.; Laumann, C.W.; Miller, J.L.

1995-01-01

A novel four-color beam smoothing scheme with a capability similar to that planned for the proposed National Ignition Facility has been deployed on the Nova laser, and has been successfully used for laser fusion experiments. Wavefront aberrations in high power laser systems produce nonuniformities in the energy distribution of the focal spot that can significantly degrade the coupling of the energy into a fusion target, driving various plasma instabilities. The introduction of temporal and spatial incoherence over the face of the beam using techniques such as smoothing by spectral dispersion (SSD) can reduce these variation in the focal irradiance when averaged over a finite time interval. We developed a multiple frequency source that is spatially separated into four quadrants, each containing a different central frequency. Each quadrant is independently converted to the third harmonic in a four-segment Type I/ Type II KDP crystal array with independent phase-matching for efficient frequency conversion. Up to 2.3 kJ of third harmonic light is generated in a 1 ns pulse, corresponding to up to 65% conversion efficiency. SSD is implemented by adding limited frequency modulated bandwidth to each frequency component. Smoothing by spectral dispersion is implemented during the spatial separation of the FM modulated beams to provide additional smoothing, reaching a 16% rms intensity variation level. The four- color system was successfully used to probe NIF-like plasmas, producing 2x10 15 W/cm 2 . This paper discusses the detailed implementation and performance of the segmented four-color system on the Nova laser system

Design of a real-time two-color interferometer for MAST Upgrade

International Nuclear Information System (INIS)

O’Gorman, T.; Naylor, G.; Scannell, R.; Cunningham, G.; Martin, R.; Croft, D.; Brunner, K. J.

2014-01-01

A single chord two-color CO 2 /HeNe (10.6/0.633 μm) heterodyne laser interferometer has been designed to measure the line integral electron density along the mid-plane of the MAST Upgrade tokamak, with a typical error of 1 × 10 18 m −3 (∼2° phase error) at 4 MHz temporal resolution. To ensure this diagnostic system can be restored from any failures without stopping MAST Upgrade operations, it has been located outside of the machine area. The final design and initial testing of this system, including details of the optics, vibration isolation, and a novel phase detection scheme are discussed in this paper

Laser-induced short- and long-range orderings of Co nanoparticles on SiO2

International Nuclear Information System (INIS)

Favazza, C.; Trice, J.; Krishna, H.; Kalyanaraman, R.; Sureshkumar, R.

2006-01-01

Laser irradiation of ultrathin Co films leads to pattern formation by dewetting with short-range order (SRO) as well as long-range order (LRO). When a 1.5 nm thick Co film is irradiated by a single laser beam, a monomodal size distribution of particles with average diameter of 31±10 nm and nearest-neighbor spacing of 75 nm is observed. Moreover, melting by two-beam interference irradiation produces LRO as well as SRO giving a quasi-two-dimensional arrangement of nanoparticles. The SRO is attributed to spinodal dewetting while the LRO is conjectured to be induced by in-plane interfacial tension gradients. Laser-induced dewetting of metals could be a simple technique to fabricate ordered metal nanoarrays

A 7.2 keV spherical x-ray crystal backlighter for two-frame, two-color backlighting at Sandia's Z Pulsed Power Facility

Science.gov (United States)

Schollmeier, M. S.; Knapp, P. F.; Ampleford, D. J.; Harding, E. C.; Jennings, C. A.; Lamppa, D. C.; Loisel, G. P.; Martin, M. R.; Robertson, G. K.; Shores, J. E.; Smith, I. C.; Speas, C. S.; Weis, M. R.; Porter, J. L.; McBride, R. D.

2017-10-01

Many experiments on Sandia National Laboratories' Z Pulsed Power Facility—a 30 MA, 100 ns rise-time, pulsed-power driver—use a monochromatic quartz crystal backlighter system at 1.865 keV (Si He α ) or 6.151 keV (Mn He α ) x-ray energy to radiograph an imploding liner (cylindrical tube) or wire array z-pinch. The x-ray source is generated by the Z-Beamlet laser, which provides two 527-nm, 1 kJ, 1-ns laser pulses. Radiographs of imploding, thick-walled beryllium liners at convergence ratios CR above 15 [ C R = r i ( 0 ) / r i ( t ) ] using the 6.151-keV backlighter system were too opaque to identify the inner radius r i of the liner with high confidence, demonstrating the need for a higher-energy x-ray radiography system. Here, we present a 7.242 keV backlighter system using a Ge(335) spherical crystal with the Co He α resonance line. This system operates at a similar Bragg angle as the existing 1.865 keV and 6.151 keV backlighters, enhancing our capabilities for two-color, two-frame radiography without modifying the system integration at Z. The first data taken at Z include 6.2-keV and 7.2-keV two-color radiographs as well as radiographs of low-convergence (CR about 4-5), high-areal-density liner implosions.

Color Change for Thermoregulation versus Camouflage in Free-Ranging Lizards.

Science.gov (United States)

Smith, Kathleen R; Cadena, Viviana; Endler, John A; Kearney, Michael R; Porter, Warren P; Stuart-Fox, Devi

2016-12-01

Animal coloration has multiple functions including thermoregulation, camouflage, and social signaling, and the requirements of each function may sometimes conflict. Many terrestrial ectotherms accommodate the multiple functions of color through color change. However, the relative importance of these functions and how color-changing species accommodate them when they do conflict are poorly understood because we lack data on color change in the wild. Here, we show that the color of individual radio-tracked bearded dragon lizards, Pogona vitticeps, correlates strongly with background color and less strongly, but significantly, with temperature. We found no evidence that individuals simultaneously optimize camouflage and thermoregulation by choosing light backgrounds when hot or dark backgrounds when cold. In laboratory experiments, lizards showed both UV-visible (300-700 nm) and near-infrared (700-2,100 nm) reflectance changes in response to different background and temperature treatments, consistent with camouflage and thermoregulatory functions, respectively, but with no interaction between the two. Overall, our results suggest that wild bearded dragons change color to improve both thermoregulation and camouflage but predominantly adjust for camouflage, suggesting that compromising camouflage may entail a greater potential immediate survival cost.

Two-color above-threshold ionization of atoms and ions in XUV Bessel beams and intense laser light

Science.gov (United States)

Seipt, D.; Müller, R. A.; Surzhykov, A.; Fritzsche, S.

2016-11-01

The two-color above-threshold ionization (ATI) of atoms and ions is investigated for a vortex Bessel beam in the presence of a strong near-infrared (NIR) light field. While the photoionization is caused by the photons from the weak but extreme ultraviolet (XUV) vortex Bessel beam, the energy and angular distribution of the photoelectrons and their sideband structure are affected by the plane-wave NIR field. We here explore the energy spectra and angular emission of the photoelectrons in such two-color fields as a function of the size and location of the target atoms with regard to the beam axis. In addition, analog to the circular dichroism in typical two-color ATI experiments with circularly polarized light, we define and discuss seven different dichroism signals for such vortex Bessel beams that arise from the various combinations of the orbital and spin angular momenta of the two light fields. For localized targets, it is found that these dichroism signals strongly depend on the size and position of the atoms relative to the beam. For macroscopically extended targets, in contrast, three of these dichroism signals tend to zero, while the other four just coincide with the standard circular dichroism, similar as for Bessel beams with a small opening angle. Detailed computations of the dichroism are performed and discussed for the 4 s valence-shell photoionization of Ca+ ions.

Evaluation of the hydrogen peroxide and special colorant effects under irradiation by argon and diode laser on tooth-whitening in vitro

International Nuclear Information System (INIS)

Gaspar, Jose Antonio

2003-01-01

The aim of this study is to determine if there is any interaction between special colorant found on bleaching agents that have 35 % of hydrogen peroxide on its composition, and argon or diode laser. The first part of the study was to characterize the extrinsic stain obtained through a staining solution containing products present on the day by day diet of the general population. Thirty-two inferior human extracted incisors, free of caries and without filling material were selected for the study. The laser devices employed were Argon laser (AccuCure 3000 TM - Lasermed), wave length 488 nm, with a 200 mW/cm 2 for 30 seconds in continuos mode; and diode laser (L 808 Medical Laser - Lasering do Brasil), wave length 808 ± 10 nm, with 1,6 W/cm 2 for 30 seconds in continuos mode. The application mode done by a scanning movement over the buccal surface. The bleaching agents used were: Opalescence Extra (OE) - Ultradent Products USA, hydrogen peroxide 35%, gel with Carotene to convert light into heat; Pola Office (PO) - SDI - USA single doses of hydrogen peroxide; Whiteness HP (WHP) - FGM - Brasil, hydrogen peroxide 35%; Opus White (OW) - Sharplan - Israel, hydrogen peroxide 35%. The temperature rise measurement was performed with a thermocouple model 120-202-AJ, Fenwal, inserted into the pulpar chamber. The bleaching material was applied on the tooth surface with 2 mm thickness and then the irradiation was perform. The thirty two teeth were randomized in four groups, two for each laser device. The obtain data demonstrated a superior performance of the Argon laser on tooth whitening and also better results concerning the temperature rise. The alteration on tooth coloration was verified through digital spectrophotometer (Shade-Eye EX - Shofu) and quantitative analyses showed statistical differences among the groups. The bleaching results for Argon laser combined with OE and WHP were superior for the other groups. The mean variation of the temperature rise obtained Argon

Tests of Gravity Using Lunar Laser Ranging

Directory of Open Access Journals (Sweden)

Stephen M. Merkowitz

2010-11-01

Full Text Available Lunar laser ranging (LLR has been a workhorse for testing general relativity over the past four decades. The three retroreflector arrays put on the Moon by the Apollo astronauts and the French built arrays on the Soviet Lunokhod rovers continue to be useful targets, and have provided the most stringent tests of the Strong Equivalence Principle and the time variation of Newton’s gravitational constant. The relatively new ranging system at the Apache Point 3.5 meter telescope now routinely makes millimeter level range measurements. Incredibly, it has taken 40 years for ground station technology to advance to the point where characteristics of the lunar retroreflectors are limiting the precision of the range measurements. In this article, we review the gravitational science and technology of lunar laser ranging and discuss prospects for the future.

Direct measuring of single-cycle mid-IR light bullets path length in LiF by the laser coloration method

Directory of Open Access Journals (Sweden)

Chekalin Sergey

2017-01-01

Full Text Available A colour-centre structure formed in a LiF crystal under filamentation of a femtosecond mid-IR laser pulse with a power slightly exceeding the critical power for self-focusing has been experimentally and theoretically investigated. A single-cycle light bullet was recorded for the first time by observation of strictly periodic oscillations for the density of the color centers induced in an isotropic LiF crystal under filamentation of a laser beam with a wavelength tuned in the range from 2600 to 3900 nm, which is due to the periodic change in the light field amplitude in the light bullet formed under filamentation under propagation in dispersive medium. The light bullet path length was not more than one millimeter.

Broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity

Science.gov (United States)

Li, Q.; Jia, Z. X.; Weng, H. Z.; Li, Z. R.; Yang, Y. D.; Xiao, J. L.; Chen, S. W.; Huang, Y. Z.; Qin, W. P.; Qin, G. S.

2018-05-01

We demonstrate broadband multi-wavelength Brillouin lasers with an operating wavelength range of 1500–1600 nm and a frequency separation of ~9.28 GHz generated by four-wave mixing in a dual wavelength Brillouin fiber laser cavity. By using one continuous-wave laser as the pump source, multi-wavelength Brillouin lasers with an operating wavelength range of 1554–1574 nm were generated via cascaded Brillouin scattering and four-wave mixing. Interestingly, when pumped by two continuous-wave lasers with an appropriate frequency separation, the operating wavelength range of the multi-wavelength Brillouin lasers was increased to 1500–1600 nm due to cavity-enhanced cascaded four-wave mixing among the frequency components generated by two pump lasers in the dual wavelength Brillouin laser cavity.

Simultaneous Laser Ranging and Communication from an Earth-Based Satellite Laser Ranging Station to the Lunar Reconnaissance Orbiter in Lunar Orbit

Science.gov (United States)

Sun, Xiaoli; Skillman, David R.; Hoffman, Evan D.; Mao, Dandan; McGarry, Jan F.; Neumann, Gregory A.; McIntire, Leva; Zellar, Ronald S.; Davidson, Frederic M.; Fong, Wai H.;

Probing Xe electronic structure by two-color HHG

International Nuclear Information System (INIS)

Faccialà, D; Ciriolo, A G; De Silvestri, S; Devetta, M; Negro, M; Stagira, S; Vozzi, C; Pabst, S; Bruner, B D; Dudovich, N; Soifer, H

2015-01-01

The aim of this study is probing the multi-electron behavior in xenon by two-color driven high harmonic generation. By changing the relative polarization of the two colors we were able to study different aspects of the multi-electron response. (paper)

Fast and robust wavelet-based dynamic range compression and contrast enhancement model with color restoration

Science.gov (United States)

Unaldi, Numan; Asari, Vijayan K.; Rahman, Zia-ur

2009-05-01

Recently we proposed a wavelet-based dynamic range compression algorithm to improve the visual quality of digital images captured from high dynamic range scenes with non-uniform lighting conditions. The fast image enhancement algorithm that provides dynamic range compression, while preserving the local contrast and tonal rendition, is also a good candidate for real time video processing applications. Although the colors of the enhanced images produced by the proposed algorithm are consistent with the colors of the original image, the proposed algorithm fails to produce color constant results for some "pathological" scenes that have very strong spectral characteristics in a single band. The linear color restoration process is the main reason for this drawback. Hence, a different approach is required for the final color restoration process. In this paper the latest version of the proposed algorithm, which deals with this issue is presented. The results obtained by applying the algorithm to numerous natural images show strong robustness and high image quality.

Long axial imaging range using conventional swept source lasers in optical coherence tomography via re-circulation loops

Science.gov (United States)

Bradu, Adrian; Jackson, David A.; Podoleanu, Adrian

2018-03-01

Typically, swept source optical coherence tomography (SS-OCT) imaging instruments are capable of a longer axial range than their camera based (CB) counterpart. However, there are still various applications that would take advantage for an extended axial range. In this paper, we propose an interferometer configuration that can be used to extend the axial range of the OCT instruments equipped with conventional swept-source lasers up to a few cm. In this configuration, the two arms of the interferometer are equipped with adjustable optical path length rings. The use of semiconductor optical amplifiers in the two rings allows for compensating optical losses hence, multiple paths depth reflectivity profiles (Ascans) can be combined axially. In this way, extremely long overall axial ranges are possible. The use of the recirculation loops produces an effect equivalent to that of extending the coherence length of the swept source laser. Using this approach, the achievable axial imaging range in SS-OCT can reach values well beyond the limit imposed by the coherence length of the laser, to exceed in principle many centimeters. In the present work, we demonstrate axial ranges exceeding 4 cm using a commercial swept source laser and reaching 6 cm using an "in-house" swept source laser. When used in a conventional set-up alone, both these lasers can provide less than a few mm axial range.

Interim report - performance of laser and radar ranging devices in adverse environmental conditions

Energy Technology Data Exchange (ETDEWEB)

Nicholas Hillier; Julian Ryde; Eleonora WidzykCapehart; Graham Brooker; Javier Martinez; Andrew Denman [CSIRO (Australia)

2008-10-15

CSIRO in conjunction with CRC Mining and the Australian Centre for Field Robotics (ACFR) conducted a series of controlled experiments to examine the performance of three scanning range devices: two scanning infrared laser range finders and millimetrewave radar. Within the controlled environment, the performance of the devices were tested in various rain, mist and dustcloud conditions. Subsequently, these sensors were installed on a P&H 2800BLE electric rope shovel at the Bracalba Quarry, near Caboolture, Queensland, and the system performance was evaluated. The three scanning range sensors tested as part of this study were: 1. A Riegl LMSQ120 scanning laser range finder; 2. A SICK LMS291S05 scanning laser range finder; and, 3. ACFR's prototype 95GHz millimetrewave radar (2D HSS). The range data from these devices is to be used to construct accurate models of the environment in which the electric rope shovel operates and to, subsequently, make control decisions for its operation. Of the currently available range sensing technologies, it is considered that the infrared laser range finders and millimetrewave radar offer the best means of obtaining this data. This report summarises the results of both the controlled (laboratory) and field testing and presents key findings on sensor performance that are likely to impact the creation of digital models of the terrain surrounding a mining shovel.

New progress of ranging technology at Wuhan Satellite Laser Ranging Station

Science.gov (United States)

Xia, Zhiz-Hong; Ye, Wen-Wei; Cai, Qing-Fu

1993-01-01

A satellite laser ranging system with an accuracy of the level of centimeter has been successfully developed at the Institute of Seismology, State Seismological Bureau with the cooperation of the Institute of Geodesy and Geophysics, Chinese Academy of Science. With significant improvements on the base of the second generation SLR system developed in 1985, ranging accuracy of the new system has been upgraded from 15 cm to 3-4 cm. Measuring range has also been expanded, so that the ETALON satellite with an orbit height of 20,000 km launched by the former U.S.S.R. can now be tracked. Compared with the 2nd generation SLR system, the newly developed system has the following improvements. A Q modulated laser is replaced by a mode-locked YAG laser. The new device has a pulse width of 150 ps and a repetition rate of 1-4 pps. A quick response photomultiplier has been adopted as the receiver for echo; for example, the adoption of the MCP tube has obviously reduced the jitter error of the transit time and has improved the ranging accuracy. The whole system is controlled by an IBM PC/XT Computer to guide automatic tracking and measurement. It can carry out these functions for satellite orbit calculation, real-time tracking and adjusting, data acquisition and the preprocessed of observing data, etc. The automatization level and reliability of the observation have obviously improved.

Demonstrator study for micro-ranging-laser device

Science.gov (United States)

Henkel, Hartmut; Bernhardt, Bodo; Pereira do Carmo, J.

2017-11-01

Within ESA's Innovation Triangle Initiative (ITI) a demonstrator breadboard for a micro-ranging-laser device "MYLRAD" has been developed. Its working principle is the measurement of the round-trip delay time of a laser beam as a phase shift. The demonstrator consists of the laser diode (30 mW, square wave AM), optics, APD detector, narrowband preamplifier, limiter, and a phase digitiser based on a novel noise-shaping synchroniser (NSS) circuit; this works without ADCs and can be built from rad-hard components for space. The system timing and the digitiser algorithm are performed by an FPGA. The demonstrator has been tested at ranges from 1 m to 30 m. With a static non-cooperative target an RMS noise of 1 mm at a result rate of 60 Hz was reached. The demonstrator needs less than 2.5 W power.

Controlling the Branching Ratio of Photoionization Products under Two-Color Excitation: Competition between ac Stark Splitting and Two-Path Interference

International Nuclear Information System (INIS)

Nakajima, T.; Zhang, J.; Lambropoulos, P.; Lambropoulos, P.

1997-01-01

We investigate the variation of the photoionization yields into different ionic channels by means of the one-photon-near-resonant two-photon ionization scheme under two-color excitation. We present a general formulation and the results of specific calculations pertaining to the Ca atom with realistic parameters. A significant change of the ionization into Ca + 4s , 3d , and 4p channels has been observed as a detuning is varied, which agrees qualitatively well with the observation by Wang, Chen, and Elliott [Phys.Rev.Lett.77, 2416 (1996)] for the Ba atom. The importance of the laser intensity effects is also addressed. copyright 1997 The American Physical Society

Laser-ranging scanning system to observe topographical deformations of volcanoes.

Science.gov (United States)

Aoki, T; Takabe, M; Mizutani, K; Itabe, T

1997-02-20

We have developed a laser-ranging system to observe the topographical structure of volcanoes. This system can be used to measure the distance to a target by a laser and shows the three-dimensional topographical structure of a volcano with an accuracy of 30 cm. This accuracy is greater than that of a typical laser-ranging system that uses a corner-cube reflector as a target because the reflected light jitters as a result of inclination and unevenness of the target ground surface. However, this laser-ranging system is useful for detecting deformations of topographical features in which placement of a reflector is difficult, such as in volcanic regions.

Method of high precision interval measurement in pulse laser ranging system

Science.gov (United States)

Wang, Zhen; Lv, Xin-yuan; Mao, Jin-jin; Liu, Wei; Yang, Dong

2013-09-01

Laser ranging is suitable for laser system, for it has the advantage of high measuring precision, fast measuring speed,no cooperative targets and strong resistance to electromagnetic interference,the measuremen of laser ranging is the key paremeters affecting the performance of the whole system.The precision of the pulsed laser ranging system was decided by the precision of the time interval measurement, the principle structure of laser ranging system was introduced, and a method of high precision time interval measurement in pulse laser ranging system was established in this paper.Based on the analysis of the factors which affected the precision of range measure,the pulse rising edges discriminator was adopted to produce timing mark for the start-stop time discrimination,and the TDC-GP2 high precision interval measurement system based on TMS320F2812 DSP was designed to improve the measurement precision.Experimental results indicate that the time interval measurement method in this paper can obtain higher range accuracy. Compared with the traditional time interval measurement system,the method simplifies the system design and reduce the influence of bad weather conditions,furthermore,it satisfies the requirements of low costs and miniaturization.

Influence of temperature on the spectral characteristics of semiconductor lasers in the visible range

Science.gov (United States)

Adamov, A. A.; Baranov, M. S.; Khramov, V. N.

2018-04-01

The results of studies on the effect of temperature on the output spectral characteristics of continuous semiconductor lasers of the visible range are presented. The paper presents the results of studying the spectral-optical radiation parameters of semiconductor lasers, their coherence lengths, and the dependence of the position of the spectral peak of the wavelength on temperature. This is necessary for the selection of the most optimal laser in order to use it for medical ophthalmologic diagnosis. The experiment was carried out using semiconductor laser modules based on a laser diode. The spectra were recorded by using a two-channel automated spectral complex based on the MDR-23 monochromator. Spectral dependences on the temperature of semiconductor lasers are obtained, in the range from 300 to 370 K. The possibility of determining the internal damage to the stabilization of laser modules without opening the case is shown, but only with the use of their spectral characteristics. The obtained data allow taking into account temperature characteristics and further optimization of parameters of such lasers when used in medical practice, in particular, in ophthalmologic diagnostics.

Laser diode stack beam shaping for efficient and compact long-range laser illuminator design

Science.gov (United States)

Lutz, Y.; Poyet, J. M.

2014-04-01

Laser diode stacks are interesting laser sources for active imaging illuminators. They allow the accumulation of large amounts of energy in multi-pulse mode, which is best suited for long-range image recording. Even when the laser diode stacks are equipped with fast-axis collimation (FAC) and slow-axis collimation (SAC) micro-lenses, their beam parameter products BPP are not compatible with direct use in highly efficient and compact illuminators. This is particularly true when narrow divergences are required such as for long-range applications. A solution to overcome these difficulties is to enhance the poor slow-axis BPP by virtually restacking the laser diode stack. We present a beam shaping and homogenization method that is low-cost and efficient and has low alignment sensitivity. After conducting simulations, we have realized and characterized the illuminator. A compact long-range laser illuminator has been set up with a divergence of 3.5×2.6 mrad and a global efficiency of 81%. Here, a projection lens with a clear aperture of 62 mm and a focal length of 571 mm was used.

Skin color and tissue thickness effects on transmittance, reflectance, and skin temperature when using 635 and 808 nm lasers in low intensity therapeutics.

Science.gov (United States)

Souza-Barros, Leanna; Dhaidan, Ghaith; Maunula, Mikko; Solomon, Vaeda; Gabison, Sharon; Lilge, Lothar; Nussbaum, Ethne L

2018-04-01

To examine the role of skin color and tissue thickness on transmittance, reflectance, and skin heating using red and infrared laser light. Forty volunteers were measured for skin color and skin-fold thickness at a standardized site near the elbow. Transmittance, reflectance and skin temperature were recorded for energy doses of 2, 6, 9, and 12 Joules using 635 nm (36 mW) and 808 nm (40 mW) wavelength laser diodes with irradiances within American National Standards Institute safety guidelines (4.88 mm diameter, 0.192 W/cm 2 and 4.88 mm diameter, 0.214 W/cm 2 , respectively). The key factors affecting reflectance to an important degree were skin color and wavelength. However, the skin color effects were different for the two wavelengths: reflectance decreased for darker skin with a greater decrease for red light than near infrared light. Transmittance was greater using 808 nm compared with 635 nm. However, the effect was partly lost when the skin was dark rather than light, and was increasingly lost as tissue thickness increased. Dose had an increasing effect on temperature (0.7-1.6°C across the 6, 9, and 12 J doses); any effects of wavelength, skin color, and tissue thickness were insignificant compared to dose effects. Subjects themselves were not aware of the increased skin temperature. Transmittance and reflectance changes as a function of energy were very small and likely of no clinical significance. Absorption did not change with higher energy doses and increasing temperature. Skin color and skin thickness affect transmittance and reflectance of laser light and must be accounted for when selecting energy dose to ensure therapeutic effectiveness at the target tissue. Skin heating appears not to be a concern when using 635 and 808 nm lasers at energy doses of up to 12 J and irradiance within American National Standards Institute standards. Photobiomodulation therapy should never exceed the American National Standards Institute

Tuning range and output power optimization of an external-cavity GaN diode laser at 455 nm

DEFF Research Database (Denmark)

Chi, Mingjun; Jensen, Ole Bjarlin; Petersen, Paul Michael

2016-01-01

In this paper we discuss how different feedback gratings affect the tuning range and the output power of external feedback diode laser systems. A tunable high-power narrow-spectrum external-cavity diode laser system around 455 nm is investigated. The laser system is based on a high-power GaN diode...... laser in a Littrow external-cavity. Both a holographic diffraction grating and a ruled diffraction grating are used as feedback elements in the external cavity. The output power, spectral bandwidth, and tunable range of the external cavity diode laser system are measured and compared with the two...... gratings at different injected currents. When the holographic grating is used, the laser system can be tuned over a range of 1.4 nm with an output power around 530 mW. When the ruled grating is used, the laser system can be tuned over a range of 6.0 nm with an output power around 80 mW. The results can...

Interplanetary laser ranging - an emerging technology for planetary science missions

Science.gov (United States)

Dirkx, D.; Vermeersen, L. L. A.

2012-09-01

Interplanetary laser ranging (ILR) is an emerging technology for very high accuracy distance determination between Earth-based stations and spacecraft or landers at interplanetary distances. It has evolved from laser ranging to Earth-orbiting satellites, modified with active laser transceiver systems at both ends of the link instead of the passive space-based retroreflectors. It has been estimated that this technology can be used for mm- to cm-level accuracy range determination at interplanetary distances [2, 7]. Work is being performed in the ESPaCE project [6] to evaluate in detail the potential and limitations of this technology by means of bottom-up laser link simulation, allowing for a reliable performance estimate from mission architecture and hardware characteristics.

Multiple-Zone Diffractive Optic Element for Laser Ranging Applications

Science.gov (United States)

Ramos-Izquierdo, Luis A.

2011-01-01

A diffractive optic element (DOE) can be used as a beam splitter to generate multiple laser beams from a single input laser beam. This technology has been recently used in LRO s Lunar Orbiter Laser Altimeter (LOLA) instrument to generate five laser beams that measure the lunar topography from a 50-km nominal mapping orbit (see figure). An extension of this approach is to use a multiple-zone DOE to allow a laser altimeter instrument to operate over a wider range of distances. In particular, a multiple-zone DOE could be used for applications that require both mapping and landing on a planetary body. In this case, the laser altimeter operating range would need to extend from several hundred kilometers down to a few meters. The innovator was recently involved in an investigation how to modify the LOLA instrument for the OSIRIS asteroid mapping and sample return mission. One approach is to replace the DOE in the LOLA laser beam expander assembly with a multiple-zone DOE that would allow for the simultaneous illumination of the asteroid with mapping and landing laser beams. The proposed OSIRIS multiple-zone DOE would generate the same LOLA five-beam output pattern for high-altitude topographic mapping, but would simultaneously generate a wide divergence angle beam using a small portion of the total laser energy for the approach and landing portion of the mission. Only a few percent of the total laser energy is required for approach and landing operations as the return signal increases as the inverse square of the ranging height. A wide divergence beam could be implemented by making the center of the DOE a diffractive or refractive negative lens. The beam energy and beam divergence characteristics of a multiple-zone DOE could be easily tailored to meet the requirements of other missions that require laser ranging data. Current single-zone DOE lithographic manufacturing techniques could also be used to fabricate a multiple-zone DOE by masking the different DOE zones during

Two-stage free electron laser research

Science.gov (United States)

Segall, S. B.

1984-10-01

KMS Fusion, Inc. began studying the feasibility of two-stage free electron lasers for the Office of Naval Research in June, 1980. At that time, the two-stage FEL was only a concept that had been proposed by Luis Elias. The range of parameters over which such a laser could be successfully operated, attainable power output, and constraints on laser operation were not known. The primary reason for supporting this research at that time was that it had the potential for producing short-wavelength radiation using a relatively low voltage electron beam. One advantage of a low-voltage two-stage FEL would be that shielding requirements would be greatly reduced compared with single-stage short-wavelength FEL's. If the electron energy were kept below about 10 MeV, X-rays, generated by electrons striking the beam line wall, would not excite neutron resonance in atomic nuclei. These resonances cause the emission of neutrons with subsequent induced radioactivity. Therefore, above about 10 MeV, a meter or more of concrete shielding is required for the system, whereas below 10 MeV, a few millimeters of lead would be adequate.

Laser long-range remote-sensing program experimental results

Science.gov (United States)

Highland, Ronald G.; Shilko, Michael L.; Fox, Marsha J.; Gonglewski, John D.; Czyzak, Stanley R.; Dowling, James A.; Kelly, Brian; Pierrottet, Diego F.; Ruffatto, Donald; Loando, Sharon; Matsuura, Chris; Senft, Daniel C.; Finkner, Lyle; Rae, Joe; Gallegos, Joe

1995-12-01

A laser long range remote sensing (LRS) program is being conducted by the United States Air Force Phillips Laboratory (AF/PL). As part of this program, AF/PL is testing the feasibility of developing a long path CO(subscript 2) laser-based DIAL system for remote sensing. In support of this program, the AF/PL has recently completed an experimental series using a 21 km slant- range path (3.05 km ASL transceiver height to 0.067 km ASL target height) at its Phillips Laboratory Air Force Maui Optical Station (AMOS) facility located on Maui, Hawaii. The dial system uses a 3-joule, (superscript 13)C isotope laser coupled into a 0.6 m diameter telescope. The atmospheric optical characterization incorporates information from an infrared scintillometer co-aligned to the laser path, atmospheric profiles from weather balloons launched from the target site, and meteorological data from ground stations at AMOS and the target site. In this paper, we report a description of the experiment configuration, a summary of the results, a summary of the atmospheric conditions and their implications to the LRS program. The capability of such a system for long-range, low-angle, slant-path remote sensing is discussed. System performance issues relating to both coherent and incoherent detection methods, atmospheric limitations, as well as, the development of advanced models to predict performance of long range scenarios are presented.

Comparative study of the action of two different types of bleaching agents activated by two different types of irradiation fonts: xenon plasma arc lamp and 960 nm diode laser

International Nuclear Information System (INIS)

Walverde, Debora Ayala

2001-01-01

This in vitro study compares two different types of tooth bleaching agents stimulated with two different irradiation fonts. These fonts accelerate the action of the bleaching agents upon the enamel surface by heating up the materials. We used the xenon plasma arc lamp and a 960 nm fiber-coupled diode laser to irradiate the two materials containing 35% of hydrogen peroxide (Opus White and Opalescence extra). The color of the teeth was measured with a spectrophotometer using the CIELAB color system that gives the numeric values of L * a * b * . (author)

Measurements of excited-state-to-excited-state transition probabilities and photoionization cross-sections using laser-induced fluorescence and photoionization signals

International Nuclear Information System (INIS)

Shah, M.L.; Sahoo, A.C.; Pulhani, A.K.; Gupta, G.P.; Dikshit, B.; Bhatia, M.S.; Suri, B.M.

2014-01-01

Laser-induced photoionization and fluorescence signals were simultaneously observed in atomic samarium using Nd:YAG-pumped dye lasers. Two-color, three-photon photoionization and two-color fluorescence signals were recorded simultaneously as a function of the second-step laser power for two photoionization pathways. The density matrix formalism has been employed to analyze these signals. Two-color laser-induced fluorescence signal depends on the laser powers used for the first and second-step transitions as well as the first and second-step transition probability whereas two-color, three-photon photoionization signal depends on the third-step transition cross-section at the second-step laser wavelength along with the laser powers and transition probability for the first and second-step transitions. Two-color laser-induced fluorescence was used to measure the second-step transition probability. The second-step transition probability obtained was used to infer the photoionization cross-section. Thus, the methodology combining two-color, three-photon photoionization and two-color fluorescence signals in a single experiment has been established for the first time to measure the second-step transition probability as well as the photoionization cross-section. - Highlights: • Laser-induced photoionization and fluorescence signals have been simultaneously observed. • The density matrix formalism has been employed to analyze these signals. • Two-color laser-induced fluorescence was used to measure the second-step transition probability. • The second-step transition probability obtained was used to infer the photoionization cross-section. • Transition probability and photoionization cross-section have been measured in a single experiment

Two-dimensional color-code quantum computation

International Nuclear Information System (INIS)

Fowler, Austin G.

2011-01-01

We describe in detail how to perform universal fault-tolerant quantum computation on a two-dimensional color code, making use of only nearest neighbor interactions. Three defects (holes) in the code are used to represent logical qubits. Triple-defect logical qubits are deformed into isolated triangular sections of color code to enable transversal implementation of all single logical qubit Clifford group gates. Controlled-NOT (CNOT) is implemented between pairs of triple-defect logical qubits via braiding.

High contrast laser marking of alumina

International Nuclear Information System (INIS)

Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; Val, J. del; Comesaña, R.; Lusquiños, F.; Pou, J.

