WorldWideScience

Sample records for broadband thz waveguiding

  1. Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

    DEFF Research Database (Denmark)

    Bao, Hualong; Nielsen, Kristian; Bang, Ole;

    2015-01-01

    verify our findings. The proposed THz waveguide is robust, insensitive to external perturbation and easy to handle, and thus the design represents a significant advance of the field of THz dielectric waveguides suitable for the 0.3-1 THz band which in the future will be important for ultrafast wireless...

  2. Broadband THz waveguiding and high-precision broadband time-resolved spectroscopy

    DEFF Research Database (Denmark)

    Cooke, David; Iwaszczuk, Krzysztof; Nielsen, Kristian;

    2009-01-01

    , particularly in spectroscopic applications where tight confinement of the THz field is required. We further demonstrate a new spectroscopic technique for ultrafast time-resolved THz time-domain spectroscopy which simultaneously acquires both reference and sample data. By using this scheme we show...... that the influence of fluctuations on the laser parameters during data acquisition can be minimized, and highly reproducible quantitative data can be recorded and extracted in a very efficient manner. This technique may become especially important in the high THz range, where phase noise becomes critical...

  3. A Broadband Terahertz Waveguide T-Junction Variable Power Splitter

    Science.gov (United States)

    Reichel, Kimberly S.; Mendis, Rajind; Mittleman, Daniel M.

    2016-06-01

    In order for the promise of terahertz (THz) wireless communications to become a reality, many new devices need to be developed, such as those for routing THz waves. We demonstrate a power splitting router based on a parallel-plate waveguide (PPWG) T-junction excited by the TE1 waveguide mode. By integrating a small triangular septum into the waveguide plate, we are able to direct the THz light down either one of the two output channels with precise control over the ratio between waveguide outputs. We find good agreement between experiment and simulation in both amplitude and phase. We show that the ratio between waveguide outputs varies exponentially with septum translation offset and that nearly 100% transmission can be achieved. The splitter operates over almost the entire range in which the waveguide is single mode, providing a sensitive and broadband method for THz power splitting.

  4. A Broadband Terahertz Waveguide T-Junction Variable Power Splitter.

    Science.gov (United States)

    Reichel, Kimberly S; Mendis, Rajind; Mittleman, Daniel M

    2016-06-29

    In order for the promise of terahertz (THz) wireless communications to become a reality, many new devices need to be developed, such as those for routing THz waves. We demonstrate a power splitting router based on a parallel-plate waveguide (PPWG) T-junction excited by the TE1 waveguide mode. By integrating a small triangular septum into the waveguide plate, we are able to direct the THz light down either one of the two output channels with precise control over the ratio between waveguide outputs. We find good agreement between experiment and simulation in both amplitude and phase. We show that the ratio between waveguide outputs varies exponentially with septum translation offset and that nearly 100% transmission can be achieved. The splitter operates over almost the entire range in which the waveguide is single mode, providing a sensitive and broadband method for THz power splitting.

  5. A Broadband Terahertz Waveguide T-Junction Variable Power Splitter

    Science.gov (United States)

    Reichel, Kimberly S.; Mendis, Rajind; Mittleman, Daniel M.

    2016-01-01

    In order for the promise of terahertz (THz) wireless communications to become a reality, many new devices need to be developed, such as those for routing THz waves. We demonstrate a power splitting router based on a parallel-plate waveguide (PPWG) T-junction excited by the TE1 waveguide mode. By integrating a small triangular septum into the waveguide plate, we are able to direct the THz light down either one of the two output channels with precise control over the ratio between waveguide outputs. We find good agreement between experiment and simulation in both amplitude and phase. We show that the ratio between waveguide outputs varies exponentially with septum translation offset and that nearly 100% transmission can be achieved. The splitter operates over almost the entire range in which the waveguide is single mode, providing a sensitive and broadband method for THz power splitting. PMID:27352772

  6. A Broadband Terahertz Waveguide T-Junction Variable Power Splitter.

    Science.gov (United States)

    Reichel, Kimberly S; Mendis, Rajind; Mittleman, Daniel M

    2016-01-01

    In order for the promise of terahertz (THz) wireless communications to become a reality, many new devices need to be developed, such as those for routing THz waves. We demonstrate a power splitting router based on a parallel-plate waveguide (PPWG) T-junction excited by the TE1 waveguide mode. By integrating a small triangular septum into the waveguide plate, we are able to direct the THz light down either one of the two output channels with precise control over the ratio between waveguide outputs. We find good agreement between experiment and simulation in both amplitude and phase. We show that the ratio between waveguide outputs varies exponentially with septum translation offset and that nearly 100% transmission can be achieved. The splitter operates over almost the entire range in which the waveguide is single mode, providing a sensitive and broadband method for THz power splitting. PMID:27352772

  7. Broadband terahertz transmission within the symmetrical plastic film coated parallel-plate waveguide.

    Science.gov (United States)

    Liu, Jiamin; Liang, Huawei; Zhang, Min; Su, Hong

    2014-09-10

    We report on the broadband terahertz (THz) transmission within a symmetrical plastic film coated parallel-plate waveguide. We theoretically study the antiresonant reflecting mechanism of the waveguide, and we find that the broadband THz wave can transmit in this waveguide with ultralow loss. The loss of the TM mode in this waveguide can be 4 orders of magnitude lower than the uncoated parallel-plate waveguide. The transmission bandwidth of this waveguide is up to 5.12 THz. We further show the mode field distributions which explain the loss mechanism.

  8. Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics

    DEFF Research Database (Denmark)

    D’Angelo, Francesco; Mics, Zoltán; Bonn, Mischa;

    2014-01-01

    -domain spectrometer employing air-photonics for the generation and detection of single-cycle sub-50 fs THz transients. The time domain measurements provide direct access to both the absorption and refractive index spectra. The polymers LDPE and TOPAS® demonstrate negligible absorption and spectrally-flat refractive...... index across the entire spectroscopy window, revealing the high potential of these polymers for applications in THz photonics such as ultra-broadband polymer-based dielectric mirrors, waveguides, and fibers. Resonant high-frequency polar vibrational modes are observed and assigned in polymers PA6...... and PTFE, and their dielectric functions in the complete frequency window 2-15 THz are theoretically reproduced. Our results demonstrate the potential of ultrabroadband air-photonics-based THz time domain spectroscopy as a valuable analytic tool for materials science....

  9. A Broadband Dipolar Resonance in THz Metamaterials

    CERN Document Server

    Sangala, Bagvanth Reddy; Gopal, Achanta Venu; Prabhu, S S

    2014-01-01

    We demonstrate a THz metamaterial with broadband dipole resonance originating due to the hybridization of LC resonances. The structure optimized by finite element method simulations is fabricated by electron beam lithography and characterized by terahertz time-domain spectroscopy. Numerically, we found that when two LC metamaterial resonators are brought together, an electric dipole resonance arises in addition to the LC resonances. We observed a strong dependence of the width of these resonances on the separation between the resonators. This dependence can be explained based on series and parallel RLC circuit analogies. The broadband dipole resonance appears when both the resonators are fused together. The metamaterial has a stopband with FWHM of 0.47 THz centered at 1.12 THz. The experimentally measured band features are in reasonable agreement with the simulated ones. The experimental power extinction ratio of THz in the stopbands is found to be 15 dB.

  10. 15-THz Tunable Wavelength Conversion of Picosecond Pulses in a Silicon Waveguide

    DEFF Research Database (Denmark)

    Pu, Minhao; Hu, Hao; Galili, Michael;

    2011-01-01

    We demonstrate all-optical ultra-broadband tunable wavelength conversion of 1-ps pulses based on four-wave mixing in a 3-mm-long dispersion engineered silicon waveguide. In the waveguide, an input pulse with center wavelength at 1600 nm is down-converted by 135 nm (17.3 THz) to 1465 nm. A tuning...

  11. Broadband polymer microstructured THz fiber coupler with downdoped cores

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Bang, Ole;

    2010-01-01

    We demonstrate a broadband THz directional coupler based on a dual core photonic crystal fiber (PCF) design with mechanically down-doped core regions. For a center frequency of 1.3 THz we demonstrate a bandwidth of 0.65 THz.......We demonstrate a broadband THz directional coupler based on a dual core photonic crystal fiber (PCF) design with mechanically down-doped core regions. For a center frequency of 1.3 THz we demonstrate a bandwidth of 0.65 THz....

  12. Transmission of THz wave by liquid dielectric waveguide

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The absorption and dispersion of several non-polar organic solvents from 0.2 to 2.5 THz are measured with the method of time-domain spectroscopy.Based on the result,we believe that liquid paraffin might be a proper choice for liquid dielectric waveguide.Transmitting performance of THz liquid dielectric waveguide at 98 GHz is tested.

  13. Quantitative study of rectangular waveguide behavior in the THz.

    Energy Technology Data Exchange (ETDEWEB)

    Rowen, Adam M.; Nordquist, Christopher Daniel; Wanke, Michael Clement

    2009-10-01

    This report describes our efforts to quantify the behavior of micro-fabricated THz rectangular waveguides on a configurable, robust semiconductor-based platform. These waveguides are an enabling technology for coupling THz radiation directly from or to lasers, mixers, detectors, antennas, and other devices. Traditional waveguides fabricated on semiconductor platforms such as dielectric guides in the infrared or co-planar waveguides in the microwave regions, suffer high absorption and radiative losses in the THz. The former leads to very short propagation lengths, while the latter will lead to unwanted radiation modes and/or crosstalk in integrated devices. This project exploited the initial developments of THz micro-machined rectangular waveguides developed under the THz Grand Challenge Program, but instead of focusing on THz transceiver integration, this project focused on exploring the propagation loss and far-field radiation patterns of the waveguides. During the 9 month duration of this project we were able to reproduce the waveguide loss per unit of length in the waveguides and started to explore how the loss depended on wavelength. We also explored the far-field beam patterns emitted by H-plane horn antennas attached to the waveguides. In the process we learned that the method of measuring the beam patterns has a significant impact on what is actually measured, and this may have an effect on most of the beam patterns of THz that have been reported to date. The beam pattern measurements improved significantly throughout the project, but more refinements of the measurement are required before a definitive determination of the beam-pattern can be made.

  14. 3D-Printed Broadband Dielectric Tube Terahertz Waveguide with Anti-Reflection Structure

    Science.gov (United States)

    Vogt, Dominik Walter; Leonhardt, Rainer

    2016-07-01

    We demonstrate broadband, low loss, and close-to-zero dispersion guidance of terahertz (THz) radiation in a dielectric tube with an anti-reflection structure (AR-tube waveguide) in the frequency range from 0.2 to 1.0 THz. The anti-reflection structure (ARS) consists of close-packed cones in a hexagonal lattice arranged on the outer surface of the tube cladding. The feature size of the ARS is in the order of the wavelength between 0.2 and 1.0 THz. The waveguides are fabricated with the versatile and cost efficient 3D-printing method. Terahertz time-domain spectroscopy (THz-TDS) measurements as well as 3D finite-difference time-domain simulations (FDTD) are performed to extensively characterize the AR-tube waveguides. Spectrograms, attenuation spectra, effective phase refractive indices, and the group-velocity dispersion parameters β 2 of the AR-tube waveguides are presented. Both the experimental and numerical results confirm the extended bandwidth and smaller group-velocity dispersion of the AR-tube waveguide compared to a low loss plain dielectric tube THz waveguide. The AR-tube waveguide prototypes show an attenuation spectrum close to the theoretical limit given by the infinite cladding tube waveguide.

  15. Broadband Waveguide QED System on a Chip

    OpenAIRE

    Quan, Qimin; Bulu, Irfan; Loncar, Marko

    2009-01-01

    We demonstrate that a slot waveguide provides a broadband loss-free platform suitable for applications in quantum optics. We find that strong coupling between light quanta and a single quantum emitter placed in the waveguide slot can be achieved with efficiency higher than 96% and Purcell factor (spontaneous emission factor) larger than 200. The proposed system is a promising platform for quantum information processing and can be used to realize an efficient single photon source and optically...

  16. Time-resolved THz spectroscopy in a parallel plate waveguide

    DEFF Research Database (Denmark)

    Cooke, David; Jepsen, Peter Uhd

    2009-01-01

    We demonstrate time-resolved terahertz spectroscopy inside a novel parallel plate waveguide where one of the metallic plates is replaced by a transparent conducting oxide. Considerable improvements to the waveguide loss coefficient are shown, with a power absorption coefficient of 4cm-1 at 0.5 THz....... The time resolution of the technique is shown to be limited by the spatial excitation profile, which for sharply focused beams can approach ~1 ps time scales....

  17. Chemical recognition with broadband THz spectroscopy

    DEFF Research Database (Denmark)

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

    2004-01-01

    contains unique fingerprints of a very large number of crystalline materials, including explosives, illicit drugs as well as most other chemicals in powder form. Since many packaging materials are transparent to THz radiation this fundamental property of crystalline compounds allows remote (contact...

  18. Quasi-TEM mode propagation in twin-wire THz waveguides

    Institute of Scientific and Technical Information of China (English)

    P. Tannouri; M. Peccianti; P. L. Lavertu; F. Vidal; R. Morandotti

    2011-01-01

    Terahertz (THz) bandwidth has been attracting much interest in material characterization,owing to its demonstrated advantages in probing and recognizing different materials,for various potential applications in fields spanning from biology to security.These applications rely on the free space propagation of broadband singlecycle THz pulses,which enables time-domain spectroscopy (TDS),capable of retrieving the amplitude and phase information of the spectral signature of various compounds[11.One of the recent challenges on the topic is the development of practical waveguides that are capable of transporting this signal to arbitrary locations.%We numerically investigate the trade-offs between the dispersion properties, coupling efficiency, and geometrical constraints in dual-wire (twin-lead) terahertz (THz) waveguides. In particular, we show that their inherent linearly polarized quasi-transverse electromagnetic (TEM) modes exist for waveguide transverse dimensions comparable with the wavelength, enabling significant end-fire coupling (>10%) for numerical-aperture limited Gaussian beams while supporting a relatively low-dispersion propagation of below 0.5 ps2/m, as desired for short-pulse time-domain spectroscopy applications. Starting from the dual-wire structure, we also demonstrate that low-dispersion tapers can be designed to improve coupling efficiency.

  19. Fibre laser based broadband THz imaging systems

    DEFF Research Database (Denmark)

    Eichhorn, Finn

    State-of-the-art optical fiber technology can contribute towards complex multi-element broadband terahertz imaging systems. Classical table-top terahertz imaging systems are generally limited to a single emitter/receiver pair, which constrains their imaging capability to tedious raster scanning i...

  20. 1 THz Micromachined Waveguide Band-Pass Filter

    Science.gov (United States)

    Liu, Shuang; Hu, Jiang; Zhang, Yong; Zheng, Zhongwan; Liu, Yupeng; Xu, Ruimin; Xue, Quan

    2016-05-01

    This paper presents a waveguide band-pass filter operating at the 0.75 ˜ 1.1 THz frequency band. The metal conductivity, the surface impedance, and the skin depth are investigated in the terahertz (THz) frequency band for more accurate designs, especially at the 1 THz and higher frequencies. Because the influence of the fabrication tolerance on the component performance cannot be negligible while the frequency increases, it is a necessary to adopt the simple structure with less resonant cavities for obtaining the given performance. Therefore, the filter in this paper is designed based on the TE301/TE102 dual-mode rectangular waveguide resonant cavities, which has fewer cavities and better rejection of the stop-band. The proposed filter is fabricated using the deep reactive ion etching (DRIE) micromachining technique. Measured results are in good agreement with simulations, which verifies the accuracy of the analysis above, and the design process is valuable to realize high-performance passive components while the frequency is up to 1 THz or higher frequencies.

  1. ALL-OPTICAL CONTROL OF THZ RADIATION IN PARALLEL PLATE WAVEGUIDES

    DEFF Research Database (Denmark)

    2010-01-01

    The invention relates to control of THz radiation in parallel plate waveguides (PPWG) by forming components in the waveguide by use of optical radiation pulses. Patterns of excited regions induced in the PPWG by an optical excitation pulses changes the electromagnetic properties of the waveguide...... medium in the THz regime, thereby forming transient passive and active components for controlling THz radiation signals. The excitation can be generation of free charge carriers in a semiconductor material in the PPWG, to create metallic regions that form mirrors, lenses or photonic crystal structures......-on-a-chip applications. The optical and THz radiation can be ultrashort pulses with picosecond or femtosecond pulse durations. L...

  2. Broadband high reflectivity in subwavelength-grating slab waveguides

    CERN Document Server

    Cui, Xuan; Zhou, Zhongxiang

    2015-01-01

    We computationally study a subwavelength dielectric grating structure, show that slab waveguide modes can be used to obtain broadband high reflectivity, and analyze how slab waveguide modes influence reflection. A structure showing interference between Fabry-Perot modes, slab waveguide modes, and waveguide array modes is designed with ultra-broadband high reflectivity. Owing to the coupling of guided modes, the region with reflectivity R > 0.99 has an ultra-high bandwidth ( {\\Delta}f/f > 30%). The incident-angle region with R > 0.99 extends over a range greater than 40{\\deg}. Moreover, an asymmetric waveguide structure is studied using a semiconductor substrate.

  3. 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....

  4. Experimental Characterization of Extremely Broadband THz Impulse Radio Communication Systems

    DEFF Research Database (Denmark)

    Yu, Xianbin; Vidal, Borja; Galili, Michael;

    2015-01-01

    We experimentally characterize a ultrabroadband terahertz (THz) impulse radio system with up to 10 GHz repetition rate. THz generation and radiation are realized in an antenna-integrated uni-traveling-carrier photodiode (UTC-PD), and THz reception is implemented based on photoconductive sampling ...

  5. Broadband line imaging with subwavelength resolution using plasmonic waveguides

    OpenAIRE

    Podoliak, N.; Horak, P.; Prangsma, J.C.; Pinkse, P.W.H.

    2015-01-01

    In this paper we design a high-resolution line imaging device allowing for broadband operation at near-infrared wavelengths ranging from 1 ?m to 2 ?m utilizing the advantage of subwavelength light confinement in plasmonic waveguides. The device consists of an array of air-guided plasmonic waveguides in gold with fanned-out geometry. In the main part of the device the separation between waveguides increases gradually from the input towards the output. High resolution is achieved on the input s...

