Non-invasive terahertz field imaging inside parallel plate waveguides

DEFF Research Database (Denmark)

Iwaszczuk, Krzysztof; Andryieuski, Andrei; Lavrinenko, Andrei

2011-01-01

We present a non-invasive broadband air photonic method of imaging of the electric field of THz pulses propagating inside a tapered parallel plate waveguide. The method is based on field-enhanced second harmonic generation of the fundamental laser beam in an external electric field. We apply...

Silicon graphene waveguide tunable broadband microwave photonics phase shifter.

Science.gov (United States)

Capmany, José; Domenech, David; Muñoz, Pascual

2014-04-07

We propose the use of silicon graphene waveguides to implement a tunable broadband microwave photonics phase shifter based on integrated ring cavities. Numerical computation results show the feasibility for broadband operation over 40 GHz bandwidth and full 360° radiofrequency phase-shift with a modest voltage excursion of 0.12 volt.

Devices Based on Parallel-Plate Waveguides for Terahertz Applications

Science.gov (United States)

Reichel, Kimberly S.

The promise of terahertz (THz) frequencies for technological applications is wide, spanning from wireless communications for faster downloads to non-destructive imaging for security screening. Although the potential is high, there is a lack of the basic devices necessary to make these prospects a reality. One essential component for any electromagnetic wave technology is a waveguide, which as the name implies can guide light waves, like a hose would direct water from the source to the desired target location. Several waveguide types have been introduced for THz frequencies, one of the most promising of which is the parallel-plate waveguide (PPWG). The PPWG is attractive based on its superior waveguiding performance of efficient input coupling and low losses, but additionally it serves as an excellent platform for other purposes. The projects presented in this dissertation highlight a few new functionalities incorporated into, and enabled by, a PPWG for sensing, filtering, and splitting. First, we characterize a high quality factor resonator integrated into a PPWG used for microfluidic sensing. Typically, the characterization of the frequency-dependent electric field profile inside a narrowband resonator is challenging, either due to limited optical access or to the perturbative effects of invasive probes. In our situation however, the geometry of the PPWG allows for direct access to the resonant cavity via the open sides of the waveguide and a novel implementation of the air-biased coherent detection (ABCD) method permits non-invasive probing. Through both experiment and simulation, we see the narrowband frequencies trapped in the resonator and also discover an unexpected broadband asymmetric field distribution due to the resonator inside the waveguide, yielding new information that is not available in the far field. Second, we investigate a narrowband tunable filter based on extraordinary optical transmission (EOT) through a 1D array of subwavelength holes inside

Tunable THz notch filter with a single groove inside parallel-plate waveguides.

Science.gov (United States)

Lee, Eui Su; Jeon, Tae-In

2012-12-31

A single groove in a parallel-plate waveguide (PPWG) has been applied to a tunable terahertz (THz) notch filter with a transverse-electromagnetic (TEM) mode. When the air gap between the metal plates of the PPWG is controlled from 60 to 240 μm using a motor controlled translation stage or a piezo-actuator, the resonant frequency of the notch filter is changed from 1.75 up to 0.62 THz, respectively. Therefore, the measured tunable sensitivity of the notch filter increases to 6.28 GHz/μm. The measured resonant frequencies were found to be in good agreement with the calculation using an effective groove depth. Using a finite-difference time-domain (FDTD) simulation, we also demonstrate that the sensitivity of a THz microfluidic sensor can be increased via a small air gap, a narrow groove width, and a deep groove depth.

Broadband Millimeter-Wave In-Phase and Out-of-Phase Waveguide Dividers with High Isolation

Science.gov (United States)

Dong, Jun; Liu, Yu; Yang, Ziqiang; Peng, Hao; Yang, Tao

2015-11-01

In this paper, two novel broadband in-phase and out-of-phase waveguide power dividers with high isolation are presented. Based on the substrate-integrated waveguide (SIW) divider and SIW-to-waveguide transition circuit, two kinds of E-plane waveguide dividers have been implemented. Due to the features of in-phase and out-of-phase performances, the proposed waveguide dividers can provide much more flexibilities than that of conventional E-plane waveguide T-junction. A broadband phase and amplitude performances are achieved across the whole Ka-band owing to the wideband characteristic of the SIW divider and transition circuits. To minimize the size and loss of the divider, a compact and low-loss SIW-to-waveguide transition circuit has been developed using the antisymmetric tapered probes. Two prototypes of the Ka-band waveguide dividers, including the in-phase and out-of-phase types, have been fabricated and measured. Measured results show that the isolation, input return loss, output return loss, amplitude imbalance, and phase imbalance of the in-phase divider are better than 15.5, 13.1, 10.8, 0.4 dB, and 3.50, while those of the out-of-phase divider are better than 15.0, 13.4, 10.4, 0.5 dB, and 3.60, respectively, over the frequency range from 26.5 to 40 GHz. The measured results agree well with the simulated ones. Considering their wide bandwidth, high isolation, good port matching performance, and compact configuration, the two types of waveguide dividers can be good candidates for broadband applications in millimeter-wave waveguide systems.

Highly nonlinear organic crystal OHQ-T for efficient ultra-broadband terahertz wave generation beyond 10 THz.

Science.gov (United States)

Kang, Bong Joo; Baek, In Hyung; Lee, Seung-Heon; Kim, Won Tae; Lee, Seung-Jun; Jeong, Young Uk; Kwon, O-Pil; Rotermund, Fabian

2016-05-16

We report on efficient generation of ultra-broadband terahertz (THz) waves via optical rectification in a novel nonlinear organic crystal with acentric core structure, i.e. 2-(4-hydroxystyryl)-1-methylquinolinium 4-methylbenzenesulfonate (OHQ-T), which possesses an ideal molecular structure leading to a maximized nonlinear optical response for near-infrared-pumped THz wave generation. By systematic studies on wavelength-dependent phase-matching conditions in OHQ-T crystals of different thicknesses we are able to generate coherent THz waves with a high peak-to-peak electric field amplitude of up to 650 kV/cm and an upper cut-off frequency beyond 10 THz. High optical-to-THz conversion efficiency of 0.31% is achieved by efficient index matching with a selective pumping at 1300 nm.

Transmission Characteristics of a Generalized Parallel Plate Dielectric Waveguide at THz Frequencies

International Nuclear Information System (INIS)

Ye Long-Fang; Xu Rui-Min; Zhang Yong; Lin Wei-Gan

2011-01-01

A generalized parallel-plate dielectric waveguide (G-PPDW) is proposed as a new guiding medium for terahertz wave. A theoretical analysis of the transmission characteristics for the TE modes of this generalized structure is performed. Equations are presented for the field components, dispersion, power ratio, transmission loss and characteristic impedance as functions of the operating frequencies, dimensions and material constants. In the case of the lowest-order mode TE 10 , design curves covering frequencies and dimensions for the given material constants in the THz region are presented. The theoretical results of transmission characteristics obtained from these equations are verified by the finite-element method with a good agreement. The investigation results show that by selecting proper dimensions and dielectric materials, G-PPDW can be used to guide THz waves efficiently with high power confinement and low attenuation. These outstanding properties may open up a way to many important applications for THz integrated circuits and systems. (fundamental areas of phenomenology(including applications))

Theoretical description and design of nanomaterial slab waveguides: application to compensation of optical diffraction.

Science.gov (United States)

Kivijärvi, Ville; Nyman, Markus; Shevchenko, Andriy; Kaivola, Matti

2018-04-02

Planar optical waveguides made of designable spatially dispersive nanomaterials can offer new capabilities for nanophotonic components. As an example, a thin slab waveguide can be designed to compensate for optical diffraction and provide divergence-free propagation for strongly focused optical beams. Optical signals in such waveguides can be transferred in narrow channels formed by the light itself. We introduce here a theoretical method for characterization and design of nanostructured waveguides taking into account their inherent spatial dispersion and anisotropy. Using the method, we design a diffraction-compensating slab waveguide that contains only a single layer of silver nanorods. The waveguide shows low propagation loss and broadband diffraction compensation, potentially allowing transfer of optical information at a THz rate.

Broadband THz pulse emission and transmission properties of nanostructured Pt thin films

Energy Technology Data Exchange (ETDEWEB)

Hu, Mingzhe [Department of Physics and Electronics, Liupanshui Normal University, Liupanshui, Guizhou 553004 (China); College of Electronics and Information, Guizhou University, Huaxi 550025, Guiyang, Guizhou (China); Mu, Kaijun; Zhang, Cunlin [Department of Physics, Capital Normal University, Yuquan Road 100082, Beijing (China); Gu, Haoshuang, E-mail: guhs@hubu.edu.cn [Department of Electronic Sci& Tech, Hubei University, Xueyuan Road 430062, Wuhan, Hubei (China); Ding, Zhao [College of Electronics and Information, Guizhou University, Huaxi 550025, Guiyang, Guizhou (China)

2015-10-01

The THz transmission and emitting properties of a composite metallic nanostructure, composed of Ag nanowires electrodeposited in an anodic aluminum oxide (AAO) template and a Pt thin film, were investigated by using a femtosecond pulse laser irradiation. The microstructure of the above sub-wavelength nanostructure was investigated by XRD, SEM, AFM and TEM. The results indicated that the thickness of the Pt thin film was about 200 nm and the Ag nanowire array had a sparse and random distribution inside the AAO template, with a length distribution in the range of 10–25 μm. The THz radiation properties of above sub-wavelength nanostructure indicated that the generated THz fluence from the Pt film was a magnitude of μW scale with a broadband frequency range and its subsequent transmission could be significantly improved by the better impedance matching property of the Ag nanowire embedded AAO film compared with that of the empty AAO film.

Chemical recognition with broadband THz spectroscopy

DEFF Research Database (Denmark)

Fischer, Bernd M.; Helm, Hanspeter; Jepsen, Peter Uhd

2004-01-01

THz science is developing rapidly in Europe as well as the rest of the world. There is a strong interest in the exploitation of optical technologies in the THz frequency range in virtually all fields of basic and applied sciences of physics, chemistry, biology as well as medicine. Commercial...... interest in this field has also been growing, spurred by the potential of tHz tools in quality control and the biotechnology sector. We will review some contrast mechanisms, which form the basis for real-world applications of THz technology, in particular in the fields of applied chemistry...... and biotechnology. Whereas narrow bandwidth THz technology may become important for e.g. real-time imaging at larger standoff distances, we will concentrate on broad bandwidth THz technologies for spectroscopic identification of various substances. It has recently been established that the 0.1-5 THz spectral range...

Low-index discontinuity terahertz waveguides

Science.gov (United States)

Nagel, Michael; Marchewka, Astrid; Kurz, Heinrich

2006-10-01

A new type of dielectric THz waveguide based on recent approaches in the field of integrated optics is presented with theoretical and experimental results. Although the guiding mechanism of the low-index discontinuity (LID) THz waveguide is total internal reflection, the THz wave is predominantly confined in the virtually lossless low-index air gap within a high-index dielectric waveguide due to the continuity of electric flux density at the dielectric interface. Attenuation, dispersion and single-mode confinement properties of two LID structures are discussed and compared with other THz waveguide solutions. The new approach provides an outstanding combination of high mode confinement and low transmission losses currently not realizable with any other metal-based or photonic crystal approach. These exceptional properties might enable the breakthrough of novel integrated THz systems or endoscopy applications with sub-wavelength resolution.

Design and Realization Aspects of 1-THz Cascade Backward Wave Amplifier Based on Double Corrugated Waveguide

DEFF Research Database (Denmark)

Paoloni, Claudio; Di Carlo, Aldo; Bouamrane, Fayçal

2013-01-01

The design and fabrication challenges in the first ever attempt to realize a 1-THz vacuum tube amplifier are described. Implementation of innovative solutions including a slow-wave structure in the form of a double corrugated waveguide, lateral tapered input and output couplers, deep X-ray LIGA f...

Metallic and 3D-printed dielectric helical terahertz waveguides.

Science.gov (United States)

Vogt, Dominik Walter; Anthony, Jessienta; Leonhardt, Rainer

2015-12-28

We investigate guidance of Terahertz (THz) radiation in metallic and 3D-printed dielectric helical waveguides in the frequency range from 0.2 to 1 THz. Our experimental results obtained from THz time-domain spectroscopy (THz-TDS) measurements are in very good agreement with finite-difference time-domain (FDTD) simulations. We observe single-mode, low loss and low dispersive propagation of THz radiation in metallic helical waveguides over a broad bandwidth. The 3D-printed dielectric helical waveguides have substantially extended the bandwidth of a low loss dielectric tube waveguide as observed from the experimental and simulation results. The high flexibility of the helical design allows an easy incorporation into bench top THz devices.

THz Electron Paramagnetic Resonance / THz Spectroscopy at BESSY II

Directory of Open Access Journals (Sweden)

Karsten Holldack

2016-02-01

Full Text Available The THz beamline at BESSY II employs high power broadband femto- to picosecond long THz pulses for magneto-optical THz and FIR studies. A newly designed set-up exploits the unique properties of ultrashort THz pulses generated by laser-energy modulation of electron bunches in the storage ring or alternatively from compressed electron bunches. Experiments from 0.15 to 5 THz (~ 5 – 150 cm-1 may be conducted at a user station equipped with a fully evacuated high resolution FTIR spectrometer (0.0063 cm-1, lHe cooled bolometer detectors, a THz TDS set-up and different sample environments, including a superconducting high field magnet (+11 T - 11T with variable temperature insert (1.5 K – 300 K, a sample cryostat and a THz attenuated total reflection chamber.  Main applications are Frequency Domain Fourier transform THz-Electron Paramagnetic Resonance (FD-FT THz-EPR, THz-FTIR spectroscopy and optical pump - THz probe time domain spectroscopy (TDS, with sub-ps time resolution.

A compact, all-optical, THz wave generator based on self-modulation in a slab photonic crystal waveguide with a single sub-nanometer graphene layer.

Science.gov (United States)

Asadi, R; Ouyang, Z; Mohammd, M M

2015-07-14

We design a compact, all-optical THz wave generator based on self-modulation in a 1-D slab photonic crystal (PhC) waveguide with a single sub-nanometer graphene layer by using enhanced nonlinearity of graphene. It has been shown that at the bandgap edge of higher bands of a 1-D slab PhC, through only one sub-nanometer graphene layer we can obtain a compact, high modulation factor (about 0.98 percent), self-intensity modulator at a high frequency (about 0.6 THz) and low threshold intensity (about 15 MW per square centimeter), and further a compact, all-optical THz wave generator by integrating the self-modulator with a THz photodiode or photonic mixer. Such a THz source is expected to have a relatively high efficiency compared with conventional sources based on optical methods. The proposed THz source can find wide applications in THz science and technology, e.g., in THz imaging, THz sensors and detectors, THz communication systems, and THz optical integrated logic circuits.

Broadband nanophotonic waveguides and resonators based on epitaxial GaN thin films

Energy Technology Data Exchange (ETDEWEB)

Bruch, Alexander W.; Xiong, Chi; Leung, Benjamin; Poot, Menno; Han, Jung; Tang, Hong X., E-mail: hong.tang@yale.edu [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511 (United States)

2015-10-05

We demonstrate broadband, low loss optical waveguiding in single crystalline GaN grown epitaxially on c-plane sapphire wafers through a buffered metal-organic chemical vapor phase deposition process. High Q optical microring resonators are realized in near infrared, infrared, and near visible regimes with intrinsic quality factors exceeding 50 000 at all the wavelengths we studied. TEM analysis of etched waveguide reveals growth and etch-induced defects. Reduction of these defects through improved material and device processing could lead to even lower optical losses and enable a wideband photonic platform based on GaN-on-sapphire material system.

The Prospects of Ultra-Broadband THz Wireless Communications

DEFF Research Database (Denmark)

Yu, Xianbin; Chen, Ying; Galili, Michael

2014-01-01

Wireless communications have entered into a path towards Terabit era, to accommodate the increasing demands on fast wireless access, e.g. huge data file transferring and fast mobile data access. Terahertz (THz) technology is considered feasible to carry ultrafast data signals, as it offers up...... to a few THz bandwidths. This paper overviews the prospects of Tbit/s wireless data rate and their potential applications. Technically, this talk reviews the key technologies and challenges to achieve an ultrafast wireless system operating in the THz frequency band, from viewpoint of communication......, in terms of ultrafast THz generation/THz detection and link power budget....

Mapping the broadband polarization properties of linear 2D SOI photonic crystal waveguides

DEFF Research Database (Denmark)

Canning, John; Skivesen, Nina; Kristensen, Martin

2007-01-01

Both quasi-TE and TM polarisation spectra for a silicon- on-insulator (SOI) waveguide are recorded over (1100-1700) nm using a broadband supercontinuum source. By studying both the input and output polarisation eigenstates we observe narrowband resonant cross coupling near the lowest quasi-TE mode...... cut-off. We also observe relatively broadband mixing between the two eigenstates to generate a complete photonic bandgap. By careful analysis of the output polarisation state we report on an inherent non-reciprocity between quasi TE and TM fundamental mode cross coupling. The nature of polarisation...

Intense Plasma Waveguide Terahertz Sources for High-Field THz Probe Science with Ultrafast Lasers for Solid State Physics

Science.gov (United States)

2016-08-25

Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a...Summary 2 1. Introduction 2. Two colour excitation of intense terahertz radiation in MOFs 2 3. Terahertz optical nonlinearities in...of 2- colour THz generation and propagation in waveguides that we have developed to evaluate fibre designs before fabrication is only one

Praseodymium ion doped phosphate glasses for integrated broadband ion-exchanged waveguide amplifier

Energy Technology Data Exchange (ETDEWEB)

Shen, L.F. [School of Textile and Material Engineering, Dalian Polytechnic University, Dalian 116034 (China); Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong (China); Chen, B.J. [Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong (China); Lin, H., E-mail: lhai8686@yahoo.com [School of Textile and Material Engineering, Dalian Polytechnic University, Dalian 116034 (China); Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong (China); Pun, E.Y.B. [Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong (China)

2015-02-15

Highlights: • Effective near-infrared emission (1380-1525 nm) is observed in Pr{sup 3+}-doped phosphate glasses. • Effective bandwidth of {sup 1}D{sub 2} → {sup 1}G{sub 4} transition emission is obtained to be 124 nm. • Channel waveguides have been fabricated by K{sup +}-Na{sup +} ion-exchange method. • Pr{sup 3+}-doped phosphate glasses are promising in developing integrated broadband waveguide amplifier. - Abstract: Effective near-infrared emission covering the fifth optical telecommunication window (1380-1525 nm) has been observed in Pr{sup 3+}-doped phosphate (NMAP) glasses. Judd-Ofelt parameters Ω{sub 2} (6.38 × 10{sup −20} cm{sup 2}), Ω{sub 4} (20.30 × 10{sup −20} cm{sup 2}) and Ω{sub 6} (0.40 × 10{sup −20} cm{sup 2}) indicate a high inversion asymmetrical and strong covalent environment in the optical glasses. The effective bandwidth (Δλ{sub eff}) of the corresponding {sup 1}D{sub 2} → {sup 1}G{sub 4} transition emission is obtained to be 124 nm, and the maximum stimulated emission cross-section (σ{sub em-max}) at 1468 nm is derived to be 1.14 × 10{sup −20} cm{sup 2}. Channel waveguide was fabricated successfully by K{sup +}-Na{sup +} ion-exchange method with mode field diameter of 8.8 μm in the horizontal direction and 6.7 μm in the vertical direction. Broad effective bandwidth, large emission cross-section and perfect thermal ion-exchangeability indicate that Pr{sup 3+}-doped NMAP phosphate glasses are promising in developing integrated broadband waveguide amplifier, especially operating at E- and S-bands which belong to the fifth optical telecommunication window.

Absorption-reduced waveguide structure for efficient terahertz generation

Energy Technology Data Exchange (ETDEWEB)

Pálfalvi, L., E-mail: palfalvi@fizika.ttk.pte.hu [Institute of Physics, University of Pécs, Ifjúság ú. 6, 7624 Pécs (Hungary); Fülöp, J. A. [MTA-PTE High-Field Terahertz Research Group, Ifjúság ú. 6, 7624 Pécs (Hungary); Szentágothai Research Centre, University of Pécs, Ifjúság ú. 20, 7624 Pécs (Hungary); Hebling, J. [Institute of Physics, University of Pécs, Ifjúság ú. 6, 7624 Pécs (Hungary); MTA-PTE High-Field Terahertz Research Group, Ifjúság ú. 6, 7624 Pécs (Hungary); Szentágothai Research Centre, University of Pécs, Ifjúság ú. 20, 7624 Pécs (Hungary)

2015-12-07

An absorption-reduced planar waveguide structure is proposed for increasing the efficiency of terahertz (THz) pulse generation by optical rectification of femtosecond laser pulses with tilted-pulse-front in highly nonlinear materials with large absorption coefficient. The structure functions as waveguide both for the optical pump and the generated THz radiation. Most of the THz power propagates inside the cladding with low THz absorption, thereby reducing losses and leading to the enhancement of the THz generation efficiency by up to more than one order of magnitude, as compared with a bulk medium. Such a source can be suitable for highly efficient THz pulse generation pumped by low-energy (nJ-μJ) pulses at high (MHz) repetition rates delivered by compact fiber lasers.

THz near-field imaging of biological tissues employing synchrotron radiation (Invited Paper)

Science.gov (United States)

Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried, Daniel

2005-04-01

Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking on to the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical waveguides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about λ/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 μm at about 12 wavenumbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06 and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin.

Numerical simulation of terahertz-wave propagation in photonic crystal waveguide based on sapphire shaped crystal

International Nuclear Information System (INIS)

Zaytsev, Kirill I; Katyba, Gleb M; Mukhina, Elena E; Kudrin, Konstantin G; Karasik, Valeriy E; Yurchenko, Stanislav O; Kurlov, Vladimir N; Shikunova, Irina A; Reshetov, Igor V

2016-01-01

Terahertz (THz) waveguiding in sapphire shaped single crystal has been studied using the numerical simulations. The numerical finite-difference analysis has been implemented to characterize the dispersion and loss in the photonic crystalline waveguide containing hollow cylindrical channels, which form the hexagonal lattice. Observed results demonstrate the ability to guide the THz-waves in multi-mode regime in wide frequency range with the minimal power extinction coefficient of 0.02 dB/cm at 1.45 THz. This shows the prospectives of the shaped crystals for highly-efficient THz waveguiding. (paper)

THz cavities and injectors for compact electron acceleration using laser-driven THz sources

Directory of Open Access Journals (Sweden)

Moein Fakhari

2017-04-01

Full Text Available We present a design methodology for developing ultrasmall electron injectors and accelerators based on cascaded cavities excited by short multicycle THz pulses obtained from laser-driven THz generation schemes. Based on the developed concept for optimal coupling of the THz pulse, a THz electron injector and two accelerating stages are designed. The designed electron gun consists of a four cell cavity operating at 300 GHz and a door-knob waveguide to coaxial coupler. Moreover, special designs are proposed to mitigate the problem of thermal heat flow and induced mechanical stress to achieve a stable device. We demonstrated a gun based on cascaded cavities that is powered by only 1.1 mJ of THz energy in 300 cycles to accelerate electron bunches up to 250 keV. An additional two linac sections can be added with five and four cell cavities both operating at 300 GHz boosting the bunch energy up to 1.2 MeV using a 4-mJ THz pulse.

Broadband Silicon-On-Insulator directional couplers using a combination of straight and curved waveguide sections.

Science.gov (United States)

Chen, George F R; Ong, Jun Rong; Ang, Thomas Y L; Lim, Soon Thor; Png, Ching Eng; Tan, Dawn T H

2017-08-03

Broadband Silicon-On-Insulator (SOI) directional couplers are designed based on a combination of curved and straight coupled waveguide sections. A design methodology based on the transfer matrix method (TMM) is used to determine the required coupler section lengths, radii, and waveguide cross-sections. A 50/50 power splitter with a measured bandwidth of 88 nm is designed and fabricated, with a device footprint of 20 μm × 3 μm. In addition, a balanced Mach-Zehnder interferometer is fabricated showing an extinction ratio of >16 dB over 100 nm of bandwidth.

Design of a GaP/Si composite waveguide for CW terahertz wave generation via difference frequency mixing.

Science.gov (United States)

Saito, Kyosuke; Tanabe, Tadao; Oyama, Yutaka

2014-06-10

We design a GaP/Si composite waveguide to achieve efficient terahertz (THz) wave generation under collinear phase-matched difference frequency mixing (DFM) between near-infrared light sources. This waveguide structure provides a strong mode confinement of both near-infrared sources and THz wave, resulting in an efficient mode overlapping. The numerical results show that the waveguide can produce guided THz wave (5.93 THz) with a power conversion efficiency of 6.6×10(-4)  W(-1). This value is larger than previously obtained with the bulk GaP crystal: 0.5×10(-9)  W(-1) [J. Lightwave Technol.27, 3057 (2009)]. Our proposed composite waveguide can be achieved by bridging the telecom wavelength and THz frequency region.

Broadband Terahertz Refraction Index Dispersion and Loss of Polymeric Dielectric Substrate and Packaging Materials

Science.gov (United States)

Motaharifar, E.; Pierce, R. G.; Islam, R.; Henderson, R.; Hsu, J. W. P.; Lee, Mark

2018-01-01

In the effort to push the high-frequency performance of electronic circuits and signal interconnects from millimeter waves to beyond 1 THz, a quantitative knowledge of complex refraction index values and dispersion in potential dielectric substrate, encapsulation, waveguide, and packaging materials becomes critical. Here we present very broadband measurements of the real and imaginary index spectra of four polymeric dielectric materials considered for use in high-frequency electronics: benzocyclobutene (BCB), polyethylene naphthalate (PEN), the photoresist SU-8, and polydimethylsiloxane (PDMS). Reflectance and transmittance spectra from 3 to 75 THz were made using a Fourier transform spectrometer on freestanding material samples. These data were quantitatively analyzed, taking into account multiple partial reflections from front and back surfaces and molecular bond resonances, where applicable, to generate real and imaginary parts of the refraction index as a function of frequency. All materials showed signatures of infrared active organic molecular bond resonances between 10 and 50 THz. Low-loss transmission windows as well as anti-window bands of high dispersion and loss can be readily identified and incorporated into high-frequency design models.

Direct UV-written broadband directional broadband planar waveguide couplers

DEFF Research Database (Denmark)

Olivero, Massimo; Svalgaard, Mikael

2005-01-01

We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation.......We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation....

THz and Sub-THz Capabilities of a Table-Top Radiation Source Driven by an RF Thermionic Electron Gun

Energy Technology Data Exchange (ETDEWEB)

Smirnov, Alexei V.; Agustsson, R.; Boucher, S.; Campese, Tara; Chen, Y.C.; Hartzell, Josiah J.; Jocobson, B.T.; Murokh, A.; O' Shea, F.H.; Spranza, E.; Berg, W.; Borland, M.; Dooling, J. C.; Erwin, L.; Lindberg, R. R.; Pasky, S.J.; Sereno, N.; Sun, Y.; Zholents, A.

2017-06-01

Design features and experimental results are presented for a sub-mm wave source [1] based on APS RF thermionic electron gun. The setup includes compact alpha-magnet, quadrupoles, sub-mm-wave radiators, and THz optics. The sub-THz radiator is a planar, oversized structure with gratings. Source upgrade for generation frequencies above 1 THz is discussed. The THz radiator will use a short-period undulator having 1 T field amplitude, ~20 cm length, and integrated with a low-loss oversized waveguide. Both radiators are integrated with a miniature horn antenna and a small ~90°-degree in-vacuum bending magnet. The electron beamline is designed to operate different modes including conversion to a flat beam interacting efficiently with the radiator. The source can be used for cancer diagnostics, surface defectoscopy, and non-destructive testing. Sub-THz experiment demonstrated a good potential of a robust, table-top system for generation of a narrow bandwidth THz radiation. This setup can be considered as a prototype of a compact, laser-free, flexible source capable of generation of long trains of Sub-THz and THz pulses with repetition rates not available with laser-driven sources.

Broadband electron spin resonance experiments using superconducting coplanar waveguides

Energy Technology Data Exchange (ETDEWEB)

Clauss, Conrad; Bogani, Lapo; Scheffler, Marc; Dressel, Martin [1. Physikalisches Institut, Universitaet Stuttgart (Germany); Bothner, Daniel; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut - Experimentalphysik II and Center for Collective Quantum Phenomena in LISA+, Universitaet Tuebingen (Germany)

2012-07-01

In recent years superconducting coplanar devices operating at microwave/GHz frequencies are employed in more and more experimental studies. Here, we present electron spin resonance (ESR) experiments using a superconducting coplanar waveguide to provide the RF field to drive the spin flips. In contrast to conventional ESR studies this allows broadband frequency as well as magnetic field swept observation of the spin resonance. We show experimental data of the spin resonance of the organic radical NitPhoMe (2-(4'-methoxyphenyl)-4,4,5,5-tetra-methylimidazoline-1-oxyl-3-oxide) for frequencies in the range of 1 GHz to 40 GHz and corresponding magnetic fields up to 1.4 T (for g=2). In addition we show the temperature dependence of the ESR signals for temperatures up to 30 K, which is well above the critical temperature of the niobium superconductor.

Dual THz comb spectroscopy

Science.gov (United States)

Yasui, Takeshi

2017-08-01

Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5 MHz and enhanced spectral accuracy of 8.39 × 10-7 in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy.

THz transceiver characterization : LDRD project 139363 final report.

Energy Technology Data Exchange (ETDEWEB)

Nordquist, Christopher Daniel; Wanke, Michael Clement; Cich, Michael Joseph; Reno, John Louis; Fuller, Charles T.; Wendt, Joel Robert; Lee, Mark; Grine, Albert D.

2009-09-01

LDRD Project 139363 supported experiments to quantify the performance characteristics of monolithically integrated Schottky diode + quantum cascade laser (QCL) heterodyne mixers at terahertz (THz) frequencies. These integrated mixers are the first all-semiconductor THz devices to successfully incorporate a rectifying diode directly into the optical waveguide of a QCL, obviating the conventional optical coupling between a THz local oscillator and rectifier in a heterodyne mixer system. This integrated mixer was shown to function as a true heterodyne receiver of an externally received THz signal, a breakthrough which may lead to more widespread acceptance of this new THz technology paradigm. In addition, questions about QCL mode shifting in response to temperature, bias, and external feedback, and to what extent internal frequency locking can improve stability have been answered under this project.

Broadband Optical Active Waveguides Written by Femtosecond Laser Pulses in Lithium Fluoride

International Nuclear Information System (INIS)

Chiamenti, Ismael; Costa, Larissa N. da; Kalinowski, Hypolito J.; Bonfigli, Francesca; Montereali, Rosa Maria; Gomes Anderson, S. L.

2014-01-01

Broadband waveguiding through light-emitting strips directly written in a blank lithium fluoride crystal with a femtosecond laser is reported. Light guiding was observed at several optical wavelengths, from blue, 458 nm, to near-infrared, at 1550 nm. Visible photoluminescence spectra of the optically active F 2 and F 3 + color centers produced by the fs laser writing process were measured. The wavelength-dependent refractive index increase was estimated to be in the order of 10 −3 −10 −4 in the visible and near-infrared spectral intervals, which is consistent with the stable formation of point defects in LiF

Broadband Optical Active Waveguides Written by Femtosecond Laser Pulses in Lithium Fluoride

Science.gov (United States)

Ismael, Chiamenti; Francesca, Bonfigli; Anderson, S. L. Gomes; Rosa, Maria Montereali; Larissa, N. da Costa; Hypolito, J. Kalinowski

2014-01-01

Broadband waveguiding through light-emitting strips directly written in a blank lithium fluoride crystal with a femtosecond laser is reported. Light guiding was observed at several optical wavelengths, from blue, 458 nm, to near-infrared, at 1550 nm. Visible photoluminescence spectra of the optically active F2 and F3+ color centers produced by the fs laser writing process were measured. The wavelength-dependent refractive index increase was estimated to be in the order of 10-3-10-4 in the visible and near-infrared spectral intervals, which is consistent with the stable formation of point defects in LiF.

An ultra-broadband multilayered graphene absorber

KAUST Repository

Amin, Muhammad

2013-01-01

An ultra-broadband multilayered graphene absorber operating at terahertz (THz) frequencies is proposed. The absorber design makes use of three mechanisms: (i) The graphene layers are asymmetrically patterned to support higher order surface plasmon modes that destructively interfere with the dipolar mode and generate electromagnetically induced absorption. (ii) The patterned graphene layers biased at different gate voltages backedup with dielectric substrates are stacked on top of each other. The resulting absorber is polarization dependent but has an ultra-broadband of operation. (iii) Graphene\\'s damping factor is increased by lowering its electron mobility to 1000cm 2=Vs. Indeed, numerical experiments demonstrate that with only three layers, bandwidth of 90% absorption can be extended upto 7THz, which is drastically larger than only few THz of bandwidth that can be achieved with existing metallic/graphene absorbers. © 2013 Optical Society of America.

A high extinction ratio THz polarizer fabricated by double-bilayer wire grid structure

Science.gov (United States)

Lu, Bin; Wang, Haitao; Shen, Jun; Yang, Jun; Mao, Hongyan; Xia, Liangping; Zhang, Weiguo; Wang, Guodong; Peng, Xiao-Yu; Wang, Deqiang

2016-02-01

We designed a new style of broadband terahertz (THz) polarizer with double-bilayer wire grid structure by fabricating them on both sides of silicon substrate. This THz polarizer shows a high average extinction ratio of 60dB in 0.5 to 2.0 THz frequency range and the maximum of 87 dB at 1.06 THz, which is much higher than that of conventional monolayer wire grid polarizers and single-bilayer wire grid ones.

A high extinction ratio THz polarizer fabricated by double-bilayer wire grid structure

Directory of Open Access Journals (Sweden)

Bin Lu

2016-02-01

Full Text Available We designed a new style of broadband terahertz (THz polarizer with double-bilayer wire grid structure by fabricating them on both sides of silicon substrate. This THz polarizer shows a high average extinction ratio of 60dB in 0.5 to 2.0 THz frequency range and the maximum of 87 dB at 1.06 THz, which is much higher than that of conventional monolayer wire grid polarizers and single-bilayer wire grid ones.

A photo-excited broadband to dual-band tunable terahertz prefect metamaterial polarization converter

Science.gov (United States)

Zhu, Jianfeng; Yang, Yang; Li, Shufang

2018-04-01

A new and simple design of photo-excited broadband to dual-band tunable terahertz (THz) metamaterial cross polarization converter is proposed in this paper. The tunable converter is a sandwich structure with the center-cut cross-shaped metallic patterned structure as a resonator, the middle dielectric layer as a spacer and the bottom metallic film as the ground. The conductivity of the photoconductive semiconductor (Silicon) filled in the gap of the cross-shaped metallic resonator can be tuned by the incident pump power, leading to an easy modulation of the electromagnetic response of the proposed converter. The results show that the proposed cross-polarization converter can be tuned from a broadband with polarization conversion ratio (PCR) beyond 95% (1.86-2.94 THz) to dual frequency bands (fl = 1 . 46 THz &fh = 2 . 9 THz). The conversion peaks can reach 99.9% for the broadband and, 99.5% (fl) and 99.7% (fh) for the dual-band, respectively. Most importantly, numerical simulations demonstrate that the broadband/dual-band polarization conversion mechanism of the converter originates from the localized surface plasmon modes, which make the design simple and different from previous designs. With these good features, the proposed broadband to dual-band tunable polarization converter is expected to be used in widespread applications.

Undulator radiation in a waveguide

Energy Technology Data Exchange (ETDEWEB)

Geloni, G.; Saldin, E.; Schneidmiller, E.; Yurkov, M.

2007-03-15

We propose an analytical approach to characterize undulator radiation near resonance, when the presence of the vacuum-pipe considerably affects radiation properties. This is the case of the far-infrared undulator beamline at the Free-electron LASer (FEL) in Hamburg (FLASH), that will be capable of delivering pulses in the TeraHertz (THz) range. This undulator will allow pump-probe experiments where THz pulses are naturally synchronized to the VUV pulse from the FEL, as well as the development of novel electron-beam diagnostics techniques. Since the THz radiation diffraction-size exceeds the vacuum-chamber dimensions, characterization of infrared radiation must be performed accounting for the presence of a waveguide.We developed a theory of undulator radiation in a waveguide based on paraxial and resonance approximation. We solved the field equation with a tensor Green's function technique, and extracted figure of merits describing in a simple way the influence of the vacuum-pipe on the radiation pulse as a function of the problem parameters. Our theory, that makes consistent use of dimensionless analysis, allows treatment and physical understanding of many asymptotes of the parameter space, together with their region of applicability. (orig.)

Undulator radiation in a waveguide

International Nuclear Information System (INIS)

Geloni, G.; Saldin, E.; Schneidmiller, E.; Yurkov, M.

2007-03-01

We propose an analytical approach to characterize undulator radiation near resonance, when the presence of the vacuum-pipe considerably affects radiation properties. This is the case of the far-infrared undulator beamline at the Free-electron LASer (FEL) in Hamburg (FLASH), that will be capable of delivering pulses in the TeraHertz (THz) range. This undulator will allow pump-probe experiments where THz pulses are naturally synchronized to the VUV pulse from the FEL, as well as the development of novel electron-beam diagnostics techniques. Since the THz radiation diffraction-size exceeds the vacuum-chamber dimensions, characterization of infrared radiation must be performed accounting for the presence of a waveguide.We developed a theory of undulator radiation in a waveguide based on paraxial and resonance approximation. We solved the field equation with a tensor Green's function technique, and extracted figure of merits describing in a simple way the influence of the vacuum-pipe on the radiation pulse as a function of the problem parameters. Our theory, that makes consistent use of dimensionless analysis, allows treatment and physical understanding of many asymptotes of the parameter space, together with their region of applicability. (orig.)

Corrugated metal surface with pillars for terahertz surface plasmon polariton waveguide components

KAUST Repository

Yuehong, Xu; Yanfeng, Li; Chunxiu, Tian; Jiaguang, Han; Quan, Xu; Xueqian, Zhang; Xixiang, Zhang; Ying, Zhang; Weili, Zhang

2018-01-01

In the terahertz regime, due to perfect conductivity of most metals, it is hard to realize a strong confinement of Surface plasmon polaritons (SPPs) although a propagation loss could be sufficiently low. We experimentally demonstrated a structure with periodic pillars arranged on a thin metal surface that supports bound modes of spoof SPPs at terahertz (THz) frequencies. By using scanning near-field THz microscopy, the electric field distribution above the metal surface within a distance of 130 μm was mapped. The results proved that this structure could guide spoof SPPs propagating along subwavelength waveguides, and at the same time reduce field expansion into free space. Further, for the development of integrated optical circuits, several components including straight waveguide, S-bend, Y-splitter and directional couplers were designed and characterized by the same method. We believe that the waveguide components proposed here will pave a new way for the development of flexible, wideband and compact photonic circuits operating at THz frequencies.

Corrugated metal surface with pillars for terahertz surface plasmon polariton waveguide components

KAUST Repository

Yuehong, Xu

2018-01-12

In the terahertz regime, due to perfect conductivity of most metals, it is hard to realize a strong confinement of Surface plasmon polaritons (SPPs) although a propagation loss could be sufficiently low. We experimentally demonstrated a structure with periodic pillars arranged on a thin metal surface that supports bound modes of spoof SPPs at terahertz (THz) frequencies. By using scanning near-field THz microscopy, the electric field distribution above the metal surface within a distance of 130 μm was mapped. The results proved that this structure could guide spoof SPPs propagating along subwavelength waveguides, and at the same time reduce field expansion into free space. Further, for the development of integrated optical circuits, several components including straight waveguide, S-bend, Y-splitter and directional couplers were designed and characterized by the same method. We believe that the waveguide components proposed here will pave a new way for the development of flexible, wideband and compact photonic circuits operating at THz frequencies.

80 Gbit/s 16-QAM Multicarrier THz Wireless Communication Link in the 400 GHz Band

DEFF Research Database (Denmark)

Jia, Shi; Yu, Xianbin; Hu, Hao

2016-01-01

We experimentally demonstrate a high-speed multicarrier THz wireless communication system operating in the 400 GHz band. The use of spectrally efficient 16-QAM modulation and broadband THz transceivers enable link data rates up to 80 Gbit/s....

Independent polarization and multi-band THz absorber base on Jerusalem cross

Science.gov (United States)

Arezoomand, Afsaneh Saee; Zarrabi, Ferdows B.; Heydari, Samaneh; Gandji, Navid P.

2015-10-01

In this paper, we present the design and simulation of a single and multi-band perfect metamaterial absorber (MA) in the THz region base on Jerusalem cross (JC) and metamaterial load in unit cells. The structures consist of dual metallic layers for allowing near-perfect absorption with absorption peak of more than 99%. In this novel design, four-different shape of Jerusalem cross is presented and by adding L, U and W shape loaded to first structure, we tried to achieve a dual-band absorber. In addition, by good implementation of these loaded, we are able to control the absorption resonance at second resonance at 0.9, 0.7 and 0.85 THz respectively. In the other hand, we achieved a semi stable designing at first resonance between 0.53 and 0.58 THz. The proposed absorber has broadband polarization angle. The surface current modeled and proved the broadband polarization angle at prototype MA. The LC resonance of the metamaterial for Jerusalem cross and modified structures are extracting from equivalent circuit. As a result, proposed MA is useful for THz medical imaging and communication systems and the dual-band absorber has applications in many scientific and technological areas.

Different roles of electron beam in two stream instability in an elliptical waveguide for generation and amplification of THz electromagnetic waves

Energy Technology Data Exchange (ETDEWEB)

Safari, S.; Jazi, B., E-mail: jaziada@kashanu.ac.ir [Department of Laser and Photonics, Faculty of Physics, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of); Jahanbakht, S. [Department of Communications Engineering, Faculty of Electrical And Computer Engineering, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of)

2016-08-15

In this work, two stream instability in a metallic waveguide with elliptical cross-section and with a hollow annular dielectric layer is studied for generation and amplification of THz electromagnetic waves. Dispersion relation of waves and their dependents to geometric dimensions and characteristics of the electron beam are analyzed. In continuation, the diagrams of growth rate for some operating frequencies are presented, so that effective factors on the growth rates, such as geometrical dimensions, dielectric constant of dielectric layer, accelerating voltage, and applied current intensity are analyzed. It is shown that while an electron beam is responsible for instability, another electron beam plays a stabilizing role.

CIRCULARLY POLARIZED SLOTTED APERTURE ANTENNA WITH COPLANAR WAVEGUIDE FED FOR BROADBAND APPLICATIONS

Directory of Open Access Journals (Sweden)

B. T. P. MADHAV

2016-02-01

Full Text Available Coplanar waveguide fed circularly polarized microstrip patch antenna performance evaluation is presented in this paper. The broadband characteristics are attained by placing open end slot at the lower side of the antenna. The proposed design has the return loss of less than -10dB and VSWR<2 in the desired band of operation. A gain of 3dB to 4dB is attained in the desired band with good radiation characteristics and a suitable axial ratio of less than 3 dB is attained in the prescribed band of operation. Proposed antenna is fabricated on the FR4 substrate with dielectric constant of 4.4. Parametric analysis with change in substrate permittivity also performed and the optimized dimensions are presented in this work.

Broadband waveguided light sources

NARCIS (Netherlands)

Pollnau, Markus

In recent years, broadband fiber interferometers have become very popular as basic instruments used in optical low-coherence reflectometry for diagnostics of fiber and integrated optics devices or in optical coherence tomography (OCT) for imaging applications in the biomedical field. The

On-chip broadband ultra-compact optical couplers and polarization splitters based on off-centered and non-symmetric slotted Si-wire waveguides

Science.gov (United States)

Haldar, Raktim; Mishra, V.; Dutt, Avik; Varshney, Shailendra K.

2016-10-01

In this work, we propose novel schemes to design on-chip ultra-compact optical directional couplers (DC) and broadband polarization beam splitters (PBS) based on off-centered and asymmetric dielectric slot waveguides, respectively. Slot dimensions and positions are optimized to achieve maximum coupling coefficients between two symmetric and non-symmetric slotted Si wire waveguides through overlap integral method. We observe >88% of enhancement in the coupling coefficients when the size-optimized slots are placed in optimal positions, with respect to the same waveguides with no slot. When the waveguides are parallel, in that case, a coupling length as short as 1.73 μm is accomplished for TM mode with the off-centered and optimized slots. This scheme enables us to design optical DC with very small footprint, L c ∼ 0.9 μm in the presence of S-bends. We also report a compact (L c ∼ 1.1 μm) on-chip broadband PBS with hybrid slots. Extinction ratios of 13 dB and 22.3 dB are realized with very low insertion loss (0.055 dB and 0.008 dB) for TM and TE modes at 1.55 μm, respectively. The designed PBS exhibits a bandwidth of 78 nm for the TM mode (C-and partial L-bands) and >100 nm for the TE mode (S + C + L wavelength bands). Such on-chip devices can be used to design compact photonic interconnects and quantum information processing units efficiently. We have also investigated the fabrication tolerances of the proposed devices and described the fabrication steps to realize such hybrid devices. Our results are in good agreement with 3D FDTD simulations.

An ultra-broadband multilayered graphene absorber

KAUST Repository

Amin, Muhammad; Farhat, Mohamed; Bagci, Hakan

2013-01-01

An ultra-broadband multilayered graphene absorber operating at terahertz (THz) frequencies is proposed. The absorber design makes use of three mechanisms: (i) The graphene layers are asymmetrically patterned to support higher order surface plasmon

Microfabricated Waveguide Atom Traps.

Energy Technology Data Exchange (ETDEWEB)

Jau, Yuan-Yu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-09-01

A nanoscale , microfabricated waveguide structure can in - principle be used to trap atoms in well - defined locations and enable strong photon-atom interactions . A neutral - atom platform based on this microfabrication technology will be prealigned , which is especially important for quantum - control applications. At present, there is still no reported demonstration of evanescent - field atom trapping using a microfabricated waveguide structure. We described the capabilities established by our team for future development of the waveguide atom - trapping technology at SNL and report our studies to overcome the technical challenges of loading cold atoms into the waveguide atom traps, efficient and broadband optical coupling to a waveguide, and the waveguide material for high - power optical transmission. From the atomic - physics and the waveguide modeling, w e have shown that a square nano-waveguide can be utilized t o achieve better atomic spin squeezing than using a nanofiber for first time.

Broadband silicon polarization beam splitter with a high extinction ratio using a triple-bent-waveguide directional coupler.

Science.gov (United States)

Ong, Jun Rong; Ang, Thomas Y L; Sahin, Ezgi; Pawlina, Bryan; Chen, G F R; Tan, D T H; Lim, Soon Thor; Png, Ching Eng

2017-11-01

We report on the design and experimental demonstration of a broadband silicon polarization beam splitter (PBS) with a high extinction ratio (ER)≥30  dB. This was achieved using triple-bent-waveguide directional coupling in a single PBS, and cascaded PBS topology. For the single PBS, the bandwidths for an ER≥30  dB are 20 nm for the quasi-TE mode, and 70 nm for the quasi-TM mode when a broadband light source (1520-1610 nm) was employed. The insertion loss (IL) varies from 0.2 to 1 dB for the quasi-TE mode and 0.2-2 dB for the quasi-TM mode. The cascaded PBS improved the bandwidth of the quasi-TE mode for an ER≥30  dB to 90 nm, with a low IL of 0.2-2 dB. To the best of our knowledge, our PBS system is one of the best broadband PBSs with an ER as high as ∼42  dB and a low IL below 1 dB around the central wavelength, and experimentally demonstrated using edge-coupling.

A tunable, linac based, intense, broad-band THz source forpump-probe experiments

Energy Technology Data Exchange (ETDEWEB)

Schmerge, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Adolphsen, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Corbett, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Dolgashev, V. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Durr, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fazio, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fisher, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Frisch, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gaffney, K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Guehr, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hastings, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hettel, B. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hoffmann, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hogan, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Holtkamp, N. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, X. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Kirchmann, P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); LaRue, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Limborg, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lindenberg, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Loos, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Maxwell, T. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Nilsson, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Raubenheimer, T. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Reis, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ross, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Shen, Z. -X. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stupakov, G. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tantawi, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tian, K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Wu, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Xiang, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Yakimenko, V. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

2015-02-02

We propose an intense THz source with tunable frequency and bandwidth that can directly interact with the degrees of freedom that determine the properties of materials and thus provides a new tool for controlling and directing these ultrafast processes as well as aiding synthesis of new materials with new functional properties. This THz source will broadly impact our understanding of dynamical processes in matter at the atomic-scale and in real time. Established optical pumping schemes using femtosecond visible frequency laser pulses for excitation are extended into the THz frequency regime thereby enabling resonant excitation of bonds in correlated solid state materials (phonon pumping), to drive low energy electronic excitations, to trigger surface chemistry reactions, and to all-optically bias a material with ultrashort electric fields or magnetic fields. A linac-based THz source can supply stand-alone experiments with peak intensities two orders of magnitude stronger than existing laser-based sources, but when coupled with atomic-scale sensitive femtosecond x-ray probes it opens a new frontier in ultrafast science with broad applications to correlated materials, interfacial and liquid phase chemistry, and materials in extreme conditions.

Very high power THz radiation at Jefferson Lab

International Nuclear Information System (INIS)

Carr, G.L.; Martin, Michael C.; McKinney, Wayne R.; Jordan, K.; Neil, George R.; Williams, G.P.

2002-01-01

We report the production of high power (20 watts average, ∼;1 Megawatt peak) broadband THz light based on coherent emission from relativistic electrons. We describe the source, presenting theoretical calculations and their experimental verification. For clarity we compare this source with one based on ultrafast laser techniques, and in fact the radiation has qualities closely analogous to that produced by such sources, namely that it is spatially coherent, and comprises short duration pulses with transform-limited spectral content. In contrast to conventional THz radiation, however, the intensity is many orders of magnitude greater due to the relativistic enhancement

Theoretical and experimental study on broadband terahertz atmospheric transmission characteristics

International Nuclear Information System (INIS)

Guo Shi-Bei; Zhong Kai; Wang Mao-Rong; Liu Chu; Xu De-Gang; Yao Jian-Quan; Xiao Yong; Wang Wen-Peng

2017-01-01

Broadband terahertz (THz) atmospheric transmission characteristics from 0 to 8 THz are theoretically simulated based on a standard Van Vleck–Weisskopf line shape, considering 1696 water absorption lines and 298 oxygen absorption lines. The influences of humidity, temperature, and pressure on the THz atmospheric absorption are analyzed and experimentally verified with a Fourier transform infrared spectrometer (FTIR) system, showing good consistency. The investigation and evaluation on high-frequency atmospheric windows are good supplements to existing data in the low-frequency range and lay the foundation for aircraft-based high-altitude applications of THz communication and radar. (paper)

High-efficiency THz modulator based on phthalocyanine-compound organic films

International Nuclear Information System (INIS)

He, Ting; Zhang, Bo; Shen, Jingling; Zang, Mengdi; Chen, Tianji; Hu, Yufeng; Hou, Yanbing

2015-01-01

We report a high efficiency, broadband terahertz (THz) modulator following a study of phthalocyanine-compound organic films irradiated with an external excitation laser. Both transmission and reflection modulations of each organic/silicon bilayers were measured using THz time-domain and continuous-wave systems. For very low intensities, the experimental results show that AlClPc/Si can achieve a high modulation factor for transmission and reflection, indicating that AlClPc/Si has a superior modulation efficiency compared with the other films (CuPc and SnCl 2 Pc). In contrast, the strong attenuation of the transmitted and reflected THz waves revealed that a nonlinear absorption process takes place at the organic/silicon interface

Terahertz light-emitting graphene-channel transistor toward single-mode lasing

Science.gov (United States)

Yadav, Deepika; Tamamushi, Gen; Watanabe, Takayuki; Mitsushio, Junki; Tobah, Youssef; Sugawara, Kenta; Dubinov, Alexander A.; Satou, Akira; Ryzhii, Maxim; Ryzhii, Victor; Otsuji, Taiichi

2018-03-01

A distributed feedback dual-gate graphene-channel field-effect transistor (DFB-DG-GFET) was fabricated as a current-injection terahertz (THz) light-emitting laser transistor. We observed a broadband emission in a 1-7.6-THz range with a maximum radiation power of 10 μW as well as a single-mode emission at 5.2 THz with a radiation power of 0.1 μW both at 100 K when the carrier injection stays between the lower cutoff and upper cutoff threshold levels. The device also exhibited peculiar nonlinear threshold-like behavior with respect to the current-injection level. The LED-like broadband emission is interpreted as an amplified spontaneous THz emission being transcended to a single-mode lasing. Design constraints on waveguide structures for better THz photon field confinement with higher gain overlapping as well as DFB cavity structures with higher Q factors are also addressed towards intense, single-mode continuous wave THz lasing at room temperature.