2015-01-01

Highlights: • Laser marking of alumina using near infrared (NIR) lasers was experimentally analyzed. • Color change produced by NIR lasers is due to thermally induced oxygen vacancies. • Laser marking results obtained using NIR lasers and green laser are compared. • High contrast marks on alumina were achieved. - Abstract: Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks

Spatial properties of a terahertz beam generated from a two-color air plasma

DEFF Research Database (Denmark)

Pedersen, Pernille Klarskov; Wang, Tianwu; Buron, Jonas Christian Due

2013-01-01

We present a spatial characterization of terahertz (THz) beams generated from a two-color air plasma under different conditions by measuring full 3D beam profiles using a commercial THz camera. We compare two THz beam profiles emitted from plasmas generated by 35 fs and 100 fs laser pulses...... that this reduces the beam waist, and that the beam spot shape changes from Lorentzian to Gaussian. Finally, we observe a forward-propagating Gaussian THz beam by spatially filtering away the conical off-axis radiation with a 1 cm aperture......., and show that the spatial properties of the two THz beams do not change significantly. For the THz beam profile generated by the 35 fs pulse, the spatial effect of eliminating the lower frequencies is investigated by implementing two crossed polarizers working as a high-pass filter. We show...

International Laser Ranging Service (ILRS): Terms of Reference

Science.gov (United States)

Husson, Van; Noll, Carey

2000-01-01

The International Laser Ranging Service (ILRS) is an established Service within Section II , Advanced Space Technology, of the International Association of Geodesy (IAG). The primary objective of the ILRS is to provide a service to support, through Satellite and Lunar Laser Ranging data and related products, geodetic and geophysical research activities as well as International Earth Rotation Service (IERS) products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF). The service also develops the necessary standards/specifications and encourages international adherence to its conventions.

Optical microscope using an interferometric source of two-color, two-beam entangled photons

Science.gov (United States)

Dress, William B.; Kisner, Roger A.; Richards, Roger K.

2004-07-13

Systems and methods are described for an optical microscope using an interferometric source of multi-color, multi-beam entangled photons. A method includes: downconverting a beam of coherent energy to provide a beam of multi-color entangled photons; converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; transforming at least a portion of the converged multi-color entangled photon beam by interaction with a sample to generate an entangled photon specimen beam; and combining the entangled photon specimen beam with an entangled photon reference beam within a single beamsplitter. An apparatus includes: a multi-refringent device providing a beam of multi-color entangled photons; a condenser device optically coupled to the multi-refringent device, the condenser device converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; a beam probe director and specimen assembly optically coupled to the condenser device; and a beam splitter optically coupled to the beam probe director and specimen assembly, the beam splitter combining an entangled photon specimen beam from the beam probe director and specimen assembly with an entangled photon reference beam.

Laser tissue welding mediated with a protein solder

Science.gov (United States)

Small, Ward, IV; Heredia, Nicholas J.; Celliers, Peter M.; Da Silva, Luiz B.; Eder, David C.; Glinsky, Michael E.; London, Richard A.; Maitland, Duncan J.; Matthews, Dennis L.; Soltz, Barbara A.

1996-05-01

A study of laser tissue welding mediated with an indocyanine green dye-enhanced protein solder was performed. Freshly obtained sections of porcine artery were used for the experiments. Sample arterial wall thickness ranged from two to three millimeters. Incisions approximately four millimeters in length were treated using an 805 nanometer continuous- wave diode laser coupled to a one millimeter diameter fiber. Controlled parameters included the power delivered by the laser, the duration of the welding process, and the concentration of dye in the solder. A two-color infrared detection system was constructed to monitor the surface temperatures achieved at the weld site. Burst pressure measurements were made to quantify the strengths of the welds immediately following completion of the welding procedure.

Modeling a color-rendering operator for high dynamic range images using a cone-response function

Science.gov (United States)

Choi, Ho-Hyoung; Kim, Gi-Seok; Yun, Byoung-Ju

2015-09-01

Tone-mapping operators are the typical algorithms designed to produce visibility and the overall impression of brightness, contrast, and color of high dynamic range (HDR) images on low dynamic range (LDR) display devices. Although several new tone-mapping operators have been proposed in recent years, the results of these operators have not matched those of the psychophysical experiments based on the human visual system. A color-rendering model that is a combination of tone-mapping and cone-response functions using an XYZ tristimulus color space is presented. In the proposed method, the tone-mapping operator produces visibility and the overall impression of brightness, contrast, and color in HDR images when mapped onto relatively LDR devices. The tone-mapping resultant image is obtained using chromatic and achromatic colors to avoid well-known color distortions shown in the conventional methods. The resulting image is then processed with a cone-response function wherein emphasis is placed on human visual perception (HVP). The proposed method covers the mismatch between the actual scene and the rendered image based on HVP. The experimental results show that the proposed method yields an improved color-rendering performance compared to conventional methods.

Design and Development of High-Repetition-Rate Satellite Laser Ranging System

Science.gov (United States)

Choi, Eun-Jung; Bang, Seong-Cheol; Sung, Ki-Pyoung; Lim, Hyung-Chul; Jung, Chan-Gyu; Kim, In-Yeung; Choi, Jae-Seung

2015-09-01

The Accurate Ranging System for Geodetic Observation ? Mobile (ARGO-M) was successfully developed as the first Korean mobile Satellite Laser Ranging (SLR) system in 2012, and has joined in the International Laser Ranging Service (ILRS) tracking network, DAEdeoK (DAEK) station. The DAEK SLR station was approved as a validated station in April 2014, through the ILRS station ¡°data validation¡± process. The ARGO-M system is designed to enable 2 kHz laser ranging with millimeter-level precision for geodetic, remote sensing, navigation, and experimental satellites equipped with Laser Retroreflector Arrays (LRAs). In this paper, we present the design and development of a next generation high-repetition-rate SLR system for ARGO-M. The laser ranging rate up to 10 kHz is becoming an important issue in the SLR community to improve ranging precision. To implement high-repetition-rate SLR system, the High-repetition-rate SLR operation system (HSLR-10) was designed and developed using ARGO-M Range Gate Generator (A-RGG), so as to enable laser ranging from 50 Hz to 10 kHz. HSLR-10 includes both hardware controlling software and data post-processing software. This paper shows the design and development of key technologies of high-repetition-rate SLR system. The developed system was tested successfully at DAEK station and then moved to Sejong station, a new Korean SLR station, on July 1, 2015. HSLR-10 will begin normal operations at Sejong station in the near future.

Probing General Relativity and New Physics with Lunar Laser Ranging

Energy Technology Data Exchange (ETDEWEB)

Dell' Agnello, S. [Laboratori Nazionali di Frascati (LNF) dell' INFN, Frascati, Rome (Italy); Maiello, M., E-mail: mauro.maiello@lnf.infn.it [Laboratori Nazionali di Frascati (LNF) dell' INFN, Frascati, Rome (Italy); Currie, D.G. [University of Maryland (UMD), College Park, MD (United States); Boni, A.; Berardi, S.; Cantone, C.; Delle Monache, G.O.; Intaglietta, N.; Lops, C.; Garattini, M.; Martini, M.; Patrizi, G.; Porcelli, L.; Tibuzzi, M. [Laboratori Nazionali di Frascati (LNF) dell' INFN, Frascati, Rome (Italy); Vittori, R. [Aeronautica Militare Italiana (AMI), Rome (Italy); Agenzia Spaziale Italiana (ASI), Rome (Italy); Bianco, G. [ASI-Centro di Geodesia Spaziale, Matera (Italy); Coradini, A. [INAF-Istituto di Fisica dello Spazio Interplanetario (IFSI), Via Fosso del Cavaliere 100, 00133 Rome (Italy); Dionisio, C. [Rheinmetall Italia S.p.A., Via Affile 102, 00131 Rome (Italy); March, R. [INFN-LNF and CNR-Istituto per le Applicazioni del Calcolo (IAC), Viale del Policlinico 137, 00161 Rome (Italy); Bellettini, G. [INFN-LNF and Department of Mathematics, University of Rome ' Tor Vergata' , Via della Ricerca Scientifica, 00133 Rome (Italy); and others

2012-11-11

Over the past 40 years, Lunar Laser Ranging (LLR, developed by the Univ. of Maryland (PI) and INFN-LNF (Co-PI)) to the Apollo Cube Corner Retroreflector (CCR) arrays have supplied almost all the significant tests of General Relativity (Currie et al., 2009 [12]). LLR can evaluate the PPN (Post Newtonian Parameters), addressing this way both the possible changes in the gravitational constant and the self-energy properties of the gravitational field. In addition, the LLR has provided significant information on the composition and origin of the Moon. This is the only Apollo experiment that is still in operation. Initially the Apollo LLR arrays contributed a negligible fraction of the ranging error budget. Over the decades, the ranging capabilities of the ground stations have improved by more than two orders of magnitude. Now, because of the lunar librations, the existing Apollo retroreflector arrays contribute a significant fraction of the limiting errors in the range measurements. We built a new experimental apparatus (the 'Satellite/Lunar Laser Ranging Characterization Facility', SCF) and created a new test procedure (the SCF-Test) to characterize and model the detailed thermal behavior and the optical performance of cube corner laser retroreflectors in space for industrial and scientific applications (Dell'Agnello et al., 2011 [13]). Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP) and the temperature distribution of the SLR retroreflector payload under thermal conditions produced with a close-match solar simulator. The apparatus includes infrared cameras for non-invasive thermometry, thermal control and real-time movement of the payload to experimentally simulate satellite orientation on orbit with respect to both solar illumination and laser interrogation beams. These unique capabilities provide experimental validation of the space segment for SLR and Lunar Laser Ranging

Analyses of surface coloration on TiO2 film irradiated with excimer laser

International Nuclear Information System (INIS)

Zheng, H.Y.; Qian, H.X.; Zhou, W.

2008-01-01

TiO 2 film of around 850 nm in thickness was deposited on a soda-lime glass by PVD sputtering and irradiated using one pulse of krypton-fluorine (KrF) excimer laser (wavelength of 248 nm and pulse duration of 25 ns) with varying fluence. The color of the irradiated area became darker with increasing laser fluence. Irradiated surfaces were characterized using optical microscopy, scanning electron microscopy, Raman spectroscopy and atomic force microscopy. Surface undergoes thermal annealing at low laser fluence of 400 and 590 mJ/cm 2 . Microcracks at medium laser fluence of 1000 mJ/cm 2 are attributed to surface melting and solidification. Hydrodynamic ablation is proposed to explain the formation of micropores and networks at higher laser fluence of 1100 and 1200 mJ/cm 2 . The darkening effect is explained in terms of trapping of light in the surface defects formed rather than anatase to rutile phase transformation as reported by others. Controlled darkening of TiO 2 film might be used for adjustable filters

Simultaneous production of spin-polarized ions/electrons based on two-photon ionization of laser-ablated metallic atoms

International Nuclear Information System (INIS)

Nakajima, Takashi; Yonekura, Nobuaki; Matsuo, Yukari; Kobayashi, Tohru; Fukuyama, Yoshimitsu

2003-01-01

We demonstrate the simultaneous production of spin-polarized ions/electrons using two-color, two-photon ionization of laser-ablated metallic atoms. Specifically, we have applied the developed technique to laser-ablated Sr atoms, and found that the electron-spin polarization of Sr + ions, and accordingly, the spin polarization of photoelectrons is 64%±9%, which is in good agreement with the theoretical prediction we have recently reported [T. Nakajima and N. Yonekura, J. Chem. Phys. 117, 2112 (2002)]. Our experimental results open up a simple way toward the construction of a spin-polarized dual ion/electron source

Laser-assisted fabrication of gold nanoparticle-composed structures embedded in borosilicate glass

Directory of Open Access Journals (Sweden)

Nikolay Nedyalkov

2017-11-01

Full Text Available We present results on laser-assisted formation of two- and three-dimensional structures comprised of gold nanoparticles in glass. The sample material was gold-ion-doped borosilicate glass prepared by conventional melt quenching. The nanoparticle growth technique consisted of two steps – laser-induced defect formation and annealing. The first step was realized by irradiating the glass by nanosecond and femtosecond laser pulses over a wide range of fluences and number of applied pulses. The irradiation by nanosecond laser pulses (emitted by a Nd:YAG laser system induced defect formation, expressed by brown coloration of the glass sample, only at a wavelength of 266 nm. At 355, 532 and 1064 nm, no coloration of the sample was observed. The femtosecond laser irradiation at 800 nm also induced defects, again observed as brown coloration. The absorbance spectra indicated that this coloration was related to the formation of oxygen deficiency defects. After annealing, the color of the irradiated areas changed to pink, with a corresponding well-defined peak in the absorbance spectrum. We relate this effect to the formation of gold nanoparticles with optical properties defined by plasmon excitation. Their presence was confirmed by high-resolution TEM analysis. No nanoparticle formation was observed in the samples irradiated by nanosecond pulses at 355, 532 and 1064 nm. The optical properties of the irradiated areas were found to depend on the laser processing parameters; these properties were studied based on Mie theory, which was also used to correlate the experimental optical spectra and the characteristics of the nanoparticles formed. We also discuss the influence of the processing conditions on the characteristics of the particles formed and the mechanism of their formation and demonstrate the fabrication of structures composed of nanoparticles inside the glass sample. This technique can be used for the preparation of 3D nanoparticle systems

Optimization of multi-color laser waveform for high-order harmonic generation

Science.gov (United States)

Jin, Cheng; Lin, C. D.

2016-09-01

With the development of laser technologies, multi-color light-field synthesis with complete amplitude and phase control would make it possible to generate arbitrary optical waveforms. A practical optimization algorithm is needed to generate such a waveform in order to control strong-field processes. We review some recent theoretical works of the optimization of amplitudes and phases of multi-color lasers to modify the single-atom high-order harmonic generation based on genetic algorithm. By choosing different fitness criteria, we demonstrate that: (i) harmonic yields can be enhanced by 10 to 100 times, (ii) harmonic cutoff energy can be substantially extended, (iii) specific harmonic orders can be selectively enhanced, and (iv) single attosecond pulses can be efficiently generated. The possibility of optimizing macroscopic conditions for the improved phase matching and low divergence of high harmonics is also discussed. The waveform control and optimization are expected to be new drivers for the next wave of breakthrough in the strong-field physics in the coming years. Project supported by the Fundamental Research Funds for the Central Universities of China (Grant No. 30916011207), Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy (Grant No. DE-FG02-86ER13491), and Air Force Office of Scientific Research, USA (Grant No. FA9550-14-1-0255).

Theoretical and experimental study of two-frequency solid-state lasers in the GHz to THz ranges. Opto-microwave applications waves

International Nuclear Information System (INIS)

Lai, N.D.

2003-07-01

We explored some new features of single- and dual-frequency solid-state lasers oscillating in continuous-wave or pulsed regimes. First, we have developed some techniques to optimise the characteristics of pulsed lasers. A weak modulation of the pump power made it possible to obtain a stable repetition rate with a relative stability of 10 -6 . The pulse duration was continuously controlled from ten nanoseconds to a few hundreds nanoseconds by three different methods: adjustment of the laser beam diameter in the absorber, adjustment of the pump beam diameter in the active medium, and, in particular, the use of forked eigenstates in a two-axis laser. Moreover, the forked eigenstates allows to increase the pulse energy by coherent addition of the pulses. A compact two-frequency Nd:YAG-Cr:YAG laser with a beat note frequency continuously adjustable up to 2,7 GHz was demonstrated. The two-frequency pulses are ideal sources to meet various needs of applications such as the Doppler lidar-radar. Moreover, we show that two-frequency pulses at 1,55 μm can be obtained by using a new c-cut Co:ASL saturable absorber in an Er-Yb:glass laser. These pulses are perfectly adapted to free-space detection systems requiring eye safety. The coherence time of the beat note in these lasers was also studied: it is limited by the pulse duration. A new technique of modulating the pump power of a solid-state laser at frequencies close to its relaxation oscillation frequency was studied and made it possible to generate a beat note coherence from pulse to pulse. Frequency conversion techniques using the nonlinear optical effects make it possible to obtain tunable two-frequency sources in the visible spectrum. Green and red two-frequency pulses were obtained by using different conversion techniques, intra-cavity or extra-cavity. A two-frequency THz source in the red spectrum was also obtained by doubling the frequencies of a two-frequency THz Er-Yb:glass laser using a mixed fan-out PPLN crystal

Design, Construction and Calibration of a Near-Infrared Four-Color Pyrometry System for Laser-Driven High Pressure Experiments

Science.gov (United States)

Ali, S. J.; Jeanloz, R.; Collins, G.; Spaulding, D. K.

2010-12-01

Current dynamic compression experiments, using both quasi-isentropic and shock-compression, allow access to pressure-temperature states both on and off the principle Hugoniot and over a wide range of conditions of direct relevance to planetary interiors. Such studies necessitate reliable temperature measurements below 4000-5000 K. Such relatively low temperature states are also of particular interest for materials such as methane and water that do not experience much heating under shock compression. In order to measure these temperatures as a function of time across the sample, a four-color, near-infrared pyrometry system is being developed for use at the Janus laser facility (LLNL) with channels at wavelengths of 932nm-1008nm, 1008nm-1108nm, 1108nm-1208nm, and 1208nm-1300nm. Each color band is fiber-coupled to an InGaAs PIN photodiode with a rise time of less than 60 ps, read using an 18 GHz oscilloscope in order to ensure time resolutions of under 200 ps. This will allow for high temporal resolution measurements of laser-driven shock compression experiments with total durations of 5-15 ns as well as correlation with simultaneous time-resolved velocity interferometry and visual-wavelength pyrometry. Calibration of the system is being accomplished using quartz targets, as the EOS for quartz is well known, along with a calibrated integrating sphere of known spectral radiance.

Testing the gravitational interaction in the field of the Earth via satellite laser ranging and the Laser Ranged Satellites Experiment (LARASE)

International Nuclear Information System (INIS)

Lucchesi, D M; Peron, R; Visco, M; Anselmo, L; Pardini, C; Bassan, M; Pucacco, G

2015-01-01

In this work, the Laser Ranged Satellites Experiment (LARASE) is presented. This is a research program that aims to perform new refined tests and measurements of gravitation in the field of the Earth in the weak field and slow motion (WFSM) limit of general relativity (GR). For this objective we use the free available data relative to geodetic passive satellite lasers tracked from a network of ground stations by means of the satellite laser ranging (SLR) technique. After a brief introduction to GR and its WFSM limit, which aims to contextualize the physical background of the tests and measurements that LARASE will carry out, we focus on the current limits of validation of GR and on current constraints on the alternative theories of gravity that have been obtained with the precise SLR measurements of the two LAGEOS satellites performed so far. Afterward, we present the scientific goals of LARASE in terms of upcoming measurements and tests of relativistic physics. Finally, we introduce our activities and we give a number of new results regarding the improvements to the modelling of both gravitational and non-gravitational perturbations to the orbit of the satellites. These activities are a needed prerequisite to improve the forthcoming new measurements of gravitation. An innovation with respect to the past is the specialization of the models to the LARES satellite, especially for what concerns the modelling of its spin evolution, the neutral drag perturbation and the impact of Earth's solid tides on the satellite orbit. (paper)

Improved atom number with a dual color magneto—optical trap

International Nuclear Information System (INIS)

Cao Qiang; Luo Xin-Yu; Gao Kui-Yi; Wang Xiao-Rui; Wang Ru-Quan; Chen Dong-Min

2012-01-01

We demonstrate a novel dual color magneto—optical trap (MOT), which uses two sets of overlapping laser beams to cool and trap 87 Rb atoms. The volume of cold cloud in the dual color MOT is strongly dependent on the frequency difference of the laser beams and can be significantly larger than that in the normal MOT with single frequency MOT beams. Our experiment shows that the dual color MOT has the same loading rate as the normal MOT, but much longer loading time, leading to threefold increase in the number of trapped atoms. This indicates that the larger number is caused by reduced light induced loss. The dual color MOT is very useful in experiments where both high vacuum level and large atom number are required, such as single chamber quantum memory and Bose—Einstein condensation (BEC) experiments. Compared to the popular dark spontaneous-force optical trap (dark SPOT) technique, our approach is technically simpler and more suitable to low power laser systems. (rapid communication)

Evaluation of the hydrogen peroxide and special colorant effects under irradiation by argon and diode laser on tooth-whitening in vitro; Avaliacao do efeito de corantes especiais e peroxido de hidrogenio irradiados por laser de argonio e laser de diodo no clareamento dental 'in vitro'

Energy Technology Data Exchange (ETDEWEB)

Gaspar, Jose Antonio

2003-07-01

The aim of this study is to determine if there is any interaction between special colorant found on bleaching agents that have 35 % of hydrogen peroxide on its composition, and argon or diode laser. The first part of the study was to characterize the extrinsic stain obtained through a staining solution containing products present on the day by day diet of the general population. Thirty-two inferior human extracted incisors, free of caries and without filling material were selected for the study. The laser devices employed were Argon laser (AccuCure 3000 TM - Lasermed), wave length 488 nm, with a 200 mW/cm{sup 2} for 30 seconds in continuos mode; and diode laser (L 808 Medical Laser - Lasering do Brasil), wave length 808 {+-} 10 nm, with 1,6 W/cm{sup 2} for 30 seconds in continuos mode. The application mode done by a scanning movement over the buccal surface. The bleaching agents used were: Opalescence Extra (OE) - Ultradent Products USA, hydrogen peroxide 35%, gel with Carotene to convert light into heat; Pola Office (PO) - SDI - USA single doses of hydrogen peroxide; Whiteness HP (WHP) - FGM - Brasil, hydrogen peroxide 35%; Opus White (OW) - Sharplan - Israel, hydrogen peroxide 35%. The temperature rise measurement was performed with a thermocouple model 120-202-AJ, Fenwal, inserted into the pulpar chamber. The bleaching material was applied on the tooth surface with 2 mm thickness and then the irradiation was perform. The thirty two teeth were randomized in four groups, two for each laser device. The obtain data demonstrated a superior performance of the Argon laser on tooth whitening and also better results concerning the temperature rise. The alteration on tooth coloration was verified through digital spectrophotometer (Shade-Eye EX - Shofu) and quantitative analyses showed statistical differences among the groups. The bleaching results for Argon laser combined with OE and WHP were superior for the other groups. The mean variation of the temperature rise

Field-glass range finder with a semiconductor laser

Science.gov (United States)

Iwanejko, Leszek; Jankiewicz, Zdzislaw; Jarocki, Roman; Marczak, Jan

1995-03-01

This paper presents the project of a laboratory model of a field-glasses range-finger. The optical transmitter of the device contains a commercial pulse semiconductor laser which generates IR wavelength around 905 nm. Some of the technical parameters of this device are: a maximum range of up to 3 km; an accuracy of +/- 5 m, divergence of a laser beam of 1 mrad; a repetition rate of 1 kHz. Dichroic elements of the receiver ensure a capability of an optimization of a field of view, without the worsening of luminance and size of an observation field.

Long-Range Coulomb Effect in Intense Laser-Driven Photoelectron Dynamics.

Science.gov (United States)

Quan, Wei; Hao, XiaoLei; Chen, YongJu; Yu, ShaoGang; Xu, SongPo; Wang, YanLan; Sun, RenPing; Lai, XuanYang; Wu, ChengYin; Gong, QiHuang; He, XianTu; Liu, XiaoJun; Chen, Jing

2016-06-03

In strong field atomic physics community, long-range Coulomb interaction has for a long time been overlooked and its significant role in intense laser-driven photoelectron dynamics eluded experimental observations. Here we report an experimental investigation of the effect of long-range Coulomb potential on the dynamics of near-zero-momentum photoelectrons produced in photo-ionization process of noble gas atoms in intense midinfrared laser pulses. By exploring the dependence of photoelectron distributions near zero momentum on laser intensity and wavelength, we unambiguously demonstrate that the long-range tail of the Coulomb potential (i.e., up to several hundreds atomic units) plays an important role in determining the photoelectron dynamics after the pulse ends.

The Color Glass Condensate and the Glasma: Two Lectures.

Energy Technology Data Exchange (ETDEWEB)

McLerran,L.

2007-08-29

These two lectures concern the Color Glass Condensate and the Glasma. These are forms of matter which might be studied in high energy hadronic collisions. The Color Glass Condensate is high energy density gluonic matter. It constitutes the part of a hadron wave function important for high energy processes. The Glasma is matter produced from the Color Glass Condensate in the first instants after a collision of two high energy hadrons. Both types of matter are associated with coherent fields. The Color Glass Condensate is static and related to a hadron wavefunction, where the Glasma is transient and evolves quickly after a collision. I present the properties of such matter, and some aspects of what is known of their properties.

Efficient and stable laser-driven white lighting

Directory of Open Access Journals (Sweden)

Kristin A. Denault

2013-07-01

Full Text Available Laser-based white lighting offers a viable option as an efficient and color-stable high-power solid-state white light source. We show that white light generation is possible using blue or near-UV laser diodes in combination with yellow-emitting cerium-substituted yttrium aluminum garnet (YAG:Ce or a mixture of red-, green-, and blue-emitting phosphors. A variety of correlated color temperatures (CCT are achieved, ranging from cool white light with a CCT of 4400 K using a blue laser diode to a warm white light with a CCT of 2700 K using a near-UV laser diode, with respective color rendering indices of 57 and 95. The luminous flux of these devices are measured to be 252 lm and 53 lm with luminous efficacies of 76 lm/W and 19 lm/W, respectively. An estimation of the maximum efficacy of a device comprising a blue laser diode in combination with YAG:Ce is calculated and the results are used to optimize the device.

Laser Meter of Atmospheric Inhomogeneity Properties in UV Spectral Range

Directory of Open Access Journals (Sweden)

S. E. Ivanov

2015-01-01

Full Text Available Development of laser systems designed to operate in conditions of the terrestrial atmosphere demands reliable information about the atmosphere condition. The aerosol lidars for operational monitoring of the atmosphere allow us to define remotely characteristics of atmospheric aerosol and cloudy formations in the atmosphere.Today the majority of aerosol lidars run in the visible range. However, in terms of safety (first of all to eyes also ultra-violet (UF range is of interest. A range of the wavelengths of the harmful effect on the eye retina is from 0.38 to 1.4 mμ. Laser radiation with the wavelengths less than 0.38 mμ and over 1.4 mμ influences the anterior ambient of an eye and is safer, than laser radiation with the wavelengths of 0.38 – 1.4 mμ.The paper describes a laser meter to measure characteristics of atmospheric inhomogeneity propertis in UF spectral range at the wavelength of 0.355 mμ.As a radiation source, the meter uses a semiconductor-pumped pulse solid-state Nd:YAG laser. As a receiving lens, Kassegren's scheme-implemented mirror lens with a socket to connect optical fibre is used in the laser meter. Radiation from the receiving lens is transported through the optical fibre to the optical block. The optical block provides spectral selection of useful signal and conversion of optical radiation into electric signal.To ensure a possibility for alignment of the optical axes of receiving lens and laser radiator the lens is set on the alignment platform that enables changing lens inclination and turn with respect to the laser.The software of the laser meter model is developed in the NI LabVIEW 2012 graphic programming environment.The paper gives the following examples: a typical laser echo signal, which is back scattered by the atmosphere and spatiotemporal distribution of variation coefficient of the volumetric factor of the back scattered atmosphere. Results of multi-day measurements show that an extent of the recorded aerosol

Two-dimensional materials for ultrafast lasers

International Nuclear Information System (INIS)

Wang Fengqiu

2017-01-01

As the fundamental optical properties and novel photophysics of graphene and related two-dimensional (2D) crystals are being extensively investigated and revealed, a range of potential applications in optical and optoelectronic devices have been proposed and demonstrated. Of the many possibilities, the use of 2D materials as broadband, cost-effective and versatile ultrafast optical switches (or saturable absorbers) for short-pulsed lasers constitutes a rapidly developing field with not only a good number of publications, but also a promising prospect for commercial exploitation. This review primarily focuses on the recent development of pulsed lasers based on several representative 2D materials. The comparative advantages of these materials are discussed, and challenges to practical exploitation, which represent good future directions of research, are laid out. (paper)

Evaluation of the hydrogen peroxide and special colorant effects under irradiation by argon and diode laser on tooth-whitening in vitro; Avaliacao do efeito de corantes especiais e peroxido de hidrogenio irradiados por laser de argonio e laser de diodo no clareamento dental 'in vitro'

Energy Technology Data Exchange (ETDEWEB)

Gaspar, Jose Antonio

2003-07-01

The aim of this study is to determine if there is any interaction between special colorant found on bleaching agents that have 35 % of hydrogen peroxide on its composition, and argon or diode laser. The first part of the study was to characterize the extrinsic stain obtained through a staining solution containing products present on the day by day diet of the general population. Thirty-two inferior human extracted incisors, free of caries and without filling material were selected for the study. The laser devices employed were Argon laser (AccuCure 3000 TM - Lasermed), wave length 488 nm, with a 200 mW/cm{sup 2} for 30 seconds in continuos mode; and diode laser (L 808 Medical Laser - Lasering do Brasil), wave length 808 {+-} 10 nm, with 1,6 W/cm{sup 2} for 30 seconds in continuos mode. The application mode done by a scanning movement over the buccal surface. The bleaching agents used were: Opalescence Extra (OE) - Ultradent Products USA, hydrogen peroxide 35%, gel with Carotene to convert light into heat; Pola Office (PO) - SDI - USA single doses of hydrogen peroxide; Whiteness HP (WHP) - FGM - Brasil, hydrogen peroxide 35%; Opus White (OW) - Sharplan - Israel, hydrogen peroxide 35%. The temperature rise measurement was performed with a thermocouple model 120-202-AJ, Fenwal, inserted into the pulpar chamber. The bleaching material was applied on the tooth surface with 2 mm thickness and then the irradiation was perform. The thirty two teeth were randomized in four groups, two for each laser device. The obtain data demonstrated a superior performance of the Argon laser on tooth whitening and also better results concerning the temperature rise. The alteration on tooth coloration was verified through digital spectrophotometer (Shade-Eye EX - Shofu) and quantitative analyses showed statistical differences among the groups. The bleaching results for Argon laser combined with OE and WHP were superior for the other groups. The mean variation of the temperature rise

Development of terahertz laser diagnostics for electron density measurements.

Science.gov (United States)

Kawahata, K; Akiyama, T; Tanaka, K; Nakayama, K; Okajima, S

2008-10-01

A two color laser interferometer using terahertz laser sources is under development for high performance operation on the large helical device and for future burning plasma experiments such as ITER. Through investigation of terahertz laser sources, we have achieved high power simultaneous oscillations at 57.2 and 47.6 microm of a CH(3)OD laser pumped by a cw 9R(8) CO(2) laser line. The laser wavelength around 50 microm is the optimum value for future fusion devices from the consideration of the beam refraction effect and signal-to-noise ratio for an expected phase shift due to plasma. In this article, recent progress of the terahertz laser diagnostics, especially in mechanical vibration compensation by using a two color laser operation and terahertz laser beam transmission through a dielectric waveguide, will be presented.

Comparison between two race/skin color classifications in relation to health-related outcomes in Brazil

Directory of Open Access Journals (Sweden)

Szwarcwald Celia L

2011-08-01

Full Text Available Abstract Background This paper aims to compare the classification of race/skin color based on the discrete categories used by the Demographic Census of the Brazilian Institute of Geography and Statistics (IBGE and a skin color scale with values ranging from 1 (lighter skin to 10 (darker skin, examining whether choosing one alternative or the other can influence measures of self-evaluation of health status, health care service utilization and discrimination in the health services. Methods This is a cross-sectional study based on data from the World Health Survey carried out in Brazil in 2003 with a sample of 5000 individuals older than 18 years. Similarities between the two classifications were evaluated by means of correspondence analysis. The effect of the two classifications on health outcomes was tested through logistic regression models for each sex, using age, educational level and ownership of consumer goods as covariables. Results Both measures of race/skin color represent the same race/skin color construct. The results show a tendency among Brazilians to classify their skin color in shades closer to the center of the color gradient. Women tend to classify their race/skin color as a little lighter than men in the skin color scale, an effect not observed when IBGE categories are used. With regard to health and health care utilization, race/skin color was not relevant in explaining any of them, regardless of the race/skin color classification. Lack of money and social class were the most prevalent reasons for discrimination in healthcare reported in the survey, suggesting that in Brazil the discussion about discrimination in the health care must not be restricted to racial discrimination and should also consider class-based discrimination. The study shows that the differences of the two classifications of race/skin color are small. However, the interval scale measure appeared to increase the freedom of choice of the respondent.

Nonablative Fractional Laser Resurfacing in Skin of Color: Evidence-based Review.

Science.gov (United States)

Kaushik, Shivani B; Alexis, Andrew F

2017-06-01

Background: Nonablative laser resurfacing represents one of the major advances in procedural dermatology over the past decade. However, its use in darker skin types is limited by safety concerns and a relative lack of available data. Aim: To provide evidence-based recommendations for the use of fractional lasers in darker skin types. Evidence review: A broad literature search of PubMed/Medline database was conducted in April 2016 using the term fractional lasers. A free text search of keywords including fractional resurfacing, nonablative lasers, skin type, skin of color, ethnic skin, Fitzpatrick skin type, Asian skin, African Americans, Afro-Caribbean, and Hispanics was also executed. An in-depth review of all the relevant articles fitting the authors' inclusion/exclusion criteria was performed. Thereafter, each study was assigned levels of evidence per the Modified Criteria by Oxford Center of Evidence Based Medicine. A recommendation was made for a specific treatment based on the presence of at least one Level 1 study or more than three Level 2 or 3 studies that had concordant results. Findings: The available evidence strongly suggests that fractional lasers are a favorable treatment option for a variety of dermatological diseases in Fitzpatrick skin phototypes IV to VI. Level 1 evidence was found for the use of fractional lasers for treating acne, striae and skin rejuvenation. Level 2 evidence was found for their use in acne scars, melasma, and surgical/traumatic scars. Conclusion: Fractional resurfacing is a safe and efficacious treatment option for various dermatological disorders in darker skin types; however, there is a paucity of high-quality studies involving skin types V and VI.