  6. Study of broadband THz time-domain spectroscopy at different relative humidity levels

    Institute of Scientific and Technical Information of China (English)

    Chiajen Lin; Ichen Ho; X. C. Zhang

    2012-01-01

    Two detection techniques of broadband terahertz (THz) time-domain spectroscopy-THz air-biased coherent detection (THz-ABCD; from 0.3 to 14 THz) and electro-optical (EO) detection (from 0.3 to 7 THz) - are both performed at several different relative humidity levels.The THz power exponentially decays with the increase in relative humidity.The dynamic range of the main pulse in the time domain linearly decreases as the relative humidity increases from 0% to 40%,and linear fittings show that the slopes are -0.017 and -0.019 for THz-ABCD and EO detection,respectively.Because of the multiple reflections caused by the crystal in the common EO detection,THz-ABCD has better spectral resolution (17 GHz) than that of EO detection (170 GHz).The spectrum of water vapor absorption measured by THz-ABCD is also compared with that measured by the Fourier transform infrared spectroscopy (FTIR).

  7. 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...

  8. Simple Broadband Circular Polarizer in Oversized Waveguide

    Science.gov (United States)

    Stange, Torsten

    2016-02-01

    In this paper, a possibility is shown to realize a simple waveguide polarizer producing nearly the same circular polarization over a broad frequency range up to an octave. It is based upon the combination of two smoothly squeezed oversized waveguides with different diameters. The principle is similar to an achromatic lens in optics, where two counteracting lenses with differently sloped wavelength dependencies of the refractive index are combined to compensate the dispersion in the desired wavelength range. Consequently, two different wavelengths of light are brought into focus at the same plane. A waveguide for the transmission of microwaves has a similar frequency dependence of the refractive index resulting in a frequency-dependent phase shift between two propagating waves polarized along the symmetry axes of a waveguide with an elliptical cross section. For this reason, an incident wave with a linear polarization between the axes of symmetry can be only converted into a circularly polarized wave over a limited frequency range. However, the diameter and the shape along two counteracting squeezed waveguides can be adjusted in such a way that the frequency dependence of the resultant phase shift is finally canceled out.

  9. Silver-Coated Teflon Tubes for Waveguiding at 1-2 THz

    Science.gov (United States)

    Navarro-Cía, Miguel; Melzer, Jeffrey E.; Harrington, James A.; Mitrofanov, Oleg

    2015-06-01

    Realization of single-mode low-loss waveguides for 1.0-2.0 THz remains a challenging problem due to large absorption in most dielectrics and ohmic losses in metals. To address this problem, we investigate dielectric-lined hollow metallic waveguides fabricated by coating 1-mm diameter 38-μm-thick polytetrafluoroethylene tubes with silver. These waveguides support a hybrid HE11 mode, which exhibits low attenuation and low dispersion. Quasi-single-mode propagation is achieved in the band of 1.0-1.6 THz, in which the hybrid HE11 mode is supported by the waveguide. In this band, the experimentally measured loss is ~20 dB/m (~0.046 cm-1), whereas the numerically computed loss is ~7 dB/m (~0.016 cm-1). The difference is attributed to additional losses in the dielectric layer, which can be reduced by using alternative polymers.

  10. Aligned copper nanorod arrays for highly efficient generation of intense ultra-broadband THz pulses

    CERN Document Server

    Mondal, S; Ding, W J; Hafez, H A; Fareed, M A; Laramée, A; Ropagnol, X; Zhang, G; Sun, S; Sheng, Z M; Zhang, J; Ozaki, T

    2016-01-01

    We demonstrate an intense broadband terahertz (THz) source based on the interaction of relativistic-intensity femtosecond lasers with aligned copper nanorod array targets. For copper nanorod targets with length 5 \\mu m, a maximum 13.8 times enhancement in the THz pulse energy (in $\\leq$ 20 THz spectral range) is measured as compared to that with a thick plane copper target under the same laser conditions. A further increase in the nanorod length leads to a decrease in the THz pulse energy at medium frequencies ($\\leq$ 20THz) and increase of the electromagnetic pulse energy in the high-frequency range (from 20 - 200 THz). For the latter, we measure a maximum energy enhancement of 28 times for the nanorod targets of length 60 \\mu m . Particle-in-cell simulations reveal that THz pulses are mostly generated by coherent transition radiation of laser produced hot electrons, which are efficiently enhanced with the use of nanorod targets. Good agreement is found between the simulation and experimental results.

  11. Broadband waveguide quantum memory for entangled photons

    CERN Document Server

    Saglamyurek, Erhan; Jin, Jeongwan; Slater, Joshua A; Oblak, Daniel; Bussieres, Felix; George, Mathew; Ricken, Raimund; Sohler, Wolfgang; Tittel, Wolfgang

    2010-01-01

    The reversible transfer of quantum states of light in and out of matter constitutes an important building block for future applications of quantum communication: it allows synchronizing quantum information, and enables one to build quantum repeaters and quantum networks. Much effort has been devoted worldwide over the past years to develop memories suitable for the storage of quantum states. Of central importance to this task is the preservation of entanglement, a quantum mechanical phenomenon whose counter intuitive properties have occupied philosophers, physicists and computer scientists since the early days of quantum physics. Here we report, for the first time, the reversible transfer of photon-photon entanglement into entanglement between a photon and collective atomic excitation in a solid-state device. Towards this end, we employ a thulium-doped lithium niobate waveguide in conjunction with a photon-echo quantum memory protocol, and increase the spectral acceptance from the current maximum of 100 MHz t...

  12. The source of THz radiation based on dielectric waveguide excited by sequence of electron bunches

    Science.gov (United States)

    Altmark, A. M.; Kanareykin, A. D.

    2016-07-01

    We present a new method for excitation of THz Cherenkov radiation in a dielectric waveguide by relativistic electron bunches. A sequence of bunches generates monochromatic radiation. The frequency of radiation is defined by the distance between the bunches. The studies were carried by using the newly updated BBU-3000 code which permits taking into account a number of additional options: an external quadrupole focusing system, group velocity of the wakefield, and the dielectric material loss factor. In this paper, we present our algorithm for optimizing the number and sequential positions of bunches for generation of narrow band high power THz radiation.

  13. Tunable THz radiation source from dielectric loaded waveguide excited by nonrelativistic electron bunch trains

    Science.gov (United States)

    Li, Weiwei; He, Zhigang; Lu, Yalin; Huang, Ruixuan; Liu, Weihao; Jia, Qika; Wang, Lin

    2016-10-01

    We propose a novel scheme to generate a tunable narrow-band THz radiation. In this scheme, a train of laser pulses with THz repetition rate is used to drive a photocathode direct current (DC) gun, leading to the emission of a train of electron bunches. The electron bunch train is subsequently accelerated by the gun field and applied to selectively excite one of the modes in the dielectric loaded waveguide (DLW) structure, which is located downstream the DC gun. Thanks to the tunability of the repetition rate of laser pulses and the gun voltage, a tunable narrow-band THz radiation source can be obtained. This proposed source has the advantages of compactness, robustness and relatively high power.

  14. A broadband THz receiver for low background space applications

    Science.gov (United States)

    Hagmann, C.; Benford, D. J.; Clapp, A. C.; Richards, P. L.; Timbie, P.

    We have developed a sensitive bolometric receiver for low background space applications. In a 10 percent bandwidth at 1 THz, this receiver is approximately 100 times more sensitive than a quantum limited heterodyne receiver with a 1 GHz IF bandwidth. This receiver is designed to be used for the long wavelength band (200-700 microns) in the MIPS instrument on NASA's SIRTF satellite. The bolometers are cooled to 100 mK by an adiabatic demagnetization refrigerator. Roughly 60 g of cesium chrome alum salt is partially demagnetized to 100 mK, followed by a slow regulated downramp to compensate for the heat leak. The hold time of the ADR system is about 18 hours with a temperature stability of delta T(sub rms) approx. equals 10 micro-K. The composite bolometers have electrical responsivities of 10(exp 9)V/W and electrical NEP's of about 3x10(exp -17) W/square root of Hz. The bolometer signals are read out by JFET preamplifiers located on the helium plate and operated at 120 K. We have addressed a number of space qualification issues, such as the development of an analog magnet controller, construction of a cryogenic shake-table for bolometers and selection of the paramagnetic salt CCA which can survive a bakeout at 50 C. The receiver is scheduled to be flown in the spring of 1992 on a balloon telescope. This flight has a dual purpose. One is to provide realistic test of the capabilities of the new receiver. The other is to search for anisotropies in the cosmic microwave background on scales of a few degrees.

  15. A Study of Electron and Phonon Dynamics by Broadband Two-Dimensional THz Time-Domain Spectroscopy

    Science.gov (United States)

    Fu, Zhengping

    Terahertz (THz) wave interacts with semiconductors in many ways, such as resonant excitation of lattice vibration, intraband transition and polaron formation. Different from the optical waves, THz wave has lower photon energy (1 THz = 4.14 meV) and is suitable for studying dynamics of low-energy excitations. Recently the studies of the interaction of THz wave and semiconductors have been extending from the linear regime to the nonlinear regime, owing to the advance of the high-intensity THz generation and detection methods. Two-dimensional (2D) spectroscopy, as a useful tool to unravel the nonlinearity of materials, has been well developed in nuclear magnetic resonance and infrared region. However, the counterpart in THz region has not been well developed and was only demonstrated at frequency around 20 THz due to the lack of intense broadband THz sources. Using laser-induced plasma as the THz source, we developed collinear broadband 2D THz time-domain spectroscopy covering from 0.5 THz to 20 THz. Broadband intense THz pulses emitted from laser-induced plasma provide access to a variety of nonlinear properties of materials. Ultrafast optical and THz pulses make it possible to resolve the transient change of the material properties with temporal resolution of tens of femtoseconds. This thesis focuses on the linear and nonlinear interaction of the THz wave with semiconductors. Since a great many physical processes, including vibrational motion of lattice and plasma oscillation, has resonant frequency in the THz range, rich physics can be studies in our experiment. The thesis starts from the linear interaction of the THz wave with semiconductors. In the narrow band gap semiconductor InSb, the plasma absorption edge, Restrahlen band and dispersion of polaritons are observed. The nonlinear response of InSb in high THz field is verified in the frequency-resolved THz Z-scan experiment. The third harmonic generations due to the anharmonicity of plasma oscillation and the

  16. Experimental and theoretical analysis of THz-frequency, direction-dependent, phonon polariton modes in a subwavelength, anisotropic slab waveguide.

    Science.gov (United States)

    Yang, Chengliang; Wu, Qiang; Xu, Jingjun; Nelson, Keith A; Werley, Christopher A

    2010-12-01

    Femtosecond optical pulses were used to generate THz-frequency phonon polariton waves in a 50 micrometer lithium niobate slab, which acts as a subwavelength, anisotropic planar waveguide. The spatial and temporal electric field profiles of the THz waves were recorded for different propagation directions using a polarization gating imaging system, and experimental dispersion curves were determined via a two-dimensional Fourier transform. Dispersion relations for an anisotropic slab waveguide were derived via analytical analysis and found to be in excellent agreement with all observed experimental modes. From the dispersion relations, we analyze the propagation-direction-dependent behavior, effective refractive index values, and generation efficiencies for THz-frequency modes in the subwavelength, anisotropic slab waveguide. PMID:21164986

  17. 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...... fabrication process, and a cascade architecture of the backward wave amplifier are discussed. New knowledge in the field of terahertz vacuum devices brought by intensive simulations and development of advanced fabrication and assembly processes of the micro-structures is highlighted....

  18. 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. PMID:27409928

  19. Wedge hybrid plasmonic THz waveguide with long propagation length and ultra-small deep-subwavelength mode area.

    Science.gov (United States)

    Gui, Chengcheng; Wang, Jian

    2015-01-01

    We present a novel design of wedge hybrid plasmonic terahertz (THz) waveguide consisting of a silicon (Si) nanowire cylinder above a triangular gold wedge with surrounded high-density polyethylene as cladding. It features long propagation length and ultra-small deep-subwavelength mode confinement. The mode properties of wedge hybrid plasmonic THz waveguide are comprehensively characterized in terms of propagation length (L), normalized mode area (Aeff/A0), figure of merit (FoM), and chromatic dispersion (D). The designed wedge hybrid plasmonic THz waveguide enables an ultra-small deep-subwavelength mode area which is more than one-order of magnitude smaller compared to previous rectangular one. When choosing the diameter of Si nanowire cylinder, a smaller diameter (e.g. 10 μm) is preferred to achieve longer L and higher FoM, while a larger diameter (e.g. 60 μm) is favorable to obtain smaller Aeff/A0 and higher FoM. We further study the impacts of possible practical fabrication errors on the mode properties. The simulated results of propagation length and normalized mode area show that the proposed wedge hybrid plasmonic THz waveguide is tolerant to practical fabrication errors in geometry parameters such as misalignment in the horizontal direction, variation of wedge tip angle, and variation of wedge tip curvature radius. PMID:26155782

  20. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization.

    Science.gov (United States)

    Sidabras, Jason W; Strangeway, Robert A; Mett, Richard R; Anderson, James R; Mainali, Laxman; Hyde, James S

    2016-03-01

    Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE10 mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in

  1. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization.

    Science.gov (United States)

    Sidabras, Jason W; Strangeway, Robert A; Mett, Richard R; Anderson, James R; Mainali, Laxman; Hyde, James S

    2016-03-01

    Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE10 mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in

  2. Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization

    Science.gov (United States)

    Sidabras, Jason W.; Strangeway, Robert A.; Mett, Richard R.; Anderson, James R.; Mainali, Laxman; Hyde, James S.

    2016-03-01

    Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-optic techniques by minimal coupling to higher-order modes. Only the TE10 mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in

  3. Generation of ultra broadband supercontinuum in dispersion managed silicon nanophotonic waveguides

    CERN Document Server

    Ciret, Charles

    2016-01-01

    Dispersion managed (DM) silicon nanophotonic waveguides are investigated for the generation of optimal ultra broadband supercontinuum (SC). DM waveguides are made of a longitudinally dependent group velocity dispersion resulting from the variation of the waveguide width with the propagation distance. For the generation of optimal SC, a genetic algorithm has been used to find the best dispersion map. This allows for the generation of a highly coherent supercontinuum spanning from 1100~nm to 2950~nm at -40~dB level for 2\\,$\\mu$m, 200 fs and 6.4 pJ input pulse. The comparison with optimal fixed width and tapered waveguides shows that the SC is 300\\,nm broader in the DM waveguide, while the high coherence is ensured by the varying dispersion.

  4. High-performance THz metamaterial absorber

    CERN Document Server

    Zhu, Jianfei; Sun, Wujiong; Ding, Fei; He, Qiong; Zhou, Lei; Ma, Yungui

    2014-01-01

    We demonstrated an ultra-broadband, polarization-insensitive and wide-angle metamaterial absorber for terahertz (THz) frequencies using arrays of truncated pyramid unit structure made of metal-dielectric multilayer composite. In our design each sub-layer behaving as an effective waveguide is gradually modified in their lateral width to realize a wideband response by effectively stitching together the resonance bands of different waveguide modes. Experimentally, our five layer sample with a total thickness 21um is capable of producing a large absorptivity above 80% from 0.7 to 2.3 THz up to the maximum measurement angle 40{\\deg}. The full absorption width at half maximum (FWHM) of our device is around 127%, greater than those previously reported for THz frequencies. Our absorber design has high practical feasibility and can be easily integrated with the semiconductor technology to make high efficient THz-oriented devices.

  5. A Stable 0.2-THz Coaxial-Waveguide Gyrotron Traveling-Wave-Tube Amplifier with Distributed Losses

    Science.gov (United States)

    Hung, C. L.; Yeh, Y. S.; Chang, T. H.; Fang, R. S.

    2016-08-01

    For high-power operation, a THz gyrotron traveling-wave-tube (gyro-TWT) amplifier must operate in a high-order waveguide mode to enlarge the transverse dimension of an interaction waveguide. However, a gyro-TWT amplifier operating in a high-order waveguide mode is susceptible to spurious oscillations. To improve the device stability, in this study, we investigate the possibility of using a coaxial waveguide with distributed losses as the interaction structure. For the same required attenuation, all threatening oscillating modes can be suppressed using different combinations of losses of inner and outer cylinders. This provides flexibility in designing distributed losses when considering the ohmic loading of the interaction structure. We predict that the 0.2-THz gyro-TWT can stably produce a peak power of 14 kW with an efficiency of 23 %, a 3-dB bandwidth of 3.5 GHz, and a saturated gain of 50 dB for a 20-kV 3-A electron beam with a 5 % velocity spread and 1.0 velocity ratio.

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

    OpenAIRE

    B.T.P.Madhav; HABIBULLA KHAN; SARAT K. KOTAMRAJU

    2016-01-01

    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

  7. Novel crystalline-waveguide broadband light sources for interferometry

    OpenAIRE

    Pollnau, Markus

    2003-01-01

    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 longitudinal resolution of such instruments is inversely proportional to the optical bandwidth of the light source. Broadband luminescence from transition-metal-ion doped materials can significantly improve t...

  8. Generation of broadband and multiple-peak THz radiation in aperiodically poled lithium niobate

    Institute of Scientific and Technical Information of China (English)

    Fucheng Chen; Xianfeng Chen; Yuping Chen; Yuxing Xia

    2005-01-01

    @@ We theoretically analyze the generation of broadened and multi-peak terahertz (THz) radiation in aperiodically poled lithium niobate (APPLN), whose sequence of opposite domains is optimized by simulated annealing (SA) algorithm. The full-width at half maximum (FWHM) of the broadened THz radiation in our simulation is 0.26 THz. Both of the central wavelength and FWHM can be easily tuned by choosing proper objective functions. THz radiation with wider and flatter FWHM can be achieved by increasing the length of the lithium niobate crystal. The two-peak THz generation is also provided as an example of multi-peak with the central wavelengths at 1.68 and 1.80 THz, respectively.

  9. Broadband, stable and highly coherent supercontinuum generation at telecommunication wavelengths in an hydrogenated amorphous silicon waveguide

    CERN Document Server

    Leo, F; Kuyken, B; Roelkens, G; Gorza, S -P

    2014-01-01

    Hydrogenated amorphous silicon (a:Si-H) has recently been recognized as a highly nonlinear CMOS compatible photonic platform. We experimentally demonstrate the generation of a supercontinuum (SC) spanning over 500 nm in a-Si:H photonic wire waveguide at telecommunication wavelengths using femtosecond input pulse with energy lower than 5 pJ. Numerical modeling of pulse propagation in the waveguide, based on the experimentally characterized dispersion profile, shows that the supercontinuum is the result of soliton fission and dispersive wave generation. It is demonstrated that the SC is highly coherent and that the waveguides do not suffer from material degradation under femtosecond pulse illumination. Finally, a direct comparison of SC generation in c-Si and a-Si:H waveguides confirms the higher performances of a-Si:H over c-Si for broadband low power SC generation at telecommunication wavelengths.

  10. Dispersion engineering silicon nitride waveguides for broadband nonlinear frequency conversion

    NARCIS (Netherlands)

    Epping, J.P.