Ultra-compact broadband higher order-mode pass filter fabricated in a silicon waveguide for multimode photonics

DEFF Research Database (Denmark)

Guan, Xiaowei; Ding, Yunhong; Frandsen, Lars Hagedorn

2015-01-01

An ultra-compact and broadband higher order-mode pass filter in a 1D photonic crystal silicon waveguide is proposed and experimentally demonstrated. The photonic crystal is designed for the lower order mode to work in the photonic band gap, while the higher order mode is located in the air band....... Consequently, light on the lower order mode is prohibited to pass through the filter, while light on a higher order mode can be converted to a Bloch mode in the photonic crystal and pass through the filter with low insertion loss. As an example, we fabricate a similar to 15-mu m-long first-order-mode pass...

Spatial-temporal dynamics of broadband terahertz Bessel beam propagation

International Nuclear Information System (INIS)

Semenova, V A; Kulya, M S; Bespalov, V G

2016-01-01

The unique properties of narrowband and broadband terahertz Bessel beams have led to a number of their applications in different fields, for example, for the depth of focusing and resolution enhancement in terahertz imaging. However, broadband terahertz Bessel beams can probably be also used for the diffraction minimization in the short-range broadband terahertz communications. For this purpose, the study of spatial-temporal dynamics of the broadband terahertz Bessel beams is needed. Here we present a simulation-based study of the propagating in non-dispersive medium broadband Bessel beams generated by a conical axicon lens. The algorithm based on scalar diffraction theory was used to obtain the spatial amplitude and phase distributions of the Bessel beam in the frequency range from 0.1 to 3 THz at the distances 10-200 mm from the axicon. Bessel beam field is studied for the different spectral components of the initial pulse. The simulation results show that for the given parameters of the axicon lens one can obtain the Gauss-Bessel beam generation in the spectral range from 0.1 to 3 THz. The length of non-diffraction propagation for a different spectral components was measured, and it was shown that for all spectral components of the initial pulse this length is about 130 mm. (paper)

Integrated Broadband Quantum Cascade Laser

Science.gov (United States)

Mansour, Kamjou (Inventor); Soibel, Alexander (Inventor)

2016-01-01

A broadband, integrated quantum cascade laser is disclosed, comprising ridge waveguide quantum cascade lasers formed by applying standard semiconductor process techniques to a monolithic structure of alternating layers of claddings and active region layers. The resulting ridge waveguide quantum cascade lasers may be individually controlled by independent voltage potentials, resulting in control of the overall spectrum of the integrated quantum cascade laser source. Other embodiments are described and claimed.

Terahertz particle-in-liquid sensing with spoof surface plasmon polariton waveguides

Directory of Open Access Journals (Sweden)

Zhijie Ma

2017-11-01

Full Text Available We present a highly sensitive microfluidic sensing technique for the terahertz (THz region of the electromagnetic spectrum based on spoof surface plasmon polaritons (SPPs. By integrating a microfluidic channel in a spoof SPP waveguide, we take advantage of these highly confined electromagnetic modes to create a platform for dielectric sensing of liquids. Our design consists of a domino waveguide, that is, a series of periodically arranged rectangular metal blocks on top of a metal surface that supports the propagation of spoof SPPs. Through numerical simulations, we demonstrate that the transmission of spoof SPPs along the waveguide is extremely sensitive to the refractive index of a liquid flowing through a microfluidic channel crossing the waveguide to give an interaction volume on the nanoliter scale. Furthermore, by taking advantage of the insensitivity of the domino waveguide’s fundamental spoof SPP mode to the lateral width of the metal blocks, we design a tapered waveguide able to achieve further confinement of the electromagnetic field. Using this approach, we demonstrate the highly sensitive detection of individual subwavelength micro-particles flowing in the liquid. These results are promising for the creation of spoof SPP based THz lab-on-a-chip microfluidic devices that are suitable for the analysis of biological liquids such as proteins and circulating tumour cells in buffer solution.

A reflective-backing-free metamaterial absorber with broadband response

Directory of Open Access Journals (Sweden)

Cuilian Xu

2017-06-01

Full Text Available In this paper, we propose a polarization-independent and broadband perfect infrared (IR metamaterial absorber (MA without reflective backing. The proposed absorber is a periodic meta-atom array consisting of metal-dielectric-multilayer truncated cones which can absorb 80% EM wave from 50.70 to 81.87THz, while transmit 80% EM wave from 0 to 37.71THz. With the decreasing of frequency, the transmissivity increases, which is close to 100% from 0 to 5THz. We can broaden the absorption bandwidth of the MA by cascading multi-layers truncated cones. Furthermore, the proposed IR MA promises to be one desirable stealth material for radar-IR compatibility.

Broadband terahertz spectroscopy: principles, fundamental research and potential for industrial applications

International Nuclear Information System (INIS)

Zouaghi, W; Thomson, M D; Rabia, K; Hahn, R; Blank, V; Roskos, H G

2013-01-01

Terahertz radiation (also called T-rays) can be employed for spectroscopy and imaging, from the laboratory to industrial applications. In this paper we give an overview of how broadband optoelectronic THz techniques (i.e. using optical lasers to achieve THz generation and detection) can be implemented, and give examples of their unique use in solid-state physics, and in biological and industrial applications. (paper)

Application of Plasma Waveguides to High Energy Accelerators

Energy Technology Data Exchange (ETDEWEB)

Milchberg, Howard M

2013-03-30

will continue our development of advanced simulation tools by modifying the QuickPIC algorithm to allow for the simulation of plasma particle pick-up by the wake fields. We have also performed extensive simulations of plasma slow wave structures for efficient THz generation by guided laser beams or accelerated electron beams. We will pursue experimental studies of direct laser acceleration, and THz generation by two methods, ponderomotive-induced THz polarization, and THz radiation by laser accelerated electron beams. We also plan to study both conventional and corrugated plasma channels using our new 30 TW in our new lab facilities. We will investigate production of very long hydrogen plasma waveguides (5 cm). We will study guiding at increasing power levels through the onset of laser-induced cavitation (bubble regime) to assess the role played by the preformed channel. Experiments in direct acceleration will be performed, using laser plasma wakefields as the electron injector. Finally, we will use 2-colour ionization of gases as a high frequency THz source (<60 THz) in order for femtosecond measurements of low plasma densities in waveguides and beams.

Unsupervised image segmentation for passive THz broadband images for concealed weapon detection

Science.gov (United States)

Ramírez, Mabel D.; Dietlein, Charles R.; Grossman, Erich; Popović, Zoya

2007-04-01

This work presents the application of a basic unsupervised classification algorithm for the segmentation of indoor passive Terahertz images. The 30,000 pixel broadband images of a person with concealed weapons under clothing are taken at a range of 0.8-2m over a frequency range of 0.1-1.2THz using single-pixel row-based raster scanning. The spiral-antenna coupled 36x1x0.02μm Nb bridge cryogenic micro-bolometers are developed at NIST-Optoelectronics Division. The antenna is evaporated on a 250μm thick Si substrate with a 4mm diameter hyper-hemispherical Si lens. The NETD of the microbolometer is 125mK at an integration time of 30 ms. The background temperature calibration is performed with a known 25 pixel source above 330 K, and a measured background fluctuation of 200-500mK. Several weapons were concealed under different fabrics: cotton, polyester, windblocker jacket and thermal sweater. Measured temperature contrasts ranged from 0.5-1K for wrinkles in clothing to 5K for a zipper and 8K for the concealed weapon. In order to automate feature detection in the images, some image processing and pattern recognition techniques have been applied and the results are presented here. We show that even simple algorithms, that can potentially be performed in real time, are capable of differentiating between a metal and a dielectric object concealed under clothing. Additionally, we show that pre-processing can reveal low temperature contrast features, such as folds in clothing.

Novel materials, fabrication techniques and algorithms for microwave and THz components, systems and applications

Science.gov (United States)

Liang, Min

This dissertation presents the investigation of several additive manufactured components in RF and THz frequency, as well as the applications of gradient index lens based direction of arrival (DOA) estimation system and broadband electronically beam scanning system. Also, a polymer matrix composite method to achieve artificially controlled effective dielectric properties for 3D printing material is studied. Moreover, the characterization of carbon based nano-materials at microwave and THz frequency, photoconductive antenna array based Terahertz time-domain spectroscopy (THz-TDS) near field imaging system, and a compressive sensing based microwave imaging system is discussed in this dissertation. First, the design, fabrication and characterization of several 3D printed components in microwave and THz frequency are presented. These components include 3D printed broadband Luneburg lens, 3D printed patch antenna, 3D printed multilayer microstrip line structure with vertical transition, THz all-dielectric EMXT waveguide to planar microstrip transition structure and 3D printed dielectric reflectarrays. Second, the additive manufactured 3D Luneburg Lens is employed for DOA estimation application. Using the special property of a Luneburg lens that every point on the surface of the Lens is the focal point of a plane wave incident from the opposite side, 36 detectors are mounted around the surface of the lens to estimate the direction of arrival (DOA) of a microwave signal. The direction finding results using a correlation algorithm show that the averaged error is smaller than 1º for all 360 degree incident angles. Third, a novel broadband electronic scanning system based on Luneburg lens phased array structure is reported. The radiation elements of the phased array are mounted around the surface of a Luneburg lens. By controlling the phase and amplitude of only a few adjacent elements, electronic beam scanning with various radiation patterns can be easily achieved

Broadband temperature-insensitivity of dispersion-engineered waveguides and resonators

Science.gov (United States)

Xu, Lijuan; He, Liuqing; Guo, Yuhao; Li, Guifang; Zhang, Lin

2018-02-01

Photonic circuits suffer from thermal drift of device performance, which is a key obstacle to the development of commercial optoelectronic products. Temperature-insensitive integrated waveguides and resonators have been demonstrated by using materials with a negative TOC at a single wavelength, which are not suitable for WDM devices and wideband nonlinear devices. Here, we propose a waveguide structure with temperature-insensitivity over a bandwidth of 780 nm (1280 to 2060 nm) with an ultra-small effective TOC within +/-1×10-6/K. Uniquely, the waveguide has small anomalous dispersion (from 66 to 329 ps/nm/km) over the same band and is suitable for frequency comb generation without being affected by intra-cavity thermal dynamics.

Broadband and scalable optical coupling for silicon photonics using polymer waveguides

Science.gov (United States)

La Porta, Antonio; Weiss, Jonas; Dangel, Roger; Jubin, Daniel; Meier, Norbert; Horst, Folkert; Offrein, Bert Jan

2018-04-01

We present optical coupling schemes for silicon integrated photonics circuits that account for the challenges in large-scale data processing systems such as those used for emerging big data workloads. Our waveguide based approach allows to optimally exploit the on-chip optical feature size, and chip- and package real-estate. It further scales well to high numbers of channels and is compatible with state-of-the-art flip-chip die packaging. We demonstrate silicon waveguide to polymer waveguide coupling losses below 1.5 dB for both the O- and C-bands with a polarisation dependent loss of <1 dB. Over 100 optical silicon waveguide to polymer waveguide interfaces were assembled within a single alignment step, resulting in a physical I/O channel density of up to 13 waveguides per millimetre along the chip-edge, with an average coupling loss of below 3.4 dB measured at 1310 nm.

Integration of a terahertz quantum cascade laser with a hollow waveguide

Science.gov (United States)

Wanke, Michael C [Albuquerque, NM; Nordquist, Christopher D [Albuquerque, NM

2012-07-03

The present invention is directed to the integration of a quantum cascade laser with a hollow waveguide on a chip to improve both the beam pattern and manufacturability. By coupling the QCL output into a single-mode rectangular waveguide the radiation mode structure can be known and the propagation, manipulation, and broadcast of the QCL radiation can then be entirely controlled by well-established rectangular waveguide techniques. By controlling the impedance of the interface, enhanced functions, such as creating amplifiers, efficient coupling to external cavities, and increasing power output from metal-metal THz QCLs, are also enabled.

THz Tube Waveguides With Low Loss, Low Dispersion, and High Bandwidth

DEFF Research Database (Denmark)

Bao, Hualong; Nielsen, Kristian; Bang, Ole

2014-01-01

We propose, model and experimentally characterize a novel class of terahertz hollow-core tube waveguides with high-loss cladding material, resulting in propagation with low loss, low dispersion, and high useful bandwidth.......We propose, model and experimentally characterize a novel class of terahertz hollow-core tube waveguides with high-loss cladding material, resulting in propagation with low loss, low dispersion, and high useful bandwidth....

A Low-Noise CMOS THz Imager Based on Source Modulation and an In-Pixel High-Q Passive Switched-Capacitor N-Path Filter

Science.gov (United States)

Boukhayma, Assim; Dupret, Antoine; Rostaing, Jean-Pierre; Enz, Christian

2016-01-01

This paper presents the first low noise complementary metal oxide semiconductor (CMOS) terahertz (THz) imager based on source modulation and in-pixel high-Q filtering. The 31×31 focal plane array has been fully integrated in a 0.13μm standard CMOS process. The sensitivity has been improved significantly by modulating the active THz source that lights the scene and performing on-chip high-Q filtering. Each pixel encompass a broadband bow tie antenna coupled to an N-type metal-oxide-semiconductor (NMOS) detector that shifts the THz radiation, a low noise adjustable gain amplifier and a high-Q filter centered at the modulation frequency. The filter is based on a passive switched-capacitor (SC) N-path filter combined with a continuous-time broad-band Gm-C filter. A simplified analysis that helps in designing and tuning the passive SC N-path filter is provided. The characterization of the readout chain shows that a Q factor of 100 has been achieved for the filter with a good matching between the analytical calculation and the measurement results. An input-referred noise of 0.2μV RMS has been measured. Characterization of the chip with different THz wavelengths confirms the broadband feature of the antenna and shows that this THz imager reaches a total noise equivalent power of 0.6 nW at 270 GHz and 0.8 nW at 600 GHz. PMID:26950131

A Low-Noise CMOS THz Imager Based on Source Modulation and an In-Pixel High-Q Passive Switched-Capacitor N-Path Filter.

Science.gov (United States)

Boukhayma, Assim; Dupret, Antoine; Rostaing, Jean-Pierre; Enz, Christian

2016-03-03

This paper presents the first low noise complementary metal oxide semiconductor (CMOS) deletedCMOS terahertz (THz) imager based on source modulation and in-pixel high-Q filtering. The 31 × 31 focal plane array has been fully integrated in a 0 . 13 μ m standard CMOS process. The sensitivity has been improved significantly by modulating the active THz source that lights the scene and performing on-chip high-Q filtering. Each pixel encompass a broadband bow tie antenna coupled to an N-type metal-oxide-semiconductor (NMOS) detector that shifts the THz radiation, a low noise adjustable gain amplifier and a high-Q filter centered at the modulation frequency. The filter is based on a passive switched-capacitor (SC) N-path filter combined with a continuous-time broad-band Gm-C filter. A simplified analysis that helps in designing and tuning the passive SC N-path filter is provided. The characterization of the readout chain shows that a Q factor of 100 has been achieved for the filter with a good matching between the analytical calculation and the measurement results. An input-referred noise of 0 . 2 μ V RMS has been measured. Characterization of the chip with different THz wavelengths confirms the broadband feature of the antenna and shows that this THz imager reaches a total noise equivalent power of 0 . 6 nW at 270 GHz and 0 . 8 nW at 600 GHz.

Fano resonances in a high-Q terahertz whispering-gallery mode resonator coupled to a multi-mode waveguide.

Science.gov (United States)

Vogt, Dominik Walter; Leonhardt, Rainer

2017-11-01

We report on Fano resonances in a high-quality (Q) whispering-gallery mode (WGM) spherical resonator coupled to a multi-mode waveguide in the terahertz (THz) frequency range. The asymmetric line shape and phase of the Fano resonances detected with coherent continuous-wave (CW) THz spectroscopy measurements are in excellent agreement with the analytical model. A very high Q factor of 1600, and a finesse of 22 at critical coupling is observed around 0.35 THz. To the best of our knowledge this is the highest Q factor ever reported for a THz WGM resonator.

Broadband luminescent materials in waveguide geometry

NARCIS (Netherlands)

Pollnau, Markus

In recent years, broadband fiber interferometers have become very popular as basic instruments used in optical low-coherence reflectometry for diagnostics of fiber and integrated optics devices or in optical coherence tomography (OCT) for imaging applications in the biomedical field. The

Phase locking of a 2.7 THz quantum cascade laser to a microwave reference

NARCIS (Netherlands)

Khosropanah, P.; Baryshev, A.; Zhang, W.; Jellema, W.; Hovenier, J.N.; Gao, J.R.; Klapwijk, T.M.; Paveliev, D.G.; Williams, B.S.; Kumar, S.; Hu, Q.; Reno, J.L.; Klein, B.; Hesler, J.L.

2009-01-01

We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain

Phase locking of a 2.7 THz quantum cascade laser to a microwave reference

NARCIS (Netherlands)

Khosropanah, P.; Baryshev, A.; Zhang, W.; Jellema, W.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Paveliev, D. G.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L.; Klein, B.; Hesler, J. L.

2009-01-01

We demonstrate the phase locking of a 2.7 THz metal-metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain

Broadband sub-THz spectroscopy modules integrated in 65-nm CMOS technology

NARCIS (Netherlands)

Matters-Kammerer, M.K.; van Goor, D.; Tripodi, L.

2017-01-01

The design and characterization of a broadband 20-480 GHz continuously tuneable on-chip spectrometer based on non-linear transmission lines in 65-nm CMOS technology is presented. The design procedure of the sampler that detects the ultra-broadband signal from the transmitter in time and frequency

Optical Cherenkov radiation in an As2S3 slot waveguide with four zero-dispersion wavelengths

DEFF Research Database (Denmark)

Wang, Shaofei; Hu, Jungao; Guo, Hairun

2013-01-01

, dispersion profiles with four zero dispersion wavelengths are found to produce a phase-matching nonlinear process leading to a broadband resonant radiation. The broadband OCR investigated in the chalcogenide waveguide may find applications in on-chip wavelength conversion and near-infrared pulse generation.......We propose an approach for an efficient generation of optical Cherenkov radiation (OCR) in the near-infrared by tailoring the waveguide dispersion for a zero group-velocity mismatching between the radiation and the pump soliton. Based on an As2S3 slot waveguide with subwavelength dimensions...

Detection of Threat Materials Using Terahertz Waveguides and Long Pathlength Terahertz Spectroscopy

Science.gov (United States)

2015-05-01

34Temperature dependent characterization of THz vibrations of explosives and related threat materials," Joseph S. Melinger, S. Sree Harsha, N. Laman ...materials,” Joseph S. Melinger, S. Sree Harsha, N. Laman , and D. Grischkowsky, Proc. SPIE 7671, 76710H (2010) Presentations: 1. ”Broadband THz...of crystal structures with poor data,” Acta Crystallogr. B 31(7), 1864–1869 (1975). 10) Joseph S. Melinger, S. Sree Harsha, N. Laman and D

A hybrid plasmonic waveguide terahertz quantum cascade laser

Energy Technology Data Exchange (ETDEWEB)

Degl' Innocenti, Riccardo, E-mail: rd448@cam.ac.uk; Shah, Yash D.; Wallis, Robert; Klimont, Adam; Ren, Yuan; Jessop, David S.; Beere, Harvey E.; Ritchie, David A. [Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

2015-02-23

We present the realization of a quantum cascade laser emitting at around 2.85 THz, based on a hybrid plasmonic waveguide with a low refractive index dielectric cladding. This hybrid waveguide design allows the performance of a double-metal waveguide to be retained, while improving the emission far-field. A set of lasers based on the same active region material were fabricated with different metal layer thicknesses. A detailed characterization of the performance of these lasers revealed that there is an optimal trade-off that yields the best far-field emission and the maximum temperature of operation. By exploiting the pure plasmonic mode of these waveguides, the standard operation conditions of a double-metal quantum cascade laser were retrieved, such that the maximum operating temperature of these devices is not affected by the process. These results pave the way to realizing a class of integrated devices working in the terahertz range which could be further exploited to fabricate terahertz on-chip circuitry.

Scheme for generating and transporting THz radiation to the X-ray experimental hall at the European XFEL

Energy Technology Data Exchange (ETDEWEB)

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

2011-12-15

The design of a THz edge radiation source for the European XFEL is presented.We consider generation of THz radiation from the spent electron beam downstream of the SASE2 undulator in the electron beam dump area. In this way, the THz output must propagate at least for 250 meters through the photon beam tunnel to the experimental hall to reach the SASE2 X-ray hutches. We propose to use an open beam waveguide such as an iris guide as transmission line. In order to efficiently couple radiation into the iris transmission line, generation of the THz radiation pulse can be performed directly within the iris guide. The line transporting the THz radiation to the SASE2 X-ray hutches introduces a path delay of about 20 m. Since THz pump/X-ray probe experiments should be enabled, we propose to exploit the European XFEL baseline multi-bunch mode of operation, with 222 ns electron bunch separation, in order to cope with the delay between THz and X-ray pulses. We present start-to-end simulations for 1 nC bunch operation-parameters, optimized for THz pump/X-ray probe experiments.Detailed characterization of the THz and SASE X-ray radiation pulses is performed. Highly focused THz beams will approach the high field limit of 1 V/atomic size. (orig.)

Bright THz Instrument and Nonlinear THz Science

Science.gov (United States)

2017-10-30

Report: Bright THz Instrument and Nonlinear THz Science The views, opinions and/or findings contained in this report are those of the author(s) and...Number: W911NF-16-1-0436 Organization: University of Rochester Title: Bright THz Instrument and Nonlinear THz Science Report Term: 0-Other Email: xi...exploring new cutting-edge research and broader applications, following the significant development of THz science and technology in the late 80’s, is the

Extremely broadband, on-chip optical nonreciprocity enabled by mimicking nonlinear anti-adiabatic quantum jumps near exceptional points.

Science.gov (United States)

Choi, Youngsun; Hahn, Choloong; Yoon, Jae Woong; Song, Seok Ho; Berini, Pierre

2017-01-20

Time-asymmetric state-evolution properties while encircling an exceptional point are presently of great interest in search of new principles for controlling atomic and optical systems. Here, we show that encircling-an-exceptional-point interactions that are essentially reciprocal in the linear interaction regime make a plausible nonlinear integrated optical device architecture highly nonreciprocal over an extremely broad spectrum. In the proposed strategy, we describe an experimentally realizable coupled-waveguide structure that supports an encircling-an-exceptional-point parametric evolution under the influence of a gain saturation nonlinearity. Using an intuitive time-dependent Hamiltonian and rigorous numerical computations, we demonstrate strictly nonreciprocal optical transmission with a forward-to-backward transmission ratio exceeding 10 dB and high forward transmission efficiency (∼100%) persisting over an extremely broad bandwidth approaching 100 THz. This predicted performance strongly encourages experimental realization of the proposed concept to establish a practical on-chip optical nonreciprocal element for ultra-short laser pulses and broadband high-density optical signal processing.

THz near-field imaging of biological tissues employing synchrotronradiation

Energy Technology Data Exchange (ETDEWEB)

Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried,Daniel

2004-12-23

Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking onto the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical wave guides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about lambda/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 mu-m at about 12 wave numbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin.

BROADBAND TRAVELLING WAVE SEMICONDUCTOR OPTICAL AMPLIFIER

DEFF Research Database (Denmark)

2010-01-01

Broadband travelling wave semiconductor optical amplifier (100, 200, 300, 400, 800) for amplification of light, wherein the amplifier (100, 200, 300, 400, 800) comprises a waveguide region (101, 201, 301, 401, 801) for providing confinement of the light in transverse directions and adapted...

X-band EPR setup with THz light excitation of Novosibirsk Free Electron Laser: Goals, means, useful extras

Science.gov (United States)

Veber, Sergey L.; Tumanov, Sergey V.; Fursova, Elena Yu.; Shevchenko, Oleg A.; Getmanov, Yaroslav V.; Scheglov, Mikhail A.; Kubarev, Vitaly V.; Shevchenko, Daria A.; Gorbachev, Iaroslav I.; Salikova, Tatiana V.; Kulipanov, Gennady N.; Ovcharenko, Victor I.; Fedin, Matvey V.

2018-03-01

Electron Paramagnetic Resonance (EPR) station at the Novosibirsk Free Electron Laser (NovoFEL) user facility is described. It is based on X-band (∼9 GHz) EPR spectrometer and operates in both Continuous Wave (CW) and Time-Resolved (TR) modes, each allowing detection of either direct or indirect influence of high-power NovoFEL light (THz and mid-IR) on the spin system under study. The optics components including two parabolic mirrors, shutters, optical chopper and multimodal waveguide allow the light of NovoFEL to be directly fed into the EPR resonator. Characteristics of the NovoFEL radiation, the transmission and polarization-retaining properties of the waveguide used in EPR experiments are presented. The types of proposed experiments accessible using this setup are sketched. In most practical cases the high-power radiation applied to the sample induces its rapid temperature increase (T-jump), which is best visible in TR mode. Although such influence is a by-product of THz radiation, this thermal effect is controllable and can deliberately be used to induce and measure transient signals of arbitrary samples. The advantage of tunable THz radiation is the absence of photo-induced processes in the sample and its high penetration ability, allowing fast heating of a large portion of virtually any sample and inducing intense transients. Such T-jump TR EPR spectroscopy with THz pulses has been previewed for the two test samples, being a useful supplement for the main goals of the created setup.

Ultrashort broadband polarization beam splitter based on a combined hybrid plasmonic waveguide.

Science.gov (United States)

Chang, Ken-Wei; Huang, Chia-Chien

2016-01-20

We propose an ultracompact broadband polarization beam splitter (PBS) based on a combined hybrid plasmonic waveguide (HPW). The proposed PBS separates transverse-electric (TE) and transverse-magnetic (TM) modes using a bent lower HPW with vertical nanoscale gaps and a straight upper HPW with a horizontal nanoscale gap, respectively, without relying on an additional coupling region. This design considerably reduces the length of the PBS to the submicron scale (920 nm, the shortest PBS reported to date) while offering polarization extinction ratios (PERs) of ~19 dB (~18 dB) and insertion losses (ILs) of ~0.6 dB (~0.3 dB) for the TE (TM) mode over an extremely broad band of 400 nm (from λ = 1300 nm to 1700 nm, covering entirely second and third telecom windows). The length of the designed PBS can be reduced further to 620 nm while still offering PERs of 15 dB, realizing a densely photonic integrated circuit. Considering the fabrication tolerance, the designed PBS allows for large geometrical deviations of ± 20 nm while restricting PER variations to within 1 dB, except for those in the nanoscale gaps smaller than 10nm. Additionally, we also address the input and ouput coupling efficiencies of the proposed PBS.

Copper nanorod array assisted silicon waveguide polarization beam splitter.

Science.gov (United States)

Kim, Sangsik; Qi, Minghao

2014-04-21

We present the design of a three-dimensional (3D) polarization beam splitter (PBS) with a copper nanorod array placed between two silicon waveguides. The localized surface plasmon resonance (LSPR) of a metal nanorod array selectively cross-couples transverse electric (TE) mode to the coupler waveguide, while transverse magnetic (TM) mode passes through the original input waveguide without coupling. An ultra-compact and broadband PBS compared to all-dielectric devices is achieved with the LSPR. The output ports of waveguides are designed to support either TM or TE mode only to enhance the extinction ratios. Compared to silver, copper is fully compatible with complementary metal-oxide-semiconductor (CMOS) technology.

THz near-field imaging of biological tissues employing synchrotron radiation

International Nuclear Information System (INIS)

Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried, Daniel

2004-01-01

Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking onto the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical wave guides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about lambda/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 mu-m at about 12 wave numbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin

X-band EPR setup with THz light excitation of Novosibirsk Free Electron Laser: Goals, means, useful extras.

Science.gov (United States)

Veber, Sergey L; Tumanov, Sergey V; Fursova, Elena Yu; Shevchenko, Oleg A; Getmanov, Yaroslav V; Scheglov, Mikhail A; Kubarev, Vitaly V; Shevchenko, Daria A; Gorbachev, Iaroslav I; Salikova, Tatiana V; Kulipanov, Gennady N; Ovcharenko, Victor I; Fedin, Matvey V

2018-03-01

Electron Paramagnetic Resonance (EPR) station at the Novosibirsk Free Electron Laser (NovoFEL) user facility is described. It is based on X-band (∼9 GHz) EPR spectrometer and operates in both Continuous Wave (CW) and Time-Resolved (TR) modes, each allowing detection of either direct or indirect influence of high-power NovoFEL light (THz and mid-IR) on the spin system under study. The optics components including two parabolic mirrors, shutters, optical chopper and multimodal waveguide allow the light of NovoFEL to be directly fed into the EPR resonator. Characteristics of the NovoFEL radiation, the transmission and polarization-retaining properties of the waveguide used in EPR experiments are presented. The types of proposed experiments accessible using this setup are sketched. In most practical cases the high-power radiation applied to the sample induces its rapid temperature increase (T-jump), which is best visible in TR mode. Although such influence is a by-product of THz radiation, this thermal effect is controllable and can deliberately be used to induce and measure transient signals of arbitrary samples. The advantage of tunable THz radiation is the absence of photo-induced processes in the sample and its high penetration ability, allowing fast heating of a large portion of virtually any sample and inducing intense transients. Such T-jump TR EPR spectroscopy with THz pulses has been previewed for the two test samples, being a useful supplement for the main goals of the created setup. Copyright © 2018 Elsevier Inc. All rights reserved.

Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers

DEFF Research Database (Denmark)

Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H. P.

2016-01-01

Frequency-comb-assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this Letter, we present a novel method using cascaded frequency agile diode lasers......, which allows us to extend the measurement bandwidth to 37.4 THz (1355-1630 nm) at megahertz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy, and in particular it enables us to characterize the dispersion...

Wide-angle, polarization-insensitive and broadband absorber based on eight-fold symmetric SRRs metamaterial

Science.gov (United States)

Wu, Dong; Liu, Yumin; Yu, Zhongyuan; Chen, Lei; Ma, Rui; Li, Yutong; Li, Ruifang; Ye, Han

2016-12-01

In this paper, we propose a novel three dimensional metamaterial design with eight-fold rotational symmetry that shows a polarization-insensitive, wide-angle and broadband perfect absorption in the microwave band. By simulation, the polarization-insensitive absorption is over 90% between 26.9 GHz to 32.9 GHz, and the broadband absorption remains a good absorption performance to a wide incident angles for both TE and TM polarizations. The magnetic field distribution are investigated to interpret the physical mechanism of broadband absorption. The broadband absorption is based on overlapping the multiple magnetic resonances at the neighboring frequencies by coupling effects of multiple metallic split-ring resonators (SRRs). Moreover, it is demonstrate that the designed structure can be extended to other frequencies by scale down the size of the unit cell, such as the visible frequencies. The simulated results show that the absorption of the smaller absorber is above 90% in the frequency range from 467 THz to 765 THz(392-642 nm), which include orange to purple light in visible region(400-760nm). The wide-angle and polarization-insensitive stabilities of the smaller absorber is also demonstrated at visible region. The proposed work provides a new design of realization of a polarization-insensitive, wide-angle and broadband absorber ranging different frequency bands, and such a structure has potential application in the fields of solar cell, imaging and detection.

Broadband terahertz wave deflection based on C-shape complex metamaterials with phase discontinuities

KAUST Repository

Zhang, Xueqian; Tian, Zhen; Yue, Weisheng; Gu, Jianqiang; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

2013-01-01

A broadband terahertz wave deflector based on metasurface induced phase discontinuities is reported. Various frequency components ranging from 0.43 to 1.0 THz with polarization orthogonal to the incidence are deflected into a broad range of angles from 25° to 84°. A Fresnel zone plate consequently developed from the beam deflector is capable of focusing a broadband terahertz radiation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Broadband terahertz wave deflection based on C-shape complex metamaterials with phase discontinuities

KAUST Repository

Zhang, Xueqian

2013-06-21

A broadband terahertz wave deflector based on metasurface induced phase discontinuities is reported. Various frequency components ranging from 0.43 to 1.0 THz with polarization orthogonal to the incidence are deflected into a broad range of angles from 25° to 84°. A Fresnel zone plate consequently developed from the beam deflector is capable of focusing a broadband terahertz radiation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tunable Multilayer Graphene Metamaterials for Terahertz/Infrared Waveguide Modulators

DEFF Research Database (Denmark)

Khromova, Irina; Andryieuski, Andrei; Lavrinenko, Andrei

regimes of multilayer graphene-dielectric artificial metamaterials. The interplay between interband and intraband transitions in graphene allows converting the structure into a transparent and/or electromagnetically dense artificial medium. The gate voltage can be used to electrically control...... the concentration of carriers in the graphene sheets and, thus, efficiently change the dispersion of the whole structure. Placed inside a hollow waveguide, a multilayer graphene/dielectric metamaterial provides high-speed modulation and tunable bandpass filtering. The absence of scattered radiation enables dense...... the latter to shift its central frequency by 1:25% per every meV graphene Fermi energy change. We believe that graphene-dielectric multilayer metamaterials will constitute the functional platform for THz-IR waveguide-integrated devices....

Full characterisation of a background limited antenna coupled KID over an octave of bandwidth for THz radiation

NARCIS (Netherlands)

Bueno, J.; Yurduseven, O.; Yates, S. J. C.; Llombart, N.; Murugesan, V.; Thoen, D. J.; Baryshev, A. M.; Neto, A.; Baselmans, J. J. A.

2017-01-01

We present the design, fabrication, and full characterisation (sensitivity, beam pattern, and frequency response) of a background limited broadband antenna coupled kinetic inductance detector covering the frequency range from 1.4 to 2.8 THz. This device shows photon noise limited performance with a

Broadband plasmon induced transparency in terahertz metamaterials

International Nuclear Information System (INIS)

Zhu Zhihua; Yang Xu; Gu Jianqiang; Jiang Jun; Tian Zhen; Han Jiaguang; Zhang Weili; Yue Weisheng; Tonouchi, Masayoshi

2013-01-01

Plasmon induced transparency (PIT) could be realized in metamaterials via interference between different resonance modes. Within the sharp transparency window, the high dispersion of the medium may lead to remarkable slow light phenomena and an enhanced nonlinear effect. However, the transparency mode is normally localized in a narrow frequency band, which thus restricts many of its applications. Here we present the simulation, implementation, and measurement of a broadband PIT metamaterial functioning in the terahertz regime. By integrating four U-shape resonators around a central bar resonator, a broad transparency window across a frequency range greater than 0.40 THz is obtained, with a central resonance frequency located at 1.01 THz. Such PIT metamaterials are promising candidates for designing slow light devices, highly sensitive sensors, and nonlinear elements operating over a broad frequency range. (paper)

Quantum Dots in Photonic Crystal Waveguides

DEFF Research Database (Denmark)

Sollner, Immo Nathanael

This Thesis is focused on the study of quantum electrodynamics in photonic crystal waveguides. We investigate the interplay between a single quantum dot and the fundamental mode of the photonic crystal waveguide. We demonstrate experimental coupling eciencies for the spontaneous emission...... into the mode exceeding 98% for emitters spectrally close to the band-edge of the waveguide mode. In addition we illustrate the broadband nature of the underlying eects, by obtaining coupling eciencies above 90% for quantum dots detuned from the band edge by as far as 20nm. These values are in good agreement...... with numerical simulations. Such a high coupling eciency implies that the system can be considered an articial 1D-atom, and we theoretically show that this system can generate strong photon-photon interaction, which is an essential functionality for deterministic optical quantum information processing. We...

Versatile silicon-waveguide supercontinuum for coherent mid-infrared spectroscopy

Science.gov (United States)

Nader, Nima; Maser, Daniel L.; Cruz, Flavio C.; Kowligy, Abijith; Timmers, Henry; Chiles, Jeff; Fredrick, Connor; Westly, Daron A.; Nam, Sae Woo; Mirin, Richard P.; Shainline, Jeffrey M.; Diddams, Scott

2018-03-01

Laser frequency combs, with their unique combination of precisely defined spectral lines and broad bandwidth, are a powerful tool for basic and applied spectroscopy. Here, we report offset-free, mid-infrared frequency combs and dual-comb spectroscopy through supercontinuum generation in silicon-on-sapphire waveguides. We leverage robust fabrication and geometrical dispersion engineering of nanophotonic waveguides for multi-band, coherent frequency combs spanning 70 THz in the mid-infrared (2.5 μm-6.2 μm). Precise waveguide fabrication provides significant spectral broadening with engineered spectra targeted at specific mid-infrared bands. We characterize the relative-intensity-noise of different bands and show that the measured levels do not pose any limitation for spectroscopy applications. Additionally, we use the fabricated photonic devices to demonstrate dual-comb spectroscopy of a carbonyl sulfide gas sample at 5 μm. This work forms the technological basis for applications such as point sensors for fundamental spectroscopy, atmospheric chemistry, trace and hazardous gas detection, and biological microscopy.

Versatile silicon-waveguide supercontinuum for coherent mid-infrared spectroscopy

Directory of Open Access Journals (Sweden)

Nima Nader

2018-03-01

Full Text Available Laser frequency combs, with their unique combination of precisely defined spectral lines and broad bandwidth, are a powerful tool for basic and applied spectroscopy. Here, we report offset-free, mid-infrared frequency combs and dual-comb spectroscopy through supercontinuum generation in silicon-on-sapphire waveguides. We leverage robust fabrication and geometrical dispersion engineering of nanophotonic waveguides for multi-band, coherent frequency combs spanning 70 THz in the mid-infrared (2.5 μm–6.2 μm. Precise waveguide fabrication provides significant spectral broadening with engineered spectra targeted at specific mid-infrared bands. We characterize the relative-intensity-noise of different bands and show that the measured levels do not pose any limitation for spectroscopy applications. Additionally, we use the fabricated photonic devices to demonstrate dual-comb spectroscopy of a carbonyl sulfide gas sample at 5 μm. This work forms the technological basis for applications such as point sensors for fundamental spectroscopy, atmospheric chemistry, trace and hazardous gas detection, and biological microscopy.

Freely tunable broadband polarization rotator for terahertz waves.

Science.gov (United States)

Fan, Ren-Hao; Zhou, Yu; Ren, Xiao-Ping; Peng, Ru-Wen; Jiang, Shang-Chi; Xu, Di-Hu; Xiong, Xiang; Huang, Xian-Rong; Wang, Mu

2015-02-18

A freely tunable polarization rotator for broadband terahertz waves is demonstrated using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized terahertz wave to any desired direction with nearly perfect conversion efficiency. This low-cost, high-efficiency, and freely tunable device has potential applications as material analysis, wireless communication, and THz imaging. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel crystalline-waveguide broadband light sources for interferometry

NARCIS (Netherlands)

Pollnau, Markus

In recent years, broadband fiber interferometers have become very popular as basic instruments used in optical low-coherence reflectometry for diagnostics of fiber and integrated optics devices or in optical coherence tomography (OCT) for imaging applications in the biomedical field. The

Broadband plasmon induced transparency in terahertz metamaterials

KAUST Repository

Zhu, Zhihua

2013-04-25

Plasmon induced transparency (PIT) could be realized in metamaterials via interference between different resonance modes. Within the sharp transparency window, the high dispersion of the medium may lead to remarkable slow light phenomena and an enhanced nonlinear effect. However, the transparency mode is normally localized in a narrow frequency band, which thus restricts many of its applications. Here we present the simulation, implementation, and measurement of a broadband PIT metamaterial functioning in the terahertz regime. By integrating four U-shape resonators around a central bar resonator, a broad transparency window across a frequency range greater than 0.40 THz is obtained, with a central resonance frequency located at 1.01 THz. Such PIT metamaterials are promising candidates for designing slow light devices, highly sensitive sensors, and nonlinear elements operating over a broad frequency range. © 2013 IOP Publishing Ltd.

RF Performance of Layer-Structured Broadband Passive Millimeter-Wave Imaging System

Directory of Open Access Journals (Sweden)

Kunio Sakakibara

2016-01-01

Full Text Available Low profile and simple configuration are advantageous for RF module in passive millimeter-wave imaging system. High sensitivity over broad operation bandwidth is also necessary to detect right information from weak signal. We propose a broadband layer-structured module with low profile, simple structure, and ease of manufacture. This module is composed of a lens antenna and a detector module that consists of a detector circuit and a broadband microstrip-to-waveguide transition. The module forms a layer structure as a printed substrate with detector circuit is fixed between two metal plates with horn antennas and back-short waveguides. We developed a broadband passive millimeter-wave imaging module composed of a lens antenna and a detector module in this work. The gain and the antenna efficiency were measured, and the broadband operation was observed for the lens antenna. For the detector module, peak sensitivity was 8100 V/W. Furthermore, the detector module recognized a difference in the absorber’s temperature. The designs of the lens antenna and the detector module are presented and the RF performances of these components are reported. Finally, passive millimeter-wave imaging of a car, a human, and a metal plate in clothes is demonstrated in this paper.

Surface-Emitting Distributed Feedback Terahertz Quantum-Cascade Lasers in Metal-Metal Waveguides

Science.gov (United States)

Kumar, Sushil; Williams, Benjamin S.; Qin, Qi; Lee, Alan W. M.; Hu, Qing; Reno, John L.

2007-01-01

Single-mode surface-emitting distributed feedback terahertz quantumcascade lasers operating around 2.9 THz are developed in metal-metal waveguides. A combination of techniques including precise control of phase of reflection at the facets, and u e of metal on the sidewalls to eliminate higher-order lateral modes allow robust single-mode operation over a range of approximately 0.35 THz. Single-lobed far-field radiation pattern is obtained using a pi phase-shift in center of the second-order Bragg grating. A grating device operating at 2.93 THz lased up to 149 K in pulsed mode and a temperature tuning of 19 .7 GHz was observed from 5 K to 147 K. The same device lased up to 78 K in continuous-wave (cw) mode emitting more than 6 m W of cw power at 5 K. ln general, maximum temperature of pulsed operation for grating devices was within a few Kelvin of that of multi-mode Fabry-Perot ridge lasers

Spectroscopic properties and thermal stability of Er3+-doped tungsten-tellurite glass for waveguide amplifier application

International Nuclear Information System (INIS)

Zhao Shilong; Wang Xiuli; Fang Dawei; Xu Shiqing; Hu Lili

2006-01-01

Tungsten-tellurite glass with molar composition of 60TeO 2 -30WO 3 -10Na 2 O has been investigated for developing planar broadband waveguide amplifier application. Spectroscopic properties and thermal stability of Er 3+ -doped tungsten-tellurite glass have been discussed. The results show that the introduction of WO 3 increases significantly the glass transition temperature and the maximum phonon energy. Er 3+ -doped tungsten-tellurite glass exhibits high glass transition temperature (377 deg. C), large emission cross-section (0.91 x 10 -20 cm 2 ) at 1532 nm and broad full width at half maximum (FWHM), which make it preferable for broadband Er 3+ -doped waveguide amplifier application

Ultra-wideband and high-gain parametric amplification in telecom wavelengths with an optimally mode-matched PPLN waveguide.

Science.gov (United States)

Sua, Yong Meng; Chen, Jia-Yang; Huang, Yu-Ping

2018-06-15

We report a wideband optical parametric amplification (OPA) over 14 THz covering telecom S, C, and L bands with observed maximum parametric gain of 38.3 dB. The OPA is realized through cascaded second-harmonic generation and difference-frequency generation (cSHG-DFG) in a 2 cm periodically poled LiNbO 3 (PPLN) waveguide. With tailored cross section geometry, the waveguide is optimally mode matched for efficient cascaded nonlinear wave mixing. We also identify and study the effect of competing nonlinear processes in this cSHG-DFG configuration.

A broadband metamaterial absorber based on multi-layer graphene in the terahertz region

Science.gov (United States)

Fu, Pan; Liu, Fei; Ren, Guang Jun; Su, Fei; Li, Dong; Yao, Jian Quan

2018-06-01

A broadband metamaterial absorber, composed of the periodic graphene pattern on SiO2 dielectric with the double layer graphene films inserted in it and all of them backed by metal plan, is proposed and investigated. The simulation results reveal that the wide absorption band can be flexibly tuned between the low-frequency band and the high-frequency band by adjusting graphene's Fermi level. The absorption can achieve 90% in 5.50-7.10 THz, with Fermi level of graphene is 0.3 eV, while in 6.98-9.10 THz with Fermi level 0.6 eV. Furthermore, the proposed structure can be switched from reflection (>81%) to absorption (>90%) over the whole operation band, when the Fermi level of graphene varies from 0 to 0.6 eV. Besides, the proposed absorber is insensitive to the polarization and can work over a wide range of incident angle. Compared with the previous broadband absorber, our graphene based wideband terahertz absorber can enable a wide application of high performance terahertz devices, including sensors, imaging devices and electro-optic switches.

Full Ka Band Waveguide-to-Microstrip Inline Transition Design

Science.gov (United States)

Li, Jianxing; Li, Lei; Qiao, Yu; Chen, Juan; Chen, Jianzhong; Zhang, Anxue

2018-05-01

In this paper, a compact and broadband inline waveguide-to-microstrip transition is proposed to cover the full Ka band. The transition can be segmented from the electric point of view into three building blocks, comprising a microstrip line to rectangular coaxial line, a wedged rectangular coaxial line to ridged waveguide, and a final tapered ridged waveguide impedance transformer to standard waveguide. Both good electrical performance and simple modular assembly without any soldering have been simultaneously obtained. The validation of the design concept has been conducted by numerical simulations and experimental measurements. The experimental results of a fabricated back-to-back transition prototype coincide with the simulated results. It shows that the proposed transition achieves good return loss of lower than 15.5 dB and low insertion loss with a fluctuation between 0.23 to 0.60 dB across the entire Ka band. Details of design considerations and operation mechanism as well as simulation and measurement results are presented.

THz radiation in KAERI

International Nuclear Information System (INIS)

Jeong, Young Uk; Cha, Hyuk Jin; Ahn, Pildong; Park, Seong Hee; Lee, Byung Cheol

2006-01-01

We have developed a high power terahertz (THz) radiation source by using a compact free electron laser (FEL). The FEL operates in the wavelength range of 100 - 1200 μm, which corresponds to 0.3-3 THz. The peak power of the FEL micropulse having 30 ps pulse duration is 1 kW and the pulse energy of the 3-μs-FEL-macropulse is approximately 0.3 mJ. The main application of the FEL is THz imaging and spectroscopy for bio-medical research and THz material study. We could get the transmitted THz imaging of several materials including bugs without being dryed by using the high power THz FEL. THz spectral characteristics of several materials have been studied by the FEL. We hope that the FEL can be upgraded for a practical source of medical and security inspections. (author)

Analysis on characteristic and application of THz frequency comb and THz sub-comb

International Nuclear Information System (INIS)

Liu Pengxiang; Xu Degang; Yao Jianquan

2011-01-01

In this paper, we proposed a method for THz sub-comb generation based on spectral interference. The result of our calculation indicated that the THz pulse train, generated by surface-emitted optical rectification of femtosecond (fs) laser pulse in periodically poled lithium niobate (PPLN), has a comb-like spectrum. The characteristic of this THz sub-comb was analyzed both in frequency and time domain. Compared with the THz frequency comb emitted by a photoconductive antenna (PCA), THz sub-comb has a lower spectral resolution and wider free spectral range. Thus it could be an ideal source for wavelength division multiplexing (WDM) in THz wireless communication system.

Electro-optic sampling of THz pulses at the CTR source at FLASH

Energy Technology Data Exchange (ETDEWEB)

Wunderlich, Steffen

2012-06-15

Several applications in material science, non-linear optics and solid-state physics require short pulses with a high pulse energy of radiation in the far-infrared and in the terahertz (THz) regime in particular. As described in the following, coherent transition radiation generated by high-relativistic electron bunches at FLASH provides broadband single-cycle pulses of sub-picosecond length. The pulses are characterized using the quantitative and time-resolved technique of electro-optic sampling showing peak field strengths in the order of 1 MV/cm.

Electro-optic sampling of THz pulses at the CTR source at FLASH

International Nuclear Information System (INIS)

Wunderlich, Steffen

2012-06-01

Several applications in material science, non-linear optics and solid-state physics require short pulses with a high pulse energy of radiation in the far-infrared and in the terahertz (THz) regime in particular. As described in the following, coherent transition radiation generated by high-relativistic electron bunches at FLASH provides broadband single-cycle pulses of sub-picosecond length. The pulses are characterized using the quantitative and time-resolved technique of electro-optic sampling showing peak field strengths in the order of 1 MV/cm.

Generation of THz frequency using PANDA ring resonator for THz imaging

Directory of Open Access Journals (Sweden)

Ong CT

2012-02-01

Full Text Available MA Jalil1, Afroozeh Abdolkarim2, T Saktioto2, CT Ong3, Preecha P Yupapin41Ibnu Sina Institute of Fundamental Science Studies, Nanotechnology Research Alliance, Universiti Teknologi Malaysia (UTM,81310, Johor Bahru, Malaysia; 2Institute of Advanced Photonics Science, Nanotechnology Research Alliance, Universiti Teknologi Malaysia (UTM, 81310, Johor Bahru, Malaysia; 3Department of Mathematics, Universiti Teknologi Malaysia 81310 Skudai, Johor Bahru, Malaysia; 4Nanoscale Science and Engineering Research Alliance (N'SERA, Advanced Research Center for Photonics, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, ThailandAbstract: In this study, we have generated terahertz (THz frequency by a novel design of microring resonators for medical applications. The dense wavelength-division multiplexing can be generated and obtained by using a Gaussian pulse propagating within a modified PANDA ring resonator and an add/drop filter system. Our results show that the THz frequency region can be obtained between 40–50 THz. This area of frequency provides a reliable frequency band for THz pulsed imaging.Keywords: THz imaging, THz technology, MRRs, PANDA, add/drop filter

Fractal THz metamaterials

DEFF Research Database (Denmark)

Malureanu, Radu; Jepsen, Peter Uhd; Xiao, S.

2010-01-01

applications. THz radiation can be employed for various purposes, among them the study of vibrations in biological molecules, motion of electrons in semiconductors and propagation of acoustic shock waves in crystals. We propose here a new THz fractal MTM design that shows very high transmission in the desired...... frequency range as well as a clear differentiation between one polarisation and another. Based on theoretical predictions we fabricated and measured a fractal based THz metamaterial that shows more than 60% field transmission at around 1THz for TE polarized light while the TM waves have almost 80% field...... transmission peak at 0.6THz. One of the main characteristics of this design is its tunability by design: by simply changing the length of the fractal elements one can choose the operating frequency window. The modelling, fabrication and characterisation results will be presented in this paper. Due to the long...

Terahertz cross-phase modulation of an optical mode

DEFF Research Database (Denmark)

Lavrinenko, Andrei; Novitsky, Andrey; Zalkovskij, Maksim

2013-01-01

We discuss an optical scheme which facilitates modulation of an optical waveguide mode by metallic-nanoslit-enhanced THz radiation. The waveguide mode acquires an additional phase shift due to THz nonlinearity with fields reachable in experiments.......We discuss an optical scheme which facilitates modulation of an optical waveguide mode by metallic-nanoslit-enhanced THz radiation. The waveguide mode acquires an additional phase shift due to THz nonlinearity with fields reachable in experiments....

Tunable Fano Resonance in Asymmetric MIM Waveguide Structure.

Science.gov (United States)

Zhao, Xuefeng; Zhang, Zhidong; Yan, Shubin

2017-06-25

A plasmonic waveguide coupled system that uses a metal-insulator-metal (MIM) waveguide with two silver baffles and a coupled ring cavity is proposed in this study. The transmission properties of the plasmonic system were investigated using the finite element method. The simulation results show a Fano profile in the transmission spectrum, which was caused by the interaction of the broadband resonance of the Fabry-Perot (F-P) cavity and the narrow band resonance of the ring cavity. The Fabry-Perot (F-P) cavity in this case was formed by two silver baffles dividing the MIM waveguide. The maximum sensitivity of 718 nm/RIU and the maximum figure of merit of 4354 were achieved. Furthermore, the effects of the structural parameters of the F-P cavity and the ring cavity on the transmission properties of the plasmonic system were analyzed. The results can provide a guide for designing highly sensitive on-chip sensors based on surface plasmon polaritons.

Experimental realization of highly efficient broadband coupling of single quantum dots to a photonic crystal waveguide

DEFF Research Database (Denmark)

Lund-Hansen, Toke; Stobbe, Søren; Julsgaard, Brian

2008-01-01

We present time-resolved spontaneous emission measurements of single quantum dots embedded in photonic crystal waveguides. Quantum dots that couple to a photonic crystal waveguide are found to decay up to 27 times faster than uncoupled quantum dots. From these measurements -factors of up to 0.89 ...... taking into account that the light-matter coupling is strongly enhanced due to the significant slow-down of light in the photonic crystal waveguides....