Genre Differences on Visual Perception of Color Range and Depth of Field

Directory of Open Access Journals (Sweden)

Luisa Ballesteros

2003-07-01

Full Text Available Visual perception is the result of the integration of various related factors of the observed object and its environment. In this study we evaluated the impact of tridimensional form on color perception and the angle from the horizontal plane of a set of similar objets on the depth of field perception between young men and women. A panel half magenta and half white placed at the end of a black box, folded either concaved or convexed to alter the chromatic effect perceived were used to determine tridimensional form on color perception. Four sets of identical sticks where the angle from the horizontal plane varied for each, were used to determine the effect of spatial distribution of depth of field perception. The parameters taking into account were age, genre, associated visual defects for each individual evaluated. Our results show that the tridimensional form alters color perception but the range of color perceived was larger for women whereas depending on the angle from the horizontal plane we found genre differences on the depth of field perception.

Range-Gated Laser Stroboscopic Imaging for Night Remote Surveillance

International Nuclear Information System (INIS)

Xin-Wei, Wang; Yan, Zhou; Song-Tao, Fan; Jun, He; Yu-Liang, Liu

2010-01-01

For night remote surveillance, we present a method, the range-gated laser stroboscopic imaging(RGLSI), which uses a new kind of time delay integration mode to integrate target signals so that night remote surveillance can be realized by a low-energy illuminated laser. The time delay integration in this method has no influence on the video frame rate. Compared with the traditional range-gated laser imaging, RGLSI can reduce scintillation and target speckle effects and significantly improve the image signal-to-noise ratio analyzed. Even under low light level and low visibility conditions, the RGLSI system can effectively work. In a preliminary experiment, we have detected and recognized a railway bridge one kilometer away under a visibility of six kilometers, when the effective illuminated energy is 29.5 μJ

Semiconductor lasers with a continuous tuning range above 100 nm in the nearest IR spectral region

Energy Technology Data Exchange (ETDEWEB)

Kostin, Yu O; Lobintsov, A A; Shramenko, M V [OOO ' Opton' , Moscow (Russian Federation); Ladugin, M A; Marmalyuk, A A [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation); Chamorovsky, A Yu [Superlum Ltd., Unit B3, Fota Point Enterprise Park, Carrigtwohill, Co Cork (Ireland); Yakubovich, S D [Moscow State Institute of Radio-Engineering, Electronics and Automation (Technical University), Moscow (Russian Federation)

2015-08-31

We have developed two new types of lasers based on quantum-confined semiconductor optical amplifiers with an acousto-optic tunable filter in an external fibre ring cavity. The lasers offer continuous wavelength tuning ranges from 780 to 885 and from 880 to 1010 nm, 20 mW of cw output power, and a tuning rate up to 10{sup 4} nm s{sup -1} at an instantaneous spectral linewidth less than 0.1 nm. (lasers)

HDR imaging and color constancy: two sides of the same coin?

Science.gov (United States)

McCann, John J.

2011-01-01

At first, we think that High Dynamic Range (HDR) imaging is a technique for improved recordings of scene radiances. Many of us think that human color constancy is a variation of a camera's automatic white balance algorithm. However, on closer inspection, glare limits the range of light we can detect in cameras and on retinas. All scene regions below middle gray are influenced, more or less, by the glare from the bright scene segments. Instead of accurate radiance reproduction, HDR imaging works well because it preserves the details in the scene's spatial contrast. Similarly, on closer inspection, human color constancy depends on spatial comparisons that synthesize appearances from all the scene segments. Can spatial image processing play similar principle roles in both HDR imaging and color constancy?

Two-channel Hyperspectral LiDAR with a Supercontinuum Laser Source

Directory of Open Access Journals (Sweden)

Ruizhi Chen

2010-07-01

Full Text Available Recent advances in nonlinear fiber optics and compact pulsed lasers have resulted in creation of broadband directional light sources. These supercontinuum laser sources produce directional broadband light using cascaded nonlinear optical interactions in an optical fibre framework. This system is used to simultaneously measure distance and reflectance to demonstrate a technique capable of distinguishing between a vegetation target and inorganic material using the Normalized Difference Vegetation Index (NDVI parameters, while the range can be obtained from the waveform of the echoes. A two-channel, spectral range-finding system based on a supercontinuum laser source was used to determine its potential application of distinguishing the NDVI for Norway spruce, a coniferous tree, and its three-dimensional parameters at 600 nm and 800 nm. A prototype system was built using commercial components.

Precision metrology of NSTX surfaces using coherent laser radar ranging

International Nuclear Information System (INIS)

Kugel, H.W.; Loesser, D.; Roquemore, A. L.; Menon, M. M.; Barry, R. E.

2000-01-01

A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 microm laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of < 100microm at distances of up to 22 meters. A description is given of the geometry and procedure for measuring NSTX interior and exterior surfaces during open vessel conditions, and the results of measurements are elaborated

Measuring the relativistic perigee advance with satellite laser ranging

International Nuclear Information System (INIS)

Iorio, Lorenzo; Ciufolini, Ignazio; Pavlis, Erricos C

2002-01-01

The pericentric advance of a test body by a central mass is one of the classical tests of general relativity. Today, this effect is measured with radar ranging by the perihelion shift of Mercury and other planets in the gravitational field of the Sun, with a relative accuracy of the order of 10 -2 -10 -3 . In this paper, we explore the possibility of a measurement of the pericentric advance in the gravitational field of Earth by analysing the laser-ranged data of some orbiting, or proposed, laser-ranged geodetic satellites. Such a measurement of the perigee advance would place limits on hypothetical, very weak, Yukawa-type components of the gravitational interaction with a finite range of the order of 10 4 km. Thus, we show that, at the present level of knowledge of the orbital perturbations, the relative accuracy, achievable with suitably combined orbital elements of LAGEOS and LAGEOS II, is of the order of 10 -3 . With the corresponding measured value of (2 + 2γ - β)/3, by using η = 4β - γ - 3 from lunar laser ranging, we could get an estimate of the PPN parameters γ and β with an accuracy of the order of 10 -2 -10 -3 . Nevertheless, these accuracies would be substantially improved in the near future with the new Earth gravity field models by the CHAMP and GRACE missions. The use of the perigee of LARES (LAser RElativity Satellite), with a suitable combination of orbital residuals including also the node and the perigee of LAGEOS II, would also further improve the accuracy of the proposed measurement

Spinor Slow Light and Two-Color Qubits

Science.gov (United States)

Yu, Ite; Lee, Meng-Jung; Ruseckas, Julius; Lee, Chin-Yuan; Kudriasov, Viaceslav; Chang, Kao-Fang; Cho, Hung-Wen; Juzeliunas, Gediminas; Yu, Ite A.

2015-05-01

We report the first experimental demonstration of two-component or spinor slow light (SSL) using a double tripod (DT) atom-light coupling scheme. The scheme involves three atomic ground states coupled to two excited states by six light fields. The oscillation due to the interaction between the two components was observed. SSL can be used to achieve high conversion efficiencies in the sum frequency generation and is a better method than the widely-used double- Λ scheme. On the basis of the stored light, our data showed that the DT scheme behaves like the two outcomes of an interferometer enabling precision measurements of frequency detuning. Furthermore, the single-photon SSL can be considered as the qubit with the superposition state of two frequency modes or, simply, as the two-color qubit. We experimentally demonstrated a possible application of the DT scheme as quantum memory/rotator for the two-color qubit. This work opens up a new direction in the EIT/slow light research. yu@phys.nthu.edu.tw

Michelson mode selector for spectral range stabilization in a self-sweeping fiber laser.

Science.gov (United States)

Tkachenko, A Yu; Vladimirskaya, A D; Lobach, I A; Kablukov, S I

2018-04-01

We report on spectral range stabilization in a self-sweeping laser by adding a narrowband fiber Bragg grating (FBG) to the output mirror in the Michelson configuration. The effects of FBG reflectivity and optical path difference in the Michelson interferometer on the laser spectral dynamics are investigated. Optimization of the interferometer allows us to demonstrate broadband (over 16 nm) self-sweeping operation and reduction of the start and stop wavelength fluctuations by two orders and one order of magnitude (∼100 and 15 times) for start and stop bounds, respectively (down to several picometers). The proposed approaches significantly improve quality of the spectral dynamics and facilitate application of the self-sweeping lasers.

P1-9: Relationship between Color Shifts in Land's Two-Color Method and Higher- and Lower-Level Visual Information

Directory of Open Access Journals (Sweden)

Saki Iwaida

2012-10-01

Full Text Available Land's two-color method gives rise to apparent full-color perception, even though only two colors (e.g., red and gray are used. Previous studies indicate that chromatic adaptation, color memory, and inductive effects contribute to the shifts of color perception from real to illusory colors (e.g., Kuriki, 2006 Vision Research 46 3055–3066. This paper investigates the relationship between the color shifts induced by Land images and the skewness of the luminance histogram. In Experiment 1, several Land images are created based on a yellow ball, and the magnitude of the color shifts of the images are measured. The results of Experiment 1 show a significant correlation between the magnitude of the color shifts and skewness, suggesting that skewness is critical for the color shifts. In Experiment 2, we test the hypothesis that color shifts depends on just skewness; the color shifts should be invariant even if the Land images are scrambled. However, the results of Experiment 2 demonstrate that scrambled Land images exhibit less intense color shifts, suggesting that color shifts are determined by the object's overall shape or surface gloss, not just skewness. Taken together, we conclude that both low-level visual processes, such as those associated with luminance histogram skew, and high-level cognitive functions, such as object interpretation or understanding of surface gloss, are involved in the color shift of Land images.

Multi-color imaging of magnetic Co/Pt heterostructures

Directory of Open Access Journals (Sweden)

Felix Willems

2017-01-01

Full Text Available We present an element specific and spatially resolved view of magnetic domains in Co/Pt heterostructures in the extreme ultraviolet spectral range. Resonant small-angle scattering and coherent imaging with Fourier-transform holography reveal nanoscale magnetic domain networks via magnetic dichroism of Co at the M2,3 edges as well as via strong dichroic signals at the O2,3 and N6,7 edges of Pt. We demonstrate for the first time simultaneous, two-color coherent imaging at a free-electron laser facility paving the way for a direct real space access to ultrafast magnetization dynamics in complex multicomponent material systems.

Color dependence with horizontal-viewing angle and colorimetric characterization of two displays using different backlighting

Science.gov (United States)

Castro, José J.; Pozo, Antonio M.; Rubiño, Manuel

2013-11-01

In this work we studied the color dependence with a horizontal-viewing angle and colorimetric characterization of two liquid-crystal displays (LCD) using two different backlighting: Cold Cathode Fluorescent Lamps (CCFLs) and light-emitting diodes (LEDs). The LCDs studied had identical resolution, size, and technology (TFT - thin film transistor). The colorimetric measurements were made with the spectroradiometer SpectraScan PR-650 following the procedure recommended in the European guideline EN 61747-6. For each display, we measured at the centre of the screen the chromaticity coordinates at horizontal viewing angles of 0, 20, 40, 60 and 80 degrees for the achromatic (A), red (R), green (G) and blue (B) channels. Results showed a greater color-gamut area for the display with LED backlight, compared with the CCFL backlight, showing a greater range of colors perceptible by human vision. This color-gamut area diminished with viewing angle for both displays. Higher differences between trends for viewing angles were observed in the LED-backlight, especially for the R- and G-channels, demonstrating a higher variability of the chromaticity coordinates with viewing angle. The best additivity was reached by the LED-backlight display (a lower error percentage). LED-backlight display provided better color performance of visualization.

Wide range optofluidically tunable multimode interference fiber laser

International Nuclear Information System (INIS)

Antonio-Lopez, J E; LiKamWa, P; Sanchez-Mondragon, J J; May-Arrioja, D A

2014-01-01

An optofluidically tunable fiber laser based on multimode interference (MMI) effects with a wide tuning range is proposed and demonstrated. The tunable mechanism is based on an MMI fiber filter fabricated using a special fiber known as no-core fiber, which is a multimode fiber (MMF) without cladding. Therefore, when the MMI filter is covered by liquid the optical properties of the no-core fiber are modified, which allow us to tune the peak wavelength response of the MMI filter. Rather than applying the liquid on the entire no-core fiber, we change the liquid level along the no-core fiber, which provides a highly linear tuning response. In addition, by selecting the adequate refractive index of the liquid we can also choose the tuning range. We demonstrate the versatility of the optofluidically tunable MMI filter by wavelength tuning two different gain media, erbium doped fiber and a semiconductor optical amplifier, achieving tuning ranges of 55 and 90 nm respectively. In both cases, we achieve side-mode suppression ratios (SMSR) better than 50 dBm with output power variations of less than 0.76 dBm over the whole tuning range. (paper)

Applying dual-laser spot positions measurement technology on a two-dimensional tracking measurement system

International Nuclear Information System (INIS)

Lee, Hau-Wei; Chen, Chieh-Li

2009-01-01

This paper presents a two-dimensional tracking measurement system with a tracking module, which consists of two stepping motors, two laser diodes and a four separated active areas segmented position sensitive detector (PSD). The PSD was placed on a two-dimensional moving stage and used as a tracking target. The two laser diodes in the tracking module were directly rotated to keep the laser spots on the origin of the PSD. The two-dimensional position of the target PSD on the moving stage is determined from the distance between the two motors and the tracking angles of the two laser diodes, which are rotated by the two stepping motors, respectively. In order to separate the four positional values of the two laser spots on one PSD, the laser diodes were modulated by two distinct frequencies. Multiple-laser spot position measurement technology was used to separate the four positional values of the two laser spots on the PSD. The experimental results show that the steady-state voltage shift rate is about 0.2% and dynamic cross-talk rate is smaller than 2% when the two laser spots are projected on one PSD at the same time. The measurement errors of the x and y axial positions of the two-dimensional tracking system were less than 1% in the measuring range of 20 mm. The results demonstrate that multiple-laser spot position measurement technology can be employed in a two-dimensional tracking measurement system

Particle range in a laser-plasma generated soft X-ray chamber

International Nuclear Information System (INIS)

Bollanti, S.; Letardi, T.

1999-01-01

Some analytical forms are deduced for calculating the flight range of a spherical particle ejected from the laser plasma target and retarded by gas resistance. it is shown that the gas pressure influence on viscosity can not be neglected when are estimated the expansion ranges fro debris of various sizes in a helium gas-buffered, laser produced plasma chamber [it

A novel hybrid color image encryption algorithm using two complex chaotic systems

Science.gov (United States)

Wang, Leyuan; Song, Hongjun; Liu, Ping

2016-02-01

Based on complex Chen and complex Lorenz systems, a novel color image encryption algorithm is proposed. The larger chaotic ranges and more complex behaviors of complex chaotic systems, which compared with real chaotic systems could additionally enhance the security and enlarge key space of color image encryption. The encryption algorithm is comprised of three step processes. In the permutation process, the pixels of plain image are scrambled via two-dimensional and one-dimensional permutation processes among RGB channels individually. In the diffusion process, the exclusive-or (XOR for short) operation is employed to conceal pixels information. Finally, the mixing RGB channels are used to achieve a multilevel encryption. The security analysis and experimental simulations demonstrate that the proposed algorithm is large enough to resist the brute-force attack and has excellent encryption performance.

Accurate color measurement methods for medical displays.

Science.gov (United States)

Saha, Anindita; Kelley, Edward F; Badano, Aldo

2010-01-01

The necessity for standard instrumentation and measurements of color that are repeatable and reproducible is the major motivation behind this work. Currently, different instrumentation and methods can yield very different results when measuring the same feature such as color uniformity or color difference. As color increasingly comes into play in medical imaging diagnostics, display color will have to be quantified in order to assess whether the display should be used for imaging purposes. The authors report on the characterization of three novel probes for measuring display color with minimal contamination from screen areas outside the measurement spot or from off-normal emissions. They compare three probe designs: A modified small-spot luminance probe and two conic probe designs based on black frusta. To compare the three color probe designs, spectral and luminance measurements were taken with specialized instrumentation to determine the luminance changes and color separation abilities of the probes. The probes were characterized with a scanning slit method, veiling glare, and a moving laser and LED arrangement. The scanning slit measurement was done using a black slit plate over a white line on an LCD monitor. The luminance was measured in 1 mm increments from the center of the slit to +/- 15 mm above and below the slit at different distances between the probe and the slit. The veiling glare setup consisted of measurements of the luminance of a black spot pattern with a white disk of radius of 100 mm as the black spot increases in 1 mm radius increments. The moving LED and laser method consisted of a red and green light orthogonal to the probe tip for the light to directly shine into the probe. The green light source was moved away from the red source in 1 cm increments to measure color stray-light contamination at different probe distances. The results of the color testing using the LED and laser methods suggest a better performance of one of the frusta probes

A two-level model of rise time in quantum cascade laser materials applied to 5 micron, 9 micron and terahertz-range wavelengths

International Nuclear Information System (INIS)

Webb, J F; Yong, K S C; Haldar, M K

2014-01-01

An equivalent circuit simulation of a two-level rate equation model for quantum cascade laser (QCL) materials is used to study the turn on delay and rise time for three QCLs with 5 micron, 9 micron and terahertz-range wavelengths. In order to do this it is necessary that the model can deal with large signal responses and not be restricted to small signal responses; the model used here is capable of this. The effect of varying some of the characteristic times in the model is also investigated. The comparison of the terahertz wave QCL with the others is particularly important given the increased interest in terahertz sources which have a large range of important applications, such as in medical imaging

MOONLIGHT: A NEW LUNAR LASER RANGING RETROREFLECTOR INSTRUMENT

Directory of Open Access Journals (Sweden)

M. Garattini

2013-12-01

Full Text Available Since 1969 Lunar Laser Ranging (LLR to the Apollo Cube Corner Reflector (CCR arrays has supplied several significant tests of gravity: Geodetic Precession, the Strong and Weak Equivalence Principle (SEP, WEP, the Parametrized Post Newtonian (PPN parameter , the time change of the Gravitational constant (G, 1/r2 deviations and new gravitational theories beyond General Relativity (GR, like the unified braneworld theory (G. Dvali et al., 2003. Now a new generation of LLR can do better using evolved laser retroreflectors, developed from tight collaboration between my institution, INFN–LNF (Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali di Frascati, and Douglas Currie (University of Maryland, USA, one of the fathers of LLR. The new lunar CCR is developing and characterizing at the “Satellite/Lunar laser ranging Characterization Facility” (SCF, in Frascati, performing our new industry standard space test procedure, the “SCF-Test”; this work contains the experimental results of the SCF-Test applied to the new lunar CCR, and all the new payload developments, including the future SCF tests. The International Lunar Network (ILN research project considers our new retroreflector as one of the possible “Core Instruments”

Two-out-of-two color matching based visual cryptography schemes.

Science.gov (United States)

Machizaud, Jacques; Fournel, Thierry

2012-09-24

Visual cryptography which consists in sharing a secret message between transparencies has been extended to color prints. In this paper, we propose a new visual cryptography scheme based on color matching. The stacked printed media reveal a uniformly colored message decoded by the human visual system. In contrast with the previous color visual cryptography schemes, the proposed one enables to share images without pixel expansion and to detect a forgery as the color of the message is kept secret. In order to correctly print the colors on the media and to increase the security of the scheme, we use spectral models developed for color reproduction describing printed colors from an optical point of view.

Frequency-modulated laser ranging sensor with closed-loop control

Science.gov (United States)

Müller, Fabian M.; Böttger, Gunnar; Janeczka, Christian; Arndt-Staufenbiel, Norbert; Schröder, Henning; Schneider-Ramelow, Martin

2018-02-01

Advances in autonomous driving and robotics are creating high demand for inexpensive and mass-producible distance sensors. A laser ranging system (Lidar), based on the frequency-modulated continuous-wave (FMCW) method is built in this work. The benefits of an FMCW Lidar system are the low-cost components and the performance in comparison to conventional time-of-flight Lidar systems. The basic system consists of a DFB laser diode (λ= 1308 nm) and an asymmetric fiber-coupled Mach-Zehnder interferometer with a fixed delay line in one arm. Linear tuning of the laser optical frequency via injection current modulation creates a beat signal at the interferometer output. The frequency of the beat signal is proportional to the optical path difference in the interferometer. Since the laser frequency-to-current response is non-linear, a closed-loop feed-back system is designed to improve the tuning linearity, and consequently the measurement resolution. For fast active control, an embedded system with FPGA is used, resulting in a nearly linear frequency tuning, realizing a narrow peak in the Fourier spectrum of the beat signal. For free-space measurements, a setup with two distinct interferometers is built. The fully fiber-coupled Mach-Zehnder reference interferometer is part of the feed-back loop system, while the other - a Michelson interferometer - has a free-space arm with collimator lens and reflective target. A resolution of 2:0 mm for a 560 mm distance is achieved. The results for varying target distances show high consistency and a linear relation to the measured beat-frequency.

Temporal enhancement of two-dimensional color doppler echocardiography

Science.gov (United States)

Terentjev, Alexey B.; Settlemier, Scott H.; Perrin, Douglas P.; del Nido, Pedro J.; Shturts, Igor V.; Vasilyev, Nikolay V.

2016-03-01

Two-dimensional color Doppler echocardiography is widely used for assessing blood flow inside the heart and blood vessels. Currently, frame acquisition time for this method varies from tens to hundreds of milliseconds, depending on Doppler sector parameters. This leads to low frame rates of resulting video sequences equal to tens of Hz, which is insufficient for some diagnostic purposes, especially in pediatrics. In this paper, we present a new approach for reconstruction of 2D color Doppler cardiac images, which results in the frame rate being increased to hundreds of Hz. This approach relies on a modified method of frame reordering originally applied to real-time 3D echocardiography. There are no previous publications describing application of this method to 2D Color Doppler data. The approach has been tested on several in-vivo cardiac 2D color Doppler datasets with approximate duration of 30 sec and native frame rate of 15 Hz. The resulting image sequences had equivalent frame rates to 500Hz.

Bio-inspired micro-nano structured surface with structural color and anisotropic wettability on Cu substrate

International Nuclear Information System (INIS)

Liu, Yan; Li, Shuyi; Niu, Shichao; Cao, Xiaowen; Han, Zhiwu; Ren, Luquan

2016-01-01

Highlights: • We have prepared a biomimetic hydrophobic surface on copper substrate by one-step femtosecond laser technique. • The hydrophobicity mechanism relies on morphology and chemical component on surface. • The hydrophobic surfaces exhibit different structural colors and a anisotropic wettability. - Abstract: Inspired by the unique creatures in the nature, the femtosecond laser technology has been usually used to fabricate the periodic microstructures due to its advantages of rapidness, simplicity, ease of large-area fabrication, and simultaneously offering dual micro/nano-scale structures simply via one-step process for a wide variety of materials. By changing the experimental conditions, multi-functional surfaces which possess superhydrophobicity and structural colors could be achieved on copper substrate. In addition, the apparent contact angle can reach 144.3° without any further modification, which also exhibits the anisotropic wettability. Moreover, it can be inferred that higher laser fluence can lead to a larger CA within a certain range. At the same time, due to the change of laser processing parameters, the obtained surfaces present different structural colors. This study may expand the applications of bio-inspired functional materials because multiple colors and hydrophobicity are both important features in the real life and industrial applications, such as display, decoration, and anti-counterfeiting technology etc.

Bio-inspired micro-nano structured surface with structural color and anisotropic wettability on Cu substrate

Energy Technology Data Exchange (ETDEWEB)

Liu, Yan [Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022 (China); State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun 130022 (China); Li, Shuyi; Niu, Shichao [Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022 (China); Cao, Xiaowen [Key Laboratory on Integrated Optoelectronics College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Han, Zhiwu, E-mail: zwhan@jlu.edu.cn [Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022 (China); Ren, Luquan [Key Laboratory of Bionic Engineering (Ministry of Education), Jilin University, Changchun 130022 (China)

2016-08-30

Highlights: • We have prepared a biomimetic hydrophobic surface on copper substrate by one-step femtosecond laser technique. • The hydrophobicity mechanism relies on morphology and chemical component on surface. • The hydrophobic surfaces exhibit different structural colors and a anisotropic wettability. - Abstract: Inspired by the unique creatures in the nature, the femtosecond laser technology has been usually used to fabricate the periodic microstructures due to its advantages of rapidness, simplicity, ease of large-area fabrication, and simultaneously offering dual micro/nano-scale structures simply via one-step process for a wide variety of materials. By changing the experimental conditions, multi-functional surfaces which possess superhydrophobicity and structural colors could be achieved on copper substrate. In addition, the apparent contact angle can reach 144.3° without any further modification, which also exhibits the anisotropic wettability. Moreover, it can be inferred that higher laser fluence can lead to a larger CA within a certain range. At the same time, due to the change of laser processing parameters, the obtained surfaces present different structural colors. This study may expand the applications of bio-inspired functional materials because multiple colors and hydrophobicity are both important features in the real life and industrial applications, such as display, decoration, and anti-counterfeiting technology etc.

University of Hawaii Lure Observatory. [lunar laser ranging system construction

Science.gov (United States)

Carter, W. E.; Williams, J. D.

1973-01-01

The University of Hawaii's Institute for Astronomy is currently constructing a lunar laser ranging observatory at the 3050-meter summit of Mt. Haleakala, Hawaii. The Nd YAG laser system to be employed provides three pulses per second, each pulse being approximately 200 picoseconds in duration. The energy contained in one pulse at 5320 A lies in the range from 250 to 350 millijoules. Details of observatory construction are provided together with transmitter design data and information concerning the lunastat, the feed telescope, the relative pointing system, the receiver, and the event timer system.

Method for numerical simulation of two-term exponentially correlated colored noise

International Nuclear Information System (INIS)

Yilmaz, B.; Ayik, S.; Abe, Y.; Gokalp, A.; Yilmaz, O.

2006-01-01

A method for numerical simulation of two-term exponentially correlated colored noise is proposed. The method is an extension of traditional method for one-term exponentially correlated colored noise. The validity of the algorithm is tested by comparing numerical simulations with analytical results in two physical applications

Quantum-cascade lasers in the 7-8 μm spectral range with full top metallization

Science.gov (United States)

Kurochkin, A. S.; Babichev, A. V.; Denisov, D. V.; Karachinsky, L. Ya; Novikov, I. I.; Sofronov, A. N.; Firsov, D. A.; Vorobjev, L. E.; Bousseksou, A.; Egorov, A. Yu

2018-03-01

The paper demonstrates the generation of multistage quantum-cascade lasers (QCL) in the 7-8 μm spectral range in the pulse generation mode. The active region structure we used is based on a two-phonon resonance scheme. The QCL heterostructure based on a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid alloys was grown by molecular beam epitaxy and includes 50 identical stages. A waveguide geometry with top cladding with full top metallization (surface- plasmon quantum-cascade lasers) has been used. The developed QCLs have demonstrated multimodal generation in the 7-8 μm spectral range in the pulse mode in the 78-250 K temperature range. The threshold current density for a 1.6 mm long laser and a 20 μm ridge width amounted to ˜ 2.8 kA/cm2 at a temperature of 78 К. A temperature increase to 250 K causes a long-wave shift of the wavelength from 7.6 to 7.9 μm and a jth increase to 5.0 kA/cm2.

Diode-pumped two micron solid-state lasers

International Nuclear Information System (INIS)

Elder, I.F.

1997-01-01

This thesis presents an investigation of diode-pumped two micron solid-state lasers, concentrating on a comparison of the cw room temperature operation of Tm:YAP, Tm,Ho:YAP and Tm,Ho:YLF. Dopant concentrations in YAP were 4.2% thulium and 0.28% holmium; in YLF they were 6% thulium and 0.4% holmium. Thermal modelling was carried out in order to provide an insight into the thermal lensing and population distributions in these materials. Laser operation was achieved utilising an end-pumping geometry with a simple two mirror standing wave resonator. The pump source for these experiments was a 3 W laser diode. Maximum output power was achieved with Tm:YAP, generating 730 mW of laser output, representing 42% conversion efficiency in terms of absorbed pump power. Upper bounds on the conversion efficiency of Tm,Ho:YAP and Tm,Ho:YLF laser crystal of 14% and 30% were obtained, with corresponding output powers of 270 and 660 mW. In all three cases, the output beam was TEM 00 in nature. Visible upconversion fluorescence bands in the green and red were identified in Tm,Ho:YAP and Tm,Ho:YLF, with additional blue emission from the latter, all assigned to transitions on holmium. The principal upconversion mechanisms in these materials all involved the holmium first excited state. Upconversion in Tm:YAP was negligible. The spectral output of Tm:YAP consisted of a comb of lines in the range 1.965 to 2.020 μm. For both the double-doped crystals, the laser output was multilongitudinal mode on a single transition, wavelength 2.120 μm in YAP, 2.065 μm in YLF. In the time domain the output of Tm:YAP was dominated by large amplitude spiking, unlike both of the double-doped laser crystals. The long lifetime of the thulium upper laser level (4.4 ms) provided very weak damping of the spiking. Excitation sharing between thulium and holmium, with a measured characteristic lifetime in YAP of 11.9 μs and YLF of 14.8 μs, provided strong damping of any spiking behaviour. (author)

Application of the UV laser printing technique to soft gelatin capsules containing titanium dioxide in the shells.

Science.gov (United States)

Hosokawa, Akihiro; Kato, Yoshiteru

2012-03-01

The purpose of this study was to examine application of ultraviolet (UV) laser irradiation to printing soft gelatin capsules containing titanium dioxide (TiO(2)) in the shells and to study effect of UV laser power on the color strength of printing on the soft gelatin capsules. Size 6 Oval type soft gelatin capsules of which shells contained 0.685% TiO(2) and 0.005% ferric dioxide were used in this study. The capsules were irradiated pulsed UV laser at a wavelength 355 nm. The color strength of the printed capsules was determined by a spectrophotometer as total color difference (dE). The soft gelatin capsules which contained TiO(2) in the shells could be printed gray by the laser. Many black particles, which were associated with the printing, were formed at the colored parts of the shells. It was found that there were two inflection points in relationship between output laser energy of a pulse and dE. Below the lower point, the capsules were not printed. From the lower point to the upper point, the capsules were printed gray and total color difference of the printing increased linearly in proportion with the output laser energy. Beyond the upper point, total color difference showed saturation because of micro-bubbles formation at the laser irradiated spot. Soft gelatin capsules containing TiO(2) in the shells could be performed stable printing using the UV laser printing technique. Color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

Advanced Laser Architecture for Two-Step Laser Tandem Mass Spectrometer

Science.gov (United States)

Fahey, Molly E.; Li, Steven X.; Yu, Anthony W.; Getty, Stephanie A.

2016-01-01

Future astrobiology missions will focus on planets with significant astrochemical or potential astrobiological features, such as small, primitive bodies and the icy moons of the outer planets that may host diverse organic compounds. These missions require advanced instrument techniques to fully and unambiguously characterize the composition of surface and dust materials. Laser desorptionionization mass spectrometry (LDMS) is an emerging instrument technology for in situ mass analysis of non-volatile sample composition. A recent Goddard LDMS advancement is the two-step laser tandem mass spectrometer (L2MS) instrument to address the need for future flight instrumentation to deconvolve complex organic signatures. The L2MS prototype uses a resonance enhanced multi-photon laser ionization mechanism to selectively detect aromatic species from a more complex sample. By neglecting the aliphatic and inorganic mineral signatures in the two-step mass spectrum, the L2MS approach can provide both mass assignments and clues to structural information for an in situ investigation of non-volatile sample composition. In this paper we will describe our development effort on a new laser architecture that is based on the previously flown Lunar Orbiter Laser Altimeter (LOLA) laser transmitter for the L2MS instrument. The laser provides two discrete midinfrared wavelengths (2.8 m and 3.4 m) using monolithic optical parametric oscillators and ultraviolet (UV) wavelength (266 nm) on a single laser bench with a straightforward development path toward flight readiness.

Two-colorable graph states with maximal Schmidt measure

International Nuclear Information System (INIS)

Severini, Simone

2006-01-01

The Schmidt measure was introduced by Eisert and Briegel for quantifying the degree of entanglement of multipartite quantum systems [J. Eisert, H.-J. Briegel, Phys. Rev. A 64 (2001) 22306]. For two-colorable graph states, the Schmidt measure is related to the spectrum of the associated graph. We observe that almost all two-colorable graph states have maximal Schmidt measure and we construct specific examples. By making appeal to a result of Ehrenfeucht et al. [A. Ehrenfeucht, T. Harju, G. Rozenberg, Discrete Math. 278 (2004) 45], we point out that the graph operations called local complementation and switching form a transitive group acting on the set of all graph states of a given dimension

Topological color codes and two-body quantum lattice Hamiltonians

Science.gov (United States)

Kargarian, M.; Bombin, H.; Martin-Delgado, M. A.