    2015-01-01

    In this thesis, we investigated nonlinear frequency conversion of optical wavelengths using integrated silicon nitride (Si3N4) waveguides. Two nonlinear conversion schemes were considered: seeded four-wave mixing and supercontinuum generation. The first—seeded four-wave mixing—is investigated by a n

  11. 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...

  12. Ti:sapphire rib waveguides as single-transverse-mode broadband fluorescence sources for optical coherence tomography applications

    NARCIS (Netherlands)

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

    2003-01-01

    Ar+-beam-milled rib waveguides in pulsed-laser-deposited Ti:sapphire layers show broadband single transverse mode fluorescence emission at output powers up to 300 μW and propagation losses comparable to those in unstructured planar waveguide counterparts.

  13. Broadband quasi-phase-matched second-harmonic generation in MgO: LiNbO3 waveguide

    Institute of Scientific and Technical Information of China (English)

    LIU Gui-hua; GUO Hai-run; FU Xing-hu; ZENG Xiang-long

    2011-01-01

    The quasi-phase-matched (QPM) condition of broadband second harmonic generation (SHG) in Ti-diffused MgO:LiNbOwaveguide is theoretically simulated. The results show that the center wavelength of broadband SHG dependent on the waveguide width is around 1550 nm and the bandwidth is 50 nm.

  14. Robust transmission stabilization and dynamic switching in broadband hybrid waveguide systems with nonlinear gain and loss

    Science.gov (United States)

    Nguyen, Quan M.; Peleg, Avner; Tran, Thinh P.

    2015-01-01

    We develop a method for transmission stabilization and robust dynamic switching for colliding optical soliton sequences in broadband waveguide systems with nonlinear gain and loss. The method is based on employing hybrid waveguides, consisting of spans with linear gain and cubic loss, and spans with linear loss, cubic gain, and quintic loss. We show that the amplitude dynamics is described by a hybrid Lotka-Volterra (LV) model, and use the model to determine the physical parameter values required for enhanced transmission stabilization and switching. Numerical simulations with coupled nonlinear Schrödinger equations confirm the predictions of the LV model, and show complete suppression of radiative instability and pulse distortion. This enables stable transmission over distances larger by an order of magnitude compared with uniform waveguides with linear gain and cubic loss. Moreover, multiple on-off and off-on dynamic switching events are demonstrated over a wide range of soliton amplitudes, showing the superiority of hybrid waveguides compared with static switching in uniform waveguides.

  15. 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.

  16. Broadband near total light absorption in non-PT-symmetric waveguide-cavity systems.

    Science.gov (United States)

    Huang, Yin; Min, Changjun; Veronis, Georgios

    2016-09-19

    We introduce broadband waveguide absorbers with near unity absorption. More specifically, we propose a compact non-parity-time-symmetric perfect absorber unit cell, consisting of two metal-dielectric-metal (MDM) stub resonators with unbalanced gain and loss side-coupled to a MDM waveguide, based on unidirectional reflectionlessness at exceptional points. With proper design, light can transport through the perfect absorber unit cell with reflection close to zero in a broad wavelength range. By cascading multiple unit cell structures, the overall absorption spectra are essentially the superposition of the absorption spectra of the individual perfect absorber unit cells, and absorption of ~ 100% is supported in a wide range of frequencies. PMID:27661956

  17. Ultra-compact broadband nanowire-to-slot waveguide mode converter based on SOI

    Science.gov (United States)

    Qi, Ying; An, Junming; Wang, Yue; Zhang, Xiaoguang

    2014-11-01

    A novel ultra-compact high-efficiency broadband mode converter between silicon (Si) nanowire and silicon slot waveguide based on Silicon-on-Insulator (SOI) is proposed in this paper. By introducing a gradual-width structure between Si nanowire and slot waveguide, the favorable transition between nanowire mode (Gaussian-like mode) and slot mode (non-Gaussian-like mode) can be obtained and then the coupling efficiency is improved. The structure is simulated and optimized by using the three-dimension Finite-Difference Time-Domain Method (3D-FDTD). The coupling efficiency of over 90% within bandwidth of over 600nm can be achieved by only 200nm-length converter which is the smallest size to our knowledge. This presented mode converter can meet the demand of ultra-compact, wavelength-insensitive of monolithic integration.

  18. 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.

  19. Hybrid Plasmonic Waveguide Fed Broadband Nano-antenna for Nanophotonic Applications

    CERN Document Server

    Saad-Bin-Alam, Md; Rahman, Atiqur; Chowdhury, Arshad M

    2014-01-01

    In this paper, we propose a novel hybrid plasmonic waveguide fed broadband optical patch nano-antenna for nanophotonic applications. Through full wave electromagnetic simulation, we demonstrated our proposed antenna to radiate and receive signal at all optical communication windows (e.g. $\\lambda$ = 850nm, 1310nm & 1550nm) with around 86% bandwidth within the operational domain. Moreover numerical results demonstrate that the proposed nano-antenna has directional radiation pattern with satisfactory gain over all three communication bands. Additionally, we evaluated the antenna performances with two different array arrangements (e.g. one dimensional and square array). The proposed broadband antenna can be used for prominent nanophotonic applications such as optical wireless communication in inter and intra-chip devices, optical sensing and optical energy harvesting etc.

  20. Ultra-broadband terahertz metamaterial absorber

    Science.gov (United States)

    Zhu, Jianfei; Ma, Zhaofeng; Sun, Wujiong; Ding, Fei; He, Qiong; Zhou, Lei; Ma, Yungui

    2014-07-01

    We demonstrated an ultra-broadband, polarization-insensitive, and wide-angle metamaterial absorber for terahertz (THz) frequencies using arrays of truncated pyramid unit structure made of metal-dielectric multilayer composite. In our design, each sub-layer behaving as an effective waveguide is gradually modified in their lateral width to realize a wideband response by effectively stitching together the resonance bands of different waveguide modes. Experimentally, our five layer sample with a total thickness 21 μm is capable of producing a large absorptivity above 80% from 0.7 to 2.3 THz up to the maximum measurement angle 40°. The full absorption width at half maximum of our device is around 127%, greater than those previously reported for THz frequencies. Our absorber design has high practical feasibility and can be easily integrated with the semiconductor technology to make high efficient THz-oriented devices.

  1. On-chip visible-to-infrared supercontinuum generation with more than 495 THz spectral bandwidth

    NARCIS (Netherlands)

    Epping, J.P.; Hellwig, T.; Hoekman, M.; Mateman, R.; Leinse, A.; Heideman, R.G.; Rees, van A.; Slot, van der P.J.M.; Lee, C.J.; Fallnich, C.; Boller, K-J.

    2015-01-01

    We report ultra-broadband supercontinuum generation in high-confinement Si3N4 integrated optical waveguides. The spectrum extends through the visible (from 470 nm) to the infrared spectral range (2130 nm) comprising a spectral bandwidth wider than 495 THz, which is the widest supercontinuum spectrum

  2. Broad-band coupling of THz radiation to an YBa2Cu3O7-δ hot-electron bolometer mixer

    International Nuclear Information System (INIS)

    We report on broad-band coupling of THz radiation to an YBa2Cu3O7-δ superconducting hot-electron bolometer. The bolometer - a micro-bridge of an YBa2Cu3O7-δ film with a PrBa2Cu3O7-δ protection layer - was built in a hybrid quasioptical antenna system consisting of a planar self-complementary spiral antenna on a dielectric substrate and an extended hyperhemispherical lens. The planar antenna was integrated into a coplanar transmission line for broad-band intermediate-frequency matching. Measurements performed in the direct detection regime between 2.5 THz and 4.2 THz delivered a system coupling efficiency for the radiation in the fundamental Gaussian mode of about 0.1 and a beam width of the radiation pattern of less than one degree. The pattern was consistent with the far-field radiation pattern that we calculated with a ray-tracing technique. At an intermediate frequency of 1.5 GHz we measured an output noise temperature of approx. 160 K for the bolometer driven in the resistive state by both dc and THz current and estimated, for the heterodyne regime, a system noise temperature of approx. 3x105 K. We studied the effect of a protection layer on the rate of phonon escape from the micro-bridge and, thus, on the output frequency bandwidth of the device. We discuss possibilities of a significant improvement of the device performance. (author)

  3. 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.

  4. Design of broadband power splitters using two-mode interference in slot waveguides

    Science.gov (United States)

    Chen, Bing; Liu, Chunliang; Si, Jinhai

    2015-11-01

    Two-mode interference effects in slot waveguides have been predicted and investigated through plane wave expansion and finite-difference time-domain methods. A broadband 1×2 power splitter (PS) based on this effect is presented, and its transmission characteristics are investigated by using finite-difference time-domain method. Calculated results indicate that, for the 1×2 PS whose interaction length is as short as 0.509 μm, the high transmission (≥95%) is observed within a wavelength range of 1.389-1.747 μm, corresponding to a relative bandwidth of 22.87%. Combining three 1×2 PS, we construct a 1×4 PS with excellent transmission characteristics. Those simple PS are expected to be applied to highly dense photonic integrated circuits.

  5. 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...

  6. Dielectric response of pure and doped-GaSe crystals studied by an indigenously developed broadband THz-TDS system

    Science.gov (United States)

    Das, Amit C.; Bhattacharya, S.; Mandal, K. C.; Mondal, S.; Jewariya, M.; Ozaki, T.; Bhaktha, S. N. B.; Datta, P. K.

    2016-04-01

    Publisher's Note: This paper, originally published on 12 July 2016, was replaced with a corrected/revised version on 26 July 2016. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. We have developed a terahertz time domain spectroscopy system (THz TDS). For THz generation, optical rectification process and for detection, electro-optic sampling processes are used. Identical cut ZnTe crystals are used for both generation and detection of THz radiation.This spectroscopy system can be used for the noninvasive and contactless electrical and optical characterizations of various samples. In this work spectroscopic measurements of pure, Chromium and Indium doped GaSe crystals within 0.4 THz to 3 THz range are taken by the developed set-up to study the dielectric response of the samples.

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

    Science.gov (United States)

    Chang, Ken-Wei; Huang, Chia-Chien

    2016-01-01

    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. PMID:26786972

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

    Science.gov (United States)

    Chang, Ken-Wei; Huang, Chia-Chien

    2016-01-01

    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.

  9. 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...

  10. Efficient coupling of propagating broadband terahertz radial beams to metal wires.

    Science.gov (United States)

    Zheng, Zhu; Kanda, Natsuki; Konishi, Kuniaki; Kuwata-Gonokami, Makoto

    2013-05-01

    Bare metal wires have recently been demonstrated as waveguides for transporting terahertz (THz) radiation, where the guiding mode is radially polarized surface Sommerfeld waves. In this study, we demonstrate high-efficiency coupling of a broadband radially polarized THz pulsed beam, which is generated with a polarization-controlled beam by a segmented half-wave-plate mode converter, to bare copper wires. A total coupling efficiency up to 16.8% is observed, and at 0.3 THz, the maximum coupling efficiency is 66.3%. The results of mode-overlap calculation and numerical simulation support the experimental data well. PMID:23669920

  11. Optimal design and performance verification of a broadband waveguide filter using ANN-GA algorithm

    Directory of Open Access Journals (Sweden)

    Manidipa Nath

    2013-09-01

    Full Text Available In this work design and optimization of EBGstructure having multiple dielectric posts uniformly placed insidea rectangular waveguide is done to extract filter responses.Frequency response of BPF configuration using trained ANNmodel of multipost rectangular waveguide are studied andoptimized using GA. The geometrical and positional dimensionof post parameters are varied in accordance to the requirementof reflectance and transmittance of the filter.

  12. Optimal design and performance verification of a broadband waveguide filter using ANN-GA algorithm

    OpenAIRE

    Manidipa Nath; Sudhabindu Ray; Bhaskar Gupta

    2013-01-01

    In this work design and optimization of EBGstructure having multiple dielectric posts uniformly placed insidea rectangular waveguide is done to extract filter responses.Frequency response of BPF configuration using trained ANNmodel of multipost rectangular waveguide are studied andoptimized using GA. The geometrical and positional dimensionof post parameters are varied in accordance to the requirementof reflectance and transmittance of the filter.

  13. Broadband terahertz fiber directional coupler

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Jepsen, Peter Uhd;

    2010-01-01

    We present the design of a short broadband fiber directional coupler for terahertz (THz) radiation and demonstrate a 3 dB coupler with a bandwidth of 0:6 THz centered at 1:4 THz. The broadband coupling is achieved by mechanically downdoping the cores of a dual-core photonic crystal fiber...

  14. Broadband frequency conversion via adiabatically tapered $\\chi^{(2)}$ waveguide in photonic integrated circuits

    CERN Document Server

    Xiong, Xiao; Guo, Xiang; Tang, Hong X; Ren, Xi-Feng; Guo, Guang-Can

    2016-01-01

    We propose to use the integrated aluminum nitride waveguide with engineered width variation to achieve optical frequency conversion based on $\\chi^{(2)}$ nonlinear effect on a photonic chip. We show that in an adiabatically tapered waveguide, the frequency conversion has a much broader bandwidth and the efficiency within the bandwidth is almost constant, which is favorable for short pulses. We demonstrate both analytically and numerically an "area law" for the frequency conversion, i.e. the product of bandwidth and efficiency is conserved as long as peak conversion efficiency does not saturate. The adiabatic structure shows higher saturation thresholds in pump power or interaction length, outperforming the conventional uniform waveguide design. With our approach, high-efficiency and wavefront-keeping conversion for short pulses is possible on a photonic chip, which will surely find applications for scalable on-chip information processing.

  15. Compact and broadband waveguide taper based on partial bandgap photonic crystals

    Institute of Scientific and Technical Information of China (English)

    Jin Hou; Dingshan Gao; Huaming Wu; Zhiping Zhou

    2009-01-01

    Partial bandgap characteristics of parallelogram lattice photonic crystals are proposed to suppress the radiation modes in a compact dielectric waveguide taper so as to obtain high transmittance in a large wavelength range. Band structure of the photonic crystals shows that there exists a partial bandgap. The photonic crystals with partial bandgap are then used as the cladding of a waveguide taper to reduce the radiation loss efficiently. In comparison with the conventional dielectric taper and the complete bandgap photonic crystal taper, the partial bandgap photonic crystal taper has a high transmittance of above 85% with a wide band of 170 nm.

  16. Ultra-compact, broadband tunable optical bandstop filters based on a multimode one-dimensional photonic crystal waveguide.

    Science.gov (United States)

    Huang, Qingzhong; Jie, Kun; Liu, Qiang; Huang, Ying; Wang, Yi; Xia, Jinsong

    2016-09-01

    In this paper, ultra-compact, broadband tunable optical bandstop filters (OBSFs) based on a multimode one-dimensional photonic crystal waveguide (PhCW) are proposed and systematically investigated. For the wavelengths in the mini-stopband, the input mode is coupled to a contra-propagating higher order mode by the PhCW and then radiates in a taper, resulting in a stopband at the output with low backreflection at the input. Three-dimensional finite-difference time-domain method is employed to study the OBSFs. The influence of main structural parameters is analyzed, and the design is optimized to reduce the back-reflection and band sidelobes. Using localized heating, we can shift the stopband and tune the bandwidth continuously by cascading the proposed structures. Due to the strong grating strength, our device provides a more compact footprint (40 μm × 1 μm) and much broader stopband (bandwidth of up to 84 nm), compared to the counterparts based on microrings, long-period waveguide gratings, and multimode two-dimensional PhCWs. PMID:27607658

  17. Design and fabrication of pill-box window for 0.14 THz folded waveguide traveling wave tubes%0.14 THz折叠波导行波管盒型窗设计与制作

    Institute of Scientific and Technical Information of China (English)

    王亚军; 陈樟; 刘俊

    2013-01-01

    This paper mainly discusses the pill-box window with sapphire piece for 0.14 THz folded waveguide traveling wave tubes. The dimension of the window is computed and optimized by HFSS. The VSWR is below 1.2 when the main structure parameters range at ±0.01 mm. Cold-test result shows the attenuation of the window test structure is about 0.7 dB during 0.135 THz-0.145 THz,which meets the practical requirements in 0.14 THz folded waveguide traveling wave tubes.%  研究用于0.14 THz 折叠波导行波管的盒形窗结构,采用三维模拟软件 HFSS 进行计算与优化,设计出基于蓝宝石窗片的盒型窗结构。分析了结构参数对盒形窗电压驻波比的影响,主要结构参数在±0.01 mm范围变化时,盒形窗电压驻波比仍然低于1.2,保证零件加工的可行性。装配完成盒形窗测试结构,冷测结果显示,在0.135 THz~0.145 THz范围内衰减系数为0.7 dB左右,满足整管要求。

  18. A Compact and Broadband Differential Microstrip Line to Rectangular Waveguide Transition Using Dipole Antenna

    Science.gov (United States)

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

    2016-06-01

    In this paper, a compact full Ka-band differential microstrip line (DML) to rectangular waveguide transition is proposed. The dipole antenna with semi-elliptic arms is introduced to transform the differential mode of DML to the TE10 mode of the rectangular waveguide directly. The two arms of the dipole antenna are connected together by a shorting strip to reduce the size of the dipole. Compared with the DML-to-waveguide transition using the fin-line topology, the size of the proposed transition has been reduced by 86 %. To verify this transition, a back-to-back structure is fabricated and tested. It provides a return loss of better than 15.2 dB and an insertion loss of 0.73 to 1.07 dB within a wide frequency range from 26.5 to 40 GHz. The measurement results show good agreement with the simulation results. Furthermore, a tolerance analysis is also performed via the simulation to prove that this transition is robust in the fabrication and mechanical assembly.

  19. Femtosecond writing of near-surface waveguides in lithium niobate for low-loss electro-optical modulators of broadband emission

    Science.gov (United States)

    Bukharin, Mikhail A.; Skryabin, Nikolay N.; Khudyakov, Dmitriy V.; Vartapetov, Sergey K.

    2016-05-01

    In the investigation we demonstrated technique of direct femtosecond laser writing of tracks with induced refractive index at record low depth under surface of lithium niobate (3-15 μm). It was shown that with the help of proposed technique one can be written claddings of near surface optical waveguides that plays a key role in fabrication of fast electro-optical modulators with low operating voltage. Fundamental problem resolved in the investigation consists in suppression of negative factors impeding femtosecond inscription of waveguides at low depths. To prevent optical breakdown of crystal surface we used high numerical aperture objectives for focusing of light. It was shown, that advanced heat accumulation regime of femtosecond inscription is inapplicable for writing of near-surface waveguides, and near the surface waveguides should be written in non-thermal regime in contrast to widespread femtosecond writing at depths of tens micrometers. Inscribed waveguides were examined for optical losses and polarization properties. It was experimentally shown, that femtosecond written near surface waveguides have such advantages over widely used proton exchanged and Ti-diffusion waveguides as lower optical losses (down to 0.3 dB/cm) and maintaining of all polarization states of propagation light, which is crucial for development of electro-optical modulators for broadband and ultrashort laser emission. Novelty of the results consists in technique of femtosecond inscription of waveguides at record low depths under the surface of crystals. As compared to previous investigations in the field (structures at depths near 50 um with buried electrodes), the obtained waveguides could be used with simple closely adjacent on-surface electrodes.