SPP-assisted sub-wavelength reflection-type THz imaging with THz time-domain spectrometer

Science.gov (United States)

Lai, Senfeng; Wu, Yanghui; Wu, Wen; Gu, Wenhua

2017-08-01

THz imaging has become a hot research topic in recent years, thanks to its merits of non-contact, strong penetration, immunity to hostile environments, and nondestructive detection. However, its spatial resolution is limited by the relatively long wavelength, so the location and measurement precision can only reach the level of the imaging wavelength, which has become a severe limitation of THz imaging. A simple way using surface plasmonic polartons (SPPs) to improve the location and measurement precision of THz by one order of magnitude was proposed in this manuscript, which can realize subwavelength THz imaging.

Ultra-small and broadband polarization splitters based on double-slit interference

Energy Technology Data Exchange (ETDEWEB)

Sun, Chengwei; Li, Hongyun [State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, Department of Physics, Peking University, Beijing 100871 (China); Gong, Qihuang; Chen, Jianjun, E-mail: jjchern@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China)

2016-03-07

An ultra-small and broadband polarization splitter is numerically and experimentally demonstrated based on the double-slit interference in a polymer-film-coated double-slit structure. The hybrid slab waveguide (air-polymer-Au) supports both the transverse-magnetic and transverse-electric modes. The incident beam from the back side can excite these two guided modes of orthogonally polarized states in the hybrid structure. By exploiting the difference slit widths and the large mode birefringence, these two guided modes propagate to the opposite directions along the front metal surface. Moreover, the short interference length broadens the operation bandwidth. Experimentally, a polarization splitter with a lateral dimension of only about 1.6 μm and an operation bandwidth of 50 nm is realized. By designing the double-slit structure in a hybrid strip waveguide, the device dimension can be significant downscaled to about 0.3 × 1.3 μm{sup 2}. Such an ultra-small and broadband polarization splitter may find important applications in the integrated photonic circuits.

Comparison of Thermal Detector Arrays for Off-Axis THz Holography and Real-Time THz Imaging

Directory of Open Access Journals (Sweden)

Erwin Hack

2016-02-01

Full Text Available In terahertz (THz materials science, imaging by scanning prevails when low power THz sources are used. However, the application of array detectors operating with high power THz sources is increasingly reported. We compare the imaging properties of four different array detectors that are able to record THz radiation directly. Two micro-bolometer arrays are designed for infrared imaging in the 8–14 μm wavelength range, but are based on different absorber materials (i vanadium oxide; (ii amorphous silicon; (iii a micro-bolometer array optimized for recording THz radiation based on silicon nitride; and (iv a pyroelectric array detector for THz beam profile measurements. THz wavelengths of 96.5 μm, 118.8 μm, and 393.6 μm from a powerful far infrared laser were used to assess the technical performance in terms of signal to noise ratio, detector response and detectivity. The usefulness of the detectors for beam profiling and digital holography is assessed. Finally, the potential and limitation for real-time digital holography are discussed.

Comparison of Thermal Detector Arrays for Off-Axis THz Holography and Real-Time THz Imaging.

Science.gov (United States)

Hack, Erwin; Valzania, Lorenzo; Gäumann, Gregory; Shalaby, Mostafa; Hauri, Christoph P; Zolliker, Peter

2016-02-06

In terahertz (THz) materials science, imaging by scanning prevails when low power THz sources are used. However, the application of array detectors operating with high power THz sources is increasingly reported. We compare the imaging properties of four different array detectors that are able to record THz radiation directly. Two micro-bolometer arrays are designed for infrared imaging in the 8-14 μm wavelength range, but are based on different absorber materials (i) vanadium oxide; (ii) amorphous silicon; (iii) a micro-bolometer array optimized for recording THz radiation based on silicon nitride; and (iv) a pyroelectric array detector for THz beam profile measurements. THz wavelengths of 96.5 μm, 118.8 μm, and 393.6 μm from a powerful far infrared laser were used to assess the technical performance in terms of signal to noise ratio, detector response and detectivity. The usefulness of the detectors for beam profiling and digital holography is assessed. Finally, the potential and limitation for real-time digital holography are discussed.

Design and simulation of a sub-terahertz folded-waveguide extended interaction oscillator

Science.gov (United States)

Liu, Wenxin; Zhang, Zhaochuan; Zhao, Chao; Guo, Xin; Liao, Suying

2017-06-01

In this paper, an interesting type of a two-section folded wave-guide (TSFW) slow wave structure (SWS) for the development of sub-Terahertz (sub-THz) extended interaction oscillator (EIO) is proposed. In this sub-THz device, the prebunching electron beam is produced by the TSFW SWS, which results in the enhancement of the output power. To verify this concept, the TSFW for sub-THz EIO is developed, which includes the design, simulation, and some fabrications. A small size of electron optics system (EOS), the TSFW SWS for beam-wave interactions, and the output structure are studied with simulations. Through the codes Egun and Superfish, the EOS is designed and optimized. With a help of CST studio and 3D particle-in-cell (PIC) simulation CHIPIC, the characteristics of beam-wave interaction generated by the TSFW are studied. The results of PIC simulation show that the output power is remarkably enhanced by a factor of 3, which exceeds 200 W at the frequency of 108 GHz. Based on the optimum parameters, the TSFW is manufactured with a high speed numerical mill, and the test transmission characteristic |S21| is 13 dB. At last, the output structure with a pill-box window is optimized, fabricated, integrated, and tested, and the result shows that the voltage standing-wave ratio of the window is about 2.2 at an operating frequency of 108 GHz. This design and simulation can provide an effective method to develop high power THz sources.

Optical nonlinearity enhancement with graphene-decorated silicon waveguides

Science.gov (United States)

Ishizawa, Atsushi; Kou, Rai; Goto, Takahiro; Tsuchizawa, Tai; Matsuda, Nobuyuki; Hitachi, Kenichi; Nishikawa, Tadashi; Yamada, Koji; Sogawa, Tetsuomi; Gotoh, Hideki

2017-04-01

Broadband on-chip optical frequency combs (OFCs) are important for expanding the functionality of photonic integrated circuits. Here, we demonstrate a huge local optical nonlinearity enhancement using graphene. A waveguide is decorated with graphene by precisely manipulating graphene’s area and position. Our approach simultaneously achieves both an extremely efficient supercontinuum and ultra-short pulse generation. With our graphene-decorated silicon waveguide (G-SWG), we have achieved enhanced spectral broadening of femtosecond pump pulses, along with an eightfold increase in the output optical intensity at a wavelength approximately 200 nm shorter than that of the pump pulses. We also found that this huge nonlinearity works as a compressor that effectively compresses pulse width from 80 to 15.7 fs. Our results clearly show the potential for our G-SWG to greatly boost the speed and capacity of future communications with lower power consumption, and our method will further decrease the required pump laser power because it can be applied to decorate various kinds of waveguides with various two-dimensional materials.

Field theory of a terahertz staggered double-grating arrays waveguide Cerenkov traveling wave amplifier

Energy Technology Data Exchange (ETDEWEB)

Xie, Wenqiu; He, Fangming [Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Zicheng; Luo, Jirun; Zhao, Ding; Liu, Qinglun [Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-04-15

Based on a rectilinear sheet electron beam propagating through the tunnel of a staggered double-grating arrays waveguide (SDGAW) slow-wave structure (SWS), a three dimensional field theory for describing the modes and the beam-wave interaction is presented, in which the higher order terms inside the grooves are retained. The fields' distribution and the conductivity losses are also calculated utilizing the theoretical model. With the optimized parameters of the SWS and the electron beam, a 1 THz SDGAW Cerenkov traveling wave amplifier may obtain a moderate net gain (the peak gain is 12.7 dB/cm) and an ultra 3 dB wideband (0.19 THz) considering the serious Ohmic losses. The theoretical results have been compared with those calculated by 3D HFSS code and CST STUDIO particle-in-cell simulations.

Semiconductor saturable absorbers for ultrafast THz signals

DEFF Research Database (Denmark)

Hoffmann, Matthias C.; Turchinovich, Dmitry

We demonstrate saturable absorber behavior of n-type semiconductors in the THz frequency range using nonlinear THz spectroscopy. Further, we observe THz pulse shortening and increase of the group refractive index at high field strengths.......We demonstrate saturable absorber behavior of n-type semiconductors in the THz frequency range using nonlinear THz spectroscopy. Further, we observe THz pulse shortening and increase of the group refractive index at high field strengths....

Broadbanding of circularly polarized patch antenna by waveguided magneto-dielectric metamaterial

Directory of Open Access Journals (Sweden)

Xin Mi Yang

2015-12-01

Full Text Available Design of bandwidth-enhanced circularly polarized (CP patch antenna using artificial magneto-dielectric substrate was investigated. The artificial magneto-dielectric material adopted here takes the form of waveguided metamaterial (WG-MTM. In particular, the embedded meander line (EML structure was employed as the building element of the WG-MTM. As verified by the retrieved effective medium parameters, the EML-based waveguided magneto-dielectric metamaterial (WG-MDM exhibits two-dimensionally isotropic magneto-dielectric property with respect to TEM wave excitations applied in two orthogonal directions. A CP patch antenna loaded with the EML-based WG-MDM (WG-MDM antenna has been proposed and its design procedure is described in detail. Simulation results show that the impedance and axial ratio bandwidths of the WG-MDM antenna have increased by 125% and 133%, respectively, compared with those obtained with pure dielectric substrate offering the same patch size. The design of the novel WG-MDM antenna was also validated by measurement results, which show good agreement with their simulated counterparts.

Ultrafast THz Saturable Absorption in Doped Semiconductors

DEFF Research Database (Denmark)

Turchinovich, Dmitry; Hoffmann, Matthias C.

2011-01-01

We demonstrate ultrafast THz saturable absorption in n-doped semiconductors by nonlinear THz time-domain spectroscopy. This effect is caused by the semiconductor conductivity modulation due to electron heating and satellite-valley scattering in strong THz fields.......We demonstrate ultrafast THz saturable absorption in n-doped semiconductors by nonlinear THz time-domain spectroscopy. This effect is caused by the semiconductor conductivity modulation due to electron heating and satellite-valley scattering in strong THz fields....

Efficient power combiner for THz radiation

Energy Technology Data Exchange (ETDEWEB)

Seidfaraji, Hamide, E-mail: hsfaraji@unm.edu; Fuks, Mikhail I.; Christodoulou, Christos; Schamiloglu, Edl [Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM, 87131-0001 (United States)

2016-08-15

Most dangerous explosive materials, both toxic and radioactive, contain nitrogen salts with resonant absorption lines in the frequency range 0.3-10 THz. Therefore, there has been growing interest in remotely detecting such materials by observing the spectrum of reflected signals when the suspicious material is interrogated by THz radiation. Practical portable THz sources available today generate only 20–40 mW output power. This power level is too low to interrogate suspicious material from a safe distance, especially if the material is concealed. Hence, there is a need for sources that can provide greater power in the THz spectrum. Generating and extracting high output power from THz sources is complicated and inefficient. The efficiency of vacuum electronic microwave sources is very low when scaled to the THz range and THz sources based on scaling down semiconductor laser sources have low efficiency as well, resulting in the well known “THz gap.” The reason for such low efficiencies for both source types is material losses in the THz band. In this article an efficient power combiner is described that is based on scaling to higher frequencies a microwave combiner that increases the output power in the THz range of interest in simulation studies. The proposed power combiner not only combines the THz power output from several sources, but can also form a Gaussian wavebeam output. A minimum conversion efficiency of 89% with cophased inputs in a lossy copper power combiner and maximum efficiency of 100% in a Perfect Electric Conductor (PEC)-made power combiner were achieved in simulations. Also, it is shown that the TE{sub 01} output mode is a reasonable option for THz applications due to the fact that conductive loss decreases for this mode as frequency increases.

Efficient power combiner for THz radiation

Directory of Open Access Journals (Sweden)

Hamide Seidfaraji

2016-08-01

Full Text Available Most dangerous explosive materials, both toxic and radioactive, contain nitrogen salts with resonant absorption lines in the frequency range 0.3-10 THz. Therefore, there has been growing interest in remotely detecting such materials by observing the spectrum of reflected signals when the suspicious material is interrogated by THz radiation. Practical portable THz sources available today generate only 20–40 mW output power. This power level is too low to interrogate suspicious material from a safe distance, especially if the material is concealed. Hence, there is a need for sources that can provide greater power in the THz spectrum. Generating and extracting high output power from THz sources is complicated and inefficient. The efficiency of vacuum electronic microwave sources is very low when scaled to the THz range and THz sources based on scaling down semiconductor laser sources have low efficiency as well, resulting in the well known “THz gap.” The reason for such low efficiencies for both source types is material losses in the THz band. In this article an efficient power combiner is described that is based on scaling to higher frequencies a microwave combiner that increases the output power in the THz range of interest in simulation studies. The proposed power combiner not only combines the THz power output from several sources, but can also form a Gaussian wavebeam output. A minimum conversion efficiency of 89% with cophased inputs in a lossy copper power combiner and maximum efficiency of 100% in a Perfect Electric Conductor (PEC-made power combiner were achieved in simulations. Also, it is shown that the TE01 output mode is a reasonable option for THz applications due to the fact that conductive loss decreases for this mode as frequency increases.

Scheme for generating and transporting THz radiation to the X-ray experimental floor at LCLS baseline

Energy Technology Data Exchange (ETDEWEB)

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

2011-08-15

This paper describes a novel scheme for integrating a coherent THz source in the baseline of the LCLS facility. Any method relying on the spent electron beam downstream of the baseline undulator should provide a way of transporting the radiation up to the experimental floor.Herewe propose to use the dump area access maze. In this way the THz output must propagate with limited size at least for one hundred meters in a maze, following many turns, to reach the near experimental hall. The use of a standard, discrete, open beam-waveguide formed by periodic reflectors, that is a mirror guide, would lead to unacceptable size of the system. To avoid these problems, in this paper we propose an alternative approach based on periodically spaced metallic screens with holes. This quasi-optical transmission line is referred to as an iris line. We present complete calculations for the iris line using both analytical and numerical methods, which we find in good agreement. We present a design of a THz edge radiation source based on the use of an iris line. The proposed setup takes almost no cost nor time to be implemented at the LCLS baseline, and can be used at other facilities as well. The edge radiation source is limited in maximally achievable field strength at the sample. An extension based on the use of an undulator in the presence of the iris line, which is feasible at the LCLS energies, is proposed as a possible upgrade of the baseline THz source. (orig)

Scheme for generating and transporting THz radiation to the X-ray experimental floor at LCLS baseline

International Nuclear Information System (INIS)

Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

2011-08-01

This paper describes a novel scheme for integrating a coherent THz source in the baseline of the LCLS facility. Any method relying on the spent electron beam downstream of the baseline undulator should provide a way of transporting the radiation up to the experimental floor.Herewe propose to use the dump area access maze. In this way the THz output must propagate with limited size at least for one hundred meters in a maze, following many turns, to reach the near experimental hall. The use of a standard, discrete, open beam-waveguide formed by periodic reflectors, that is a mirror guide, would lead to unacceptable size of the system. To avoid these problems, in this paper we propose an alternative approach based on periodically spaced metallic screens with holes. This quasi-optical transmission line is referred to as an iris line. We present complete calculations for the iris line using both analytical and numerical methods, which we find in good agreement. We present a design of a THz edge radiation source based on the use of an iris line. The proposed setup takes almost no cost nor time to be implemented at the LCLS baseline, and can be used at other facilities as well. The edge radiation source is limited in maximally achievable field strength at the sample. An extension based on the use of an undulator in the presence of the iris line, which is feasible at the LCLS energies, is proposed as a possible upgrade of the baseline THz source. (orig)

Noise temperature of an NbN hot-electron bolometric mixer at frequencies from 0.7 THz to 5.2 THz

International Nuclear Information System (INIS)

Schubert, J.; Semenov, A.; Gol'tsman, G.; Huebers, H-W.; Voronov, B.; Gershenzon, E.; Schwaab, G.

1999-01-01

We report on noise temperature measurements of an NbN phonon-cooled hot-electron bolometric mixer in the terahertz frequency range. The devices were 3 nm thick films with in-plane dimensions 1.7x0.2μm 2 and 0.9x0.2μm 2 integrated in a complementary logarithmic-spiral antenna. Measurements were performed at seven frequencies ranging from 0.7 THz to 5.2 THz. The measured DSB noise temperatures are 1500 K (0.7 THz), 2200 K (1.4 THz), 2600 K (1.6 THz), 2900 K (2.5 THz), 4000 K (3.1 THz), 5600 K (4.3 THz) and 8800 K (5.2 THz). (author)

Design and fabrication of three-dimensional polymer mode multiplexer based on asymmetric waveguide couplers

Science.gov (United States)

He, Guobing; Gao, Yang; Xu, Yan; Ji, Lanting; Sun, Xiaoqiang; Wang, Xibin; Yi, Yunji; Chen, Changming; Wang, Fei; Zhang, Daming; Wu, Yuanda

2018-05-01

A polymer mode multiplexer based on asymmetric couplers is theoretically designed and experimentally demonstrated. The proposed X-junction coupler is formed by waveguides overlapped with different crossing angles in the vertical direction. A beam propagation method is adopted to optimize the dimensional parameters of the mode multiplexer to convert LP01 mode of two lower waveguides to LP11a and LP21a mode of the upper waveguide. The ultraviolet lithography and wet chemical etching are used in the fabrication process. A conversion ratio over 98% for both LP11a and LP21a mode in the wavelength range from 1530 to 1570 nm are experimentally demonstrated. This mode multiplexer has potential in broadband mode-division multiplexing transmission systems.

Improvement of passive THz camera images

Science.gov (United States)

Kowalski, Marcin; Piszczek, Marek; Palka, Norbert; Szustakowski, Mieczyslaw

2012-10-01

Terahertz technology is one of emerging technologies that has a potential to change our life. There are a lot of attractive applications in fields like security, astronomy, biology and medicine. Until recent years, terahertz (THz) waves were an undiscovered, or most importantly, an unexploited area of electromagnetic spectrum. The reasons of this fact were difficulties in generation and detection of THz waves. Recent advances in hardware technology have started to open up the field to new applications such as THz imaging. The THz waves can penetrate through various materials. However, automated processing of THz images can be challenging. The THz frequency band is specially suited for clothes penetration because this radiation does not point any harmful ionizing effects thus it is safe for human beings. Strong technology development in this band have sparked with few interesting devices. Even if the development of THz cameras is an emerging topic, commercially available passive cameras still offer images of poor quality mainly because of its low resolution and low detectors sensitivity. Therefore, THz image processing is very challenging and urgent topic. Digital THz image processing is a really promising and cost-effective way for demanding security and defense applications. In the article we demonstrate the results of image quality enhancement and image fusion of images captured by a commercially available passive THz camera by means of various combined methods. Our research is focused on dangerous objects detection - guns, knives and bombs hidden under some popular types of clothing.

Wide Angle of Incidence-Insensitive Polarization-Independent THz Metamaterial Absorber for Both TE and TM Mode Based on Plasmon Hybridizations

Directory of Open Access Journals (Sweden)

Xiu Tao Huang

2018-04-01

Full Text Available An ultra-wide-angle THz metamaterial absorber (MA utilizing sixteen-circular-sector (SCR resonator for both transverse electric (TE and transverse magnetic (TM mode is designed and investigated numerically. At normal incidence, the absorptivity of the proposed MA is higher than 93.7% at 9.05 THz for different polarization angles, due to the rotational symmetry structure of the unit cell. Under oblique incidence, the absorptivity can still exceed 90%, even when the incident angle is up to 70° for both TE and TM mode. Especially, the frequency variation in TE mode is less than 0.25% for different incident angles from 0° to 70°. The electric field (Ez distributions are used to explain the absorption mechanism. Numerical simulation results show that the high absorption with wide-angle independence stems from fundamental dipole resonance and gap surface plasmons. The broadband deep-infrared MA is also obtained by stacking three metal-dielectric layers. The designed MA has great potential in bolometric pixel elements, biomedical sensors, THz imaging, and solar cells.

Terahertz broadband polarization converter based on metamaterials

Science.gov (United States)

Li, Yonghua; Zhao, Guozhong

2018-01-01

Based on the metamaterial composed of symmetrical split resonant ring, a broadband reflective terahertz polarization converter is proposed. The numerical simulation shows that it can rotate the polarization direction of linear polarized wave 90° in the range of 0.7-1.8THz and the polarization conversion ratio is over 90%. The reflection coefficient of the two electric field components in the diagonal direction is the same and the phase difference is 180° ,which leads to the cross-polarization rotation.In order to further study the physical mechanism of high polarization conversion, we analyze the surface current distribution of the resonant ring. The polarization converter has potential applications in terahertz wave plate and metamaterial antenna design.

Engineered Quasi-Phase Matching for Nonlinear Quantum Optics in Waveguides

Science.gov (United States)

Van Camp, Mackenzie A.

Entanglement is the hallmark of quantum mechanics. Quantum entanglement--putting two or more identical particles into a non-factorable state--has been leveraged for applications ranging from quantum computation and encryption to high-precision metrology. Entanglement is a practical engineering resource and a tool for sidestepping certain limitations of classical measurement and communication. Engineered nonlinear optical waveguides are an enabling technology for generating entangled photon pairs and manipulating the state of single photons. This dissertation reports on: i) frequency conversion of single photons from the mid-infrared to 843nm as a tool for incorporating quantum memories in quantum networks, ii) the design, fabrication, and test of a prototype broadband source of polarization and frequency entangled photons; and iii) a roadmap for further investigations of this source, including applications in quantum interferometry and high-precision optical metrology. The devices presented herein are quasi-phase-matched lithium niobate waveguides. Lithium niobate is a second-order nonlinear optical material and can mediate optical energy conversion to different wavelengths. This nonlinear effect is the basis of both quantum frequency conversion and entangled photon generation, and is enhanced by i) confining light in waveguides to increase conversion efficiency, and ii) quasi-phase matching, a technique for engineering the second-order nonlinear response by locally altering the direction of a material's polarization vector. Waveguides are formed by diffusing titanium into a lithium niobate wafer. Quasi-phase matching is achieved by electric field poling, with multiple stages of process development and optimization to fabricate the delicate structures necessary for broadband entangled photon generation. The results presented herein update and optimize past fabrication techniques, demonstrate novel optical devices, and propose future avenues for device development

Proposal of a broadband, polarization-insensitive and high-efficiency hot-carrier schottky photodetector integrated with a plasmonic silicon ridge waveguide

International Nuclear Information System (INIS)

Yang, Liu; Kou, Pengfei; Shen, Jianqi; Lee, El Hang; He, Sailing

2015-01-01

We propose a broadband, polarization-insensitive and high-efficiency plasmonic Schottky diode for detection of sub-bandgap photons in the optical communication wavelength range through internal photoemission (IPE). The distinctive features of this design are that it has a gold film covering both the top and the sidewalls of a dielectric silicon ridge waveguide with the Schottky contact formed at the gold–silicon interface and the sidewall coverage of gold can be easily tuned by an insulating layer. An extensive physical model on IPE of hot carriers is presented in detail and is applied to calculate and examine the performance of this detector. In comparison with a diode having only the top gold contact, the polarization sensitivity of the responsivity is greatly minimized in our photodetector with gold film covering both the top and the sidewall. Much higher responsivities for both polarizations are also achieved over a broad wavelength range of 1.2–1.6 μm. Moreover, the Schottky contact is only 4 μm long, leading to a very small dark current. Our design is very promising for practical applications in high-density silicon photonic integration. (paper)

THz wave sensing for petroleum industrial applications

Science.gov (United States)

Al-Douseri, Fatemah M.; Chen, Yunqing; Zhang, X.-C.

2006-04-01

We present the results of terahertz (THz) sensing of gasoline products. The frequency-dependent absorption coefficients, refractive indices, and complex dielectric constants of gasoline and xylene isomers were extracted in the spectral range from 0.5 3.0 THz. The THz spectra of gasoline (#87, #89, #93) and related BTEX (benzene, toluene, ethylbenzene, and xylene) compounds were studied by using Fourier transform infrared spectroscopy (FTIR) in the 1.5 20 THz (50 660 cm-1). The xylene isomers, which are used as antiknock agent in gasoline were determined quantitatively in gasoline in the THz range. Our investigations show the potential of THz technology for the petroleum industrial applications.

THz waves: biological effects, industrial and medical; Les ondes THz: effets biologiques, applications industrielles et medicales

Energy Technology Data Exchange (ETDEWEB)

Coutaz, J.L.; Garet, F. [Universite de Savoie au Bourget du Lac, IMEP-LAHC, UMR CNRS 5130, 73 (France); Le Drean, Y.; Zhadobov, M. [Institut d' Electronique et des Telecommunications de Rennes, 35 (France); Veyret, B. [I.M.S., 33 - Pessac (France); Mounaix, P. [Laboratoire Ondes et Matiere d' Aquitaine, Universite de Bordeaux, 1 UMR 5798, 33 - Talence (France); Caumes, J.P. [ALPhANOV, 33 - Bordeaux (France); Gallot, G. [Ecole Polytechnique, Laboratoire d' Optique et Biosciences, CNRS UMR 7645, INSERM U696, 91 - Palaiseau (France); Gian Piero, Gallerano [ENEA, Frascati (Italy); Mouret, G. [Universite du Littoral Cote d' Opale - ULCO, 59 - Dunkerque (France); Guilpin, J.C. [Direction Generale de l' Aviation Civile, 94 - Bonneuil sur Marne (France)

2011-07-01

Following the debates about body scanners installed in airports for passengers security control, the non-ionizing radiations (NIR) section of the French radiation protection society (SFR) has organized a conference day to take stock of the present day knowledge about the physical aspects and the biological effects of this frequency range as well as about their medical, and industrial applications (both civil and military). This document gathers the slides of the available presentations: 1 - introduction and general considerations about THz waves, the THz physical phenomenon among NIR (J.L. Coutaz); 2 - interaction of millimeter waves with living material: from dosimetry to biological impacts (Y. Le Drean and M. Zhadobov); 3 - Tera-Hertz: standards and recommendations (B. Veyret); 4 - THz spectro-imaging technique: status and perspectives (P. Mounaix); 5 - THz technology: seeing the invisible? (J.P. Caumes); 6 - Tera-Hertz: biological and medical applications (G. Gallot); 7 - Biological applications of THz radiation: a review of events and a glance to the future (G.P. Gallerano); 8 - Industrial and military applications - liquids and solids detection in the THz domain (F. Garet); 9 - THz radiation and its civil and military applications - gas detection and quantifying (G. Mouret); 10 - Body scanners and civil aviation security (J.C. Guilpin, presentation not available). (J.S.)

Ultrafast THz Saturable Absorption in Semiconductors

DEFF Research Database (Denmark)

Turchinovich, Dmitry; Hoffmann, Matthias C.

2011-01-01

We demonstrate THz saturable absorption in n-doped semiconductors GaAs, GaP, and Ge in a nonlinear THz time-domain spectroscopy experiment. Saturable absorption is caused by sample conductivity modulation due to electron heating and satellite valley scattering in the field of a strong THz pulse....

A hybrid waveguide cell for the dielectric properties of reservoir rocks

International Nuclear Information System (INIS)

Siggins, A F; Gunning, J; Josh, M

2011-01-01

A hybrid waveguide cell is described for broad-band measurements of the dielectric properties of hydrocarbon reservoir rocks. The cell is designed to operate in the radio frequency range of 1 MHz to 1 GHz. The waveguide consists of 50 Ω coaxial lines feeding into a central cylindrical section which contains the sample under test. The central portion of the waveguide acts as a circular waveguide and can accept solid core plugs of 38 mm diameter and lengths from 2 to 150 mm. The central section can also be used as a conventional coaxial waveguide when a central electrode with spring-loaded end collets is installed. In the latter mode the test samples are required to be in the form of hollow cylinders. An additional feature of the cell is that the central section is designed to telescope over a limited range of 1–2 mm with the application of an axial load. Effective pressures up to 35 MPa can be applied to the sample under the condition of uniaxial strain. The theoretical basis of the hybrid waveguide cell is discussed together with calibration results. Two reservoir rocks, a Donnybrook sandstone and a kaolin rich clay, are then tested in the cell, both as hollow cylinders in coaxial mode and in the form of solid core plugs. The complex dielectric properties of the two materials over the bandwidth of 1 MHz to 1 GHz are compared with the results of the two testing methods

A hybrid waveguide cell for the dielectric properties of reservoir rocks

Science.gov (United States)

Siggins, A. F.; Gunning, J.; Josh, M.

2011-02-01

A hybrid waveguide cell is described for broad-band measurements of the dielectric properties of hydrocarbon reservoir rocks. The cell is designed to operate in the radio frequency range of 1 MHz to 1 GHz. The waveguide consists of 50 Ω coaxial lines feeding into a central cylindrical section which contains the sample under test. The central portion of the waveguide acts as a circular waveguide and can accept solid core plugs of 38 mm diameter and lengths from 2 to 150 mm. The central section can also be used as a conventional coaxial waveguide when a central electrode with spring-loaded end collets is installed. In the latter mode the test samples are required to be in the form of hollow cylinders. An additional feature of the cell is that the central section is designed to telescope over a limited range of 1-2 mm with the application of an axial load. Effective pressures up to 35 MPa can be applied to the sample under the condition of uniaxial strain. The theoretical basis of the hybrid waveguide cell is discussed together with calibration results. Two reservoir rocks, a Donnybrook sandstone and a kaolin rich clay, are then tested in the cell, both as hollow cylinders in coaxial mode and in the form of solid core plugs. The complex dielectric properties of the two materials over the bandwidth of 1 MHz to 1 GHz are compared with the results of the two testing methods.

Waveguide transition with vacuum window for multiband dynamic nuclear polarization systems

Energy Technology Data Exchange (ETDEWEB)

Rybalko, Oleksandr; Bowen, Sean; Zhurbenko, Vitaliy [Technical University of Denmark, Ørsteds Plads 349, 2800 Kgs. Lyngby (Denmark); Ardenkjær-Larsen, Jan Henrik, E-mail: jhar@elektro.dtu.dk [Technical University of Denmark, Ørsteds Plads 349, 2800 Kgs. Lyngby (Denmark); GE Healthcare, Park Alle 295, Brøndby (Denmark)

2016-05-15

A low loss waveguide transition section and oversized microwave vacuum window covering several frequency bands (94 GHz, 140 GHz, 188 GHz) is presented. The transition is compact and was optimized for multiband Dynamic Nuclear Polarization (DNP) systems in a full-wave simulator. The window is more broadband than commercially available windows, which are usually optimized for single band operation. It is demonstrated that high-density polyethylene with urethane adhesive can be used as a low loss microwave vacuum window in multiband DNP systems. The overall assembly performance and dimensions are found using full-wave simulations. The practical aspects of the window implementation in the waveguide are discussed. To verify the design and simulation results, the window is tested experimentally at the three frequencies of interest.

Phase Locking of a 2.7 THz Quantum Cascade Laser to a Microwave Reference

Science.gov (United States)

Khosropanah, P.; Baryshev, A.; Zhang, W.; Jellema, W.; Hovenier, J. N.; Gao, J. R.; Klapwijk, T. M.; Paveliev, D. G.; Williams, B. S.; Hu, Q.;

Temperature controlled infrared broadband cloaking with the bilayer coatings of semiconductor and superconductor

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaohua [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Physics and Electronics, Yancheng Teachers University, Yancheng 224051 (China); Liu, Youwen, E-mail: ywliu@nuaa.edu.cn [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Feng, Yuncai [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

2015-06-15

Highlights: • We first propose that the cloak is composed of the bilayer of semiconductor and superconductor. • We realize the infrared broadband cloaking based on the scattering cancellation method. • The cloaking frequency can be tuned by external temperature. - Abstract: The infrared broadband tunable cloaking have been proposed and investigated with the bilayer coating materials of semiconductor (n-Ge) and high-temperature superconductor (YBa{sub 2}Cu{sub 3}O{sub 7}), whose cloaking frequency can be controlled by external temperature. The analytical solution is derived based on the scattering cancellation cloaking technique from the Mie scattering theory, and the full-wave numerical simulation is performed by the finite element method. The calculated and simulated results have demonstrated that this invisibility cloak may reduce the total scattering cross section of the composite structure of 90% over a broad frequency band of nearly 20 THz, and the infrared cloaking frequency can be tuned by the external temperature. It can provide a feasible way to design a broadband tunable cloak.

Broadband single-transverse-mode fluorescence sources based on ribs fabricated in pulsed laser deposited Ti: sapphire waveguides

NARCIS (Netherlands)

Grivas, C.; May-Smith, T.C.; Shepherd, D.P.; Eason, R.W.; Pollnau, Markus; Jelinek, M.

2004-01-01

Active rib waveguides with depths and widths varying from 3 to 5 μm and from 9 to 24 μm, respectively, have been structured by $Ar^{+}$-beam etching in pulsed laser deposited Ti:sapphire layers. Losses in the channel structures were essentially at the same levels as the unstructured planar waveguide

Experimental study of a high-current FEM with a broadband microwave system

Energy Technology Data Exchange (ETDEWEB)

Denisov, G.G.; Bratman, V.L.; Ginzburg, N.S. [Institute of Applied Physics, Nizhny Novgorod (Russian Federation)] [and others

1995-12-31

One of the main features of FELs and FEMs is the possibility of fast and wideband tuning of the resonant frequency of active media, which can be provided by changing the particle energy. For a frequency adjustable FEM-oscillator, a broadband microwave system, which is simply combined with an electron-optical FEM system and consists of an oversized waveguide and reflectors based on the microwave beams multiplication effect has been proposed and studied successfully in {open_quotes}cold{close_quotes} measurements. Here, the operating ability of a cavity, that includes some key elements of the broadband microwave system, was tested in the presence of an electron beam. To provide large particle oscillation velocities in a moderate undulator field and the presence of a guide magnetic field, the FEM operating regime of double resonance was chosen. In this regime the cyclotron as well as undulator resonance conditions were satisfied. The FEM-oscillator was investigated experimentally on a high-current accelerator {open_quotes}Sinus-6{close_quotes} that forms an electron beam with particle energy 500keV and pulse duration 25ns. The aperture with a diameter 2.5mm at the center of the anode allows to pass through only the central fraction of the electron beam with a current about 100A and a small spread of longitudinal velocities of the particles. Operating transverse velocity was pumped into the electron beam in the pulse plane undulator of a 2.4cm period. The cavity with a frequency near 45GHz consists of a square waveguide and two reflectors. The broadband up-stream reflector based on the multiplication effect had the power reflectivity coefficient more than 90% in the frequency band 10% for the H{sup 10} wave of the square waveguide with the maximum about 100% at a frequency 45GHz. The down-stream narrow-band Bragg reflector had the power reflection coefficient approximately 80% in the frequency band of 4% near 45GHz for the operating mode.

High-power broad-band tunable microwave oscillator, driven by REB in plasma

Energy Technology Data Exchange (ETDEWEB)

Kuzelev, M V; Loza, O T; Ponomarev, A V; Rukhadze, A A; Strel` kov, P S; Shkvarunets, A G; Ulyanov, D K [General Physics Inst. of Russian Academy of Sciences, Moscow (Russian Federation)

1997-12-31

The radiation spectra of a plasma relativistic broad-band microwave oscillator were measured. A hollow relativistic electron beam (REB) was injected into the plasma waveguide, consisting of annular plasma in a circular metal waveguide. The radiation spectra were measured by means of a calorimeter-spectrometer with a large cross section in the band of 3-39 GHz. The mean frequency was tunable in the band of 20-27 GHz, the spectrum width was 5-25 GHz with a power level of 40-85 MW. Calculations were carried out based on non-linear theory, taking into account electromagnetic noise amplification due to REB injection into the plasma waveguide. According to the theory the radiation regime should change from the single-particle regime to the collective regime when the plasma density and the gap between the annular plasma and REB are increased. Comparison of the experimental results with the non-linear theory explains some peculiarities of the measured spectrum. (author). 4 figs., 2 refs.

Reflective THz and MR imaging of burn wounds: a potential clinical validation of THz contrast mechanisms

Science.gov (United States)

Bajwa, Neha; Nowroozi, Bryan; Sung, Shijun; Garritano, James; Maccabi, Ashkan; Tewari, Priyamvada; Culjat, Martin; Singh, Rahul; Alger, Jeffry; Grundfest, Warren; Taylor, Zachary

2012-10-01

Terahertz (THz) imaging is an expanding area of research in the field of medical imaging due to its high sensitivity to changes in tissue water content. Previously reported in vivo rat studies demonstrate that spatially resolved hydration mapping with THz illumination can be used to rapidly and accurately detect fluid shifts following induction of burns and provide highly resolved spatial and temporal characterization of edematous tissue. THz imagery of partial and full thickness burn wounds acquired by our group correlate well with burn severity and suggest that hydration gradients are responsible for the observed contrast. This research aims to confirm the dominant contrast mechanism of THz burn imaging using a clinically accepted diagnostic method that relies on tissue water content for contrast generation to support the translation of this technology to clinical application. The hydration contrast sensing capabilities of magnetic resonance imaging (MRI), specifically T2 relaxation times and proton density values N(H), are well established and provide measures of mobile water content, lending MRI as a suitable method to validate hydration states of skin burns. This paper presents correlational studies performed with MR imaging of ex vivo porcine skin that confirm tissue hydration as the principal sensing mechanism in THz burn imaging. Insights from this preliminary research will be used to lay the groundwork for future, parallel MRI and THz imaging of in vivo rat models to further substantiate the clinical efficacy of reflective THz imaging in burn wound care.

Characterization of low-frequency acoustic wave propagation through a periodic corrugated waveguide

Science.gov (United States)

Jiang, Changyong; Huang, Lixi

2018-03-01

In this paper, a periodic corrugated waveguide structure is proposed, and its unit-cell is analyzed by the wave finite element method. In low-frequency range, the unit-cell is treated as an equivalent fluid through a homogenization process, and the equivalent acoustic parameters are obtained, which are validated by finite structure simulations and experiments. The proposed structure is shown to add tortuosity to the waveguide, hence higher equivalent fluid density is achieved, while the system elastic modulus remains unchanged. As a result, the equivalent speed of sound is smaller than normal air. The application of such change of speed of sound is demonstrated in the classic quarter-wavelength resonator based on the corrugated waveguide, which gives a lower resonance frequency with the same side branch length. When the waveguide is filled with porous materials, the added tortuosity enhances the broadband, low-frequency sound absorption by increasing the equivalent mass without bringing in excess damping, the latter being partly responsible for the poor performance of usual porous materials in the low-frequency region. Therefore, the proposed structure provides another dimension for the design and optimization of porous sound absorption materials.

Broadband Amplification of Low-Terahertz Signals Using Axis-Encircling Electrons in a Helically Corrugated Interaction Region

Science.gov (United States)

He, W.; Donaldson, C. R.; Zhang, L.; Ronald, K.; Phelps, A. D. R.; Cross, A. W.

2017-11-01

Experimental results are presented of a broadband, high power, gyrotron traveling wave amplifier (gyro-TWA) operating in the (75-110)-GHz frequency band and based on a helically corrugated interaction region. The second harmonic cyclotron mode of a 55-keV, 1.5-A, axis-encircling electron beam is used to resonantly interact with a traveling TE21 -like eigenwave achieving broadband amplification. The gyro-TWA demonstrates a 3-dB gain bandwidth of at least 5.5 GHz in the experimental measurement with 9 GHz predicted for a wideband drive source with a measured unsaturated output power of 3.4 kW and gain of 36-38 dB. The approach may allow a gyro-TWA to operate at 1 THz.

Broadband enhancement of single photon emission and polarization dependent coupling in silicon nitride waveguides.

Science.gov (United States)

Bisschop, Suzanne; Guille, Antoine; Van Thourhout, Dries; Hens, Zeger; Brainis, Edouard

2015-06-01

Single-photon (SP) sources are important for a number of optical quantum information processing applications. We study the possibility to integrate triggered solid-state SP emitters directly on a photonic chip. A major challenge consists in efficiently extracting their emission into a single guided mode. Using 3D finite-difference time-domain simulations, we investigate the SP emission from dipole-like nanometer-sized inclusions embedded into different silicon nitride (SiNx) photonic nanowire waveguide designs. We elucidate the effect of the geometry on the emission lifetime and the polarization of the emitted SP. The results show that highly efficient and polarized SP sources can be realized using suspended SiNx slot-waveguides. Combining this with the well-established CMOS-compatible processing technology, fully integrated and complex optical circuits for quantum optics experiments can be developed.

Design of application specific long period waveguide grating filters using adaptive particle swarm optimization algorithms

International Nuclear Information System (INIS)

Semwal, Girish; Rastogi, Vipul

2014-01-01

We present design optimization of wavelength filters based on long period waveguide gratings (LPWGs) using the adaptive particle swarm optimization (APSO) technique. We demonstrate optimization of the LPWG parameters for single-band, wide-band and dual-band rejection filters for testing the convergence of APSO algorithms. After convergence tests on the algorithms, the optimization technique has been implemented to design more complicated application specific filters such as erbium doped fiber amplifier (EDFA) amplified spontaneous emission (ASE) flattening, erbium doped waveguide amplifier (EDWA) gain flattening and pre-defined broadband rejection filters. The technique is useful for designing and optimizing the parameters of LPWGs to achieve complicated application specific spectra. (paper)

Planar integrated metasurfaces for highly-collimated terahertz quantum cascade lasers

Science.gov (United States)

Liang, Guozhen; Dupont, Emmanuel; Fathololoumi, Saeed; Wasilewski, Zbigniew R.; Ban, Dayan; Liang, Hou Kun; Zhang, Ying; Yu, Siu Fung; Li, Lianhe H.; Davies, Alexander Giles; Linfield, Edmund H.; Liu, Hui Chun; Wang, Qi Jie

2014-01-01

We report planar integration of tapered terahertz (THz) frequency quantum cascade lasers (QCLs) with metasurface waveguides that are designed to be spoof surface plasmon (SSP) out-couplers by introducing periodically arranged SSP scatterers. The resulting surface-emitting THz beam profile is highly collimated with a divergence as narrow as ~4° × 10°, which indicates a good waveguiding property of the metasurface waveguide. In addition, the low background THz power implies a high coupling efficiency for the THz radiation from the laser cavity to the metasurface structure. Furthermore, since all the structures are in-plane, this scheme provides a promising platform where well-established surface plasmon/metasurface techniques can be employed to engineer the emitted beam of THz QCLs controllably and flexibly. More importantly, an integrated active THz photonic circuit for sensing and communication applications could be constructed by incorporating other optoelectronic devices such as Schottky diode THz mixers, and graphene modulators and photodetectors. PMID:25403796

Octave-spanning supercontinuum generation at telecommunications wavelengths in a precisely dispersion- and length-controlled silicon-wire waveguide with a double taper structure

Science.gov (United States)

Ishizawa, Atsushi; Goto, Takahiro; Kou, Rai; Tsuchizawa, Tai; Matsuda, Nobuyuki; Hitachi, Kenichi; Nishikawa, Tadashi; Yamada, Koji; Sogawa, Tetsuomi; Gotoh, Hideki

2017-07-01

We demonstrate on-chip octave-spanning supercontinuum (SC) generation with a Si-wire waveguide (SWG). We precisely controlled the SWG width so that the group velocity becomes flat over a wide wavelength range. By adjusting the SWG length, we could reduce the optical losses due to two-photon absorption and pulse propagation. In addition, for efficient coupling between the laser pulse and waveguide, we fabricated a two-step inverse taper at both ends of the SWG. Using a 600-nm-wide SWG, we were able to generate a broadband SC spectrum at wavelengths from 1060 to 2200 nm at a -40 dB level with only 50-pJ laser energy from an Er-doped fiber laser oscillator. We found that we can generate an on-chip broadband SC spectrum with an SWG with a length even as small as 1.7 mm.

THz waves: biological effects, industrial and medical

International Nuclear Information System (INIS)

Coutaz, J.L.; Garet, F.; Le Drean, Y.; Zhadobov, M.; Veyret, B.; Mounaix, P.; Caumes, J.P.; Gallot, G.; Gian Piero, Gallerano; Mouret, G.; Guilpin, J.C.

2011-01-01

Following the debates about body scanners installed in airports for passengers security control, the non-ionizing radiations (NIR) section of the French radiation protection society (SFR) has organized a conference day to take stock of the present day knowledge about the physical aspects and the biological effects of this frequency range as well as about their medical, and industrial applications (both civil and military). This document gathers the slides of the available presentations: 1 - introduction and general considerations about THz waves, the THz physical phenomenon among NIR (J.L. Coutaz); 2 - interaction of millimeter waves with living material: from dosimetry to biological impacts (Y. Le Drean and M. Zhadobov); 3 - Tera-Hertz: standards and recommendations (B. Veyret); 4 - THz spectro-imaging technique: status and perspectives (P. Mounaix); 5 - THz technology: seeing the invisible? (J.P. Caumes); 6 - Tera-Hertz: biological and medical applications (G. Gallot); 7 - Biological applications of THz radiation: a review of events and a glance to the future (G.P. Gallerano); 8 - Industrial and military applications - liquids and solids detection in the THz domain (F. Garet); 9 - THz radiation and its civil and military applications - gas detection and quantifying (G. Mouret); 10 - Body scanners and civil aviation security (J.C. Guilpin, presentation not available). (J.S.)

THz Electro-absorption Effect in Quantum Dots

DEFF Research Database (Denmark)

Turchinovich, Dmitry; Monozon, Boris S.; Livshits, Daniil A.

2011-01-01

In a THz pump - optical probe experiment we demonstrate an instantaneous electro-absorption effect in InGaAs/GaAs quantum dots, induced by the electric field of a single-cycle THz pulse with 3 THz bandwidth and with free-space peak electric field reaching 220 kV/cm. The transient modulation of QD...

Generation, transmission, and detection of terahertz photons on an electrically driven single chip

Energy Technology Data Exchange (ETDEWEB)

Ikushima, Kenji; Ito, Atsushi; Okano, Shun [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588 (Japan)

2014-02-03

We demonstrate single photon counting of terahertz (THz) waves transmitted from a local THz point source through a coplanar two-wire waveguide on a GaAs/AlGaAs single heterostructure crystal. In the electrically driven all-in-one chip, quantum Hall edge transport is used to achieve a noiseless injection current for a monochromatic point source of THz fields. The local THz fields are coupled to a coplanar two-wire metal waveguide and transmitted over a macroscopic scale greater than the wavelength (38 μm in GaAs). THz waves propagating on the waveguide are counted as individual photons by a quantum-dot single-electron transistor on the same chip. Photon counting on integrated high-frequency circuits will open the possibilities for on-chip quantum optical experiments.

Bridging the gap between the THz and IR frequency regime

DEFF Research Database (Denmark)

Kaltenecker, Korbinian J.; Zhou, Binbin; Stenger, Nicolas

2017-01-01

THz air photonics allow for the generation and detection of single-cycle sub-40 fs THz transients, which we use in a THz time-domain spectrometer to investigate the transmission properties of molecular crystalline materials in the ultrabroadband frequency window from 0.3 THz to more than 40 THz. ...

Broadband electron spin resonance from 500 MHz to 40 GHz using superconducting coplanar waveguides

Science.gov (United States)

Clauss, Conrad; Bothner, Daniel; Koelle, Dieter; Kleiner, Reinhold; Bogani, Lapo; Scheffler, Marc; Dressel, Martin

2013-04-01

We present non-conventional electron spin resonance (ESR) experiments based on microfabricated superconducting Nb thin film waveguides. A very broad frequency range, from 0.5 to 40 GHz, becomes accessible at low temperatures down to 1.6 K and in magnetic fields up to 1.4 T. This allows for an accurate inspection of the ESR absorption position in the frequency domain, in contrast to the more common observation as a function of magnetic field. We demonstrate the applicability of frequency-swept ESR on Cr3+ atoms in ruby as well as on organic radicals of the nitronyl-nitroxide family. Measurements between 1.6 and 30 K reveal a small frequency shift of the ESR and a resonance broadening below the critical temperature of Nb, which we both attribute to a modification of the magnetic field configuration due to the appearance of shielding supercurrents in the waveguide.

Broadband and Efficient Dual-Pump Four-Wave Mixing in AlGaAs-On-Insulator Nano-Waveguide

DEFF Research Database (Denmark)

Da Ros, Francesco; Pu, Minhao; Ottaviano, Luisa

2016-01-01

We characterize dual-pump four-wave-mixing in AlGaAs-on-insulator nano-waveguides and demonstrate an output conversion efficiency as high as -8.5 dB at 155-mW pump power. The idler optical signal-to-noise ratio is above 25 dB over a 26-nm bandwidth.......We characterize dual-pump four-wave-mixing in AlGaAs-on-insulator nano-waveguides and demonstrate an output conversion efficiency as high as -8.5 dB at 155-mW pump power. The idler optical signal-to-noise ratio is above 25 dB over a 26-nm bandwidth....

Asymmetric quantum well broadband thyristor laser

Science.gov (United States)

Liu, Zhen; Wang, Jiaqi; Yu, Hongyan; Zhou, Xuliang; Chen, Weixi; Li, Zhaosong; Wang, Wei; Ding, Ying; Pan, Jiaoqing

2017-11-01

A broadband thyristor laser based on InGaAs/GaAs asymmetric quantum well (AQW) is fabricated by metal organic chemical vapor deposition (MOCVD). The 3-μm-wide Fabry-Perot (FP) ridge-waveguide laser shows an S-shape I-V characteristic and exhibits a flat-topped broadband optical spectrum coverage of ~27 nm (Δ-10 dB) at a center wavelength of ~1090 nm with a total output power of 137 mW under pulsed operation. The AQW structure was carefully designed to establish multiple energy states within, in order to broaden the gain spectrum. An obvious blue shift emission, which is not generally acquired in QW laser diodes, is observed in the broadening process of the optical spectrum as the injection current increases. This blue shift spectrum broadening is considered to result from the prominent band-filling effect enhanced by the multiple energy states of the AQW structure, as well as the optical feedback effect contributed by the thyristor laser structure. Project supported by the National Natural Science Foundation of China (Nos. 61604144, 61504137). Zhen Liu and Jiaqi Wang contributed equally to this work.

THz Imaging by a Wide-band Compact FEL

CERN Document Server

Uk Jeong Young; Cheol Lee Byung; Hee-Park, S

2004-01-01

We have developed a laboratory-scale users facility with a compact THz FEL. The FEL operates in the wide wavelength range of 100–1200 μm, which corresponds to 0.3-3 THz. THz radiation from the FEL shows well collimated Gaussian spatial distribution and narrow spectral width of 0.3 μm, which is Fourier transform limited by the estimated pulse duration of 20 ps. The main application of the FEL is THz imaging for bio-medical researches. We are developing THz imaging techniques by 2-D scanning, single pulse capturing with the electro-optic method, and 3-D holography. High power, coherent, and pulsed feature of the FEL radiation is expected to show much better performance in advanced THz imaging of 3-D tomography by comparing with incoherent and weak THz sources. By controlling the optical delay between reference beam and scattered light from an object, we can get its 3-D tomography by the holograms. The coherent and pulse length of the FEL beam is measured to be 3-6 mm. In this paper we will show a...

Tunable plasmon-induced absorption effects in a graphene-based waveguide coupled with graphene ring resonators

Science.gov (United States)

Huang, Pei-Nian; Xia, Sheng-Xuan; Fu, Guang-Lai; Liang, Mei-Zhen; Qin, Meng; Zhai, Xiang; Wang, Ling-Ling

2018-03-01

In this paper, we propose a structure composed of two graphene waveguides and dual coupled graphene ring resonators (GRRs) to achieve a plasmon-induced absorption (PIA) effect. A three-level plasmonic system and a temporal coupled mode theory (CMT) are utilized to verify the simulation results. Moreover, a double-window-PIA effect can be conveniently attained by introducing another GRR with proper parameters to meet more specific acquirement in optical modulation process. The pronounced PIA resonances can be tuned in a number of ways, such as by adjusting the coupling distance between the GRRs and the couplings between the GRR and the waveguide, and tuning the radius and the Fermi energy of the GRRs. Besides, the produced PIA effect shows a high group delay up to - 1 . 87 ps, exhibiting a particularly prominent fast-light feature. Our results have potential applications in the realization of THz-integrated spectral control and graphene plasmonic devices such as sensors, filters, ultra-fast optical switches and so on.