2010-02-01

Topological color codes are among the stabilizer codes with remarkable properties from the quantum information perspective. In this paper, we construct a lattice, the so-called ruby lattice, with coordination number 4 governed by a two-body Hamiltonian. In a particular regime of coupling constants, in a strong coupling limit, degenerate perturbation theory implies that the low-energy spectrum of the model can be described by a many-body effective Hamiltonian, which encodes the color code as its ground state subspace. Ground state subspace corresponds to a vortex-free sector. The gauge symmetry Z2×Z2 of the color code could already be realized by identifying three distinct plaquette operators on the ruby lattice. All plaquette operators commute with each other and with the Hamiltonian being integrals of motion. Plaquettes are extended to closed strings or string-net structures. Non-contractible closed strings winding the space commute with Hamiltonian but not always with each other. This gives rise to exact topological degeneracy of the model. A connection to 2-colexes can be established via the coloring of the strings. We discuss it at the non-perturbative level. The particular structure of the two-body Hamiltonian provides a fruitful interpretation in terms of mapping onto bosons coupled to effective spins. We show that high-energy excitations of the model have fermionic statistics. They form three families of high-energy excitations each of one color. Furthermore, we show that they belong to a particular family of topological charges. The emergence of invisible charges is related to the string-net structure of the model. The emerging fermions are coupled to nontrivial gauge fields. We show that for particular 2-colexes, the fermions can see the background fluxes in the ground state. Also, we use the Jordan-Wigner transformation in order to test the integrability of the model via introducing Majorana fermions. The four-valent structure of the lattice prevents the

Comparative study of the action of two different types of bleaching agents activated by two different types of irradiation fonts: xenon plasma arc lamp and 960 nm diode laser; Avaliacao da cor e estudo comparativo da acao de dois tipos diferentes de agentes clareadores ativados pelo laser de diodo e lampada xenonio plasmatica, na superficie do esmalte

Energy Technology Data Exchange (ETDEWEB)

Walverde, Debora Ayala

2001-07-01

This in vitro study compares two different types of tooth bleaching agents stimulated with two different irradiation fonts. These fonts accelerate the action of the bleaching agents upon the enamel surface by heating up the materials. We used the xenon plasma arc lamp and a 960 nm fiber-coupled diode laser to irradiate the two materials containing 35% of hydrogen peroxide (Opus White and Opalescence extra). The color of the teeth was measured with a spectrophotometer using the CIELAB color system that gives the numeric values of L{sup *}a{sup *}b{sup *}. (author)

The biological basis of a universal constraint on color naming: cone contrasts and the two-way categorization of colors.

Science.gov (United States)

Xiao, Youping; Kavanau, Christopher; Bertin, Lauren; Kaplan, Ehud

2011-01-01

Many studies have provided evidence for the existence of universal constraints on color categorization or naming in various languages, but the biological basis of these constraints is unknown. A recent study of the pattern of color categorization across numerous languages has suggested that these patterns tend to avoid straddling a region in color space at or near the border between the English composite categories of "warm" and "cool". This fault line in color space represents a fundamental constraint on color naming. Here we report that the two-way categorization along the fault line is correlated with the sign of the L- versus M-cone contrast of a stimulus color. Moreover, we found that the sign of the L-M cone contrast also accounted for the two-way clustering of the spatially distributed neural responses in small regions of the macaque primary visual cortex, visualized with optical imaging. These small regions correspond to the hue maps, where our previous study found a spatially organized representation of stimulus hue. Altogether, these results establish a direct link between a universal constraint on color naming and the cone-specific information that is represented in the primate early visual system.

The McDonald Observatory lunar laser ranging project

Science.gov (United States)

Silverberg, E. C.

1978-01-01

A summary of the activities of the McDonald lunar laser ranging station at Fort Davis for the FY 77-78 fiscal year is presented. The lunar laser experiment uses the observatory 2.7m reflecting telescope on a thrice-per-day, 21-day-per-lunation schedule. Data are recorded on magnetic tapes and sent to the University of Texas at Austin where the data is processed. After processing, the data is distributed to interested analysis centers and later to the National Space Science Data Center where it is available for routine distribution. Detailed reports are published on the McDonald operations after every fourth lunation or approximately once every 115 days. These reports contain a day-by-day documentation of the ranging activity, detailed discussions of the equipment development efforts, and an abundance of other information as is needed to document and archive this important data type.

Time biases in laser ranging observations: A concerning issue of Space Geodesy

Science.gov (United States)

Exertier, Pierre; Belli, A.; Lemoine, J. M.

2017-09-01

Time transfer by Laser Ranging (LR) recently demonstrated a remarkable stability (a few ps over ∼1000 s) and accuracy (synchronizing both space and ground clocks over distances from a few thousands to tens of thousands kilometers. Given its potential role in navigation, fundamental physics and metrology, it is crucial that synergy between laser ranging and Time&Frequency (T/F) technologies improves to meet the present and future space geodesy requirements. In this article, we examine the behavior of T/F systems that are used in LR tracking stations of the international laser ranging service. The approach we investigate is to compute time synchronization between clocks used at LR stations using accurate data of the Time Transfer by Laser Link (T2L2) experiment onboard the satellite Jason-2 (Samain et al., 2014). Systematic time biases are estimated against the UTC time scale for a set of 22 observing stations in 2013, in the range of zero to a few μ s. Our results suggest that the ILRS network suffers from accuracy issues, due to time biases in the laser ranging observations. We discuss how these systematic effects impact the precise orbit determination of LAGEOS geodetic satellites over a 1-year analysis, and additionally give a measure of the local effect into station coordinates, regarding in particular the effect in the east-west component that is of 2-6 mm for a typical systematic time bias of one μ s.

Assessing probe-specific dye and slide biases in two-color microarray data

Directory of Open Access Journals (Sweden)

Goldberg Zelanna

2008-07-01

Full Text Available Abstract Background A primary reason for using two-color microarrays is that the use of two samples labeled with different dyes on the same slide, that bind to probes on the same spot, is supposed to adjust for many factors that introduce noise and errors into the analysis. Most users assume that any differences between the dyes can be adjusted out by standard methods of normalization, so that measures such as log ratios on the same slide are reliable measures of comparative expression. However, even after the normalization, there are still probe specific dye and slide variation among the data. We define a method to quantify the amount of the dye-by-probe and slide-by-probe interaction. This serves as a diagnostic, both visual and numeric, of the existence of probe-specific dye bias. We show how this improved the performance of two-color array analysis for arrays for genomic analysis of biological samples ranging from rice to human tissue. Results We develop a procedure for quantifying the extent of probe-specific dye and slide bias in two-color microarrays. The primary output is a graphical diagnostic of the extent of the bias which called ECDF (Empirical Cumulative Distribution Function, though numerical results are also obtained. Conclusion We show that the dye and slide biases were high for human and rice genomic arrays in two gene expression facilities, even after the standard intensity-based normalization, and describe how this diagnostic allowed the problems causing the probe-specific bias to be addressed, and resulted in important improvements in performance. The R package LMGene which contains the method described in this paper has been available to download from Bioconductor.

Study of pseudo noise CW diode laser for ranging applications

Science.gov (United States)

Lee, Hyo S.; Ramaswami, Ravi

1992-01-01

A new Pseudo Random Noise (PN) modulated CW diode laser radar system is being developed for real time ranging of targets at both close and large distances (greater than 10 KM) to satisy a wide range of applications: from robotics to future space applications. Results from computer modeling and statistical analysis, along with some preliminary data obtained from a prototype system, are presented. The received signal is averaged for a short time to recover the target response function. It is found that even with uncooperative targets, based on the design parameters used (200-mW laser and 20-cm receiver), accurate ranging is possible up to about 15 KM, beyond which signal to noise ratio (SNR) becomes too small for real time analog detection.

How do we select multiple features? Transient costs for selecting two colors rather than one, persistent costs for color-location conjunctions.

Science.gov (United States)

Lo, Shih-Yu; Holcombe, Alex O

2014-02-01

In a previous study Lo, Howard, & Holcombe (Vision Research 63:20-33, 2012), selecting two colors did not induce a performance cost, relative to selecting one color. For example, requiring possible report of both a green and a red target did not yield a worse performance than when both targets were green. Yet a cost of selecting multiple colors was observed when selection needed be contingent on both color and location. When selecting a red target to the left and a green target to the right, superimposing a green distractor to the left and a red distractor to the right impeded performance. Possibly, participants cannot confine attention to a color at a particular location. As a result, distractors that share the target colors disrupt attentional selection of the targets. The attempt to select the targets must then be repeated, which increases the likelihood that the trial terminates when selection is not effective, even for long trials. Consistent with this, here we find a persistent cost of selecting two colors when the conjunction of color and location is needed, but the cost is confined to short exposure durations when the observer just has to monitor red and green stimuli without the need to use the location information. These results suggest that selecting two colors is time-consuming but effective, whereas selection of simultaneous conjunctions is never entirely successful.

Superimpose of images by appending two simple video amplifier circuits to color television

International Nuclear Information System (INIS)

Kojima, Kazuhiko; Hiraki, Tatsunosuke; Koshida, Kichiro; Maekawa, Ryuichi; Hisada, Kinichi.

1979-01-01

Images are very useful to obtain diagnostic informations in medical fields. Also by superimposing two or three images obtained from the same patient, various informations, for example a degree of overlapping and anatomical land mark, which can not be found in only one image, can be often found. In this paper characteristics of our trial color television system for the purpose of superimposing x-ray images and/or radionuclide images are described. This color television system superimposing two images in each different color consists of two monochromatic vidicon cameras and 20 inches conventional color television in which only two simple video amplifier circuits are added. Signals from vidicon cameras are amplified about 40 dB and are directly applied to cathode terminals of color CRT in the television. This system is very simple and economical color displays, and enhance a degree of overlapping and displacement between images. As one of typical clinical applications, pancreas images were superimposed in color by this method. As a result, size and position of pancreas was enhanced. Also x-ray image and radionuclide image were superimposed to find exactly the position of tumors. Furthermore this system was very useful for color display of multinuclides scintigraphy. (author)

Superimpose of images by appending two simple video amplifier circuits to color television

Energy Technology Data Exchange (ETDEWEB)

Kojima, K; Hiraki, T; Koshida, K; Maekawa, R [Kanazawa Univ. (Japan). School of Paramedicine; Hisada, K

1979-09-01

Images are very useful to obtain diagnostic informations in medical fields. Also by superimposing two or three images obtained from the same patient, various informations, for example a degree of overlapping and anatomical land mark, which can not be found in only one image, can be often found. In this paper characteristics of our trial color television system for the purpose of superimposing x-ray images and/or radionuclide images are described. This color television system superimposing two images in each different color consists of two monochromatic vidicon cameras and 20 inches conventional color television in which only two simple video amplifier circuits are added. Signals from vidicon cameras are amplified about 40 dB and are directly applied to cathode terminals of color CRT in the television. This system is very simple and economical color displays, and enhance a degree of overlapping and displacement between images. As one of typical clinical applications, pancreas images were superimposed in color by this method. As a result, size and position of pancreas was enhanced. Also x-ray image and radionuclide image were superimposed to find exactly the position of tumors. Furthermore this system was very useful for color display of multinuclides scintigraphy.

7 CFR 51.1447 - Fairly uniform in color.

Science.gov (United States)

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Fairly uniform in color. 51.1447 Section 51.1447... color. Fairly uniform in color means that 90 percent or more of the kernels in the lot have skin color within the range of one or two color classifications. ...

Measuring the relativistic perigee advance with satellite laser ranging

CERN Document Server

Iorio, L; Pavlis, E C

2002-01-01

The pericentric advance of a test body by a central mass is one of the classical tests of general relativity. Today, this effect is measured with radar ranging by the perihelion shift of Mercury and other planets in the gravitational field of the Sun, with a relative accuracy of the order of 10 sup - sup 2 -10 sup - sup 3. In this paper, we explore the possibility of a measurement of the pericentric advance in the gravitational field of Earth by analysing the laser-ranged data of some orbiting, or proposed, laser-ranged geodetic satellites. Such a measurement of the perigee advance would place limits on hypothetical, very weak, Yukawa-type components of the gravitational interaction with a finite range of the order of 10 sup 4 km. Thus, we show that, at the present level of knowledge of the orbital perturbations, the relative accuracy, achievable with suitably combined orbital elements of LAGEOS and LAGEOS II, is of the order of 10 sup - sup 3. With the corresponding measured value of (2 + 2 gamma - beta)/3, ...

Real-time multi-target ranging based on chaotic polarization laser radars in the drive-response VCSELs.

Science.gov (United States)

Zhong, Dongzhou; Xu, Geliang; Luo, Wei; Xiao, Zhenzhen

2017-09-04

According to the principle of complete chaos synchronization and the theory of Hilbert phase transformation, we propose a novel real-time multi-target ranging scheme by using chaotic polarization laser radar in the drive-response vertical-cavity surface-emitting lasers (VCSELs). In the scheme, to ensure each polarization component (PC) of the master VCSEL (MVCSEL) to be synchronized steadily with that of the slave VCSEL, the output x-PC and y-PC from the MVCSEL in the drive system and those in the response system are modulated by the linear electro-optic effect simultaneously. Under this condition, by simulating the influences of some key parameters of the system on the synchronization quality and the relative errors of the two-target ranging, related operating parameters can be optimized. The x-PC and the y-PC, as two chaotic radar sources, are used to implement the real-time ranging for two targets. It is found that the measured distances of the two targets at arbitrary position exhibit strong real-time stability and only slight jitter. Their resolutions are up to millimeters, and their relative errors are very small and less than 2.7%.

Producing High Intense Attosecond Pulse Train by Interaction of Three-Color Pulse and Overdense Plasma

Science.gov (United States)

Salehi, M.; Mirzanejad, S.

2017-05-01

Amplifying the attosecond pulse by the chirp pulse amplification method is impossible. Furthermore, the intensity of attosecond pulse is low in the interaction of laser pulse and underdense plasma. This motivates us to propose using a multi-color pulse to produce the high intense attosecond pulse. In the present study, the relativistic interaction of a three-color linearly-polarized laser-pulse with highly overdense plasma is studied. We show that the combination of {{ω }}1, {{ω }}2 and {{ω }}3 frequencies decreases the instance full width at half maximum reflected attosecond pulse train from the overdense plasma surface. Moreover, we show that the three-color pulse increases the intensity of generated harmonics, which is explained by the relativistic oscillating mirror model. The obtained results demonstrate that if the three-color laser pulse interacts with overdense plasma, it will enhance two orders of magnitude of intensity of ultra short attosecond pulses in comparison with monochromatic pulse.

Collisional absorption of two laser beams in plasma

International Nuclear Information System (INIS)

Mohan, M.; Acharya, R.

1977-04-01

The collisional absorption of two laser beams is considered by solving the kinetic equation for the plasma electron. Results show that the simultaneous effect of two laser beams on the heating rate is greater as compared with the individual contribution of each laser beam when the two laser beams have a difference of frequencies equal to the plasma frequency

Two dimensional simulation of high power laser-surface interaction

International Nuclear Information System (INIS)

Goldman, S.R.; Wilke, M.D.; Green, R.E.L.; Johnson, R.P.; Busch, G.E.

1998-01-01

For laser intensities in the range of 10 8 --10 9 W/cm 2 , and pulse lengths of order 10 microsec or longer, the authors have modified the inertial confinement fusion code Lasnex to simulate gaseous and some dense material aspects of the laser-matter interaction. The unique aspect of their treatment consists of an ablation model which defines a dense material-vapor interface and then calculates the mass flow across this interface. The model treats the dense material as a rigid two-dimensional mass and heat reservoir suppressing all hydrodynamic motion in the dense material. The computer simulations and additional post-processors provide predictions for measurements including impulse given to the target, pressures at the target interface, electron temperatures and densities in the vapor-plasma plume region, and emission of radiation from the target. The authors will present an analysis of some relatively well diagnosed experiments which have been useful in developing their modeling. The simulations match experimentally obtained target impulses, pressures at the target surface inside the laser spot, and radiation emission from the target to within about 20%. Hence their simulational technique appears to form a useful basis for further investigation of laser-surface interaction in this intensity, pulse-width range. This work is useful in many technical areas such as materials processing

Davenport Ranges, Northern Territory, Australia, SRTM Shaded Relief and Colored Height

Science.gov (United States)

2005-01-01

The Davenport Ranges of central Australia have been inferred to be among the oldest persisting landforms on Earth, founded on the belief that the interior of Australia has been tectonically stable for at least 700 million years. New rock age dating techniques indicate that substantial erosion has probably occurred over that time period and that the landforms are not nearly that old, but landscape evolution certainly occurs much slower here (at least now) than is typical across Earth's surface. Regardless of their antiquity, the Davenport Ranges exhibit a striking landform pattern as shown in this display of elevation data from the Shuttle Radar Topography Mission (SRTM). Quartzites and other erosion resistant strata form ridges within anticlinal (arched up) and synclinal (arched down) ovals and zigzags. These structures, if not the landforms, likely date back at least hundreds of millions of years, to a time when tectonic forces were active. Maximum local relief is only about 60 meters (about 200 feet), which is enough to contrast greatly with the extremely low relief surrounding terrain. Two visualization methods were combined to produce this image: shading and color coding of topographic height. The shade image was derived by computing topographic slope in the northeast-southwest (image top to bottom) direction, so that northeast slopes appear bright and southwest slopes appear dark. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and tan, to white at the highest elevations. Elevation data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data

Femtosecond laser surface structuring of molybdenum thin films

Energy Technology Data Exchange (ETDEWEB)

Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Mthunzi, P. [Council for Scientific and Industrial Research (CSIR), Biophotonics Lab: National Laser Centre Pretoria, 0001 (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Itala (Italy); Sechoghela, P.; Mongwaketsi, N. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Ramponi, R. [Institute for Photonics and Nanotechnologies (IFN)–CNR, Piazza Leanardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa)

2015-10-30

Highlights: • Color change of the molybdenum thin film from shinny to violet–yellowish color after laser irradiation at various laser powers. • Formation of the molybdenum dioxide coating after laser exposure, as confirmed by the X-ray diffraction spectrometry. • Selective solar absorbing nature of the laser exposed films. • Study of the binding energies is presented in this contribution using the XPS spectrometry. - Abstract: This contribution reports on the femtosecond surface structuring of molybdenum thin coatings deposited by electron beam evaporation onto Corning glass substrates. The 1-D type periodic grating lines created by such an ablation showed that the widths of the shallow grooves followed a logarithmic dependence with the laser energy incident on the molybdenum film. The electronic valence “x” of the created oxide surface layer MoO{sub x} was found to be incident laser power dependent via Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction investigations. Such a photo-induced MoO{sub x}–Mo nanocomposite exhibited effective selective solar absorption in the UV–vis–IR spectral range.

Particle range in a laser-plasma generated soft X-ray chamber

Energy Technology Data Exchange (ETDEWEB)

Bollanti, S.; Letardi, T. [ENEA, Centro Ricerche Frascati, Rome (Italy). Dipt. Innovazione; Zheng, C. [EL.EN, Calenzano, Florence (Italy)

1999-07-01

Some analytical forms are deduced for calculating the flight range of a spherical particle ejected from the laser plasma target and retarded by gas resistance. it is shown that the gas pressure influence on viscosity can not be neglected when are estimated the expansion ranges fro debris of various sizes in a helium gas-buffered, laser produced plasma chamber. [Italian] Vengono ricavate alcune formule analitiche per il calcolo del range di frammenti sferici espulsi con velocita' iniziale dati e frenati dalla resistenza di un fondo gassoso. Si mostra che nei gas considerati non si puo' ignorare influenza della pressione nella viscosita' del gas.

Integrated two-section discrete mode laser

NARCIS (Netherlands)

Anandarajah, P.M.; Latkowski, S.; Browning, C.; Zhou, R.; O'Carroll, J.; Phelan, R.; Kelly, B.; O'Gorman, J.; Barry, L.P.

2012-01-01

The authors present the design and characterization of a novel integrated two-section discrete mode index patterned diode laser source. The two slotted regions etched into the laser ridge waveguide are formed in the same fabrication step as the ridge, thus avoiding the requirement for complex

Performance Considerations for the SIMPL Single Photon, Polarimetric, Two-Color Laser Altimeter as Applied to Measurements of Forest Canopy Structure and Composition

Science.gov (United States)

Dabney, Philip W.; Harding, David J.; Valett, Susan R.; Vasilyev, Aleksey A.; Yu, Anthony W.

2012-01-01

The Slope Imaging Multi-polarization Photon-counting Lidar (SIMPL) is a multi-beam, micropulse airborne laser altimeter that acquires active and passive polarimetric optical remote sensing measurements at visible and near-infrared wavelengths. SIMPL was developed to demonstrate advanced measurement approaches of potential benefit for improved, more efficient spaceflight laser altimeter missions. SIMPL data have been acquired for wide diversity of forest types in the summers of 2010 and 2011 in order to assess the potential of its novel capabilities for characterization of vegetation structure and composition. On each of its four beams SIMPL provides highly-resolved measurements of forest canopy structure by detecting single-photons with 15 cm ranging precision using a narrow-beam system operating at a laser repetition rate of 11 kHz. Associated with that ranging data SIMPL provides eight amplitude parameters per beam unlike the single amplitude provided by typical laser altimeters. Those eight parameters are received energy that is parallel and perpendicular to that of the plane-polarized transmit pulse at 532 nm (green) and 1064 nm (near IR), for both the active laser backscatter retro-reflectance and the passive solar bi-directional reflectance. This poster presentation will cover the instrument architecture and highlight the performance of the SIMPL instrument with examples taken from measurements for several sites with distinct canopy structures and compositions. Specific performance areas such as probability of detection, after pulsing, and dead time, will be highlighted and addressed, along with examples of their impact on the measurements and how they limit the ability to accurately model and recover the canopy properties. To assess the sensitivity of SIMPL's measurements to canopy properties an instrument model has been implemented in the FLIGHT radiative transfer code, based on Monte Carlo simulation of photon transport. SIMPL data collected in 2010 over

Simulation of Far-Field Superresolution Fluorescence Imaging with Two-Color One-Photon Excitation of Reversible Photoactivatable Protein

International Nuclear Information System (INIS)

Wang Chen; Qiao Ling-Ling; Mao Zheng-Le

2011-01-01

We propose to achieve far-field super-resolution imaging by using offset two-color one-photon (2C1P) excitation of reversible photoactivatable fluorescence proteins. Due to the distinctive photoswitching performance of the proteins, such as dronpa, the fluorescence emission will only come from the overlapped region of activation beam and excitation beam. The analysis solution of rate equation shows that the resolution of offset 2C1P microscope is 'engineered' by laser power of excitation and activation beams and the power ratio between them. Superior lateral and transverse resolution is theoretically demonstrated compared with conventional fluorescence scanning microscopy. (fundamental areas of phenomenology(including applications))

Treatment of tattoos with a 755-nm Q-switched alexandrite laser and novel 1064 nm and 532 nm Nd:YAG laser handpieces pumped by the alexandrite treatment beam.

Science.gov (United States)

Bernstein, Eric F; Bhawalkar, Jay; Clifford, Joan; Hsia, James

2010-11-01

Multi-colored and even black tattoos often require more than one wavelength to remove the target pigment. The authors report here a novel alexandrite laser with two Nd:YAG laser handpieces pumped by the alexandrite treatment beam enabling the delivery of three wavelengths from a single device. To describe and evaluate the effectiveness of a novel Q-switched laser-pumped laser for treating tattoos. Twenty tattoos in 14 subjects were treated at four-week intervals using a combination of available wavelengths (532, 755 and 1064 nm) as determined by the treating physician. Digital cross-polarized photographs were taken before treatment and two months following the fourth and final treatment. Photographs were evaluated by three physician observers blinded as to the treatment condition and rated for clearance by the following scale: 1 = > 95 percent, 2 = 76-95 percent, 3 = 51-75 percent, 4 = 26-50 percent and 5 = 0-25 percent clearance. The average clearance score was 3.1, in the 51-75 percent range, two months following four treatments. No scarring, hyper- or hypopigmentation was noted on post-treatment photographs or by the treating physician. The alexandrite and alexandrite-pumped 532 nm and 1064 nm Q-switched lasers are effective for removing decorative tattoos, and represents the first commercial laser with laser-pumped, laser handpieces.

Automated tracking for advanced satellite laser ranging systems

Science.gov (United States)

McGarry, Jan F.; Degnan, John J.; Titterton, Paul J., Sr.; Sweeney, Harold E.; Conklin, Brion P.; Dunn, Peter J.

1996-06-01

NASA's Satellite Laser Ranging Network was originally developed during the 1970's to track satellites carrying corner cube reflectors. Today eight NASA systems, achieving millimeter ranging precision, are part of a global network of more than 40 stations that track 17 international satellites. To meet the tracking demands of a steadily growing satellite constellation within existing resources, NASA is embarking on a major automation program. While manpower on the current systems will be reduced to a single operator, the fully automated SLR2000 system is being designed to operate for months without human intervention. Because SLR2000 must be eyesafe and operate in daylight, tracking is often performed in a low probability of detection and high noise environment. The goal is to automatically select the satellite, setup the tracking and ranging hardware, verify acquisition, and close the tracking loop to optimize data yield. TO accomplish the autotracking tasks, we are investigating (1) improved satellite force models, (2) more frequent updates of orbital ephemerides, (3) lunar laser ranging data processing techniques to distinguish satellite returns from noise, and (4) angular detection and search techniques to acquire the satellite. A Monte Carlo simulator has been developed to allow optimization of the autotracking algorithms by modeling the relevant system errors and then checking performance against system truth. A combination of simulator and preliminary field results will be presented.

Effect of elimination of nitrogen and/or hypoxia or restricted visual environment on color vision and range of accommodation

Science.gov (United States)

Wolbarsht, M. L.; White, C. W.; Anderson, W. B., Jr.

1973-01-01

The effects upon range of accommodation and color vision of reduced atmospheric pressure, at partial and complete elimination of nitrogen, of hypoxia, and of exposure for varying periods of time to restricted visual environment, have been studied alone or in various combinations. Measurements were made on the electroretinogram, the electrooculogram, and the diameter of the retinal vessels as an indicator of blood flow to the retina at the time of total elimination of nitrogen. An objective method was used to test range of accommodation. In the color vision test the flicker colors of a Benham's top were matched with a colorimeter.

Efficacy and persistence of tooth bleaching using a diode laser with three different treatment regimens.

Science.gov (United States)

Al Quran, Firas A M; Mansour, Yasar; Al-Hyari, Sabaa; Al Wahadni, Ahed; Mair, Lawrence

2011-01-01

Studies have measured the effectiveness of tooth bleaching, however there are very few studies that have measured the persistence in color change after a 6-month follow-up. This study assessed the efficacy of the laser bleaching process using different regimens, and the persistence of color change over a 6-month period. Sixty patients divided into three equal groups were subjected to bleaching using a diode laser with 34% hydrogen peroxide. Group 1: patients subjected to one session of laser bleaching. Group 2: patients subjected to two sessions of laser bleaching with a 1-week interval. Group 3: the same as Group 2 but followed by home bleaching once a month for 3 months. The color was assessed four times: before bleaching, directly after bleaching, 3 months after bleaching, and 6 months after bleaching. All teeth had a significant color change at 6 months, but all teeth had regressed from the maximum value. There was significantly less regression in color for Group 3, followed by Groups 2 and 1, respectively. The combined technique of in-office laser bleaching for two sessions with a 1-week interval, followed by home bleaching once a month for 3 months gave more persistence in color change. In-office power bleaching using a laser assisted hydrogen peroxide system repeated after a week, combined with home bleaching once a month for 3 months, is an effective bleaching regimen with less color regression after 6 months compared to a regimen of in-office bleaching alone.

Time Biases in laser ranging measurements; impacts on geodetic products (Reference Frame and Orbitography)

Science.gov (United States)

Belli, A.; Exertier, P.; Lemoine, F. G.; Chinn, D. S.; Zelensky, N. P.

2017-12-01

The GGOS objectives are to maintain a geodetic network with an accuracy of 1 mm and a stability of 0.1 mm per year. For years, the laser ranging technique, which provide very accurate absolute distances to geodetic targets enable to determine the scale factor as well as coordinates of the geocenter. In order to achieve this goal, systematic errors appearing in the laser ranging measurements must be considered and solved. In addition to Range Bias (RB), which is the primary source of uncertainty of the technique, Time Bias (TB) has been recently detected by using the Time Transfer by Laser Link (T2L2) space instrument capability on-board the satellite Jason-2. Instead of determining TB through the precise orbit determination that is applied to commonly used geodetic targets like LAGEOS to estimate global geodetic products, we have developed, independently, a dedicated method to transfer time between remote satellite laser ranging stations. As a result, the evolving clock phase shift to UTC of around 30 stations has been determined under the form of time series of time bias per station from 2008 to 2016 with an accuracy of 3-4 ns. It demonstrated the difficulty, in terms of Time & Frequency used technologies, to locally maintain accuracy and long term stability at least in the range of 100 ns that is the current requirement for time measurements (UTC) for the laser ranging technique. Because some laser ranging stations oftently exceed this limit (from 100 ns to a few μs) we have been studying these effects first on the precision orbit determination itself, second on the station positioning. We discuss the impact of TB on LAGEOS and Jason-2 orbits, which appears to affect the along-track component essentially. We also investigate the role of TB in global geodetic parameters as the station coordinates. Finally, we propose to provide the community with time series of time bias of laser ranging stations, under the form of a data- handling-file in order to be included in

Absolute distance measurement with correction of air refractive index by using two-color dispersive interferometry.

Science.gov (United States)

Wu, Hanzhong; Zhang, Fumin; Liu, Tingyang; Li, Jianshuang; Qu, Xinghua

2016-10-17

Two-color interferometry is powerful for the correction of the air refractive index especially in the turbulent air over long distance, since the empirical equations could introduce considerable measurement uncertainty if the environmental parameters cannot be measured with sufficient precision. In this paper, we demonstrate a method for absolute distance measurement with high-accuracy correction of air refractive index using two-color dispersive interferometry. The distances corresponding to the two wavelengths can be measured via the spectrograms captured by a CCD camera pair in real time. In the long-term experiment of the correction of air refractive index, the experimental results show a standard deviation of 3.3 × 10-8 for 12-h continuous measurement without the precise knowledge of the environmental conditions, while the variation of the air refractive index is about 2 × 10-6. In the case of absolute distance measurement, the comparison with the fringe counting interferometer shows an agreement within 2.5 μm in 12 m range.

Two-color infrared detector

Science.gov (United States)

Klem, John F; Kim, Jin K

2014-05-13

A two-color detector includes a first absorber layer. The first absorber layer exhibits a first valence band energy characterized by a first valence band energy function. A barrier layer adjoins the first absorber layer at a first interface. The barrier layer exhibits a second valence band energy characterized by a second valence band energy function. The barrier layer also adjoins a second absorber layer at a second interface. The second absorber layer exhibits a third valence band energy characterized by a third valence band energy function. The first and second valence band energy functions are substantially functionally or physically continuous at the first interface and the second and third valence band energy functions are substantially functionally or physically continuous at the second interface.

Precision Lunar Laser Ranging For Lunar and Gravitational Science

Science.gov (United States)

Merkowitz, S. M.; Arnold, D.; Dabney, P. W.; Livas, J. C.; McGarry, J. F.; Neumann, G. A.; Zagwodzki, T. W.

2008-01-01

Laser ranging to retroreflector arrays placed on the lunar surface by the Apollo astronauts and the Soviet Lunar missions over the past 39 years have dramatically increased our understanding of gravitational physics along with Earth and Moon geophysics, geodesy, and dynamics. Significant advances in these areas will require placing modern retroreflectors and/or active laser ranging systems at new locations on the lunar surface. Ranging to new locations will enable better measurements of the lunar librations, aiding in our understanding of the interior structure of the moon. More precise range measurements will allow us to study effects that are too small to be observed by the current capabilities as well as enabling more stringent tests of Einstein's theory of General Relativity. Setting up retroreflectors was a key part of the Apollo missions so it is natural to ask if future lunar missions should include them as well. The Apollo retroreflectors are still being used today, and nearly 40 years of ranging data has been invaluable for scientific as well as other studies such as orbital dynamics. However, the available retroreflectors all lie within 26 degrees latitude of the equator, and the most useful ones within 24 degrees longitude of the sub-earth meridian. This clustering weakens their geometrical strength.

Development of softcopy environment for primary color banding visibility assessment

Science.gov (United States)

Min, Byungseok; Pizlo, Zygmunt; Allebach, Jan P.

2008-01-01

Fine-pitch banding is one of the most unwanted artifacts in laser electrophotographic (EP) printers. It is perceived as a quasiperiodic fluctuation in the process direction. Therefore, it is essential for printer vendors to know how banding is perceived by humans in order to improve print quality. Monochrome banding has been analyzed and assessed by many researchers; but there is no literature that deals with the banding of color laser printers as measured from actual prints. The study of color banding is complicated by the fact that the color banding signal is physically defined in a three-dimensional color space, while banding perception is described in a one-dimensional sense such as more banding or less banding. In addition, the color banding signal arises from the independent contributions of the four primary colorant banding signals. It is not known how these four distinct signals combine to give rise to the perception of color banding. In this paper, we develop a methodology to assess the banding visibility of the primary colorant cyan based on human visual perception. This is our first step toward studying the more general problem of color banding in combinations of two or more colorants. According to our method, we print and scan the cyan test patch, and extract the banding profile as a one dimensional signal so that we can freely adjust the intensity of banding. Thereafter, by exploiting the pulse width modulation capability of the laser printer, the extracted banding profile is used to modulate a pattern consisting of periodic lines oriented in the process direction, to generate extrinsic banding. This avoids the effect of the halftoning algorithm on the banding. Furthermore, to conduct various banding assessments more efficiently, we also develop a softcopy environment that emulates a hardcopy image on a calibrated monitor, which requires highly accurate device calibration throughout the whole system. To achieve the same color appearance as the hardcopy

Lunar laser ranging: the millimeter challenge

International Nuclear Information System (INIS)

Murphy, T W

2013-01-01

Lunar laser ranging has provided many of the best tests of gravitation since the first Apollo astronauts landed on the Moon. The march to higher precision continues to this day, now entering the millimeter regime, and promising continued improvement in scientific results. This review introduces key aspects of the technique, details the motivations, observables, and results for a variety of science objectives, summarizes the current state of the art, highlights new developments in the field, describes the modeling challenges, and looks to the future of the enterprise. (review article)

Two-wavelength, passive self-injection-controlled operation of diode-pumped cw Yb-doped crystal lasers.