  20. 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.

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

    Science.gov (United States)

    Yang, Xin Mi; Wen, Juan; Liu, Chang Rong; Liu, Xue Guan; Cui, Tie Jun

    2015-12-01

    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.

  2. 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.

  3. Tunable Multilayer Graphene Metamaterials for Terahertz/Infrared Waveguide Modulators

    DEFF Research Database (Denmark)

    Khromova, Irina; Andryieuski, Andrei; Lavrinenko, Andrei

    Active development of terahertz (THz)/ infrared (IR) science and technology has created a growing demand for new electronic and quasi-optical devices. In particular, the promising opportunities for broadband high-speed terahertz communication require new techniques for real-time manipulation......-space propagation configurations. However, high-speed THz/IR communication channels will unlikely be based on such architectures - atmospheric absorption peaks and small wavelengths (from submillimeter to tens of micrometers) imply strong free-space attenuation. It is therefore preferential to apply waveguide...... and very high modulation depth: > 38 dB with only 70 meV graphene electrochemical potential change. The second one is a modulator with extreme sensitivity towards graphene Fermi energy. The third one is a tunable waveguide-based passband filter. The narrow-band cut-off conditions around the ON-state allow...

  4. Broadband terahertz spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Wenhui Fan

    2011-01-01

    1.Introduction Spanning the frequency range between the infrared (IR) radiation and microwaves,terahertz (THz) waves are,also known as T-rays,T-lux,or simply called THz,assigned to cover the electromagnetic spectrum typically from 100 GHz (1011 Hz) to 10 THz (1013 Hz),namely,from 3 mm to 30 μm in wavelength,although slightly different definitions have been quoted by different authors.For a very long time,THz region is an almost unexplored field due to its rather unique location in the electromagnetic spectrum.Well-known techniques in optical or microwave region can not be directly employed in the THz range because optical wavelengths are too short and microwave wavelengths are too long compared to THz wavelengths.%An overview of the major techniques to generate and detect THz radiation so far, especially the major approaches to generate and detect coherent ultra-short THz pulses using ultra-short pulsed laser, has been presented. And also, this paper, in particularly, focuses on broadband THz spectroscopy and addresses on a number of issues relevant to generation and detection of broadband pulsed THz radiation as well as broadband time-domain THz spectroscopy (THz-TDS) with the help of ultra-short pulsed laser. The time-domain waveforms of coherent ultra-short THz pulses from photoconductive antenna excited by femtosecond laser with different pulse durations and their corresponding Fourier-transformed spectra have been obtained via the numerical simulation of ultrafast dynamics between femtosecond laser pulse and photoconductive material. The origins of fringes modulated on the top of broadband amplitude spectrum, which is measured by electric-optic detector based on thin nonlinear crystal and extracted by fast Fourier transformation, have been analyzed and the major solutions to get rid of these fringes are discussed.

  5. Variable height slot-outcoupling for the compact UH THz-FEL

    International Nuclear Information System (INIS)

    The quest for tunable, compact coherent radiation sources in the THz region of the electro-magnetic spectrum is growing and stimulating further developments and research activities in this area. The THz-FEL Group of the University of Hawaii (UH) pursues the concept of minimizing size and cost of a recirculating-beam electrostatic accelerator THz-FEL. The system employs a low voltage (1.7 MeV) pelletron accelerator in conjunction with a short period (λu=8 mm) hybrid undulator and miniature beam line components. The continuous tunability offered by the system over a spectral range between 230 and 640 μm necessitates a broad-band outcoupling mechanism. Holes on the axis in resonator mirrors have been previously employed in long wavelength FELs as a means to couple out optical radiation from the cavity. The UH THz-FEL adopted a parallel plate waveguide resonator design introducing a height adjustable slot-aperture on one of the cylindrical metal mirrors. Based on the mode-matching method employed in treating waveguide discontinuities, we examine the characteristics of the chosen outcoupling mechanism and its influence on the intracavity optical fields

  6. THz based phase space manipulation in a zero-slippage IFEL

    CERN Document Server

    Curry, E; Musumeci, P; Gover, A

    2016-01-01

    We describe an IFEL interaction driven by a guided broadband THz source to compress a relativistic electron bunch and synchronize it with an external laser pulse. A high field near single-cycle THz pulse, generated via optical rectification from the external laser source, is group velocity-matched to the electron bunch inside a waveguide, allowing for a sustained interaction in a magnetic undulator. We present measurements of the THz waveform before and after a curved parallel plate waveguide with varying aperture size and estimate the reduced group velocity. For a proof-of-concept experiment at the UCLA PEGASUS laboratory, a 6 MeV, 100 fs electron bunch with an initial 0.03 % energy spread can be readily produced. Given these parameters and a projected THz peak field of 10 MV/m, our simulation model predicts a phase space rotation of the bunch distribution that compresses the electron bunch by nearly an order of magnitude and reduces any initial timing jitter within the phase acceptance window. We also discu...

  7. 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.

  8. Spectral phase transfer from near IR to deep UV by broadband phase-matched four-wave mixing in an argon-filled hollow core waveguide

    Science.gov (United States)

    Siqueira, J. P.; Mendonça, C. R.; Zilio, S. C.; Misoguti, L.

    2016-10-01

    We report on the implementation of a spectral phase transfer scheme from near IR to deep UV, in which the frequency conversion step is based on the broadband phase-matched four-wave mixing in a gas-filled hollow core waveguide. Micro joule level femtosecond pulses at 260 nm were generated by nonlinear mixing of a Ti:sapphire laser and its second-harmonic. The transfer of a π-step phase in a controllable manner was proposed and confirmed by a modulation observed in the generated deep UV femtosecond pulse spectrum due to an interference process. Numerical simulations confirmed our results.

  9. A New Type of Terahertz Waveguides

    Institute of Scientific and Technical Information of China (English)

    LOU Shu-Qin; GUO Tie-Ying; FANG Hong; LI Hong-Lei; JIAN Shui-Sheng

    2006-01-01

    A new type of THz waveguides, which employs a solid polyethylene rod as the core and polyethylene tubes in a periodic array of square lattice as the cladding, is proposed. Optical properties of this new THz waveguide, especially in dispersion, confinement loss and single mode property, are investigated in detail with the plane wave expansion method and the beam propagation method. Numerical results demonstrate that the new THz waveguide can reach not only low dispersion but also low confinement loss at single mode propagation. Therefore, the square lattice structure is a better candidate as THz waveguides than the triangular ones.

  10. 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, M.; 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

  11. Design and Analysis of Broad-Band Fixed-Tuned Submillimeter-Waveguide Multipliers using MMIC Style Circuit Topology

    Science.gov (United States)

    Bruston, J.; Kim, M.; Martin, S. C.; Mehdi, I.; Smith, R. P.; Siegel, P. H.

    1996-01-01

    The design and analysis of varactor diode doubler, quadrupler and cascaded doubler circuits for 320 and 640 GHz have been completed. A new approach has been employed to produce a tunerless waveguide mount with a very flexible, frequency scaleable, MMIC style multiplier circuit. The concept, design, predicted performance and measurements on some of the constituent mount elements are presented.

  12. 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, M.; 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 sh

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

    Science.gov (United States)

    Rahmani, Z.; Heidari-Semiromi, E.; Safari, S.

    2016-06-01

    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.

  14. Optimizing Broadband Terahertz Modulation with Hybrid Graphene/Metasurface Structures

    OpenAIRE

    Shi, S. -F.; Zeng, B.; Han, H. -L.; Hong, X; Tsai, H. -Z.; Jung, H. S.; Zettl, A.; Crommie, M. F.; Wang, F.

    2014-01-01

    We demonstrate efficient terahertz (THz) modulation by coupling graphene strongly with a broadband THz metasurface device. This THz metasurface, made of periodic gold slit arrays, shows near unity broadband transmission, which arises from coherent radiation of the enhanced local-field in the slits. Utilizing graphene as an active load with tunable conductivity, we can significantly modify the local-field enhancement and strongly modulate the THz wave transmission. This hybrid device also prov...

  15. A novel broadband terahertz filter for photonic crystal

    Science.gov (United States)

    Luo, Yuan; Li, Yanyan; Hu, Zhangfang; Liu, Jinlan

    2016-09-01

    The influence of the change of the radius of point defect cylinders, scattering dielectric cylinders, dielectric cylinders on both sides of line waveguide on S parameter is studied. According to the resonant coupling principle between micro-cavity and waveguide, a novel broadband terahertz filter is designed. The novel filter is formed by introducing scattering dielectric cylinders into the resonant microcavity, and the point defect cylinders are composed of HgTe material and adjusting the radius of dielectric cylinders on both sides of line waveguide. Results show that the 3 dB bandwidth reaches 74.2 GHz, the return loss is less than -12.02 dB, the maximum insertion loss in-band reaches 0.35 dB and its drop efficiency is up to 96.79%. The novel terahertz filter has flat passband, sharp rejections at out-bands and its central frequency is 0.338THz. The good performances show that it can meet the requirements of high speed and broadband in terahertz atmosphere communication I window.

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

    Science.gov (United States)

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

    2015-12-01

    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.

  17. 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)

    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)

  18. Low-loss and bendable THz fiber with tailored dispersion

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Adam, Aurèle J. L.;

    2009-01-01

    A polymer THz fiber made of Topas and having a Photonic Crystal Fiber structure is demonstrated. It has low broadband loss and the dispersion of the fiber can be tailored by adjusting the structural parameters.......A polymer THz fiber made of Topas and having a Photonic Crystal Fiber structure is demonstrated. It has low broadband loss and the dispersion of the fiber can be tailored by adjusting the structural parameters....

  19. Theoretical study of ultra-wideband slow light in dual-stub-coupled plasmonic waveguide

    Science.gov (United States)

    Li, Chunlei; Su, Runzhou; Wang, Yuxiao; Zhang, Xueru

    2016-10-01

    We propose and demonstrate a metal-insulator-metal (MIM) waveguide side coupled double stubs to realize broadband slow surface plasmon polaritons (SPPs) around the telecom frequency 193.5 THz. When the depth of single stub is approximately equal to integral multiple of half plasmon wavelength, owing to the constructive interferences between the electromagnetic wave propagating through the MIM waveguide and that reflected from the stubs, wideband slow light effect appears. The improved transmission line theory calculation indicates that the group velocity of SPPs in the plasmonic waveguide system for stub depth 1111 nm is 0.1c (c is light speed in vacuum.) over a broad bandwidth of 69 THz. Exploiting the finite-difference time-domain (FDTD) numerical simulation, the group velocity of pulse for width 20 fs (Full width at half high) is calculated. The result agrees well with that predicted by the transmission line theory. This plasmonic waveguide for slow light effect has important potential application in optical delay lines.

  20. Optimizing broadband terahertz modulation with hybrid graphene/metasurface structures.

    Science.gov (United States)

    Shi, S-F; Zeng, B; Han, H-L; Hong, X; Tsai, H-Z; Jung, H S; Zettl, A; Crommie, M F; Wang, F

    2015-01-14

    We demonstrate efficient terahertz (THz) modulation by coupling graphene strongly with a broadband THz metasurface device. This THz metasurface, made of periodic gold slit arrays, shows near unity broadband transmission, which arises from coherent radiation of the enhanced local-field in the slits. Utilizing graphene as an active load with tunable conductivity, we can significantly modify the local-field enhancement and strongly modulate the THz wave transmission. This hybrid device also provides a new platform for future nonlinear THz spectroscopy study of graphene. PMID:25483819

  1. Time-resolved terahertz spectroscopy in a parallel-plate waveguide

    DEFF Research Database (Denmark)

    Cooke, David; Jepsen, Peter Uhd

    2009-01-01

    a parallel plate waveguide, termed time-resolved THz waveguide spectroscopy. The interaction of the THz radiation with the sample is then enhanced by travelling along the material over lengths of cm's instead of through it where the length can be nm's. We highlight the performance of this technique...... by examining photocarriers induced in Si and show a spin-off technique where we can use the photocarriers to control the propagation of the THz pulse within the waveguide....

  2. Polymer fiber waveguides for terahertz radiation

    DEFF Research Database (Denmark)

    Nielsen, Kristian

    Terahertz radiation offers many exciting applications noticeably in spectroscopy and it is showing promising results in imaging, mainly for security applications. In this project the study of using structured polymer fibers for THz waveguiding is presented. The inspiration for the THz fiber...

  3. Short pulse generation and mode control of broadband terahertz quantum cascade lasers

    CERN Document Server

    Bachmann, Dominic; Süess, Martin J; Beck, Mattias; Unterrainer, Karl; Darmo, Juraj; Faist, Jérôme; Scalari, Giacomo

    2016-01-01

    We report on a waveguide engineering technique that enables the generation of a bandwidth up to 1 THz and record ultra-short pulse length of 2.5 ps in injection seeded terahertz quantum cascade lasers. The reported technique is able to control and fully suppress higher order lateral modes in broadband terahertz quantum cascade lasers by introducing side-absorbers to metal-metal waveguides. The side-absorbers consist of a top metalization set-back with respect to the laser ridge and an additional lossy metal layer. In continuous wave operation the side-absorbers lead to octave spanning laser emission, ranging from 1.63 to 3.37 THz, exhibiting a 725 GHz wide at top within a 10 dB intensity range as well as frequency comb operation with a bandwidth of 442 GHz. Numerical and experimental studies have been performed to optimize the impact of the side-absorbers on the emission properties and to determine the required increase of waveguide losses. Furthermore, these studies have led to a better understanding of the ...

  4. Efficient and broadband polarization conversion with the coupled metasurfaces.

    Science.gov (United States)

    Huang, Cheng-ping

    2015-12-14

    Coupled metasurfaces may refer to a composite plasmonic structure, which consists of multilayered but usually different metasurfaces. A pair of orthogonal plasmonic polarizers, which represents one of such systems, can induce a transmission of light and 90-degree polarization rotation. We explored the effect systematically and found that such effect may be highly efficient and broadband in the near-infrared region. By combining the low-loss metal (silver), the longer operating wavelength, and a work style using propagating waveguide mode, conversion efficiency more than 80% has been suggested near the telecom wavelength. We also suggested that, by overlapping the internal surface-plasmon (2, 0) and (1, 1) modes, an efficient and wideband polarization rotation can be realized. The maximal efficiency is 83% around the wavelength 1340 nm, and the working bandwidth reaches 300 nm. Similar effect has also been revealed in the THz band. The results are useful for constructing compact and high-performance polarization rotators. PMID:26698992

  5. Broadband Polarizers Based on Graphene Metasurfaces

    CERN Document Server

    Guo, Tianjing

    2016-01-01

    We present terahertz (THz) metasurfaces based on aligned rectangular graphene patches placed on top of a dielectric layer to convert the transmitted linearly polarized waves to circular or elliptical polarized radiation. Our results lead to the design of an ultrathin broadband THz quarter-wave plate. In addition, ultrathin metasurfaces based on arrays of L-shaped graphene periodic patches are demonstrated to achieve broadband cross-polarization transformation in reflection and transmission. The proposed metasurface designs have tunable responses and are envisioned to become the building blocks of several integrated THz systems.

  6. THz radiation at plasma frequency in ultrashort two-color laser plasma

    CERN Document Server

    Li, Na; Miao, Tianshi; Liu, Peng; Li1, Ruxin; Xu, Zhizhan

    2016-01-01

    Contribution of plasma oscillation to the broadband terahertz (THz) emission is revealed by interacting two-color laser pulses with a supersonic jet of nitrogen molecules. Temporal and spectral shifts of THz waves are observed as the plasma density varies. The former owes to the changing refractive index of the THz waves, and the latter correlates to the varying plasma frequency. The broadband low-frequency spectrum of the THz emission by the two-color pulses suggests the mechanism that includes the radiations from both the transient photocurrents and plasma oscillations.

  7. Novel concepts for terahertz waveguide spectroscopy

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd

    2009-01-01

    In the recent years there has been a tremendous interest in various waveguides for the THz range. A waveguide offers strong confinement of the field as well as low-loss propagation over significant distances, properties which are important for sensitive spectroscopy. The confinement of the field...... leads to high sensitivity, and the long propagation distance further allows high spectral resolution. In this presentation we will review our recent work on metallic parallel-plate waveguides (PPWGs). The PPWG is an appealing waveguide geometry for THz spectroscopic applications due to its low loss...... and low dispersion [1]. In contrast to previous work on PPWG we have applied transparent metallization to the waveguide. The transparent metallization allows optical access to the dielectric-filled waveguide, and hence spectroscopy of photoinduced processes in the PPWG becomes possible...

  8. 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...... of the whole structure. Placed inside a hollow waveguide, a multilayer graphene/dielectric metamaterial provides high-speed modulation of radiation and offers novel concepts for terahertz modulators and tunable bandpass filters. We exemplify it showing performance of waveguide-based terahertz modulators...

  9. A Simple Birefringent Terahertz Waveguide Based on Polymer Elliptical Tube

    Institute of Scientific and Technical Information of China (English)

    WANG Jing-Li; YAO Jian-Quan; CHEN He-Ming; LI Zhong-Yang

    2011-01-01

    We propose a simple birefringent terahertz (THz) waveguide which is a polymer elliptical tube with a cross section of elliptical ring structure. It can be achieved by stretching a normal circular-tube in one direction. Simulations based on the full-vector finite element method (FEM) show that this kind of waveguides exhibits high birefringence on a level of 10-2 over a wide THz frequency range. Moreover, as a majority of modal power is trapped in the air core inside the polymer elliptical tube, the THz waveguide guiding loss caused by material absorption can be reduced effectively.

  10. 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.

  11. Simplified THz Instrumentation for High-Field DNP-NMR Spectroscopy

    OpenAIRE

    Maly, Thorsten; Sirigiri, Jagadishwar R.

    2012-01-01

    We present an alternate simplified concept to irradiate a nuclear magnetic resonance sample with terahertz (THz) radiation for dynamic nuclear polarization (DNP) experiments using the TE01 circular waveguide mode for transmission of the THz power and the illumination of the DNP sample by either the TE01 or TE11 mode. Using finite element method and 3D electromagnetic simulations we demonstrate that the average value of the transverse magnetic field induced by the THz radiation and responsible...

  12. 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

  13. 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.