Tunable, Room Temperature THZ Emitters Based on Nonlinear Photonics

Science.gov (United States)

Sinha, Raju

The Terahertz (1012 Hz) region of the electromagnetic spectrum covers the frequency range from roughly 300 GHz to 10 THz, which is in between the microwave and infrared regimes. The increasing interest in the development of ultra-compact, tunable room temperature Terahertz (THz) emitters with wide-range tunability has stimulated in-depth studies of different mechanisms of THz generation in the past decade due to its various potential applications such as biomedical diagnosis, security screening, chemical identification, life sciences and very high speed wireless communication. Despite the tremendous research and development efforts, all the available state-of-the-art THz emitters suffer from either being large, complex and costly, or operating at low temperatures, lacking tunability, having a very short spectral range and a low output power. Hence, the major objective of this research was to develop simple, inexpensive, compact, room temperature THz sources with wide-range tunability. We investigated THz radiation in a hybrid optical and THz micro-ring resonators system. For the first time, we were able to satisfy the DFG phase matching condition for the above-mentioned THz range in one single device geometry by employing a modal phase matching technique and using two separately designed resonators capable of oscillating at input optical waves and generated THz waves. In chapter 6, we proposed a novel plasmonic antenna geometry – the dimer rod-tapered antenna (DRTA), where we created a hot-spot in the nanogap between the dimer arms with a very large intensity enhancement of 4.1x105 at optical resonant wavelength. Then, we investigated DFG operation in the antenna geometry by incorporating a nonlinear nanodot in the hot-spot of the antenna and achieved continuously tunable enhanced THz radiation across 0.5-10 THz range. In chapter 8, we designed a multi-metallic resonators providing an ultrasharp toroidal response at THz frequency, then fabricated and

Majolica imaging with THz waves: preliminary results

Science.gov (United States)

Catapano, Ilaria; Affinito, Antonio; Guerriero, Luigi; Bisceglia, Bruno; Soldovieri, Francesco

2016-05-01

Recent advancements performed in the development of stable and flexible devices working at TeraHertz (THz) frequencies have opened the way at considering this technology as a very interesting noninvasive diagnostic tool in cultural heritage. In this frame, the paper aims at assessing the ability of THz imaging to gather information about preservation state and constructive modalities of majolica artworks. In particular, THz surveys have been carried out on two majolica tiles dated back to the nineteenth century and realized as building cladding at Naples (Italy). The analysis has been performed by means of the Zomega fiber-coupled THz time-domain system. This analysis corroborates the ability of THz to reconstruct irregularities of majolica tile topography, to characterize pigment and glaze losses, and to detect and localize glaze and pigment layer as well as the glaze-clay body interface.

Design of a 300 GHZ broadband coupler and RF-structure

International Nuclear Information System (INIS)

Krawczyk, F.L.; Carlsten, B.E.; Earley, L.M.; Sigler, F.E.; Potter, J.M.; Schulze, M.E.

2004-01-01

Recent LANL activities in millimeter wave structures focus on 95 and 300 GHz structures. They aim at power generation from low power (100W-2kW) with a round electron beam (120kV, 0.1-1.0 A) to high power (2-100 kW) with a sheet beam structure (120 kV, 20 A). Applications cover basic research, radar and secure communications and remote sensing of biological and chemical agents. In this presentation the design of a 300 GHz RF-structure with a broadband (> 6% bandwidth) power coupler is presented. The choice of two input/output waveguides, a special coupling region and the structure parameters are presented. As a benchmark also a scaled up version at 10 GHz was designed and measured. These results will also be presented. We are investigating planar micro-fabricated traveling-wave tube amplifiers as sources for the generation of millimeter waves from 95 to 300 GHz. While for low energy applications narrow structures with pencil beams are proposed, for high energy operation flat, thin sheet beams are required. For the latter vane-loaded rectangular waveguides that operate in a slow-wave mode matched to the velocity of the electron beam are especially well suited. The 300 GHz effort initially is limited to narrow structures for pencil beams. The main emphasis for this work are the study of fabrication issues and the understanding of features that allow a broadband operation (5-10% bandwidth).

Empty substrate integrated waveguide technology for E plane high-frequency and high-performance circuits

Science.gov (United States)

Belenguer, Angel; Cano, Juan Luis; Esteban, Héctor; Artal, Eduardo; Boria, Vicente E.

2017-01-01

Substrate integrated circuits (SIC) have attracted much attention in the last years because of their great potential of low cost, easy manufacturing, integration in a circuit board, and higher-quality factor than planar circuits. A first suite of SIC where the waves propagate through dielectric have been first developed, based on the well-known substrate integrated waveguide (SIW) and related technological implementations. One step further has been made with a new suite of empty substrate integrated waveguides, where the waves propagate through air, thus reducing the associated losses. This is the case of the empty substrate integrated waveguide (ESIW) or the air-filled substrate integrated waveguide (air-filled SIW). However, all these SIC are H plane structures, so classical H plane solutions in rectangular waveguides have already been mapped to most of these new SIC. In this paper a novel E plane empty substrate integrated waveguide (ESIW-E) is presented. This structure allows to easily map classical E plane solutions in rectangular waveguide to this new substrate integrated solution. It is similar to the ESIW, although more layers are needed to build the structure. A wideband transition (covering the frequency range between 33 GHz and 50 GHz) from microstrip to ESIW-E is designed and manufactured. Measurements are successfully compared with simulation, proving the validity of this new SIC. A broadband high-frequency phase shifter (for operation from 35 GHz to 47 GHz) is successfully implemented in ESIW-E, thus proving the good performance of this new SIC in a practical application.

Precision and broadband frequency swept laser source based on high-order modulation-sideband injection-locking.

Science.gov (United States)

Wei, Fang; Lu, Bin; Wang, Jian; Xu, Dan; Pan, Zhengqing; Chen, Dijun; Cai, Haiwen; Qu, Ronghui

2015-02-23

A precision and broadband laser frequency swept technique is experimentally demonstrated. Using synchronous current compensation, a slave diode laser is dynamically injection-locked to a specific high-order modulation-sideband of a narrow-linewidth master laser modulated by an electro-optic modulator (EOM), whose driven radio frequency (RF) signal can be agilely, precisely controlled by a frequency synthesizer, and the high-order modulation-sideband enables multiplied sweep range and tuning rate. By using 5th order sideband injection-locking, the original tuning range of 3 GHz and tuning rate of 0.5 THz/s is multiplied by 5 times to 15 GHz and 2.5 THz/s respectively. The slave laser has a 3 dB-linewidth of 2.5 kHz which is the same to the master laser. The settling time response of a 10 MHz frequency switching is 2.5 µs. By using higher-order modulation-sideband and optimized experiment parameters, an extended sweep range and rate could be expected.

An on-chip polarization splitter based on the radiation loss in the bending hybrid plasmonic waveguide structure

Science.gov (United States)

Sun, Chengwei; Rong, Kexiu; Gan, Fengyuan; Chu, Saisai; Gong, Qihuang; Chen, Jianjun

2017-09-01

Polarization beam splitters (PBSs) are one of the key components in the integrated photonic circuits. To increase the integration density, various complex hybrid plasmonic structures have been numerically designed to shrink the footprints of the PBSs. Here, to decrease the complexity of the small hybrid structures and the difficulty of the hybrid micro-nano fabrications, the radiation losses are utilized to experimentally demonstrate an ultra-small, broadband, and efficient PBS in a simple bending hybrid plasmonic waveguide structure. The hybrid plasmonic waveguide comprising a dielectric strip on the metal surface supports both the transverse-magnetic (TM) and transverse-electric (TE) waveguide modes. Because of the different field confinements, the TE waveguide mode has larger radiation loss than the TM waveguide mode in the bending hybrid strip waveguide. Based on the different radiation losses, the two incident waveguide modes of orthogonal polarization states are efficiently split in the proposed structure with a footprint of only about 2.2 × 2.2 μm2 on chips. Since there is no resonance or interference in the splitting process, the operation bandwidth is as broad as Δλ = 70 nm. Moreover, the utilization of the strongly confined waveguide modes instead of the bulk free-space light (with the spot size of at least a few wavelengths) as the incident source considerably increases the coupling efficiency, resulting in a low insertion loss of <3 dB.

Characterization of a Wavelength Converter for 256-QAM Signals Based on an AlGaAs-On-Insulator Nano-waveguide

DEFF Research Database (Denmark)

Da Ros, Francesco; Yankov, Metodi Plamenov; Porto da Silva, Edson

2016-01-01

High efficiency and broadband wavelength conversion in a 9-mm AlGaAs-On-Insulator waveguide is shown to provide high-quality (OSNR > 30 dB) idler generation over a 28-nm bandwidth enabling error-free conversion of 10-GBd 256-QAM with OSNR penalty below 2.5 dB....

Novel O-band tunable fiber laser using an array waveguide grating

International Nuclear Information System (INIS)

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

2010-01-01

A novel tunable fibre laser (TFL) operating in the ordinary band (O-band) of 1310 nm is proposed and demonstrated. The proposed TFL is developed using a 1×16 arrayed waveguide grating (AWG) as a slicing mechanism for the broadband amplified spontaneous emission (ASE) source and an optical channel selector (OCS) to provide the tunability. A semiconductor optical amplifier (SOA) with a centre wavelength of 1310 nm serves as the compact gain medium for the TFL and also as a broadband ASE source. The TFL has a tuning range of 1301.26 nm to 1311.18 nm with 9.92 nm span and a channel spacing of 0.7 nm. The measured output power is about –4 and –8 dBm and with a side node suppression ratio (SMSR) of 29 to 33 dB

Broadband and efficient dual-pump four-wave-mixing in AlGaAs-on-insulator nano-waveguides

DEFF Research Database (Denmark)

Da Ros, Francesco; Pu, Minhao; Ottaviano, Luisa

2016-01-01

We characterize dual-pump four-wave-mixing in AlGaAs-on-insulator nano-waveguides and demonstrate an output conversion efficiency as high as −8.5 dB at 155-mW pump power. The idler optical signal-to-noise ratio is above 25 dB over a 26-nm bandwidth.......We characterize dual-pump four-wave-mixing in AlGaAs-on-insulator nano-waveguides and demonstrate an output conversion efficiency as high as −8.5 dB at 155-mW pump power. The idler optical signal-to-noise ratio is above 25 dB over a 26-nm bandwidth....

THz and Security Applications

CERN Document Server

Sizov, Fedir; Detectors, Sources and Associated Electronics for THz Applications

2014-01-01

These proceedings comprise invited papers from highly experienced researchers in THz technology and security applications. THz detection of explosives represents one of the most appealing technologies to have recently emerged in dealing with terrorist attacks encountered by civil security and military forces throughout the world. Discussed are the most advanced technologies and developments, the various points of operational strength and weaknesses as well as are suggestions and predictions the best technological solutions to  overcome current operational limits.  The current status of various levels of cooling in THz detectors, sources and associated electronics are also addressed. The goal was to provide a clear view on the current technologies available and the required advances needed in order to achieve more efficient systems. This goal was outlined in part by establishing the baseline of current uncertainty estimations in physics-based modelling and the identification of key areas which require additi...

New developments in THz-time domain spectroscopy involving ML-VECSELs

Science.gov (United States)

Apostolopoulos, Vasilis; Tropper, Anne C.; Keenlyside, Benjamin; Chen-Sverre, Theo; Woods, Jonathan R. C.

2018-02-01

The THz time domain spectrometer (THz-TDS) has revolutionized the adoption of THz science in fields such as medicine, material characterization, pharmaceutical research and biology among others. Traditionally a THz-TDS was based on a titanium sapphire laser, while most of the commercially sold spectrometers today adopt fiber lasers. Vertical External Cavity Surface emitting lasers or VECSELs have potential to be the future laser of choice for the implementation of THz spectrometers, as they are small, low-cost, low noise and high repetition rate. Here I will outline the progress in our laboratory and the general community concerning VECSEL-THz technology and I will account the problems that have to be solved for the VECSEL-THz technology to succeed.

Extremely frequency-widened terahertz wave generation using Cherenkov-type radiation.

Science.gov (United States)

Suizu, Koji; Koketsu, Kaoru; Shibuya, Takayuki; Tsutsui, Toshihiro; Akiba, Takuya; Kawase, Kodo

2009-04-13

Terahertz (THz) wave generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-wave source. Such a development of efficient and wide tunable THz-wave source depends on discovery of novel brilliant nonlinear crystal. Important factors of a nonlinear crystal for THz-wave generation are, 1. High nonlinearity and 2. Good transparency at THz frequency region. Unfortunately, many nonlinear crystals have strong absorption at THz frequency region. The fact limits efficient and wide tunable THz-wave generation. Here, we show that Cherenkov radiation with waveguide structure is an effective strategy for achieving efficient and extremely wide tunable THz-wave source. We fabricated MgO-doped lithium niobate slab waveguide with 3.8 microm of thickness and demonstrated difference frequency generation of THz-wave generation with Cherenkov phase matching. Extremely frequency-widened THz-wave generation, from 0.1 to 7.2 THz, without no structural dips successfully obtained. The tuning frequency range of waveguided Cherenkov radiation source was extremely widened compare to that of injection seeded-Terahertz Parametric Generator. The tuning range obtained in this work for THz-wave generation using lithium niobate crystal was the widest value in our knowledge. The highest THz-wave energy obtained was about 3.2 pJ, and the energy conversion efficiency was about 10(-5) %. The method can be easily applied for many conventional nonlinear crystals, results in realizing simple, reasonable, compact, high efficient and ultra broad band THz-wave sources.

Ultrafast nonlinear carrier dynamics in doped semiconductors in high THz fields

DEFF Research Database (Denmark)

Hoffmann, Matthias C.; Turchinovich, Dmitry

2011-01-01

THz frequency saturable absorption and intervalley carrier scattering in n-type semiconductors were observed using intensity-dependent transmission experiments as well as THz-pump—THz probe spectroscopy with ultrabroadband probe pulses.......THz frequency saturable absorption and intervalley carrier scattering in n-type semiconductors were observed using intensity-dependent transmission experiments as well as THz-pump—THz probe spectroscopy with ultrabroadband probe pulses....

A THz Tomography System for Arbitrarily Shaped Samples

Science.gov (United States)

Stübling, E.; Bauckhage, Y.; Jelli, E.; Fischer, B.; Globisch, B.; Schell, M.; Heinrich, A.; Balzer, J. C.; Koch, M.

2017-10-01

We combine a THz time-domain spectroscopy system with a robotic arm. With this scheme, the THz emitter and receiver can be positioned perpendicular and at defined distance to the sample surface. Our system allows the acquisition of reflection THz tomographic images of samples with an arbitrarily shaped surface.

Invited Article: An active terahertz polarization converter employing vanadium dioxide and a metal wire grating in total internal reflection geometry

Science.gov (United States)

Liu, Xudong; Chen, Xuequan; Parrott, Edward P. J.; Han, Chunrui; Humbert, Georges; Crunteanu, Aurelian; Pickwell-MacPherson, Emma

2018-05-01

Active broadband terahertz (THz) polarization manipulation devices are challenging to realize, but also of great demand in broadband terahertz systems. Vanadium dioxide (VO2) shows a promising phase transition for active control of THz waves and provides broadband polarization characteristics when integrated within grating-type structures. We creatively combine a VO2-based grating structure with a total internal reflection (TIR) geometry providing a novel interaction mechanism between the electromagnetic waves and the device, to realize a powerful active broadband THz polarization-controlling device. The device is based on a Si-substrate coated with a VO2 layer and a metal grating structure on top, attached to a prism for generating the TIR condition on the Si-VO2-grating interface. The grating is connected to electrodes for electrically switching the VO2 between its insulating and conducting phases. By properly selecting the incident angle of the THz waves, the grating direction, and the incident polarization state, we first achieved a broadband intensity modulator under a fused silica prism with an average modulation depth of 99.75% in the 0.2-1.1 THz region. Additionally, we realized an active ultra-broadband quarter-wave converter under a Si prism that can be switched between a 45° linear rotator and a quarter wave converter in the 0.8-1.5 THz region. This is the first demonstration of an active quarter-wave converter with ultra-broad bandwidth performance. Our work shows a highly flexible and multifunctional polarization-controlling device for broadband THz applications.

Substrate integrated waveguide (SIW 3 dB coupler for K-Band applications

Directory of Open Access Journals (Sweden)

Khalid Nurehansafwanah

2017-01-01

Full Text Available This paper presented a designed coupler by using Rogers RO4003C with thickness (h 0.508 mm and relative permittivity (εr 3.55. The four port network coupler operates in K-band (18-27 GHz and design by using substrate integrated waveguide (SIW method. The reflection coefficient and isolation coefficient of propose Substrate Integrated Waveguide (SIW coupler is below than -10 dB. Meanwhile the coupler requirements are phase shift 90° between coupled port and output. SIW are high performance broadband interconnects with excellent immunity to electromagnetic interference and suitable for use in microwave and communication electronics, as well as increase bandwidth systems. The designs of coupler are investigated using CST Microwave Studio simulation tool. This proposed couplers are varied from parameters that cover the frequency range (21 -24 GHz and better performance of scattering (S-parameter.

Broadband modulation of terahertz waves through electrically driven hybrid bowtie antenna-VO2 devices.

Science.gov (United States)

Han, Chunrui; Parrott, Edward P J; Humbert, Georges; Crunteanu, Aurelian; Pickwell-MacPherson, Emma

2017-10-05

Broadband modulation of terahertz (THz) light is experimentally realized through the electrically driven metal-insulator phase transition of vanadium dioxide (VO 2 ) in hybrid metal antenna-VO 2 devices. The devices consist of VO 2 active layers and bowtie antenna arrays, such that the electrically driven phase transition can be realized by applying an external voltage between adjacent metal wires extended to a large area array. The modulation depth of the terahertz light can be initially enhanced by the metal wires on top of VO 2 and then improved through the addition of specific bowties in between the wires. As a result, a terahertz wave with a large beam size (~10 mm) can be modulated within the measurable spectral range (0.3-2.5 THz) with a frequency independent modulation depth as high as 0.9, and the minimum amplitude transmission down to 0.06. Moreover, the electrical switch on/off phase transition depends very much on the size of the VO 2 area, indicating that smaller VO 2 regions lead to higher modulation speeds and lower phase transition voltages. With the capabilities in actively tuning the beam size, modulation depth, modulation bandwidth as well as the modulation speed of THz waves, our study paves the way in implementing multifunctional components for terahertz applications.

Self-phase modulation of a single-cycle THz pulse

DEFF Research Database (Denmark)

Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, M. C.

2013-01-01

We demonstrate self-phase modulation (SPM) of a single-cycle THz pulse in a semiconductor, using bulk n-GaAs as a model system. The SPM arises from the heating of free electrons in the electric field of the THz pulse. Electron heating leads to an ultrafast reduction of the plasma frequency, which...... results in a strong modification of the THz-range dielectric function of the material. THz SPM is observed directly in the time domain as a characteristic reshaping of single-cycle THz pulse. In the frequency domain, it corresponds to a strong frequency-dependent refractive index nonlinearity of n...

THz Time-Domain Spectroscopy of Interstellar Ice Analogs

Science.gov (United States)

Ioppolo, Sergio; McGuire, Brett A.; de Vries, Xander; Carroll, Brandon; Allodi, Marco; Blake, Geoffrey

2015-08-01

The unambiguous identification of nearly 200 molecular species in different astronomical environments proves that our cosmos is a ‘Molecular Universe’. The cumulative outcome of recent observations, laboratory studies, and astrochemical models indicates that there is a strong interplay between the gas and the solid phase throughout the process of forming molecules in space. Observations of interstellar ices are generally limited to lines-of-sight along which infrared absorption spectroscopy is possible. Therefore, the identification of more complex prebiotic molecules in the mid-IR is difficult because of their low expected interstellar abundances and the overlap of their absorption features with those from the more abundant species. In the THz region, telescopes can detect Interstellar ices in emission or absorption against dust continuum. Thus, THz searches do not require a background point source. Moreover, since THz spectra are the fingerprint of inter- and intramolecular forces, complex species can present unique modes that do not overlap with those from simpler, more abundant molecules. THz modes are also sensitive to temperature and phase changes in the ice. Therefore, spectroscopy at THz frequencies has the potential to better characterize the physics and chemistry of the ISM. Currently, the Herschel Space Telescope, SOFIA, and ALMA databases contain a vast amount of new THz spectral data that require THz laboratory spectra for interpretation. The latter, however, are largely lacking. We have recently constructed a new THz time-domain spectroscopy system operating in the range between 0.3 - 7.5 THz. This work focuses on the laboratory investigation of the composition and structure of the most abundant interstellar ice analogs compared to some more complex species. Different temperatures, mixing ratios, and matrix isolation experiments will be shown. The ultimate goal of this research is to provide the scientific community with an extensive THz ice

Propagation characteristic of THz wave in camouflage net material

Science.gov (United States)

Dong, Hailong; Wang, Jiachun; Chen, Zongsheng; Lin, Zhidan; Zhao, Dapeng; Liu, Ruihuang

2017-10-01

Terahertz (THz) radar system, with excellent potentials such as high-resolution and strong penetration capability, is promising in the field of anti-camouflage. Camouflage net is processed by cutting the camouflage net material, which is fabricated on pre-processing substrate by depositing coatings with camouflage abilities in different bands, such as visible, infrared and radar. In this paper, we concentrate on the propagation characteristic of THz wave in camouflage net material. Firstly, function and structure of camouflage net were analyzed. Then the advantage and appliance of terahertz time-domain spectroscopy (THz-TDS) was introduced. And the relevant experiments were conducted by utilizing THz-TDS. The results obtained indicate that THz wave has better penetration capacity in camouflage net material, which demonstrates the feasibility of using THz radar to detect those targets covered with camouflage net.

Photonic-assisted ultrafast THz wireless access

DEFF Research Database (Denmark)

Yu, Xianbin; Chen, Ying; Galili, Michael

THz technology has been considered feasible for ultrafast wireless data communi- cation, to meet the increasing demand on next-generation fast wireless access, e.g., huge data file transferring and fast mobile data stream access. This talk reviews recent progress in high-speed THz wireless...

Nonlinear THz spectroscopy on n-type GaAs

Energy Technology Data Exchange (ETDEWEB)

Gaal, Peter

2008-06-23

In this thesis, the ultrafast dynamics of conduction band electrons in semiconductors are investigated by nonlinear terahertz (THz) spectroscopy. In particular, n-doped gallium arsenide samples with doping concentrations in the range of 10{sup 16} cm{sup -3} to 10{sup 17} cm{sup -3} are studied. A novel source for the generation of intense THz radiation is developed which yields single-cycle THz transients with field amplitudes of more then 400 kV/cm. The THz source uses ultrashort optical laser pulses provided by a Ti:sapphire oscillator. In addition, a two-color THz-pump mid-infrared-probe setup is implemented, which allows for two-dimensional time-resolved experiments in the far-infrared wavelength range. Field ionization of neutral shallow donors in gallium arsenide with intense, ultrashort THz pulses and subsequent coherent radiative recombination of electrons to impurity ground states is observed at room temperature. The superradiant decay of the nonlinear polarization results in the emission of a coherent signal with picosecond lifetimes. Such nonlinear signals, which exhibit a lifetime ten times longer than in the linear regime are observed for the first time. At low temperatures and THz field strengths below 5 kV/cm, Rabi flopping on shallow donor transitions is demonstrated. For the first time, the polar electron-LO phonon interaction is directly measured in the quantum kinetic transport regime. Quasi-instantaneous acceleration of conduction band electrons in the polar gallium arsenide lattice by the electric field of intense THz pulses and subsequent probing of the mid-infrared transmission reveals a modulation of the transmission along the THz-mid-infrared delay coordinate with the frequency of the LO phonon. These modulations directly display the relative phase between the electron motion and its surrounding virtual phonon cloud. Quantum kinetic model calculations fully account for the observed phenomena. (orig.)

Vectorial diffraction properties of THz vortex Bessel beams.

Science.gov (United States)

Wu, Zhen; Wang, Xinke; Sun, Wenfeng; Feng, Shengfei; Han, Peng; Ye, Jiasheng; Yu, Yue; Zhang, Yan

2018-01-22

A vortex Bessel beam combines the merits of an optical vortex and a Bessel beam, including a spiral wave front and a non-diffractive feature, which has immense application potentials in optical trapping, optical fabrication, optical communications, and so on. Here, linearly and circularly polarized vortex Bessel beams in the terahertz (THz) frequency range are generated by utilizing a THz quarter wave plate, a spiral phase plate, and Teflon axicons with different opening angles. Taking advantage of a THz focal-plane imaging system, vectorial diffraction properties of the THz vortex Bessel beams are comprehensively characterized and discussed, including the transverse (Ex, Ey) and longitudinal (Ez) polarization components. The experimental phenomena are accurately simulated by adopting the vectorial Rayleigh diffraction integral. By varying the opening angle of the axicon, the characteristic parameters of these THz vortex Bessel beams are exhibited and compared, including the light spot size, the diffraction-free range, and the phase evolution process. This work provides the precise experimental and theoretical bases for the comprehension and application of a THz vortex Bessel beam.

Computational Investigations of THz Transmittance in the Atmosphere

Directory of Open Access Journals (Sweden)

Yang Xingyu

2016-01-01

Full Text Available With the recent scientific advancements in Terahertz (THz wave propagation and reception technology, there has been significant development in new possibilities for using THz waves – offering new possibilities in THz detection and ranging. A first foundational step toward this goal is to better understand THz transmittance in the turbulent atmosphere. In this project, a frequency modulation pattern of THz waves was created by utilizing a system of shifting frequency based on temperature, air humidity, and distance of transmission. The total path loss of the wave in air, based on the wave spread and molecular absorption, was then modeled using radiative transfer theory, onto a set of JavaHAWK filtered-HITRAN data representative of an air sample. This data was used to generate a path loss matrix, which was then used to optimize frequency of transmission for the specific conditions. The concept to be evaluated is whether adaptive frequency modulated THz might usefully decrease transmission losses by adjusting to atmospheric conditions (such as local variations in temperature and humidity.

Polymer microstructured fibers for guiding of THz radiation

DEFF Research Database (Denmark)

Nielsen, Kristian; Bang, Ole; Jepsen, Peter Uhd

2010-01-01

THz radiation, including low-loss transport of THz signals [1] between high-speed devices, integrated components for manipulation of THz light [2], such as power splitters, polarization management, and frequency filters, and confinement of the electric field of a THz signal in a small volume, enabling...... the facets of the fiber have allowed a direct visualization of the guided modes in the fiber [5]. We will discuss the optimal material choice for various kinds of polymer-based fibers, including solid-core and air-core photonic crystal fibers, and show examples of characterization of such components. We...

Waveguide silicon nitride grating coupler

Science.gov (United States)

Litvik, Jan; Dolnak, Ivan; Dado, Milan

2016-12-01

Grating couplers are one of the most used elements for coupling of light between optical fibers and photonic integrated components. Silicon-on-insulator platform provides strong confinement of light and allows high integration. In this work, using simulations we have designed a broadband silicon nitride surface grating coupler. The Fourier-eigenmode expansion and finite difference time domain methods are utilized in design optimization of grating coupler structure. The fully, single etch step grating coupler is based on a standard silicon-on-insulator wafer with 0.55 μm waveguide Si3N4 layer. The optimized structure at 1550 nm wavelength yields a peak coupling efficiency -2.6635 dB (54.16%) with a 1-dB bandwidth up to 80 nm. It is promising way for low-cost fabrication using complementary metal-oxide- semiconductor fabrication process.

Investigation of 0.38 THz backward-wave oscillator based on slotted sine waveguide and pencil electron beam

Energy Technology Data Exchange (ETDEWEB)

Zhang, Luqi; Wei, Yanyu; Wang, Bing; Shen, Wenan; Xu, Jin; Gong, Yubin [National Key Laboratory of Science and Technology on Vacuum Electronics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Park, Gun-Sik [The Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

2016-03-15

A novel backward wave oscillator (BWO) is presented by utilizing a slotted sine waveguide with a pencil electron beam to produce the high power terahertz wave. The high frequency characteristics including dispersion properties, interaction impedances, and transmission characteristics of the slotted sine waveguide are analyzed in detail. The high frequency system including the output coupler, slow wave structure (SWS), and reflector are designed properly. A 3-D particle-in-cell mode is applied to predict the device performance of the BWO based on the novel SWS. The investigation results demonstrate that this device can generate over 8.05 W output power in the frequency range of 363.4–383.8 GHz by using a 30 mA pencil electron beam and adjusting the beam voltage from 20 kV to 32 kV.

Graphene-enhanced metamaterials in THz applications

DEFF Research Database (Denmark)

Andryieuski, Andrei; Chigrin, Dmitry N.; Khromova, Irina

Terahertz (THz) radiation is widely employed in a broad range of fields in biology, medicine, communication, security, chemistry, and spectroscopy. To expand the application of terahertz radiation new device designs and fabrication methods are needed. The ability of metamaterials to manipulate...... electromagnetic waves makes them natural candidates for THz optical components [1]. However, ranges of light manipulation can be strongly expanded by involving graphene as a structural component of metamaterials. The interplay between interband and intraband transitions in graphene allows converting a multilayer...... on hyperbolic-like dispersion [4]. We believe that graphene-enhanced metamaterials constitute a useful functional element for the THz-infrared integrated optics devices....

Novel THz-Frequency Spectrometers by Integrating Widely-Tunable Monochromatic THz Sources and Detectors, or Arrays of Emitters and Detectors, with Photonic Bandgap Crystals

National Research Council Canada - National Science Library

Zotova, Yuliya

2004-01-01

.... Third, we have used our tunable THz source to take a THz picture of an object (proof of principle). Fourth, we have observed up-conversion process, which can be used as a new detection scheme for THz waves at room temperature...

Compact broadband polarization beam splitter using a symmetric directional coupler with sinusoidal bends.

Science.gov (United States)

Zhang, Fan; Yun, Han; Wang, Yun; Lu, Zeqin; Chrostowski, Lukas; Jaeger, Nicolas A F

2017-01-15

We design and demonstrate a compact broadband polarization beam splitter (PBS) using a symmetric directional coupler with sinusoidal bends on a silicon-on-insulator platform. The sinusoidal bends in our PBS suppress the power exchange between two parallel symmetric strip waveguides for the transverse-electric (TE) mode, while allowing for the maximum power transfer to the adjacent waveguide for the transverse-magnetic (TM) mode. Our PBS has a nominal coupler length of 8.55 μm, and it has an average extinction ratio (ER) of 12.0 dB for the TE mode, an average ER of 20.1 dB for the TM mode, an average polarization isolation (PI) of 20.6 dB for the through port, and an average PI of 11.5 dB for the cross port, all over a bandwidth of 100 nm.

Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam.

Science.gov (United States)

Li, Weiwei; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

2016-06-01

We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure.

Reflective terahertz (THz) imaging: system calibration using hydration phantoms

Science.gov (United States)

Bajwa, Neha; Garritano, James; Lee, Yoon Kyung; Tewari, Priyamvada; Sung, Shijun; Maccabi, Ashkan; Nowroozi, Bryan; Babakhanian, Meghedi; Sanghvi, Sajan; Singh, Rahul; Grundfest, Warren; Taylor, Zachary

2013-02-01

Terahertz (THz) hydration sensing continues to gain traction in the medical imaging community due to its unparalleled sensitivity to tissue water content. Rapid and accurate detection of fluid shifts following induction of thermal skin burns as well as remote corneal hydration sensing have been previously demonstrated in vivo using reflective, pulsed THz imaging. The hydration contrast sensing capabilities of this technology were recently confirmed in a parallel 7 Tesla Magnetic Resonance (MR) imaging study, in which burn areas are associated with increases in local mobile water content. Successful clinical translation of THz sensing, however, still requires quantitative assessments of system performance measurements, specifically hydration concentration sensitivity, with tissue substitutes. This research aims to calibrate the sensitivity of a novel, reflective THz system to tissue water content through the use of hydration phantoms for quantitative comparisons of THz hydration imagery.Gelatin phantoms were identified as an appropriate tissue-mimicking model for reflective THz applications, and gel composition, comprising mixtures of water and protein, was varied between 83% to 95% hydration, a physiologically relevant range. A comparison of four series of gelatin phantom studies demonstrated a positive linear relationship between THz reflectivity and water concentration, with statistically significant hydration sensitivities (p hydration). The THz-phantom interaction is simulated with a three-layer model using the Transfer Matrix Method with agreement in hydration trends. Having demonstrated the ability to accurately and noninvasively measure water content in tissue equivalent targets with high sensitivity, reflective THz imaging is explored as a potential tool for early detection and intervention of corneal pathologies.

Performance of Ar+-milled Ti:Sapphire rib waveguides as single transverse-mode broadband fluorescence sources

NARCIS (Netherlands)

Grivas, C.; Shepherd, D.P.; May-Smith, T.C.; Eason, R.W.; Pollnau, Markus; Crunteanu, A.; Jelinek, M.

2003-01-01

Rib waveguides have been fabricated in pulsed-laser-deposited Ti:sapphire layers using photolithographic patterning and subsequent Ar+-beam milling. Fluorescence output powers up to 300 W have been observed from the ribs following excitation by a 3-W multiline argon laser. Mode intensity profiles

Differentiation of illicit drugs with THz time-domain spectroscopy

International Nuclear Information System (INIS)

Liu Guifeng; Ma Shihua; Ji Te; Zhao Hongwei; Wang Wenfeng

2010-01-01

The tera hertz time-domain spectroscopy (THz-TDS) was used for sensing and identifying illicit drugs. The absorption spectra of seven illicit drug samples(morphine and its hydrochloride, cocaine hydrochloride, codeine phosphate, papaverine hydrochloride, pethidine hydrochloride, and thebaine) were studied by THz-TDS at 0.3-2.0 THz at room temperature. The geometric structure and vibration frequencies of morphine were calculated by density functional theory. The four absorption features were dominated by intra-/inter-molecular collective or lattice vibration modes. Each illicit drug has a distinct signature in its THz spectra. The results indicate that the THz-TDS can be used to identify and discriminate illicit drugs by their characteristic fingerprints. (authors)

Strong terahertz field generation, detection, and application

Energy Technology Data Exchange (ETDEWEB)

Kim, Ki-Yong [Univ. of Maryland, College Park, MD (United States)

2016-05-22

This report describes the generation and detection of high-power, broadband terahertz (THz) radiation with using femtosecond terawatt (TW) laser systems. In particular, this focuses on two-color laser mixing in gases as a scalable THz source, addressing both microscopic and macroscopic effects governing its output THz yield and radiation profile. This also includes the characterization of extremely broad THz spectra extending from microwaves to infrared frequencies. Experimentally, my group has generated high-energy (tens of microjoule), intense (>8 MV/cm), and broadband (0.01~60 THz) THz radiation in two-color laser mixing in air. Such an intense THz field can be utilized to study THz-driven extremely nonlinear phenomena in a university laboratory.

Strong terahertz field generation, detection, and application

Energy Technology Data Exchange (ETDEWEB)

Kim, Ki-Yong [Univ. of Maryland, College Park, MD (United States)

2016-05-15

This report describes the generation and detection of high-power, broadband terahertz (THz) radiation with using femtosecond terawatt (TW) laser systems. In particular, this focuses on two-color laser mixing in gases as a scalable THz source, addressing both microscopic and macroscopic effects governing its output THz yield and radiation profile. This also includes the characterization of extremely broad THz spectra extending from microwaves to infrared frequencies. Experimentally, my group has generated high-energy (tens of microjoule), intense (>8 MV/cm), and broadband (0.01~60 THz) THz radiation in two-color laser mixing in air. Such an intense THz field can be utilized to study THz-driven extremely nonlinear phenomena in a university laboratory.

Broadband terahertz generation of metamaterials

Science.gov (United States)

Luo, Liang; Wang, Jigang; Koschny, Thomas; Wegener, Martin; Soukoulis, Costas M.

2017-06-20

Provided are systems and methods to generate single-cycle THz pulses from a few tens of nanometers thin layer of split ring resonators (SRRs) via optical rectification of femtosecond laser pulses. The emitted THz radiation, with a spectrum ranging from about 0.1 to 4 THz, arises exclusively from pumping the magnetic-dipole resonance of SRRs around 200 THz. This resonant enhancement, together with pump polarization dependence and power scaling of the THz emission, underpins the nonlinearity from optically induced circulating currents in SRRs, with a huge effective nonlinear susceptibility of 0.8.times.10.sup.-16 m.sup.2/V that far exceeds surface nonlinearities of both thin films and bulk organic/inorganic crystals and sheet nonlinearities of non-centrosymmetric materials such as ZnTe.

Widely tunable THz synthesizer

Science.gov (United States)

Hindle, F.; Mouret, G.; Eliet, S.; Guinet, M.; Cuisset, A.; Bocquet, R.; Yasui, T.; Rovera, D.

2011-09-01

The generation of cw-THz radiation by photomixing is particularly suited to the high resolution spectroscopy of gases; nevertheless, until recently, it has suffered from a lack of frequency metrology. Frequency combs are a powerful tool that can transfer microwave frequency standards to optical frequencies and a single comb has permitted accurate (10-8) THz frequency synthesis with a limited tuning range. A THz synthesizer composed of three extended cavity laser diodes phase locked to a frequency comb has been constructed and its utility for high resolution gas phase spectroscopy demonstrated. The third laser diode allows a larger tuning range of up to 300 MHz to be achieved without the need for large frequency excursions, while the frequency comb provides a versatile link to be established from any traceable microwave frequency standard. The use of a single frequency comb as a reference for all of the cw-lasers eliminates the dependency of synthesized frequency on the carrier envelope offset frequency. This greatly simplifies the frequency comb stabilization requirements and leads to a reduced instrument complexity.

Large antennas for ground-based astronomy above 1 THz

NARCIS (Netherlands)

Wild, Wolfgang; Guesten, R.; Holland, W. S.; Ivison, R.; Stacey, G. J.

2006-01-01

In its history astronomy has continuously expanded access to new wavelength regions both from space and on the ground. Today, one of the few unexplored regimes is the terahertz (THz) frequency range, more specifically above 1 THz (< lambda 300 mum). Astronomical observations above 1 THz are

Exact equivalent straight waveguide model for bent and twisted waveguides

DEFF Research Database (Denmark)

Shyroki, Dzmitry

2008-01-01

Exact equivalent straight waveguide representation is given for a waveguide of arbitrary curvature and torsion. No assumptions regarding refractive index contrast, isotropy of materials, or particular morphology in the waveguide cross section are made. This enables rigorous full-vector modeling...... of in-plane curved or helically wound waveguides with use of available simulators for straight waveguides without the restrictions of the known approximate equivalent-index formulas....

Ultrabroadband THz time-domain spectroscopy of biomolecular crystals

DEFF Research Database (Denmark)

Kaltenecker, Korbinian J.; Engelbrecht, Sebastian; Iwaszczuk, Krzysztof

2016-01-01

Ultrabroadband THz time-domain spectroscopy based on two-color plasma generation and air biased coherent detection is used for the investigation of molecular dynamics of crystalline materials in the frequency range from 0.3 THz to 20 THz. We show that the spectral features in this extended...... frequency range are a result of inter- and intramolecular vibrations which are identified by means of simulations of the crystalline materials....

Active THz inspection of water content in plants

Science.gov (United States)

Etayo, D.; Iriarte, J. C.; Palacios, I.; Teniente, J.; Ederra, I.; Gonzalo, R.

2010-04-01

The THz range offers the possibility of measuring water content. This can be useful in wine industry to control plants water levels and also to decrease irrigation costs. This paper presents a THz imaging system used to characterise water content in leaves using frequency and time domain methods from 0.14 to 0.22 THz. Our results show the possibility of getting useful information out of the preformed measurements.

Nonlinear propagation of strong-field THz pulses in doped semiconductors

DEFF Research Database (Denmark)

Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias C.

2012-01-01

We report on nonlinear propagation of single-cycle THz pulses with peak electric fields reaching 300 kV/cm in n-type semiconductors at room temperature. Dramatic THz saturable absorption effects are observed in GaAs, GaP, and Ge, which are caused by the nonlinear electron transport in THz fields....... The semiconductor conductivity, and hence the THz absorption, is modulated due to the acceleration of carriers in strong THz fields, leading to an increase of the effective mass of the electron population, as the electrons are redistributed from the low-momentum, low-effective-mass states to the high-momentum, high...

Active metamaterial: Gain and stability, and microfluidic chip for THz cell spectroscopy

Science.gov (United States)

Tang, Qi

Metamaterials are artificially designed composite materials which can exhibit unique and unusual properties such as the negative refractive index, negative phase velocity, etc. The concept of metamaterials becomes prevalent in the electromagnetic society since the first experimental implementation in the early 2000s. Many fascinated potential applications, e.g. super lens, invisibility cloaking, and novel antennas that are electrically small, have been proposed based on metamaterials. However, most of the applications still remain in theory and are not suitable for practical applications mainly due to the intrinsic loss and narrow bandwidth (large dispersion) determined by the fundamental physics of metamaterials. In this dissertation, we incorporate active gain devices into conventional passive metamaterials to overcome loss and even provide gain. Two types of active gain negative refractive index metamaterials are proposed, designed and experimentally demonstrated, including an active composite left-/right-handed transmission line and an active volumetric metamaterial. In addition, we investigate the non-Foster circuits for broadband matching of electrically small antennas. A rigorous way of analyzing the stability of non-Foster circuits by normalized determinant function is proposed. We study the practical factors that may affect the stability of non-Foster circuits, including the device parasitics, DC biasing, layouts and load impedance. A stable floating negative capacitor is designed, fabricated and tested. Moreover, it is important to resolve the sign of refractive index for active gain media which can be quite challenging. We investigate the analytical solution of a gain slab system, and apply the Nyquist criterion to analyze the stability of a causal gain medium. We then emphasize that the result of frequency domain simulation has to be treated with care. Lastly, this dissertation discusses another interesting topic about THz spectroscopy of live cells

Broadband non-polarizing beam splitter based on guided mode resonance effect

Science.gov (United States)

Ma, Jian-Yong; Xu, Cheng; Qiang, Ying-Huai; Zhu, Ya-Bo

2011-10-01

A broadband non-polarizing beam splitter (NPBS) operating in the telecommunication C+L band is designed by using the guided mode resonance effect of periodic silicon-on-insulator (SOI) elements. It is shown that this double layer SOI structure can provide ~50/50 beam ratio with the maximum divergences between reflection and transmission being less than 8% over the spectrum of 1.4 μm~1.7 μm and 1% in the telecommunication band for both TE and TM polarizations. The physical basis of this broadband non-polarizing property is on the simultaneous excitation of the TE and TM strong modulation waveguide modes near the designed spectrum band. Meanwhile, the electric field distributions for both TE and TM polarizations verify the resonant origin of spectrum in the periodic SOI structure. Furthermore, it is demonstrated with our calculations that the beam splitter proposed here is tolerant to the deviations of incident angle and structure parameters, which make it very easy to be fabricated with current IC technology.

[Application of THz technology to nondestructive detection of agricultural product quality].

Science.gov (United States)

Jiang, Yu-ying; Ge, Hong-yi; Lian, Fei-yu; Zhang, Yuan; Xia, Shan-hong

2014-08-01

With recent development of THz sources and detector, applications of THz radiation to nondestructive testing and quality control have expanded in many fields, such as agriculture, safety inspection and quality control, medicine, biochemistry, communication etc. Compared with other detection technique, being a new kind of technique, THz radiation has low energy, good perspectivity, and high signal-to-noise ratio, and thus can obtain physical, chemical and biological information. This paper first introduces the basic concept of THz radiation and the major properties, then gives an extensive review of recent research progress in detection of the quality of agricultural products via THz technique, analyzes the existing shortcomings of THz detection and discusses the outlook of potential application, finally proposes the new application of THz technique to detection of quality of stored grain.

3D-printed phase waveplates for THz beam shaping

Science.gov (United States)

Gospodaric, J.; Kuzmenko, A.; Pimenov, Anna; Huber, C.; Suess, D.; Rotter, S.; Pimenov, A.

2018-05-01

The advancement of 3D-printing opens up a new way of constructing affordable custom terahertz (THz) components due to suitable printing resolution and THz transparency of polymer materials. We present a way of calculating, designing, and fabricating a THz waveplate that phase-modulates an incident THz beam (λ0 = 2.14 mm) in order to create a predefined intensity profile of the optical wavefront on a distant image plane. Our calculations were performed for two distinct target intensities with the use of a modified Gerchberg-Saxton algorithm. The resulting phase-modulating profiles were used to model the polylactide elements, which were printed out with a commercially available 3D-printer. The results were tested in a THz experimental setup equipped with a scanning option, and they showed good agreement with theoretical predictions.

THz characterization of hydrated and anhydrous materials

Science.gov (United States)

Sokolnikov, Andre

2011-06-01

The characterization of anhydrous and hydrated forms of materials is of great importance to science and industry. Water content poses difficulties for successful identification of the material structure by THz radiation. However, biological tissues and hydrated forms of nonorganic substances still may be investigated by THz radiation. This paper outlines the range of possibilities of the above characterization, as well as provides analysis of the physical mechanism that allows or prevents penetration of THz waves through the substance. THz-TDS is used to measure the parameters of the characterization of anhydrous and hydrated forms of organic and nonorganic samples. Mathematical methods (such as prediction models of time-series analysis) are used to help identifying the absorption coefficient and other parameters of interest. The discovered dependencies allow designing techniques for material identification/characterization (e.g. of drugs, explosives, etc. that may have water content). The results are provided.

Lateral strukturierte Oberflächen zur THz-Strahlmanipulation

OpenAIRE

Jahn, David; Koch, Martin (Prof. Dr.)

2018-01-01

Die Terahertz-Zeitbereichsspektroskopie ist mittlerweile eine etablierte spektroskopische Methode im Frequenzbereich von 0;2 THz bis etwa 5 THz. Mit der stetigen Verbesserung von Zeitbereichs-Spektrometern, in den letzten Jahren hauptsächlich vorangetrieben durch die Verbesserung der Materialsysteme sowohl im photoleitenden Emitter als auch im Detektor sind heute Systeme mit bis zu 90 dB SNR und 4;5 THz Brandbreite verfügbar. Auch der Einfluss anderer Systemkomponenten, deren Beitrag zum...

Highly efficient quantum dot-based photoconductive THz materials and devices

Science.gov (United States)

Rafailov, E. U.; Leyman, R.; Carnegie, D.; Bazieva, N.

2013-09-01

We demonstrate Terahertz (THz) signal sources based on photoconductive (PC) antenna devices comprising active layers of InAs semiconductor quantum dots (QDs) on GaAs. Antenna structures comprised of multiple active layers of InAs:GaAs PC materials are optically pumped using ultrashort pulses generated by a Ti:Sapphire laser and CW dualwavelength laser diodes. We also characterised THz output signals using a two-antenna coherent detection system. We discuss preliminary performance data from such InAs:GaAs THz devices which exhibit efficient emission of both pulsed and continuous wave (CW) THz signals and significant optical-to-THz conversion at both absorption wavelength ranges, <=850 nm and <=1300 nm.

Josephson admittance spectroscopy application for frequency analysis of broadband THz antennas

International Nuclear Information System (INIS)

Volkov, O Yu; Divin, Yu Yu; Gubankov, V N; Gundareva, I I; Pavlovskiy, V V

2010-01-01

Application of Josephson admittance spectroscopy for the spectral analysis of a broad-band log-periodic superconducting antenna was demonstrated at the frequency range from 50 to 700 GHz. The [001]-tilt YBa 2 Cu 3 O 7-x bicrystal Josephson junctions, integrated with sinuous log-periodic YBa 2 Cu 3 O 7-x antennas, were fabricated on NdGaO 3 bicrystal substrates. A real part of the antenna admittance ReY(f) as a function of the frequency f was reconstructed from the modification of the dc current-voltage characteristic of the junction, induced by the antenna. Resonance features were observed in the recovered ReY(f)-spectra with a periodicity in the logarithmic frequency scale, corresponding to log-periodic geometry of the antenna. The ReY(f)-spectra, recovered by Josephson spectroscopy, were compared with the ReY(f)-spectra, obtained by CAD simulation, and both spectra were shown to be similar in their main features. A value of 23 was obtained for an effective permittivity of the NdGaO3 bicrystal substrates by fitting simulated data to those obtained from Josephson spectroscopy.

THz computed tomography system with zero-order Bessel beam

Science.gov (United States)

Niu, Liting; Wu, Qiao; Wang, Kejia; Liu, Jinsong; Yang, Zhengang

2018-01-01

Terahertz (THz) waves can penetrate many optically opaque dielectric materials such as plastics, ceramics and colorants. It is effective to reveal the internal structures of these materials. We have built a THz Computed Tomography (CT) system with 0.3 THz zero-order Bessel beam to improve the depth of focus of this imaging system for the non-diffraction property of Bessel beam. The THz CT system has been used to detect a paper cup with a metal rod inside. Finally, the acquired projection data have been processed by the filtered back-projection algorithm and the reconstructed image of the sample has been obtained.

THz-wave generation via stimulated polariton scattering in KTiOAsO4 crystal.

Science.gov (United States)

Wang, Weitao; Cong, Zhenhua; Liu, Zhaojun; Zhang, Xingyu; Qin, Zengguang; Tang, Guanqi; Li, Ning; Zhang, Yuangeng; Lu, Qingming

2014-07-14

A terahertz parametric oscillator based on KTiOAsO(4) crystal is demonstrated for the first time. With the near-forward scattering configuration X(ZZ)X + Δφ, the polarizations of the pump, the Stokes and the generated THz waves are parallel to the z-axis of the crystal KTA. When the incident angle θext of the pump wave is changed from 1.875° to 6.500°, the THz wave is intermittently tuned from 3.59 to 3.96 THz, from 4.21 to 4.50 THz, from 4.90 to 5.16 THz, from 5.62 to 5.66 THz and from 5.92 to 6.43 THz. The obtained maximum THz wave energy is 627 nJ at 4.30 THz with a pump energy of 100 mJ. It is believed that the terahertz wave generation is caused by the stimulated scattering of the polaritons associated with the most intensive transverse A(1) mode of 233.8 cm(-1). Four much weaker transverse A(1) modes of 132.9 cm(-1), 156.3 cm(-1),175.1 cm(-1), and 188.4 cm(-1) cause four frequency gaps, from 3.97 THz to 4.20 THz, from 4.51 to 4.89 THz, from 5.17 to 5.61 THz and from 5.67 to 5.91 THz, respectively.

Terahertz-wave surface-emitted difference-frequency generation without quasi-phase-matching technique.

Science.gov (United States)

Avetisyan, Yuri H

2010-08-01

A scheme of terahertz (THz)-wave surface-emitted difference-frequency generation (SEDFG), which lacks the drawbacks associated with the usage of periodically orientation-inverted structures, is proposed. It is shown that both material birefringence of the bulk LiNbO(3) crystal and modal birefringence of GaAs/AlAs waveguide are sufficient to obtain SEDFG up to a frequency of approximately 3THz. The simplicity of the proposed scheme, along with the fact that there is a much smaller THz-wave decay in nonlinear crystal, makes it a good candidate for the practical realization of efficient THz generation. The use of a GaAs waveguide with an oxidized AlAs layer is proposed for enhanced THz-wave SEDFG in the vicinity of the GaAs polariton resonance at 8THz.

Current responsivity of semiconductor superlattice THz-photon detectors

DEFF Research Database (Denmark)

Ignatov, Anatoly A.; Jauho, Antti-Pekka

1999-01-01

The current responsivity of a semiconductor superlattice THz-photon detector is calculated using an equivalent circuit model which takes into account the finite matching efficiency between a detector antenna and the superlattice in the presence of parasitic losses. Calculations performed for curr......The current responsivity of a semiconductor superlattice THz-photon detector is calculated using an equivalent circuit model which takes into account the finite matching efficiency between a detector antenna and the superlattice in the presence of parasitic losses. Calculations performed...... for currently available superlattice diodes show that both the magnitudes and the roll-off frequencies of the responsivity are strongly influenced by an excitation of hybrid plasma-Bloch oscillations which are found to be eigenmodes of the system in the THz-frequency band. The expected room temperature values...... of the responsivity (2–3 A/W in the 1–3 THz-frequency band) range up to several percents of the quantum efficiency e/[h-bar] omega of an ideal superconductor tunnel junction detector. Properly designed semiconductor superlattice detectors may thus demonstrate better room temperature THz-photon responsivity than...