Science.gov (United States)

Louyer, Yann; Wallerand, Jean-Pierre; Himbert, Marc; Deneva, Margarita; Nenchev, Marin

2003-09-20

We demonstrate and investigate a peculiar mode of cw Yb3+-doped crystal laser operation when two emissions, at two independently tunable wavelengths, are simultaneously produced. Both emissions are generated from a single pumped volume and take place in either a single beam or spatially separated beams. The laser employs original two-channel cavities that use a passive self-injection-locking (PSIL) control to reduce intracavity loss. The advantages of the application of the PSIL technique and some limitations are shown. The conditions for two-wavelength multimode operation of the cw quasi-three-level diode-pumped Yb3+ lasers and the peculiarity of such an operation are carried out both theoretically and experimentally. The results reported are based on the example of a Yb3+:GGG laser but similar results are also obtained with a Yb3+:YAG laser. The laser operates in the 1023-1033-nm (1030-1040-nm) range with a total output power of 0.4 W. A two-wavelength, single longitudinal mode generation is also obtained.

Enamel-Caries Prevention Using Two Applications of Fluoride-Laser Sequence.

Science.gov (United States)

Noureldin, Amal; Quintanilla, Ines; Kontogiorgos, Elias; Jones, Daniel

2016-03-01

Studies demonstrated a significant synergism between fluoride and laser in reduction of enamel solubility. However, minimal research has focused on testing the sequence of their application and no other research investigated the preventive effect of repeated applications of a combined treatment. This study investigated the effect of two applications of fluoride-laser sequence on the resistance of sound enamel to cariogenic challenge compared to one-time application. Sixty enamel slabs were cut from 10 human incisors, ground flat, polished and coated with nail varnish except a 2 x 2 mm window. Specimens were randomly assigned into five groups of 12 specimens; (CON-) negative-control received no treatment, (CON+) positive-control received pH challenge, (FV) treated with M fluoride varnish, (F-L1) one-application fluoride-varnish followed by CO2 laser-treatment (short-pulsed 10.6 µm, 2.4J/ cm2, 10HZ, 10sec), and (F-L2) two-applications of fluoride varnish-laser treatment. Specimens were left in distilled water for one day between applications. Except CON-, all groups were submitted to pH cycling for 9-days (8 demin/ remin + 1 day remineralisation bath) at 37°C. Enamel demineralization was quantitatively evaluated by measurement of Knoop surface-microhardness (SM H) (50-grams/10 seconds). Data were analyzed using one-way ANOVA (p ≤ 0.05) followed by Duncan's Multiple Range Test. Within the limitations of this study, it was found that one or two applications of fluoride-laser sequence significantly improved resistance of the sound enamel surface to acid attack compared to FV-treated group. Although the two applications of fluoride-laser sequence (F-L1 and F-L2) showed higher SMH values, significant resistance to demineralization was only obtained with repeated applications.

Q-switched laser tattoo removal

Directory of Open Access Journals (Sweden)

Viljem H. topčič

2013-10-01

Full Text Available Background: Decorative tattooing gained popularity in many western countries throughout the 1990s. Some estimates show that approximately 10 % of men in the United States already have tattoos. However, tattoos often become a personal regret. As recent surveys suggest, 17 % of people that have obtained a tattoo and more than 50 % of adults over the age of 40 in the United States of America consider having them removed. The same trend can be observed in our country as well. Laser therapy is the gold standard for tattoo removal. In Slovenia, laser tattoo removal therapy is available and widely accessible. There is a wide range of facilities offering laser tattoo removal, ranging from different private clinics to beauty salons. Different facilities use different lasers, but not all lasers, however, are optimal for successful and complete tattoo removal, as inappropriate use can cause many unwanted side effects.Methods: Eleven (11 patients (2 men and 9 women requesting tattoo removal were treated in our department. When treating our patients, we used Fotona’s QX MAX quality-switched Nd:YAG laser which offers four different wavelengths in a single system; 1064 nm Nd:YAG was used to treat and remove dark pigments, 532 nm KTP for red, tan-colored, purple and orange tattoo inks, 650 nm dye for green tattoo inks and 585 nm dye for sky-blue colored inks.Results: Satisfactory tattoo removal was achieved in all patients treated. Patients were very satisfied with the success and the number of treatments needed for tattoo removal. There were mild unwanted side effects and the pain was moderate. The average number of treatments required for complete tattoo removal was less than 7, ranging from 3 to 21 treatments. Patients’ satisfaction with tattoo removal was estimated at 5.2 (on a scale from 1 to 6.Conclusions: Our study showed that Q-switched lasers successfully remove tattoo ink, however several treatments are required for satisfactory tattoo removal

Advanced technologies in the ASI MLRO towards a new generation laser ranging system

Science.gov (United States)

Varghese, Thomas; Bianco, Giuseppe

1994-01-01

Matera Laser Ranging Observatory (MLRO) is a high performance, highly automated optical and astronomical observatory currently under design and development by AlliedSignal for the Italian Space Agency (ASI). It is projected to become operational at the Centro Geodesia Spaziale in Matera, Italy, in 1997. MLRO, based on a 1.5-meter astronomical quality telescope, will perform ranging to spacecraft in earthbound orbits, lunar reflectors, and specially equipped deep space missions. The primary emphasis during design is to incorporate state-of-the-art technologies to produce an intelligent, automated, high accuracy ranging system that will mimic the characteristic features of a fifth generation laser ranging system. The telescope has multiple ports and foci to support future experiments in the areas of laser communications, lidar, astrometry, etc. The key features providing state-of-the-art ranging performance include: a diode-pumped picosecond (50 ps) laser, high speed (3-5 GHz) optoelectronic detection and signal processing, and a high accuracy (6 ps) high resolution (less than 2 ps) time measurement capability. The above combination of technologies is expected to yield millimeter laser ranging precision and accuracy on targets up to 300,000 km, surpassing the best operational instrument performance to date by a factor of five or more. Distributed processing and control using a state-of-the-art computing environment provides the framework for efficient operation, system optimization, and diagnostics. A computationally intelligent environment permits optimal planning, scheduling, tracking, and data processing. It also supports remote access, monitor, and control for joint experiments with other observatories.

Color variability and body size of larvae of two Epomis species (Coleoptera: Carabidae in Israel

Directory of Open Access Journals (Sweden)

Gil Wizen

2011-07-01

Full Text Available Species identification using the characteristics of developmental stages is challenging. However, for insect taxonomy the coloration of larval stages can be an informative feature. The use of live specimens is recommended for this because the color fades in preserved specimens. In this study we examine the possibility of using variation in coloration and color pattern of larvae in order to distinguish between two ground beetles species Epomis dejeani Dejean, 1831 and E. circumscriptus Duftschmid, 1812. We present an atlas and describe the coloration and body size of the three larval stages of the above species based on live specimens. The first instar larvae of the two Epomis species can be easily distinguished based on their color. From the second instar on, the variability in coloration and color patterns increases, creating an overlap in these attributes between larvae of the two species. Except for minor differences in color of the antennae and the base of the mandibles, larvae of the two species are indistinguishable at the second and third larval stages. To the best of our knowledge this is the first attempt to use variation in coloration and color pattern in live larvae in order to identify coleopterans. The color atlas of the larvae enables simple separation of the two Epomis species without requiring sophisticated magnifying devices, although it is less straightforward at the second and third larval stages. We found similar body lengths between the two species for all developmental stages, except for third instar larvae prior to pupation. In the two species the difference in larval body length before pupation positively correlated with that of the adult beetles. More than 70% of the adults' length can be explained by the length of the late third-instar larva; i.e. the large larvae develop into large adults. The larger specimens are the females.

Recording and Modelling of MONUMENTS' Interior Space Using Range and Optical Sensors

Science.gov (United States)

Georgiadis, Charalampos; Patias, Petros; Tsioukas, Vasilios

2016-06-01

Three dimensional modelling of artefacts and building interiors is a highly active research field in our days. Several techniques are being utilized to perform such a task, spanning from traditional surveying techniques and photogrammetry to structured light scanners, laser scanners and so on. New technological advancements in both hardware and software create new recording techniques, tools and approaches. In this paper we present a new recording and modelling approach based on the SwissRanger SR4000 range camera coupled with a Canon 400D dSLR camera. The hardware component of our approach consists of a fixed base, which encloses the range and SLR cameras. The two sensors are fully calibrated and registered to each other thus we were able to produce colorized point clouds acquired from the range camera. In this paper we present the initial design and calibration of the system along with experimental data regarding the accuracy of the proposed approach. We are also providing results regarding the modelling of interior spaces and artefacts accompanied with accuracy tests from other modelling approaches based on photogrammetry and laser scanning.

Filament-induced remote surface ablation for long range laser-induced breakdown spectroscopy operation

International Nuclear Information System (INIS)

Rohwetter, Ph.; Stelmaszczyk, K.; Woeste, L.; Ackermann, R.; Mejean, G.; Salmon, E.; Kasparian, J.; Yu, J.; Wolf, J.-P.

2005-01-01

We demonstrate laser induced ablation and plasma line emission from a metallic target at distances up to 180 m from the laser, using filaments (self-guided propagation structures ∼ 100 μm in diameter and ∼ 5 x 10 13 W/cm 2 in intensity) appearing as femtosecond and terawatt laser pulses propagating in air. The remarkable property of filaments to propagate over a long distance independently of the diffraction limit opens the frontier to long range operation of the laser-induced breakdown spectroscopy technique. We call this special configuration of remote laser-induced breakdown spectroscopy 'remote filament-induced breakdown spectroscopy'. Our results show main features of filament-induced ablation on the surface of a metallic sample and associated plasma emission. Our experimental data allow us to estimate requirements for the detection system needed for kilometer-range remote filament-induced breakdown spectroscopy experiment

The Construction and Calibration of a LADAR (Laser Detection and Ranging) Cross-Section Measurement Range

Science.gov (United States)

1985-12-01

resonator optics consist of two porro prisms which are oriented 900 from one another about the cavity’s optical axis. In other words, the roof edges of each... prism are perpendicular to one another. The Nd:YAG laser rod measures 5 mm in diameter by 75 mm long and is optically pumped by a Xenon flashlamp. Q...Switching of the laser is performed by a Pockels Cell. A dielectric polarizer is sealed between two right angle prisms which are joined symetrically

Comparison of three methods reducing the beam parameter product of a laser diode stack for long range laser illumination applications

Science.gov (United States)

Lutz, Yves; Poyet, Jean-Michel; Metzger, Nicolas

2013-10-01

Laser diode stacks are interesting laser sources for active imaging illuminators. They allow the accumulation of large amounts of energy in multi-pulse mode, which is well suited for long-range image recording. Even when laser diode stacks are equipped with fast-axis collimation (FAC) and slow-axis collimation (SAC) microlenses, their beam parameter product (BPP) are not compatible with a direct use in highly efficient and compact illuminators. This is particularly true when narrow divergences are required such as for long range applications. To overcome these difficulties, we conducted investigations in three different ways. A first near infrared illuminator based on the use of conductively cooled mini-bars was designed, realized and successfully tested during outdoor experimentations. This custom specified stack was then replaced in a second step by an off-the-shelf FAC + SAC micro lensed stack where the brightness was increased by polarization overlapping. The third method still based on a commercial laser diode stack uses a non imaging optical shaping principle resulting in a virtually restacked laser source with enhanced beam parameters. This low cost, efficient and low alignment sensitivity beam shaping method allows obtaining a compact and high performance laser diode illuminator for long range active imaging applications. The three methods are presented and compared in this paper.

Using mid-range laser scanners to digitize cultural-heritage sites.

Science.gov (United States)

Spring, Adam P; Peters, Caradoc; Minns, Tom

2010-01-01

Here, we explore new, more accessible ways of modeling 3D data sets that both professionals and amateurs can employ in areas such as architecture, forensics, geotechnics, cultural heritage, and even hobbyist modeling. To support our arguments, we present images from a recent case study in digital preservation of cultural heritage using a mid-range laser scanner. Our appreciation of the increasing variety of methods for capturing 3D spatial data inspired our research. Available methods include photogrammetry, airborne lidar, sonar, total stations (a combined electronic and optical survey instrument), and midand close-range scanning.1 They all can produce point clouds of varying density. In our case study, the point cloud produced by a mid-range scanner demonstrates how open source software can make modeling and disseminating data easier. Normally, researchers would model this data using expensive specialized software, and the data wouldn't extend beyond the laser-scanning community.

Modeling human color categorization: Color discrimination and color memory

OpenAIRE

Heskes, T.; van den Broek, Egon; Lucas, P.; Hendriks, Maria A.; Vuurpijl, L.G.; Puts, M.J.H.; Wiegerinck, W.

2003-01-01

Color matching in Content-Based Image Retrieval is done using a color space and measuring distances between colors. Such an approach yields non-intuitive results for the user. We introduce color categories (or focal colors), determine that they are valid, and use them in two experiments. The experiments conducted prove the difference between color categorization by the cognitive processes color discrimination and color memory. In addition, they yield a Color Look-Up Table, which can improve c...

Fluorescence of ceramic color standards

International Nuclear Information System (INIS)

Koo, Annette; Clare, John F.; Nield, Kathryn M.; Deadman, Andrew; Usadi, Eric

2010-01-01

Fluorescence has been found in color standards available for use in calibration and verification of color measuring instruments. The fluorescence is excited at wavelengths below about 600 nm and emitted above 700 nm, within the response range of silicon photodiodes, but at the edge of the response of most photomultipliers and outside the range commonly scanned in commercial colorimeters. The degree of fluorescence on two of a set of 12 glossy ceramic tiles is enough to introduce significant error when those tiles have been calibrated in one mode of measurement and are used in another. We report the nature of the fluorescence and the implications for color measurement.

Two electron response to an intense x-ray free electron laser pulse

International Nuclear Information System (INIS)

Moore, L R; Parker, J S; Meharg, K J; Armstrong, G S J; Taylor, K T

2009-01-01

New x-ray free electron lasers (FELs) promise an ultra-fast ultra-intense regime in which new physical phenomena, such as double core hole formation in at atom, should become directly observable. Ahead of x-ray FEL experiments, an initial key task is to theoretically explore such fundamental laser-atom interactions and processes. To study the response of a two-electron positive ion to an intense x-ray FEL pulse, our theoretical approach is a direct numerical integration, incorporating non-dipole Hamiltonian terms, of the full six-dimensional time-dependent Schroedinger equation. We present probabilities of double K-shell ionization in the two-electron positive ions Ne 8+ and Ar 16+ exposed to x-ray FEL pulses with frequencies in the range 50 au to 300 au and intensities in the range 10 17 to 10 22 W/cm 2 .

Two-color walking Peregrine solitary waves.

Science.gov (United States)

Baronio, Fabio; Chen, Shihua; Mihalache, Dumitru

2017-09-15

We study the extreme localization of light, evolving upon a non-zero background, in two-color parametric wave interaction in nonlinear quadratic media. We report the existence of quadratic Peregrine solitary waves, in the presence of significant group-velocity mismatch between the waves (or Poynting vector beam walk-off), in the regime of cascading second-harmonic generation. This finding opens a novel path for the experimental demonstration of extreme rogue waves in ultrafast quadratic nonlinear optics.

High contrast laser marking of alumina

Science.gov (United States)

Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; del Val, J.; Comesaña, R.; Lusquiños, F.; Pou, J.

2015-05-01

Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks.

Two-photon transitions driven by a combination of diode and femtosecond lasers.

Science.gov (United States)

Moreno, Marco P; Nogueira, Giovana T; Felinto, Daniel; Vianna, Sandra S

2012-10-15

We report on the combined action of a cw diode laser and a train of ultrashort pulses when each of them drives one step of the 5S-5P-5D two-photon transition in rubidium vapor. The fluorescence from the 6P(3/2) state is detected for a fixed repetition rate of the femtosecond laser while the cw-laser frequency is scanned over the rubidium D(2) lines. This scheme allows for a velocity selective spectroscopy in a large spectral range including the 5D(3/2) and 5D(5/2) states. The results are well described in a simplified frequency domain picture, considering the interaction of each velocity group with the cw laser and a single mode of the frequency comb.

Modeling human color categorization: Color discrimination and color memory

NARCIS (Netherlands)

Heskes, T.; van den Broek, Egon; Lucas, P.; Hendriks, Maria A.; Vuurpijl, L.G.; Puts, M.J.H.; Wiegerinck, W.

2003-01-01

Color matching in Content-Based Image Retrieval is done using a color space and measuring distances between colors. Such an approach yields non-intuitive results for the user. We introduce color categories (or focal colors), determine that they are valid, and use them in two experiments. The

MLRS - A lunar/artificial satellite laser ranging facility at the McDonald Observatory

Science.gov (United States)

Shelus, P. J.

1985-01-01

Experience from lunar and satellite laser ranging experiments carried out at McDonald Observatory has been used to design the McDonald Laser Ranging Station (MLRS). The MLRS is a dual-purpose installation designed to obtain observations from the LAGEOS satellite and lunar targets. The instruments used at the station include a telescope assembly 0.76 meters in diameter; a Q-switched doubled neodymium YAG laser with a pulse rate of three nanoseconds; and a GaAs photodetector with Fabry-Perot interferometric filter. A functional diagram of the system is provided. The operating parameters of the instruments are summarized in a table.

On Two Color and CCD Methods for the Determination of Astronomic Position.

Science.gov (United States)

1986-03-14

INTRODUCTION .................................... 2 A. Astroposition Objectives As Related to Two-Color Refractometry .................. 2 B. Results...value for the astronomic longitude and latitude.-_ A. Astroposition Objectives As Related to Two-Color Refractometry The long term objectives consist...The interior of the box was divided into 4 bays containing the telescope, the refractometry optics, the power supplies and the refralctometry

DETECTING LASER SPOT IN SHOOTING SIMULATOR USING AN EMBEDDED CAMERA

OpenAIRE

Soetedjo, Aryuanto; Mahmudi, Ali; Ibrahim Ashari, M.; Ismail Nakhoda, Yusuf

2017-01-01

This paper presents the application of an embedded camera system for detecting laser spot in the shooting simulator. The proposed shooting simulator uses a specific target box, where the circular pattern target is mounted. The embedded camera is installed inside the box to capture the circular pattern target and laser spot image. To localize the circular pattern automatically, two colored solid circles are painted on the target. This technique allows the simple and fast color tracking to trac...

MOONLIGHT: A NEW LUNAR LASER RANGING RETROREFLECTOR AND THE LUNAR GEODETIC PRECESSION

Directory of Open Access Journals (Sweden)

M. Martini

2013-12-01

Full Text Available Since the 1970s Lunar Laser Ranging (LLR to the Apollo Cube Corner Retroreflector (CCR arrays (developed by the University of Maryland, UMD supplied almost all significant tests of General Relativity (Alley et al., 1970; Chang et al., 1971; Bender et al.,1973: possible changes in the gravitational constant, gravitational self-energy, weak equivalence principle, geodetic precession, inverse-square force-law. The LNF group, in fact, has just completed a new measurement of the lunar geodetic precession with Apollo array, with accuracy of 9 × 10−3, comparable to the best measurement to date. LLR has also provided significant information on the composition and origin of the moon. This is the only Apollo experiment still in operation. In the 1970s Apollo LLR arrays contributed a negligible fraction of the ranging error budget. Since the ranging capabilities of ground stations improved by more than two orders of magnitude, now, because of the lunar librations, Apollo CCR arrays dominate the error budget. With the project MoonLIGHT (Moon Laser Instrumentation for General relativity High-accuracy Tests, in 2006 INFN-LNF joined UMD in the development and test of a new-generation LLR payload made by a single, large CCR (100mm diameter unaffected by the effect of librations. With MoonLIGHT CCRs the accuracy of the measurement of the lunar geodetic precession can be improved up to a factor 100 compared to Apollo arrays. From a technological point of view, INFN-LNF built and is operating a new experimental apparatus (Satellite/lunar laser ranging Characterization Facility, SCF and created a new industry-standard test procedure (SCF-Test to characterize and model the detailed thermal behavior and the optical performance of CCRs in accurately laboratory-simulated space conditions, for industrial and scientific applications. Our key experimental innovation is the concurrent measurement and modeling of the optical Far Field Diffraction Pattern (FFDP and the

Theoretical evaluation of measurement uncertainties of two-color pyrometry applied to optical diagnostics

International Nuclear Information System (INIS)

Fu Tairan; Cheng Xiaofang; Yang Zangjian

2008-01-01

We present a theoretical analysis of two-color pyrometry applied to optical diagnostics. A two-color pyrometer built with a single CCD is advantageous due to the simple system design. We evaluate the possibility and degree of ill-conditionness on the basis of measurement uncertainties for different measurement approaches of this two-color system. We classify measurement approaches. The corresponding ill-conditionness criterion is established. The greater the criterion value is, the worse the ill-conditioned degree of solution is. So, the optimum choice of measurement approach for the two-color system is achieved through intercomparison of the criterion values. Numerical examples are also given to illustrate this point. The theoretical analysis not only provides an effective way of evaluating different measurement approaches, but also may help us to better understand the influences that determine the choices between wavelength/waveband measurements and calibration/noncalibration modes for temperature and soot distribution

Research on tunable multiwavelength fiber lasers with two-section birefringence fibers and a nonlinear optical loop

Science.gov (United States)

Chen, Jiao; Tong, Zhengrong; Zhang, Weihua; Xue, Lifang; Pan, Honggang

2018-05-01

Two types of tunable multiwavelength fiber lasers based on two-section polarization maintaining fibers (PMFs) cascaded/in parallel and nonlinear optical loop are proposed and experimentally demonstrated. Two-section cascaded PMFs and two polarization controllers (PCs) form the two-stage Lyot filter, which can generate comb spectrum to achieve multiwavelength output. When two sections of PMFs are in parallel, PCs in two paths are adjusted to change the beam’s polarization to suppress the light of one branch, and then the light of the other branch passes through the cavity. Additionally, a nonlinear optical loop acts as an intensity-dependent component, which can suppress the mode competition to maintain a stable output of multiwavelength lasing. The nonlinear optical loop is made by a 3 dB coupler, a PC3, and a 200 m high nonlinear fiber. Two types of tunable multiwavelength fiber lasers can achieve tuning of the channel space and the number of lasing wavelengths by adjusting PC1 and PC2. The channel space of the multiwavelengh laser can be tuned at nearly 0.4, 0.68, and 0.92 nm. Meanwhile, the spectral range of multiwavelength lasing can be controlled by PC3 in the nonlinear optical loop, and the tuning range of two multiwavelength lasers is about 2.28 and 1.45 nm, respectively.

Lorentz Symmetry Violations from Matter-Gravity Couplings with Lunar Laser Ranging

Science.gov (United States)

Bourgoin, A.; Le Poncin-Lafitte, C.; Hees, A.; Bouquillon, S.; Francou, G.; Angonin, M.-C.

2017-11-01

The standard-model extension (SME) is an effective field theory framework aiming at parametrizing any violation to the Lorentz symmetry (LS) in all sectors of physics. In this Letter, we report the first direct experimental measurement of SME coefficients performed simultaneously within two sectors of the SME framework using lunar laser ranging observations. We consider the pure gravitational sector and the classical point-mass limit in the matter sector of the minimal SME. We report no deviation from general relativity and put new realistic stringent constraints on LS violations improving up to 3 orders of magnitude previous estimations.

Spatial profile of contours inducing long-range color assimilation.

Science.gov (United States)

Devinck, Frédéric; Spillmann, Lothar; Werner, John S

2006-01-01

Color induction was measured using a matching method for two spatial patterns, each composed of double contours. In one pattern (the standard), the contours had sharp edges to induce the Watercolor Effect (WCE); in the other, the two contours had a spatial taper so that the overall profile produced a sawtooth edge, or ramped stimulus. These patterns were chosen based on our previous study demonstrating that the strength of the chromatic WCE depends on a luminance difference between the two contours. Low-pass chromatic mechanisms, unlike bandpass luminance mechanisms, may be expected to be insensitive to the difference between the two spatial profiles. The strength of the watercolor spreading was similar for the two patterns at narrow widths of the contour possibly because of chromatic aberration, but with wider contours, the standard stimulus produced stronger assimilation than the ramped stimulus. This research suggests that luminance-dependent chromatic mechanisms mediate the WCE and that these mechanisms are sensitive to differences in the two spatial profiles of the pattern contours only when they are wide.

Superthin resonator dye laser with THz intermode frequency separation

International Nuclear Information System (INIS)

Rudych, P D; Surovtsev, N V

2014-01-01

Two-color laser irradiation is considered an effective way to pump THz excitations for numerous scientific and applied goals. We present a design for convenient laser source with THz intermode frequency separation. The setup is based on dye laser with superthin resonator pumped by a subnanosecond pulse laser. It was proven that the superthin resonator dye laser is useful, possesses high stability and high energy conversion, and generates narrow laser modes. The ability of this laser to pump CARS processes for THz vibrations is demonstrated. (letter)

The rf sigmameter: A digital phase-locked technique for accurate long-range laser scanning

International Nuclear Information System (INIS)

Zhu, M.; Hall, J.L.

1986-01-01

The authors use a new version of a sigmameter, the two-channel field-widened rf sigmameter, to map optical frequency into the phase of an rf signal. This enables them to lock the laser frequency on the interferometer by using a phase-locked loop (PLL). Controlling the reference phase of the PLL electronically, they are able to scan the laser frequency over a long range step by step or with substeps. The systematic error of each substep is cancelled automatically when the authors change one step (which is ten substeps, for example), and that of each step is cancelled when they change the reference phase by 2π (which corresponds to 256 steps in their scheme)

Two-color quark matter: U(1)A restoration, superfluidity, and quarkyonic phase

International Nuclear Information System (INIS)

Brauner, Tomas; Fukushima, Kenji; Hidaka, Yoshimasa

2009-01-01

We discuss the phase structure of quantum chromodynamics (QCD) with two colors and two flavors of light quarks. This is motivated by the increasing interest in the QCD phase diagram as follows: (1) The QCD critical point search has been under intensive dispute and its location and existence suffer from uncertainty of effective U(1) A symmetry restoration. (2) A new phase called quarkyonic matter is drawing theoretical and experimental attention but it is not clear whether it can coexist with diquark condensation. We point out that two-color QCD is nontrivial enough to contain essential ingredients for (1) and (2) both, and most importantly, is a system without the sign problem in numerical simulations on the lattice. We adopt the two-flavor Nambu-Jona-Lasinio model extended with the two-color Polyakov loop and make quantitative predictions that can be tested by lattice simulations.

Effects of a static electric field on two-color photoassociation between different atoms

International Nuclear Information System (INIS)

Chakraborty, Debashree; Deb, Bimalendu

2014-01-01

We study non-perturbative effects of a static electric field on two-color photoassociation of different atoms. A static electric field induces anisotropy in scattering between two different atoms and hybridizes field-free rotational states of heteronuclear dimers or polar molecules. In a previous paper [D. Chakraborty et al., J. Phys. B 44, 095201 (2011)], the effects of a static electric field on one-color photoassociation between different atoms has been described through field-modified ground-state scattering states, neglecting electric field effects on heteronuclear diatomic bound states. To study the effects of a static electric field on heteronuclear bound states, and the resulting influence on Raman-type two-color photoassociation between different atoms in the presence of a static electric field, we develop a non-perturbative numerical method to calculate static electric field-dressed heteronuclear bound states. We show that the static electric field induced scattering anisotropy as well as hybridization of rotational states strongly influence two-color photoassociation spectra, leading to significant enhancement in PA rate and large shift. In particular, for static electric field strengths of a few hundred kV/cm, two-color PA rate involving high-lying bound states in electronic ground-state increases by several orders of magnitude even in the weak photoassociative coupling regime

Laser-Assisted Removal of Graffiti from Granite: Advantages of the Simultaneous Use of Two Wavelengths

Directory of Open Access Journals (Sweden)

José Santiago Pozo-Antonio

2018-03-01

Full Text Available Currently, removal of graffiti from stone monuments is a particularly challenging task. Lasers, being highly controllable and precise tools with minimal chemical waste, offer a key solution in this respect and a significant amount of research has been dedicated to this subject. Studies related to the laser cleaning of carbonate stones (such as limestone and marble reported the extraction of the graffiti layer, although minimal damage to the substrate can be also detected. Recently, research efforts have been focused on the cleaning of granite, which is a complex stone due to its grained and polymineralic texture. Tests involving different wavelengths indicated that the effectiveness of the cleaning procedure is highly dependent on two components: The composition of the binding medium of the graffiti and the fissure system of the granite. In that direction, the aim of this paper is to investigate and to compare the cleaning effectiveness of two wavelengths emitted from a nanosecond (ns Q-Switched Nd:YAG laser system (IR at 1064 nm and UV at 355 nm, as well as their simultaneous application at different energy density ratios FIR/FUV. The effectiveness of this combined methodology has been shown in several other cases; i.e., for the removal of pollution crusts from carbonate stones (marble. For this study, three different in composition graffiti paints (blue, black, and silver were applied on a fine-grained granite originating from the NW Iberian Peninsula. Prior to the irradiation tests, the damage thresholds of the granite, as well as the extraction thresholds of the graffiti, were determined. Then, several tests involving a variety of parameters (fluence value, number of pulses, etc. were performed and the most satisfactory irradiation conditions from each individual wavelength as well as their combination were compared, based on graffiti extraction level and any damage induced on the granite forming minerals. The analytical techniques used for

Long range coherence in free electron lasers

Science.gov (United States)

Colson, W. B.

1984-01-01

The simple free electron laser (FEL) design uses a static, periodic, transverse magnetic field to undulate relativistic electrons traveling along its axis. This allows coupling to a co-propagating optical wave and results in bunching to produce coherent radiation. The advantages of the FEL are continuous tunability, operation at wavelengths ranging from centimeters to angstroms, and high efficiency resulting from the fact that the interaction region only contains light, relativistic electrons, and a magnetic field. Theoretical concepts and operational principles are discussed.

Two electron response to an intense x-ray free electron laser pulse

Energy Technology Data Exchange (ETDEWEB)

Moore, L R; Parker, J S; Meharg, K J; Armstrong, G S J; Taylor, K T, E-mail: l.moore@qub.ac.u [DAMTP, David Bates Building, Queen' s University Belfast, Belfast, BT7 1NN (United Kingdom)

2009-11-01

New x-ray free electron lasers (FELs) promise an ultra-fast ultra-intense regime in which new physical phenomena, such as double core hole formation in at atom, should become directly observable. Ahead of x-ray FEL experiments, an initial key task is to theoretically explore such fundamental laser-atom interactions and processes. To study the response of a two-electron positive ion to an intense x-ray FEL pulse, our theoretical approach is a direct numerical integration, incorporating non-dipole Hamiltonian terms, of the full six-dimensional time-dependent Schroedinger equation. We present probabilities of double K-shell ionization in the two-electron positive ions Ne{sup 8+} and Ar{sup 16+} exposed to x-ray FEL pulses with frequencies in the range 50 au to 300 au and intensities in the range 10{sup 17} to 10{sup 22} W/cm{sup 2}.

Υ decay to two charm-quark jets as a probe of the color-octet mechanism

International Nuclear Information System (INIS)

Zhang Yujie; Chao Kuangta

2008-01-01

We calculate the decay rate of bottomonium to two charm-quark jets Υ→cc at the tree level and one-loop level including color-singlet and color-octet bb annihilations. We find that the short-distance coefficient of the color-octet piece is much larger than the color-singlet piece, and that the QCD correction will change the end point behavior of the charm quark jet. The color-singlet piece is strongly affected by the one-loop QCD correction. In contrast, the QCD correction to the color-octet piece is weak. Once the experiment can measure the branching ratio and energy distribution of the two charm-quark jets in the Υ decay, the result can be used to test the color-octet mechanism or give a strong constraint on the color-octet matrix elements.

Ultrafast spectral dynamics of dual-color-soliton intracavity collision in a mode-locked fiber laser

Science.gov (United States)

Wei, Yuan; Li, Bowen; Wei, Xiaoming; Yu, Ying; Wong, Kenneth K. Y.

2018-02-01

The single-shot spectral dynamics of dual-color-soliton collisions inside a mode-locked laser is experimentally and numerically investigated. By using the all-optically dispersive Fourier transform, we spectrally unveil the collision-induced soliton self-reshaping process, which features dynamic spectral fringes over the soliton main lobe, and the rebuilding of Kelly sidebands with wavelength drifting. Meanwhile, the numerical simulations validate the experimental observation and provide additional insights into the physical mechanism of the collision-induced spectral dynamics from the temporal domain perspective. It is verified that the dynamic interference between the soliton and the dispersive waves is responsible for the observed collision-induced spectral evolution. These dynamic phenomena not only demonstrate the role of dispersive waves in the sophisticated soliton interaction inside the laser cavity, but also facilitate a deeper understanding of the soliton's inherent stability.

Light Detection and Ranging (LIDAR) From Space - Laser Altimeters

Science.gov (United States)

Sun, Xiaoli

2016-01-01

Light detection and ranging, or lidar, is like radar but atoptical wavelengths. The principle of operation and theirapplications in remote sensing are similar. Lidars havemany advantages over radars in instrument designs andapplications because of the much shorter laser wavelengthsand narrower beams. The lidar transmitters and receiveroptics are much smaller than radar antenna dishes. Thespatial resolution of lidar measurement is much finer thanthat of radar because of the much smaller footprint size onground. Lidar measurements usually give a better temporalresolution because the laser pulses can be much narrowerthan radio frequency (RF) signals. The major limitation oflidar is the ability to penetrate clouds and ground surfaces.

Recent progress in color image intensifier

International Nuclear Information System (INIS)

Nittoh, K.