  14. Self-referenced ultra-broadband transient terahertz spectroscopy using air-photonics.

    Science.gov (United States)

    D'Angelo, F; Němec, H; Parekh, S H; Kužel, P; Bonn, M; Turchinovich, D

    2016-05-01

    Terahertz (THz) air-photonics employs nonlinear interactions of ultrashort laser pulses in air to generate and detect THz pulses. As air is virtually non-dispersive, the optical-THz phase matching condition is automatically met, thus permitting the generation and detection of ultra-broadband THz pulses covering the entire THz spectral range without any gaps. Air-photonics naturally offers unique opportunities for ultra-broadband transient THz spectroscopy, yet many critical challenges inherent to this technique must first be resolved. Here, we present explicit guidelines for ultra-broadband transient THz spectroscopy with air-photonics, including a novel method for self-referenced signal acquisition minimizing the phase error, and the numerically-accurate approach to the transient reflectance data analysis. PMID:27137624

  15. 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...

  16. THz wave emission microscope

    Science.gov (United States)

    Yuan, Tao

    Sensing and imaging using Terahertz (THz) radiation has attracted more and more interest in the last two decades thanks to the abundant material 'finger prints' in the THz frequency range. The low photon energy also makes THz radiation an attractive tool for nondestructive evaluation of materials and devices, biomedical applications, security checks and explosive screening. Due to the long wavelength, the far-field THz wave optical systems have relatively low spatial resolution. This physical limitation confines THz wave sensing and imaging to mostly macro-size samples. To investigate local material properties or micro-size structures and devices, near-field technology has to be employed. In this dissertation, the Electro-Optical THz wave emission microscope is investigated. The basic principle is to focus the femtosecond laser to a tight spot on a thin THz emitter layer to produce a THz wave source with a similar size as the focus spot. The apparatus provides a method for placing a THz source with sub-wavelength dimension in the near-field range of the investigated sample. Spatial resolution to the order of one tenth of the THz wavelength is demonstrated by this method. The properties of some widely used THz wave emission materials under tight focused pump light are studied. As an important branch of THz time domain spectroscopy (THz-TDS), THz wave emission spectroscopy has been widely used as a tool to investigate the material physics, such as energy band structure, carrier dynamics, material nonlinear properties and dynamics. As the main work of this dissertation, we propose to combine the THz wave emission spectroscopy with scanning probe microscopy (SPM) to build a tip-assisted THz wave emission microscope (TATEM), which is a valuable extension to current SPM science and technology. Illuminated by a femtosecond laser, the biased SPM tip forms a THz wave source inside the sample beneath the tip. The source size is proportional to the apex size of the tip so

  17. Broadband mode conversion via gradient index metamaterials.

    Science.gov (United States)

    Wang, HaiXiao; Xu, YaDong; Genevet, Patrice; Jiang, Jian-Hua; Chen, HuanYang

    2016-04-21

    We propose a design for broadband waveguide mode conversion based on gradient index metamaterials (GIMs). Numerical simulations demonstrate that the zeroth order of transverse magnetic mode or the first order of transverse electric mode (TM0/TE1) can be converted into the first order of transverse magnetic mode or the second order of transverse electric mode (TM1/TE2) for a broadband of frequencies. As an application, an asymmetric propagation is achieved by integrating zero index metamaterials inside the GIM waveguide.

  18. 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.

  19. Broadband Single-Ridge Waveguide Slot Antenna Design%宽带单脊波导缝隙天线的设计

    Institute of Scientific and Technical Information of China (English)

    张文涛; 杨晖; 稂华清

    2011-01-01

    From the transmission line equations single ridge waveguide slot active admittance formula is derived.With three-dimensional electromagnetic simulation software HFSS,the active radiation conductance of the gap in the antenna are obtained.An 8-element single ridge waveguide slot array is designed.Experimental results show that the side lobe is-23.61dB,relative bandwidth for VSWR less than 2 is about 8%,which is about 2 times of that in rectangular waveguide slot antenna.%根据传输线方程推导了单脊波导辐射缝隙有源导纳的计算公式,结合三维电磁仿真软件HFSS提取了天线阵列中辐射缝隙的有源电导,设计了一个8元单脊波导缝隙线阵,实测结果表明,副瓣为-23.61dB,VSWR≤2时的相对带宽为8%,约为矩形波导缝隙天线的2倍。

  20. Spectral modification of the laser emission of a terahertz quantum cascade laser induced by broad-band double pulse injection seeding

    Energy Technology Data Exchange (ETDEWEB)

    Markmann, Sergej, E-mail: sergej.markmann@ruhr-uni-bochum.de; Nong, Hanond, E-mail: nong.hanond@ruhr-uni-bochum.de; Hekmat, Negar; Jukam, Nathan [AG Terahertz Spektroskopie und Technologie, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Pal, Shovon [AG Terahertz Spektroskopie und Technologie, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Scholz, Sven; Kukharchyk, Nadezhda; Ludwig, Arne; Wieck, Andreas D. [Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Dhillon, Sukhdeep; Tignon, Jérôme [Laboratoire Pierre Aigrain, Ecole Normale Supérieure, UMR 8551 CNRS, UPMC, Univ. Paris 6, 75005 Paris (France); Marcadet, Xavier [Alcatel-Thales III-V Lab, Route Départementale 128, 91767 Palaiseau Cedex (France); Bock, Claudia; Kunze, Ulrich [Lehrstuhl für Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

    2015-09-14

    We demonstrate by injection seeding that the spectral emission of a terahertz (THz) quantum cascade laser (QCL) can be modified with broad-band THz pulses whose bandwidths are greater than the QCL bandwidth. Two broad-band THz pulses delayed in time imprint a modulation on the single THz pulse spectrum. The resulting spectrum is used to injection seed the THz QCL. By varying the time delay between the THz pulses, the amplitude distribution of the QCL longitudinal modes is modified. By applying this approach, the QCL emission is reversibly switched from multi-mode to single mode emission.

  1. Coherent broadband light source for parallel optical coherence tomography

    NARCIS (Netherlands)

    Rivier, S.; Laversenne, L.; Bourquin, S.; Salathé, R.P.; Pollnau, M.; Grivas, C.; Shepherd, D.P.; Eason, R.W.; Flury, M.; Philipoussis, I.; Herzig, H.P.

    2004-01-01

    A Ti:sapphire planar waveguide is rib structured by Ar ion milling to provide parallel channel waveguides. By coupling high-power pump light through a microlens array into the waveguides, a novel broadband luminescent parallel emitter is demonstrated as a light source for parallel optical coherence

  2. Metal-loaded graphene surface plasmon waveguides working in the terahertz regime

    DEFF Research Database (Denmark)

    Xiao, Binggang; Qin, Kang; Xiao, Sanshui;

    2015-01-01

    A metal-loaded graphene surface plasmon waveguide composed of a thin silica layer sandwiched between a graphene layer and a metal stripe is proposed and the waveguiding properties in the THz regime are numerically investigated. The results show that the fundamental mode of the proposed waveguide ...

  3. Low-loss terahertz ribbon waveguides

    Science.gov (United States)

    Yeh, Cavour; Shimabukuro, Fred; Siegel, Peter H.

    2005-10-01

    The submillimeter wave or terahertz (THz) band (1 mm-100 µm) is one of the last unexplored frontiers in the electromagnetic spectrum. A major stumbling block hampering instrument deployment in this frequency regime is the lack of a low-loss guiding structure equivalent to the optical fiber that is so prevalent at the visible wavelengths. The presence of strong inherent vibrational absorption bands in solids and the high skin-depth losses of conductors make the traditional microstripline circuits, conventional dielectric lines, or metallic waveguides, which are common at microwave frequencies, much too lossy to be used in the THz bands. Even the modern surface plasmon polariton waveguides are much too lossy for long-distance transmission in the THz bands. We describe a concept for overcoming this drawback and describe a new family of ultra-low-loss ribbon-based guide structures and matching components for propagating single-mode THz signals. For straight runs this ribbon-based waveguide can provide an attenuation constant that is more than 100 times less than that of a conventional dielectric or metallic waveguide. Problems dealing with efficient coupling of power into and out of the ribbon guide, achieving low-loss bends and branches, and forming THz circuit elements are discussed in detail. One notes that active circuit elements can be integrated directly onto the ribbon structure (when it is made with semiconductor material) and that the absence of metallic structures in the ribbon guide provides the possibility of high-power carrying capability. It thus appears that this ribbon-based dielectric waveguide and associated components can be used as fundamental building blocks for a new generation of ultra-high-speed electronic integrated circuits or THz interconnects.

  4. An All-Cryogenic THz Transmission Spectrometer

    CERN Document Server

    Burke, P J; Pfeiffer, L N; West, K W

    2001-01-01

    This paper describes a THz transmission spectrometer for the spectral range of 2-65 cm^-1 (100 GHz to 2 THz) with a spectral resolution of at least 1.8 cm^-1 (50 GHz) where the source, sample, and detector are all fully contained in a cryogenic environment. Cyclotron emission from a two-dimensional electron gas heated with an electrical current serves as a magnetic field tunable source. The spectrometer is demonstrated at 4.2 K by measuring the resonant cyclotron absorption of a second two dimensional electron gas. Unique aspects of the spectrometer are that 1) an ultra-broadband detector is used and 2) the emitter is run quasi-continuously with a chopping frequency of only 1 Hz. Since optical coupling to room temperature components is not necessary, this technique is compatible with ultra-low temperature (sub 100 mK) operation.

  5. Broadband terahertz generation and detection at 10 nm scale.

    Science.gov (United States)

    Ma, Yanjun; Huang, Mengchen; Ryu, Sangwoo; Bark, Chung Wung; Eom, Chang-Beom; Irvin, Patrick; Levy, Jeremy

    2013-06-12

    Terahertz (0.1-30 THz) radiation reveals a wealth of information that is relevant for material, biological, and medical sciences with applications that span chemical sensing, high-speed electronics, and coherent control of semiconductor quantum bits. To date, there have been no methods capable of controlling terahertz (THz) radiation at molecular scales. Here we report both generation and detection of broadband terahertz field from 10 nm scale oxide nanojunctions. Frequency components of ultrafast optical radiation are mixed at these nanojunctions, producing broadband THz emission. These same devices detect THz electric fields with comparable spatial resolution. This unprecedented control, on a scale of 4 orders of magnitude smaller than the diffraction limit, creates a pathway toward THz-bandwidth spectroscopy and control of individual nanoparticles and molecules.

  6. Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

    International Nuclear Information System (INIS)

    Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz

  7. Polymer microstructured fibers for guiding of THz radiation

    DEFF Research Database (Denmark)

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

    2010-01-01

    spectroscopic investigations of minute sample quantities [3]. In this presentation we will describe our current efforts in the development, fabrication and characterization of a class of THz waveguides and components based on microstructured polymer optical fibers (mPOF’s) [4] designed for the THz frequency...... range [5]. Fabrication and characterization of tailored mPOF’s Similar to photonic crystal fibers for the near-infrared, we fabricate our mPOF structures in a fiber draw tower. Based on numerical simulations, a fiber cross section is first designed using standard and custom finite-element methods...

  8. Metamaterial-based gradient index lens with strong focusing in the THz frequency range

    CERN Document Server

    Neu, Jens; Paul, Oliver; Reinhard, Benjamin; Beigang, René; Rahm, Marco

    2010-01-01

    The development of innovative terahertz (THz) imaging systems has recently moved in the focus of scientific efforts due to the ability to screen substances through textiles or plastics. The invention of THz imaging systems with high spatial resolution is of increasing interest for applications in the realms of quality control, spectroscopy in dusty environment and security inspections. One of the main restrictions of current THz imaging systems is the low spatial resolution which is limited by a lack of THz lenses with strong focusing capabilities. Here we present the design, fabrication and the measurement of the optical properties of spectrally broadband metamaterial-based gradient index (GRIN) lenses that allow one to focus THz radiation to a spot diameter smaller than the wavelength. Due to the subwavelength thickness and the high focusing strength the presented GRIN lenses are an important step towards compact THz imaging systems with strongly improved spatial resolution.

  9. Design of a plasmonic-organic hybrid slot waveguide integrated with a bowtie-antenna for terahertz wave detection

    Science.gov (United States)

    Zhang, Xingyu; Chung, Chi-Jui; Subbaraman, Harish; Pan, Zeyu; Chen, Chin-Ta; Chen, Ray T.

    2016-03-01

    Electromagnetic (EM) wave detection over a large spectrum has recently attracted significant amount of attention. Traditional electronic EM wave sensors use large metallic probes which distort the field to be measured and also have strict limitations on the detectable RF bandwidth. To address these problems, integrated photonic EM wave sensors have been developed to provide high sensitivity and broad bandwidth. Previously we demonstrated a compact, broadband, and sensitive integrated photonic EM wave sensor, consisting of an organic electro-optic (EO) polymer refilled silicon slot photonic crystal waveguide (PCW) modulator integrated with a gold bowtie antenna, to detect the X band of the electromagnetic spectrum. However, due to the relative large RC constant of the silicon PCW, such EM wave sensors can only work up to tens of GHz. In this work, we present a detailed design and discussion of a new generation of EM wave sensors based on EO polymer refilled plasmonic slot waveguides in conjunction with bowtie antennas to cover a wider electromagnetic spectrum from 1 GHz up to 10THz, including the range of microwave, millimeter wave and even terahertz waves. This antennacoupled plasmonic-organic hybrid (POH) structure is designed to provide an ultra-small RC constant, a large overlap between plasmonic mode and RF field, and strong electric field enhancement, as well as negligible field perturbation. A taper is designed to bridge silicon strip waveguide to plasmonic slot waveguide. Simulation results show that our device can have an EM wave sensing ability up to 10 THz. To the best of our knowledge, this is the first POH device for photonic terahertz wave detection.

  10. Fractal THz metamaterials

    DEFF Research Database (Denmark)

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

    2010-01-01

    The concept of metamaterials (MTMs) is acknowledged for providing new horizons for controlling electromagnetic radiations thus their use in frequency ranges otherwise difficult to manage (e.g. THz radiation) broadens our possibility to better understand our world as well as opens the path for new...... 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...... wavelength of THz radiation, the resolution requirements for fabrication of metamaterials are within the optical lithography range. However, the high aspect ratio of such structures as well as the substrate thickness pose challenges in the fabrication process. The measurements were made using terahertz time...

  11. Effects of chirp of pump pulses on broadband terahertz pulse spectra generated by optical rectification

    Science.gov (United States)

    Hamazaki, Junichi; Furusawa, Kentaro; Sekine, Norihiko; Kasamatsu, Akifumi; Hosako, Iwao

    2016-11-01

    The effects of the chirp of the pump pulse in broadband terahertz (THz) pulse generation by optical rectification (OR) in GaP were systematically investigated. It was found that the pre-compensation for the dispersion of GaP is important for obtaining smooth and single-peaked THz spectra as well as high power-conversion efficiency. It was also found that an excessive amount of chirp leads to distortions in THz spectra, which can be quantitatively analyzed by using a simple model. Our results highlight the importance of accurate control over the chirp of the pump pulse for generating broadband THz pulses by OR.

  12. Metamaterial Composite with an Ultra-Broadband Usable Range of over 25 Terahertz

    DEFF Research Database (Denmark)

    Strikwerda, Andrew; Zalkovskij, Maksim; Krabbe, Alexander;

    2014-01-01

    Using a metamaterial composite , we demonstrate a band pass filter that has only a single transmission mode from 0 to >25 THz. This usable bandwidth match es , or e xceed s , that of current ly used THz sources and demonstrates a path towards broadband metamaterial design.......Using a metamaterial composite , we demonstrate a band pass filter that has only a single transmission mode from 0 to >25 THz. This usable bandwidth match es , or e xceed s , that of current ly used THz sources and demonstrates a path towards broadband metamaterial design....

  13. Experimental and computational investigations of the THz spectra of dipeptide nanotubes

    Science.gov (United States)

    Siegrist, K. M.; Pfefferkorn, C.; Schwarzkopf, A.; Podobedov, V. B.; Plusquellic, D. F.

    2008-02-01

    Continuous wave THz spectroscopy has been used to obtain spectra for four isostructural dipeptide nanotubes at 4.2K from 2 cm -1 to 100 cm -1 (0.05 to 3 THz). Line-narrowing of spectral features by a factor of 2 to 4 is observed for the crystalline dipeptide films investigated by absorption spectroscopy using a plane parallel waveguide, compared to spectra from pressed disks of polyethylene-diluted samples. The x-ray determined crystal structures of these peptides formed the basis for a parallel computational investigation. Spectral predictions from the ab initio level computational package DMOL 3 and the empirical force field model CHARMM22 are compared to the experimentally obtained THz absorption spectra. The THz waveguide spectroscopy technique can provide information on the orientation-dependent dipole coupling of the vibrational modes, which can aid in validating computational models.

  14. A Multichannel THz Detector Using Integrated Bow-Tie Antennas

    OpenAIRE

    Hairui Liu; Junsheng Yu; Peter Huggard; Byron Alderman

    2013-01-01

    This paper presents a kind of a multichannel THz detector using lens-based bow-tie array. A hyperhemispherical silicon lens is employed to provide a focal plane; 8 bow-tie elements are arranged on the focal plane with careful design to show a performance of broadband, high gain, well compact, and easy assembling. These characteristics of the detector are preferred for detecting weak THz signal. Measured far field shows that the radiation pattern of each element is shifted angularly, by ≈9°, w...

  15. 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.

  16. Introduction to THz wave photonics

    CERN Document Server

    Zhang, X-C

    2009-01-01

    Introduction to THz Wave Photonics examines the science and technology related to terahertz wave technologies, taking a dual approach between presenting the field 's history while simultaneously providing an overview of existing technology. The latest research in developing THz areas such as electromagnetic waves are presented, along with an introduction to continuous wave THz technology. Authors X.-C. Zhang and Jingzhou Xu place particular emphasis on pulsed THz technology, among many other facets of THz technology including: Complete coverage of THz wave spectroscopy and imagingA discussion

  17. Terahertz-frequency waveguide HEB mixers for spectral line astronomy

    Science.gov (United States)

    Boussaha, Faouzi; Kawamura, Jonathan; Stern, Jeffery; Jung, Cecile; Skalare, Anders; White, Victor

    2012-09-01

    We report on the development of waveguide-based mixers for operation beyond 2 THz. The mixer element is a superconducting hot-electron bolometer (HEB) fabricated on a silicon-on-insulator (SOI) substrate. Because it is beyond the capability of conventional machining techniques to produce the fine structures required for the waveguide embedding circuit for use at such high frequencies, we employ two lithography-based approaches to produce the waveguide circuit: a metallic micro-plating process akin to 3-D printing and deep reactive ion etching (DRIE) silicon micromachining. Various mixer configurations have been successfully produced using these approaches. A single-ended mixer produced by the metal plating technique has been demonstrated with a receiver noise temperature of 970 K (DSB) at a localoscillator frequency of 2.74 THz. A similar mixer, produced using a silicon-based micro-machining technique, has a noise temperature of 2000 K (DSB) at 2.56 THz. In another example, we have successfully produced a waveguide RF hybrid for operation at 2.74 THz. This is a key component in a balanced mixer, a configuration that efficiently utilizes local oscillator power, which is scarce at these frequencies. In addition to allowing us to extend the frequency of operation of waveguide-based receivers beyond 2 THz, these technologies we employ here are amenable to the production of large array receivers, where numerous copies of the same circuit, precisely the same and aligned to each other, are required.