A Broadband Waveguide Transfer Standard for Dissemination of UK National Microwave Power Standards,

Science.gov (United States)

1982-01-01

la )PT " RT a where RT is the resistance of the thermistor when the bridge is balanced. Although the thermistor mount is temperature controlled, some...voltage difference V1 - V and Vb - V2 - V then equation la 4 ... . .. mmm mmm mmmmmmmm m m mm mm mmmm m mm A becomes 2V(V - Vb) + V 2 - 2 P a b a b (lb...Weidman, "An international intercomparison of power standards in WR-28 waveguide". Metrologia , 17, June 1981. 4 G F Engen. "A refined X-band microwave

Semiconductor Quantum Dash Broadband Emitters: Modeling and Experiments

KAUST Repository

Khan, Mohammed Zahed Mustafa

2013-10-01

Broadband light emitters operation, which covers multiple wavelengths of the electromagnetic spectrum, has been established as an indispensable element to the human kind, continuously advancing the living standard by serving as sources in important multi-disciplinary field applications such as biomedical imaging and sensing, general lighting and internet and mobile phone connectivity. In general, most commercial broadband light sources relies on complex systems for broadband light generation which are bulky, and energy hungry. \\tRecent demonstration of ultra-broadband emission from semiconductor light sources in the form of superluminescent light emitting diodes (SLDs) has paved way in realization of broadband emitters on a completely novel platform, which offered compactness, cost effectiveness, and comparatively energy efficient, and are already serving as a key component in medical imaging systems. The low power-bandwidth product is inherent in SLDs operating in the amplified spontaneous emission regime. A quantum leap in the advancement of broadband emitters, in which high power and large bandwidth (in tens of nm) are in demand. Recently, the birth of a new class of broadband semiconductor laser diode (LDs) producing multiple wavelength light in stimulated emission regime was demonstrated. This very recent manifestation of a high power-bandwidth-product semiconductor broadband LDs relies on interband optical transitions via quantum confined dot/dash nanostructures and exploiting the natural inhomogeneity of the self-assembled growth technology. This concept is highly interesting and extending the broad spectrum of stimulated emission by novel device design forms the central focus of this dissertation. \\tIn this work, a simple rate equation numerical technique for modeling InAs/InP quantum dash laser incorporating the properties of inhomogeneous broadening effect on lasing spectra was developed and discussed, followed by a comprehensive experimental analysis

Dynamics of a broad-band quantum cascade laser: from chaos to coherent dynamics and mode-locking

Science.gov (United States)

Columbo, L. L.; Barbieri, S.; Sirtori, C.; Brambilla, M.

2018-02-01

The dynamics of a multimode Quantum Cascade Laser, is studied in a model based on effective semiconductor Maxwell-Bloch equations, encompassing key features for the radiationmedium interaction such as an asymmetric, frequency dependent, gain and refractive index as well as the phase-amplitude coupling provided by the Henry factor. By considering the role of the free spectral range and Henry factor, we develop criteria suitable to identify the conditions which allow to destabilize, close to threshold, the traveling wave emitted by the laser and lead to chaotic or regular multimode dynamics. In the latter case our simulations show that the field oscillations are associated to self-confined structures which travel along the laser cavity, bridging mode-locking and solitary wave propagation. In addition, we show how a RF modulation of the bias current leads to active mode-locking yielding high-contrast, picosecond pulses. Our results compare well with recent experiments on broad-band THz-QCLs and may help understanding the conditions for the generation of ultrashort pulses and comb operation in Mid-IR and THz spectral regions

Wave-guided optical waveguides

DEFF Research Database (Denmark)

Palima, Darwin; Bañas, Andrew Rafael; Vizsnyiczai, George

2012-01-01

This work primarily aims to fabricate and use two photon polymerization (2PP) microstructures capable of being optically manipulated into any arbitrary orientation. We have integrated optical waveguides into the structures and therefore have freestanding waveguides, which can be positioned anywhe...... bridge the diffraction barrier. This structure-mediated paradigm may be carried forward to open new possibilities for exploiting beams from far-field optics down to the subwavelength domain....

Enhanced photoresponsivity in graphene-silicon slow-light photonic crystal waveguides

International Nuclear Information System (INIS)

Zhou, Hao; Gu, Tingyi; McMillan, James F.; Yu, Mingbin; Lo, Guoqiang; Kwong, Dim-Lee; Feng, Guoying; Zhou, Shouhuan; Wong, Chee Wei

2016-01-01

We demonstrate the enhanced fast photoresponsivity in graphene hybrid structures by combining the ultrafast dynamics of graphene with improved light-matter interactions in slow-light photonic crystal waveguides. With a 200 μm interaction length, a 0.8 mA/W photoresponsivity is achieved in a graphene-silicon Schottky-like photodetector, with an operating bandwidth in excess of 5 GHz and wavelength range at least from 1480 nm to 1580 nm. Fourfold enhancement of the photocurrent is observed in the slow light region, compared to the wavelength far from the photonic crystal bandedge, for a chip-scale broadband fast photodetector.

Compact, low-loss and broadband photonic crystal circulator based on a star-type ferrite rod

Directory of Open Access Journals (Sweden)

Xiang Xi

Full Text Available We propose and investigate a compact, low-loss and broadband circulator based on a star-type ferrite rod in two-dimensional square-lattice photonic crystals. Only one ferrite rod is required to be inserted in our structure. Firstly, the performances of circulator based on the star-type, circle, and square ferrite rod are compared, showing that the circulator with the star-type ferrite rod performs better than the other two ones. And then, based on the star-type ferrite rod circulator, four cases of improvement, in which the background rods around the center ferrite rod are replaced respectively by the backward-triangle, forward-triangle, backward-semicircle, and forward-semicircle rods, are investigated to modulate the coupling between the center magneto-optical micro-cavity and the corresponding waveguides. The results show that, with proper parameters, all the four cases can greatly improve the output properties of the circulator, and different cases have its own advantages. The mechanism behind these improvements is also discussed. Finite-element method is used to calculate the characteristics of the circulator and Nelder-Mead optimization method is employed to obtain the optimized parameters. The ideas presented here are useful for designing broadband, low insertion loss, and high-isolation circulators which have potential application in integrated photonic crystal devices. Keywords: Photonic crystals, Circulator, Magneto-optical material, Photonic crystal waveguides

European Research on THz Vacuum Amplifiers

DEFF Research Database (Denmark)

Brunetti, F.; Cojocarua, C.-S.; de Rossi, A.

2010-01-01

The OPTHER (OPtically Driven TeraHertz AmplifiERs) project represents a considerable advancement in the field of high frequency amplification. The design and realization of a THz amplifier within this project is a consolidation of efforts at the international level from the main players...... of the European research, academy and industry in vacuum electronics. This paper describes the status of the project and progress towards the THz amplifier realization....

Control of deviations and prediction of surface roughness from micro machining of THz waveguides using acoustic emission signals

Science.gov (United States)

Griffin, James M.; Diaz, Fernanda; Geerling, Edgar; Clasing, Matias; Ponce, Vicente; Taylor, Chris; Turner, Sam; Michael, Ernest A.; Patricio Mena, F.; Bronfman, Leonardo

2017-02-01

By using acoustic emission (AE) it is possible to control deviations and surface quality during micro milling operations. The method of micro milling is used to manufacture a submillimetre waveguide where micro machining is employed to achieve the required superior finish and geometrical tolerances. Submillimetre waveguide technology is used in deep space signal retrieval where highest detection efficiencies are needed and therefore every possible signal loss in the receiver has to be avoided and stringent tolerances achieved. With a sub-standard surface finish the signals travelling along the waveguides dissipate away faster than with perfect surfaces where the residual roughness becomes comparable with the electromagnetic skin depth. Therefore, the higher the radio frequency the more critical this becomes. The method of time-frequency analysis (STFT) is used to transfer raw AE into more meaningful salient signal features (SF). This information was then correlated against the measured geometrical deviations and, the onset of catastrophic tool wear. Such deviations can be offset from different AE signals (different deviations from subsequent tests) and feedback for a final spring cut ensuring the geometrical accuracies are met. Geometrical differences can impact on the required transfer of AE signals (change in cut off frequencies and diminished SNR at the interface) and therefore errors have to be minimised to within 1 μm. Rules based on both Classification and Regression Trees (CART) and Neural Networks (NN) were used to implement a simulation displaying how such a control regime could be used as a real time controller, be it corrective measures (via spring cuts) over several initial machining passes or, with a micron cut introducing a level plain measure for allowing setup corrective measures (similar to a spirit level).

Nanoscale electron manipulation in metals with intense THz electric fields

Science.gov (United States)

Takeda, Jun; Yoshioka, Katsumasa; Minami, Yasuo; Katayama, Ikufumi

2018-03-01

Improved control over the electromagnetic properties of metals on a nanoscale is crucial for the development of next-generation nanoelectronics and plasmonic devices. Harnessing the terahertz (THz)-electric-field-induced nonlinearity for the motion of electrons is a promising method of manipulating the local electromagnetic properties of metals, while avoiding undesirable thermal effects and electronic transitions. In this review, we demonstrate the manipulation of electron delocalization in ultrathin gold (Au) films with nanostructures, by intense THz electric-field transients. On increasing the electric-field strength of the THz pulses, the transmittance in the THz-frequency region abruptly decreases around the percolation threshold. The observed THz-electric-field-induced nonlinearity is analysed, based on the Drude-Smith model. The results suggest that ultrafast electron delocalization occurs by electron tunnelling across the narrow insulating bridge between the Au nanostructures, without material breakdown. In order to quantitatively discuss the tunnelling process, we perform scanning tunnelling microscopy with carrier-envelope phase (CEP)-controlled single-cycle THz electric fields. By applying CEP-controlled THz electric fields to the 1 nm nanogap between a metal nanotip and graphite sample, many electrons could be coherently driven through the quantum tunnelling process, either from the nanotip to the sample or vice versa. The presented concept, namely, electron tunnelling mediated by CEP-controlled single-cycle THz electric fields, can facilitate the development of nanoscale electron manipulation, applicable to next-generation ultrafast nanoelectronics and plasmonic devices.

Numerical and experimental studies of mechanisms underlying the effect of pulsed broadband terahertz radiation on nerve cells

Energy Technology Data Exchange (ETDEWEB)

Duka, M V; Dvoretskaya, L N; Babelkin, N S; Khodzitskii, M K; Chivilikhin, S A; Smolyanskaya, O A [St. Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg (Russian Federation)

2014-08-31

We have studied the mechanisms underlying the effect of pulsed broadband terahertz radiation on the growth of neurites of sensory ganglia using a comparative analysis of measured reflection spectra of ganglion neurites (in the frequency range 0.1 – 2.0 THz) and spectra obtained by numerical simulation with CST Microwave Studio. The observed changes are shown to be mainly due to pulse energy absorption in the ganglion neurites. Of particular interest are the observed single resonance frequencies related to resonance size effects, which can be used to irradiate ganglia in order to activate their growth. (laser biophotonics)

Broadband Access

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Broadband Access. Worldwide market for broadband access $30 Billion! Over 200 million broadband subscribers worldwide! Various Competing Broadband access. Digital Subscriber line; Wireless; Optical Fiber.

Electronic THz-spectrometer for plasmonic enhanced deep subwavelength layer detection

NARCIS (Netherlands)

Berrier, A.; Schaafsma, M.C.; Gómez Rivas, J.; Schäfer-Eberwein, H.; Haring Bolivar, P.; Tripodi, L.; Matters-Kammerer, M.K.

2015-01-01

We demonstrate the operation of a miniaturized all-electronic CMOS based THz spectrometer with performances comparable to that of a THz-TDS spectrometer in the frequency range 20 to 220 GHz. The use of this all-electronic THz spectrometer for detection of a thin TiO2 layer and a B. subtilis bacteria

Interconnect Between a Waveguide and a Dielectric Waveguide Comprising an Impedance Matched Dielectric Lens

Science.gov (United States)

Decrossas, Emmanuel (Inventor); Chattopadhyay, Goutam (Inventor); Chahat, Nacer (Inventor); Tang, Adrian J. (Inventor)

2016-01-01

A lens for interconnecting a metallic waveguide with a dielectric waveguide is provided. The lens may be coupled a metallic waveguide and a dielectric waveguide, and minimize a signal loss between the metallic waveguide and the dielectric waveguide.

Far-infrared cw difference-frequency generation using vertically integrated and planar low temperature grown GaAs photomixers: application to H2S rotational spectrum up to 3 THz

Science.gov (United States)

Mouret, G.; Matton, S.; Bocquet, R.; Hindle, F.; Peytavit, E.; Lampin, J. F.; Lippens, D.

2004-10-01

The generation of continuous coherent THz radiation by mixing two cw Ti:Sa laser beams with a well-controlled frequency separation for a new scheme of vertically integrated low temperature grown GaAs (LTG-GaAs) spiral photomixer is reported. For this new photomixer device used in THz emission, the LTG-GaAs active layer is sandwiched between the two parallel metal plates of a high-speed photodetector loaded by a broadband spiral antenna. We have exploited the advantage of a higher delivered power in the low part of the spectrum (<2000 GHz), while a low RC time constant planar interdigitated detector was used at the upper frequency. The performances of the spectroscopic setup in terms of spectral resolution (5 MHz), tunability and frequency capability are assessed by measurements of the pure rotational spectra of hydrogen sulfide (H2S) up to 3000 GHz.

Ultra-Broad Band Radar Cross Section Reduction of Waveguide Slot Antenna with Metamaterials

Directory of Open Access Journals (Sweden)

Qiang Fu

2016-06-01

Full Text Available To reduce the radar cross section of a waveguide slot antenna, a three-layer metamaterial is presented based on orthogonal double split-ring resonators. The absorption characteristics of three-layer metamaterial are demonstrated by simulation. Moreover, the metamaterials have been loaded on common waveguide slot antenna according to the surface current distribution. The ultra-broad band radar cross section reduction of the antenna with metamaterials had been theoretically and experimentally investigated by radiating and scattering performances. Experimental and simulated results showed that the proposed antenna with metamaterials performed broadband radar cross section reduction from 3.9 GHz to 18 GHz and the gain had been improved due to the coupling effect between slot and the period structure. The maximal radar cross section reduction achieved 17.81 dB at 8.68 GHz for x-polarized incidence and 21.79 dB at 6.25 GHz for y-polarized waves.

NATO Advanced Research Workshop on THz for CBRN and Explosives Detection and Diagnosis

CERN Document Server

Shulika, Oleksiy

2017-01-01

This work is intended to jointly address the development, realization and applications of emitters and detectors of terahertz (THz-0.3 THz up to 10 THz) and their application to diagnostics of CBRN effects and detection of explosives and CBRN. Hazardous substances typically exhibit rotational and vibrational transitions in this region, hence giving access to spectroscopic analysis of a large variety of molecules which play a key role in security as well as various other areas, e.g. air pollution, climate research, industrial process control, agriculture, food industry, workplace safety and medical diagnostics can be monitored by sensing and identifying them via THz (0.3 to 10 THz) and mid infrared (MIR-10 THz to 100 THz) absorption “finger prints”. Most plastics, textiles and paper are nearly transparent for THz radiation.

Passive THz metamaterials

DEFF Research Database (Denmark)

Lavrinenko, Andrei; Malureanu, Radu; Zalkovskij, Maksim

2012-01-01

In this work we present our activities in the fabrication and characterization of passive THz metamaterials. We use two fabrication processes to develop metamaterials either as free-standing metallic membranes or patterned metallic multi-layers on the substrates to achieve different functionalities...

Competition and evolution of dielectric waveguide mode and plasmonic waveguide mode

Science.gov (United States)

Yuan, Sheng-Nan; Fang, Yun-Tuan

2017-10-01

In order to study the coupling and evolution law of the waveguide mode and two plasmonic surface modes, we construct a line defect waveguide based on hexagonal honeycomb plasmonic photonic crystal. Through adjusting the radius of the edge dielectric rods, the competition and evolution behaviors occur between dielectric waveguide mode and plasmonic waveguide mode. There are three status: only plasmonic waveguide modes occur for rA 0.25a; two kinds of modes coexist for 0.09a advantages in achieving slow light.

Broadband non-polarizing terahertz beam splitters with variable split ratio

KAUST Repository

Wei, Minggui

2017-08-15

Seeking effective terahertz functional devices has always aroused extensive attention. Of particular interest is the terahertz beam splitter. Here, we have proposed, designed, manufactured, and tested a broadband non-polarizing terahertz beam splitter with a variable split ratio based on an all-dielectric metasurface. The metasurface was created by patterning a dielectric surface of the N-step phase gradient and etching to a few hundred micrometers. The conversion efficiency as high as 81% under the normal incidence at 0.7 THz was achieved. Meanwhile, such a splitter works well over a broad frequency range. The split ratio of the proposed design can be continuously tuned by simply shifting the metasurface, and the angle of emergences can also be easily adjusted by choosing the step of phase gradients. The proposed design is non-polarizing, and its performance is kept under different polarizations.

Broadband non-polarizing terahertz beam splitters with variable split ratio

Science.gov (United States)

Wei, Minggui; Xu, Quan; Wang, Qiu; Zhang, Xueqian; Li, Yanfeng; Gu, Jianqiang; Tian, Zhen; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

2017-08-01

Seeking effective terahertz functional devices has always aroused extensive attention. Of particular interest is the terahertz beam splitter. Here, we have proposed, designed, manufactured, and tested a broadband non-polarizing terahertz beam splitter with a variable split ratio based on an all-dielectric metasurface. The metasurface was created by patterning a dielectric surface of the N-step phase gradient and etching to a few hundred micrometers. The conversion efficiency as high as 81% under the normal incidence at 0.7 THz was achieved. Meanwhile, such a splitter works well over a broad frequency range. The split ratio of the proposed design can be continuously tuned by simply shifting the metasurface, and the angle of emergences can also be easily adjusted by choosing the step of phase gradients. The proposed design is non-polarizing, and its performance is kept under different polarizations.

Broadband non-polarizing terahertz beam splitters with variable split ratio

KAUST Repository

Wei, Minggui; Xu, Quan; Wang, Qiu; Zhang, Xueqian; Li, Yanfeng; Gu, Jianqiang; Tian, Zhen; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

2017-01-01

Seeking effective terahertz functional devices has always aroused extensive attention. Of particular interest is the terahertz beam splitter. Here, we have proposed, designed, manufactured, and tested a broadband non-polarizing terahertz beam splitter with a variable split ratio based on an all-dielectric metasurface. The metasurface was created by patterning a dielectric surface of the N-step phase gradient and etching to a few hundred micrometers. The conversion efficiency as high as 81% under the normal incidence at 0.7 THz was achieved. Meanwhile, such a splitter works well over a broad frequency range. The split ratio of the proposed design can be continuously tuned by simply shifting the metasurface, and the angle of emergences can also be easily adjusted by choosing the step of phase gradients. The proposed design is non-polarizing, and its performance is kept under different polarizations.

Generation and detection of ultrabroadband infrared wave exceeding 200 THz

Directory of Open Access Journals (Sweden)

Ashida Masaaki

2013-03-01

Full Text Available By focusing a hollow-fiber compressed intense 10–fs pulse and its second harmonic in air, an ultrabroadband infrared pulse with a spectral range of 1–200 THz is generated through a plasma. Coherent detection of the signal up to 100 THz is achieved with electro–optic sampling and THz air-breakdown-coherent-detection. The drastic dependence on the orientation of the second harmonic crystal is clarified in a range of 100–200 THz. From these, the whole frequency components are confirmed to be generated from the AC biased plasma and phase-locked.

In vitro osteosarcoma biosensing using THz time domain spectroscopy

Science.gov (United States)

Ferguson, Bradley S.; Liu, Haibo; Hay, Shelley; Findlay, David; Zhang, Xi-Cheng; Abbott, Derek

2004-03-01

Terahertz time domain spectroscopy (THz-TDS) has a wide range of applications from semiconductor diagnostics to biosensing. Recent attention has focused on bio-applications and several groups have noted the ability of THz-TDS to differentiate basal cell carcinoma tissue from healthy dermal tissue ex vivo. The contrast mechanism is unclear but has been attributed to increased interstitial water in cancerous tissue. In this work we investigate the THz response of human osteosarcoma cells and normal human bone cells grown in culture to isolate the cells' responses from other effects. A classification algorithms based on a frequency selection by genetic algorithm is used to attempt to differentiate between the cell types based on the THz spectra. Encouraging preliminary results have been obtained.

Ultrabroadband THz Time-Domain Spectroscopy of a Free-Flowing Water Film

DEFF Research Database (Denmark)

Wang, Tianwu; Pedersen, Pernille Klarskov; Jepsen, Peter Uhd

2014-01-01

of liquid water using two different THz-TDS setups. The extracted absorption coefficient and refractive index of water are in agreement with previous results reported in the literature. With this we show that the thin free-flowing liquid film is a versatile tool for windowless, ultrabroadband THz......We demonstrate quantitative ultrabroadband THz time-domain spectroscopy (THz-TDS) of water by application of a 17-$\\mu$m thick gravity-driven wire-guided flow jet of water. The thickness and stability of the water film is accurately measured by an optical intensity crosscorrelator, and the standard...... deviation of the film thickness is less than 500 nm. The cross section of the water film is found to have a biconcave cylindrical lens shape. By transmitting through such a thin film, we perform the first ultrabroadband (0.2–30 THz) THz-TDS across the strongest absorbing part of the infrared spectrum...

Broadband non-polarizing beam splitter based on guided mode resonance effect

International Nuclear Information System (INIS)

Ma Jian-Yong; Xu Cheng; Qiang Ying-Huai; Zhu Ya-Bo

2011-01-01

A broadband non-polarizing beam splitter (NPBS) operating in the telecommunication C+L band is designed by using the guided mode resonance effect of periodic silicon-on-insulator (SOI) elements. It is shown that this double layer SOI structure can provide ∼50/50 beam ratio with the maximum divergences between reflection and transmission being less than 8% over the spectrum of 1.4 μm∼1.7 μm and 1% in the telecommunication band for both TE and TM polarizations. The physical basis of this broadband non-polarizing property is on the simultaneous excitation of the TE and TM strong modulation waveguide modes near the designed spectrum band. Meanwhile, the electric field distributions for both TE and TM polarizations verify the resonant origin of spectrum in the periodic SOI structure. Furthermore, it is demonstrated with our calculations that the beam splitter proposed here is tolerant to the deviations of incident angle and structure parameters, which make it very easy to be fabricated with current IC technology. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

THz Spectroscopic Identification of Red Mineral Pigments in Ancient Chinese Artworks

Science.gov (United States)

Yang, Yuping; Zhai, Dongwei; Zhang, Zhenwei; Zhang, Cunlin

2017-10-01

Nondestructive analysis of historical objects is of significance for cultural heritage conservation. In this paper, terahertz time-domain spectroscopy (THz-TDS) was used to distinguish seven red mineral pigments used in ancient Chinese artworks. Two absorption features of natural minerals HgS and four highly resolved spectral features of mineral pigment Pb3O4 were observed and identified as their fingerprints in the range 0.2 to 3.0 THz, based on which the spatial distribution of individual chemical substances including cinnabar, vermilion, and red lead were clearly revealed at various frequencies using terahertz spectroscopy imaging. Moreover, a noncontact evaluation of thickness changing and dehydration of a wet painting was monitored by inferring time delay as well as signal amplitude of THz pulses transmitted through the painting. In order to demonstrate the feasibility of THz-TDS and THz imaging for authentic artworks detection, a complete set of THz analysis of two nineteenth century wall paintings discovered in the Fuchen Temple of the Forbidden City, Beijing, was performed and the results indicate that THz measurement techniques provide a noninvasive and nondestructive solution for the care, preservation, and restoration of cultural relics.

Modeling of dispersion engineered chalcogenide rib waveguide for ultraflat mid-infrared supercontinuum generation in all-normal dispersion regime

Science.gov (United States)

Ahmad, H.; Karim, M. R.; Rahman, B. M. A.

2018-03-01

A rigorous numerical investigation has been carried out through dispersion engineering of chalcogenide rib waveguide for near-infrared to mid-infrared ultraflat broadband supercontinuum generation in all-normal group-velocity dispersion regime. We propose a novel design of a 1-cm-long air-clad rib waveguide which is made from {Ge}_{11.5} {As}_{24} {Se}_{64.5} chalcogenide glass as the core with either silica or {Ge}_{11.5} {As}_{24} {S}_{64.5} chalcogenide glass as a lower cladding separately. A broadband ultraflat supercontinuum spanning from 1300 to 1900 nm could be generated when pumped at 1.55 μ {m} with a low input peak power of 100 W. Shifting the pump to 2 μ {m}, the supercontinuum spectra extended in the mid-infrared region up to 3400 nm with a moderate-input peak power of 500 W. To achieve further extension in mid-infrared, we excite our optimized rib waveguide in both the anomalous and all-normal dispersion pumping regions at 3.1 μ {m} with a largest input peak power of 3 kW. In the case of anomalous dispersion region pumping, numerical analysis shows that supercontinuum spectrum can be extended in the mid-infrared up to 10 μ {m}, although this contains high spectral amplitude fluctuations over the entire bandwidth which limits the supercontinuum sources in the field of high precision measurement applications. On the other hand, by optimizing a rib waveguide geometry for pumping in all-normal dispersion region, we are able to generate a smooth and flat-top coherent supercontinuum spectrum with a moderate bandwidth spanning the wavelength range 2-5.5 μ {m} with less than 5 dB spectral fluctuation over the entire output bandwidth. Our proposed design is highly suitable for making on-chip SC light sources for a variety of applications such as biomedical imaging, and environmental and industrial sensing in the mid-infrared region.

Probing giant magnetoresistance with THz spectroscopy

DEFF Research Database (Denmark)

Jin, Zuanming; Tkach, Alexander; Casper, Frederick

2014-01-01

We observe a giant magnetoresistance effect in CoFe/Cu-based multistack using THz time-domain spectroscopy. The magnetic field-dependent dc conductivity, electron scattering time, as well as spin-asymmetry parameter of the structure are successfully determined. © 2014 OSA.......We observe a giant magnetoresistance effect in CoFe/Cu-based multistack using THz time-domain spectroscopy. The magnetic field-dependent dc conductivity, electron scattering time, as well as spin-asymmetry parameter of the structure are successfully determined. © 2014 OSA....

Excitation of THz hybrid modes in an elliptical dielectric rod waveguide with a cold collisionless unmagnetized plasma column by an annular electron beam

Energy Technology Data Exchange (ETDEWEB)

Rahmani, Z., E-mail: z.rahmani@kashanu.ac.ir; Safari, S. [Department of Laser and Photonics, Faculty of Physics, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of); Heidari-Semiromi, E. [Department of Condense Matter, Faculty of Physics, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of)

2016-06-15

The dispersion relation of electromagnetic waves propagating in an elliptical plasma waveguide with a cold collisionless unmagnetized plasma column and a dielectric rod is studied analytically. The frequency spectrum of the hybrid waves and the growth rate for excitation of the waves by a thin annular relativistic elliptical electron beam (TAREEB) is obtained. The effects of relative permittivity constant of dielectric rod, geometrical dimensions, plasma frequency, accelerating voltage, and current density of TAREEB on the growth rate and frequency spectra of the waveguide will be investigated.

Semiconductor Nonlinear Dynamics Study by Broadband Terahertz Spectroscopy

Science.gov (United States)

Ho, I.-Chen

Semiconductor nonlinearity in the terahertz (THz) frequency range has been attracting considerable attention due to the recent development of high-power semiconductor-based nanodevices. However, the underlying physics concerning carrier dynamics in the presence of high-field THz transients is still obscure. This thesis introduces an ultrafast, time-resolved THz pump/THz probe approach to the study of semiconductor properties in the nonlinear regime. The carrier dynamics regarding two mechanisms, intervalley scattering and impact ionization, is observed for doped InAs on a sub-picosecond time scale. In addition, polaron modulation driven by intense THz pulses is experimentally and theoretically investigated. The observed polaron dynamics verifies the interaction between energetic electrons and a phonon field. In contrast to previous work which reports optical phonon responses, acoustic phonon modulations are addressed in this study. A further understanding of the intense field interacting with solid materials will accelerate the development of semiconductor devices. This thesis starts with the design and performance of a table-top THz spectrometer which has the advantages of ultra-broad bandwidth (one order higher bandwidth compared to a conventional ZnTe sensor) and high electric field strength (>100 kV/cm). Unlike the conventional THz time-domain spectroscopy, the spectrometer integrates a novel THz air-biased-coherent-detection (THz-ABCD) technique and utilizes selected gases as THz emitters and sensors. In comparison with commonly used electro-optic (EO) crystals or photoconductive (PC) dipole antennas, the gases have the benefits of no phonon absorption as existing in EO crystals and no carrier life time limitation as observed in PC dipole antennas. The newly development THz-ABCD spectrometer with a strong THz field strength capability provides a platform for various research topics especially on the nonlinear carrier dynamics of semiconductors. Two mechanisms

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)

Terahertz-wave differential detection based on simultaneous dual-wavelength up-conversion

Directory of Open Access Journals (Sweden)

Yuma Takida

2017-03-01

Full Text Available We report a terahertz (THz-wave differential detection based on simultaneous dual-wavelength up-conversion in a nonlinear optical MgO:LiNbO3 crystal with optical and electronic THz-wave sources. The broadband parametric gain and noncollinear phase-matching of MgO:LiNbO3 provide efficient conversion from superposed THz waves to spatially distributed near-infrared (NIR beams to function as a dispersive THz-wave spectrometer without any additional dispersive element. We show that the μW-level THz waves from two independent sources, a 0.78-THz injection-seeded THz-wave parametric generator (is-TPG and a 1.14-THz resonant tunneling diode (RTD, are simultaneously up-converted to two NIR waves and then detected with two NIR photodetectors. By applying a balanced detection scheme to this dual-frequency detection, we demonstrate THz-wave differential imaging of maltose and polyethylene pellets in the transmission geometry. This dual-wavelength detection is applicable to more than three frequencies and broadband THz-wave radiation for real-time THz-wave spectroscopic detection and imaging.

Frequency-agile THz-wave generation and detection system using nonlinear frequency conversion at room temperature.

Science.gov (United States)

Guo, Ruixiang; Ikar'i, Tomofumi; Zhang, Jun; Minamide, Hiroaki; Ito, Hiromasa

2010-08-02

A surface-emitting THz parametric oscillator is set up to generate a narrow-linewidth, nanosecond pulsed THz-wave radiation. The THz-wave radiation is coherently detected using the frequency up-conversion in MgO: LiNbO(3) crystal. Fast frequency tuning and automatic achromatic THz-wave detection are achieved through a special optical design, including a variable-angle mirror and 1:1 telescope devices in the pump and THz-wave beams. We demonstrate a frequency-agile THz-wave parametric generation and THz-wave coherent detection system. This system can be used as a frequency-domain THz-wave spectrometer operated at room-temperature, and there are a high possible to develop into a real-time two-dimensional THz spectral imaging system.

A BRIGHT IMPULSIVE SOLAR BURST DETECTED AT 30 THz

Energy Technology Data Exchange (ETDEWEB)

Kaufmann, P.; Fernandes, L. O. T.; Kudaka, A. S.; De Souza, R. V.; Valio, A.; Raulin, J.-P. [Center of Radio Astronomy and Astrophysics, Engineering School, Mackenzie Presbyterian University, Sao Paulo, SP (Brazil); White, S. M. [Air Force Research Laboratories, Space Vehicles Directorate, Albuquerque, NM 87117 (United States); Freeland, S. L. [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States); Marcon, R. [' ' Gleb Wataghin' ' Physics Institute, State University of Campinas, Campinas, SP (Brazil); Aballay, J. L.; Fernandez, G.; Godoy, R.; Marun, A.; Gimenez de Castro, C. G. [El Leoncito Astronomical Complex, CONICET, San Juan (Argentina)

2013-05-10

Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised several unsolved controversies. The last unexplored wavelength frontier for solar flares is in the range of submillimeter and infrared wavelengths. Here we report the detection of an intense impulsive burst at 30 THz using a new imaging system. The 30 THz emission exhibited remarkable time coincidence with peaks observed at microwave, mm/submm, visible, EUV, and hard X-ray wavelengths. The emission location coincides with a very weak white-light feature, and is consistent with heating below the temperature minimum in the atmosphere. However, there are problems in attributing the heating to accelerated electrons. The peak 30 THz flux is several times larger than the usual microwave peak near 9 GHz, attributed to non-thermal electrons in the corona. The 30 THz emission could be consistent with an optically thick spectrum increasing from low to high frequencies. It might be part of the same spectral component found at sub-THz frequencies whose nature remains mysterious. Further observations at these wavelengths will provide a new window for flare studies.

Coherent detection of THz-induced sideband emission from excitons in the nonperturbative regime

Science.gov (United States)

Uchida, K.; Otobe, T.; Mochizuki, T.; Kim, C.; Yoshita, M.; Tanaka, K.; Akiyama, H.; Pfeiffer, L. N.; West, K. W.; Hirori, H.

2018-04-01

Strong interaction of a terahertz (THz) wave with excitons induces nonperturbative optical effects such as Rabi splitting and high-order sideband generation. Here, we investigated coherent properties of THz-induced sideband emissions from GaAs/AlGaAs multiquantum wells. With increasing THz electric field, optical susceptibility of the THz-dressed exciton shows a redshift with spectral broadening and extraordinary phase shift. This implies that the field ionization of the 1 s exciton modifies the THz-dressed exciton in the nonperturbative regime.

THz Induced Nonlinear Effects in Materials at Intensities above 26 GW/cm2

Science.gov (United States)

Woldegeorgis, A.; Kurihara, T.; Beleites, B.; Bossert, J.; Grosse, R.; Paulus, G. G.; Ronneberger, F.; Gopal, A.

2018-04-01

Nonlinear refractive index and absorption coefficient are measured for common semiconductor material such as silicon and organic molecule such as lactose in the terahertz (THz) spectral regime extending from 0.1 to 3 THz. Terahertz pulses with field strengths in excess of 4.4 MV/cm have been employed. Transmittance and the transmitted spectrum were measured with Z-scan and single shot noncollinear electro-optic pump-probe techniques. The THz-induced change in the refractive index (Δn) shows frequency-dependence and a maximum change of - 0.128 at 1.37 THz in lactose and up to + 0.169 at 0.15 THz in silicon was measured for a peak incident THz intensity of 26 GW/cm2. Furthermore, the refractive index variation shows a quadratic dependence on the incident THz field, implying the dominance of third-order nonlinearity.

Possible way for increasing the quality of imaging from THz passive device

Science.gov (United States)

Trofimov, Vyacheslav A.; Trofimov, Vladislav V.; Deng, Chao; Zhao, Yuan-meng; Zhang, Cun-lin; Zhang, Xin

2011-11-01

Using the passive THz imaging system developed by the CNU-THz laboratory, we capture the passive THz image of human body with forbidden objects hidden under opaque clothes. We demonstrate the possibility of significant improving the quality of the image. Our approach bases on the application of spatial filters, developed by us for computer treatment of passive THz imaging. The THz imaging system is constructed with accordance to well known passive THz imaging principles and to the THz quasi-optical theory. It contains a scanning mechanism, which has a detector approximately with 1200μm central wavelength, a data acquisition card and a microcomputer. To get a clear imaging of object we apply a sequence of the spatial filters to the image and spectral transforms of the image. The treatment of imaging from the passive THz device is made by computer code. The performance time of treatment of the image, containing about 5000 pixels, is less than 0.1 second. To illustrate the efficiency of developed approach we detect the liquid explosive, knife, pistol and metal plate hidden under opaque clothes. The results obtained demonstrate the high efficiency of our approach for the detection and recognition of the hidden objects and are very promising for the real security application.

THz induced nonlinear absorption in ZnTe

DEFF Research Database (Denmark)

Pedersen, Pernille Klarskov; Jepsen, Peter Uhd

2015-01-01

Absorption spectra of ZnTe during strong-field THz interaction are investigated. Bleaching of the difference phonon modes below the fundamental TO mode is observed when field strengths higher than 4 MV/cm are applied.......Absorption spectra of ZnTe during strong-field THz interaction are investigated. Bleaching of the difference phonon modes below the fundamental TO mode is observed when field strengths higher than 4 MV/cm are applied....

Frequency-dependent absorbance of broadband terahertz wave in dense plasma sheet

Science.gov (United States)

Peng, Yan; Qi, Binbin; Jiang, Xiankai; Zhu, Zhi; Zhao, Hongwei; Zhu, Yiming

2018-05-01

Due to the ability of accurate fingerprinting and low-ionization for different substances, terahertz (THz) technology has a lot of crucial applications in material analysis, information transfer, and safety inspection, etc. However, the spectral characteristic of atmospheric gas and ionized gas has not been widely investigated, which is important for the remote sensing application. Here, in this paper, we investigate the absorbance of broadband terahertz wave in dense plasma sheet generated by femtosecond laser pulses. It was found that as the terahertz wave transmits through the plasma sheet formed, respectively, in carbon dioxide, oxygen, argon and nitrogen, spectrum presents completely different and frequency-dependent absorbance. The reasons for these absorption peaks are related to the molecular polarity, electric charge, intermolecular and intramolecular interactions, and collisional absorption of gas molecules. These results have significant implications for the remote sensing of gas medium.

Refractive Index Sensor Based on a Metal–Insulator–Metal Waveguide Coupled with a Symmetric Structure

Directory of Open Access Journals (Sweden)

Shubin Yan

2017-12-01

Full Text Available In this study, a new refractive index sensor based on a metal–insulator–metal waveguide coupled with a notched ring resonator and stub is designed. The finite element method is used to study the propagation characteristics of the sensor. According to the calculation results, the transmission spectrum exhibits a typical Fano resonance shape. The phenomenon of Fano resonance is caused by the coupling between the broadband spectrum and narrowband spectrum. In the design, the broadband spectrum signal is generated by the stub, while the narrowband spectrum signal is generated by the notched ring resonator. In addition, the structural parameters of the resonators and the structure filled with media of different refractive indices are varied to study the sensing properties. The maximum achieved sensitivity of the sensor reached 1071.4 nm/RIU. The results reveal potential applications of the coupled system in the field of sensors.

Quasioptical devices based on extraordinary transmission at THz

Science.gov (United States)

Beruete, Miguel

2016-04-01

In this work I will present our latest advances in components developed from extraordinary transmission concepts operating at terahertz (THz) frequencies. First, a structure exhibiting two different extraordinary transmission resonances depending on the polarization of the incident wave will be shown. The peaks of transmission appear at approximately 2 and 2.5 THz for vertical and horizontal polarization, respectively, with a transmittance above 60% in both cases. Later on, a meandering line structure able to tune the extraordinary transmission resonance will be discussed. The operation frequency in this case is between 9 and 17 THz. A self-complementary polarizer will be then presented, with a high polarization purity. The fundamentals of this device based on the Babinet's principle will be discussed in depth. Finally, all these structures will be combined together to produce a dual-band Quarter Wave Plate able to convert a linear polarization at the input in a circular polarization at the output at two different bands, 1 and 2.2. THz. Some final words regarding the potential of extraordinary transmission for sensing applications will close the contribution.

Cross-talk dynamics of optical solitons in a broadband Kerr nonlinear system with weak cubic loss

International Nuclear Information System (INIS)

Peleg, Avner; Nguyen, Quan M.; Chung, Yeojin

2010-01-01

We study the dynamics of fast soliton collisions in a Kerr nonlinear optical waveguide with weak cubic loss. We obtain analytic expressions for the amplitude and frequency shifts in a single two-soliton collision and show that the impact of a fast three-soliton collision is given by the sum of the two-soliton interactions. Our analytic predictions are confirmed by numerical simulations with the perturbed nonlinear Schroedinger (NLS) equation. Furthermore, we show that the deterministic collision-induced dynamics of soliton amplitudes in a broadband waveguide system with N frequency channels is described by a Lotka-Volterra model for N competing species. For a two-channel system we find that stable transmission with equal prescribed amplitudes can be achieved by a proper choice of linear amplifier gain. The predictions of the Lotka-Volterra model are confirmed by numerical solution of a perturbed coupled-NLS model.

Wavelength interrogation of fiber Bragg grating sensors using tapered hollow Bragg waveguides.

Science.gov (United States)

Potts, C; Allen, T W; Azar, A; Melnyk, A; Dennison, C R; DeCorby, R G

2014-10-15

We describe an integrated system for wavelength interrogation, which uses tapered hollow Bragg waveguides coupled to an image sensor. Spectral shifts are extracted from the wavelength dependence of the light radiated at mode cutoff. Wavelength shifts as small as ~10  pm were resolved by employing a simple peak detection algorithm. Si/SiO₂-based cladding mirrors enable a potential operational range of several hundred nanometers in the 1550 nm wavelength region for a taper length of ~1  mm. Interrogation of a strain-tuned grating was accomplished using a broadband amplified spontaneous emission (ASE) source, and potential for single-chip interrogation of multiplexed sensor arrays is demonstrated.

Ultracompact and broadband polarization beam splitter based on polarization-dependent critical guiding condition.

Science.gov (United States)

Ying, Zhoufeng; Wang, Guanghui; Zhang, Xuping; Ho, Ho-pui; Huang, Ying

2015-05-01

An ultracompact and broadband polarization beam splitter (PBS) based on the polarization-dependent critical guiding condition of an asymmetrical directional coupler is proposed. The device consists of a pair of silicon waveguides with different height and width. Due to the different cutoff conditions for the TE and TM polarization modes, it is possible to have the TM mode guided in one waveguide while the TE mode is supported in both. Therefore, only the phase-matching condition for the cross-coupling of the TE mode needs to be considered. This approach not only simplifies the design procedures but also significantly improves device performance with smaller total length and larger bandwidth. Finally, regardless of the contribution of S-bend waveguides, our proposed PBS has a coupling region as short as 0.2 μm, which is the shortest reported until now. The simulation result shows that the extinction ratios for the TE and TM polarization are 13.5 and 16.6 dB at their respective output ports, and their insertion losses are 0.29 and 0.13 dB, respectively. Numerical simulations also show that the device offers a very large bandwidth (∼140  nm) with large extinction ratio (>10  dB) and low insertion loss (<1  dB).

Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers.

Science.gov (United States)

Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

2015-06-02

Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers.

THz Generation Using Fluxon Dynamics in High Temperature Superconductors

DEFF Research Database (Denmark)

Pedersen, Niels Falsig; Madsen, S.

2009-01-01

We consider THz emission due to fluxon dynamics in a stack of inductively coupled long Josephson junctions connected electrically to a resonant cavity. By comparing to experiments on Josephson junction parametric amplifiers we consider the role of a negative resistance in connection with THz emis...

Characterization of European Lacquers by Terahertz (THz) Reflectometric Imaging

DEFF Research Database (Denmark)

Dandolo, Corinna Ludovica Koch; Jepsen, Peter Uhd; Christensen, Mads C.

2013-01-01

In this study a European lacquerware replica has been investigated by terahertz (THz) reflectometric imaging. The inspected lacquerware is a wooden panel covered by multiple complex layers of lacquers and plaster. Utilizing pulsed Terahertz Time-Domain Imaging (THz-TDI) in reflection mode, we obs...

Comparative study of broadband electrodynamic properties of single-crystal and thin-film strontium titanate

International Nuclear Information System (INIS)

Findikoglu, A. T.; Jia, Q. X.; Kwon, C.; Reagor, D. W.; Kaduchak, G.; Rasmussen, K. Oe.; Bishop, A. R.

1999-01-01

We have used a coplanar waveguide structure to study broadband electrodynamic properties of single-crystal and thin-film strontium titanate. We have incorporated both time- and frequency-domain measurements to determine small-signal effective refractive index and loss tangent as functions of frequency (up to 4 GHz), dc bias (up to 10 6 V/m), and cryogenic temperature (17 and 60 K). The large-signal impulse response of the devices and the associated phenomenological nonlinear wave equation illustrate how dissipation and nonlinearity combine to produce the overall response in the large-signal regime. (c) 1999 American Institute of Physics

THz Backward-wave oscillators for plasma diagnostic in nuclear fusion

OpenAIRE

Paoloni, Claudio; Yue, Lingna; Tang, Xiaopin; Zhang, Fuzhi; Popovic, Branko; Himes, Logan; Barchfeld, Robert; Gamzina, Diana; Mineo, Mauro; Letizia, Rosa; Luhmann Jr., Neville C.

2015-01-01

Summary form only given. The understanding of plasma turbulence in nuclear fusion is related to the availability of powerful THz sources and the possibility to map wider plasma regions. A novel approach to realize compact THz sources to be implemented in the plasma diagnostic at NSTX experiment (Princeton Plasma Physics Laboratory, USA) is reported.Two novel 0.346 THz Backward-Wave Oscillators (BWOs) have been designed and are presently in the fabrication phase. One BWO is based on the Double...

Inspection of Asian Lacquer Substructures by Terahertz Time-Domain Imaging (THz-TDI)

DEFF Research Database (Denmark)

Dandolo, Corinna Ludovica Koch; Fukunaga, Kaori; Kohzuma, Yoshei

2017-01-01

Lacquering is considered one of the most representative Asian artistic techniques. While the decorative part of lacquerwares is the lacquer itself, their substructures serve as the backbone of the object itself. Very little is known about these hidden substructures. Since lacquerwares are mostly...... by inspecting the substructures of Asian lacquerwares by means of THz time-domain imaging (THz-TDI). Three different kinds of Asian lacquerwares were examined by THz-TDI, and the outcomes have been compared with those obtained by standard X-radiography. THz-TDI provides unique information on lacquerwares...

A European Project on Vacuum Tube Amplifiers for THz Amplification

DEFF Research Database (Denmark)

Paoloni, Claudio; Di Carlo, Aldo; Brunetti, Francesca

2012-01-01

The OPTHER (Optically Driven THz amplifier) project supported by the European Commission within the Seventh Framework Program (FP7) represents the first joint European attempt to realize vacuum electron devices in THz range. The target of the project was to design and realize the first 1 THz vacuum...... tube amplifier. The challenges of the presented task and the innovative solutions adopted established a new level of knowledge in the field. The main aspects of the OPTHER project are described, focusing on challenges and adopted innovative solutions....

Graphene antidot lattice waveguides

DEFF Research Database (Denmark)

Pedersen, Jesper Goor; Gunst, Tue; Markussen, Troels

2012-01-01

We introduce graphene antidot lattice waveguides: nanostructured graphene where a region of pristine graphene is sandwiched between regions of graphene antidot lattices. The band gaps in the surrounding antidot lattices enable localized states to emerge in the central waveguide region. We model...... the waveguides via a position-dependent mass term in the Dirac approximation of graphene and arrive at analytical results for the dispersion relation and spinor eigenstates of the localized waveguide modes. To include atomistic details we also use a tight-binding model, which is in excellent agreement...... with the analytical results. The waveguides resemble graphene nanoribbons, but without the particular properties of ribbons that emerge due to the details of the edge. We show that electrons can be guided through kinks without additional resistance and that transport through the waveguides is robust against...

The OPTHER Project: Progress toward the THz Amplifier

DEFF Research Database (Denmark)

Paoloni, C; Brunetti, F; Di Carlo, A

2011-01-01

This paper describes the status of the OPTHER (OPtically driven TeraHertz AmplifiERs) project and progress toward the THz amplifier realization. This project represents a considerable advancement in the field of high frequency amplification. The design and realization of a THz amplifier within...... this project is a consolidation of efforts at the international level from the leading scientific and industrial European organizations working with vacuum electronics....

Coherent dynamics and terahertz emission in an asymmetric quantum well coupled to broadband infrared pulses

International Nuclear Information System (INIS)

Wu, B H; Cao, J C

2004-01-01

A selected intersubband transition in the asymmetric quantum well is theoretically proposed by using the superposition of two identical time delayed and phase shifted broadband pulses. Three conduction subbands in the semiconductor quantum well structure are optically coupled with the ultrafast infrared pulses. By adjusting the delay between these two pulses, the carriers at ground level can be selectively pumped to one of the upper levels, while the other upper level remains unoccupied. Thus selective transitions in the three level model can be manipulated by optical interference. At the same time, terahertz radiation will be emitted by coherent controlled charge oscillations. The phase and amplitude of THz radiation is found to be sensitive to the optical interference of the coupling pulses

Low-loss rotated porous core hexagonal single-mode fiber in THz regime

DEFF Research Database (Denmark)

Islam, Raonaqul; Hasanuzzaman, G.K.M.; Habib, Selim

2015-01-01

A kind of porous core photonic crystal fiber (PCF) for terahertz (THz) wave propagation is proposed in thispaper. By intentionally rotating the porous core lattice structure, a dispersion of 1.06 ± 0.12 ps/THz/cm ina frequency range of 0.5–1.08 THz is observed. Also, a very low material absorptio...

Optical waveguide demultiplexer

International Nuclear Information System (INIS)

Gajdaj, Yu.O.; Maslyukyivs'kij, R.M.; Sirota, A.V.

2009-01-01

For channels division in fibre-optical networks with wavelength multiplexing, the planar waveguide together with a prism coupler is offered for using. The planar waveguide fulfils a role of a dispersing unit, and prism coupler is the selector of optical channels. The parameters of the planar waveguide which provide maximal space division of adjacent information channels in networks with coarse wavelength multiplexing are calculated

A versatile setup for ultrafast broadband optical spectroscopy of coherent collective modes in strongly correlated quantum systems

Directory of Open Access Journals (Sweden)

Edoardo Baldini

2016-11-01

Full Text Available A femtosecond pump-probe setup is described that is optimised for broadband transient reflectivity experiments on solid samples over a wide temperature range. By combining high temporal resolution and a broad detection window, this apparatus can investigate the interplay between coherent collective modes and high-energy electronic excitations, which is a distinctive characteristic of correlated electron systems. Using a single-shot readout array detector at frame rates of 10 kHz allows resolving coherent oscillations with amplitudes <10−4. We demonstrate its operation on the charge-transfer insulator La2CuO4, revealing coherent phonons with frequencies up to 13 THz and providing access into their Raman matrix elements.

Evaluation of slot-to-slot coupling between dielectric slot waveguides and metal-insulator-metal slot waveguides.

Science.gov (United States)

Kong, Deqing; Tsubokawa, Makoto

2015-07-27

We numerically analyzed the power-coupling characteristics between a high-index-contrast dielectric slot waveguide and a metal-insulator-metal (MIM) plasmonic slot waveguide as functions of structural parameters. Couplings due mainly to the transfer of evanescent components in two waveguides generated high transmission efficiencies of 62% when the slot widths of the two waveguides were the same and 73% when the waveguides were optimized by slightly different widths. The maximum transmission efficiency in the slot-to-slot coupling was about 10% higher than that in the coupling between a normal slab waveguide and an MIM waveguide. Large alignment tolerance of the slot-to-slot coupling was also proved. Moreover, a small gap inserted into the interface between two waveguides effectively enhances the transmission efficiency, as in the case of couplings between a normal slab waveguide and an MIM waveguide. In addition, couplings with very wideband transmissions over a wavelength region of a few hundred nanometers were validated.

Single- and double energy N{sup +} ion irradiated planar optical waveguides in Er: Tungsten–tellurite oxide glass and sillenite type Bismuth Germanate crystals working up to telecommunications wavelengths

Energy Technology Data Exchange (ETDEWEB)

Bányász, I., E-mail: banyasz@sunserv.kfki.hu [Department of Crystal Physics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Zolnai, Z.; Fried, M.; Lohner, T. [Research Institute for Technical Physics and Materials Science, Research Centre for Natural Sciences, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Berneschi, S.; Righini, G.C. [MDF-Lab, “Nello Carrara” Institute of Applied Physics, IFAC-CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); “Enrico Fermi” Center for Study and Research, Piazza del Viminale 2, 00184 Roma (Italy); Pelli, S.; Nunzi-Conti, G. [MDF-Lab, “Nello Carrara” Institute of Applied Physics, IFAC-CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy)

2013-07-15

Ion implantation proved to be a universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er{sup 3+}-doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55 μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Fabrication of channel waveguides in such a material via N{sup +} ion implantation was reported recently. Sillenite type Bismuth Germanate (BGO) crystals are good nonlinear optical materials. Parameters of waveguide fabrication in both materials via implantation of MeV-energy N{sup +} ions were optimized. First single-energy implantations at 3.5 MeV at various fluences were applied. Waveguide operation up to 1.5 μm was observed in both materials. Then double-energy implantations at a fixed upper energy of 3.5 MeV and lower energies between 2.5 and 3.1 MeV were performed to suppress leaky modes by increasing barrier width. Improvement of waveguide characteristics was found by m-line spectroscopy and spectroscopic ellipsometry.

120 Gb/s Multi-Channel THz Wireless Transmission and THz Receiver Performance Analysis

DEFF Research Database (Denmark)

Jia, Shi; Yu, Xianbin; Hu, Hao

2017-01-01

/s. The THz carriers with high-frequency stability and low phase noise are generated based on photonic photomixing of 25-GHz spaced six optical tones and a single optical local oscillator derived from a same optical frequency comb in an ultrabroadband uni-travelling carrier photodiode. The bit...

Multi-Step Deep Reactive Ion Etching Fabrication Process for Silicon-Based Terahertz Components

Science.gov (United States)

Jung-Kubiak, Cecile (Inventor); Reck, Theodore (Inventor); Chattopadhyay, Goutam (Inventor); Perez, Jose Vicente Siles (Inventor); Lin, Robert H. (Inventor); Mehdi, Imran (Inventor); Lee, Choonsup (Inventor); Cooper, Ken B. (Inventor); Peralta, Alejandro (Inventor)

2016-01-01

A multi-step silicon etching process has been developed to fabricate silicon-based terahertz (THz) waveguide components. This technique provides precise dimensional control across multiple etch depths with batch processing capabilities. Nonlinear and passive components such as mixers and multipliers waveguides, hybrids, OMTs and twists have been fabricated and integrated into a small silicon package. This fabrication technique enables a wafer-stacking architecture to provide ultra-compact multi-pixel receiver front-ends in the THz range.