2010-01-01

A multi-color scintillator based high-sensitive, wide dynamic range and long-life X-ray image intensifier (Ultimage TM ) has been developed. Europium activated Y 2 O 2 S scintillator, emitting red, green and blue wavelength photons of different intensities, is utilized as the output fluorescent screen of the intensifier. By combining this image intensifier with a suitably tuned high sensitive color CCD camera, the sensitivity of the red color component achieved six times higher than that of the conventional image intensifier. Simultaneous emission of a moderate green color and a weak blue color covers different sensitivity regions. This widens the dynamic range by nearly two orders of magnitude. With this image intensifier, it is possible to image complex objects containing various different X-ray transmissions from paper, water or plastic to heavy metals at a time. This color scintillator based image intensifier is widely used in X-ray inspections of various fields. (author)

J/Ψ-production of photon-photon colliders as a probe of the color octet mechanism

International Nuclear Information System (INIS)

Ma, J.P.; McKellar, B.H.J.; Paranavitane, C.B

1997-01-01

We study J/Ψ production at photon-photon colliders, which can be realised with Compton scattering of laser photons at e + e - colliders. We find that the production rate through the color-octet channel is comparable to that through the color-singlet channel. Experimentally the two mechanisms can be studied separately because the processes have different signals. (authors)

Detecting Topological Defect Dark Matter Using Coherent Laser Ranging System

Science.gov (United States)

Yang, Wanpeng; Leng, Jianxiao; Zhang, Shuangyou; Zhao, Jianye

2016-01-01

In the last few decades, optical frequency combs with high intensity, broad optical bandwidth, and directly traceable discrete wavelengths have triggered rapid developments in distance metrology. However, optical frequency combs to date have been limited to determine the absolute distance to an object (such as satellite missions). We propose a scheme for the detection of topological defect dark matter using a coherent laser ranging system composed of dual-combs and an optical clock via nongravitational signatures. The dark matter field, which comprises a defect, may interact with standard model particles, including quarks and photons, resulting in the alteration of their masses. Thus, a topological defect may function as a dielectric material with a distinctive frequency-depend index of refraction, which would cause the time delay of a periodic extraterrestrial or terrestrial light. When a topological defect passes through the Earth, the optical path of long-distance vacuum path is altered, this change in optical path can be detected through the coherent laser ranging system. Compared to continuous wavelength(cw) laser interferometry methods, dual-comb interferometry in our scheme excludes systematic misjudgement by measuring the absolute optical path length. PMID:27389642

Multicolor Scanning Laser Imaging in Diabetic Retinopathy.

Science.gov (United States)

Ahmad, Mohammad S Z; Carrim, Zia Iqbal

2017-11-01

Diabetic retinopathy is a common cause of blindness in individuals younger than 60 years. Screening for retinopathy is undertaken using conventional color fundus photography and relies on the identification of hemorrhages, vascular abnormalities, exudates, and cotton-wool spots. These can sometimes be difficult to identify. Multicolor scanning laser imaging, a new imaging modality, may have a role in improving screening outcomes, as well as facilitating treatment decisions. Observational case series comprising two patients with known diabetes who were referred for further examination after color fundus photography revealed abnormal findings. Multicolor scanning laser imaging was undertaken. Features of retinal disease from each modality were compared. Multicolor scanning laser imaging provides superior visualization of retinal anatomy and pathology, thereby facilitating risk stratification and treatment decisions. Multicolor scanning laser imaging is a novel imaging technique offering the potential for improving the reliability of screening for diabetic retinopathy. Validation studies are warranted.

Autonomous Target Ranging Techniques

DEFF Research Database (Denmark)

Jørgensen, Peter Siegbjørn; Jørgensen, John Leif; Denver, Troelz

2003-01-01

of this telescope, a fast determination of the range to and the motion of the detected targets are important. This is needed in order to prepare the future observation strategy for each target, i.e. when is the closest approach where imaging will be optimal. In order to quickly obtain such a determination two...... ranging strategies are presented. One is an improved laser ranger with an effective range with non-cooperative targets of at least 10,000 km, demonstrated in ground tests. The accuracy of the laser ranging will be approximately 1 m. The laser ranger may furthermore be used for trajectory determination...... of nano-gravity probes, which will perform direct mass measurements of selected targets. The other is triangulation from two spacecraft. For this method it is important to distinguish between detection and tracking range, which will be different for Bering since different instruments are used...

Acquisition Of Three-Dimensional Image Data By A Scanning Laser Range Finder

Science.gov (United States)

Moring, I.; Heikkinen, T.; Myllyla, R.; Kilpela, A. T.

1989-08-01

We describe a 3-D vision system designed and constructed at the Technical Research Centre of Finland in cooperation with the University of Oulu. The system was developed chiefly for geometric measurements of large objects. The system has been operative for about one year, and its performance has been extensively tested. The system consists of three main units: the range finder, the scanner, and the computer. The range finder is based on the direct measurement of the time-of-flight of a laser pulse. The scanner consists of two mirrors driven by moving iron galvanometers; this unit is controlled by servo amplifiers. The computer controls the scanner, transforms the measured coordinates into a Cartesian coordinate system, and serves as a user interface and postprocessing environment.

Satellite laser ranging to low Earth orbiters: orbit and network validation

Science.gov (United States)

Arnold, Daniel; Montenbruck, Oliver; Hackel, Stefan; Sośnica, Krzysztof

2018-04-01

Satellite laser ranging (SLR) to low Earth orbiters (LEOs) provides optical distance measurements with mm-to-cm-level precision. SLR residuals, i.e., differences between measured and modeled ranges, serve as a common figure of merit for the quality assessment of orbits derived by radiometric tracking techniques. We discuss relevant processing standards for the modeling of SLR observations and highlight the importance of line-of-sight-dependent range corrections for the various types of laser retroreflector arrays. A 1-3 cm consistency of SLR observations and GPS-based precise orbits is demonstrated for a wide range of past and present LEO missions supported by the International Laser Ranging Service (ILRS). A parameter estimation approach is presented to investigate systematic orbit errors and it is shown that SLR validation of LEO satellites is not only able to detect radial but also along-track and cross-track offsets. SLR residual statistics clearly depend on the employed precise orbit determination technique (kinematic vs. reduced-dynamic, float vs. fixed ambiguities) but also reveal pronounced differences in the ILRS station performance. Using the residual-based parameter estimation approach, corrections to ILRS station coordinates, range biases, and timing offsets are derived. As a result, root-mean-square residuals of 5-10 mm have been achieved over a 1-year data arc in 2016 using observations from a subset of high-performance stations and ambiguity-fixed orbits of four LEO missions. As a final contribution, we demonstrate that SLR can not only validate single-satellite orbit solutions but also precise baseline solutions of formation flying missions such as GRACE, TanDEM-X, and Swarm.

Research on effect of rough surface on FMCW laser radar range accuracy

Science.gov (United States)

Tao, Huirong

2018-03-01

The non-cooperative targets large scale measurement system based on frequency-modulated continuous-wave (FMCW) laser detection and ranging technology has broad application prospects. It is easy to automate measurement without cooperative targets. However, the complexity and diversity of the surface characteristics of the measured surface directly affects the measurement accuracy. First, the theoretical analysis of range accuracy for a FMCW laser radar was studied, the relationship between surface reflectivity and accuracy was obtained. Then, to verify the effect of surface reflectance for ranging accuracy, a standard tool ball and three standard roughness samples were measured within 7 m to 24 m. The uncertainty of each target was obtained. The results show that the measurement accuracy is found to increase as the surface reflectivity gets larger. Good agreements were obtained between theoretical analysis and measurements from rough surfaces. Otherwise, when the laser spot diameter is smaller than the surface correlation length, a multi-point averaged measurement can reduce the measurement uncertainty. The experimental results show that this method is feasible.

Influence of Surrounding Colors in the Illuminant-Color Mode on Color Constancy

Directory of Open Access Journals (Sweden)

Kazuho Fukuda

2011-05-01

Full Text Available On color constancy, we showed that brighter surrounding colors had greater influence than dim colors (Uchikawa, Kitazawa, MacLeod, Fukuda, 2010 APCV. Increasing luminance of a stimulus causes the change in appearance from the surface-color to the illuminant-color mode. However it is unknown whether the visual system considers such color appearance mode of surrounding colors to achieve color constancy. We investigated the influence of surrounding colors that appeared illuminant on color constancy. The stimulus was composed of a central test stimulus and surrounding six colors: bright and dim red, green and blue. The observers adjusted the chromaticity of the test stimulus to be appeared as an achromatic surface. The luminance balance of three bright surrounding colors was equalized with that of the optimal colors in three illuminant conditions, then, the luminance of one of the three bright colors was varied in the range beyond the critical luminance of color appearance mode transition. The results showed that increasing luminance of a bright surrounding color shifted the observers' achromatic setting toward its chromaticity, but this effect diminished for the surrounding color in the illuminant-color mode. These results suggest that the visual system considers color appearance mode of surrounding colors to accomplish color constancy.

High-order harmonic generation spectra and isolated attosecond pulse generation with a two-color time delayed pulse

International Nuclear Information System (INIS)

Feng Liqiang; Chu Tianshu

2012-01-01

Highlights: ► Investigation of HHG spectra and single isolated attosecond pulse generation. ► Irradiation from a model Ne atom by two-color time delayed pulse. ► Observation of time delay effect and relative phase effect. ► Revelation of the optimal condition for generating isolated attosecond pulse. ► Generation of a single isolated attosecond pulse of 45as. - Abstract: In this paper, we theoretically investigate the delay time effect on the high-order harmonic generation (HHG) when a model Ne atom is exposed to a two-color time delayed pulse, consisting of a 5fs/800 nm fundamental field and a 20fs/2000 nm controlling field. It shows that the HHG spectra are strongly sensitive to the delay time between the two laser fields, in particular, for the zero carrier-envelope phase (CEP) φ case (corresponding to the 800 nm fundamental field), the maximum cutoff energy has been achieved at zero delay time. However, with the introduction of the CEP (φ = 180°), the delay effect on HHG is changed, exhibiting a ‘U’ structure harmonic emission from −1 T to 1 T. In addition, the combinations of different controlling pulse frequencies and pulse intensities have also been considered, showing the similar results as the original controlling field case, but with some characteristics. Finally, by properly superposing the optimal harmonic spectrum, an isolated 45as pulse is generated without phase compensation.

Processing of Color Words Activates Color Representations

Science.gov (United States)

Richter, Tobias; Zwaan, Rolf A.

2009-01-01

Two experiments were conducted to investigate whether color representations are routinely activated when color words are processed. Congruency effects of colors and color words were observed in both directions. Lexical decisions on color words were faster when preceding colors matched the color named by the word. Color-discrimination responses…

Laser synthesis of hybrid nanoparticles for biomedicine

Science.gov (United States)

Avetissian, H. K.; Lalayan, A. A.

2018-04-01

The extraordinary properties of size-tunable nanoparticles (NPs) have given rise to their widespread applications in Nanophotonics, Biomedicine, Plasmonics etc. Semiconductor and metal NPs have found a number of significant applications in the modern biomedicine due to ultrasmall sizes (1-10 nm) and the size-dependent flexibility of their optical properties. In the present work passive Q-switched Nd:YAG pulsed laser was used to synthesize NPs by method of laser ablation in different liquids. For cases of hybrid metal NPs we have demonstrated that plasmon resonance can be modified and tuned from the plasmon resonances of pure metal NPs. The shifted plasmon resonance frequency at 437 nm for Au-Ag hybrid NPs, and 545 nm for Au-Cu hybrid NPs have been observed. Effectiveness of biotissue ablation in the case of the tissue sample that colored with metal NPs was approximately on 4-5 times larger than for the sample with non-colored area. Laser welding for deep-located biotissue layers colored by metal NPs has been realized. The luminescence properties of the colloidal hybrid Si-Ni nanoparticles' system fabricated by pulsed laser ablation are also considered. The red-shifted photoluminescence of this system has been registered in the blue range of the spectrum because of the Stark effect in the Coulomb field of the charged Ni nanoparticles. Summarizing, the knowledge of peculiarities of optical properties of hybrid NPs is very important for biomedical applications. More complex nanoassemblies can be easily constructed by the presented technique of laser synthesis of colloidal QDs including complexes of NPs of different materials.

Process of optical excitation and relaxation of color center in synthetic diamond and its application to optoelectronics

International Nuclear Information System (INIS)

Nishida, Yoshio

1989-01-01

Irradiation of high-pressure synthesized diamond is carried out by using a nuclear reactor or a linac. Then, the effect of annealing on the color centers is observed. A study is made to identify different color centers and to provide techniques to control their introduction. Investigations cover the relation of color center formation with annealing temperature, dependence of color center formation on radiation dose, migration of H3 center and hydrogen, and applicability of five different color centers to optoelectronics. Next, a study is made of the formation and relaxation of the nitrogen vacancy (NV) center in a metastable excited state produced by optical excitation. An optical gain is essential to provide laser. Optical amplification is measured at the vibronic emission band of the NV center. An increase in absorption is detected, indicating that the NV center will not provide laser. In the optical excitation-relaxation process, the relaxation proceeds via a metastable state. Finally, hole burning of ZPL of the NV center is observed in the temperature range from 20K to 80K, and some of its features are described. (N.K.)

Two-Photon Pumped Synchronously Mode-Locked Bulk GaAs Laser

Science.gov (United States)

Cao, W. L.; Vaucher, A. M.; Ling, J. D.; Lee, C. H.

1982-04-01

Pulses 7 picoseconds or less in duration have been generated from a bulk GaAs crystal by a synchronous mode-locking technique. The GaAs crystal was optically pumped by two-photon absorption of the emission from a mode-locked Nd:glass laser. Two-photon absorption as the means of excitation increases the volume of the gain medium by increasing the pene-tration depth of the pump intensity, enabling generation of intra-cavity pulses with peak power in the megawatt range. Tuning of the wavelength of the GaAs emission is achieved by varying the temperature. A tuning range covering 840 nm to 885 nm has been observed over a temperature range from 97°K to 260°K. The intensity of the GaAs emission has also been observed to decrease as the temperature of the crystal is increased.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

Science.gov (United States)

Follett, R. K.; Shaw, J. G.; Myatt, J. F.; Palastro, J. P.; Short, R. W.; Froula, D. H.

2018-03-01

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ˜0.7 % laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. This allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Study on Dental Treatment with YAG Laser (1st Report): Temperature of Dental Tissue Irradiated with Laser Beam

OpenAIRE

上田, 隆司; 山田, 啓司; 古本, 達明

2000-01-01

The flash temperature of a dental hard tissue irradiated with pulsed Nd:YAG laser is measured using a two-color pyrometer with an optical fiber. This pyrometer consists of a chalcogenide optical fiber and a laminated infrared detector. The influence of the laser power on the temperature of the dental tissue is investigated, and the relationship between the laser power and the removal volume of the dental tissue is obtained. In order to examine the thermal damage on the dental tissue, hardness...

Fault-Tolerant Conflict-Free Coloring

DEFF Research Database (Denmark)

Abam, Mohammad; de Berg, Mark; Poon, Sheung-Hung

2008-01-01

] introduced conict-free colorings, as de ned next, to model this problem. Let S be a set of n objects, and let R be a, possibly in nite, family of ranges. In this paper, we only consider objects and ranges that are subsets of R2, or sometimes of R1. For a range r 2 R, let S(r) be the subset of objects from S...... intersecting the range r. A conict-free coloring (CF-coloring) of S with respect to R is a coloring of S with the following property [5]: for any range r 2 R for which S(r) 6= ; there is an object o 2 S(r) with a unique color in S(r), that is, with a color not used by any other object in S(r). Trivially......, a conict-free coloring always exists: just assign a different color to each object. However, one would like to nd a coloring with only few colors. This is the conict-free coloring problem. Note that if we take S to be a set of disks|namely, the regions within reach of each base station|and we take R...

Lifetime predictions for dimmable two-channel drivers for color tuning luminaires

Energy Technology Data Exchange (ETDEWEB)

Davis, Lynn [RTI International, Research Triangle Park, NC (United States); Smith, Aaron [Finelite Inc., Union City, CA (United States); Clark, Terry [Finelite Inc., Union City, CA (United States); Mills, Karmann [RTI International, Research Triangle Park, NC (United States); Perkins, Curtis [RTI International, Research Triangle Park, NC (United States)

2017-05-30

Two-channel tunable white lighting (TWL) systems represent the next wave of solid-state lighting (SSL) systems and promise flexibility in light environment while maintaining the high reliability and luminous efficacy expected with SSL devices. TWL systems utilize LED assemblies consisting of two different LED spectra (i.e., often a warm white assembly and a cool white assembly) that are integrated into modules. While these systems provide the ability to adjust the lighting spectrum to match the physiology needs of the task at hand, they also are a potentially more complex lighting system from a performance and reliability perspective. We report an initial study on the reliability performance of such lighting systems including an examination of the lumen maintenance and chromaticity stability of warm white and cool white LED assemblies and the multi-channel driver that provides power to the assemblies. Accelerated stress tests including operational bake tests conducted at 75°C and 95°C were used to age the LED modules, while more aggressive temperature and humidity tests were used for the drivers in this study. Small differences in the performance between the two LED assemblies were found and can be attributed to the different phosphor chemistries. The lumen maintenances of both LED assemblies were excellent. The warm white LED assemblies were found to shift slightly in the green color direction over time while the cool white LED assemblies shifted slightly in the yellow color direction. The net result of these chromaticity shifts is a small, barely perceptible reduction in the tuning range after 6,000 hours of exposure to an accelerating elevated temperature of 75°C.

Diode pumped solid state laser by two diodes

International Nuclear Information System (INIS)

Li Mingzhong; Zhang Xiaomin; Liang Yue; Man Yongzai; Zhou Pizhang

1995-01-01

A Nd: YLF laser is pumped by home-made quantum well diode lasers. Datum of laser output energy 60 μJ and peak power 120 mw are observed at wavelength 1.047 μm. On the same pumping condition, the output power synchronously pumped by two diodes is higher than the total output power pumped by two diodes separately. The fluctuation is <3%. The results agree with theoretical analysis

Color ferromagnetic vacuum states in QCD and two-loop energy densities

International Nuclear Information System (INIS)

Nielsen, H.B.; Ninomiya, M.

1979-12-01

Two-loop energy densities of color ferromagnetic states are obtained using the β-function calculated to two-loop approximation and the exact formula for the energy density of such a state. This is used to derive bounds on the MIT bag constant correcting the previous bound in one-loop approximation. For a constant field color ferromagnetic ansatz state the bound on the QCD scale parameter Λsub(p) 3 -vacuum ansatz with two-loop and instanton correction gives Λsub(p)<= 0.16 GeV. Tt is stressed that the 'perturbative vacuum', which is identified with the inside bag state is a somewhat ill defined concept due to a path-dependence in the integral giving the energy density. (Auth.)

Digitally controlled chirped pulse laser for sub-terahertz-range fiber structure interrogation.

Science.gov (United States)

Chen, Zhen; Hefferman, Gerald; Wei, Tao

2017-03-01

This Letter reports a sweep velocity-locked laser pulse generator controlled using a digital phase-locked loop (DPLL) circuit. This design is used for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with millimeter-level spatial resolution. A distributed feedback laser was employed to generate chirped laser pulses via injection current modulation. A DPLL circuit was developed to lock the optical frequency sweep velocity. A high-quality linearly chirped laser pulse with a frequency excursion of 117.69 GHz at an optical communication band was demonstrated. The system was further adopted to interrogate a continuously distributed sub-terahertz-range fiber structure (sub-THz-fs) for sensing applications. A strain test was conducted in which the sub-THz-fs showed a linear response to longitudinal strain change with predicted sensitivity. Additionally, temperature testing was conducted in which a heat source was used to generate a temperature distribution along the fiber structure to demonstrate its distributed sensing capability. A Gaussian temperature profile was measured using the described system and tracked in real time, as the heat source was moved.

Medical application of laser hair removal

International Nuclear Information System (INIS)

Fadlalla, Alwalled Hussein Ataalmannan

2015-12-01

The use of laser in medical treatment has become of paramount importance proportional to what has high therapeutic privileges such as speed and accuracy in penetrating tissues and high quality especially when used in hair removal which is the subject of our study, this laser operates cards may cause some change in the color of the skin when used in a manner that is correct ratio of the thermal impact force in the laser hair removal process, or if it is exposed directly to his eye. This study is a comparison between the physical properties of laser of lasers used in hair removal, according to previous studies to be the basis for the benefit of doctors who use lasers for hair removal. The aim of this study was to study the effect of laser hair removal using the Nd: YAG laser with a wavelength 1064 nm as well as the risks airing from the assessment. The aim of this study was to identify the appropriate laser energy that absorbed in the hair follicle with a dark color and the appropriate thermal effect occurs to vaporize the follicle cell, a 40 J/cm"2 is to be significant without side effects for healthy tissue. In this study doses for a few laser beam is considered when compared to previous studies. Laser danger to the patient during the operation increases with increasing laser energy emitted during treatment. Laser hair removal by the user and energy emitted by wavelength of the laser device also depends on the hair color and roughness as well as skin color. (Author)

A color hierarchy for automatic target selection.

Directory of Open Access Journals (Sweden)

Illia Tchernikov

Full Text Available Visual processing of color starts at the cones in the retina and continues through ventral stream visual areas, called the parvocellular pathway. Motion processing also starts in the retina but continues through dorsal stream visual areas, called the magnocellular system. Color and motion processing are functionally and anatomically discrete. Previously, motion processing areas MT and MST have been shown to have no color selectivity to a moving stimulus; the neurons were colorblind whenever color was presented along with motion. This occurs when the stimuli are luminance-defined versus the background and is considered achromatic motion processing. Is motion processing independent of color processing? We find that motion processing is intrinsically modulated by color. Color modulated smooth pursuit eye movements produced upon saccading to an aperture containing a surface of coherently moving dots upon a black background. Furthermore, when two surfaces that differed in color were present, one surface was automatically selected based upon a color hierarchy. The strength of that selection depended upon the distance between the two colors in color space. A quantifiable color hierarchy for automatic target selection has wide-ranging implications from sports to advertising to human-computer interfaces.

Mechanical properties and polymerization shrinkage of composite resins light-cured using two different lasers.

Science.gov (United States)

Kim, Tae-Wan; Lee, Jang-Hoon; Jeong, Seung-Hwa; Ko, Ching-Chang; Kim, Hyung-Il; Kwon, Yong Hoon

2015-04-01

The purpose of the present study was to investigate the usefulness of 457 and 473 nm lasers for the curing of composite resins during the restoration of damaged tooth cavity. Monochromaticity and coherence are attractive features of laser compared with most other light sources. Better polymerization of composite resins can be expected. Eight composite resins were light cured using these two lasers and a light-emitting diode (LED) light-curing unit (LCU). To evaluate the degrees of polymerization achieved, polymerization shrinkage and flexural and compressive properties were measured and compared. Polymerization shrinkage values by 457 and 473 nm laser, and LED ranged from 10.9 to 26.8, from 13.2 to 26.1, and from 11.5 to 26.3 μm, respectively. The values by 457 nm laser was significantly different from those by 473 and LED LCU (p0.05). For the tested LCUs, no specific LCU could consistently achieve highest strength and modulus from the specimens tested. Two lasers (457 and 473 nm) can polymerize composite resins to the level that LED LCU can achieve despite inconsistent trends of polymerization shrinkage and flexural and compressive properties of the tested specimens.

Plasmonic laser printing for functional metasurfaces

DEFF Research Database (Denmark)

Zhu, Xiaolong; Carstensen, M. S.; Vannahme, Christoph

2016-01-01

Recently, we show a method of color printing on nanoimprinted plasmonic metasurfaces using laser post-writing. Laser pulses induce transient local heat generation that leads to melting and reshaping of the imprinted nanostructures [1]. Depending on the laser pulse energy density, different surface...... morphologies that support different plasmonic resonances can be created. This technology creates a laser printer capable of producing color images with a resolution up to 127,000 DPI. With tailored trains of laser pulses, multiple optical states are flatiron onto the metasurface film with a nanoscale...

Testing Gravity via Lunar Laser Ranging: Maximizing Data Quality

Science.gov (United States)

Murphy, Thomas

We propose to continue leading-edge observations with the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO), in an effort to subject gravity to the most stringent tests yet. APOLLO has delivered a dramatic improvement in the measurement of the lunar orbit: now at the millimeter level. Yet incomplete models are thus far unable to confirm the accuracy. We therefore seek to build a calibration system to ensure that APOLLO meets its millimeter measurement goal. Gravity--the most evident force of nature--is in fact the weakest of the fundamental forces, and consequently the most poorly tested. Einstein’s general relativity, which is currently our best description of gravity, is fundamentally incompatible with quantum mechanics and is likely to be replaced by a more complete theory in the future. A modified theory would predict small deviations in the solar system that could have profound consequences for our understanding of the Universe as a whole. Lunar laser ranging (LLR), in which short laser pulses launched from a telescope are bounced off of reflectors placed on the Moon by U.S. astronauts and Soviet landers, has for decades produced some of the leading tests of gravity by mapping the shape of the lunar orbit to high precision. These include tests of the strong equivalence principle, the time-rate-ofchange of Newton’s gravitational constant, gravitomagnetism, the inverse-square law, and many others. Among the attributes that contribute to APOLLO’s superior observations, routine ranging to all five lunar reflectors on timescales of minutes dramatically improves our ability to gauge lunar orientation and body distortion. This information produces insights into the interior structure and dynamics of the Moon, allowing a more precise determination of the path for the Moon’s center of mass, lending to tests of fundamental gravity. Simultaneously, higher precision range measurements, together with data from a superconducting gravimeter at the

Stokes image reconstruction for two-color microgrid polarization imaging systems.

Science.gov (United States)

Lemaster, Daniel A

2011-07-18

The Air Force Research Laboratory has developed a new microgrid polarization imaging system capable of simultaneously reconstructing linear Stokes parameter images in two colors on a single focal plane array. In this paper, an effective method for extracting Stokes images is presented for this type of camera system. It is also shown that correlations between the color bands can be exploited to significantly increase overall spatial resolution. Test data is used to show the advantages of this approach over bilinear interpolation. The bounds (in terms of available reconstruction bandwidth) on image resolution are also provided.

双色激光激励对空气中太赫兹辐射增强的研究%THz emission enhancement in air by two-color laser excitation

Institute of Scientific and Technical Information of China (English)

戴厚梅; 孙伟; 汪东亮

2015-01-01

Photocurrent model was used to study THz emission enhancement when air was irradiated by two‐color laser pulses with introducing another 400 nm laser pulse .The second order ionization of nitrogen and the collision between the electrons and the surrounding ions and molecules were taken in‐to account .The results show that the symmetry of laser field is broken by the introduction of the sec‐ond harmonic 400 nm laser ,w hich leads to the production of non‐zero DC electron current and greater intensity of T Hz emission in the far field .%利用光电流模型模拟研究在泵浦光中引入400 nm倍频光对空气中太赫兹辐射的增强情况，其中空气中氮气离化过程考虑到二阶离化，同时考虑电子在运动过程中与周围离子、分子的碰撞。结果表明，400 nm激光的引入打破了原激光电场的对称性，导致了光电流中漂移成分的产生，大大增强了最后的太赫兹波输出强度。

Colored Contact Lens Dangers

Medline Plus

Full Text Available ... about the members of the eye-care team . Consumer warning about the improper use of colored contact ... a laser pointer several times, according to a report published this month in the New England Journal ...

Colored Contact Lens Dangers

Medline Plus

Full Text Available ... Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center Global Ophthalmology Guide Eye Health ... Leer en Español: Peligros asociados con los lentes de contacto de color Sep. 26, ...

An absolute distance interferometer with two external cavity diode lasers

International Nuclear Information System (INIS)

Hartmann, L; Meiners-Hagen, K; Abou-Zeid, A

2008-01-01

An absolute interferometer for length measurements in the range of several metres has been developed. The use of two external cavity diode lasers allows the implementation of a two-step procedure which combines the length measurement with a variable synthetic wavelength and its interpolation with a fixed synthetic wavelength. This synthetic wavelength is obtained at ≈42 µm by a modulation-free stabilization of both lasers to Doppler-reduced rubidium absorption lines. A stable reference interferometer is used as length standard. Different contributions to the total measurement uncertainty are discussed. It is shown that the measurement uncertainty can considerably be reduced by correcting the influence of vibrations on the measurement result and by applying linear regression to the quadrature signals of the absolute interferometer and the reference interferometer. The comparison of the absolute interferometer with a counting interferometer for distances up to 2 m results in a linearity error of 0.4 µm in good agreement with an estimation of the measurement uncertainty

Broadband Laser Ranging for Position Measurements in Shock Physics Experiments

Science.gov (United States)

Rhodes, Michelle; Bennett, Corey; Daykin, Edward; Younk, Patrick; Lalone, Brandon; Kostinski, Natalie

2017-06-01

Broadband laser ranging (BLR) is a recently developed measurement system that provides an attractive option for determining the position of shock-driven surfaces. This system uses broadband, picosecond (or femtosecond) laser pulses and a fiber interferometer to measure relative travel time to a target and to a reference mirror. The difference in travel time produces a delay difference between pulse replicas that creates a spectral beat frequency. The spectral beating is recorded in real time using a dispersive Fourier transform and an oscilloscope. BLR systems have been designed that measure position at 12.5-40 MHz with better than 100 micron accuracy over ranges greater than 10 cm. We will give an overview of the basic operating principles of these systems. Prepared by LLNL under Contract DE-AC52-07NA27344, by LANL under Contract DE-AC52-06NA25396, and by NSTec Contract DE-AC52-06NA25946.

Color categories and color appearance

Science.gov (United States)

Webster, Michael A.; Kay, Paul

2011-01-01

We examined categorical effects in color appearance in two tasks, which in part differed in the extent to which color naming was explicitly required for the response. In one, we measured the effects of color differences on perceptual grouping for hues that spanned the blue–green boundary, to test whether chromatic differences across the boundary were perceptually exaggerated. This task did not require overt judgments of the perceived colors, and the tendency to group showed only a weak and inconsistent categorical bias. In a second case, we analyzed results from two prior studies of hue scaling of chromatic stimuli (De Valois, De Valois, Switkes, & Mahon, 1997; Malkoc, Kay, & Webster, 2005), to test whether color appearance changed more rapidly around the blue–green boundary. In this task observers directly judge the perceived color of the stimuli and these judgments tended to show much stronger categorical effects. The differences between these tasks could arise either because different signals mediate color grouping and color appearance, or because linguistic categories might differentially intrude on the response to color and/or on the perception of color. Our results suggest that the interaction between language and color processing may be highly dependent on the specific task and cognitive demands and strategies of the observer, and also highlight pronounced individual differences in the tendency to exhibit categorical responses. PMID:22176751

Measuring Earth: Current status of the GRACE Follow-On Laser Ranging Interferometer

Science.gov (United States)

Schütze, Daniel; LRI Team

2016-05-01

The GRACE mission that was launched in 2002 has impressively proven the feasibility of low-orbit satellite-to-satellite tracking for Earth gravity observations. Especially mass transport related to Earth's hydrological system could be well resolved both spatially and temporally. This allows to study processes such as polar ice sheet decline and ground water depletion in great detail. Owing to GRACE's success, NASA and GFZ will launch the successor mission GRACE Follow-On in 2017. In addition to the microwave ranging system, GRACE Follow-On will be the first mission to use a Laser Ranging Interferometer as technology demonstrator to track intersatellite distance changes with unprecedented precision. This new ranging device inherits some of the technologies which have been developed for the future spaceborne gravitational wave detector LISA. I will present the architecture of the Laser Ranging Interferometer, point out similarities and differences to LISA, and conclude with the current status of the flight hardware production.

Calibration between a Laser Range Scanner and an Industrial Robot Manipulator

DEFF Research Database (Denmark)

Andersen, Thomas Timm; Andersen, Nils Axel; Ravn, Ole

2014-01-01

In this paper we present a method for findingthe transformation between a laser scanner and a robotmanipulator. We present the design of a flat calibration targetthat can easily fit between a laser scanner and a conveyor belt,making the method easily implementable in a manufacturingline.We prove...... that the method works by simulating a range ofdifferent orientations of the target, and performs an extensivenumerical evaluation of the targets design parameters to estab-lish the optimal values as well as the worst-case accuracy ofthe method...

Optical properties of color centers in calcium-stabilized gadolinium gallium garnets

International Nuclear Information System (INIS)

Pogatshnik, G.J.; Cain, L.S.; Chen, Y.; Evans, B.D.

1991-01-01

The addition of small amounts of calcium during the crystal growth of large-diameter, gadolinium gallium garnet (GGG) crystals creates color centers that absorb in the near-uv region of the spectrum. Ultraviolet and γ-ray irradiation of the crystals produced changes in the intensities of the uv color-center bands along with a broad absorption throughout the visible spectrum. The color center that gives rise to an absorption band at 350 nm serves as a photoionizable donor center so that uv excitation results in a visible coloration of the crystals. The effects of oxidation and reduction treatments on the strength of the color-center bands and on the radiation response of the material were examined. Photoluminescence bands were observed in both reduced GGG crystals as well as crystals that were irradiated with neutrons. Visible coloration is likely to occur during flashlamp pumping of laser rods that utilize large-diameter GGG crystals as the laser host. The changes in the optical properties of the material under uv excitation indicate that the addition of small amounts of calcium to assist in the growth of large-diameter crystals is likely to result in the degradation of laser performance

Broadband laser ranging development at the DOE Labs

Science.gov (United States)

Bennett, Corey V.; La Lone, Brandon M.; Younk, Patrick W.; Daykin, Ed P.; Rhodes, Michelle A.

2017-02-01

Broadband Laser Ranging (BLR) is a new diagnostic being developed in collaboration across multiple USA Dept. of Energy (DOE) facilities. Its purpose is to measure the precise position of surfaces and particle clouds moving at speeds of a few kilometers per second. The diagnostic uses spectral interferometry to encode distance into a modulation in the spectrum of pulses from a mode-locked fiber laser and uses a dispersive Fourier transformation to map the spectral modulation into time. This combination enables recording of range information in the time domain on a fast oscilloscope every 25-80 ns. Discussed here are some of the hardware design issues, system tradeoffs, calibration issues, and experimental results. BLR is being developed as an add-on to conventional Photonic Doppler Velocimetry (PDV) systems because PDV often yields incomplete information when lateral velocity components are present, or when there are drop-outs in the signal amplitude. In these cases, integration of the velocity from PDV can give incorrect displacement results. Experiments are now regularly fielded with over 100 channels of PDV, and BLR is being developed in a modular way to enable high channel counts of BLR and PDV recorded from the same probes pointed at the same target location. In this way instruments, will independently record surface velocity and distance information along the exact same path.