  18. Light-Sound Interaction in Nanoscale Silicon Waveguides

    CERN Document Server

    Van Laer, Raphaël

    2016-01-01

    This thesis studies the interaction between near-infrared light and gigahertz sound in nanoscale silicon waveguides. Chapter 2 introduces photon-phonon coupling and its theoretical description, describing basic mechanisms and developing a quantum field theory of the process. Chapter 3 explores the dynamical effects in both waveguides and cavities. It also proves a connection between the Brillouin gain coefficient and the vacuum coupling rate. Chapter 4 deals with the observation of Brillouin scattering in nanoscale silicon waveguides. The waveguides tightly confine $193 \\, \\text{THz}$ light and $10 \\, \\text{GHz}$ acoustic vibrations. The acoustic quality factor remains limited to about $300$ because of leakage into silica substrate. These waveguides are optically transparent in a narrow band of frequencies at a pump power of $25 \\, \\text{mW}$. Besides this amplification, we translate a $10 \\, \\text{GHz}$ microwave signal across $1 \\, \\text{THz}$. Chapter 5 extends the experimental work of chapter 4 by fabrica...

  19. Graphene nano-ribbon waveguides

    CERN Document Server

    He, S; He, Y

    2013-01-01

    Graphene as a one-atom-thick platform for infrared metamaterial plays an important role in optical science and engineering. Here we study the unique properties of some plasmonic waveguides based on graphene nano-ribbon. It is found that a graphene ribbon of finite width leads to the occurrence of coupled edge mode. The single-mode region of a single freestanding graphene ribbon is identified at a fixed frequency of 30 THz. A low-loss waveguide structure, consisting of a graphene layer, a silica buffer layer and silicon substrate is proposed to reduce the propagation loss and obtain a high figure of merit for future integration of waveguide devices. Furthermore, two coupled ribbon configurations, namely, side-side coupling and top-bottom coupling, are investigated. As a device example, a nano-ring cavity of ultra-small size is designed.

  20. Compact narrow-band THz radiation source based on photocathode rf gun

    International Nuclear Information System (INIS)

    Narrow-band THz coherent Cherenkov radiation can be driven by a subpicosecond electron bunch traveling along the axis of a hollow cylindrical dielectric-lined waveguide. We present a scheme of compact THz radiation source based on the photocathode rf gun. On the basis of our analytic result, the subpicosecond electron bunch with high charge (800 pC) can be generated directly in the photocathode rf gun. According to the analytical and simulated results, a narrow emission spectrum peaked at 0.24 THz with 2 megawatt (MW) peak power is expected to gain in the proposed scheme (the length of the facility is about 1.2 m). (authors)

  1. Quantum well intersubband THz lasers and detectors

    Science.gov (United States)

    Soref, Richard A.; Friedman, Lionel R.; Sun, Gregory; Noble, Michael J.; Ram-Mohan, L. R.

    1999-11-01

    This paper presents modeling and simulation results on Si- based quantum-well intersubband THz detectors and THz lasers (tasers) in the 3 to 10 THz range where the intersubband transition energy is 12 to 41 meV. The incoherent cryogenically cooled (4 K to 20 K) quantum well terahertz detector (QWTD) consists of p-type Si0.9Ge0.1 QWs with Si barriers on an Si substrate, or of p-Si0.85Ge0.15/Si on a relaxed Si0.97Ge0.03 buffer on Si. The QWTD senses THz radiation at normal incidence (the XY polarization on the HH1 to LH1 transition) or at edge- illumination (the Z polarization on the HH1 to HH2 transition). Resonant-cavity enhancement, coupling to Si THz waveguides, and integration with SiGe transistor preamplifiers appear feasible for QWTDs. The quantum staircase taser is a simplified far-infrared version of the quantum cascade laser in which each superlattice transfer region is replaced by a thin tunnel-barrier layer. We have adapted to group IV the III-V idea of Sun, Lu, and Khurgin; the `inverted mass taser'. On a Si0.81Ge0.19 substrate, we find that an inverted effective mass exists in LH1 at kg equals 0.013 angstroms-1 in 9-nm single- wells of Si0.7Ge0.3 with 5-nm Si barriers. Selective electrical injection of holes into LH1 at T equals 77 K is postulated. This offers local-in-k-space LH1-HH1 population inversion and tasing at 7.2 THz. Since the taser emission is XY-polarized, the active MQW staircase (a set of identical square QWs) is suitable for insertion into a vertical cavity surface-emitting taser. The VCSET would have resonator thickness of (lambda) /2n equals 6 micrometers , and Bragg mirrors constructed from SiO2/Si multilayers.

  2. 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...

  3. Ultra-wide Bandwidth Inter-Chip Interconnects for Heterogeneous Millimeter-Wave and THz Circuits

    Science.gov (United States)

    Fay, Patrick; Bernstein, Gary H.; Lu, Tian; Kulick, Jason M.

    2016-09-01

    Heterogeneous chip-to-chip interconnects with low loss and ultra-wide bandwidths have been demonstrated. Coplanar waveguide-based interconnects between GaAs and Si die have been fabricated and characterized and the results compared to expectations from full-wave electromagnetic simulation. Broadband transmission characteristics were obtained, with insertion losses below 0.3 dB at 100 GHz and below 0.8 dB at frequencies up to 220 GHz demonstrated experimentally. The measured return loss exceeded 11.5 dB at all frequencies up to 220 GHz. The interconnects offer low latency, with a measured group delay of 0.69 ps. The measured results are in good agreement with full-wave simulations, indicating that the measured results do not suffer from significant impairments compared to theoretical predictions. The demonstrated interconnects offer an alternative to conventional approaches to millimeter-wave circuit and system integration, by enabling the compact realization of circuits in the microwave, millimeter-wave, sub-millimeter-wave, and THz frequency regimes in heterogeneous device technologies with very low chip-to-chip insertion loss.

  4. 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....... Our interest lies in metamaterials for a broad spectrum of linear properties in operations with THz waves, such as linear and circular polarizers, absorbers and devices with enhanced transmittivity, single layer dichroic and chiral systems. All the three steps (modelling, fabrication...

  5. THz generation using a reflective stair-step echelon

    CERN Document Server

    Ofori-Okai, Benjamin K; Huang, W Ronny; Nelson, Keith A

    2015-01-01

    We present a novel method for THz generation in lithium niobate using a reflective stair-step echelon structure. The echelon produces a discretely tilted pulse front with less angular dispersion compared to a high groove-density grating. The THz output was characterized using both a 1-lens and 3-lens imaging system to set the tilt angle at room and cryogenic temperatures. Using broadband 800 nm pulses with a pulse energy of 0.95 mJ and a pulse duration of 70 fs (24 nm FWHM bandwidth, 39 fs transform limited width), we produced THz pulses with field strengths as high as 500 kV/cm and pulse energies as high as 3.1 $\\mu$J. The highest conversion efficiency we obtained was 0.33%. In addition, we find that the echelon is easily implemented into an experimental setup for quick alignment and optimization.

  6. A Multichannel THz Detector Using Integrated Bow-Tie Antennas

    Directory of Open Access Journals (Sweden)

    Hairui Liu

    2013-01-01

    Full Text Available This paper presents a kind of a multichannel THz detector using lens-based bow-tie array. A hyperhemispherical silicon lens is employed to provide a focal plane; 8 bow-tie elements are arranged on the focal plane with careful design to show a performance of broadband, high gain, well compact, and easy assembling. These characteristics of the detector are preferred for detecting weak THz signal. Measured far field shows that the radiation pattern of each element is shifted angularly, by ≈9°, which can be used for THz imaging. Tested responsivity of the detector shows a good spectral performance from 260 to 400 GHz: respective values were ≥220 V/W, and the best NEP is achieved at about 60 pW/. Besides that, the proposed antenna has advantages of simple structure, easy fabrication, and low cost.

  7. THz Plasma Diagnostics: an evolution from FIR and Millimeter waves historical applications

    Science.gov (United States)

    Bombarda, F.; Doria, A.; Galatola Teka, G.; Giovenale, E.; Zerbini, M.

    2016-08-01

    Extremely broadband (100 GHz–30 THz) single cycle THz pulses are routinely generated with femtosecond laser for Time Domain Spectroscopy applications (TDS). The wide frequency range has an unquestionable diagnostic potential for Tokamak plasmas and not surprisingly THz TDS finds a natural field of application in this area, which is an evolution of the FIR and millimeter waves diagnostics, where ENEA Frascati holds historical expertise. By illuminating the plasma with a THz beam, phase, intensity and polarization of both reflected and transmitted beams can be detected, devising a single diagnostic instrument capable of measuring multiple plasma parameters. We will describe and discuss the laboratory work now in progress to realise a tailored THz-TDS spectrometer with design parameters optimised for the requirements of Tokamak plasmas and the tests of optical fibers and quasioptical couplers to optimise access to plasma. ENEA Frascati and the Photonics group of Physics Dept. of Oxford University are collaborating on this subject [1].

  8. THz spectrum of reduced glutathione

    Institute of Scientific and Technical Information of China (English)

    WANG; Weining; YAN; Haitao; YUE; Weiwei; ZHAO; Guozhong; Z

    2005-01-01

    The optical characteristics of reduced glutathione molecules between 0.2 THz and 2.4 THz have been investigated by THz time-domain spectroscopy (THz-TDS). The absorption characteristics and optical parameters of the reduced glutathione purged with Nitrogen at room temperature were obtained experimentally. The measured results were fitted well with the theoretical results computed by using Density Functional Theory (DFT) in far-infrared range. Also the conformation of the reduced glutathione molecule was simulated by Gaussian 03. This work has demonstrated significantly that THz-TDS spectroscopy can further be used to study other biological molecules in biological and biomedical engineering.

  9. The study of gas species on THz generation from laser-induced air plasma

    Science.gov (United States)

    Zhao, Ji; Zhang, LiangLiang; Wu, YiJian; Wu, Tong; Yuan, Hui; Zhang, CunLin; Zhao, YueJin

    2015-08-01

    Intense Terahertz waves generated from air-induced plasma and serving as broadband THz source provide a promising broadband source for innovative technology. Terahertz generation in selected gases has attracted more and more researchers' interests in recent years. In this research, the THz emission from different atoms is described, such as nitrogen, argon and helium in Michelson. The THz radiation is detected by a Golay Cell equipped with a 6-mm-diameter diamond-inputting window. It can be seen in the first time that when the pump power lies at a stable level, the THz generation created by the femtosecond laser focusing on the nitrogen is higher than which focusing on the helium, and lower than that produced in the argon gas environment. We believe that the THz intensity is Ar > N > Ne because of its atomic mass, which is Ar > N > Ne as well. It is clear that the Gas molecular decides the release of free electrons ionized from ultra short femtosecond laser through the electronic dynamic analysis. The higher the gas mass is, the stronger the terahertz emission will be. We further explore the THz emission at the different laser power levels, and the experimental results can be commendably quadratic fitted. It can be inferred that THz emission under different gas medium environment still complies with the law of four-wave mixing (FWM) process and has nothing to do with the gas environment: the radiation energy is proportional to the quadratic of incident laser power.

  10. Organic-inorganic composites for THz device fabrication

    Science.gov (United States)

    Cai, B.; Ye, T. M.; Bo, G.; Wang, X. C.; Li, Y. Z.; Zhu, Y. M.; Sugihara, O.

    2016-02-01

    In this paper, several organic-inorganic composites were prepared for Terahertz (THz) devices fabrication. First, a two-layer structure was designed for femtosecond (fs) laser/THz radiation separation. The top layer was made by sintered 20-40 nm hollow quartz particles which can diffuse the incident fs laser thus decrease the power intensity. The bottom layer comprised of silicon 100 nm particles and cycle-olefine polymer (COP), by which the fs laser light can be greatly scattered and absorbed but THz radiation can propagate insusceptibly. With this two-layer structure a high efficient fs-laser/THz filter was fabricated successfully. Second, titania-polymer composites with a very high refractiveindex tunability and high transparency in the THz region were prepared. By controlling the blending ratio of the titania particle, a broad refractive-index tuning range from 1.5 to 3.1 was realized. Then, the composites were used to fabricate antireflective (AR) layers on a high-resistivity silicon (HR-Si) substrate. By utilizing the thermoplasticity of the titania- polymer composite, a graded-index structure was fabricated via a hot-embossing method. Because of the good refractive-index matching between the composite and the HR-Si substrate, a broadband AR layer was fabricated.

  11. 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.

  12. 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.)

  13. A broadband terahertz ultrathin multi-focus lens

    Science.gov (United States)

    He, Jingwen; Ye, Jiasheng; Wang, Xinke; Kan, Qiang; Zhang, Yan

    2016-06-01

    Ultrathin transmission metasurface devices are designed on the basis of the Yang-Gu amplitude-phase retrieval algorithm for focusing the terahertz (THz) radiation into four or nine spots with focal spacing of 2 or 3 mm at a frequency of 0.8 THz. The focal properties are experimentally investigated in detail, and the results agree well with the theoretical expectations. The designed THz multi-focus lens (TMFL) demonstrates a good focusing function over a broad frequency range from 0.3 to 1.1 THz. As a transmission-type device based on metasurface, the diffraction efficiency of the TMFL can be as high as 33.92% at the designed frequency. The imaging function of the TMFL is also demonstrated experimentally and clear images are obtained. The proposed method produces an ultrathin, low-cost, and broadband multi-focus lens for THz-band application

  14. Simplified THz Instrumentation for High-Field DNP-NMR Spectroscopy.

    Science.gov (United States)

    Maly, Thorsten; Sirigiri, Jagadishwar R

    2012-07-01

    We present an alternate simplified concept to irradiate a nuclear magnetic resonance sample with terahertz (THz) radiation for dynamic nuclear polarization (DNP) experiments using the TE(01) circular waveguide mode for transmission of the THz power and the illumination of the DNP sample by either the TE(01) or TE(11) mode. Using finite element method and 3D electromagnetic simulations we demonstrate that the average value of the transverse magnetic field induced by the THz radiation and responsible for the DNP effect using the TE(11) or the TE(01) mode are comparable to that generated by the HE(11) mode and a corrugated waveguide. The choice of the TE(11)/TE(01) mode allows the use of a smooth-walled, oversized waveguide that is easier to fabricate and less expensive than a corrugated waveguide required for transmission of the HE(11) mode. Also, the choice of the TE(01) mode can lead to a simplification of gyrotron oscillators that operate in the TE(0n) mode, by employing an on-axis rippled-wall mode converter to convert the TE(0n) mode into the TE(01) mode either inside or outside of the gyrotron tube. These novel concepts will lead to a significant simplification of the gyrotron, the transmission line and the THz coupler, which are the three main components of a DNP system. PMID:22977293

  15. Phase-locking of a 2.7-THz quantum cascade laser

    NARCIS (Netherlands)

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

    2010-01-01

    We successfully realized phase-locking of a 2.7-THz metal-metal waveguide quantum cascade laser (QCL) to a reference, which is generated from an external microwave signal by applying two stages of frequency multiplication. The reference is the 15th harmonic of a signal at 182 GHz, which is produced

  16. 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 (x1

  17. 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 (x1

  18. 0.14 THz基模多注折叠波导行波管的理论与模拟研究∗%Theoretical and simulation study of 0.14 THz fundamental mo de multi-b eam folded waveguide traveling wave tub e

    Institute of Scientific and Technical Information of China (English)

    颜胜美; 苏伟; 王亚军; 徐翱; 陈樟; 金大志; 向伟

    2014-01-01

    为解决THz行波管工作电流过小、输出功率低等问题,提出了基模多注工作模式的折叠波导行波管.首先,获得了基模多注折叠波导色散特性的等效传输线计算模型,并与数值模拟结果进行了比较;然后,对基模多注折叠波导的传输特性进行了模拟计算;最后,通过模拟和理论计算完成了0.14 THz基模多注折叠波导行波管的注波互作用特性分析.电子注参数为12 mA,15.75 kV时,获得的3 dB带宽为25 GHz (128—153 GHz),最大增益为33.61 dB,最大峰值功率为23 W;电子注参数为30 mA,15.75 kV时,在0.14 THz处获得了38 dB增益,最大脉冲输出功率为63.1 W.对比同条件下基模单注折叠波导行波管,3 dB带宽提升了1倍,0.14 THz处输出功率增大了9.66倍,互作用效率增大了3.22倍;当增益相同时,多注方式的互作用长度较单注缩短了33%.该方法能够有效增大THz行波管的工作电流,提高互作用增益及效率、3 dB带宽、输出功率;在增益相同时,基模多注行波管可以做得更短更紧凑.%To improve the current and output power of the THz traveling wave tube (TWT), a fundamental mode multi-beam folded waveguide (FMMBFW) TWT scheme is proposed. Firstly, an equivalent circuit model FMMBFW for calculating the high-frequency characteristic is established and compared with numerical simulation. Secondly, the transmission characteristic of 60 periods FMMBFW is analyzed. Finally, the beam-wave interaction characteristic of 0.14 THz FMMBFW TWT is completed by numerical simulation and theoretical calculation. When the DC current is 12 mA and the applied voltage is 15.75 kV, the 3 dB bandwidth of 0.14 THz FMMBFW TWT is 25 GHz (128–153 GHz), the maximum gain is 33.61 dB and the maximum output power is 23 W. When the DC current is 30 mA and the voltage is 15.75 kV, the maximum gain is 38 dB and the maximum pulse output power is 63.1 W at 0.14 THz. Compared with the fundamental single-beam folded

  19. Combless broadband terahertz generation with conventional laser diodes.

    Science.gov (United States)

    Molter, D; Wagner, A; Weber, S; Jonuscheit, J; Beigang, R

    2011-03-14

    We present a novel technique to generate a continuous, combless broadband Terahertz spectrum with conventional low-cost laser diodes. A standard time-domain spectroscopy system using photoconductive antennas is pumped by the output of two tunable diode lasers. Using fine tuning for one laser and fine and coarse tuning for the second laser, difference frequency generation results in a continuous broadband THz spectrum. Fast coarse-tuning is achieved by a simple spatial light modulator introduced in an external cavity. The results are compared to multi-mode operation for THz generation.