Thermally tunable magnetic metamaterials at THz frequencies

International Nuclear Information System (INIS)

Bui, Son Tung; Nguyen, Van Dung; Bui, Xuan Khuyen; Vu, Dinh Lam; Nguyen, Thanh Tung; Lievens, Peter; Lee, YoungPak

2013-01-01

We investigate theoretically and numerically the tunability of the magnetic property of metamaterial in the THz region via thermal control. One component of the meta-atom is InSb, playing an important role as an alterable metal. When the temperature of the InSb stack increases from 300 to 350 K, the resonance peak of the transmission spectra shows a shift from 0.6 to 0.85 THz accompanied by a stronger magnetic behavior. The S-parameter retrieval method realizes the tunability of the negative permeability achieved in the above heating range. (paper)

Compound semiconductor optical waveguide switch

Science.gov (United States)

Spahn, Olga B.; Sullivan, Charles T.; Garcia, Ernest J.

2003-06-10

An optical waveguide switch is disclosed which is formed from III-V compound semiconductors and which has a moveable optical waveguide with a cantilevered portion that can be bent laterally by an integral electrostatic actuator to route an optical signal (i.e. light) between the moveable optical waveguide and one of a plurality of fixed optical waveguides. A plurality of optical waveguide switches can be formed on a common substrate and interconnected to form an optical switching network.

Terahertz plasmon-induced transparency based on asymmetric dual-disk resonators coupled to a semiconductor InSb waveguide and its biosensor application

Science.gov (United States)

Shahamat, Yadollah; Vahedi, Mohammad

2017-06-01

An ultracompact double eight-shaped plasmonic structure for the realization of plasmon-induced transparency (PIT) in the terahertz (THz) region has been studied. The device consists of a semiconductor-insulator-semiconductor bus waveguide coupled to the dual-disk resonators. Indium antimonide is employed to excite SPP in the THz region. The transmission characteristics of the proposed device are simulated numerically by the finite-difference time-domain method. In addition, a theoretical analysis based on the coupled-mode theory for transmission features is presented and compared with the numerical results. Results are in good agreement. Also, the dependence of PIT frequency characteristics on the radius of the outer disk is discussed in detail. In addition, by removing one of the outer disk resonators, double-PIT peaks can be observed in the transmission spectrum, and the physical mechanism of the appeared peaks is investigated. Finally, an application of the proposed structure for distinguishing different states of DNA molecules is discussed. Results show that the maximum sensitivity with 654 GHz/RIU-1 could be obtained for a single PIT structure. The frequency shifts equal to 37 and 99 GHz could be observed for the denatured and the hybridized DNA states, respectively.

Fundamental Analysis of Extremely Fast Photonic THz Wireless Communication Systems

DEFF Research Database (Denmark)

Yu, Xianbin; Zhang, Xianmin

This talk will review the recent progress on developing THz communication systems for high speed wireless access, and fundamentally analyze the realistic throughput and accessible wireless range of a THz impulse radio communication link by employing a uni-travelling photodiode (UTC-PD) as emitter...

Design and Fabrication of a 1 THz Backward Wave Amplifier

DEFF Research Database (Denmark)

Paoloni, Claudio; Di Carlo, Aldo; Brunetti, Francesca

2011-01-01

, to get a level of output power to enable applications at these frequencies. The OPTHER (Optically driven THz amplifier) project, funded by the European Community, is on the road to realize the first 1 THz vacuum tube amplifier. Technology at the state of the art has been used for the realization...... of the parts with dimensions supporting THz frequencies. A backward wave amplifier configuration is chosen to make the parts realizable. A carbon nanotube cold cathode has been considered for electron generation. A thermionic micro electron gun is designed to test the tube. A novel slow-wave structure (SWS...

Low-loss multimode interference couplers for terahertz waves

Science.gov (United States)

Themistos, Christos; Kalli, Kyriacos; Komodromos, Michael; Markides, Christos; Quadir, Anita; Rahman, B. M. Azizur; Grattan, Kenneth T. V.

2012-04-01

The terahertz (THz) frequency region of the electromagnetic spectrum is located between the traditional microwave spectrum and the optical frequencies, and offers a significant scientific and technological potential in many fields, such as in sensing, in imaging and in spectroscopy. Waveguiding in this intermediate spectral region is a major challenge. Amongst the various THz waveguides suggested, metal-clad plasmonic waveguides and specifically hollow core structures, coated with insulating material are the most promising low-loss waveguides used in both active and passive devices. Optical power splitters are important components in the design of optoelectronic systems and optical communication networks such as Mach-Zehnder Interferometric switches, polarization splitter and polarization scramblers. Several designs for the implementation of the 3dB power splitters have been proposed in the past, such as the directional coupler-based approach, the Y-junction-based devices and the MMI-based approach. In the present paper a novel MMI-based 3dB THz wave splitter is implemented using Gold/polystyrene (PS) coated hollow glass rectangular waveguides. The H-field FEM based full-vector formulation is used here to calculate the complex propagation characteristics of the waveguide structure and the finite element beam propagation method (FE-BPM) and finite difference time domain (FDTD) approach to demonstrate the performance of the proposed 3dB splitter.

Integrated Sources of Polarization Entangled Photon Pair States via Spontaneous Four-Wave Mixing in AlGaAs Waveguides

Science.gov (United States)

Kultavewuti, Pisek

Polarization-entangled photon pair states (PESs) are indispensable in several quantum protocols that should be implemented in an integrated photonic circuit for realizing a practical quantum technology. Preparing such states in integrated waveguides is in fact a challenge due to polarization mode dispersion. Unlike other conventional ways that are plagued with complications in fabrication or in state generation, in this thesis, the scheme based on parallel spontaneous four-wave mixing processes of two polarization waveguide modes is thoroughly studied in theory and experimentation for the polarization entanglement generation. The scheme in fact needs the modal dispersion, contradictory to the general perception, as revealed by a full quantum mechanical framework. The proper modal dispersion balances the effects of temporal walk-off and state factorizability. The study also shows that the popular standard platform such as a silicon-on-insulator wafer is far from suitable to implement the proposed simple generation technique. Proven by the quantum state tomography, the technique produces a highly-entangled state with a maximum concurrence of 0.97 +/- 0:01 from AlGaAs waveguides. In addition, the devices directly generated Bell states with an observed fidelity of 0.92 +/- 0:01 without any post-generation compensating steps. Novel suspended device structures, including their components, are then investigated numerically and experimentally characterized in pursuit of finding the geometry with the optimal dispersion property. The 700 nm x 1100 nm suspended rectangular waveguide is identified as the best geometry with a predicted maximum concurrence of 0.976 and a generation bandwidth of 3.3 THz. The suspended waveguide fabrication procedure adds about 15 dB/cm and 10 dB/cm of propagation loss to the TE and TM mode respectively, on top of the loss in corresponding full-cladding waveguides. Bridges, which structurally support the suspended waveguides, are optimized using

260 Gbit/s photonic-wireless link in the THz band

DEFF Research Database (Denmark)

Pang, X.; Jia, S.; Ozolins, O.

2016-01-01

A single-transmitter/single-receiver THz link (0.3-0.5 THz) with a record net data rate of 260 Gbit/s is experimentally demonstrated. Spectrally efficient multi-channel signal transmission is enabled by a novel frequency-band-allocation scheme with pre-and post- digital equalization....

Terahertz spectroscopy

DEFF Research Database (Denmark)

Jepsen, Peter Uhd

2009-01-01

In this presentation I will review methods for spectroscopy in the THz range, with special emphasis on the practical implementation of the technique known ad THz time-domain spectroscopy (THz-TDS). THz-TDS has revived the old field of far-infrared spectroscopy, and enabled a wealth of new...... activities that promise commercial potential for spectroscopic applications in the THz range. This will be illustrated with examples of spectroscopy of liquids inside their bottles as well as sensitive, quantitative spectroscopy in waveguides....

Adoption of Broadband Services

DEFF Research Database (Denmark)

Falch, Morten

2008-01-01

Broadband is seen as a key infrastructure for developing the information society. For this reason many Governments are actively engaged in stimulating investments in broadband infrastructures and use of broadband services. This chapter compares a wide range of broadband strategies in the most suc....... Many countries have provided active support for stimulating diffusion of broadband and national variants of this type of policies in different countries are important for an explanation of national differences in adoption of broadband....

FTIR Spectroscopy on Basic Materials in THz Region for Compact FEL-Based Imaging

CERN Document Server

Cha, H J; Lee, B C; Park, S H

2005-01-01

We are making experiments on THz(terahertz) imaging using a compact high power FEL (free-electron laser) which is operating as a users facility at KAERI. The wavelength range of output pulses is 100~1200 μm, which corresponds to 0.3~3 THz in the frequency region. We should select the optimum wavelength for the constituents of specimens to realize the imaging based on the THz FEL. A FTIR (Fourier-transform infrared) spectrometer was modified to measure the optical constants of the specimens in THz region. A polyester film of which thickness is 3.7 μm was used as a beam splitter of the spectrometer. In the case of normal incidence, the transmittance of the film was measured to be more than 90%, and the estimated loss by absorption was approximately 2% at the FEL frequency of 3 THz. Several tens of nanometer-thick-silver was coated on the polyester film to balance both transmission and reflection of THz waves in the beam splitter. We investigated FTIR spectroscopy on air, vapor and liquid water...

Tunable broadband unidirectional acoustic transmission based on a waveguide with phononic crystal

Science.gov (United States)

Song, Ailing; Chen, Tianning; Wang, Xiaopeng; Wan, Lele

2016-08-01

In this paper, a tunable broadband unidirectional acoustic transmission (UAT) device composed of a bended tube and a superlattice with square columns is proposed and numerically investigated by using finite element method. The UAT is realized in the proposed UAT device within two wide frequency ranges. And the effectiveness of the UAT device is demonstrated by analyzing the sound pressure distributions when the acoustic waves are incident from different directions. The unidirectional band gaps can be effectively tuned by mechanically rotating the square columns, which is a highlight of this paper. Besides, a bidirectional acoustic isolation (BAI) device is obtained by placing two superlattices in the bended tube, in which the acoustic waves cannot propagate along any directions. The physical mechanisms of the proposed UAT device and BAI device are simply discussed. The proposed models show potential applications in some areas, such as unidirectional sonic barrier or noise insulation.

Rotational spectrum of formaldehyde reinvestigated using a photomixing THz synthesizer

Science.gov (United States)

Eliet, Sophie; Cuisset, Arnaud; Guinet, Mickaël; Hindle, Francis; Mouret, Gaël; Bocquet, Robin; Demaison, Jean

2012-09-01

Approximately 60 pure rotational frequency transitions of formaldehyde in its ground state have been measured with sub-MHz uncertainty in the 0.7-1.8 THz frequency range using a photomixing THz synthesizer locked onto a frequency comb. The frequencies associated with previous submillimeter and infrared data have been included in a fit providing a new set of improved molecular parameters. The assignment of each line was checked using the usual statistical diagnostics. Finally, the ability of the continuous-wave spectrometer coupled to a multipass-cell to measure THz rotational transitions of H2CO in the 31, 41 and 61 vibrational states was demonstrated.

A tunable continuous wave (CW) and short-pulse optical source for THz brain imaging applications

International Nuclear Information System (INIS)

Bakopoulos, P; Karanasiou, I; Zakynthinos, P; Uzunoglu, N; Avramopoulos, H; Pleros, N

2009-01-01

We demonstrate recent advances toward the development of a novel 2D THz imaging system for brain imaging applications both at the macroscopic and at the bimolecular level. A frequency-synthesized THz source based on difference frequency generation between optical wavelengths is presented, utilizing supercontinuum generation in a highly nonlinear optical fiber with subsequent spectral carving by means of a fiber Fabry–Perot filter. Experimental results confirm the successful generation of THz radiation in the range of 0.2–2 THz, verifying the enhanced frequency tunability properties of the proposed system. Finally, the roadmap toward capturing functional brain information by exploiting THz imaging technologies is discussed, outlining the unique advantages offered by THz frequencies and their complementarity with existing brain imaging techniques

Tailoring of Highly Intense THz Radiation Through High Brightness Electron Beams Longitudinal Manipulation

Directory of Open Access Journals (Sweden)

Flavio Giorgianni

2016-02-01

Full Text Available The ultra-short electron beams, produced through the velocity bunching compression technique at the SPARC_LAB test Facility (Frascati, Italy, are used to produce Coherent Transition Radiation in the terahertz (THz range. This paper reports on the main features of this THz source, which have a spectral coverage up to 5 THz, a pulse duration down to 100 fs, and an energy per pulse on the order of tens of μJ. These figures of merits open the possibility to apply this source for nonlinear and THz pump-probe experiments in Solid-State Physics and material science.

InGaAs/InAlAs superlattice detector for THz radiation

CERN Document Server

Schomburg, E; Kratschmer, M; Vollnhals, A; Scheuerer, R; Renk, K F; Ustinov, V; Zhukov, A; Kovsh, A

2002-01-01

We report the use of an InGaAs/InAlAs superlattice for detection of THz radiation pulses generated by a free-electron-laser (FELIX). The detector showed a response corresponding to a reduction of the direct current through the superlattice. The current reduction is attributed to the THz-field induced modulation of Bloch oscillations performed by miniband electrons. The detector response was measured in a frequency range between 4 and 12 THz and showed strong minima at the frequencies of infrared active transverse optic phonons. (10 refs).

Broadband dynamic phase matching of high-order harmonic generation by a high-peak-power soliton pump field in a gas-filled hollow photonic-crystal fiber.

Science.gov (United States)

Serebryannikov, Evgenii E; von der Linde, Dietrich; Zheltikov, Aleksei M

2008-05-01

Hollow-core photonic-crystal fibers are shown to enable dynamically phase-matched high-order harmonic generation by a gigawatt soliton pump field. With a careful design of the waveguide structure and an appropriate choice of input-pulse and gas parameters, a remarkably broadband phase matching can be achieved for a soliton pump field and a large group of optical harmonics in the soft-x-ray-extreme-ultraviolet spectral range.

Mechanisms of realization of THz-waves of nitrogen oxide occurrence physiological effects

Directory of Open Access Journals (Sweden)

Vyacheslav F. Kirichuk

2013-11-01

Full Text Available In this review, there is generalized material of many experimental researches in interaction of THz-waves molecular emission and absorption spectrum (MEAS of nitrogen oxide occurrence with bioobjects. Thrombocytes and experimental animals were used as bioobjects. The experiments let indicate changes caused by THz-waves: at the cellular, tissular, system, organismic levels. There are all data of changes in physiological mechanisms of reglations at all levels: autocrine, paracrine, endocrine and nervous. There is a complex overview of experimental material firstly performed in the article. There had been shown that the effect of THz-waves of the given occurrence is realized by the changed activity of nitroxidergic system. It had been proved that THz-waves of nitrogen oxide occurrence can stimulate nitrogen oxide producing in organs and tissues in condition of its low concentration. Possible mechanisms of antiaggregative effect of the given waves had been described. There had been shown the possibility of regulating of vascular tone and system hemodynamics with the help of the studying these frequencies. The represented data of lipid peroxidation and enzymatic and nonenzymatic components of organism system under the influence of THz-waves of nitrogen oxide occurrence in stress conditions. Besides, there were shown changes of stress-regulating system activity and in concentration of important mediators - catecholamines and glucocorticosteroids. These data let characterize mechanism of realization of THz-waves basic effects. The research had shown the possibility of THz-waves of nitrogen oxide occurrence usage as a method of natural physiological noninvasive regulation of significant organism functions.

CH3D photomixing spectroscopy up to 2.5 THz: New set of rotational and dipole parameters, first THz self-broadening measurements

Science.gov (United States)

Bray, Cédric; Cuisset, Arnaud; Hindle, Francis; Bocquet, Robin; Mouret, Gaël; Drouin, Brian J.

2017-03-01

Several previously unmeasured transitions of 12CH3D have been recorded by a terahertz photomixing continuous-wave spectrometer up to QR(10) branch at 2.5 THz. An improved set of rotational constants has been obtained utilizing a THz frequency metrology based on a frequency comb that achieved an averaged frequency position better than 150 kHz on more than fifty ground-state transitions. A detailed analysis of the measured line intensities was undertaken using the multispectrum fitting program and has resulted in a determination of new dipole moment parameters. Measurements at different pressures of the QR(7) transitions provide the first determination of self-broadening coefficients from pure rotational CH3D lines. The THz rotational measurements are consistent with IR rovibrational data but no significant vibrational dependence of self-broadening coefficient may be observed by comparison.

Tunable narrow band difference frequency THz wave generation in DAST via dual seed PPLN OPG.

Science.gov (United States)

Dolasinski, Brian; Powers, Peter E; Haus, Joseph W; Cooney, Adam

2015-02-09

We report a widely tunable narrowband terahertz (THz) source via difference frequency generation (DFG). A narrowband THz source uses the output of dual seeded periodically poled lithium niobate (PPLN) optical parametric generators (OPG) combined in the nonlinear crystal 4-dimthylamino-N-methyl-4-stilbazolium-tosylate (DAST). We demonstrate a seamlessly tunable THZ output that tunes from 1.5 THz to 27 THz with a minimum bandwidth of 3.1 GHz. The effects of dispersive phase matching, two-photon absorption, and polarization were examined and compared to a power emission model that consisted of the current accepted parameters of DAST.

Silicon microphotonic waveguides

International Nuclear Information System (INIS)

Ta'eed, V.; Steel, M.J.; Grillet, C.; Eggleton, B.; Du, J.; Glasscock, J.; Savvides, N.

2004-01-01

Full text: Silicon microphotonic devices have been drawing increasing attention in the past few years. The high index-difference between silicon and its oxide (Δn = 2) suggests a potential for high-density integration of optical functions on to a photonic chip. Additionally, it has been shown that silicon exhibits strong Raman nonlinearity, a necessary property as light interaction can occur only by means of nonlinearities in the propagation medium. The small dimensions of silicon waveguides require the design of efficient tapers to couple light to them. We have used the beam propagation method (RSoft BeamPROP) to understand the principles and design of an inverse-taper mode-converter as implemented in several recent papers. We report on progress in the design and fabrication of silicon-based waveguides. Preliminary work has been conducted by patterning silicon-on-insulator (SOI) wafers using optical lithography and reactive ion etching. Thus far, only rib waveguides have been designed, as single-mode ridge-waveguides are beyond the capabilities of conventional optical lithography. We have recently moved to electron beam lithography as the higher resolutions permitted will provide the flexibility to begin fabricating sub-micron waveguides

Waveguide harmonic damper for klystron amplifier

International Nuclear Information System (INIS)

Kang, Y.

1998-01-01

A waveguide harmonic damper was designed for removing the harmonic frequency power from the klystron amplifiers of the APS linac. Straight coaxial probe antennas are used in a rectangular waveguide to form a damper. A linear array of the probe antennas is used on a narrow wall of the rectangular waveguide for damping klystron harmonics while decoupling the fundamental frequency in dominent TE 01 mode. The klystron harmonics can exist in the waveguide as waveguide higher-order modes above cutoff. Computer simulations are made to investigate the waveguide harmonic damping characteristics of the damper

Rectangular waveguide-to-coplanar waveguide transitions at U-band using e-plane probe and wire bonding

DEFF Research Database (Denmark)

Dong, Yunfeng; Johansen, Tom Keinicke; Zhurbenko, Vitaliy

2016-01-01

This paper presents rectangular waveguide-to-coplanar waveguide (CPW) transitions at U-band (40–60 GHz) using E-plane probe and wire bonding. The designs of CPWs based on quartz substrate with and without aluminum cover are explained. The single and double layer rectangular waveguide-to-CPW trans......This paper presents rectangular waveguide-to-coplanar waveguide (CPW) transitions at U-band (40–60 GHz) using E-plane probe and wire bonding. The designs of CPWs based on quartz substrate with and without aluminum cover are explained. The single and double layer rectangular waveguide......-to-CPW transitions using E-plane probe and wire bonding are designed. The proposed rectangular waveguide-to-CPW transition using wire bonding can provide 10 GHz bandwidth at U-band and does not require extra CPWs or connections between CPWs and chips. A single layer rectangular waveguide-to-CPW transition using E......-plane probe with aluminum package has been fabricated and measured to validate the proposed transitions. To the authors' best knowledge, this is the first time that a wire bonding is used as a probe for rectangular waveguide-to-CPW transition at U-band....

Omnidirectional optical waveguide

Science.gov (United States)

Bora, Mihail; Bond, Tiziana C.

2016-08-02

In one embodiment, a system includes a scintillator material; a detector coupled to the scintillator material; and an omnidirectional waveguide coupled to the scintillator material, the omnidirectional waveguide comprising: a plurality of first layers comprising one or more materials having a refractive index in a first range; and a plurality of second layers comprising one or more materials having a refractive index in a second range, the second range being lower than the first range, a plurality of interfaces being defined between alternating ones of the first and second layers. In another embodiment, a method includes depositing alternating layers of a material having a relatively high refractive index and a material having a relatively low refractive index on a substrate to form an omnidirectional waveguide; and coupling the omnidirectional waveguide to at least one surface of a scintillator material.

Development of the high-power THz spectroscopy and imaging systems on the basis of an S-band compact electron LINAC

International Nuclear Information System (INIS)

Kuroda, R.; Taira, Y.; Tanaka, M.; Toyokawa, H.; Yamada, K.; Kumaki, M.; Tachibana, M.; Sakaue, K.; Washio, M.

2014-01-01

The high-power terahertz time-domain spectroscopy (THz-TDS) and imaging systems have been developed on the basis of an S-band compact electron linac at AIST. Such high-power THz source is strongly expected for inspection of dangerous materials in the homeland security field. The high-power THz radiations are generated in two methods with the high-brightness ultra-short electron bunch. One is THz coherent synchrotron radiation (THz-CSR) for THz imaging applications. The other is THz coherent transition radiation (THz-CTR) for the THz spectroscopy. The THz-CTR time-domain spectroscopy (TDS) has been constructed with the EO sampling method and demonstrated in freq. range between 0.1-2 THz. The absorption measurements of drug samples have been successfully performed in atmosphere. In this symposium, we will describe details of the THz-CTR-TDS and imaging experiments and a future plan of the THz applications. (author)

High power and spectral purity continuous-wave photonic THz source tunable from 1 to 4.5 THz for nonlinear molecular spectroscopy

Science.gov (United States)

Kiessling, J.; Breunig, I.; Schunemann, P. G.; Buse, K.; Vodopyanov, K. L.

2013-10-01

We report a diffraction-limited photonic terahertz (THz) source with linewidth OP) gallium arsenide (GaAs) via intracavity frequency mixing between the two closely spaced resonating signal and idler waves of an optical parametric oscillator (OPO) operating near λ = 2 μm. The doubly resonant type II OPO is based on a periodically poled lithium niobate (PPLN) pumped by a single-frequency Yb:YAG disc laser at 1030 nm. We take advantage of the enhancement of both optical fields inside a high-finesse OPO cavity: with 10 W of 1030 nm pump, 100 W of intracavity power near 2 μm was attained with GaAs inside cavity. This allows dramatic improvement in terms of generated THz power, as compared to the state-of-the art CW methods. We achieved >25 μW of single-frequency tunable CW THz output power scalable to >1 mW with proper choice of pump laser wavelength.

Investigation of fingerprints for small polar molecules by using a tunable monochromatic THz source

Science.gov (United States)

Sun, Hongqian

Over the past 20 years, considerable efforts have been dedicated to the generation and the application of electromagnetic waves in the Terahertz (THz) regime. Among all of the proposed applications, the THz spectroscopy is probably the most mature and promising one. According to the previous reports, the THz spectroscopy has been extensively applied into many analysis fields, including the investigation of vibrational modes for the crystalline solids, the characterization of electron transport in the condense matters and the identification of explosive materials at a standoff distance. More interestingly, since most gas phase chemicals exhibit unique transition peaks in the THz spectra, one could in principle achieve highly accurate molecular fingerprinting and chemical sensing as well. However, all of the practical THz spectroscopy applications were still greatly hampered by the lack of suitable sources and detectors. In this thesis, a unique approach to measure the THz spectrum is developed based on a novel tunable narrowband source. Unlike the previous THz systems, high power THz pulses were generated by the difference frequency generation processes between two collinearly propagated near infrared laser beams. To tune the output THz signal frequency, one can simply adjust one of the incident beam frequencies. Therefore, based on a convenient wavelength tuning scheme, the transmission spectra can be measured for a series of polar gases with either similar or distinct molecular structures. According to the measured spectra, it is found that the obtained transition frequencies, absorption intensities and molecular constants are all in good agreement with the theoretical results tabulated in the molecular spectroscopic databases, such as the HITRAN database. By further analyzing the transition frequencies, it is also discovered that one can confidently identify each polar molecule and differentiate between various isotopic variants based on their characteristic

The impact of hydration changes in fresh bio-tissue on THz spectroscopic measurements

International Nuclear Information System (INIS)

Png, G M; Ng, B W-H; Mickan, S P; Abbott, D; Choi, J W; Zhang, X-C

2008-01-01

We present a study of how residual hydration in fresh rat tissue samples can vastly alter their extracted terahertz (THz) optical properties and influence their health assessment. Fresh (as opposed to preserved) tissue most closely mimics in vivo conditions, but high water content creates many challenges for tissue handling and THz measurement. Our THz measurements of fresh tissue over time highlight the effect of tissue hydration on tissue texture and dimension, the latter directly influencing the accuracy of calculated optical properties. We then introduce lyophilization (freeze drying) as a viable solution for overcoming hydration and freshness problems. Lyophilization removes large amounts of water while retaining sample freshness. In addition, lyophilized tissue samples are easy to handle and their textures and dimensions do not vary over time, allowing for consistent and stable THz measurements. A comparison of lyophilized and fresh tissue shows for the first time that freeze drying may be one way of overcoming tissue hydration issues while preserving tissue cellular structure. Finally, we compare THz measurements from fresh tissue against necrotic tissue to verify freshness over time. Indeed, THz measurements from fresh and necrotic tissues show marked differences

Low crosstalk Arrayed Waveguide Grating with Cascaded Waveguide Grating Filter

International Nuclear Information System (INIS)

Deng Yang; Liu Yuan; Gao Dingshan

2011-01-01

We propose a highly compact and low crosstalk arrayed waveguide grating (AWG) with cascaded waveguide grating (CWGF). The side lobes of the silicon nanowire AWG, which are normally introduced by fabrication errors, can be effectively suppressed by the CWGF. And the crosstalk can be improved about 15dB.

THz Wireless Transmission Systems Based on Photonic Generation of Highly Pure Beat-Notes

DEFF Research Database (Denmark)

Jia, Shi; Yu, Xianbin; Hu, Hao

2016-01-01

In this paper, a terahertz (THz) wireless communication system at 400 GHz with various modulation formats [on–off keying (OOK), quadrature phase-shift keying (QPSK), 16-quadrature amplitude modulation (16-QAM), and 32-quadrature amplitude modulation (32-QAM)] is experimentally demonstrated based...... noise of photonically generated THz beat-notes when phase correlation of two optical comb tones is damaged due to their path-length difference. In addition, we demonstrate THz wireless transmission of various modulation formats, including OOK, QPSK, 16-QAM, and 32-QAM at beyond 10 Gb/s in such a system......, and the measured bit error rate (BER) performance for all the signals after 0.5 m free-space delivery is below the hard decision forward error correction threshold of 3.8 × 10–3. Furthermore, the influence of THz carrier purity on the system performance is experimentally analyzed with respect to the BER of the THz...

Fabrication and characterization of 8.87 THz schottky barrier mixer diodes for mixer

Science.gov (United States)

Wang, Wenjie; Li, Qian; An, Ning; Tong, Xiaodong; Zeng, Jianping

2018-04-01

In this paper we report on the fabrication and characterization of GaAs-based THz schottky barrier mixer diodes. Considering the analyzed results as well as fabrication cost and complexity, a group of trade-off parameters was determined. Electron-beam lithography and air-bridge technique have been used to obtain schottky diodes with a cut off frequency of 8.87 THz. Equivalent values of series resistance, ideal factor and junction capacitance of 10.2 (1) Ω, 1.14 (0.03) and 1.76(0.03) respectively have been measured for 0.7um diameter anode devices by DC and RF measurements. The schottky barrier diodes fabrication process is fully planar and very suitable for integration in THz frequency multiplier and mixer circuits. THz Schottky barrier diodes based on such technology with 2 μm diameter anodes have been tested at 1.6 THz in a sub-harmonic mixer.

Evanescent fields of laser written waveguides

Science.gov (United States)

Jukić, Dario; Pohl, Thomas; Götte, Jörg B.

2015-03-01

We investigate the evanescent field at the surface of laser written waveguides. The waveguides are written by a direct femtosecond laser writing process into fused silica, which is then sanded down to expose the guiding layer. These waveguides support eigenmodes which have an evanescent field reaching into the vacuum above the waveguide. We study the governing wave equations and present solution for the fundamental eigenmodes of the modified waveguides.

Progress in planar optical waveguides

CERN Document Server

Wang, Xianping; Cao, Zhuangqi

2016-01-01

This book provides a comprehensive description of various slab waveguide structures ranged from graded-index waveguide to symmetrical metal-cladding waveguide. In this book, the transfer Matrix method is developed and applied to analyze the simplest case and the complex generalizations. A novel symmetrical metal-cladding waveguide structure is proposed and systematically investigated for several issues of interest, such as biochemical sensing, Goos-Hänchen shift and the slow light effect, etc. Besides, this book summarizes the authors’ research works on waveguides over the last decade. The readers who are familiar with basic optics theory may find this book easy to read and rather inspiring.

Nanoporous polymer liquid core waveguides

DEFF Research Database (Denmark)

Gopalakrishnan, Nimi; Christiansen, Mads Brøkner; Ndoni, Sokol

2010-01-01

We demonstrate liquid core waveguides defined by UV to enable selective water infiltration in nanoporous polymers, creating an effective refractive index shift Δn=0.13. The mode confinement and propagation loss in these waveguides are presented.......We demonstrate liquid core waveguides defined by UV to enable selective water infiltration in nanoporous polymers, creating an effective refractive index shift Δn=0.13. The mode confinement and propagation loss in these waveguides are presented....

Expanded opportunities of THz passive camera for the detection of concealed objects

Science.gov (United States)

Trofimov, Vyacheslav A.; Trofimov, Vladislav V.; Kuchik, Igor E.

2013-10-01

Among the security problems, the detection of object implanted into either the human body or animal body is the urgent problem. At the present time the main tool for the detection of such object is X-raying only. However, X-ray is the ionized radiation and therefore can not be used often. Other way for the problem solving is passive THz imaging using. In our opinion, using of the passive THz camera may help to detect the object implanted into the human body under certain conditions. The physical reason of such possibility arises from temperature trace on the human skin as a result of the difference in temperature between object and parts of human body. Modern passive THz cameras have not enough resolution in temperature to see this difference. That is why, we use computer processing to enhance the passive THz camera resolution for this application. After computer processing of images captured by passive THz camera TS4, developed by ThruVision Systems Ltd., we may see the pronounced temperature trace on the human body skin from the water, which is drunk by person, or other food eaten by person. Nevertheless, there are many difficulties on the way of full soution of this problem. We illustrate also an improvement of quality of the image captured by comercially available passive THz cameras using computer processing. In some cases, one can fully supress a noise on the image without loss of its quality. Using computer processing of the THz image of objects concealed on the human body, one may improve it many times. Consequently, the instrumental resolution of such device may be increased without any additional engineering efforts.

Experiences with rectangular waveguide

International Nuclear Information System (INIS)

Beltran, J.; Sepulveda, J. J.; Navarro, E. A.

2000-01-01

A simple and didactic experimental arrangement is presented to show wave propagation along a structure with translational symmetry, particularly the rectangular waveguide. Parameters of this waveguide as cutoff frequency, guide wavelength and field distribution of fundamental mode can be measured. For this purpose a large paralelepipedical waveguide structure is designed and built, its dimensions can be varied in order to change its parameters. (Author) 9 refs

New investigation on THz spectra of OH and SH radicals (X∏)

Science.gov (United States)

Martin-Drumel, M. A.; Eliet, S.; Pirali, O.; Guinet, M.; Hindle, F.; Mouret, G.; Cuisset, A.

2012-10-01

Pure rotational transitions of OH and SH radicals have been recorded in the THz spectral range using cw-THz and synchrotron-based FT-FIR techniques. Line lists on these radicals have been completed in the three and two lowest vibrational states for OH and SH, respectively. Furthermore, the hyperfine structure of OH and SH has been observed for the first time using infrared IR FT-spectroscopy, and at frequencies higher than 1 THz, respectively. A combined fit has been made for each of these radicals including v = 0, 1 and 2 for OH and v = 0 and 1 for SH.

Development of a THz spectroscopic imaging system

International Nuclear Information System (INIS)

Usami, M; Iwamoto, T; Fukasawa, R; Tani, M; Watanabe, M; Sakai, K

2002-01-01

We have developed a real-time THz imaging system based on the two-dimensional (2D) electro-optic (EO) sampling technique. Employing the 2D EO-sampling technique, we can obtain THz images using a CCD camera at a video rate of up to 30 frames per second. A spatial resolution of 1.4 mm was achieved. This resolution was reasonably close to the theoretical limit determined by diffraction. We observed not only static objects but also moving ones. To acquire spectroscopic information, time-domain images were collected. By processing these images on a computer, we can obtain spectroscopic images. Spectroscopy for silicon wafers was demonstrated

In vivo THz imaging of human skin: Accounting for occlusion effects.

Science.gov (United States)

Sun, Qiushuo; Parrott, Edward P J; He, Yuezhi; Pickwell-MacPherson, Emma

2018-02-01

In vivo terahertz (THz) imaging of human skin needs to be done in reflection geometry due to the high attenuation of THz light by water in the skin. To aid the measurement procedure, there is typically an imaging window onto which the patient places the area of interest. The window enables better pulse alignment and helps keep the patient correctly positioned during the measurement. In this paper, we demonstrate how the occlusion caused by the skin contact with the imaging window during the measurement affects the THz response. By studying both rapid point measurements and imaging over an area of a human volar forearm, we find that even 5 seconds of occlusion affects the THz response. As the occlusion time increases, the skin surface water content increases, resulting in the reduction of the amplitude of the reflected THz pulse, especially in the first 3 minutes. Furthermore, it was found that the refractive index of the volar forearm increased by 10% to 15% after 20 minutes of occlusion. In this work, we examine and propose a model for the occlusion effects due to the quartz window with a view to compensating for its influence. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Single Channel 106 Gbit/s 16QAM Wireless Transmission in the 0.4 THz Band

DEFF Research Database (Denmark)

Pang, Xiaodan; Jia, Shi; Ozolins, Oskars

2017-01-01

We experimentally demonstrate a single channel 32-GBd 16QAM THz wireless link operating in the 0.4 THz band. Post-FEC net data rate of 106 Gbit/s is successfully achieved without any spatial/frequency multiplexing.......We experimentally demonstrate a single channel 32-GBd 16QAM THz wireless link operating in the 0.4 THz band. Post-FEC net data rate of 106 Gbit/s is successfully achieved without any spatial/frequency multiplexing....

Bismuth telluride topological insulator nanosheet saturable absorbers for q-switched mode-locked Tm:ZBLAN waveguide lasers

Energy Technology Data Exchange (ETDEWEB)

Jiang, Xiantao; Gross, Simon; Withford, Michael J.; Fuerbach, Alexander [Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS) and MQ Photonics Research Centre, Dept. of Physics and Astronomy, Macquarie Univ., NSW (Australia); Zhang, Han; Guo, Zhinan [SZU-NUS Collaborative Innovation Centre for Optoelectronic Science and Technology, Key Lab. of Optoelectronic Devices and Systems of Ministry of Education, College of Optoelectronic Engineering, Shenzhen Univ. (China)

2016-08-15

Nanosheets of bismuth telluride (Bi{sub 2}Te{sub 3}), a topological insulator material that exhibits broadband saturable absorption due to its non-trivial Dirac-cone like energy structure, are utilized to generate short pulses from Tm:ZBLAN waveguide lasers. By depositing multiple layers of a carefully prepared Bi{sub 2}Te{sub 3} solution onto a glass substrate, the modulation depth and the saturation intensity of the fabricated devices can be controlled and optimized. This approach enables the realization of saturable absorbers that feature a modulation depth of 13% and a saturation intensity of 997 kW/cm{sup 2}. For the first time to our knowledge, Q-switched mode-locked operation of a linearly polarized mid-IR ZBLAN waveguide chip laser was realized in an extended cavity configuration using the topological insulator Bi{sub 2}Te{sub 3}. The maximum average output power of the laser is 16.3 mW and the Q-switched and mode-locked repetition rates are 44 kHz and 436 MHz, respectively. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Synthesis of the Thickness Profile of the Waveguide Layer of the Thin Film Generalized Waveguide Luneburg Lens

Directory of Open Access Journals (Sweden)

Ayryan E.A.

2016-01-01

Full Text Available A local variation in the thickness of the waveguide layer of integrated optics waveguide causes a local decrease of phase velocity, and hence bending of rays and of the wave front. The relationship of the waveguide layer thickness profile h (y, z with the distribution of the effective refractive index of the waveguide β (y, z is described in terms of a particular model of waveguide solutions of the Maxwell equations. In the model of comparison waveguides the support of the thickness irregularity of the waveguide layer Δh coincides with the support of inhomogeneity of the effective refractive index Δβ. A more adequate but more cumbersome model of the adiabatic waveguide modes allows them to mismatch supp Δh ⊃ supp Δβ. In this paper, we solve the problem of the Δh reconstruction on the base of given Δβ of the thin film generalized waveguide Luneburg lens in a model of adiabatic waveguide modes. The solution is found in the form of a linear combination of Gaussian exponential functions and in the form of a cubic spline for the cylindrically symmetric Δh (r and in the form of a cubic spline for Δβ (r.

1,3-thiazole as suitable antenna ligand for lanthanide photoluminescence in [LnCl{sub 3}(thz){sub 4}].0.5thz, Ln = Sm, Eu, Gd, Tb, Dy

Energy Technology Data Exchange (ETDEWEB)

Dannenbauer, Nicole; Mueller-Buschbaum, Klaus [Wuerzburg Univ. (Germany). Inst. for Inorganic Chemistry; Kuzmanoski, Ana; Feldmann, Claus [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany). Inst. for Inorganic Chemistry

2014-02-15

The series of luminescent monomeric lanthanide thiazole complexes [LnCl{sub 3}(thz){sub 4}].0.5thz (Ln = Sm, Eu, Gd, Tb, Dy; thz = 1,3-thiazole) has been synthesised and characterised by powder and single-crystal X-ray diffraction, IR and photoluminescence spectroscopy, DTA/TG as well as elemental analysis. The colourless compounds exhibit photoluminescence in the visible region with varying quantum efficiencies up to QY = 48 % for [LnCl{sub 3}(thz){sub 4}].0.5thz. Both, the lanthanide ions as well as the thiazole ligand contribute to the luminescence. Excitation can be achieved via intra-4f transitions and by exciting the ligand, emission is observed mainly from the lanthanide ions again by 4f transitions. Thiazole can transfer energy to the lanthanide ions, which further feeds the lanthanide emission by an efficient antenna effect even at room temperature. The lanthanide ions show pentagonal-bipyramidal coordination by three chloride anions and four N atoms of 1,3-thiazole, which leads to a strong {sup 5}D{sub 0} → {sup 7}F{sub 4} transition for europium. Significant differences arise as compared to thiophene complexes because no sulphur atom is involved in the metal coordination, as the thiazole ligand is solely coordinated via its nitrogen function. (orig.)

Experiments and Computational Theory for Electrical Breakdown in Critical Components: THz Imaging of Electronic Plasmas.

Energy Technology Data Exchange (ETDEWEB)

Zutavern, Fred J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hjalmarson, Harold P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bigman, Verle Howard [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Gallegos, Richard Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2016-11-01

This report describes the development of ultra-short pulse laser (USPL) induced terahertz (THz) radiation to image electronic plasmas during electrical breakdown. The technique uses three pulses from two USPLs to (1) trigger the breakdown, (2) create a 2 picosecond (ps, 10 -12 s), THz pulse to illuminate the breakdown, and (3) record the THz image of the breakdown. During this three year internal research program, sub-picosecond jitter timing for the lasers, THz generation, high bandwidth (BW) diagnostics, and THz image acquisition was demonstrated. High intensity THz radiation was optically-induced in a pulse-charged gallium arsenide photoconductive switch. The radiation was collected, transported, concentrated, and co-propagated through an electro-optic crystal with an 800 nm USPL pulse whose polarization was rotated due to the spatially varying electric field of the THz image. The polarization modulated USPL pulse was then passed through a polarizer and the resulting spatially varying intensity was detected in a high resolution digital camera. Single shot images had a signal to noise of %7E3:1. Signal to noise was improved to %7E30:1 with several experimental techniques and by averaging the THz images from %7E4000 laser pulses internally and externally with the camera and the acquisition system (40 pulses per readout). THz shadows of metallic films and objects were also recorded with this system to demonstrate free-carrier absorption of the THz radiation and improve image contrast and resolution. These 2 ps THz pulses were created and resolved with 100 femtosecond (fs, 10 -15 s) long USPL pulses. Thus this technology has the capability to time-resolve extremely fast repetitive or single shot phenomena, such as those that occur during the initiation of electrical breakdown. The goal of imaging electrical breakdown was not reached during this three year project. However, plans to achieve this goal as part of a follow-on project are described in this document

High Resolution Spectroscopy Using a Tunable Thz Synthesizer Based on Photomixing

Science.gov (United States)

Cuisset, Arnaud; Hindle, Francis; Mouret, Gael; Eliet, Sophie; Guinet, Mickael; Bocquet, Robin

2011-06-01

Optical heterodyning, also know as photomixing is an attractive solution as a single device able to cover the entire frequency range from 300 GHz to 3 THz. As the THz frequency is extracted from the difference frequency of two lasers, the accuracy with which the generated frequency is known is directly determined by the frequency accuracy of the lasers. In order to fully characterize the spectral fingerprint of a given molecule an accuracy approximately one order of magnitude finer than the Doppler linewidth is required, around 100 kHz for smaller polar compounds. To generate accurate cw-THz the frequency spacing of the modes of a Frequency Comb (FC) has been employed to constrain the emission frequency of a photomixing source.footnote{G. Mouret, F. Hindle, A. Cuisset, C. Yang, R. Bocquet, M. Lours, D. Rovera, Opt. Express, 2009, 17: 22031.} Two phase locked loops are implemented coherently locking the two cw-lasers (CW1 and CW2) to different modes of the FC. Although this solution allows accurate generation of narrowband THz the continuous tuning of the frequency presents some obstacles. To overcome these difficulties a system architecture with a third cw-laser (CW3) phase locked to CW2 has been implemented. The beatnote between CW2 and CW3 is free from the FC modes therefore the PLL frequency can be freely scanned over its entire operating range, in our case around 200 MHz. The most of polar compounds may be studied at high resolution in the THz domain with this synthesizer. Three different examples of THz analysis with atmospherical and astrophysical interests will be presented: The ground and vibrationnally excited states of H_2CO revisited in the 0.5-2 THz frequency region The rotational dependences of the broadening coefficients of CH_3Cl studied at high J and K values The molecular discrimination of a complex mixture containing methanol and ethanol. F. Hindle, A. Cuisset, G. Mouret, R. Bocquet Comptes Rendus Physique, 2008, 9: 262-275.

Analysis and design of tunable wideband microwave photonics phase shifter based on Fabry-Perot cavity and Bragg mirrors in silicon-on-insulator waveguide.

Science.gov (United States)

Qu, Pengfei; Zhou, Jingran; Chen, Weiyou; Li, Fumin; Li, Haibin; Liu, Caixia; Ruan, Shengping; Dong, Wei

2010-04-20

We designed a microwave (MW) photonics phase shifter, consisting of a Fabry-Perot filter, a phase modulation region (PMR), and distributed Bragg reflectors, in a silicon-on-insulator rib waveguide. The thermo-optics effect was employed to tune the PMR. It was theoretically demonstrated that the linear MW phase shift of 0-2pi could be achieved by a refractive index variation of 0-9.68x10(-3) in an ultrawideband (about 38?GHz-1.9?THz), and the corresponding tuning resolution was about 6.92 degrees / degrees C. The device had a very compact size. It could be easily integrated in silicon optoelectronic chips and expected to be widely used in the high-frequency MW photonics field.

Light-emitting waveguide-plasmon polaritions

NARCIS (Netherlands)

Rodriguez, S.R.K.; Murai, S.; Verschuuren, M.A.; Gómez Rivas, J.

2012-01-01

We demonstrate the generation of light in an optical waveguide strongly coupled to a periodic array of metallic nanoantennas. This coupling gives rise to hybrid waveguide-plasmon polaritons (WPPs), which undergo a transmutation from plasmon to waveguide mode and vice versa as the eigenfrequency

Study on guided-mode resonance characteristic of multilayer dielectric grating with broadband and wide using-angle

International Nuclear Information System (INIS)

Jian-Peng, Wang; Yun-Xia, Jin; Jian-Yong, Ma; Jian-Da, Shao; Zheng-Xiu, Fan

2010-01-01

Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resonance is very important. In this paper the characteristics of guided-mode resonance in multilayer dielectric grating are studied with the aim of better understanding the physical process of guided-mode resonance and designing a broadband multilayer dielectric grating with no guided-mode resonance. By employing waveguide theory, all guided-wave modes appearing in multilayer dielectric grating are found, and the incident conditions, separately, corresponding to each guided-wave mode are also obtained. The electric field enhancement in multilayer dielectric grating is shown obviously. Furthermore, from the detailed analyses on the guided-mode resonance conditions, it is found that the reduction of the grating period would effectively avoid the appearing of guided-mode resonance. And the expressions for calculating maximum periods, which ensure that no guided-mode resonance occurs in the requiring broad angle or wavelength range, are first reported. The above results calculated by waveguide theory and Fourier mode method are compared with each other, and they are coincident completely. Moreover, the method that relies on waveguide theory is more helpful for understanding the guided-mode resonance excited process and analyzing how each parameter affects the characteristic of guided-mode resonance. Therefore, the effects of multilayer dielectric grating parameters, such as period, fill factor, thickness of grating layer, et al., on the guided-mode resonance characteristic are discussed in detail based on waveguide theory, and some meaningful results are obtained. (classical areas of phenomenology)

Nanoscale waveguiding methods

Directory of Open Access Journals (Sweden)

Wang Chia-Jean

2007-01-01

Full Text Available AbstractWhile 32 nm lithography technology is on the horizon for integrated circuit (IC fabrication, matching the pace for miniaturization with optics has been hampered by the diffraction limit. However, development of nanoscale components and guiding methods is burgeoning through advances in fabrication techniques and materials processing. As waveguiding presents the fundamental issue and cornerstone for ultra-high density photonic ICs, we examine the current state of methods in the field. Namely, plasmonic, metal slot and negative dielectric based waveguides as well as a few sub-micrometer techniques such as nanoribbons, high-index contrast and photonic crystals waveguides are investigated in terms of construction, transmission, and limitations. Furthermore, we discuss in detail quantum dot (QD arrays as a gain-enabled and flexible means to transmit energy through straight paths and sharp bends. Modeling, fabrication and test results are provided and show that the QD waveguide may be effective as an alternate means to transfer light on sub-diffraction dimensions.

Optical Slot-Waveguide Based Biochemical Sensors

Directory of Open Access Journals (Sweden)

Carlos Angulo Barrios

2009-06-01

Full Text Available Slot-waveguides allow light to be guided and strongly confined inside a nanometer-scale region of low refractive index. Thus stronger light-analyte interaction can be obtained as compared to that achievable by a conventional waveguide, in which the propagating beam is confined to the high-refractive-index core of the waveguide. In addition, slot-waveguides can be fabricated by employing CMOS compatible materials and technology, enabling miniaturization, integration with electronic, photonic and fluidic components in a chip, and mass production. These advantages have made the use of slot-waveguides for highly sensitive biochemical optical integrated sensors an emerging field. In this paper, recent achievements in slot-waveguide based biochemical sensing will be reviewed. These include slot-waveguide ring resonator based refractometric label-free biosensors, label-based optical sensing, and nano-opto-mechanical sensors.

Compact and broadband directional coupling and demultiplexing in dielectric-loaded surface plasmon polariton waveguides based on the multimode interference effect

DEFF Research Database (Denmark)

Zhu, Zhihong; García Ortíz, César Eduardo; Han, Zhanghua

2013-01-01

We theoretically, numerically, and experimentally demonstrate that a directional coupling function can be realized with a wide bandwidth (greater than 200 nm) in dielectric-loaded surface plasmon polariton waveguides based on the multimode interference effect. The functional size of the structure...

Optimization And Single-Shot Characterization Of Ultrashort Thz Pulses From A Laser Wakefield Accelerator

International Nuclear Information System (INIS)

Plateau, G.R.; Matlis, N.H.; van Tilborg, J.; Geddes, C.G.R.; Toth, Cs.; Schroeder, C.B.; Leemans, W.P.

2009-01-01

We present spatiotemporal characterization of μJ-class ultrashort THz pulses generated from a laser wakefield accelerator (LWFA). Accelerated electrons, resulting from the interaction of a high-intensity laser pulse with a plasma, emit high-intensity THz pulses as coherent transition radiation. Such high peak-power THz pulses, suitable for high-field (MV/cm) pump-probe experiments, also provide a non-invasive bunch-length diagnostic and thus feedback for the accelerator. The characterization of the THz pulses includes energy measurement using a Golay cell, 2D sign-resolved electro-optic measurement and single-shot spatiotemporal electric-field distribution retrieval using a new technique, coined temporal electric-field cross-Correlation (TEX). All three techniques corroborate THz pulses of ∼ 5 μJ, with peak fields of 100's of kV/cm and ∼ 0.4 ps rms duration.

3D THz hyperspectrum applied in security check-in

Science.gov (United States)

Damian, V.; Logofǎtu, P. C.; Vasile, T.

2016-12-01

We developed a measuring technology using a TDS-THz system to construct hyperspectral images of some objects, including hazardous materials. "T-rays" (the THz spectral domain of the light) have a growing importance in security and imagistic domain. Due to their property of penetrating through dielectric objects, and using non-ionizing radiations, the THz systems have become a standard for "hot-places" (airports, train stations etc.). The hyperspectral images are 3D images having 2D spatial dimension and one spectral dimension. In this way, we obtain simultaneously information about the form of the object and its molecular composition. For discriminating between substances, we must first build a database of spectra for hazardous and dangerous substances. We experiment our system on some items (among them a firecracker, a cigarette and a metal collar) and we tried to discriminate between them using the database of spectra.

Reverse-symmetry waveguides: Theory and fabrication

DEFF Research Database (Denmark)

Horvath, R.; Lindvold, Lars René; Larsen, N.B.

2002-01-01

We present an extensive theoretical analysis of reverse-symmetry waveguides with special focus on their potential application as sensor components in aqueous media and demonstrate a novel method for fabrication of such waveguides. The principle of reverse symmetry is based on making the refractive...... index of the waveguide substrate less than the refractive index of the medium covering the waveguiding film (n(water) = 1.33). This is opposed to the conventional waveguide geometry, where the substrate is usually glass or polymers with refractive indices of approximate to1.5. The reverse configuration...... are combined with air-grooved polymer supports to form freestanding single-material polymer waveguides of reverse symmetry capable of guiding light....

Electroporation-Induced Cell Modifications Detected with THz Time-Domain Spectroscopy

Science.gov (United States)

Romeo, Stefania; Vernier, P. Thomas; Zeni, Olga

2018-04-01

Electroporation (electropermeabilization) increases the electrical conductivity of biological cell membranes and lowers transport barriers for normally impermeant materials. Molecular simulations suggest that electroporation begins with the reorganization of water and lipid head group dipoles in the phospholipid bilayer interface, driven by an externally applied electric field, and the evolution of the resulting defects into water-filled, lipid pores. The interior of the electroporated membrane thus contains water, which should provide a signature for detection of the electropermeabilized state. In this feasibility study, we use THz time-domain spectroscopy, a powerful tool for investigating biomolecular systems and their interactions with water, to detect electroporation in human cells subjected to permeabilizing pulsed electric fields (PEFs). The time-domain response of electroporated human monocytes was acquired with a commercial THz, time-domain spectrometer. For each sample, frequency spectra were calculated, and the absorption coefficient and refractive index were extracted in the frequency range between 0.2 and 1.5 THz. This analysis reveals a higher absorption of THz radiation by PEF-exposed cells, with respect to sham-exposed ones, consistent with the intrusion of water into the cell through the permeabilized membrane that is presumed to be associated with electroporation.