Femtosecond two-photon laser-induced fluorescence of krypton for high-speed flow imaging.

Science.gov (United States)

Wang, Yejun; Capps, Cade; Kulatilaka, Waruna D

2017-02-15

Ultrashort-pulse (femtosecond-duration) two-photon laser-induced fluorescence (fs-TPLIF) of an inert gas tracer krypton (Kr) is investigated. A detailed spectroscopic study of fluorescence channels followed by the 5p'←←4p excitation of Kr at 204.1 nm is reported. The experimental line positions in the 750-840 nm emission region agree well with the NIST Atomic Spectra Database. The present work provides an accurate listing of relative line strengths in this spectral region. In the range of laser pulse energies investigated, a quadratic dependence was observed between the Kr-TPLIF signal and the laser pulse energy. The single-laser-shot 2D TPLIF images recorded in an unsteady jet demonstrate the potential of using fs excitation at 204.1 nm for mixing and flow diagnostic studies using Kr as an inert gas tracer.

Imprinting on empty hard gelatin capsule shells containing titanium dioxide by application of the UV laser printing technique.

Science.gov (United States)

Hosokawa, Akihiro; Kato, Yoshiteru; Terada, Katsuhide

2014-08-01

The purpose of this study was to examine the application of ultraviolet (UV) laser irradiation to printing hard gelatin capsule shells containing titanium dioxide (TiO2) and to clarify how the color strength of the printing by the laser could be controlled by the power of the irradiated laser. Hard gelatin capsule shells containing 3.5% TiO2 were used in this study. The capsules were irradiated with pulsed UV laser at a wavelength of 355 nm. The color strength of the printed capsule was determined by a spectrophotometer as total color difference (dE). The capsules could be printed gray by the UV laser. The formation of many black particles which were agglomerates of oxygen-defected TiO2 was associated with the printing. In the relationship between laser peak power of a pulse and dE, there were two inflection points. The lower point was the minimal laser peak power to form the black particles and was constant regardless of the dosage forms, for example film-coated tablets, soft gelatin capsules and hard gelatin capsules. The upper point was the minimal laser peak power to form micro-bubbles in the shells and was variable with the formulation. From the lower point to the upper point, the capsules were printed gray and the dE of the printing increased linearly with the laser peak power. Hard gelatin capsule shells containing TiO2 could be printed gray using the UV laser printing technique. The color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

Efficient infrared (≈1.9-2.0 μm) laser operation in color-defect-free Tm:NaGd(MoO4)2 crystal

Science.gov (United States)

Han, X.; Rico, M.; Serrano, M. D.; Cascales, C.; Zaldo, C.

2013-04-01

Color-defect-free 5 at.% Tm:NaGd(MoO4)2 crystals have been grown in a Na2MoO4/Na2Mo2O7 flux. Using a hemispherical optical cavity and pumping at λ = 794.5 nm with a Ti-sapphire laser, up to 850 mW of output power at λ ≈ 1900 nm was obtained at 300 K with an output coupler transmission of 8%. In the cw regime, the slope efficiency versus absorbed power was η = 45% and the pump power laser threshold was ≈180 mW. The laser was tunable from 1875 to 1975 nm and the emission had a FWHM bandwidth ≈20 nm, indicating the potential for ultrashort laser pulse generation.

The picosecond laser for tattoo removal.

Science.gov (United States)

Hsu, Vincent M; Aldahan, Adam S; Mlacker, Stephanie; Shah, Vidhi V; Nouri, Keyvan

2016-11-01

The prevalence of tattoos continues to grow as modern society's stigma towards this form of body art shifts towards greater acceptance. Approximately one third of Americans aged 18-25 and 40 % of Americans aged 26-40 are tattooed. As tattoos continue to rise in popularity, so has the demand for an effective method of tattoo removal such as lasers. The various colors of tattoo inks render them ideal targets for specific lasers using the principle of selective photothermolysis. Traditional laser modalities employed for tattoo removal operate on pulse durations in the nanosecond domain. However, this pulse duration range is still too long to effectively break ink into small enough particles. Picosecond (10 -12 ) lasers have emerged at the forefront of laser tattoo removal due to their shorter pulse lengths, leading to quicker heating of the target chromophores, and consequently, more effective tattoo clearance. Recent studies have cited more effective treatment outcomes using picosecond lasers. Future comparative studies between picosecond lasers of various settings are necessary to determine optimal laser parameters for tattoo clearance.

Photofragmentation of colloidal solutions of gold nanoparticles under femtosecond laser pulses in IR and visible ranges

International Nuclear Information System (INIS)

Danilov, P A; Zayarnyi, D A; Ionin, A A; Kudryashov, S I; Makarov, S V; Rudenko, A A; Saraeva, I N; Yurovskikh, V I; Lednev, V N; Pershin, S M

2015-01-01

The specific features of photofragmentation of sols of gold nanoparticles under focused femtosecond laser pulses in IR (1030 nm) and visible (515 nm) ranges is experimentally investigated. A high photofragmentation efficiency of nanoparticles in the waist of a pulsed laser beam in the visible range (at moderate radiation scattering) is demonstrated; this efficiency is related to the excitation of plasmon resonance in nanoparticles on the blue shoulder of its spectrum, in contrast to the regime of very weak photofragmentation in an IR-laser field of comparable intensity. Possible mechanisms of femtosecond laser photofragmentation of gold nanoparticles are discussed. (extreme light fields and their applications)

Spectral BRDF measurements of metallic samples for laser processing applications

International Nuclear Information System (INIS)

Vitali, L; Fustinoni, D; Gramazio, P; Niro, A

2015-01-01

The spectral bidirectional reflectance distribution function (BRDF) of metals plays an important role in industrial processing involving laser-surface interaction. In particular, in laser metal machining, absorbance is strongly dependent on the radiation incidence angle as well as on finishing and contamination grade of the surface, and in turn it can considerably affect processing results. Very recently, laser radiation is also used to structure metallic surfaces, in order to produce many particular optical effects, ranging from a high level polishing to angular color shifting. Of course, full knowledge of the spectral BRDF of these structured layers makes it possible to infer reflectance or color for any irradiation and viewing angles. In this paper, we present Vis-NIR spectral BRDF measurements of laser-polished metallic, opaque, flat samples commonly employed in such applications. The resulting optical properties seem to be dependent on the atmospheric composition during the polishing process in addition to the roughness. The measurements are carried out with a Perkin Elmer Lambda 950 double-beam spectrophotometer, equipped with the Absolute Reflectance/Transmittance Analyzer (ARTA) motorized goniometer. (paper)

COLORS OF ELLIPTICALS FROM GALEX TO SPITZER

Energy Technology Data Exchange (ETDEWEB)

Schombert, James M., E-mail: jschombe@uoregon.edu [Department of Physics, University of Oregon, Eugene, OR 97403 (United States)

2016-12-01

Multi-color photometry is presented for a large sample of local ellipticals selected by morphology and isolation. The sample uses data from the Galaxy Evolution Explorer ( GALEX ), Sloan Digital Sky Survey (SDSS), Two Micron All-Sky Survey (2MASS), and Spitzer to cover the filters NUV , ugri , JHK and 3.6 μ m. Various two-color diagrams, using the half-light aperture defined in the 2MASS J filter, are very coherent from color to color, meaning that galaxies defined to be red in one color are always red in other colors. Comparison to globular cluster colors demonstrates that ellipticals are not composed of a single age, single metallicity (e.g., [Fe/H]) stellar population, but require a multi-metallicity model using a chemical enrichment scenario. Such a model is sufficient to explain two-color diagrams and the color–magnitude relations for all colors using only metallicity as a variable on a solely 12 Gyr stellar population with no evidence of stars younger than 10 Gyr. The [Fe/H] values that match galaxy colors range from −0.5 to +0.4, much higher (and older) than population characteristics deduced from Lick/IDS line-strength system studies, indicating an inconsistency between galaxy colors and line indices values for reasons unknown. The NUV colors have unusual behavior, signaling the rise and fall of the UV upturn with elliptical luminosity. Models with blue horizontal branch tracks can reproduce this behavior, indicating the UV upturn is strictly a metallicity effect.

COLORS OF ELLIPTICALS FROM GALEX TO SPITZER

International Nuclear Information System (INIS)

Schombert, James M.

2016-01-01

Multi-color photometry is presented for a large sample of local ellipticals selected by morphology and isolation. The sample uses data from the Galaxy Evolution Explorer ( GALEX ), Sloan Digital Sky Survey (SDSS), Two Micron All-Sky Survey (2MASS), and Spitzer to cover the filters NUV , ugri , JHK and 3.6 μ m. Various two-color diagrams, using the half-light aperture defined in the 2MASS J filter, are very coherent from color to color, meaning that galaxies defined to be red in one color are always red in other colors. Comparison to globular cluster colors demonstrates that ellipticals are not composed of a single age, single metallicity (e.g., [Fe/H]) stellar population, but require a multi-metallicity model using a chemical enrichment scenario. Such a model is sufficient to explain two-color diagrams and the color–magnitude relations for all colors using only metallicity as a variable on a solely 12 Gyr stellar population with no evidence of stars younger than 10 Gyr. The [Fe/H] values that match galaxy colors range from −0.5 to +0.4, much higher (and older) than population characteristics deduced from Lick/IDS line-strength system studies, indicating an inconsistency between galaxy colors and line indices values for reasons unknown. The NUV colors have unusual behavior, signaling the rise and fall of the UV upturn with elliptical luminosity. Models with blue horizontal branch tracks can reproduce this behavior, indicating the UV upturn is strictly a metallicity effect.

Two-laser thermal-lens determination of phosphorus in silicon

International Nuclear Information System (INIS)

Grishko, V.I.; Gol'dshtein, M.M.; Grishko, V.P.; Yudelevich, I.G.

1986-01-01

Laser thermal-lens spectrophotometry is a high-sensitivity method of measuring absorptivity, where the signal is the relative intensity change at the beam center after passage through the medium, which absorbs at the laser wavelength. The two-lens method is discussed here which employs a high-power laser to induce the lens, while the absorptivity is measured from the intensity change in the beam from a continous wave low-power test laser at a wavelength different from that for the inducing one. This paper uses two-laser thermal-lens techniques to determine phosphorus in silicon. Phosphorus is determined as the ionic association of molybdophosphoric acid with auramine

1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

Energy Technology Data Exchange (ETDEWEB)

Sadeev, T., E-mail: tagir@mailbox.tu-berlin.de; Arsenijević, D.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin (Germany); Franke, D.; Kreissl, J.; Künzel, H. [Heinrich-Hertz-Institut, Einsteinufer 37, 10587 Berlin (Germany)

2015-01-19

Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning.

1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

International Nuclear Information System (INIS)

Sadeev, T.; Arsenijević, D.; Bimberg, D.; Franke, D.; Kreissl, J.; Künzel, H.

2015-01-01

Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning

Digital color imaging

CERN Document Server

Fernandez-Maloigne, Christine; Macaire, Ludovic

2013-01-01

This collective work identifies the latest developments in the field of the automatic processing and analysis of digital color images.For researchers and students, it represents a critical state of the art on the scientific issues raised by the various steps constituting the chain of color image processing.It covers a wide range of topics related to computational color imaging, including color filtering and segmentation, color texture characterization, color invariant for object recognition, color and motion analysis, as well as color image and video indexing and retrieval. <

Two plus blue equals green: Grapheme-color synesthesia allows cognitive access to numerical information via color

Science.gov (United States)

McCarthy, J. Daniel; Barnes, Lianne N.; Alvarez, Bryan D.; Caplovitz, Gideon Paul

2013-01-01

In grapheme-color synesthesia, graphemes (e.g., numbers or letters) evoke color experiences. It is generally reported that the opposite is not true: colors will not generate experiences of graphemes or their associated information. However, recent research has provided evidence that colors can implicitly elicit symbolic representations of associated graphemes. Here, we examine if these representations can be cognitively accessed. Using a mathematical verification task replacing graphemes with color patches, we find that synesthetes can verify such problems with colors as accurately as with graphemes. Doing so, however, takes time: ~250ms per color. Moreover, we find minimal reaction time switch-costs for switching between computing with graphemes and colors. This demonstrates that given specific task demands, synesthetes can cognitively access numerical information elicited by physical colors, and they do so as accurately as with graphemes. We discuss these results in the context of possible cognitive strategies used to access the information. PMID:24100131

Ranging error analysis of single photon satellite laser altimetry under different terrain conditions

Science.gov (United States)

Huang, Jiapeng; Li, Guoyuan; Gao, Xiaoming; Wang, Jianmin; Fan, Wenfeng; Zhou, Shihong

2018-02-01

Single photon satellite laser altimeter is based on Geiger model, which has the characteristics of small spot, high repetition rate etc. In this paper, for the slope terrain, the distance of error's formula and numerical calculation are carried out. Monte Carlo method is used to simulate the experiment of different terrain measurements. The experimental results show that ranging accuracy is not affected by the spot size under the condition of the flat terrain, But the inclined terrain can influence the ranging error dramatically, when the satellite pointing angle is 0.001° and the terrain slope is about 12°, the ranging error can reach to 0.5m. While the accuracy can't meet the requirement when the slope is more than 70°. Monte Carlo simulation results show that single photon laser altimeter satellite with high repetition rate can improve the ranging accuracy under the condition of complex terrain. In order to ensure repeated observation of the same point for 25 times, according to the parameters of ICESat-2, we deduce the quantitative relation between the footprint size, footprint, and the frequency repetition. The related conclusions can provide reference for the design and demonstration of the domestic single photon laser altimetry satellite.

Oceanographic applications of laser technology

Science.gov (United States)

Hoge, F. E.

1988-01-01

Oceanographic activities with the Airborne Oceanographic Lidar (AOL) for the past several years have primarily been focussed on using active (laser induced pigment fluorescence) and concurrent passive ocean color spectra to improve existing ocean color algorithms for estimating primary production in the world's oceans. The most significant results were the development of a technique for selecting optimal passive wavelengths for recovering phytoplankton photopigment concentration and the application of this technique, termed active-passive correlation spectroscopy (APCS), to various forms of passive ocean color algorithms. Included in this activity is use of airborne laser and passive ocean color for development of advanced satellite ocean color sensors. Promising on-wavelength subsurface scattering layer measurements were recently obtained. A partial summary of these results are shown.

High-power cw laser bars of the 750 – 790-nm wavelength range

International Nuclear Information System (INIS)

Degtyareva, N S; Kondakov, S A; Mikayelyan, G T; Gorlachuk, P V; Ladugin, M A; Marmalyuk, Aleksandr A; Ryaboshtan, Yu L; Yarotskaya, I V

2013-01-01

We have developed the effective design of semiconductor heterostructures, which allow one to fabricate cw laser diodes emitting in the 750 – 790-nm spectral range. The optimal conditions for fabrication of GaAsP/AlGaInP/GaAs heterostructures by MOCVD have been determined. It is shown that the use of quantum wells with a precisely defined quantity mismatch reduces the threshold current density and increases the external differential efficiency. The results of studies of characteristics of diode laser bars fabricated from these heterostructures are presented. (lasers)

Quantitative measurement of binocular color fusion limit for non-spectral colors.

Science.gov (United States)

Jung, Yong Ju; Sohn, Hosik; Lee, Seong-il; Ro, Yong Man; Park, Hyun Wook

2011-04-11

Human perception becomes difficult in the event of binocular color fusion when the color difference presented for the left and right eyes exceeds a certain threshold value, known as the binocular color fusion limit. This paper discusses the binocular color fusion limit for non-spectral colors within the color gamut of a conventional LCD 3DTV. We performed experiments to measure the color fusion limit for eight chromaticity points sampled from the CIE 1976 chromaticity diagram. A total of 2480 trials were recorded for a single observer. By analyzing the results, the color fusion limit was quantified by ellipses in the chromaticity diagram. The semi-minor axis of the ellipses ranges from 0.0415 to 0.0923 in terms of the Euclidean distance in the u'v´ chromaticity diagram and the semi-major axis ranges from 0.0640 to 0.1560. These eight ellipses are drawn on the chromaticity diagram. © 2011 Optical Society of America

Two-Laser Interference Visible to the Naked Eye

Science.gov (United States)

Kawalec, Tomasz; Bartoszek-Bober, Dobroslawa

2012-01-01

An experimental setup allowing the observation of two-laser interference by the naked eye is described. The key concept is the use of an electronic phase lock between two external cavity diode lasers. The experiment is suitable both for undergraduate and graduate students, mainly in atomic physics laboratories. It gives an opportunity for…

ColorMoves: Optimizing Color's Potential for Exploration and Communication of Data

Science.gov (United States)

Samsel, F.

2017-12-01

Color is the most powerful perceptual channel available for exposing and communicating data. Most visualizations are rendered in one of a handful of common colormaps - the rainbow, cool-warm, heat map and viridis. These maps meet the basic criteria for encoding data - perceptual uniformity and reasonable discriminatory power. However, as the size and complexity of data grows, our need to optimize the potential of color grows. The ability to expose greater detail and differentiate between multiple variables becomes ever more important. To meet this need we have created ColorMoves, an interactive colormap construction tool that enables scientists to quickly and easily align a concentration contrast with the data ranges of interest. Perceptual research tells us that luminance is the strongest contrast and thus provides the highest degree of perceptual discrimination. However, the most commonly used colormaps contain a limited range of luminance contrast. ColorMoves enables interactive constructing colormaps enabling one to distribute the luminance where is it most needed. The interactive interface enables optimal placement of the color scales. The ability to watch the changes on ones data, in real time makes precision adjustment quick and easy. By enabling more precise placement and multiple ranges of luminance one can construct colomaps containing greater discriminatory power. By selecting from the wide range of color scale hues scientists can create colormaps intuitive to their subject. ColorMoves is comprised of four main components: a set of 40 color scales; a histogram of the data distribution; a viewing area showing the colormap on your data; and the controls section. The 40 color scales span the spectrum of hues, saturation levels and value distributions. The histogram of the data distribution enables placement of the color scales in precise locations. The viewing area show is the impact of changes on the data in real time. The controls section enables export

Two dimensional finite element thermal model of laser surface glazing for H13 tool steel

Science.gov (United States)

Kabir, I. R.; Yin, D.; Naher, S.

2016-10-01

A two dimensional (2D) transient thermal model with line-heat-source was developed by Finite Element Method (FEM) for laser surface glazing of H13 tool steel using commercial software-ANSYS 15. The geometry of the model was taken as a transverse circular cross-section of cylindrical specimen. Two different power levels (300W, 200W) were used with 0.2mm width of laser beam and 0.15ms exposure time. Temperature distribution, heating and cooling rates, and the dimensions of modified surface were analysed. The maximum temperatures achieved were 2532K (2259°C) and 1592K (1319°C) for laser power 300W and 200W respectively. The maximum cooling rates were 4.2×107 K/s for 300W and 2×107 K/s for 200W. Depths of modified zone increased with increasing laser power. From this analysis, it can be predicted that for 0.2mm beam width and 0.15ms time exposer melting temperature of H13 tool steel is achieved within 200-300W power range of laser beam in laser surface glazing.

Laser Digital Cinema

Science.gov (United States)

Takeuchi, Eric B.; Flint, Graham W.; Bergstedt, Robert; Solone, Paul J.; Lee, Dicky; Moulton, Peter F.

2001-03-01

Electronic cinema projectors are being developed that use a digital micromirror device (DMDTM) to produce the image. Photera Technologies has developed a new architecture that produces truly digital imagery using discrete pulse trains of red, green, and blue light in combination with a DMDTM where in the number of pulses that are delivered to the screen during a given frame can be defined in a purely digital fashion. To achieve this, a pulsed RGB laser technology pioneered by Q-Peak is combined with a novel projection architecture that we refer to as Laser Digital CameraTM. This architecture provides imagery wherein, during the time interval of each frame, individual pixels on the screen receive between zero and 255 discrete pulses of each color; a circumstance which yields 24-bit color. Greater color depth, or increased frame rate is achievable by increasing the pulse rate of the laser. Additionally, in the context of multi-screen theaters, a similar architecture permits our synchronously pulsed RGB source to simultaneously power three screens in a color sequential manner; thereby providing an efficient use of photons, together with the simplifications which derive from using a single DMDTM chip in each projector.

Close-range laser scanning in forests: towards physically based semantics across scales.

Science.gov (United States)

Morsdorf, F; Kükenbrink, D; Schneider, F D; Abegg, M; Schaepman, M E

2018-04-06

Laser scanning with its unique measurement concept holds the potential to revolutionize the way we assess and quantify three-dimensional vegetation structure. Modern laser systems used at close range, be it on terrestrial, mobile or unmanned aerial platforms, provide dense and accurate three-dimensional data whose information just waits to be harvested. However, the transformation of such data to information is not as straightforward as for airborne and space-borne approaches, where typically empirical models are built using ground truth of target variables. Simpler variables, such as diameter at breast height, can be readily derived and validated. More complex variables, e.g. leaf area index, need a thorough understanding and consideration of the physical particularities of the measurement process and semantic labelling of the point cloud. Quantified structural models provide a framework for such labelling by deriving stem and branch architecture, a basis for many of the more complex structural variables. The physical information of the laser scanning process is still underused and we show how it could play a vital role in conjunction with three-dimensional radiative transfer models to shape the information retrieval methods of the future. Using such a combined forward and physically based approach will make methods robust and transferable. In addition, it avoids replacing observer bias from field inventories with instrument bias from different laser instruments. Still, an intensive dialogue with the users of the derived information is mandatory to potentially re-design structural concepts and variables so that they profit most of the rich data that close-range laser scanning provides.

An overview of Broadband Laser Ranging Architecture and Measurement Considerations

Science.gov (United States)

Daykin, Edward; La Lone, Brandon; Miller, Edward; Younk, Patrick; Bennett, Corey; Catenacci, Jared; LLNL BLR Development Group Collaboration; LANL BLR Development Group Collaboration

2017-06-01

Broadband Laser Ranging (BLR) is a developmental diagnostic intended to measure the position of rapidly moving surfaces in combination with optical velocimetry. Design and employment of a BLR diagnostic on dynamic experiments requires consideration for both the inherent measurement system tradeoffs as well as architectural choices appropriate to the nature of investigation. The diagnostic uses spectral interferometry to measure distance by mapping femtosecond laser pulses to the time domain via chromatic dispersion within the fiber-optic architecture. The system parameters and governing equations that describe measurement range, resolution, and Doppler sensitivity will be discussed. We will also briefly review the impact of diagnostic architectural choices including: nature of interferometer, Interferometric dispersion matching, optical amplification, integration of optical velocimetry, BLR calibration, and field operability. To summarize we will present the architectural and operational approach currently being pursued by NSTec within an on-going collaboration between NSTec, Lawrence Livermore and Los Alamos National Labs. This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy.

True Yellow Light-Emitting Diodes as Phosphor for Tunable Color-Rendering Index Laser-Based White Light

KAUST Repository

Janjua, Bilal; Ng, Tien Khee; Zhao, Chao; Prabaswara, Aditya; Consiglio, Giuseppe Bernardo; Priante, Davide; Shen, Chao; Elafandy, Rami T.; Anjum, Dalaver H.; Alhamoud, Abdullah A.; Alatawi, Abdullah A.; Yang, Yang; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.

2016-01-01

An urgent challenge for the lighting research community is the lack of efficient optical devices emitting in between 500 and 600 nm, resulting in the “green-yellow gap”. In particular, true green (∼555 nm) and true yellow (∼590 nm), along with blue and red, constitute four technologically important colors. The III-nitride material system, being the most promising choice of platform to bridge this gap, still suffers from high dislocation density and poor crystal quality in realizing high-power, efficient devices. Particularly, the high polarization fields in the active region of such 2D quantum confined structures prevent efficient recombination of carriers. Here we demonstrate a true yellow nanowire (NW) light emitting diode (LED) with peak emission of 588 nm at 29.5 A/cm2 (75 mA in a 0.5 × 0.5 mm2 device) and a low turn-on voltage of ∼2.5 V, while having an internal quantum efficiency of 39%, and without “efficiency droop” up to an injection current density of 29.5 A/cm2. By mixing yellow light from a NW LED in reflective configuration with that of a red, green, and blue laser diode (LD), white light with a correlated color temperature of ∼6000 K and color-rendering index of 87.7 was achieved. The nitride-NW-based device offers a robust, long-term stability for realizing yellow light emitters for tunable color-rendering index solid-state lighting, on a scalable, low-cost, foundry-compatible titanium/silicon substrate, suitable for industry uptake.

True Yellow Light-Emitting Diodes as Phosphor for Tunable Color-Rendering Index Laser-Based White Light

KAUST Repository

Janjua, Bilal

2016-10-11

An urgent challenge for the lighting research community is the lack of efficient optical devices emitting in between 500 and 600 nm, resulting in the “green-yellow gap”. In particular, true green (∼555 nm) and true yellow (∼590 nm), along with blue and red, constitute four technologically important colors. The III-nitride material system, being the most promising choice of platform to bridge this gap, still suffers from high dislocation density and poor crystal quality in realizing high-power, efficient devices. Particularly, the high polarization fields in the active region of such 2D quantum confined structures prevent efficient recombination of carriers. Here we demonstrate a true yellow nanowire (NW) light emitting diode (LED) with peak emission of 588 nm at 29.5 A/cm2 (75 mA in a 0.5 × 0.5 mm2 device) and a low turn-on voltage of ∼2.5 V, while having an internal quantum efficiency of 39%, and without “efficiency droop” up to an injection current density of 29.5 A/cm2. By mixing yellow light from a NW LED in reflective configuration with that of a red, green, and blue laser diode (LD), white light with a correlated color temperature of ∼6000 K and color-rendering index of 87.7 was achieved. The nitride-NW-based device offers a robust, long-term stability for realizing yellow light emitters for tunable color-rendering index solid-state lighting, on a scalable, low-cost, foundry-compatible titanium/silicon substrate, suitable for industry uptake.

The precision of today's satellite laser ranging systems

Science.gov (United States)

Dunn, Peter J.; Torrence, Mark H.; Hussen, Van S.; Pearlman, Michael R.

1993-06-01

Recent improvements in the accuracy of modern satellite laser ranging (SLR) systems are strengthened by the new capability of many instruments to track an increasing number of geodetic satellite targets without significant scheduling conflict. This will allow the refinement of some geophysical parameters, such as solid Earth tidal effects and GM, and the improved temporal resolution of others, such as Earth orientation and station position. Better time resolution for the locations of fixed observatories will allow us to monitor more subtle motions at the stations, and transportable systems will be able to provide indicators of long term trends with shorter occupations. If we are to take advantage of these improvements, care must be taken to preserve the essential accuracy of an increasing volume of range observations at each stage of the data reduction process.

Multi-GNSS orbit determination using satellite laser ranging

Science.gov (United States)

Bury, Grzegorz; Sośnica, Krzysztof; Zajdel, Radosław

2018-04-01

Galileo, BeiDou, QZSS, and NavIC are emerging global navigation satellite systems (GNSSs) and regional navigation satellite systems all of which are equipped with laser retroreflector arrays for range measurements. This paper summarizes the GNSS-intensive tracking campaigns conducted by the International Laser Ranging Service and provides results from multi-GNSS orbit determination using solely SLR observations. We consider the whole constellation of GLONASS, all active Galileo, four BeiDou satellites: 1 MEO, 3 IGSO, and one QZSS. We analyze the influence of the number of SLR observations on the quality of the 3-day multi-GNSS orbit solution. About 60 SLR observations are needed for obtaining MEO orbits of sufficient quality with the root mean square (RMS) of 3 cm for the radial component when compared to microwave-based orbits. From the analysis of a minimum number of tracking stations, when considering the 3-day arcs, 5 SLR stations do not provide a sufficient geometry of observations. The solution obtained using ten stations is characterized with RMS of 4, 9, and 18 cm in the radial, along-track, and cross-track direction, respectively, for MEO satellites. We also investigate the impact of the length of orbital arc on the quality of SLR-derived orbits. Hence, 5- and 7-day arcs constitute the best solution, whereas 3-day arcs are of inferior quality due to an insufficient number of SLR observations and 9-day arcs deteriorate the along-track component. The median RMS from the comparison between 7-day orbital arcs determined using SLR data with microwave-based orbits assumes values in the range of 3-4, 11-16, and 15-27 cm in radial, along-track, and cross-track, respectively, for MEO satellites. BeiDou IGSO and QZSS are characterized by RMS values higher by a factor of 8 and 24, respectively, than MEO orbits.

Feasibility of LED-Assisted CMOS Camera: Contrast Estimation for Laser Tattoo Treatment

Directory of Open Access Journals (Sweden)

Ngot Thi Pham

2018-04-01

Full Text Available Understanding the residual tattoo ink in skin after laser treatment is often critical for achieving good clinical outcomes. The current study aims to investigate the feasibility of a light-emitting diode (LED-assisted CMOS camera to estimate the relative variations in tattoo contrast after the laser treatment. Asian mice were tattooed using two color inks (black and red. The LED illumination was a separate process from the laser tattoo treatment. Images of the ink tattoos in skin were acquired under the irradiation of three different LED colors (red, green, and blue for pre- and post-treatment. The degree of contrast variation due to the treatment was calculated and compared with the residual tattoo distribution in the skin. The black tattoo demonstrated that the contrast consistently decreased after the laser treatment for all LED colors. However, the red tattoo showed that the red LED yielded an insignificant contrast whereas the green and blue LEDs induced a 30% (p < 0.001 and 26% (p < 0.01 contrast reduction between the treatment conditions, respectively. The proposed LED-assisted CMOS camera can estimate the relative variations in the image contrast before and after the laser tattoo treatment.

Stability of optically injected two-state quantum-dot lasers

Energy Technology Data Exchange (ETDEWEB)

Meinecke, Stefan; Lingnau, Benjamin; Roehm, Andre; Luedge, Kathy [Institut fuer Theoretische Physik, Technische Universitaet Berlin (Germany)

2017-12-15

Simultaneous two-state lasing is a unique property of semiconductor quantum-dot (QD) lasers. This not only changes steady-state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single-state laser devices, we find a strong suppression of dynamical instabilities in two-state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all-optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Stability of optically injected two-state quantum-dot lasers

International Nuclear Information System (INIS)

Meinecke, Stefan; Lingnau, Benjamin; Roehm, Andre; Luedge, Kathy

2017-01-01

Simultaneous two-state lasing is a unique property of semiconductor quantum-dot (QD) lasers. This not only changes steady-state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single-state laser devices, we find a strong suppression of dynamical instabilities in two-state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all-optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Tests of a two-color interferometer and polarimeter for ITER density measurements

Science.gov (United States)

Van Zeeland, M. A.; Carlstrom, T. N.; Finkenthal, D. K.; Boivin, R. L.; Colio, A.; Du, D.; Gattuso, A.; Glass, F.; Muscatello, C. M.; O'Neill, R.; Smiley, M.; Vasquez, J.; Watkins, M.; Brower, D. L.; Chen, J.; Ding, W. X.; Johnson, D.; Mauzey, P.; Perry, M.; Watts, C.; Wood, R.

2017-12-01

A full-scale 120 m path length ITER toroidal interferometer and polarimeter (TIP) prototype, including an active feedback alignment system, has been constructed and undergone initial testing at General Atomics. In the TIP prototype, two-color interferometry is carried out at 10.59 μm and 5.22 μm using a CO2 and quantum cascade laser (QCL) respectively while a separate polarimetry measurement of the plasma induced Faraday effect is made at 10.59 μm. The polarimeter system uses co-linear right and left-hand circularly polarized beams upshifted by 40 and 44 MHz acousto-optic cells respectively, to generate the necessary beat signal for heterodyne phase detection, while interferometry measurements are carried out at both 40 MHz and 44 MHz for the CO2 laser and 40 MHz for the QCL. The high-resolution phase information is obtained using an all-digital FPGA based phase demodulation scheme and precision clock source. The TIP prototype is equipped with a piezo tip/tilt stage active feedback alignment system responsible for minimizing noise in the measurement and keeping the TIP diagnostic aligned indefinitely on its 120 m beam path including as the ITER vessel is brought from ambient to operating temperatures. The prototype beam path incorporates translation stages to simulate ITER motion through a bake cycle as well as other sources of motion or misalignment. Even in the presence of significant motion, the TIP prototype is able to meet ITER’s density measurement requirements over 1000 s shot durations with demonstrated phase resolution of 0.06° and 1.5° for the polarimeter and vibration compensated interferometer respectively. TIP vibration compensated interferometer measurements of a plasma have also been made in a pulsed radio frequency device and show a line-integrated density resolution of δ {nL}=3.5× {10}17 m-2.

The Design Concept of the First Mobile Satellite Laser Ranging System (ARGO-M in Korea

Directory of Open Access Journals (Sweden)

Jung Hyun Jo

2011-03-01

Full Text Available Korea Astronomy and Space Science Institute (KASI launched the development project of two satellite laser ranging (SLR systems in early 2008 after the government fund approval of the SLR systems in 2007. One mobile SLR system and one permanent SLR station will be developed with the completion of the project. The main objectives of these systems will be focused on the Space Geodetic researches. A system requirement review was held in the second half of the same year. Through the following system design review meeting and other design reviews, many unsolved technical and engineering issues would be discussed and resolved. However, the design of the mobile SLR system is a corner stone of whole project. The noticeable characteristics of Korea’s first SLR system are 1 use of light weight main mirror, 2 design of compact optical assembly, 3 use of KHz laser pulse, 4 use of commercial laser generator, 5 remote operation capability, 6 automatic tracking, 7 state of art operation system, etc. In this paper, the major user requirement and pre-defined specification are presented and discussed.