  20. Ex-vivo detection of neural events using THz BioMEMS

    CERN Document Server

    Abbas, Abdennour; Croix, Dominique; Salzet, Michel; Bocquet, Bertrand

    2009-01-01

    Background: Electromagnetic frequencies up to a few terahertz (THz) can yield real-time and noninvasive measurements on biological matter. Unfortunately, strong absorption in aqueous solutions and low spatial resolution return difficult free-space investigations. A new approach based on integrated THz circuits was used. The authors designed and fabricated a BioMEMS (Biological MicroElectro-Mechanical System) compatible with microfluidic circulation and electromagnetic propagation. It is dedicated to the ex vivo detection of nitric oxide synthase (NOS) activity, which is involved in neurodegenerative phenomena. Material/Methods: The biological model was a leech's central nervous system. After its injury, the production of NO was observed and measured in the far-THz spectral domain. The nerve cord was put inside a BioMEMS realized in polydimethylsiloxane (PDMS) sealed on a glass wafer. Glass is a good material for supporting high-frequency integrated waveguides such as coplanar waveguides (CPWs). Measurements w...

  1. Compact and high-power broadband terahertz source based on femtosecond photonic crystal fiber amplifier

    Institute of Scientific and Technical Information of China (English)

    Feng Liu; Lu Chai; Qirong Xing; Chingyue Wang; Weili Zhang; Xiaokun Hu; Jiang Li; Changlei Wang; Yi Li; Yanfeng Li; YoujianSong; Bowen Liu; Minglie Hu

    2011-01-01

    Terahertz (THz) waves,generally defined in the 0.1-10 THz range are finding growing applications in various important fields[1-4] such as imaging,food and pharmaceutical quality coutrol,security screening,and standoff detection of bio-threat species,among which THz timedomain spectroscopy (THz-TDS)[5] is particularly appealing.However,the low conversion efficiency and low power of typical broadband THz sources severely hinder the utility and realization of the full potential of THzTDS.Recently,there have been efforts to generate THz pulses using compact pump sources in fiber format[6,7].%We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier. The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient. Broadband THz pulseg of 150 μW extending from 0.1 to 3.5 TH2 are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 & and a repetition rate of 52 MHz. A strong saturation effect is observed, which is attributed to pump pulse absorption; a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1040 run. A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscope

  2. 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....

  3. 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....

  4. Linearly polarized single TM mode terahertz waveguide.

    Science.gov (United States)

    Li, Haisu; Ren, Guobin; Atakaramians, Shaghik; Kuhlmey, Boris T; Jian, Shuisheng

    2016-09-01

    We design a hollow-core terahertz (THz) waveguide guiding a single linearly polarized mode. This is achieved using a hybrid cladding, where we introduce a ring of subwavelength structures, including metal wires and air-holes. The wire-based cladding is extremely anisotropic, reflecting only transverse magnetic (TM) modes. The polarization of TM modes is further manipulated by replacing some wires with air-holes. Numerical simulations confirm the guidance of only an x-polarized TM2 mode over 0.36-0.46 THz in a wavelength-scale core (diameter of 1 mm). The propagation losses are of the order 0.25  dB/cm, with low bend losses <0.3  dB/cm at 0.4 THz for a bend radius of 5 cm. PMID:27607958

  5. Random Lasers for Broadband Directional Emission

    CERN Document Server

    Schönhuber, Sebastian; Hisch, Thomas; Deutsch, Christoph; Krall, Michael; Detz, Hermann; Strasser, Gottfried; Rotter, Stefan; Unterrainer, Karl

    2016-01-01

    Broadband coherent light sources are becoming increasingly important for sensing and spectroscopic applications, especially in the mid-infrared and terahertz (THz) spectral regions, where the unique absorption characteristics of a whole host of molecules are located. The desire to miniaturize such light emitters has recently lead to spectacular advances with compact on-chip lasers that cover both of these spectral regions. The long wavelength and the small size of the sources result in a strongly diverging laser beam that is difficult to focus on the target that one aims to perform spectroscopy with. Here, we introduce an unconventional solution to this vexing problem relying on a random laser to produce coherent broadband THz radiation as well as an almost diffraction limited far-field emission profile. Our random lasers do not require any fine-tuning and thus constitute a promising example of practical device applications for random lasing.

  6. Multi-channel terahertz wavelength division demultiplexer with defects-coupled photonic crystal waveguide

    Science.gov (United States)

    Li, Shaopeng; Liu, Hongjun; Sun, Qibing; Huang, Nan

    2016-05-01

    Terahertz (THz) wavelength division demultiplexer based on a compact defects-coupled photonic crystal waveguide is proposed and demonstrated numerically. This device consists of an input waveguide that perpendicularly coupled with a series of defects cavities, each of which captures the resonance frequency from the input waveguide. Coupled-mode theory and finite element method are used to analyze the transmission properties of the structure. It is found that the transmission wavelength centered around 1 THz can be adjusted by changing the geometrical parameters of defects cavities, which equals to THz waves generated by optical methods such as difference frequency generation and optical rectification. Applications in this frequency range are urgently needed. Furthermore, the highest transmission efficiency of 0.94 can be achieved when a perfect wavelength-selective mirror is set in the output waveguide.

  7. An Artificially Garnet Crystal Materials Using In Terahertz Waveguide

    Institute of Scientific and Technical Information of China (English)

    YANG Qing-Hui; ZHANG Huai-Wu; LIU Ying-Li; WEN Qi-Ye; ZHA Jie

    2008-01-01

    A hypothesis is brought forward that the materials with low propagation loss in both optical and microwave band may exhibit good performance in terahertz (THz) band because THz wave band interspaces those two wavebands. For the purpose of exploring a kind of low-loss material for THz waveguide, Lu2.1Bio.9FesO12(LuBiIG)garnet films are prepared by liquid phase epitaxy (LPE) method on a gadolinium gallium garnet (GGG) substrate from lead-free flux because of the good properties in both optical and microwave bands. In microwave band, the ferromagnetic resonance (FMR) linewidth of the film 2△H = 2.8-5.1 Oe; in optical band, the optical absorption coefficient is 600cm-1 at visible range and about 100-170cm-l when the wavelength is longer than 80Onm. In THz range, our hypothesis is well confirmed by a THz-TDS measurement which shows that the absorbance of the film for THz wave is 0.05-0.3 cm- 1 and the minimum value appears at 2.3 THz. This artificial ferromagnetic material holds a great promise for magnetic field tunable THz devices such as wavegnide, modulator or switch.

  8. 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...

  9. Resonant Terahertz InSb Waveguide Device for Sensing Polymers

    Science.gov (United States)

    Bhatt, Shourie Ranjana J.; Bhatt, Piyush; Deshmukh, Prathmesh; Sangala, Bagvanth R.; Satyanarayan, M. N.; Umesh, G.; Prabhu, S. S.

    2016-08-01

    We have demonstrated the possibility of employing a device, designed to operate at terahertz (THz) frequencies, for sensing materials. The device consists of a waveguide section with a pair of stubs located at the middle and oriented transversely to the waveguide axis. The two stubs function as a resonator and, hence, the device would behave as a filter in the THz domain. The device was fabricated by laser micromachining of InSb pellets and was characterized by THz time-domain transmission spectroscopy. For a waveguide width of 740 μm and stub length of 990 μm, a transmission minimum is seen to occur at 0.265 THz. We investigated the capability of the device to sense polystyrene, dissolved in toluene, loaded into the stubs. The consequent change in the refractive index in the stubs alters the transmitted signal intensity. Our results show that, a change in concentration of polystyrene even by 1 mol/L, leads to measurable change in the transmission coefficient close to the resonant frequency of the device. Thus, our device operating at THz frequencies shows promising potential as chemical and bio sensors.

  10. Kinetic inductance driven nanoscale 2D and 3D THz transmission lines.

    Science.gov (United States)

    Mousavi, S Hossein; Williamson, Ian A D; Wang, Zheng

    2016-05-03

    We examine the unusual dispersion and attenuation of transverse electromagnetic waves in the few-THz regime on nanoscale graphene and copper transmission lines. Conventionally, such propagation has been considered to be highly dispersive, due to the RC time constant-driven voltage diffusion below 1 THz and plasmonic effects at higher optical frequencies. Our numerical modeling across the microwave, THz, and optical frequency ranges reveals that the conductor kinetic inductance creates an ultra-broadband linear-dispersion and constant-attenuation region in the THz regime. This so-called LC region is an ideal characteristic that is known to be absent in macro-scale transmission lines. The kinetic-LC frequency range is dictated by the structural dimensionality and the free-carrier scattering rate of the conductor material. Moreover, up to 40x wavelength reduction is observed in graphene transmission lines.

  11. Kinetic inductance driven nanoscale 2D and 3D THz transmission lines

    Science.gov (United States)

    Mousavi, S. Hossein; Williamson, Ian A. D.; Wang, Zheng

    2016-01-01

    We examine the unusual dispersion and attenuation of transverse electromagnetic waves in the few-THz regime on nanoscale graphene and copper transmission lines. Conventionally, such propagation has been considered to be highly dispersive, due to the RC time constant-driven voltage diffusion below 1 THz and plasmonic effects at higher optical frequencies. Our numerical modeling across the microwave, THz, and optical frequency ranges reveals that the conductor kinetic inductance creates an ultra-broadband linear-dispersion and constant-attenuation region in the THz regime. This so-called LC region is an ideal characteristic that is known to be absent in macro-scale transmission lines. The kinetic-LC frequency range is dictated by the structural dimensionality and the free-carrier scattering rate of the conductor material. Moreover, up to 40x wavelength reduction is observed in graphene transmission lines. PMID:27137628

  12. Freely-tunable broadband polarization rotator for terahertz waves

    Science.gov (United States)

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

    It is known that commercially-available terahertz (THz) emitters usually generate linearly polarized waves only along certain directions, but in practice, a polarization rotator that is capable of rotating the polarization of THz waves to any direction is particularly desirable and it will have various important applications. In this work, we demonstrate a freely tunable polarization rotator for broadband THz waves using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized THz wave to any desired direction with nearly perfect conversion efficiency. The device performance has been experimentally demonstrated by both THz transmission spectra and direct imaging. The polarization rotation originates from multi wave interference in the three-layer grating structure based on the scattering-matrix analysis. We can expect that this active broadband polarization rotator has wide applications in analytical chemistry, biology, communication technology, imaging, etc.. Reference: R. H. Fan, Y. Zhou, X. P. Ren, R. W. Peng, S. C. Jiang, D. H. Xu, X. Xiong, X. R. Huang, and Mu Wang, Advanced Materials 27,1201(2015). Freely-tunable broadband polarization rotator for terahertz waves.

  13. Quantum cascade lasers operating from 1.4 to 4 THz

    Institute of Scientific and Technical Information of China (English)

    Sushil Kumar

    2011-01-01

    The development of teranertz (THz) quantum cascade lasers (QCLs) has progressed considerably since their advent almost a decade ago. THz QCLs operating in a frequency range from 1.4 to 4 THz with electron-phonon scattering mediated depopulation schemes are described. Several different types of GaAs/AlGaAs superlattice designs are reviewed. Some of the best temperature performances are obtained by the so-called resonant-phonon designs that are described. Operation above a temperature of 160 K has been obtained across the spectrum for THz QCLs operating at v > 1.8 THz. The maximum operating temperature of previously reported THz QCLs has empirically been limited to a value of ~ hω/kB- A new design scheme for THz QCLs with scattering-assisted injection is shown to surpass this empirical temperature barrier, and is promising to improve the maximum operating temperatures of THz QCLs even further.%1.IntroductionHigh-power sources of terahertz (THz) radiation are required for a multitude of applications in sensing,imaging,and spectroscopy in fields as diverse as astronomy,medicine,security,pharmaceuticals and so-forth.THz science and technology has advanced significantly in the recent years[1,2] especially toward the realization of novel THz radiation sources.In comparison to narrow-band sources such as lasers,broadband sources of terahertz radiation are more widely available;however,such sources are inherently low power (average power is of the order of few micro-Watts).They are useful nevertheless because of room temperature operation and for their ability to be detected coherently.Techniques such as generation of THz bandwidth time-domain pulses in high resistivity semiconductors[3],non-linear generation by electrooptical-rectification in crystals such as ZnTe[4],or nonlinear generation by optical parametric conversion in materials such as LiNbO3[5] or by difference-frequency generation in semiconductors[6],have been used for various raster-scanned imaging and

  14. First supra-THz Heterodyne Array Receivers for Astronomy with the SOFIA Observatory

    CERN Document Server

    Risacher, Christophe; Stutzki, Juergen; Huebers, Heinz-Wilhelm; Buechel, Denis; Graf, Urs U; Heyminck, Stefan; Honingh, Cornelia E; Jacobs, Karl; Klein, Bernd; Klein, Thomas; Leinz, Christian; Puetz, Patrick; Reyes, Nicolas; Ricken, Oliver; Wunsch, Hans-Joachim; Fusco, Paul; Rosner, Stefan

    2015-01-01

    We present the upGREAT THz heterodyne arrays for far-infrared astronomy. The Low Frequency Array (LFA) is designed to cover the 1.9-2.5 THz range using 2x7-pixel waveguide-based HEB mixer arrays in a dual polarization configuration. The High Frequency Array (HFA) will perform observations of the [OI] line at ~4.745 THz using a 7-pixel waveguide-based HEB mixer array. This paper describes the common design for both arrays, cooled to 4.5 K using closed- cycle pulse tube technology. We then show the laboratory and telescope characterization of the first array with its 14 pixels (LFA), which culminated in the successful commissioning in May 2015 aboard the SOFIA airborne observatory observing the [CII] fine structure transition at 1.905 THz. This is the first successful demonstration of astronomical observations with a heterodyne focal plane array above 1 THz and is also the first time high- power closed-cycle coolers for temperatures below 4.5 K are operated on an airborne platform.

  15. Industrial applications of THz systems

    Science.gov (United States)

    Wietzke, S.; Jansen, C.; Jördens, C.; Krumbholz, N.; Vieweg, N.; Scheller, M.; Shakfa, M. K.; Romeike, D.; Hochrein, T.; Mikulics, M.; Koch, M.

    2009-07-01

    Terahertz time-domain spectroscopy (THz TDS) holds high potential as a non-destructive, non-contact testing tool. We have identified a plethora of emerging industrial applications such as quality control of industrial processes and products in the plastics industry. Polymers are transparent to THz waves while additives show a significantly higher permittivity. This dielectric contrast allows for detecting the additive concentration and the degree of dispersion. We present a first inline configuration of a THz TDS spectrometer for monitoring polymeric compounding processes. To evaluate plastic components, non-destructive testing is strongly recommended. For instance, THz imaging is capable of inspecting plastic weld joints or revealing the orientation of fiber reinforcements. Water strongly absorbs THz radiation. However, this sensitivity to water can be employed in order to investigate the moisture absorption in plastics and the water content in plants. Furthermore, applications in food technology are discussed. Moreover, security scanning applications are addressed in terms of identifying liquid explosives. We present the vision and first components of a handheld security scanner. In addition, a new approach for parameter extraction of THz TDS data is presented. All in all, we give an overview how industry can benefit from THz TDS completing the tool box of non-destructive evaluation.

  16. UV-LIGA microfabrication process for sub-terahertz waveguides utilizing multiple layered SU-8 photoresist

    Science.gov (United States)

    Malekabadi, Ali; Paoloni, Claudio

    2016-09-01

    A microfabrication process based on UV LIGA (German acronym of lithography, electroplating and molding) is proposed for the fabrication of relatively high aspect ratio sub-terahertz (100–1000 GHz) metal waveguides, to be used as a slow wave structure in sub-THz vacuum electron devices. The high accuracy and tight tolerances required to properly support frequencies in the sub-THz range can be only achieved by a stable process with full parameter control. The proposed process, based on SU-8 photoresist, has been developed to satisfy high planar surface requirements for metal sub-THz waveguides. It will be demonstrated that, for a given thickness, it is more effective to stack a number of layers of SU-8 with lower thickness rather than using a single thick layer obtained at lower spin rate. The multiple layer approach provides the planarity and the surface quality required for electroforming of ground planes or assembly surfaces and for assuring low ohmic losses of waveguides. A systematic procedure is provided to calculate soft and post-bake times to produce high homogeneity SU-8 multiple layer coating as a mold for very high quality metal waveguides. A double corrugated waveguide designed for 0.3 THz operating frequency, to be used in vacuum electronic devices, was fabricated as test structure. The proposed process based on UV LIGA will enable low cost production of high accuracy sub-THz 3D waveguides. This is fundamental for producing a new generation of affordable sub-THz vacuum electron devices, to fill the technological gap that still prevents a wide diffusion of numerous applications based on THz radiation.

  17. UV-LIGA microfabrication process for sub-terahertz waveguides utilizing multiple layered SU-8 photoresist

    Science.gov (United States)

    Malekabadi, Ali; Paoloni, Claudio

    2016-09-01

    A microfabrication process based on UV LIGA (German acronym of lithography, electroplating and molding) is proposed for the fabrication of relatively high aspect ratio sub-terahertz (100-1000 GHz) metal waveguides, to be used as a slow wave structure in sub-THz vacuum electron devices. The high accuracy and tight tolerances required to properly support frequencies in the sub-THz range can be only achieved by a stable process with full parameter control. The proposed process, based on SU-8 photoresist, has been developed to satisfy high planar surface requirements for metal sub-THz waveguides. It will be demonstrated that, for a given thickness, it is more effective to stack a number of layers of SU-8 with lower thickness rather than using a single thick layer obtained at lower spin rate. The multiple layer approach provides the planarity and the surface quality required for electroforming of ground planes or assembly surfaces and for assuring low ohmic losses of waveguides. A systematic procedure is provided to calculate soft and post-bake times to produce high homogeneity SU-8 multiple layer coating as a mold for very high quality metal waveguides. A double corrugated waveguide designed for 0.3 THz operating frequency, to be used in vacuum electronic devices, was fabricated as test structure. The proposed process based on UV LIGA will enable low cost production of high accuracy sub-THz 3D waveguides. This is fundamental for producing a new generation of affordable sub-THz vacuum electron devices, to fill the technological gap that still prevents a wide diffusion of numerous applications based on THz radiation.

  18. Terahertz field enhancement to the MV/cm regime in a tapered parallel plate waveguide

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Andryieuski, Andrei; Lavrinenko, Andrei;

    2012-01-01

    We investigate field enhancement properties of a tapered parallel plate waveguide for ultrashort terahertz (THz) pulses. We use two independent methods, air biased coherent detection inside the waveguide and free-space electro-optic sampling, respectively, which enables a calibrated, quantitative...

  19. 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 anywhere...... in the sample at any orientation using optical traps. One of the key aspects to the work is the change in direction of the incident plane wave, and the marked increase in the numerical aperture demonstrated. Hence, the optically steered waveguide can tap from a relatively broader beam and then...... generate a more tightly confined light at its tip. The paper contains both simulation, related to the propagation of light through the waveguide, and experimental demonstrations using our BioPhotonics Workstation. In a broader context, this work shows that optically trapped microfabricated structures can...