Theoretical and experimental investigations of efficient light coupling with spatially varied all dielectric striped waveguides

Science.gov (United States)

Yilmaz, Y. A.; Tandogan, S. E.; Hayran, Z.; Giden, I. H.; Turduev, M.; Kurt, H.

2017-07-01

Integrated photonic systems require efficient, compact, and broadband solutions for strong light coupling into and out of optical waveguides. The present work investigates an efficient optical power transferring the problem between optical waveguides having different widths of in/out terminals. We propose a considerably practical and feasible concept to implement and design an optical coupler by introducing gradually index modulation to the coupler section. The index profile of the coupler section is modulated with a Gaussian function by the help of striped waveguides. The effective medium theory is used to replace the original spatially varying index profile with dielectric stripes of a finite length/width having a constant effective refractive index. 2D and 3D finite-difference time-domain analyzes are utilized to investigate the sampling effect of the designed optical coupler and to determine the parameters that play a crucial role in enhancing the optical power transfer performance. Comparing the coupling performance of conventional benchmark adiabatic and butt couplers with the designed striped waveguide coupler, the corresponding coupling efficiency increases from approximately 30% to 95% over a wide frequency interval. In addition, to realize the realistic optical coupler appropriate to integrated photonic applications, the proposed structure is numerically designed on a silicon-on-insulator wafer. The implemented SOI platform based optical coupler operates in the telecom wavelength regime (λ = 1.55 μm), and the dimensions of the striped coupler are kept as 9.77 μm (along the transverse to propagation direction) and 7.69 μm (along the propagation direction) where the unit distance is fixed to be 465 nm. Finally, to demonstrate the operating design principle, the microwave experiments are conducted and the spot size conversion ratio as high as 7.1:1 is measured, whereas a coupling efficiency over 60% in the frequency range of 5.0-16.0 GHz has been also

Anisotropic and nonlinear optical waveguides

CERN Document Server

Someda, CG

1992-01-01

Dielectric optical waveguides have been investigated for more than two decades. In the last ten years they have had the unique position of being simultaneously the backbone of a very practical and fully developed technology, as well as an extremely exciting area of basic, forefront research. Existing waveguides can be divided into two sets: one consisting of waveguides which are already in practical use, and the second of those which are still at the laboratory stage of their evolution. This book is divided into two separate parts: the first dealing with anisotropic waveguides, an

DOE-NSF-NIH Workshop on Opportunities in THz Science, February 12-14, 2004

Energy Technology Data Exchange (ETDEWEB)

Sherwin, M.A.; Bucksbaum, P.H.; Schmuttenmaer, C. A.; Allen, J.; Biedron, S.; Carr, L.; Chamberlain, M.; Crowe, T.; DeLucia, F.; Hu, Q.; Jones, B.; Noordham, B.; Norris, T.; Orenstein, J.; Unterrainer, K.; Van der Meer, L.; Wilke, I.; Williams, G.; Zhang, X.-C.; Cheville, A.; Markelz, A.; Parks, B.; Plancken, P.; Shan, J.; Austin, B.; Basov, D.; Citrin, D.; Grundfest, W.; Heinz, T.; Kono, J.; Mittleman, D.; Siegel, P.; Taylor, T.; Jones, B.; Markelz, A.; Martin, M.; Nelson, K.; Smith, T.; Williams, G.; Allen, M.; Averitt, R.; Brunel, L.; Heilweil, T.; Heyman, J.; Jepsen, P.; Kaind, R.; Leemans, W.; Mihaly, L.; Rangan, C.; Tom, H.; Wallace, V.; Zimdars, D.

2004-02-14

This is the report of the Workshop on Opportunities in THz Science, held on February 12-14, 2004 in Arlington, VA. This workshop brought together researchers who use or produce THz radiation for physics, chemistry, biology, medicine, and materials science to discuss new research opportunities and common resource needs. The charge from the sponsors of the workshop was to focus on basic science questions within these disciplines that have and can be answered using THz radiation.

Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction

Energy Technology Data Exchange (ETDEWEB)

Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H. [Department of Physics and Astronomy, UCLA, Los Angeles California, 90095 (United States)

2012-12-21

A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.

Longitudinal phase space manipulation of an ultrashort electron beam via THz IFEL interaction

International Nuclear Information System (INIS)

Moody, J. T.; Li, R. K.; Musumeci, P.; Scoby, C. M.; To, H.

2012-01-01

A scheme where a laser locked THz source is used to manipulate the longitudinal phase space of an ultrashort electron beam using an IFEL interaction is investigated. The efficiency of THz source based on the pulse front tilt optical rectification scheme is increased by cryogenic cooling to achieve sufficient THz power for compression and synchronization. Start-to-end simulations describing the evolution of the beam from the cathode to the compression point after the undulator are presented.

Complete achromatic and robustness electro-optic switch between two integrated optical waveguides

Science.gov (United States)

Huang, Wei; Kyoseva, Elica

2018-01-01

In this paper, we present a novel design of electro-optic modulator and optical switching device, based on current integrated optics technique. The advantages of our optical switching device are broadband of input light wavelength, robustness against varying device length and operation voltages, with reference to previous design. Conforming to our results of previous paper [Huang et al, phys. lett. a, 90, 053837], the coupling of the waveguides has a hyperbolic-secant shape. while detuning has a sign flip at maximum coupling, we called it as with a sign flip of phase mismatch model. The a sign flip of phase mismatch model can produce complete robust population transfer. In this paper, we enhance this device to switch light intensity controllable, by tuning external electric field based on electro-optic effect.

Design of a 300 GHz Broadband TWT Coupler and RF-Structure

CERN Document Server

Krawczyk, F L

2004-01-01

Recent LANL activities in millimeter wave structures focus on 94 and 300 GHz structures. They aim at power generation from low power (100–2000 W) with a round electron beam (120 kV, 0.1–1.0 A) to high power (2–100 kW) with a sheet beam structure (120 kV, 20 A). Applications cover basic research, radar and secure communications and remote sensing of biological and chemical agents. In this presentation the design and cold-test measurements of a 300 GHz RF-structure with a broadband (>6% bandwidth) power coupler are presented. The design choice of two input/output waveguides, a special coupling region and the structure parameters themselves are presented. As a benchmark also a scaled up version at 10 GHz was designed and measured. These results will also be presented.

Inspection of Asian Lacquer Substructures by Terahertz Time-Domain Imaging (THz-TDI)

Science.gov (United States)

Dandolo, Corinna Ludovica Koch; Fukunaga, Kaori; Kohzuma, Yoshei; Kiriyama, Kyoko; Matsuda, Kazutaka; Jepsen, Peter Uhd

2017-04-01

Lacquering is considered one of the most representative Asian artistic techniques. While the decorative part of lacquerwares is the lacquer itself, their substructures serve as the backbone of the object itself. Very little is known about these hidden substructures. Since lacquerwares are mostly composed of organic materials, such as urushi, wood, carbon black, and fabrics which are very X-ray transparent, standard X-ray radiography has some problems in achieving clear X-ray radiographic images. Therefore, we wanted to contribute to the understanding of the lacquer manufacturing technique by inspecting the substructures of Asian lacquerwares by means of THz time-domain imaging (THz-TDI). Three different kinds of Asian lacquerwares were examined by THz-TDI, and the outcomes have been compared with those obtained by standard X-radiography. THz-TDI provides unique information on lacquerwares substructures, aiding in the comprehension of the manufacturing technology yielding to these precious artefacts.

Identification of explosives and drugs and inspection of material defects with THz radiation

Science.gov (United States)

Zhang, Cunlin; Mu, Kaijun; Jiang, Xue; Jiao, Yueying; Zhang, Liangliang; Zhou, Qingli; Zhang, Yan; Shen, Jingling; Zhao, Guoshong; Zhang, X.-C.

2008-03-01

We report the sensing of explosive materials and illicit drugs by using terahertz time-domain spectroscopy (THz-TDS) and imaging. Several explosive materials, such as γ-HNIW, RDX, 2,4-DNT, TNT, Nitro-aniline, and illicit drugs, such as methamphetamine (MA) etc were researched here. Non-destructive testing, as one of the major applications of THz imaging, can be applied to an area of critical need: the testing of aerospace materials. Composite materials such as carbon fiber are widely used in this industry. The nature of their use requires technologies that are able to differentiate between safe and unsafe materials, due to either manufacturing tolerance or damage acquired while in use. In this paper, we discuss the applicability of terahertz (THz) imaging systems to this purpose, focusing on graphite fiber composite materials, carbon silicon composite materials and so on. We applied THz imaging technology to evaluate the fire damage to a variety of carbon fiber composite samples. Major carbon fiber materials have polarization-dependent reflectivity in THz frequency range, and we show how the polarization dependence changes versus the burned damage level. Additionally, time domain information acquired through a THz time-domain spectroscopy (TDS) system provides further information with which to characterize the damage. We also detect fuel tank insulation foam panel defects with pulse and continuous-wave (CW) terahertz system.

High peak power THz source for ultrafast electron diffraction

Directory of Open Access Journals (Sweden)

Shengguang Liu

2018-01-01

Full Text Available Terahertz (THz science and technology have already become the research highlight at present. In this paper, we put forward a device setup to carry out ultrafast fundamental research. A photocathode RF gun generates electron bunches with ∼MeV energy, ∼ps bunch width and about 25pC charge. The electron bunches inject the designed wiggler, the coherent radiation at THz spectrum emits from these bunches and increases rapidly until the saturation at ∼MW within a short wiggler. THz pulses can be used as pump to stimulate an ultra-short excitation in some kind of sample. Those electron bunches out of wiggler can be handled into bunches with ∼1pC change, small beam spot and energy spread to be probe. Because the pump and probe comes from the same electron source, synchronization between pump and probe is inherent. The whole facility can be compacted on a tabletop.

Mechanical detection of electron spin resonance beyond 1 THz

International Nuclear Information System (INIS)

Takahashi, Hideyuki; Ohmichi, Eiji; Ohta, Hitoshi

2015-01-01

We report the cantilever detection of electron spin resonance (ESR) in the terahertz (THz) region. This technique mechanically detects ESR as a change in magnetic torque that acts on the cantilever. The ESR absorption of a tiny single crystal of Co Tutton salt, Co(NH 4 ) 2 (SO 4 ) 2 ⋅6H 2 O, was observed in frequencies of up to 1.1 THz using a backward travelling wave oscillator as a THz-wave source. This is the highest frequency of mechanical detection of ESR till date. The spectral resolution was evaluated with the ratio of the peak separation to the sum of the half-width at half maximum of two absorption peaks. The highest resolution value of 8.59 ± 0.53 was achieved at 685 GHz, while 2.47 ± 0.01 at 80 GHz. This technique will not only broaden the scope of ESR spectroscopy application but also lead to high-spectral-resolution ESR imaging

Design and Characterization of 1.8-3.2 THz Schottky-based Harmonic Mixers

OpenAIRE

Bulcha, BT; Hesler, JL; Drakinskiy, V; Stake, J; Valavanis, A; Dean, P; Li, LH; Barker, NS

2016-01-01

A room-temperature Schottky diode-based WM-86 (WR-0.34) harmonic mixer was developed to build high-resolution spectrometers, and multi-pixel receivers in the THz region for applications such as radio astronomy, plasma diagnostics, and remote sensing. The mixer consists of a quartz-based Local Oscillator (LO), Intermediate-Frequency (IF) circuits, and a GaAs-based beam-lead THz circuit with an integrated diode. Measurements of the harmonic mixer were performed using a 2 THz solid-state source ...

High-power beam-based coherently enhanced THz radiation source

Directory of Open Access Journals (Sweden)

Yuelin Li (李跃林

2008-08-01

Full Text Available We propose a compact Smith-Purcell radiation device that can potentially generate high average power THz radiation with high conversion efficiency. The source is based on a train of short electron bunches from an rf photoemission gun at an energy of a few MeV. Particle tracking simulation and analysis show that, with a beam current of 1 mA, it is feasible to generate hundreds of watts of narrow-band THz radiation at a repetition rate of 1 MHz.

THz field engineering in two-color femtosecond filaments using chirped and delayed laser pulses

Science.gov (United States)

Nguyen, A.; González de Alaiza Martínez, P.; Thiele, I.; Skupin, S.; Bergé, L.

2018-03-01

We numerically study the influence of chirping and delaying several ionizing two-color light pulses in order to engineer terahertz (THz) wave generation in air. By means of comprehensive 3D simulations, it is shown that two chirped pulses can increase the THz yield when they are separated by a suitable time delay for the same laser energy in focused propagation geometry. To interpret these results, the local current theory is revisited and we propose an easy, accessible all-optical criterion that predicts the laser-to-THz conversion efficiencies given any input laser spectrum. In the filamentation regime, numerical simulations display evidence that a chirped pulse is able to produce more THz radiation due to propagation effects, which maintain the two colors of the laser field more efficiently coupled over long distances. A large delay between two pulses promotes multi-peaked THz spectra as well as conversion efficiencies above 10‑4.

Active Photonic Crystal Waveguides

DEFF Research Database (Denmark)

Ek, Sara

This thesis deals with the fabrication and characterization of active photonic crystal waveguides, realized in III-V semiconductor material with embedded active layers. The platform offering active photonic crystal waveguides has many potential applications. One of these is a compact photonic...... due to photonic crystal dispersion. The observations are explained by the enhancement of net gain by light slow down. Another application based on active photonic crystal waveguides is micro lasers. Measurements on quantum dot micro laser cavities with different mirror configurations and photonic...

Transmission of reactive pulsed laser deposited VO{sub 2} films in the THz domain

Energy Technology Data Exchange (ETDEWEB)

Émond, Nicolas; Hendaoui, Ali; Ibrahim, Akram; Al-Naib, Ibraheem; Ozaki, Tsuneyuki; Chaker, Mohamed, E-mail: chaker@emt.inrs.ca

2016-08-30

Highlights: • Synthesis of vanadium dioxide (VO{sub 2}) thin films as a function of oxygen pressure (2–25 mTorr) using Reactive Pulsed Laser Deposition (RPLD). • Characterization of RPLD-grown VO{sub 2} thin films in the THz frequency range. • THz switches and/or sensors require VO{sub 2} films deposited at low oxygen pressure (i.e. low transition temperature, large amplitude contrast of THz transmission, narrow hysteresis width). • THz optical memory applications require VO{sub 2} films deposited at high oxygen pressure (broad hysteresis width). - Abstract: This work reports on the characteristics of the insulator-to-metal transition (IMT) of reactive pulsed laser deposited vanadium dioxide (VO{sub 2}) films in the terahertz (THz) frequency range, namely the transition temperature T{sub IMT}, the amplitude contrast of the THz transmission over the IMT ΔA, the transition sharpness ΔT and the hysteresis width ΔH. XRD analysis shows the sole formation of VO{sub 2} monoclinic structure with an enhancement of (011) preferential orientation when varying the O{sub 2} pressure (P{sub O2}) during the deposition process from 2 to 25 mTorr. THz transmission measurements as a function of temperature reveal that VO{sub 2} films obtained at low P{sub O2} exhibit low T{sub IMT}, large ΔA, and narrow ΔH. Increasing P{sub O2} results in VO{sub 2} films with higher T{sub IMT}, smaller ΔA, broader ΔH and asymmetric hysteresis loop. The good control of the VO{sub 2} IMT features in the THz domain could be further exploited for the development of advanced smart devices, such as ultrafast switches, modulators, memories and sensors.

Ultra-high Q terahertz whispering-gallery modes in a silicon resonator

Science.gov (United States)

Vogt, Dominik Walter; Leonhardt, Rainer

2018-05-01

We report on the first experimental demonstration of terahertz (THz) whispering-gallery modes (WGMs) with an ultra-high quality factor of 1.5 × 104 at 0.62 THz. The WGMs are observed in a high resistivity float zone silicon spherical resonator coupled to a sub-wavelength silica waveguide. A detailed analysis of the coherent continuous wave THz spectroscopy measurements combined with a numerical model based on Mie-Debye-Aden-Kerker theory allows us to unambiguously identify the observed higher order radial THz WGMs.

THz - ToF Optical Layer Analysis (OLA) to determine optical properties of dielectric materials

Science.gov (United States)

Spranger, Holger; Beckmann, Jörg

2017-02-01

Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. The knowledge of the base materials shape and optical properties is essential for a proper reconstruction result. To obtain these properties a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric characteristics. The Optical Layer Analysis (OLA) is able to fulfill these requirements. A short description why the optical properties are crucial for meaningful SAFT reconstruction results will be given first. Afterwards the OLA will be derived and applied on representative samples to discuss and evaluate its benefits and limits.

Grating-Coupled Waveguide Cloaking

International Nuclear Information System (INIS)

Wang Jia-Fu; Qu Shao-Bo; Ma Hua; Wang Cong-Min; Wang Xin-Hua; Zhou Hang; Xu Zhuo; Xia Song

2012-01-01

Based on the concept of a grating-coupled waveguide (GCW), a new strategy for realizing EM cloaking is presented. Using metallic grating, incident waves are firstly coupled into the effective waveguide and then decoupled into free space behind, enabling EM waves to pass around the obstacle. Phase compensation in the waveguide keeps the wave-front shape behind the obstacle unchanged. Circular, rectangular and triangular cloaks are presented to verify the robustness of the GCW cloaking. Electric field animations and radar cross section (RCS) comparisons convincingly demonstrate the cloaking effect

Semiconductor plasmonic crystals: active control of THz extinction

International Nuclear Information System (INIS)

Schaafsma, M C; Rivas, J Gómez

2013-01-01

We investigate theoretically the enhanced THz extinction by periodic arrays of semiconductor particles. Scattering particles of doped semiconductors can sustain localized surface plasmon polaritons, which can be diffractively coupled giving rise to surface lattice resonances. These resonances are characterized by a large extinction and narrow bandwidth, which can be tuned by controlling the charge carrier density in the semiconductor. The underlaying mechanism leading to this tuneability is explained using the coupled dipole approximation and considering GaAs as the semiconductor. The enhanced THz extinction in arrays of GaAs particles could be tuned in a wide range by optical pumping of charge carriers. (invited article)

Attenuation in Superconducting Circular Waveguides

Directory of Open Access Journals (Sweden)

K. H. Yeap

2016-09-01

Full Text Available We present an analysis on wave propagation in superconducting circular waveguides. In order to account for the presence of quasiparticles in the intragap states of a superconductor, we employ the characteristic equation derived from the extended Mattis-Bardeen theory to compute the values of the complex conductivity. To calculate the attenuation in a circular waveguide, the tangential fields at the boundary of the wall are first matched with the electrical properties (which includes the complex conductivity of the wall material. The matching of fields with the electrical properties results in a set of transcendental equations which is able to accurately describe the propagation constant of the fields. Our results show that although the attenuation in the superconducting waveguide above cutoff (but below the gap frequency is finite, it is considerably lower than that in a normal waveguide. Above the gap frequency, however, the attenuation in the superconducting waveguide increases sharply. The attenuation eventually surpasses that in a normal waveguide. As frequency increases above the gap frequency, Cooper pairs break into quasiparticles. Hence, we attribute the sharp rise in attenuation to the increase in random collision of the quasiparticles with the lattice structure.

MHD waveguides in space plasma

International Nuclear Information System (INIS)

Mazur, N. G.; Fedorov, E. N.; Pilipenko, V. A.

2010-01-01

The waveguide properties of two characteristic formations in the Earth's magnetotail-the plasma sheet and the current (neutral) sheet-are considered. The question of how the domains of existence of different types of MHD waveguide modes (fast and slow, body and surface) in the (k, ω) plane and their dispersion properties depend on the waveguide parameters is studied. Investigation of the dispersion relation in a number of particular (limiting) cases makes it possible to obtain a fairly complete qualitative pattern of all the branches of the dispersion curve. Accounting for the finite size of perturbations across the wave propagation direction reveals new additional effects such as a change in the critical waveguide frequencies, the excitation of longitudinal current at the boundaries of the sheets, and a change in the symmetry of the fundamental mode. Knowledge of the waveguide properties of the plasma and current sheets can explain the occurrence of preferred frequencies in the low-frequency fluctuation spectra in the magnetotail. In satellite observations, the type of waveguide mode can be determined from the spectral properties, as well as from the phase relationships between plasma oscillations and magnetic field oscillations that are presented in this paper.

Terahertz (THz) Optical Parameters of Three-Dimensional (3-D) Printing Materials

Science.gov (United States)

2017-03-01

Terahertz (THz), Submillimeter Wave, Imaging 15. NUMBER OF PAGES 16 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT UNCLASSIFIED 18...and imaging has become a topic of research as an optical technique to study these materials because THz radiation can penetrate many visibly opaque...2) Three materials, each tinted with two different colors, were measured. The materials were High Impact polystyrene (HIPS

Tunable graphene antennas for selective enhancement of THz-emission

KAUST Repository

Filter, Robert; Farhat, Mohamed; Steglich, Mathias; Alaee, Rasoul; Rockstuhl, Carsten; Lederer, Falk L.

2013-01-01

In this paper, we will introduce THz graphene antennas that strongly enhance the emission rate of quantum systems at specific frequencies. The tunability of these antennas can be used to selectively enhance individual spectral features. We will show as an example that any weak transition in the spectrum of coronene can become the dominant contribution. This selective and tunable enhancement establishes a new class of graphene-based THz devices, which will find applications in sensors, novel light sources, spectroscopy, and quantum communication devices. © 2013 Optical Society of America.

THz imaging of majolica tiles and biological attached marble fragments

Science.gov (United States)

Catapano, Ilaria; Soldovieri, Francesco

2016-04-01

Devices exploiting waves in the frequency range from 0.1 THz to 10 THz (corresponding to a free-space wavelength ranging from 30 μm to 3 mm) deserve attention as diagnostic technologies for cultural heritage. THz waves are, indeed, non-ionizing radiations capable of penetrating into non-metallic materials, which are opaque to both visible and infrared waves, without implying long term risks to the molecular stability of the exposed objects and humans. Moreover, THz surveys involve low poewr probing waves, are performed without contact with the object and, thanks to the recent developments, which have allowed the commercialization of compact, flexible and portable systems, maybe performed in loco (i.e. in the place where the artworks are usually located). On the other hand, THz devices can be considered as the youngest among the sensing and imaging electromagnetic techniques and their actual potentialities in terms of characterization of artworks is an ongoing research activity. As a contribution within this context, we have performed time of flight THz imaging [1,2] on ceramic and marble objects. In particular, we surveyed majolica tiles produced by Neapolitan ceramists in the 18th and 19th centuries with the aim to gather information on their structure, constructive technique and conservation state. Moreover, we investigated a Marmo di Candoglia fragment in order to characterize the biological attach affecting it. All the surveys were carried out by using the Fiber-Coupled Terahertz Time Domain System (FICO) developed by Z-Omega and available at the Institute of Electromagnetic Sensing of the Environment (IREA). This system is equipped with fiber optic coupled transmitting and receiving probes and with an automatic positioning system enabling to scan a 150 mm x 150 mm area under a reflection measurement configuration. Based on the obtained results we can state that the use of THz waves allows: - the reconstruction of the object topography; - the geometrical

Black phosphorus: broadband nonlinear optical absorption and application

Science.gov (United States)

Li, Ying; He, Yanliang; Cai, Yao; Chen, Shuqing; Liu, Jun; Chen, Yu; Yuanjiang, Xiang

2018-02-01

Black phosphorus (BP), 2D layered material with layered dependent direct bandgap (0.3 eV (bulk), 2.0 eV (single layer)) that has gained renewed attention, has been demonstrated as an extremely appropriate optical material for broadband optical applications from infrared to mid-infrared wavebands. Herein, by coupling multi-layer BP films with microfiber, we fabricated a nonlinear optical device with long light-matter interaction distance and enhanced damage threshold. Through taking full advantage of its fine nonlinear optical absorption property, we obtained stable mode-locking (51 ps) and Q-switched mode-locking states in Yb-doped or Er-doped (403.7 fs) all-fiber lasers and the single-longitudinal-mode operation (53 kHz) in an Er-doped fiber laser with enhanced power tolerance, using the same nonlinear optical device. Our results showed that BP could be a favorable nonlinear optical material for developing BP-enabled wave-guiding photonic devices, and revealed new insight into BP for high optical power unexplored optical devices.

Design of a dedicated beamline for THz coherent synchrotron radiation at UVSOR-III

International Nuclear Information System (INIS)

Kimura, Shin-ichi; Nakamura, Eiken; Imura, Keiichiro; Katoh, Masahiro; Hosaka, Masahito; Takahashi, Toshiharu

2012-01-01

We report the design of a THz beamline for coherent synchrotron radiation (CSR) at the UVSOR-III very-low-emittance synchrotron radiation light source. The emitted THz-CSR is collected by a three-dimensional 'magic mirror', which is a perfect collecting mirror for bending-magnet radiation with an acceptance angle of 288 mrad (H) × 80 mrad (V). A quasi-monochromatic THz-CSR with an average flux of 104 μW/0.1 % b.w. and a peak power of 120 nJ/pulse/0.1 % b.w. is expected at the beamline.

Dual-channel operation in a synchronously pumped optical parametric oscillator for the generation of broadband mid-infrared coherent light sources.

Science.gov (United States)

Liu, Pei; Wang, Sicong; He, Puyuan; Zhang, Zhaowei

2018-05-01

We report, to the best of our knowledge, a novel approach for generating broadband mid-infrared (mid-IR) light by implementing a dual-channel scheme in a synchronously pumped optical parametric oscillator (SPOPO). Two-channel operation was achieved by inserting a prism pair and two reflection mirrors inside an optical parametric oscillator (OPO) cavity. Pumped by a Yb-fiber laser, the OPO generated an idler wave at ∼3150  nm with a -10  dB bandwidth of ∼13.2  THz, which was twice as much as that of the pump source. This scheme represents a promising technical route to transform conventional SPOPOs into a device capable of generating mid-IR light with very broad instantaneous bandwidth.

Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation.

Science.gov (United States)

Wan, W J; Li, H; Zhou, T; Cao, J C

2017-03-08

Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification.

THz limb sounder (TLS) for lower thermospheric wind, oxygen density, and temperature

Science.gov (United States)

Wu, Dong L.; Yee, Jeng-Hwa; Schlecht, Erich; Mehdi, Imran; Siles, Jose; Drouin, Brian J.

2016-07-01

Neutral winds are one of the most critical measurements in the lower thermosphere and E region ionosphere (LTEI) for understanding complex electrodynamic processes and ion-neutral interactions. We are developing a high-sensitivity, low-power, noncryogenic 2.06 THz Schottky receiver to measure wind profiles at 100-140 km. The new technique, THz limb sounder (TLS), aims to measure LTEI winds by resolving the wind-induced Doppler shift of 2.06 THz atomic oxygen (OI) emissions. As a transition between fine structure levels in the ground electronic state, the OI emission is in local thermodynamic equilibrium (LTE) at altitudes up to 350 km. This LTE property, together with day-and-night capability and small line-of-sight gradient, makes the OI limb sounding a very attractive technique for neutral wind observations. In addition to the wind measurement, TLS can also retrieve [OI] density and neutral temperature in the LTEI region. TLS leverages rapid advances in THz receiver technologies including subharmonically pumped (SHP) mixers and Schottky-diode-based power multipliers. Current SHP Schottky receivers have produced good sensitivity for THz frequencies at ambient environment temperatures (120-150 K), which are achievable through passively cooling in spaceflight. As an emerging technique, TLS can fill the critical data gaps in the LTEI neutral wind observations to enable detailed studies on the coupling and dynamo processes between charged and neutral molecules.

Photonic crystal waveguides in artificial opals

DEFF Research Database (Denmark)

Lavrinenko, Andrei; Kiyan, Roman; Neumeister, Andrei

2008-01-01

3D photonic crystals based on Si inverted-opals are numerically explored as hosts for effective air-channel waveguides, which can serve as parts of photonic circuits. Two basic shapes of straight waveguides are considered: cylindrical and a chain of spheres. Modelling shows that transmission...... is heavily dependent on the lattice position of the waveguide and its direction. Our experiments of defect inscription by 2-photon polymerization for the production of straight and bent waveguides in opal templates are reported....

Ballistic Deflection Transistors for THz Amplification

Science.gov (United States)

2016-05-09

glass nano-materials. Si-on-glass is an interesting material with possible applications ranging from ultrafast electronics to solar cells. We used our...planar geometry allows for a flexible design and easy integration as a multi-element sensor or with either optical nano-concentrators or THz coupling

Coupled nanopillar waveguides: optical properties and applications

DEFF Research Database (Denmark)

Chigrin, Dmitry N.; Zhukovsky, Sergei V.; Lavrinenko, Andrei

2007-01-01

, while guided modes dispersion is strongly affected by the waveguide structure. We present a systematic analysis of the optical properties of coupled nanopillar waveguides and discuss their possible applications for integrated optics. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim......In this paper we review basic properties of coupled periodic and aperiodic nanopillar waveguides. A coupled nanopillar waveguide consists of several rows of periodically or aperiodically placed dielectric rods (pillars). In such a waveguide, light confinement is due to the total internal reflection...

Effect of patterns and inhomogeneities on the surface of waveguides used for optical waveguide lightmode spectroscopy applications

DEFF Research Database (Denmark)

Horvath, R.; Voros, J.; Graf, R.

2001-01-01

It has been found that patterns acid inhomogeneities on the surface of the waveguide used fur optical waveguide lightmode spectroscopy applications can produce broadening and fine structure in the incoupled light peak spectra. During cell spreading on the waveguide, a broadening of the incoupling...

Three-dimensional patterning in polymer optical waveguides using focused ion beam milling

Science.gov (United States)

Kruse, Kevin; Burrell, Derek; Middlebrook, Christopher

2016-07-01

Waveguide (WG) photonic-bridge taper modules are designed for symmetric planar coupling between silicon WGs and single-mode fibers (SMFs) to minimize photonic chip and packaging footprint requirements with improving broadband functionality. Micromachined fabrication and evaluation of polymer WG tapers utilizing high-resolution focused ion beam (FIB) milling is performed and presented. Polymer etch rates utilizing the FIB and optimal methods for milling polymer tapers are identified for three-dimensional patterning. Polymer WG tapers with low sidewall roughness are manufactured utilizing FIB milling and optically tested for fabrication loss. FIB platforms utilize a focused beam of ions (Ga+) to etch submicron patterns into substrates. Fabricating low-loss polymer WG taper prototypes with the FIB before moving on to mass-production techniques provides theoretical understanding of the polymer taper and its feasibility for connectorization devices between silicon WGs and SMFs.

THz Properties of Adhesives

Science.gov (United States)

Stübling, E.; Gomell, L.; Sommer, S.; Winkel, A.; Kahlmeyer, M.; Böhm, S.; Koch, M.

2018-06-01

We determined the THz properties of 12 different adhesives which are mainly used for industrial purposes. The adhesives applied can be classified according to their chemical structure: epoxy resins, acrylic resins, and polyurethane based materials. This work represents a basis for future studies, which will concentrate on aging effects, including the absorption of water of adhesive joints. Thus, the dielectric properties of the unaged adhesives are investigated and the results of these measurements are described herein.

[Extracting THz absorption coefficient spectrum based on accurate determination of sample thickness].

Science.gov (United States)

Li, Zhi; Zhang, Zhao-hui; Zhao, Xiao-yan; Su, Hai-xia; Yan, Fang

2012-04-01

Extracting absorption spectrum in THz band is one of the important aspects in THz applications. Sample's absorption coefficient has a complex nonlinear relationship with its thickness. However, as it is not convenient to measure the thickness directly, absorption spectrum is usually determined incorrectly. Based on the method proposed by Duvillaret which was used to precisely determine the thickness of LiNbO3, the approach to measuring the absorption coefficient spectra of glutamine and histidine in frequency range from 0.3 to 2.6 THz(1 THz = 10(12) Hz) was improved in this paper. In order to validate the correctness of this absorption spectrum, we designed a series of experiments to compare the linearity of absorption coefficient belonging to one kind amino acid in different concentrations. The results indicate that as agreed by Lambert-Beer's Law, absorption coefficient spectrum of amino acid from the improved algorithm performs better linearity with its concentration than that from the common algorithm, which can be the basis of quantitative analysis in further researches.

THz spectroscopy: An emerging technology for pharmaceutical development and pharmaceutical Process Analytical Technology (PAT) applications

Science.gov (United States)

Wu, Huiquan; Khan, Mansoor

2012-08-01

As an emerging technology, THz spectroscopy has gained increasing attention in the pharmaceutical area during the last decade. This attention is due to the fact that (1) it provides a promising alternative approach for in-depth understanding of both intermolecular interaction among pharmaceutical molecules and pharmaceutical product quality attributes; (2) it provides a promising alternative approach for enhanced process understanding of certain pharmaceutical manufacturing processes; and (3) the FDA pharmaceutical quality initiatives, most noticeably, the Process Analytical Technology (PAT) initiative. In this work, the current status and progress made so far on using THz spectroscopy for pharmaceutical development and pharmaceutical PAT applications are reviewed. In the spirit of demonstrating the utility of first principles modeling approach for addressing model validation challenge and reducing unnecessary model validation "burden" for facilitating THz pharmaceutical PAT applications, two scientific case studies based on published THz spectroscopy measurement results are created and discussed. Furthermore, other technical challenges and opportunities associated with adapting THz spectroscopy as a pharmaceutical PAT tool are highlighted.

Focal plane arrays for THz imaging

NARCIS (Netherlands)

Iacono, A.; Bencivenni, C.; Freni, A.; Neto, A.; Gerini, G.

2012-01-01

The growing attention for Terahertz technology finds support in the high number of applications which will benefit by its use. In the space science sector, the investigation of the THz frequency range will improve the knowledge of the universe, giving a clearer view on its origin and its evolution.

Microring Diode Laser for THz Generation

DEFF Research Database (Denmark)

Mariani, S.; Andronico, A.; Favero, I.

2013-01-01

We report on the modeling and optical characterization of AlGaAs/InAs quantum-dot microring diode lasers designed for terahertz (THz) difference frequency generation (DFG) between two whispering gallery modes (WGMs) around 1.3 $\\mu$m. In order to investigate the spectral features of this active...

Role of misalignment-induced angular chirp in the electro-optic detection of THz waves

CERN Document Server

Walsh, D A; Pan, R; Snedden, E W; Graham, D M; Gillespie, W A; Jamison, S P

2014-01-01

A general description of electro-optic detection including non-collinear phase matching and finite transverse beam profiles is presented. It is shown theoretically and experimentally that non-collinear phase matching in ZnTe (and similar materials) produces an angular chirp in the chi((2))-generated optical signal. Due to this, in non-collinear THz and probe arrangements such as single-shot THz measurements or through accidental misalignment, measurement of an undistorted THz signal is critically dependent on having sufficient angular acceptance in the optical probe path. The associated spatial walk-off can also preclude the phase retardation approximation used in THz-TDS. The rate of misalignment-induced chirping in commonly used ZnTe and GaP schemes is tabulated, allowing ready analysis of a detection system. (C) 2014 Optical Society of America.

Perspective: Watching low-frequency vibrations of water in biomolecular recognition by THz spectroscopy

Science.gov (United States)

Xu, Yao; Havenith, Martina

2015-11-01

Terahertz (THz) spectroscopy has turned out to be a powerful tool which is able to shed new light on the role of water in biomolecular processes. The low frequency spectrum of the solvated biomolecule in combination with MD simulations provides deep insights into the collective hydrogen bond dynamics on the sub-ps time scale. The absorption spectrum between 1 THz and 10 THz of solvated biomolecules is sensitive to changes in the fast fluctuations of the water network. Systematic studies on mutants of antifreeze proteins indicate a direct correlation between biological activity and a retardation of the (sub)-ps hydration dynamics at the protein binding site, i.e., a "hydration funnel." Kinetic THz absorption studies probe the temporal changes of THz absorption during a biological process, and give access to the kinetics of the coupled protein-hydration dynamics. When combined with simulations, the observed results can be explained in terms of a two-tier model involving a local binding and a long range influence on the hydration bond dynamics of the water around the binding site that highlights the significance of the changes in the hydration dynamics at recognition site for biomolecular recognition. Water is shown to assist molecular recognition processes.

Near-field characterization of plasmonic waveguides

DEFF Research Database (Denmark)

Zenin, Volodymyr

2014-01-01

simply by changing geometric parameters of the waveguide, keeping in mind the trade-off between confinement and propagation losses. A broad variety of plasmonic waveguides and waveguide components, including antennas for coupling the light in/out of the waveguide, requires correspondent characterization...... capabilities, especially on experimental side. The most straight-forward and powerful technique for such purpose is scanning near-field optical microscopy, which allows to probe and map near-field distribution and therefore becomes the main tool in this project. The detailed description of the used setups...

Innovative monolithic detector for tri-spectral (THz, IR, Vis) imaging

Science.gov (United States)

Pocas, S.; Perenzoni, M.; Massari, N.; Simoens, F.; Meilhan, J.; Rabaud, W.; Martin, S.; Delplanque, B.; Imperinetti, P.; Goudon, V.; Vialle, C.; Arnaud, A.

2012-10-01

Fusion of multispectral images has been explored for many years for security and used in a number of commercial products. CEA-Leti and FBK have developed an innovative sensor technology that gathers monolithically on a unique focal plane arrays, pixels sensitive to radiation in three spectral ranges that are terahertz (THz), infrared (IR) and visible. This technology benefits of many assets for volume market: compactness, full CMOS compatibility on 200mm wafers, advanced functions of the CMOS read-out integrated circuit (ROIC), and operation at room temperature. The ROIC houses visible APS diodes while IR and THz detections are carried out by microbolometers collectively processed above the CMOS substrate. Standard IR bolometric microbridges (160x160 pixels) are surrounding antenna-coupled bolometers (32X32 pixels) built on a resonant cavity customized to THz sensing. This paper presents the different technological challenges achieved in this development and first electrical and sensitivity experimental tests.

Diffraction of an Electromagnetic Wave on a Dielectric Rod in a Rectangular Waveguide. A Method of Partial Waveguide Filling

Science.gov (United States)

Zav'yalov, A. S.

2018-04-01

A variant of the method of partial waveguide filling is considered in which a sample is put into a waveguide through holes in wide waveguide walls at the distance equal to a quarter of the wavelength in the waveguide from a short-circuiter, and the total input impedance of the sample in the waveguide is directly measured. The equivalent circuit of the sample is found both without and with account of the hole. It is demonstrated that consideration of the edge effect makes it possible to obtain more exact values of the dielectric permittivity.

External-cavity high-power dual-wavelength tapered amplifier with tunable THz frequency difference

DEFF Research Database (Denmark)

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

2012-01-01

A tunable 800 nm high-power dual-wavelength diode laser system with double-Littrow external-cavity feedback is demonstrated. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 5.0 THz. A maximum output power of 1.54 W is achie......A tunable 800 nm high-power dual-wavelength diode laser system with double-Littrow external-cavity feedback is demonstrated. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 5.0 THz. A maximum output power of 1.54 W...... is achieved with a frequency difference of 0.86 THz, the output power is higher than 1.3 W in the 5.0 THz range of frequency difference, and the amplified spontaneous emission intensity is more than 20 dB suppressed in the range of frequency difference. The beam quality factor M2 is 1.22±0.15 at an output...

Arrayed waveguide Sagnac interferometer.

Science.gov (United States)

Capmany, José; Muñoz, Pascual; Sales, Salvador; Pastor, Daniel; Ortega, Beatriz; Martinez, Alfonso

2003-02-01

We present a novel device, an arrayed waveguide Sagnac interferometer, that combines the flexibility of arrayed waveguides and the wide application range of fiber or integrated optics Sagnac loops. We form the device by closing an array of wavelength-selective light paths provided by two arrayed waveguides with a single 2 x 2 coupler in a Sagnac configuration. The equations that describe the device's operation in general conditions are derived. A preliminary experimental demonstration is provided of a fiber prototype in passive operation that shows good agreement with the expected theoretical performance. Potential applications of the device in nonlinear operation are outlined and discussed.

Analysis of Waveguides on Lithium Niobate Thin Films

Directory of Open Access Journals (Sweden)

Yiwen Wang

2018-04-01

Full Text Available Waveguides formed by etching, proton-exchange (PE, and strip-loaded on single-crystal lithium niobate (LN thin film were designed and simulated by a full-vectorial finite difference method. The single-mode condition, optical power distribution, and bending loss of these kinds of waveguides were studied and compared systematically. For the PE waveguide, the optical power distributed in LN layer had negligible change with the increase of PE thickness. For the strip-loaded waveguide, the relationships between optical power distribution in LN layer and waveguide thickness were different for quasi-TE (q-TE and quasi-TM (q-TM modes. The bending loss would decrease with the increase of bending radius. There was a bending loss caused by the electromagnetic field leakage when the neff of q-TM waveguide was smaller than that of nearby TE planar waveguide. LN ridge waveguides possessed a low bending loss even at a relatively small bending radius. This study is helpful for the understanding of waveguide structures as well as for the optimization and the fabrication of high-density integrated optical components.

Nano-Antenna For Terahertz (THz) Medical Imaging Applications

Data.gov (United States)

National Aeronautics and Space Administration — As a result of technological breakthroughs, research and applications in the Terahertz (THz) radiation system are experiencing explosive growth. The non-ionizing and...

Real-time computer treatment of THz passive device images with the high image quality

Science.gov (United States)

Trofimov, Vyacheslav A.; Trofimov, Vladislav V.

2012-06-01

We demonstrate real-time computer code improving significantly the quality of images captured by the passive THz imaging system. The code is not only designed for a THz passive device: it can be applied to any kind of such devices and active THz imaging systems as well. We applied our code for computer processing of images captured by four passive THz imaging devices manufactured by different companies. It should be stressed that computer processing of images produced by different companies requires using the different spatial filters usually. The performance of current version of the computer code is greater than one image per second for a THz image having more than 5000 pixels and 24 bit number representation. Processing of THz single image produces about 20 images simultaneously corresponding to various spatial filters. The computer code allows increasing the number of pixels for processed images without noticeable reduction of image quality. The performance of the computer code can be increased many times using parallel algorithms for processing the image. We develop original spatial filters which allow one to see objects with sizes less than 2 cm. The imagery is produced by passive THz imaging devices which captured the images of objects hidden under opaque clothes. For images with high noise we develop an approach which results in suppression of the noise after using the computer processing and we obtain the good quality image. With the aim of illustrating the efficiency of the developed approach we demonstrate the detection of the liquid explosive, ordinary explosive, knife, pistol, metal plate, CD, ceramics, chocolate and other objects hidden under opaque clothes. The results demonstrate the high efficiency of our approach for the detection of hidden objects and they are a very promising solution for the security problem.

28.3THz bowtie antenna integrated rectifier for infrared energy harvesting

KAUST Repository

Gadalla, Mena N.

2014-10-01

The design, fabrication and characterization of an asymmetric 28.3 THz antenna integrated rectifier (rectenna) using Au/Al2O3/Pt is presented. The rectenna design comprises a sharp tip bowtie antenna and a tunneling Metal-insulator-Metal (MIM) diode. The design benefits from the geometric field enhancement around the nano tips of the bowtie antenna. Simultaneous optimization of the antenna\\'s length and flare angle resulted in a relative intensity enhancement of 104 for a 10 nm gap. In order to benefit from the field enhancement, the THz diode is realized through the overlap of the bowtie sharp tips exactly at the hot spot. Dissimilar electrodes are used to allow THz signals rectification at zero bias, which is critical for energy harvesting applications. The rectenna exhibits a zero bias responsivity of 10 A/W. © 2014 European Microwave Association.

Experimental demonstration of a broadband two-mode multi/demultiplexer based on asymmetric Y-junctions

Science.gov (United States)

Li, Haiqin; Wang, Pengjun; Yang, Tianjun; Dai, Tingge; Wang, Gencheng; Li, Shiqi; Chen, Weiwei; Yang, Jianyi

2018-03-01

A broadband two-mode multi/demultiplexer using asymmetric Y-junctions is designed and experimentally demonstrated on a silicon-on-insulator platform for on-chip mode-division multiplexing applications. Within a bandwidth from 1513 to 1619 nm, the fabricated device, which consists of a two-mode multiplexer, a multimode straight waveguide, and a two-mode demultiplexer, exhibits demultiplexing crosstalk of less than -9.1 dB. The demultiplexing crosstalk as low as -42.1 dB, lower than -12.8 dB over the C band can be obtained. The measured insertion loss varies from 0.40 to 0.56 dB at a wavelength of 1550 nm. A transmission experiment of 10 Gbit/s electrical signals carried on TE0 and TE1 modes is successfully achieved with open and clear eye diagrams.

Nanoscale devices based on plasmonic coaxial waveguide resonators

Science.gov (United States)

Mahigir, A.; Dastmalchi, P.; Shin, W.; Fan, S.; Veronis, G.

2015-02-01

Waveguide-resonator systems are particularly useful for the development of several integrated photonic devices, such as tunable filters, optical switches, channel drop filters, reflectors, and impedance matching elements. In this paper, we introduce nanoscale devices based on plasmonic coaxial waveguide resonators. In particular, we investigate threedimensional nanostructures consisting of plasmonic coaxial stub resonators side-coupled to a plasmonic coaxial waveguide. We use coaxial waveguides with square cross sections, which can be fabricated using lithography-based techniques. The waveguides are placed on top of a silicon substrate, and the space between inner and outer coaxial metals is filled with silica. We use silver as the metal. We investigate structures consisting of a single plasmonic coaxial resonator, which is terminated either in a short or an open circuit, side-coupled to a coaxial waveguide. We show that the incident waveguide mode is almost completely reflected on resonance, while far from the resonance the waveguide mode is almost completely transmitted. We also show that the properties of the waveguide systems can be accurately described using a single-mode scattering matrix theory. The transmission and reflection coefficients at waveguide junctions are either calculated using the concept of the characteristic impedance or are directly numerically extracted using full-wave three-dimensional finite-difference frequency-domain simulations.

Challenging Aspects of Terahertz Terabit Wireless Communications

DEFF Research Database (Denmark)

Yu, Xianbin; Galili, Michael; Jepsen, Peter Uhd

The increasing demand on fast wireless communications, e.g. huge data file transferring and mobile broadband access, has driven wireless communication systems into a path towards Terabit era. Terahertz (THz) technology is promising due to its unique features, such as unlimited bandwidth available......, in terms of THz generation and link power budget. The THz atmospheric absorption is another critical issue to limit wireless communication range....

Prospects of Using High-Intensity THz Pulses To Induce Ultrafast Temperature-Jumps in Liquid Water.

Science.gov (United States)

Mishra, Pankaj Kr; Bettaque, Vincent; Vendrell, Oriol; Santra, Robin; Welsch, Ralph

2018-06-01

Ultrashort, high-intensity terahertz (THz) pulses, e.g., generated at free-electron laser facilities, allow for direct investigation as well as the driving of intermolecular modes in liquids like water and thus will deepen our understanding of the hydrogen bonding network. In this work, the temperature-jump (T-jump) of water induced by THz radiation is simulated for ten different THz frequencies in the range from 3 to 30 THz and five different pulse intensities in the range from 1 × 10 11 to 5 × 10 12 W/cm 2 employing both ab initio molecular dynamics (AIMD) and force field molecular dynamics (FFMD) approaches. The most efficient T-jump can be achieved with 16 THz pulses. Three distinct T-jump mechanisms can be uncovered. For all cases, the T-jump mechanism proceeds within tens of femtoseconds (fs). For frequencies between 10 and 25 THz, most of the energy is initially transferred to the rotational degrees of freedom. Subsequently, the energy is redistributed to the translational and intramolecular vibrational degrees of freedom within a maximum of 500 fs. For the lowest frequencies considered (7 THz and below), translational and rotational degrees of freedom are heated within tens of fs as the THz pulse also couples to the intermolecular vibrations. Subsequently, the intramolecular vibrational modes are heated within a few hundred fs. At the highest frequencies considered (25 THz and above), vibrational and rotational degrees of freedom are heated within tens of fs, and energy redistribution to the translational degrees of freedom happens within several hundred fs. Both AIMD and FFMD simulations show a similar dependence of the T-jump on the frequency employed. However, the FFMD simulations overestimate the total energy transfer around the main peak and drop off too fast toward frequencies higher and lower than the main peak. These differences can be rationalized by missing elements, such as the polarizability, in the TIP4P/2005f force field employed. The

Unidirectional THz radiation propagation in BiFeO3

Science.gov (United States)

Room, Toomas

The mutual coupling between magnetism and electricity present in many multiferroic materials permit the magnetic control of the electric polarization and the electric control of the magnetization. These static magnetoelectric (ME) effects are of enormous interest: The ability to write a magnetic state current-free by an electric voltage would provide a huge technological advantage. However, ME coupling changes the low energy electrodynamics of these materials in unprecedented way - optical ME effects give rise to unidirectional light propagation as recently observed in low-temperature multiferroics. The transparent direction can be switched with dc magnetic or electric field, thus opening up new possibilities to manipulate the propagation of electromagnetic waves in multiferroic materials. We studied the unidirectional transmission of THz radiation in BiFeO3 crystals, the unique multiferroic compound offering a real potential for room temperature applications. The electrodynamics of BiFeO3 at 1THz and below is dominated by the spin wave modes of cycloidal spin order. We found that the optical magnetoelectric effect generated by spin waves in BiFeO3 is robust enough to cause considerable nonreciprocal directional dichroism in the GHz-THz range even at room temperature. The supporting theory attributes the observed unidirectional transmission to the spin-current-driven dynamic ME effect. Our work demonstrates that the nonreciprocal directional dichroism spectra of low energy excitations and their theoretical analysis provide microscopic model of ME couplings in multiferroic materials. Recent THz spectroscopy studies of multiferroic materials are an important step toward the realization of optical diodes, devices which transmit light in one but not in the opposite direction.

Waveguide-Based Biosensors for Pathogen Detection

Directory of Open Access Journals (Sweden)

Nile Hartman

2009-07-01

Full Text Available Optical phenomena such as fluorescence, phosphorescence, polarization, interference and non-linearity have been extensively used for biosensing applications. Optical waveguides (both planar and fiber-optic are comprised of a material with high permittivity/high refractive index surrounded on all sides by materials with lower refractive indices, such as a substrate and the media to be sensed. This arrangement allows coupled light to propagate through the high refractive index waveguide by total internal reflection and generates an electromagnetic wave—the evanescent field—whose amplitude decreases exponentially as the distance from the surface increases. Excitation of fluorophores within the evanescent wave allows for sensitive detection while minimizing background fluorescence from complex, “dirty” biological samples. In this review, we will describe the basic principles, advantages and disadvantages of planar optical waveguide-based biodetection technologies. This discussion will include already commercialized technologies (e.g., Corning’s EPIC® Ô, SRU Biosystems’ BIND™, Zeptosense®, etc. and new technologies that are under research and development. We will also review differing assay approaches for the detection of various biomolecules, as well as the thin-film coatings that are often required for waveguide functionalization and effective detection. Finally, we will discuss reverse-symmetry waveguides, resonant waveguide grating sensors and metal-clad leaky waveguides as alternative signal transducers in optical biosensing.

Ultrabroadband terahertz characterization of highly doped ZnO and ITO

DEFF Research Database (Denmark)

Wang, Tianwu; Zalkovskij, Maksim; Iwaszczuk, Krzysztof

2015-01-01

The broadband complex conductivities of transparent conducting oxides (TCO), namely, aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO) and tin-doped indium oxide (ITO), were investigated by using THz-TDS from 0.5 to 18 THz. The complex conductivities were accurately calculated using...

Quantitative terahertz time-domain spectroscopy and analysis in chemistry and biology

DEFF Research Database (Denmark)

Jepsen, Peter Uhd

2005-01-01

I will describe how Terahertz Time-Domain Spectroscopy (THz-TDS) can be used for quantitative, broadband spectroscopy in the far-infrared spectral region. Thz-TDS is sensitive to long-range, non-covalent interactions in the condensed phase, for instance intermolecular hydrogen bonding in molecula...

Broadband Faraday isolator.

Science.gov (United States)

Berent, Michał; Rangelov, Andon A; Vitanov, Nikolay V

2013-01-01

Driving on an analogy with the technique of composite pulses in quantum physics, we theoretically propose a broadband Faraday rotator and thus a broadband optical isolator, which is composed of sequences of ordinary Faraday rotators and achromatic quarter-wave plates rotated at the predetermined angles.

Coupled mode theory of periodic waveguides arrays

DEFF Research Database (Denmark)

Lavrinenko, Andrei; Chigrin, Dmitry N.

We apply the scalar coupled mode theory to the case of waveguides array consisting om two periodic waveguides. One of the waveguides is arbitrary shifted along another. A longitudinal shift acts as a parameter in the coupled mode theory. The proposed theory explains peculiarities of modes dispers...... dispersion and transmission in coupled periodic waveguides systems. Analytical results are compared with the numerical ones obtained by the plane wave expansion and FDTD methods....