Synchronization scenario of two distant mutually coupled semiconductor lasers

DEFF Research Database (Denmark)

Mulet, Josep; Mirasso, Claudio; Heil, Tilmann

2004-01-01

We present numerical and experimental investigations of the synchronization of the coupling-induced instabilities in two distant mutually coupled semiconductor lasers. In our experiments, two similar Fabry-Perot lasers are coupled via their coherent optical fields. Our theoretical framework is ba...

Color Categories and Color Appearance

Science.gov (United States)

Webster, Michael A.; Kay, Paul

2012-01-01

We examined categorical effects in color appearance in two tasks, which in part differed in the extent to which color naming was explicitly required for the response. In one, we measured the effects of color differences on perceptual grouping for hues that spanned the blue-green boundary, to test whether chromatic differences across the boundary…

Nondébridement of laser char after two carbon dioxide laser passes results in faster reepithelialization

DEFF Research Database (Denmark)

Collawn, Sherry S; Woods, Anne; Couchman, John R

2003-01-01

Skin repair following laser injury can be accelerated by using techniques that promote rapid reepithelialization. In this article, the benefit of intraoperative nondébridement of laser debris after two laser passes is discussed. After carbon dioxide laser resurfacing of the face, skin specimens w...

Super-resolution imaging of ciliary microdomains in isolated olfactory sensory neurons using a custom two-color stimulated emission depletion microscope

Science.gov (United States)

Meyer, Stephanie A.; Ozbay, Baris N.; Potcoava, Mariana; Salcedo, Ernesto; Restrepo, Diego; Gibson, Emily A.

2016-06-01

We performed stimulated emission depletion (STED) imaging of isolated olfactory sensory neurons (OSNs) using a custom-built microscope. The STED microscope uses a single pulsed laser to excite two separate fluorophores, Atto 590 and Atto 647N. A gated timing circuit combined with temporal interleaving of the different color excitation/STED laser pulses filters the two channel detection and greatly minimizes crosstalk. We quantified the instrument resolution to be ˜81 and ˜44 nm, for the Atto 590 and Atto 647N channels. The spatial separation between the two channels was measured to be under 10 nm, well below the resolution limit. The custom-STED microscope is incorporated onto a commercial research microscope allowing brightfield, differential interference contrast, and epifluorescence imaging on the same field of view. We performed immunolabeling of OSNs in mice to image localization of ciliary membrane proteins involved in olfactory transduction. We imaged Ca2+-permeable cyclic nucleotide gated (CNG) channel (Atto 594) and adenylyl cyclase type III (ACIII) (Atto 647N) in distinct cilia. STED imaging resolved well-separated subdiffraction limited clusters for each protein. We quantified the size of each cluster to have a mean value of 88±48 nm and 124±43 nm, for CNG and ACIII, respectively. STED imaging showed separated clusters that were not resolvable in confocal images.

Crustal Strain Observation Using a Two-Color Interferometer with Accurate Correction of Refractive Index of Air

Directory of Open Access Journals (Sweden)

Souichi Telada

2014-07-01

Full Text Available A highly accurate two-color interferometer with automatic correction of the refractive index of air was developed for crustal strain observation. The two-color interferometer, which can measure a geometrical distance of approximately 70 m, with a relative resolution of 2 × 10−9, clearly detected a change in strain due to earth tides in spite of optical measurement in air. Moreover, a large strain quake due to an earthquake could be observed without disturbing the measurement. We demonstrated the advantages of the two-color interferometer in air for geodetic observation.

Comparison of retina damage thresholds simulating the femtosecond-laser in situ keratomileusis (fs-LASIK) process with two laser systems in the CW- and fs-regime

Science.gov (United States)

Sander, M.; Minet, O.; Zabarylo, U.; Müller, M.; Tetz, M. R.

2012-04-01

The femtosecond-laser in situ keratomileusis procedure affords the opportunity to correct ametropia by cutting transparent corneal tissue with ultra-short laser pulses. Thereby the tissue cut is generated by a laser-induced optical breakdown in the cornea with ultra-short laser pulses in the near-infrared range. Compared to standard procedures such as photorefractive keratectomy and laser in-situ keratomileusis with the excimer laser, where the risk potential for the eye is low due to the complete absorption of ultraviolet irradiation from corneal tissue, only a certain amount of the pulse energy is deposited in the cornea during the fs-LASIK process. The remaining energy propagates through the eye and interacts with the retina and the strong absorbing tissue layers behind. The objective of the presented study was to determine and compare the retina damage thresholds during the fs-LASIK process simulated with two various laser systems in the CW- and fs-regime.

Versatile single-molecule multi-color excitation and detection fluorescence setup for studying biomolecular dynamics

KAUST Repository

Sobhy, M. A.

2011-11-07

Single-molecule fluorescence imaging is at the forefront of tools applied to study biomolecular dynamics both in vitro and in vivo. The ability of the single-molecule fluorescence microscope to conduct simultaneous multi-color excitation and detection is a key experimental feature that is under continuous development. In this paper, we describe in detail the design and the construction of a sophisticated and versatile multi-color excitation and emission fluorescence instrument for studying biomolecular dynamics at the single-molecule level. The setup is novel, economical and compact, where two inverted microscopes share a laser combiner module with six individual laser sources that extend from 400 to 640 nm. Nonetheless, each microscope can independently and in a flexible manner select the combinations, sequences, and intensities of the excitation wavelengths. This high flexibility is achieved by the replacement of conventional mechanical shutters with acousto-optic tunable filter (AOTF). The use of AOTF provides major advancement by controlling the intensities, duration, and selection of up to eight different wavelengths with microsecond alternation time in a transparent and easy manner for the end user. To our knowledge this is the first time AOTF is applied to wide-field total internal reflection fluorescence (TIRF) microscopy even though it has been commonly used in multi-wavelength confocal microscopy. The laser outputs from the combiner module are coupled to the microscopes by two sets of four single-mode optic fibers in order to allow for the optimization of the TIRF angle for each wavelength independently. The emission is split into two or four spectral channels to allow for the simultaneous detection of up to four different fluorophores of wide selection and using many possible excitation and photoactivation schemes. We demonstrate the performance of this new setup by conducting two-color alternating excitation single-molecule fluorescence resonance energy

Really Large Scale Computer Graphic Projection Using Lasers and Laser Substitutes

Science.gov (United States)

Rother, Paul

1989-07-01

This paper reflects on past laser projects to display vector scanned computer graphic images onto very large and irregular surfaces. Since the availability of microprocessors and high powered visible lasers, very large scale computer graphics projection have become a reality. Due to the independence from a focusing lens, lasers easily project onto distant and irregular surfaces and have been used for amusement parks, theatrical performances, concert performances, industrial trade shows and dance clubs. Lasers have been used to project onto mountains, buildings, 360° globes, clouds of smoke and water. These methods have proven successful in installations at: Epcot Theme Park in Florida; Stone Mountain Park in Georgia; 1984 Olympics in Los Angeles; hundreds of Corporate trade shows and thousands of musical performances. Using new ColorRayTM technology, the use of costly and fragile lasers is no longer necessary. Utilizing fiber optic technology, the functionality of lasers can be duplicated for new and exciting projection possibilities. The use of ColorRayTM technology has enjoyed worldwide recognition in conjunction with Pink Floyd and George Michaels' world wide tours.

Sub-micrometric surface texturing of AZ31 Mg-alloy through two-beam direct laser interference patterning with a ns-pulsed green fiber laser

Science.gov (United States)

Furlan, Valentina; Biondi, Marco; Demir, Ali Gökhan; Pariani, Giorgio; Previtali, Barbara; Bianco, Andrea

2017-11-01

Two-beam direct laser interference patterning (DLIP) is the method that employs two beams and provides control over the pattern geometry by regulating the angle between the beams and the wavelength of the beam. Despite the simplistic optical arrangement required for the method, the feasibility of sub-micrometric patterning of a surface depends on the correct manipulation of the process parameters, especially in the case of metallic materials. Magnesium alloys, from this point of view, exhibit further difficulty in processability due to low melting point and high reactivity. With biocompatibility and biodegradability features, Mg-alloy implants can take further advantage of surface structuring for tailoring the biological behaviour. In this work, a two-beam DLIP setup has been developed employing an industrial grade nanosecond-pulsed fiber laser emitting at 532 nm. The high repetition rate and ramped pulse profile provided by the laser were exploited for a more flexible control over the energy content deposited over the heat-sensitive Mg-alloy. The paper describes the strategies developed for controlling ramped laser emission at 20 kHz repetition rate. The process feasibility window was assessed within a large range of parameters. Within the feasibility window, a complete experimental plan was applied to investigate the effect of main laser process parameters on the pattern dimensions. Periodic surface structures with good definition down to 580 nm ± 20 nm spacing were successfully produced.

Laser surgery - skin

Science.gov (United States)

... Bleeding Problem not going away Infection Pain Scarring Skin color changes Some laser surgery is done when you are asleep and ... TG, Elston DM, eds. Andrews' Diseases of the Skin: Clinical ... lasers, lights, and tissue interactions. In: Hruza GJ, Avram ...

The effect of coherent phase control in (e, 2e) process of a hydrogenic ion in presence of a two colour laser field

Energy Technology Data Exchange (ETDEWEB)

Sinha, C; Chattopadhyay, A; Deb, S Ghosh, E-mail: chand_sin@hotmail.co, E-mail: arpita.chattopadhyay@gmail.co, E-mail: srabanti.ghosh@gmail.co [Theoretical Physics Department, Indian Association for the Cultivation of Science, Kolkata - 700032 (India)

2009-11-01

We study the coherent phase control (CPC) of ionization (TDCS) of a hydrogenic ion under the action of a bichromatic laser field consisting of a fundamental frequency and one of its harmonics by varying the phase difference between the two components. A significant reduction is noted particularly in the recoil peak (dominant for the ionic target) with the two color field as compared to the monochromatic one, while the modification of the binary peak is comparatively less. The CPC is found to be more effective for the odd harmonics than the even one.

Laser discrimination by stimulated emission of a phosphor

Science.gov (United States)

Mathur, V. K.; Chakrabarti, K.

1991-01-01

A method for discriminating sources of UV, near infrared, and far infrared laser radiation was discovered. This technology is based on the use of a single magnesium sulfide phosphor doubly doped with rare earth ions, which is thermally/optically stimulated to generate colors correlatable to the incident laser radiation. The phosphor, after initial charging by visible light, exhibits green stimulated luminescence when exposed to a near infrared source (Nd: YAG laser). On exposure to far infrared sources (CO2 laser) the phosphor emission changes to orange color. A UV laser produces both an orange red as well as green color. A device using this phosphor is useful for detecting the laser and for discriminating between the near infrared, far infrared, and UV lasers. The technology is also capable of infrared laser diode beam profiling since the radiation source leaves an imprint on the phosphor that can be photographed. Continued development of the technology offers potential for discrimination between even smaller bandwidths within the infrared spectrum, a possible aid to communication or wavemixing devices that need to rapidly identify and process optical signals.

Earth rotation, station coordinates and orbit determination from satellite laser ranging

Science.gov (United States)

Murata, Masaaki

The Project MERIT, a special program of international colaboration to Monitor Earth Rotation and Intercompare the Techniques of observation and analysis, has come to an end with great success. Its major objective was to evaluate the ultimate potential of space techniques such as VLBI and satellite laser ranging, in contrast with the other conventional techniques, in the determination of rotational dynamics of the earth. The National Aerospace Laboratory (NAL) has officially participated in the project as an associate analysis center for satellite laser technique for the period of the MERIT Main Campaign (September 1983-October 1984). In this paper, the NAL analysis center results are presented.

Upgrading NASA/DOSE laser ranging system control computers

Science.gov (United States)

Ricklefs, Randall L.; Cheek, Jack; Seery, Paul J.; Emenheiser, Kenneth S.; Hanrahan, William P., III; Mcgarry, Jan F.

1993-01-01

Laser ranging systems now managed by the NASA Dynamics of the Solid Earth (DOSE) and operated by the Bendix Field Engineering Corporation, the University of Hawaii, and the University of Texas have produced a wealth on interdisciplinary scientific data over the last three decades. Despite upgrades to the most of the ranging station subsystems, the control computers remain a mix of 1970's vintage minicomputers. These encompass a wide range of vendors, operating systems, and languages, making hardware and software support increasingly difficult. Current technology allows replacement of controller computers at a relatively low cost while maintaining excellent processing power and a friendly operating environment. The new controller systems are now being designed using IBM-PC-compatible 80486-based microcomputers, a real-time Unix operating system (LynxOS), and X-windows/Motif IB, and serial interfaces have been chosen. This design supports minimizing short and long term costs by relying on proven standards for both hardware and software components. Currently, the project is in the design and prototyping stage with the first systems targeted for production in mid-1993.

Generation of surface electromagnetic waves in terahertz spectral range by free-electron laser radiation and their refractive index determination

International Nuclear Information System (INIS)

Bogomolov, G.D.; Jeong, Uk Young; Zhizhin, G.N.; Nikitin, A.K.; Zavyalov, V.V.; Kazakevich, G.M.; Lee, Byung Cheol

2005-01-01

First experiments for observation of surface electromagnetic waves (SEW) in the terahertz spectral range generated on dense aluminum films covering the optical quality glass plates are presented in this paper. Coherent radiation of the new free-electron laser covering the frequency range from 30 to 100cm -1 was used. The interference technique employing SEW propagation in the part of one shoulder of the asymmetric interferometer was applied. From the interference pattern the real part of SEW's effective refractive index ae ' was determined for the two laser emission wavelengths: at λ=150μm-ae ' =1+5x10 -5 , at λ=110μm-ae ' =1+8x10 -4 . High sensitivity of the interference patterns to overlayers made of Ge and Si with thickness of 100nm was demonstrated as well

The Two-Beam Free Electron Laser Oscillator

CERN Document Server

Thompson, Neil R

2004-01-01

A one-dimensional model of a free-electron laser operating simultaneously with two electron beams of different energies [1] is extended to an oscillator configuration. The electron beam energies are chosen so that an harmonic of the lower energy beam is at the fundamental radiation wavelength of the higher energy beam. Potential benefits over a single-beam free-electron laser oscillator are discussed.

Two-color spatial and temporal temperature measurements using a streaked soft x-ray imager

Energy Technology Data Exchange (ETDEWEB)

Moore, A. S., E-mail: alastair.moore@physics.org; Ahmed, M. F.; Soufli, R.; Pardini, T.; Hibbard, R. L.; Bailey, C. G.; Bell, P. M.; Hau-Riege, S. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551-0808 (United States); Benstead, J.; Morton, J.; Guymer, T. M.; Garbett, W. J.; Rubery, M. S.; Skidmore, J. W. [Directorate Science and Technology, AWE Aldermaston, Reading RG7 4PR (United Kingdom); Bedzyk, M.; Shoup, M. J.; Regan, S. P.; Agliata, T.; Jungquist, R. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Schmidt, D. W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); and others

2016-11-15

A dual-channel streaked soft x-ray imager has been designed and used on high energy-density physics experiments at the National Ignition Facility. This streaked imager creates two images of the same x-ray source using two slit apertures and a single shallow angle reflection from a nickel mirror. Thin filters are used to create narrow band pass images at 510 eV and 360 eV. When measuring a Planckian spectrum, the brightness ratio of the two images can be translated into a color-temperature, provided that the spectral sensitivity of the two images is well known. To reduce uncertainty and remove spectral features in the streak camera photocathode from this photon energy range, a thin 100 nm CsI on 50 nm Al streak camera photocathode was implemented. Provided that the spectral shape is well-known, then uncertainties on the spectral sensitivity limits the accuracy of the temperature measurement to approximately 4.5% at 100 eV.

In-line process control for laser welding of titanium by high dynamic range ratio pyrometry and plasma spectroscopy

Science.gov (United States)

Lempe, B.; Taudt, C.; Baselt, T.; Rudek, F.; Maschke, R.; Basan, F.; Hartmann, P.

2014-02-01

The production of complex titanium components for various industries using laser welding processes has received growing attention in recent years. It is important to know whether the result of the cohesive joint meets the quality requirements of standardization and ultimately the customer requirements. Erroneous weld seams can have fatal consequences especially in the field of car manufacturing and medicine technology. To meet these requirements, a real-time process control system has been developed which determines the welding quality through a locally resolved temperature profile. By analyzing the resulting weld plasma received data is used to verify the stability of the laser welding process. The determination of the temperature profile is done by the detection of the emitted electromagnetic radiation from the material in a range of 500 nm to 1100 nm. As detectors, special high dynamic range CMOS cameras are used. As the emissivity of titanium depends on the wavelength, the surface and the angle of radiation, measuring the temperature is a problem. To solve these a special pyrometer setting with two cameras is used. That enables the compensation of these effects by calculating the difference between the respective pixels on simultaneously recorded images. Two spectral regions with the same emissivity are detected. Therefore the degree of emission and surface effects are compensated and canceled out of the calculation. Using the spatially resolved temperature distribution the weld geometry can be determined and the laser process can be controlled. The active readjustment of parameters such as laser power, feed rate and inert gas injection increases the quality of the welding process and decreases the number of defective goods.

Mixture analysis with laser raman spctroscopy

International Nuclear Information System (INIS)

Kim, M.S.; Bark, G.M.

1981-01-01

Trace amount of methyl orange was determined in colored medium by resonance Raman spectrometry. Without major modification of a commercial laser Raman spectrometer, the resonance Raman active molecule could be determined satisfactorily in 10sup(-5)M range when the background fluorescence was more than 20 times stronger than the signal. Use of fluorescence quenching agent was found helpful to improve the Raman signal. Suggestions for the improvement of analytical method is presented. (Author)

A semiclassical approach for two-color four-mode solid-state superfluorescence

International Nuclear Information System (INIS)

Lambruschini, C.L.P.

1991-05-01

A model for multilevel superfluorescence is presented. By using a parametric solution of this model we explain basic features in the two-color solid-state superfluorescence experiments of Florian, Schwan and Schmid. (author). 23 refs

Scanning laser beam displays based on a 2D MEMS

Science.gov (United States)

Niesten, Maarten; Masood, Taha; Miller, Josh; Tauscher, Jason

2010-05-01

The combination of laser light sources and MEMS technology enables a range of display systems such as ultra small projectors for mobile devices, head-up displays for vehicles, wearable near-eye displays and projection systems for 3D imaging. Images are created by scanning red, green and blue lasers horizontally and vertically with a single two-dimensional MEMS. Due to the excellent beam quality of laser beams, the optical designs are efficient and compact. In addition, the laser illumination enables saturated display colors that are desirable for augmented reality applications where a virtual image is used. With this technology, the smallest projector engine for high volume manufacturing to date has been developed. This projector module has a height of 7 mm and a volume of 5 cc. The resolution of this projector is WVGA. No additional projection optics is required, resulting in an infinite focus depth. Unlike with micro-display projection displays, an increase in resolution will not lead to an increase in size or a decrease in efficiency. Therefore future projectors can be developed that combine a higher resolution in an even smaller and thinner form factor with increased efficiencies that will lead to lower power consumption.

Processing and Application of ICESat Large Footprint Full Waveform Laser Range Data

NARCIS (Netherlands)

Duong, V.H.

2010-01-01

In the last two decades, laser scanning systems made the transition from scientific research to the commercial market. Laser scanning has a large variety of applications such as digital elevation models, forest inventory and man-made object reconstruction, and became the most required input data for

Laser Range Profiling for Active Protection System Target Classification and Aim-Point Selection

National Research Council Canada - National Science Library

Jones, Michael

2004-01-01

.... The attractiveness of smaller, faster interceptors precipitated the investigation of a laser radar sensor augmentation for CIAPS that could quickly resolve the range profile of an incoming projectile...

Unquenched Complex Dirac Spectra at Nonzero Chemical Potential: Two-Color QCD Lattice Data versus Matrix Model

International Nuclear Information System (INIS)

Akemann, Gernot; Bittner, Elmar

2006-01-01

We compare analytic predictions of non-Hermitian chiral random matrix theory with the complex Dirac operator eigenvalue spectrum of two-color lattice gauge theory with dynamical fermions at nonzero chemical potential. The Dirac eigenvalues come in complex conjugate pairs, making the action of this theory real and positive for our choice of two staggered flavors. This enables us to use standard Monte Carlo simulations in testing the influence of the chemical potential and quark mass on complex eigenvalues close to the origin. We find excellent agreement between the analytic predictions and our data for two different volumes over a range of chemical potentials below the chiral phase transition. In particular, we detect the effect of unquenching when going to very small quark masses

Optimal designs for one- and two-color microarrays using mixed models: a comparative evaluation of their efficiencies.

Science.gov (United States)

Lima Passos, Valéria; Tan, Frans E S; Winkens, Bjorn; Berger, Martijn P F

2009-01-01

Comparative studies between the one- and two-color microarrays provide supportive evidence for similarities of results on differential gene expression. So far, no design comparisons between the two platforms have been undertaken. With the objective of comparing optimal designs of one- and two-color microarrays in their statistical efficiencies, techniques of design optimization were applied within a mixed model framework. A- and D-optimal designs for the one- and two-color platforms were sought for a 3 x 3 factorial experiment. The results suggest that the choice of the platform will not affect the "subjects to groups" allocation, being concordant in the two designs. However, under financial constraints, the two-color arrays are expected to have a slight upper hand in terms of efficiency of model parameters estimates, once the price of arrays is more expensive than that of subjects. This statement is especially valid for microarray studies envisaging class comparisons.

Two Micron Laser Technology Advancements at NASA Langley Research Center

Science.gov (United States)

Singh, Upendra N.

2010-01-01

An Independent Laser Review Panel set up to examine NASA s space-based lidar missions and the technology readiness of lasers appropriate for space-based lidars indicated a critical need for an integrated research and development strategy to move laser transmitter technology from low technical readiness levels to the higher levels required for space missions. Based on the review, a multiyear Laser Risk Reduction Program (LRRP) was initiated by NASA in 2002 to develop technologies that ensure the successful development of the broad range of lidar missions envisioned by NASA. This presentation will provide an overview of the development of pulsed 2-micron solid-state laser technologies at NASA Langley Research Center for enabling space-based measurement of wind and carbon dioxide.

Laser-Bioplasma Interaction: Excitation and Suppression of the Brain Waves by the Multi-photon Pulsed-operated Fiber Lasers in the Ultraviolet Range of Frequencies

Science.gov (United States)

Stefan, V. Alexander; IAPS-team Team

2017-10-01

The novel study of the laser excitation-suppression of the brain waves is proposed. It is based on the pulsed-operated multi-photon fiber-laser interaction with the brain parvalbumin (PV) neurons. The repetition frequency matches the low frequency brain waves (5-100 Hz); enabling the resonance-scanning of the wide range of the PV neurons (the generators of the brain wave activity). The tunable fiber laser frequencies are in the ultraviolet frequency range, thus enabling the monitoring of the PV neuron-DNA, within the 10s of milliseconds. In medicine, the method can be used as an ``instantaneous-on-off anesthetic.'' Supported by Nikola Tesla Labs, Stefan University.

Laser bistatic two-dimensional scattering imaging simulation of lambert cone

Science.gov (United States)

Gong, Yanjun; Zhu, Chongyue; Wang, Mingjun; Gong, Lei

2015-11-01

This paper deals with the laser bistatic two-dimensional scattering imaging simulation of lambert cone. Two-dimensional imaging is called as planar imaging. It can reflect the shape of the target and material properties. Two-dimensional imaging has important significance for target recognition. The expression of bistatic laser scattering intensity of lambert cone is obtained based on laser radar eauqtion. The scattering intensity of a micro-element on the target could be obtained. The intensity is related to local angle of incidence, local angle of scattering and the infinitesimal area on the cone. According to the incident direction of laser, scattering direction and normal of infinitesimal area, the local incidence angle and scattering angle can be calculated. Through surface integration and the introduction of the rectangular function, we can get the intensity of imaging unit on the imaging surface, and then get Lambert cone bistatic laser two-dimensional scattering imaging simulation model. We analyze the effect of distinguishability, incident direction, observed direction and target size on the imaging. From the results, we can see that the scattering imaging simulation results of the lambert cone bistatic laser is correct.

Two-color studies of autoionizing states of small molecules

International Nuclear Information System (INIS)

Pratt, S.T.; Dehmer, P.M.; Dehmer, J.L.; Tomkins, F.S.; O'Halloran, M.A.

1989-01-01

Two-color, resonantly enhanced multiphoton ionization is proving to be a valuable technique for the study of autoionizing states of small molecules. In this talk, results obtained by combining REMPI, photoelectron spectroscopy, and mass spectrometry will be discussed and will be illustrated by examples from our recent studies of rotational and vibrational autoionization in molecular hydrogen and rotational autoionization in nitric oxide. 2 refs., 1 fig

Color me healthy: food diversity in school community gardens in two rapidly urbanising Australian cities.

Science.gov (United States)

Guitart, Daniela A; Pickering, Catherine M; Byrne, Jason A

2014-03-01

Community garden research has focused on social aspects of gardens, neglecting systematic analysis of what food is grown. Yet agrodiversity within community gardens may provide health benefits. Diverse fruit and vegetables provide nutritional benefits, including vitamins, minerals and phytochemicals. This paper reports research that investigated the agro-biodiversity of school-based community gardens in Brisbane and Gold Coast cities, Australia. Common motivations for establishing these gardens were education, health and environmental sustainability. The 23 gardens assessed contained 234 food plants, ranging from 7 to 132 plant types per garden. This included 142 fruits and vegetables. The nutritional diversity of fruits and vegetable plants was examined through a color classification system. All gardens grew fruits and vegetables from at least four food color groups, and 75% of the gardens grew plants from all seven color groups. As places with high agrodiversity, and related nutritional diversity, some school community gardens can provide children with exposure to a healthy range of fruit and vegetables, with potential flow-on health benefits. Copyright © 2014 Elsevier Ltd. All rights reserved.

Coherent laser radar with dual-frequency Doppler estimation and interferometric range detection

NARCIS (Netherlands)

Onori, D.; Scotti, F.; Laghezza, F.; Scaffardi, M.; Bogoni, A.

2016-01-01

The concept of a coherent interferometric dual frequency laser radar, that measures both the target range and velocity, is presented and experimentally demonstrated. The innovative architecture combines the dual frequency lidar concept, allowing a precise and robust Doppler estimation, with the

Heterodyne interferometer laser source with a pair of two phase locked loop coupled He–Ne lasers by 632.8 nm

International Nuclear Information System (INIS)

Sternkopf, C; Diethold, C; Gerhardt, U; Manske, E; Wurmus, J

2012-01-01

Two He–Ne lasers are frequency and phase coupled by phase locking loop technique for a heterodyne laser interferometer. The heterodyne He–Ne laser is built of stabilized commercially used laser tubes. The two lasers create a high frequency stable heterodyne laser source with an output power of 2 mW. The laser source is coupled by two fibers (one fiber per laser) to the heterodyne laser head. This paper describes the configuration and the control theory basics of the laser system. The experimental setup and the equipment used are also described. First, experimental results with different parameters are represented. Then we discuss a novel heterodyne laser source which has achieved a master laser frequency stability of Δf 1 /f 1 = 1 · 10 −8 and a beat frequency stability of approximately Δf beat /f beat ≈ 4.5 · 10 −5 . (paper)

Correlation between three color coordinates of human teeth

Science.gov (United States)

Lee, Yong-Keun

2014-11-01

The objective was to determine whether there were significant correlations in the three color coordinates within each of two color coordinate systems, such as the Commission Internationale de l'Eclairage (CIE) L*a*b* system, and the lightness, chroma, and hue angle system, of human vital teeth. The color of six maxillary and six mandibular anterior teeth was measured by the Shade Vision System. Pearson correlations between each pair of the color coordinates were determined (α=0.01). The influence of two color coordinates on the other color coordinate was determined with a multiple regression analysis (α=0.01). Based on correlation analyses, all the color coordinate pairs showed significant correlations except for the chroma and hue angle pair. The CIE L* was negatively correlated with the CIE a*, b*, and chroma, but positively correlated with the hue angle. The CIE a* was positively correlated with the CIE b* and chroma. Tooth color coordinates were correlated each other. Lighter teeth were less chromatic both in the CIE a* and b* coordinates. Therefore, it was postulated that the three color coordinates of human teeth were harmonized within certain color attribute ranges, and a lack of correlations in these coordinates might indicate external/internal discolorations and/or anomalies of teeth.

Narrow-line external cavity diode laser micro-packaging in the NIR and MIR spectral range

Science.gov (United States)

Jiménez, A.; Milde, T.; Staacke, N.; Aßmann, C.; Carpintero, G.; Sacher, J.

2017-07-01

Narrow-linewidth tunable diode lasers are an important tool for spectroscopic instrumentation. Conventional external cavity diode lasers offer high output power and narrow linewidth. However, most external cavity diode lasers are designed as laboratory instrument and do not allow portability. In comparison, other commonly used lasers, like distributed feedback lasers (DFB) that are capable of driving a handheld device, are limited in power and show linewidths which are not sufficiently narrow for certain applications. We present new miniaturized types of tunable external cavity diode laser which overcome the drawbacks of conventional external cavity diode lasers and which preserve the advantages of this laser concept. Three different configurations are discussed in this article. The three types of miniaturized external cavity diode laser systems achieve power values of more than 50 mW within the 1.4 μm water vapor absorption band with excellent side-mode suppression and linewidth below 100 kHz. Typical features outstand with respect to other type of laser systems which are of extended use such as DFB laser diodes. The higher output power and the lower linewidth will enable a higher sensitivity and resolution for a wide range of applications.

Three-dimensional perceived-shape representation fusing range data and fuzzy-like segmented image data

Science.gov (United States)

Bourbakis, Nikolaos G.

2001-04-01

A fusion technique is presented for 3D representation. The fusion involves laser range data and segmented image data, using human expertise related to the environment. In particular, the range data may contain noise due to reflections on sloped surfaces or long open corridors; the proposed approach removes the noise by using human expertise from 3D environments. This method could be utilized either by an autonomous robot in an unknown environment, or by an inspection machine in a complex manufacturing environment, or by a visual navigation device used by blind people. Additional applications for this technique are to correct measurement deficiencies in a laser scan and to provide a true color and 3D perceived-shape representation for a given object in a modeling environment.

Laser parameters of a Fe : ZnSe crystal in the 85-255-K temperature range

NARCIS (Netherlands)

Voronov, AA; Kozlovskii, [No Value; Korostelin, YV; Podmar'kov, YP; Frolov, MP

The temperature dependence of the efficiency of a laser based on a Fe:ZnSe crystal grown from the vapour phase by the free-growth method is studied in the 85-255-K temperature range. As the temperature was increased, the slope efficiency of the laser with respect to absorbed energy decreased from

Spectrally resolved measurements of the terahertz beam profile generated from a two-color air plasma

DEFF Research Database (Denmark)

Pedersen, Pernille Klarskov; Zalkovskij, Maksim; Strikwerda, Andrew

2014-01-01

Using a THz camera and THz bandpass filters, we measure the frequency - resolved beam profile emitted from a two - color air plasma. We observe a frequency - independent emission angle from the plasma .......Using a THz camera and THz bandpass filters, we measure the frequency - resolved beam profile emitted from a two - color air plasma. We observe a frequency - independent emission angle from the plasma ....

Risks and advantages of using surface laser photogrammetry on free-ranging marine organisms: a case study on white sharks Carcharodon carcharias.

Science.gov (United States)

Leurs, G; O'Connell, C P; Andreotti, S; Rutzen, M; Vonk Noordegraaf, H

2015-06-01

This study employed a non-lethal measurement tool, which combined an existing photo-identification technique with a surface, parallel laser photogrammetry technique, to accurately estimate the size of free-ranging white sharks Carcharodon carcharias. Findings confirmed the hypothesis that surface laser photogrammetry is more accurate than crew-based estimations that utilized a shark cage of known size as a reference tool. Furthermore, field implementation also revealed that the photographer's angle of reference and the shark's body curvature could greatly influence technique accuracy, exposing two limitations. The findings showed minor inconsistencies with previous studies that examined pre-caudal to total length ratios of dead specimens. This study suggests that surface laser photogrammetry can successfully increase length estimation accuracy and illustrates the potential utility of this technique for growth and stock assessments on free-ranging marine organisms, which will lead to an improvement of the adaptive management of the species. © 2015 The Fisheries Society of the British Isles.

On the chiral perturbation theory for two-flavor two-color QCD at finite chemical potential

Czech Academy of Sciences Publication Activity Database

Brauner, Tomáš

2006-01-01

Roč. 21, č. 7 (2006), s. 559-569 ISSN 0217-7323 R&D Projects: GA ČR(CZ) GD202/05/H003 Institutional research plan: CEZ:AV0Z10480505 Keywords : two-color QCD * chiral perturbation theory * chemical potential Subject RIV: BE - Theoretical Physics Impact factor: 1.564, year: 2006

Full-color tuning in binary polymer:perovskite nanocrystals organic-inorganic hybrid blends

Science.gov (United States)

Perulli, A.; Balena, A.; Fernandez, M.; Nedelcu, G.; Cretí, A.; Kovalenko, M. V.; Lomascolo, M.; Anni, M.

2018-04-01

The excellent optical and electronic properties of metal halide perovskites recently proposed these materials as interesting active materials for optoelectronic applications. In particular, the high color purity of perovskite colloidal nanocrystals (NCs) had recently motivated their exploration as active materials for light emitting diodes with tunable emission across the visible range. In this work, we investigated the emission properties of binary blends of conjugated polymers and perovskite NCs. We demonstrate that the emission color of the blends is determined by the superposition of the component photoluminescence spectra, allowing color tuning by acting on the blend relative composition. The use of two different polymers, two different perovskite NCs, and different blend compositions is exploited to tune the blend color in the blue-green, yellow-red, and blue-red ranges, including white light generation.

Two-step laser ionization schemes for in-gas laser ionization and spectroscopy of radioactive isotopesa