Gap Surface Plasmon Waveguide Analysis

DEFF Research Database (Denmark)

Nielsen, Michael Grøndahl; Bozhevolnyi, Sergey I.

2014-01-01

Plasmonic waveguides supporting gap surface plasmons (GSPs) localized in a dielectric spacer between metal films are investigated numerically and the waveguiding properties at telecommunication wavelengths are presented. Especially, we emphasize that the mode confinement can advantageously...

Theoretical study of the folded waveguide

International Nuclear Information System (INIS)

Chen, G.L.; Owens, T.L.; Whealton, J.H.

1988-01-01

We have applied a three-dimensional (3-D) algorithm for solving Maxwell's equations to the analysis of foleded waveguides used for fusion plasma heating at the ion cyclotron resonance frequency. A rigorous analysis of the magnetic field structure in the folded waveguide is presented. The results are compared to experimenntal measurements. Optimum conditions for the folded waveguide are discussed. 6 refs., 10 figs

THz-TDS Characterization of the Digital Communication Channels of the Atmosphere and the Enabled Applications

Science.gov (United States)

Yang, Yihong; Mandehgar, Mahboubeh; Grischkowsky, D.

2015-02-01

Our measurements and complete linear dispersion theory calculations of amplitude and phase show that it is possible to have seven high performance point-to-point, 10.7 Gb/s to 28.4 Gb/s, digital THz ground links in the atmosphere. At a RH 58% (10g/m3) and 20 °C including O2 absorption, and for an absorption loss of 10 dB, the seven links are: Channel 1: at 96 GHz, Bandwidth (BW) 30 GHz, 10.7 Gb/s for 17.5 km, Channel 2: at 144 GHz, BW 30 GHz, 12.0 Gb/s for 7.4 km, Channel 3: at 252 GHz, BW 50 GHz, 25.2 Gb/s for 2.5 km, Channel 4: at 342 GHz, BW 24 GHz, 11.4 Gb/s for 840 m, Channel 5: at 408 GHz, BW 30 GHz, 13.6 Gb/s for 440 m, Channel 6: at 672 GHz, BW 60 GHz, 22.6 Gb/s for 140 m, and Channel 7: at 852 GHz, BW 60 GHz, 28.4 Gb/s for 120 m. The enabled long-path THz links are discussed. Two applications are presented in detail, namely, a long-path 17.5 km THz ground-link operating at 96 GHz, BW 30 GHz, 10.7 Gb/s, and a GEO satellite link at 252 GHz, BW 50 GHz, 25.2 Gb/s. In addition, Channel 7 at 852 GHz is studied by calculated pulse propagation to understand the relationships between high bit-rates and propagation distance. It is shown that good digital transmission could be obtained with 852 GHz, BW 108 GHz, 56.8 Gb/s for a 160 m propagation distance in the atmosphere with RH 58% (10g/m3) and 20 °C. Good digital transmission could also be obtained with 852 GHz, BW 108 GHz, 71.0 Gb/s for 80 m. These results are discussed with respect to high bit-rate, short-path applications. These digital THz communication channels were determined together with a new measurement of the water vapor continuum absorption from 0.35 to 1 THz. The THz pulses propagate though a 137 m long humidity-controlled chamber and are measured by THz time-domain spectroscopy (THz-TDS). The average relative humidity along the entire THz path is precisely obtained by measuring the difference between transit times of the sample and reference THz pulses to an accuracy of 0.1 ps. Using the measured

Photo-conductive detection of continuous THz waves via manipulated ultrafast process in nanostructures

Science.gov (United States)

Moon, Kiwon; Lee, Eui Su; Lee, Il-Min; Park, Dong Woo; Park, Kyung Hyun

2018-01-01

Time-domain and frequency-domain terahertz (THz) spectroscopy systems often use materials fabricated with exotic and expensive methods that intentionally introduce defects to meet short carrier lifetime requirements. In this study, we demonstrate the development of a nano-photomixer that meets response speed requirements without using defect-incorporated, low-temperature-grown (LTG) semiconductors. Instead, we utilized a thin InGaAs layer grown on a semi-insulating InP substrate by metal-organic chemical vapor deposition (MOCVD) combined with nano-electrodes to manipulate local ultrafast photo-carrier dynamics via a carefully designed field-enhancement and plasmon effect. The developed nano-structured photomixer can detect continuous-wave THz radiation up to a frequency of 2 THz with a peak carrier collection efficiency of 5%, which is approximately 10 times better than the reference efficiency of 0.4%. The better efficiency results from the high carrier mobility of the MOCVD-grown InGaAs thin layer with the coincidence of near-field and plasmon-field distributions in the nano-structure. Our result not only provides a generally applicable methodology for manipulating ultrafast carrier dynamics by means of nano-photonic techniques to break the trade-off relation between the carrier lifetime and mobility in typical LTG semiconductors but also contributes to mass-producible photo-conductive THz detectors to facilitate the widespread application of THz technology.

Light modulation abilities of nanostructures

DEFF Research Database (Denmark)

Lavrinenko, Andrei; Babicheva, Viktoriia; Novitsky, Andrey

2012-01-01

In the work we consider two new routes to impose control on the optical waveguides propagation. The first approach is based on the Kerr effect caused by the THz field, which strength is manifold times enhanced by the presence of a nanoslit in a metallic film surrounding the waveguide. The second ...

Fabrication of plasmonic waveguides for device applications

DEFF Research Database (Denmark)

Boltasseva, Alexandra; Leosson, Kristjan; Rosenzveig, Tiberiu

2007-01-01

and thickness-modulated gold strips different waveguide components including reflecting gratings can be realized. For applications where polarization is random or changing, metal nanowire waveguides are shown to be suitable candidates for efficient guiding of arbitrary polarized light. Plasmonic waveguides...

Concept of ceramics-free coaxial waveguide

International Nuclear Information System (INIS)

Arai, Hiroyuki

1994-01-01

A critical key point of the ITER IC antenna is ceramics support of an internal conductor of a coaxial antenna feeder close to the plasma, because dielectric loss tangent of ceramics enhanced due to neutron irradiation limits significantly the antenna injection power. This paper presents a ceramics-free waveguide to overcome this problem by a T-shaped ridged waveguide with arms for the mechanical support. This ridged waveguide has a low cutoff frequency for its small cross section, which has been proposed for the conceptual design study of Fusion Experimental Reactor (FER) IC system and the high frequency supplementary IC system for ITER. This paper presents the concept of ceramics-free coaxial waveguide consisting of the coaxial-line and the ridged waveguide. This paper also presents the cutoff frequency and the electric field distribution of the ridged waveguide calculated by a finite element method and an approximate method. The power handling capability more than 3 MW is evaluated by using the transmission-line theory and the optimized antenna impedance considering the ITER plasma parameters. We verify this transmission-line model by one-tenth scale models experimentally. (author)

Dispersion-tailored, low-loss photonic crystal fibers for the THz range

DEFF Research Database (Denmark)

Nielsen, Kristian; Rasmussen, Henrik K.; Adam, Aurèle J.L.

2009-01-01

We have fabricated a new type of photonic crystal fibers based on a cyclic olefin copolymer, transparent in the THz range. We characterize the propagation loss, dispersion, and spatial beam profile in fibers designed for low and high dispersion.......We have fabricated a new type of photonic crystal fibers based on a cyclic olefin copolymer, transparent in the THz range. We characterize the propagation loss, dispersion, and spatial beam profile in fibers designed for low and high dispersion....

Quantum-mechanical designed terahertz laser

International Nuclear Information System (INIS)

Benz, A.; Fasching, G.; Unterrainer, K.; Zobl, R.; Andrews, M.A.; Roch, T.; Schrenk, W.; Strasser, G.

2005-01-01

Full text: The terahertz-frequency region (1 THz=10 12 Hz) lies between RF-electronics and the photonics. Due to the large demand of coherent sources in this spectral range for applications liKEX medical imaging, chemical sensing and security applications large effort is put into the development of the THz-technology to close the THz-gap. The RF-electronics is able to generate frequencies up to around 0.1 THz, limited by the RC-time-constant of the system. The photonics on the other hand generates frequencies down to around 100 THz, defined by the bandgap of the used semiconducting material. Changing the wavelength requires the selection of a new material or of a new material composition. A new concept for coherent light sources is the quantum cascade laser (QCL), which was developed for the mid-infrared spectral region. The major advantage of the QCL-structure is the possibility to design the emission wavelength by band structure engineering. The wavelength is defined by the energy difference of quantized states in the conduction band. Here, we present a QCL working in the THz spectral region at 3 THz. The design is based on optical transitions between subbands of an AlGaAs/GaAs heterostructure. The thickness of the GaAs and AlGaAs layers were calculated to obtain quantized transitions at the desired THz-frequency. The wavefunctions were optimized to achieve the largest possible matrix element. 271 cascades were grown by molecular beam epitaxy to increase the optical gain and to achieve a waveguide thickness comparable to the THz-wavelength. We report lasing from conventional ridge waveguide and microcavity devices. (author)

Guided modes in silicene-based waveguides

Science.gov (United States)

Yu, Mengzhuo; He, Ying; Yang, Yanfang; Zhang, Huifang

2018-02-01

Silicene is a new Dirac-type electron system similar to graphene. A monolayer silicene sheet forms a quantum well induced by an electrostatic potential, which acts as an electron waveguide. The guided modes in the silicene waveguide have been investigated. Electron waves can propagate in the silicene-based waveguide in the cases of Klein tunneling and classical motion. The behavior of the wave function depends on the spin and valley indices. The amplitude of the electron wave function in the silicene waveguide can be controlled by the external electric field. These phenomena may be helpful for the potential applications of silicene-based electronic devices.

a Thz Photomixing Synthesizer Based on a Fiber Frequency Comb for High Resolution Rotational Spectroscopy

Science.gov (United States)

Hindle, Francis; Mouret, Gael; Cuisset, Arnaud; Yang, Chun; Eliet, Sophie; Bocquet, Robin

2010-06-01

To date the principal application for photomixing sources has been for high resolution spectroscopy of gases due to the large tuning range and spectral purity. New Developments of the Opto-Electronic THz Spectrometer have been performed in order to obtain a powerful tool for High-Resolution Spectroscopy. The combination of two extended cavity laser diodes and fast charge carrier lifetime semiconductor materials has allowed a continuous-wave THz spectrometer to be constructed based on optical heterodyning. Unlike many THz sources, this instrument gives access to all frequencies in the range 0.3 to 3.5 THz with a resolution of 1 MHz. The main spectroscopic applications of this spectrometer were dedicated to line profile analysis of rotational transitions referenced in the spectroscopic databases. One limitation of the THz spectrometer was accuracy with which the generated frequency is known. Recently, this obstacle has been circled with the construction of a photomixing spectrometer where the two pump lasers are phase locked to two modes of a repetition rate stabilized frequency doubled fiber laser frequency comb. In order to achieve a tuning range in excess to 100 MHz a third cw laser was required in the new configuration of the THz spectrometer. To assess the performances of this instrument, the frequencies of the pure rotational transitions of OCS molecules have been measured between 0,8 to 1,2 THz. A rms inferior to 100 kHz, deduced from the frequencies measured, demonstrates that the THz photomixing synthesizer is now able to be competitive with microwave and submillimeter techniques. S. Matton, F. Rohart, R. Bocquet, D. Bigourd, A. Cuisset, F. Hindle, G. Mouret, J. Mol. Spectrosc., 2006, 239: 182. C. Yang, J. Buldyreva, I. E. Gordon, F. Rohart, A. Cuisset, G. Mouret, R. Bocquet, F. Hindle, J. Quant. Spectrosc. Radiat. Transfer, 2008, 109: 2857. G. Mouret, F. Hindle, A. Cuisset, C. Yang, R. Bocquet, M. Lours, D. Rovera, Opt. Express, 2009, 17: 22031.

Dynamic diffraction-limited light-coupling of 3D-maneuvered wave-guided optical waveguides.

Science.gov (United States)

Villangca, Mark; Bañas, Andrew; Palima, Darwin; Glückstad, Jesper

2014-07-28

We have previously proposed and demonstrated the targeted-light delivery capability of wave-guided optical waveguides (WOWs). As the WOWs are maneuvered in 3D space, it is important to maintain efficient light coupling through the waveguides within their operating volume. We propose the use of dynamic diffractive techniques to create diffraction-limited spots that will track and couple to the WOWs during operation. This is done by using a spatial light modulator to encode the necessary diffractive phase patterns to generate the multiple and dynamic coupling spots. The method is initially tested for a single WOW and we have experimentally demonstrated dynamic tracking and coupling for both lateral and axial displacements.

Dynamic diffraction-limited light-coupling of 3D-maneuvered wave-guided optical waveguides

DEFF Research Database (Denmark)

Villangca, Mark Jayson; Bañas, Andrew Rafael; Palima, Darwin

2014-01-01

We have previously proposed and demonstrated the targeted-light delivery capability of wave-guided optical waveguides (WOWs). As the WOWs are maneuvered in 3D space, it is important to maintain efficient light coupling through the waveguides within their operating volume. We propose the use...... of dynamic diffractive techniques to create diffraction-limited spots that will track and couple to the WOWs during operation. This is done by using a spatial light modulator to encode the necessary diffractive phase patterns to generate the multiple and dynamic coupling spots. The method is initially tested...... for a single WOW and we have experimentally demonstrated dynamic tracking and coupling for both lateral and axial displacements....

Wideband absorption in one dimensional photonic crystal with graphene-based hyperbolic metamaterials

Science.gov (United States)

Kang, Yongqiang; Liu, Hongmei

2018-02-01

A broadband absorber which was proposed by one dimensional photonic crystal (1DPC) containing graphene-based hyperbolic metamaterials (GHMM) is theoretically investigated. For TM mode, it was demonstrated to absorb roughly 90% of all available electromagnetic waves at a 14 THz absorption bandwidth at normal incidence. The absorption bandwidth was affected by Fermi energy and thickness of dielectric layer. When the incident angle was increased, the absorption value decreased, and the absorption band had a gradual blue shift. These findings have potential applications for designing broadband optoelectronic devices at mid-infrared and THz frequency range.

Broadband radiometric LED measurements

Science.gov (United States)

Eppeldauer, G. P.; Cooksey, C. C.; Yoon, H. W.; Hanssen, L. M.; Podobedov, V. B.; Vest, R. E.; Arp, U.; Miller, C. C.

2016-09-01

At present, broadband radiometric LED measurements with uniform and low-uncertainty results are not available. Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric measurements are based on the CIE standardized V(λ) function, which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where the realization is always poor. Reference irradiance meters with spectrally constant response and high-intensity LED irradiance sources were developed here to implement the previously suggested broadband radiometric LED measurement procedure [1, 2]. Using a detector with spectrally constant response, the broadband radiometric quantities of any LEDs or LED groups can be simply measured with low uncertainty without using any source standard. The spectral flatness of filtered-Si detectors and low-noise pyroelectric radiometers are compared. Examples are given for integrated irradiance measurement of UV and blue LED sources using the here introduced reference (standard) pyroelectric irradiance meters. For validation, the broadband measured integrated irradiance of several LED-365 sources were compared with the spectrally determined integrated irradiance derived from an FEL spectral irradiance lamp-standard. Integrated responsivity transfer from the reference irradiance meter to transfer standard and field UV irradiance meters is discussed.

Broadband Internet and Income Inequality

OpenAIRE

HOUNGBONON , Georges Vivien; Liang , Julienne

2017-01-01

Policy makers are aiming for a large coverage of high-speed broadband Internet. However , there is still a lack of evidence about its effects on income distribution. In this paper, we investigate the effects of fixed broadband Internet on mean income and income inequality using a unique town-level data on broadband adoption and quality in France. We find that broadband adoption and quality raise mean income and lower income inequality. These results are robust to initial conditions, and yield...

Design of broadband dispersion flattened fiber for DWDM system: Performance analysis using various modulation formats

Science.gov (United States)

Goel, Aditya; Pandey, Gaurav

2018-05-01

In this paper, unique design of an optimal broadband optical dispersion flattened fiber (DFF) is proposed, which is capable of supporting the data rate of the order of Tb/s. The analysis of the single mode fiber for the design of the proposed DFF has been carried out by employing the quadratic Finite Element Method (FEM) with generalized refractive index (R. I.) profile. The minimization of the dispersion with respect to various profile parameters within the specified wavelength band is the essential optimization criteria. Computations show that a DFF can be designed where the overall dispersion can be restricted within ± 1 ps/km-nm over the entire spectral span ranging from 1290 to 1540 nm (250 nm) exhibiting a very small maximum value of dispersion slope (± 0.02 ps / (nm2-km)) in particular. The detailed performance analysis of the proposed DFF with different modulation techniques has been carried out in order to critically evaluate the performance of the DFF with respect to various significant parameters. The results suggest an excellent design of broadband optical waveguide capable of supporting high-speed data rate (40 Tb/s) through the single DFF, ideally suitable for the long haul dense wavelength division multiplexing (DWDM) optical transmission systems.

Is there a Biological Basis for Therapeutic Applications of Millimetre Waves and THz Waves?

Science.gov (United States)

Mattsson, Mats-Olof; Zeni, Olga; Simkó, Myrtill

2018-03-01

Millimetre wave (MMW) and THz wave (THz) applications are already employed in certain industrial and medical environments for non-destructive quality control, and medical imaging, diagnosis, and therapy, respectively. The aim of the present study is to investigate if published experimental studies (in vivo and in vitro) provide evidence for "non-thermal" biological effects of MMW and THz. Such effects would occur in absence of tissue heating and associated damage and are the ones that can be exploited for therapeutic medical use. The investigated studies provide some evidence for both MMW and THz that can influence biological systems in a manner that is not obviously driven by tissue heating. However, the number of relevant studies is very limited which severely limits the drawing of any far-reaching conclusions. Furthermore, the studies have not addressed specific interaction mechanisms and do not provide hints for future mechanistic studies. Also, the studies do not indicate any specific importance regarding power density levels, frequencies, or exposure duration. It is also unclear if any specific biological endpoints are especially sensitive. Any therapeutic potential of MMW or THz has to be evaluated based on future high-quality studies dealing with physical, bio-physical, and biological aspects that have specific health-related perspectives in mind.

Broadband microwave photonic fully tunable filter using a single heterogeneously integrated III-V/SOI-microdisk-based phase shifter.

Science.gov (United States)

Lloret, Juan; Morthier, Geert; Ramos, Francisco; Sales, Salvador; Van Thourhout, Dries; Spuesens, Thijs; Olivier, Nicolas; Fédéli, Jean-Marc; Capmany, José

2012-05-07

A broadband microwave photonic phase shifter based on a single III-V microdisk resonator heterogeneously integrated on and coupled to a nanophotonic silicon-on-insulator waveguide is reported. The phase shift tunability is accomplished by modifying the effective index through carrier injection. A comprehensive semi-analytical model aiming at predicting its behavior is formulated and confirmed by measurements. Quasi-linear and continuously tunable 2π phase shifts at radiofrequencies greater than 18 GHz are experimentally demonstrated. The phase shifter performance is also evaluated when used as a key element in tunable filtering schemes. Distortion-free and wideband filtering responses with a tuning range of ~100% over the free spectral range are obtained.

A comparative study of the plasmon effect in nanoelectrode THz emitters: Pulse vs. continuous-wave radiation

Energy Technology Data Exchange (ETDEWEB)

Moon, Kiwon; Lee, Eui Su; Lee, Il-Min; Han, Sang-Pil; Kim, Hyun-Soo; Park, Kyung Hyun, E-mail: khp@etri.re.kr [Terahertz Basic Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of); Choi, Jeongyong [Metal-Insulator Transition Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of); Lee, Donghun [Optical Internet Components Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of)

2016-08-15

Plasmonic field enhancement in terahertz (THz) generation is one of the recently arisen techniques in the THz field that has attracted considerable interest. However, the reported levels of enhancement of THz output power in the literature are significantly different from each other, from less than two times to about two orders of magnitude of enhancement in power, which implies the existence of other major limiting factors yet to be revealed. In this work, the contribution of the plasmonic effect to the power enhancement of THz emitters is revisited. We show that the carrier collection efficiency in a THz emitter with plasmonic nanostructures is more critical to the device performance than the plasmonic field enhancement itself. The strong reverse fields induced by the highly localized plasmonic carriers in the vicinity of the nanoelectrodes screen the carrier collections and seriously limit the power enhancement. This is supported by our experimental observations of the significantly enhanced power in a plasmonic nanoelectrode THz emitter in continuous-wave radiation mode, while the same device has limited enhancement with pulsed radiation. We hope that our study may provide an intuitive but practical guideline in adopting plasmonic nanostructures with an aim of enhancing the efficiency of optoelectronic devices.

Quantum Electrodynamics in Photonic Crystal Waveguides

DEFF Research Database (Denmark)

Nielsen, Henri Thyrrestrup

In this thesis we have performed quantum electrodynamics (QED) experiments in photonic crystal (PhC) waveguides and cavity QED in the Anderson localized regime in disordered PhC waveguides. Decay rate measurements of quantum dots embedded in PhC waveguides has been used to map out the variations...... in the local density of states (LDOS) in PhC waveguides. From decay rate measurements on quantum dot lines temperature tuned in the vicinity of the waveguide band edge, a β-factor for a single quantum dot of more then 85% has been extracted. Finite difference time domain simulations (FDTD) for disordered Ph...... is shown to increase from 3 − 7 um for no intentional disorder to 25 um for 6% disorder. A distribution of losses is seen to be necessary to explain the measured Q-factor distributions. Finally we have performed a cavity QED experiment between single quantum dots and an Anderson localized mode, where a β...

Electromagnetic Modeling of Distributed-Source-Excitation of Coplanar Waveguides: Applications to Traveling-Wave Photomixers

Science.gov (United States)

Pasqualini, Davide; Neto, Andrea; Wyss, Rolf A.

2001-01-01

In this work an electromagnetic model and subsequent design is presented for a traveling-wave, coplanar waveguide (CPW) based source that will operate in the THz frequency regime. The radio frequency (RF) driving current is a result of photoexcitation of a thin GaAs membrane using two frequency-offset lasers. The GaAs film is grown by molecular-beam-epitaxy (MBE) and displays sub-ps carrier lifetimes which enable the material conductivity to be modulated at a very high rate. The RF current flows between electrodes deposited on the GaAs membrane which are biased with a DC voltage source. The electrodes form a CPW and are terminated with a double slot antenna that couples the power to a quasi-optical system. The membrane is suspended above a metallic reflector to launch all radiation in one direction. The theoretical investigation and consequent design is performed in two steps. The first step consists of a direct evaluation of the magnetic current distribution on an infinitely extended coplanar waveguide excited by an impressed electric current distributed over a finite area. The result of the analysis is the difference between the incident angle of the laser beams and the length of the excited area that maximizes the RF power coupled to the CPW. The optimal values for both parameters are found as functions of the CPW and membrane dimensions as well as the dielectric constants of the layers. In the second step, a design is presented of a double slot antenna that matches the CPW characteristic impedance and gives good overall performance. The design is presently being implemented and measurements will soon be available.

Two-dimensional Kagome photonic bandgap waveguide

DEFF Research Database (Denmark)

Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou

2000-01-01

The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....

Carrier transport in THz quantum cascade lasers: Are Green's functions necessary?

International Nuclear Information System (INIS)

Matyas, A; Jirauschek, C; Kubis, T; Lugli, P

2009-01-01

We have applied two different simulation models for the stationary carrier transport and optical gain analysis in resonant phonon depopulation THz Quantum Cascade Lasers (QCLs), based on the semiclassical ensemble Monte Carlo (EMC) and fully quantum mechanical non-equilibrium Green's functions (NEGF) method, respectively. We find in the incoherent regime near and above the threshold current a qualitative and quantitative agreement of both methods. Therefore, we show that THz-QCLs can be successfully optimized utilizing the numerically efficient EMC method.

Numerical Investigation of Ultrafast interaction between THz Fields and Crystalline Materials

DEFF Research Database (Denmark)

Pedersen, Pernille Klarskov; Clark, Stewart J.; Jepsen, Peter Uhd

2014-01-01

We present a quantum - mechanical molecular dynamics investigation of the interaction between strong single - cyc le THz pulses and ionic crystals . We find nonlinearities in the response of the CsI crystals at field strengths higher than 10 MV/cm.......We present a quantum - mechanical molecular dynamics investigation of the interaction between strong single - cyc le THz pulses and ionic crystals . We find nonlinearities in the response of the CsI crystals at field strengths higher than 10 MV/cm....

Hollow waveguide cavity ringdown spectroscopy

Science.gov (United States)

Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

2012-01-01

Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

Adapting an optical nanoantenna for high E-field probing applications to a waveguided optical waveguide (WOW)

DEFF Research Database (Denmark)

Rindorf, Lars Henning; Glückstad, Jesper

2013-01-01

In the current work we intend to use the optical nano-antenna to include various functionalities for the recently demonstrated waveguided optical waveguide (WOW) by Palima et al. (Optics Express 2012). Specifically, we intend to study a WOW with an optical nano-antenna which can block the guiding......-stop characteristic. We give geometrical parameters necessary for realizing functioning nanoantennas. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.......In the current work we intend to use the optical nano-antenna to include various functionalities for the recently demonstrated waveguided optical waveguide (WOW) by Palima et al. (Optics Express 2012). Specifically, we intend to study a WOW with an optical nano-antenna which can block the guiding...... light wavelength while admitting other wavelengths of light which address certain functionalities, e.g. drug release, in the WOW. In particular, we study a bow-tie optical nano-antenna to circular dielectric waveguides in aqueous environments. It is shown with finite element computer simulations...

Enhanced optical-to-THz conversion efficiency of photoconductive antenna using dielectric nano-layer encapsulation

Science.gov (United States)

Gupta, Abhishek; Rana, Goutam; Bhattacharya, Arkabrata; Singh, Abhishek; Jain, Ravikumar; Bapat, Rudheer D.; Duttagupta, S. P.; Prabhu, S. S.

2018-05-01

Photoconductive antennas (PCAs) are among the most conventional devices used for emission as well as detection of terahertz (THz) radiation. However, due to their low optical-to-THz conversion efficiencies, applications of these devices in out-of-laboratory conditions are limited. In this paper, we report several factors of enhancement in THz emission efficiency from conventional PCAs by coating a nano-layer of dielectric (TiO2) on the active area between the electrodes of a semi-insulating GaAs-based device. Extensive experiments were done to show the effect of thicknesses of the TiO2 layer on the THz power enhancement with different applied optical power and bias voltages. Multiphysics simulations were performed to elucidate the underlying physics behind the enhancement of efficiency of the PCA. Additionally, this layer increases the robustness of the electrode gaps of the PCAs with high electrical insulation as well as protect it from external dust particles.

Waveguide Phased Array Antenna Analysis and Synthesis

NARCIS (Netherlands)

Visser, H.J.; Keizer, W.P.M.N.

1996-01-01

Results of two software packages for analysis and synthesis of waveguide phased array antennas are shown. The antennas consist of arrays of open-ended waveguides where irises can be placed in the waveguide apertures and multiple dielectric sheets in front of the apertures in order to accomplish a

Broadband Radiometric LED Measurements

OpenAIRE

Eppeldauer, G. P.; Cooksey, C. C.; Yoon, H. W.; Hanssen, L. M.; Podobedov, V. B.; Vest, R. E.; Arp, U.; Miller, C. C.

2016-01-01

At present, broadband radiometric measurements of LEDs with uniform and low-uncertainty results are not available. Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric measurements are based on the CIE standardized V(��) function, which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where the realization is always poor. Reference irr...

THz Imaging as a Method to Detect Defects of Aeronautical Coatings

Science.gov (United States)

Catapano, I.; Soldovieri, F.; Mazzola, L.; Toscano, C.

2017-10-01

Ice adhesion over critical aircraft surfaces is a serious potential hazard that runs the risk of causing accidents. To face this issue, the design and diagnostics of new multifunctional coatings with icephobic and aesthetical properties are demanded. In particular, diagnostic tools, capable of characterizing coating surface finishing and its defects, are needed. In this paper, terahertz (THz) imaging is considered as a high-resolution diagnostic tool useful for contactless surveys providing information on surface defects and material inner structure. Therefore, two composite specimens, one covered by a classical commercial livery coating and the other one by a new multifunctional coating with icephobic properties, are investigated by THz surveys carried out in normal environmental conditions of pressure and temperature. The results, obtained by processing the raw data properly, corroborate that THz imaging allows us to detect variations of the coating thickness, to localize hidden anomalies as well as to characterize surface defects at millimetric scale.

Spectroelectrochemical sensing: planar waveguides

Energy Technology Data Exchange (ETDEWEB)

Ross, Susan E.; Shi Yining; Seliskar, Carl J.; Heineman, William R

2003-09-30

The spectroelectrochemical sensor combines in a single device electrochemistry, spectroscopy, and selective partitioning into a film, giving improved selectivity for applications that involve complex samples. Sensing is based on the change in optical signal that accompanies electrochemical modulation of analyte that has partitioned into the film. Two classes of optical quality chemically-selective films based on two different host materials, namely, sol-gel processed silica and cross-linked poly(vinyl alcohol) have been developed. Films are typically 400-700 nm thick. Three types of sensor platforms are discussed: a multiple internal reflection (MIR) optic consisting of a bilayer of an indium tin oxide (ITO) optically transparent electrode deposited on a 1-mm thick glass substrate, a planar waveguide in which a potassium ion-exchanged BK7 glass waveguide (5-9 {mu}m thick) was over-coated with a thin film of ITO, and a planar waveguide in which a potassium ion-exchanged BK7 glass waveguide channel was formed and a pair of electrodes deposited along side the channel. These sensors were evaluated with ferrocyanide and a selective film of PDMDAAC-SiO{sub 2}, where PDMDAAC=poly(dimethyl diallylammonium chloride)

Spectroelectrochemical sensing: planar waveguides

International Nuclear Information System (INIS)

Ross, Susan E.; Shi Yining; Seliskar, Carl J.; Heineman, William R.

2003-01-01

The spectroelectrochemical sensor combines in a single device electrochemistry, spectroscopy, and selective partitioning into a film, giving improved selectivity for applications that involve complex samples. Sensing is based on the change in optical signal that accompanies electrochemical modulation of analyte that has partitioned into the film. Two classes of optical quality chemically-selective films based on two different host materials, namely, sol-gel processed silica and cross-linked poly(vinyl alcohol) have been developed. Films are typically 400-700 nm thick. Three types of sensor platforms are discussed: a multiple internal reflection (MIR) optic consisting of a bilayer of an indium tin oxide (ITO) optically transparent electrode deposited on a 1-mm thick glass substrate, a planar waveguide in which a potassium ion-exchanged BK7 glass waveguide (5-9 μm thick) was over-coated with a thin film of ITO, and a planar waveguide in which a potassium ion-exchanged BK7 glass waveguide channel was formed and a pair of electrodes deposited along side the channel. These sensors were evaluated with ferrocyanide and a selective film of PDMDAAC-SiO 2 , where PDMDAAC=poly(dimethyl diallylammonium chloride)

Schroedinger covariance states in anisotropic waveguides

International Nuclear Information System (INIS)

Angelow, A.; Trifonov, D.

1995-03-01

In this paper Squeezed and Covariance States based on Schroedinger inequality and their connection with other nonclassical states are considered for particular case of anisotropic waveguide in LiNiO 3 . Here, the problem of photon creation and generation of squeezed and Schroedinger covariance states in optical waveguides is solved in two steps: 1. Quantization of electromagnetic field is provided in the presence of dielectric waveguide using normal-mode expansion. The photon creation and annihilation operators are introduced, expanding the solution A-vector(r-vector,t) in a series in terms of the Sturm - Liouville mode-functions. 2. In terms of these operators the Hamiltonian of the field in a nonlinear waveguide is derived. For such Hamiltonian we construct the covariance states as stable (with nonzero covariance), which minimize the Schroedinger uncertainty relation. The evolutions of the three second momenta of q-circumflex j and p-circumflex j are calculated. For this Hamiltonian all three momenta are expressed in terms of one real parameters s only. It is found out how covariance, via this parameter s, depends on the waveguide profile n(x,y), on the mode-distributions u-vector j (x,y), and on the waveguide phase mismatching Δβ. (author). 37 refs

THz detectors using surface Josephson plasma waves in layered superconductors

International Nuclear Information System (INIS)

Savel'ev, Sergey; Yampol'skii, Valery; Nori, Franco

2006-01-01

We describe a proposal for THz detectors based on the excitation of surface waves, in layered superconductors, at frequencies lower than the Josephson plasma frequency ω J . These waves propagate along the vacuum-superconductor interface and are attenuated in both transverse directions out of the surface (i.e., towards the superconductor and towards the vacuum). The surface Josephson plasma waves are also important for the complete suppression of the specular reflection from a sample (Wood's anomalies, used for gratings) and produce a huge enhancement of the wave absorption, which can be used for the detection of THz waves

THz Wave Propagation on Strip Lines: Devices, Properties, and Applications

Directory of Open Access Journals (Sweden)

Y. Kadoya

2008-06-01

Full Text Available We report the propagation characteristics of THz pulses on micro-strip-lines and coplanar strip-lines, in which low permittivity polymer materials are used as the dielectric layer or the substrate. As a result of the low attenuation and small dispersion in the devices, the spectral width up to 3 THz can be achieved even after the 1 mm propagation. Spectroscopic characterizations of liquid or powder specimens are demonstrated using the devices. We also show a possibility of realizing a very low attenuation using a quadrupole mode in three strip coplanar lines on the polymer substrate.

Temperature resolution enhancing of commercially available THz passive cameras due to computer processing of images

Science.gov (United States)

Trofimov, Vyacheslav A.; Trofimov, Vladislav V.; Kuchik, Igor E.

2014-06-01

As it is well-known, application of the passive THz camera for the security problems is very promising way. It allows seeing concealed object without contact with a person and this camera is non-dangerous for a person. Efficiency of using the passive THz camera depends on its temperature resolution. This characteristic specifies possibilities of the detection of concealed object: minimal size of the object, maximal distance of the detection, image detail. One of probable ways for a quality image enhancing consists in computer processing of image. Using computer processing of the THz image of objects concealed on the human body, one may improve it many times. Consequently, the instrumental resolution of such device may be increased without any additional engineering efforts. We demonstrate new possibilities for seeing the clothes details, which raw images, produced by the THz cameras, do not allow to see. We achieve good quality of the image due to applying various spatial filters with the aim to demonstrate independence of processed images on math operations. This result demonstrates a feasibility of objects seeing. We consider images produced by THz passive cameras manufactured by Microsemi Corp., and ThruVision Corp., and Capital Normal University (Beijing, China).

Development of a coherent THz radiation source based on the ultra-short electron beam and its applications

International Nuclear Information System (INIS)

Kuroda, R.; Yasumoto, M.; Toyokawa, H.; Sei, N.; Koike, M.; Yamada, K.

2011-01-01

At the National Institute of Advanced Industrial Science and Technology (AIST), a coherent terahertz (THz) radiation source has been developed based on an ultra-short electron beam using an S-band compact electron linac. The designed THz pulse has a high peak power of more than 1 kW in the frequency range 0.1-2 THz. The entire system is located in one research room of about 10 m square. The linac consists of a laser photocathode rf gun (BNL type) with a Cs 2 Te photocathode load-lock system and two 1.5-m-long S-band accelerator tubes. The electron beam can be accelerated up to approximately 42 MeV. The electron bunch was compressed to less than 1 ps (rms) with a magnetic bunch compressor. The coherent synchrotron radiation (CSR) of the THz region was generated from the ultra-short electron bunch at the 90 o bending magnet, and it was extracted from a z-cut quartz window for THz applications. In this work, the THz scanning transmission imaging was successfully demonstrated for measuring the freshness of a vegetable leaf over a period of time.

Development of force-detected THz-ESR measurement system and its application to metal porphyrin complexes

Science.gov (United States)

Takahashi, Hideyuki; Okamoto, Tsubasa; Ohmichi, Eiji; Ohta, Hitoshi

Electron spin resonance spectroscopy in the terahertz region (THz-ESR) is a promising technique to study biological materials such as metalloproteins because it directly probes the metal ion sites that play an important role in the emergence of functionality. By combining THz-ESR with force detection, the samples mass is reduced to the order of ng. This feature is of great advantage because the sample preparation process of biological materials is time-consuming. We developed a force-detected THz-ESR system utilizing optical interferometry for precise cantilever displacement measurement. In order to suppress the sensitivity fluctuation and instability of cantilever dynamics under high magnetic field, the tuning of interferometer is feedback-controlled during a measurement. By using this system, we successfully observed the ESR signal of hemin, which is a model substance of hemoglobin and myoglobin, in THz region.

High Efficient THz Emission From Unbiased and Biased Semiconductor Nanowires Fabricated Using Electron Beam Lithography

Energy Technology Data Exchange (ETDEWEB)

Balci, Soner; Czaplewski, David A.; Jung, Il Woong; Kim, Ju-Hyung; Hatami, Fariba; Kung, Patrick; Kim, Seongsin Margaret

2017-07-01

Besides having perfect control on structural features, such as vertical alignment and uniform distribution by fabricating the wires via e-beam lithography and etching process, we also investigated the THz emission from these fabricated nanowires when they are applied DC bias voltage. To be able to apply a voltage bias, an interdigitated gold (Au) electrode was patterned on the high-quality InGaAs epilayer grown on InP substrate bymolecular beam epitaxy. Afterwards, perfect vertically aligned and uniformly distributed nanowires were fabricated in between the electrodes of this interdigitated pattern so that we could apply voltage bias to improve the THz emission. As a result, we achieved enhancement in the emitted THz radiation by ~four times, about 12 dB increase in power ratio at 0.25 THz with a DC biased electric field compared with unbiased NWs.

Tuning characteristics of narrowband THz radiation generated via optical rectification in periodically poled lithium niobate.

Science.gov (United States)

Weiss, C; Torosyan, G; Meyn, J P; Wallenstein, R; Beigang, R; Avetisyan, Y

2001-04-23

The tuning properties of pulsed narrowband THz radiation generated via optical rectification in periodically poled lithium niobate have been investigated. Using a disk-shaped periodically poled crystal tuning was easily accomplished by rotating the crystal around its axis and observing the generated THz radiation in forward direction. In this way no beam deflection during tuning was observed. The total tuning range extended from 180 GHz up to 830 GHz and was limited by the poling period of 127 microm which determines the maximum THz frequency in forward direction.

Study on THz wave generation from air plasma induced by quasi-square Airy beam

Science.gov (United States)

Zhang, Shijing; Zhang, Liangliang; Jiang, Guangtong; Zhang, Cunlin; Zhao, Yuejin

2018-01-01

Terahertz (THz) wave has attracted considerable attention in recent years because of its potential applications. The intense THz waves generated from air plasma induced by two-color femtosecond laser are widely used due to its high generation efficiency and broad frequency bandwidth. The parameters of the laser change the distribution of the air plasma, and then affect the generation of THz wave. In this research, we investigate the THz wave generation from air plasma induced by quasi-square Airy beam. Unlike the common Gauss beam, the quasi-square Airy beam has ability to autofocus and to increase the maximum intensity at the focus. By using the spatial light modulator (SLM), we can change the parameters of phase map to control the shape of the Airy beam. We obtain the two-color laser field by a 100-um-thick BBO crystal, then use a Golay detector to record THz wave energy. By comparing terahertz generation at different modulation depths, we find that terahertz energy produced by quasi-square Airy beam is up to 3.1 times stronger than that of Gauss beam with identical laser energy. In order to understand the influence of quasi-square Airy beam on the BBO crystal, we record THz wave energy by changing the azimuthal angle of BBO crystal with Gauss beam and Airy beam at different modulation depths. We find that the trend of terahertz energy with respect to the azimuthal angle of the BBO crystal keeps the same for different laser beams. We believe that the quasi-square Airy beam or other auto focusing beam can significantly improve the efficiency of terahertz wave generation and pave the way for its applications.

CW-THz vector spectroscopy and imaging system based on 1.55-µm fiber-optics.

Science.gov (United States)

Kim, Jae-Young; Song, Ho-Jin; Yaita, Makoto; Hirata, Akihiko; Ajito, Katsuhiro

2014-01-27

We present a continuous-wave terahertz (THz) vector spectroscopy and imaging system based on a 1.5-µm fiber optic uni-traveling-carrier photodiode and InGaAs photo-conductive receiver. Using electro-optic (EO) phase modulators for THz phase control with shortened optical paths, the system achieves fast vector measurement with effective phase stabilization. Dynamic ranges of 100 dB · Hz and 75 dB · Hz at 300 GHz and 1 THz, and phase stability of 1.5° per minute are obtained. With the simultaneous measurement of absorbance and relative permittivity, we demonstrate non-destructive analyses of pharmaceutical cocrystals inside tablets within a few minutes.

Gas phase THz spectroscopy of toxic agent simulant compounds using the AILES synchrotron beamline

Science.gov (United States)

Cuisset, A.; Smirnova, I.; Bocquet, R.; Hindle, F.; Mouret, G.; Yang, C.; Pirali, O.; Roy, P.

2010-02-01

A new study is currently underway aiming at recording and assigning the gas phase rovibrational spectra of several organophosphorus and organosulphur compounds in the THz frequency domain. Thanks to the exceptional properties of flux, brilliance and spectral range of the AILES beamline coupled to the FTIR spectrometer, the gas phase vibrational spectra of low volatility organophosphorous compounds have been recorded across the entire THz frequency range. High resolution FTIR spectroscopy was used to record the pure rotational and the low-frequency rovibrational spectrum of DMSO. A comparison between the spectra measured with the AILES beamline and the spectra obtained with optoelectronic THz sources is possible.

Nonlinear optical localization in embedded chalcogenide waveguide arrays

International Nuclear Information System (INIS)

Li, Mingshan; Huang, Sheng; Wang, Qingqing; Chen, Kevin P.; Petek, Hrvoje

2014-01-01

We report the nonlinear optical localization in an embedded waveguide array fabricated in chalcogenide glass. The array, which consists of seven waveguides with circularly symmetric cross sections, is realized by ultrafast laser writing. Light propagation in the chalcogenide waveguide array is studied with near infrared laser pulses centered at 1040 nm. The peak intensity required for nonlinear localization for the 1-cm long waveguide array was 35.1 GW/cm 2 , using 10-nJ pulses with 300-fs pulse width, which is 70 times lower than that reported in fused silica waveguide arrays and with over 7 times shorter interaction distance. Results reported in this paper demonstrated that ultrafast laser writing is a viable tool to produce 3D all-optical switching waveguide circuits in chalcogenide glass

A disorder-based strategy for tunable, broadband wave attenuation

Science.gov (United States)

Zhang, Weiting; Celli, Paolo; Cardella, Davide; Gonella, Stefano

2017-04-01

One of the most daunting limitations of phononic crystals and acoustic/elastic metamaterials is their passivity: a given configuration is bound to display its phononic properties only around its design point, i.e., working at some pre-determined operating conditions. In the past decade, this shortcoming has inspired the design of phononic media with tunable wave characteristics; noteworthy results have been obtained through a family of methodologies involving shunted piezoelectric elements. Shunting a piezoelectric element means connecting it to a passive electric circuit; tunability stems from the ability to modify the effective mechanical properties of the piezoelectric medium by modifying the circuit characteristics. One of the most popular shunting circuits is the resistor-inductor, which allows the patch-and-shunt system to behave as an electromechanical resonator. A common motif among the works employing shunted piezos for phononic control is periodicity: the patches are typically periodically placed in the domain and the circuits are identically tuned. The objective of this work is to demonstrate that the wave attenuation performance of structures with shunted piezoelectric patches can be improved by leveraging notions of organized disorder. Based on the idea of rainbow trapping broadband wave attenuation obtained by tuning an array of resonators at distinct neighboring frequencies we design and test an electromechanical waveguide structure capable of attenuating waves over broad frequency ranges. In order to emphasize the fact that periodicity is not a binding requirement when working with RL shunts (which induce locally resonant bandgaps), we report on the performance of random arrangements of patches. In an attempt to demonstrate the tunability attribute of our strategy, we take advantage of the reconfigurability of the circuits to show how a single waveguide can attenuate both waves and vibrations over different frequency ranges.

Driving demand for broadband networks and services

CERN Document Server

Katz, Raul L

2014-01-01

This book examines the reasons why various groups around the world choose not to adopt broadband services and evaluates strategies to stimulate the demand that will lead to increased broadband use. It introduces readers to the benefits of higher adoption rates while examining the progress that developed and emerging countries have made in stimulating broadband demand. By relying on concepts such as a supply and demand gap, broadband price elasticity, and demand promotion, this book explains differences between the fixed and mobile broadband demand gap, introducing the notions of substitution and complementarity between both platforms. Building on these concepts, ‘Driving Demand for Broadband Networks and Services’ offers a set of best practices and recommendations aimed at promoting broadband demand.  The broadband demand gap is defined as individuals and households that could buy a broadband subscription because they live in areas served by telecommunications carriers but do not do so because of either ...

Semiconductor plasmonic crystals : active control of THz extinction

NARCIS (Netherlands)

Schaafsma, M.C.; Gomez Rivas, J.

2013-01-01

We investigate theoretically the enhanced THz extinction by periodic arrays of semiconductor particles. Scattering particles of doped semiconductors can sustain localized surface plasmon polaritons, which can be diffractively coupled giving rise to surface lattice resonances. These resonances are

Finite-width plasmonic waveguides with hyperbolic multilayer cladding

DEFF Research Database (Denmark)

Babicheva, Viktoriia; Shalaginov, Mikhail Y.; Ishii, Satoshi

2015-01-01

Engineering plasmonic metamaterials with anisotropic optical dispersion enables us to tailor the properties of metamaterial-based waveguides. We investigate plasmonic waveguides with dielectric cores and multilayer metal-dielectric claddings with hyperbolic dispersion. Without using any homogeniz......Engineering plasmonic metamaterials with anisotropic optical dispersion enables us to tailor the properties of metamaterial-based waveguides. We investigate plasmonic waveguides with dielectric cores and multilayer metal-dielectric claddings with hyperbolic dispersion. Without using any...

Tunable photonic crystal for THz radiation in layered superconductors: Strong magnetic-field dependence of the transmission coefficient

International Nuclear Information System (INIS)

Savel'ev, Sergey; Rakhmanov, A.L.; Nori, Franco

2006-01-01

Josephson plasma waves are scattered by the Josephson vortex lattice. This scattering results in a strong dependence, on the in-plane magnetic-field H ab , of the reflection and transmission of THz radiation propagating in layered superconductors. In particular, a tunable band-gap structure (THz photonic crystal) occurs in such a medium. These effects can be used, by varying H ab , for the selective frequency-filtering of THz radiation

Multilayer cladding with hyperbolic dispersion for plasmonic waveguides

DEFF Research Database (Denmark)

Babicheva, Viktoriia; Shalaginov, Mikhail Y.; Ishii, Satoshi

2015-01-01

We study the properties of plasmonic waveguides with a dielectric core and multilayer metal-dielectric claddings that possess hyperbolic dispersion. The waveguides hyperbolic multilayer claddings show better performance in comparison to conventional plasmonic waveguides. © OSA 2015....

Ultrabroadband terahertz conductivity of highly doped ZnO and ITO

DEFF Research Database (Denmark)

Wang, Tianwu; Zalkovskij, Maksim; Iwaszczuk, Krzysztof

2015-01-01

The broadband complex conductivities of transparent conducting oxides (TCO), namely aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO) and tin-doped indium oxide (ITO), were investigated by terahertz time domain spectroscopy (THz-TDS) in the frequency range from 0.5 to 18 THz using air...... to be more thickness dependent than GZO and ITO, indicating high importance of the surface states for electron dynamics in AZO. Finally, we measure the transmittance of the TCO films from 10 to 200 THz with Fourier transform infrared spectroscopy (FTIR) measurements, thus closing the gap between THz...

Broadband Rotational Spectroscopy

Science.gov (United States)

Pate, Brooks

2014-06-01

The past decade has seen several major technology advances in electronics operating at microwave frequencies making it possible to develop a new generation of spectrometers for molecular rotational spectroscopy. High-speed digital electronics, both arbitrary waveform generators and digitizers, continue on a Moore's Law-like development cycle that started around 1993 with device bandwidth doubling about every 36 months. These enabling technologies were the key to designing chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers which offer significant sensitivity enhancements for broadband spectrum acquisition in molecular rotational spectroscopy. A special feature of the chirped-pulse spectrometer design is that it is easily implemented at low frequency (below 8 GHz) where Balle-Flygare type spectrometers with Fabry-Perot cavity designs become technologically challenging due to the mirror size requirements. The capabilities of CP-FTMW spectrometers for studies of molecular structure will be illustrated by the collaborative research effort we have been a part of to determine the structures of water clusters - a project which has identified clusters up to the pentadecamer. A second technology trend that impacts molecular rotational spectroscopy is the development of high power, solid state sources in the mm-wave/THz regions. Results from the field of mm-wave chirped-pulse Fourier transform spectroscopy will be described with an emphasis on new problems in chemical dynamics and analytical chemistry that these methods can tackle. The third (and potentially most important) technological trend is the reduction of microwave components to chip level using monolithic microwave integrated circuits (MMIC) - a technology driven by an enormous mass market in communications. Some recent advances in rotational spectrometer designs that incorporate low-cost components will be highlighted. The challenge to the high-resolution spectroscopy community - as posed by Frank De

Matrix method for two-dimensional waveguide mode solution

Science.gov (United States)

Sun, Baoguang; Cai, Congzhong; Venkatesh, Balajee Seshasayee

2018-05-01

In this paper, we show that the transfer matrix theory of multilayer optics can be used to solve the modes of any two-dimensional (2D) waveguide for their effective indices and field distributions. A 2D waveguide, even composed of numerous layers, is essentially a multilayer stack and the transmission through the stack can be analysed using the transfer matrix theory. The result is a transfer matrix with four complex value elements, namely A, B, C and D. The effective index of a guided mode satisfies two conditions: (1) evanescent waves exist simultaneously in the first (cladding) layer and last (substrate) layer, and (2) the complex element D vanishes. For a given mode, the field distribution in the waveguide is the result of a 'folded' plane wave. In each layer, there is only propagation and absorption; at each boundary, only reflection and refraction occur, which can be calculated according to the Fresnel equations. As examples, we show that this method can be used to solve modes supported by the multilayer step-index dielectric waveguide, slot waveguide, gradient-index waveguide and various plasmonic waveguides. The results indicate the transfer matrix method is effective for 2D waveguide mode solution in general.

Sharp Absorption Peaks in THz Spectra Valuable for Crystal Quality Evaluation of Middle Molecular Weight Pharmaceuticals

Science.gov (United States)

Sasaki, Tetsuo; Sakamoto, Tomoaki; Otsuka, Makoto

2018-05-01

Middle molecular weight (MMW) pharmaceuticals (MW 400 4000) are attracting attention for their possible use in new medications. Sharp absorption peaks were observed in MMW pharmaceuticals at low temperatures by measuring with a high-resolution terahertz (THz) spectrometer. As examples, high-resolution THz spectra for amoxicillin trihydrate, atorvastatin calcium trihydrate, probucol, and α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin p-toluenesulfonate (TMPyP) were obtained at 10 K. Typically observed as peaks with full width at half-height (FWHM) values as low as 5.639 GHz at 0.96492 THz in amoxicillin trihydrate and 8.857 GHz at 1.07974 THz for probucol, many sharp peaks of MMW pharmaceuticals could be observed. Such narrow absorption peaks enable evaluation of the crystal quality of MMW pharmaceuticals and afford sensitive detection of impurities.

Recent progress in synchrotron-based frequency-domain Fourier-transform THz-EPR.

Science.gov (United States)

Nehrkorn, Joscha; Holldack, Karsten; Bittl, Robert; Schnegg, Alexander

2017-07-01

We describe frequency-domain Fourier-transform THz-EPR as a method to assign spin-coupling parameters of high-spin (S>1/2) systems with very large zero-field splittings. The instrumental foundations of synchrotron-based FD-FT THz-EPR are presented, alongside with a discussion of frequency-domain EPR simulation routines. The capabilities of this approach is demonstrated for selected mono- and multinuclear HS systems. Finally, we discuss remaining challenges and give an outlook on the future prospects of the technique. Copyright © 2017 Elsevier Inc. All rights reserved.

Guided modes of elliptical metamaterial waveguides

International Nuclear Information System (INIS)

Halterman, Klaus; Feng, Simin; Overfelt, P. L.

2007-01-01

The propagation of guided electromagnetic waves in open elliptical metamaterial waveguide structures is investigated. The waveguide contains a negative-index media core, where the permittivity ε and permeability μ are negative over a given bandwidth. The allowed mode spectrum for these structures is numerically calculated by solving a dispersion relation that is expressed in terms of Mathieu functions. By probing certain regions of parameter space, we find the possibility exists to have extremely localized waves that transmit along the surface of the waveguide