  20. Sapphire decelerating capillary channel integrated with antenna at frequency 0.675 THz

    Science.gov (United States)

    Ashanin, I. A.; Polozov, S. M.

    2016-07-01

    In recent years, there has been an increasing interest in THz-radiation for application in medicine (THz tomographs), in pharmaceutics (composition analysis for medicines), in introscopy of large-scale objects (ships, trains, containers) and others. THz-radiation can be generated by relativistic electron bunches passing through the Cherenkov decelerating capillary channel (circular waveguide with dielectric filling) with horn extraction. Relativistic electron beams having ∼100 µm in diameter and pulse durations of 1 ps or less (as in photoinjectors) are capable of producing substantial power of THz-radiation. High-peak power coherent Cherenkov radiation can be produced by a properly modulated high-brightness electron beam or by a single, high-density bunch having sub-wavelength dimension. The aperture of a Cherenkov decelerating structure should be comparable with the mm or sub-mm wavelength (0.1-3 mm). Different dielectric materials for the internal surface coating of the capillary channel of mm-sub-mm cross-section can be used. As is known, a frequency of 0.675 THz corresponds to the atmospheric window with high transparency. This report presents the results of electrodynamics study of the metallized sapphire decelerating Cherenkov capillary. A horn antenna attached to the metallized sapphire capillary channel at the 0.675 THz resonant frequency will be considered.

  1. 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...... quantum-dot-waveguide coupling. Such a structure is ideally suited for a number of applications in quantum information processing and among others we propose an on-chip spin-photon interface, a single photon transistor, and a deterministic cNOT gate....

  2. Time-resolved terahertz spectroscopy in a parallel-plate waveguide

    DEFF Research Database (Denmark)

    Cooke, David; Jepsen, Peter Uhd

    2009-01-01

    The parallel plate waveguide (PPWG), formed by two conducting parallel plates separated by a distance on the order of the wavelength of the propagating light, has shown itself to be a near ideal terahertz interconnect exhibiting low loss and dispersionless propagation.[1] It is also a useful tool...... for enhancing the interaction of THz radiation with thin lms to the point where spectroscopy on 20 nm-thick layers of water have been performed.[2] A natural extension ofthis technique is to examine photoexcited samples inside the waveguide, with the addition of a second femtosecond excitation pulse. Here we...... demonstrate such a technique for time-resolved optical pump-THz probe measurements of materials embedded within a parallel plate waveguide. This is made possible by replacing one of the plates with a transparent conducting oxide, which provides sufcient electrical conductivity to guide the THz pulse, yet...

  3. Electrical Control of Broadband Terahertz Wave Transmission with Two-Terminal Graphene Oxide Devices

    CERN Document Server

    Lee, Seungwoo; Lee, Won Jun; Park, Byung Cheol; Kang, Byungsoo; Hwang, Euyheon; Kim, Sang Ouk

    2015-01-01

    Carbon nanomaterials such as carbon nanotubes and graphene have proved to be efficient building blocks for active optoelectronic devices. Especially, the exotic properties of crystalline graphene, such as a linear/gapless energy dispersion, offer a generic route to the development of active photonic modulator at the infrared (IR) and terahertz (THz) regime with large modulation depth. Here, we show that graphene oxide (GO), an oxygenated derivative of graphene with randomly distributed molecular defects (e.g., adsorbed water molecules and punched holes), can provide a different way to effectively control broadband THz transmission amplitude, when incorporated into two-terminal electrode devices. Electrically trapped charge carriers within localized impurity states (LIS) of GO, which originate from fully randomized defective structure of GO, results in a large modulation of transmission amplitude (~30%) for broadband THz waves (0.3 ~ 2.0 THz) even at room temperature. Interesting hysteretic behavior observed i...

  4. Structure Design of Polymer Electro-Optic Modulator with Ultra- Broadband

    Institute of Scientific and Technical Information of China (English)

    Haibo Peng; Boyu Wu; Qiong Song; Fei Lu; Shuyun Luo

    2003-01-01

    Using finite element method, lots of calculating focusing on polymer electro-optic modulators with ultra-broadband were done, a few structures were analyzed. Coplanar waveguide electrode system was advanced, a few real examples was given.

  5. 宽带印刷天线与双极化微带及波导缝隙天线阵%Broadband printed antennas and dual-polarized microstrip and waveguide slot antenna arrays

    Institute of Scientific and Technical Information of China (English)

    汪伟

    2006-01-01

    @@ In order to meet the urgent needs in wireless communications, microwave image synthetic aperture radars (SAR), and electronic warfare systems, this dissertation studies several types of broadband dual-polarized planar antenna elements and arrays, and proposes a few of novel designs with experimental verification.The main accomplishments reported in the dissertation are as follows.

  6. Generation of broadband spontaneous parametric fluorescence using multiple bulk nonlinear crystals

    OpenAIRE

    Okano, Masayuki; Okamoto, Ryo; TANAKA, Akira; Subashchandran, Shanthi; Takeuchi, Shigeki

    2012-01-01

    We propose a novel method for generating broadband spontaneous parametric fluorescence by using a set of bulk nonlinear crystals (NLCs). We also demonstrate this scheme experimentally. Our method employs a superposition of spontaneous parametric fluorescence spectra generated using multiple bulk NLCs. A typical bandwidth of 160 nm (73 THz) with a degenerate wavelength of 808 nm was achieved using two beta-barium-borate (BBO) crystals, whereas a typical bandwidth of 75 nm (34 THz) was realized...

  7. Frequency Comb Assisted Broadband Precision Spectroscopy with Cascaded Diode Lasers

    CERN Document Server

    Liu, Junqiu; Pfeiffer, Martin H P; Kordts, Arne; Kamel, Ayman N; Guo, Hairun; Geiselmann, Michael; Kippenberg, Tobias J

    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 extending the measurement bandwidth to 37.4 THz (1355 to 1630 nm) at MHz 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 to characterize the dispersion of integrated microresonators up to the fourth order.

  8. Monolithic, Widely Tunable, THz Local Oscillator Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal describes development of a new type of quantum-cascade laser for use as a local oscillator at frequencies above 2 THz. The THz source described is a...

  9. 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.

  10. Broadband terahertz radiation from a biased two-dimensional electron gas in an AlGaN/GaN heterostructure

    International Nuclear Information System (INIS)

    The broadband terahertz (THz) emission from drifting two-dimensional electron gas (2DEG) in an AlGaN/GaN heterostructure at 6 K is reported. The devices are designed as THz plasmon emitters according to the Smith-Purcell effect and the ‘shallow water’ plasma instability mechanism in 2DEG. Plasmon excitation is excluded since no signature of electron-density dependent plasmon mode is observed. Instead, the observed THz emission is found to come from the heated lattice and/or the hot electrons. Simulated emission spectra of hot electrons taking into account the THz absorption in air and Fabry-Pérot interference agree well with the experiment. It is confirmed that a blackbody-like THz emission will inevitably be encountered in similar devices driven by a strong in-plane electric field. A conclusion is drawn that a more elaborate device design is required to achieve efficient plasmon excitation and THz emission. (paper)

  11. An Industrial THz Killer Application?

    CERN Document Server

    van Mechelen, Dook

    2015-01-01

    Terahertz technology is mature enough for large-volume sensing applications. However, Dook van Mechelen says there are a few hurdles preventing its industrial debut. THz spectroscopy has a number of advantages that point to abundant industrial applications, in areas such quality control, security and biomedical imaging. Yet despite those advantages, the search for a THz "killer application"--a novel, innovative use with a business case strong enough to bring the technology into the industrial mainstream--has remained fruitless, and even the hope of finding such an application has begun to falter. Why has a killer app for THz radiation been so elusive? And how can the road to industrial application of this versatile technology be cleared?

  12. 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....

  13. Image magnification in transformation optics devices based on tapered waveguides

    Science.gov (United States)

    Zimmerman, William; Jensen, Christopher; Smolyaninova, Vera; Smolyaninov, Igor

    Recent progress in metamaterial and transformation optics (TO) research gave rise to such fascinating devices as perfect lenses, invisibility cloaks, and numerous other unusual electromagnetic devices. However, the metamaterials have problems with low-loss broadband performance and complexity of fabrication, especially in the visible frequency range. Our TO devices allow us to circumvent these difficulties by using lithographically defined metal/dielectric waveguides to emulate metamaterial properties. Adiabatic variations of the waveguide shape enable control of the effective refractive index experienced by light propagating inside the waveguide. The achieved image magnification is consistent with numerical simulations. We have studied wavelength and polarization dependent performance of the waveguides. Our experimental designs appear to be broadband, which has been verified in the 480-633 nm range. These novel optical devices considerably extend our ability to control light on sub-micrometer scales. This research was supported by the NSF Grant DMR-1104676.

  14. A symmetric terahertz graphene-based hybrid plasmonic waveguide

    Science.gov (United States)

    Chen, Ming; Sheng, Pengchi; Sun, Wei; Cai, Jianjin

    2016-10-01

    A graphene-based hybrid plasmonic waveguide (GHPW) structure, which works on the terahertz frequency and includes two identical cylinder robs symmetrically put on each side of graphene sheet with gaps g, has been proposed and investigated. The present waveguide not only significantly improves the propagation length but also maintains a compact mode area, which is due to the coupling between the dielectric waveguide mode and plasmonic mode. The graphene plasmons particularly differ from plasmons in noble metals of which propagation loss can be tuned by adjusting the Fermi energy level or carrier mobility. With a very good Fermi energy level and carrier mobility, a typical propagation length of 26.7 mm, and mode area of optical field of approximately 4 μm2 at 10 THz are achieved. This waveguide structure shows great promise for designing kinds of functional elements in actively tunable integrated optical devices.

  15. 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....

  16. A broadband multifocal metalens in the terahertz frequency range

    Science.gov (United States)

    Hashemi, Mahdieh; Moazami, Amin; Naserpour, Mahin; Zapata-Rodríguez, Carlos J.

    2016-07-01

    Metasurfaces, the 2D form of metamaterials with their ability in phase, amplitude and polarization manipulation are widely used in designing optical devices. Efforts to find proper photonic components in the terahertz (THz) range of frequency lead us to adopt metasurfaces as their constituent elements. Here, we conceived a broadband THz lens with an adjustable number and arrangement of focal points. To have a full control over the lens functionality, we used a metasurface with the capability of simultaneously modulating the amplitude and phase of the incident wave. C-shaped ring resonators (CSRRs) with different geometry and orientation capable of simultaneously manipulating phase and amplitude of the scattered fields, are proper choice to design the lens. We show that the introduced lens in a one-dimensional layout has a wide range of working frequencies within the THz spectrum, which can be used in a plethora of applications.

  17. 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

  18. Broadband absorption engineering of hyperbolic metafilm patterns

    Science.gov (United States)

    Ji, Dengxin; Song, Haomin; Zeng, Xie; Hu, Haifeng; Liu, Kai; Zhang, Nan; Gan, Qiaoqiang

    2014-03-01

    Perfect absorbers are important optical/thermal components required by a variety of applications, including photon/thermal-harvesting, thermal energy recycling, and vacuum heat liberation. While there is great interest in achieving highly absorptive materials exhibiting large broadband absorption using optically thick, micro-structured materials, it is still challenging to realize ultra-compact subwavelength absorber for on-chip optical/thermal energy applications. Here we report the experimental realization of an on-chip broadband super absorber structure based on hyperbolic metamaterial waveguide taper array with strong and tunable absorption profile from near-infrared to mid-infrared spectral region. The ability to efficiently produce broadband, highly confined and localized optical fields on a chip is expected to create new regimes of optical/thermal physics, which holds promise for impacting a broad range of energy technologies ranging from photovoltaics, to thin-film thermal absorbers/emitters, to optical-chemical energy harvesting.

  19. Eutectic epsilon-near-zero metamaterial terahertz waveguides

    OpenAIRE

    Acosta, M. F.; Merino, R. I.; Orera, V.M.; Tzortzakis, S.

    2013-01-01

    We present and analyze the unique phenomena of enhanced THz transmission through a subwavelength LiF dielectric rod lattice embedded in an epsilon-near-zero KCl host. Our experimental results in combination with theoretical calculations show that subwavelength waveguiding of terahertz radiation is achieved within an alkali-halide eutectic metamaterial as result of the coupling of Mie-resonance modes arising in the dielectric lattice. © 2013 Optical Society of America.

  20. Amplifier based broadband pixel for sub-millimeter wave imaging

    Science.gov (United States)

    Sarkozy, Stephen; Drewes, Jonathan; Leong, Kevin M. K. H.; Lai, Richard; Mei, X. B. (Gerry); Yoshida, Wayne; Lange, Michael D.; Lee, Jane; Deal, William R.

    2012-09-01

    Broadband sub-millimeter wave technology has received significant attention for potential applications in security, medical, and military imaging. Despite theoretical advantages of reduced size, weight, and power compared to current millimeter wave systems, sub-millimeter wave systems have been hampered by a fundamental lack of amplification with sufficient gain and noise figure properties. We report a broadband pixel operating from 300 to 340 GHz, biased off a single 2 V power supply. Over this frequency range, the amplifiers provide > 40 dB gain and 1.0 THz. The first sub-millimeter wave-based images using active amplification are demonstrated as part of the Joint Improvised Explosive Device Defeat Organization Longe Range Personnel Imager Program. This development and demonstration may bring to life future sub-millimeter-wave and THz applications such as solutions to brownout problems, ultra-high bandwidth satellite communication cross-links, and future planetary exploration missions.

  1. Spatial-temporal dynamics of broadband terahertz Bessel beam propagation

    Science.gov (United States)

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

    2016-08-01

    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.

  2. 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.

  3. 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.

  4. Polymers in Waveguide Packaging

    Institute of Scientific and Technical Information of China (English)

    G; Z.; Xiao; C.; P.; Grover

    2003-01-01

    Polymers were successfully used in the packaging of waveguide-based photonic components in the area of fiber-to-waveguide coupling, waveguide die attachment, strain relief, and waveguide encapsulation. The application results of these polymers were described in this paper.

  5. Photo-generated THz antennas

    Science.gov (United States)

    Georgiou, G.; Tyagi, H. K.; Mulder, P.; Bauhuis, G. J.; Schermer, J. J.; Rivas, J. Gómez

    2014-01-01

    Electromagnetic resonances in conducting structures give rise to the enhancement of local fields and extinction efficiencies. Conducting structures are conventionally fabricated with a fixed geometry that determines their resonant response. Here, we challenge this conventional approach by demonstrating the photo-generation of THz linear antennas on a flat semiconductor layer by the structured optical illumination through a spatial light modulator. Free charge carriers are photo-excited only on selected areas, which enables the realization of different conducting antennas on the same sample by simply changing the illumination pattern, thus without the need of physically structuring the sample. These results open a wide range of possibilities for the all-optical spatial control of resonances on surfaces and the concomitant control of THz extinction and local fields.

  6. Observing electron spin resonance between 0.1 and 67 GHz at temperatures between 50 mK and 300 K using broadband metallic coplanar waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Wiemann, Yvonne; Simmendinger, Julian; Clauss, Conrad; Bogani, Lapo; Dressel, Martin; Scheffler, Marc [1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart (Germany); Bothner, Daniel; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Collective Quantum Phenomena in LISA+, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen (Germany)

    2015-05-11

    We describe a fully broadband approach for electron spin resonance (ESR) experiments, where it is possible to tune not only the magnetic field but also the frequency continuously over wide ranges. Here, a metallic coplanar transmission line acts as compact and versatile microwave probe that can easily be implemented in different cryogenic setups. We perform ESR measurements at frequencies between 0.1 and 67 GHz and at temperatures between 50 mK and room temperature. Three different types of samples (Cr{sup 3+} ions in ruby, organic radicals of the nitronyl-nitroxide family, and the doped semiconductor Si:P) represent different possible fields of application for the technique. We demonstrate that an extremely large phase space in temperature, magnetic field, and frequency for ESR measurements, substantially exceeding the range of conventional ESR setups, is accessible with metallic coplanar lines.

  7. Bright 30 THz Impulsive Solar Bursts

    CERN Document Server

    Kaufmann, P; Marcon, R; Kudaka, A S; Cabezas, D P; Cassiano, M M; Francile, C; Fernandes, L O T; Ramirez, R F Hidalgo; Luoni, M; Marun, A; Pereyra, P; de Souza, R V

    2015-01-01

    Impulsive 30 THz continuum bursts have been recently observed in solar flares, utilizing small telescopes with a unique and relatively simple optical setup concept. The most intense burst was observed together with a GOES X2 class event on October 27, 2014, also detected at two sub-THz frequencies, RHESSI X-rays and SDO/HMI and EUV. It exhibits strikingly good correlation in time and in space with white light flare emission. It is likely that this association may prove to be very common. All three 30 THz events recently observed exhibited intense fluxes in the range of 104 solar flux units, considerably larger than those measured for the same events at microwave and sub-mm wavelengths. The 30 THz burst emission might be part of the same spectral burst component found at sub-THz frequencies. The 30 THz solar bursts open a promising new window for the study of flares at their origin

  8. Integration of a terahertz quantum cascade laser with a hollow waveguide

    Science.gov (United States)

    Wanke, Michael C.; Nordquist, Christopher D.

    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.

  9. 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.

  10. Broad spectral range synchronized flat-top arrayed waveguide grating

    NARCIS (Netherlands)

    Akca, B. Imran; Doerr, Christopher R.; Pollnau, Markus; Ridder, de René M.

    2012-01-01

    A broad-band Mach-Zehnder-interferometer-synchronized flat-top arrayed waveguide grating is presented with a 0.5-dB bandwidth of 12 nm over 90 nm of spectral range and a central excess loss value of -0.5 dB.

  11. Terahertz field imaging inside tapered parallel plate waveguides

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Andryieuski, Andrei; Lavrinenko, Andrei;

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

  12. Quantum waveguides

    CERN Document Server

    Exner, Pavel

    2015-01-01

    This monograph explains the theory of quantum waveguides, that is, dynamics of quantum particles confined to regions in the form of tubes, layers, networks, etc. The focus is on relations between the confinement geometry on the one hand and the spectral and scattering properties of the corresponding quantum Hamiltonians on the other. Perturbations of such operators, in particular, by external fields are also considered. The volume provides a unique summary of twenty five years of research activity in this area and indicates ways in which the theory can develop further. The book is fairly self-contained. While it requires some broader mathematical physics background, all the basic concepts are properly explained and proofs of most theorems are given in detail, so there is no need for additional sources. Without a parallel in the literature, the monograph by Exner and Kovarik guides the reader through this new and exciting field.

  13. Inherent resistivity of graphene to strong THz fields

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Mics, Zoltán; Jensen, Søren;

    2014-01-01

    The nonlinear THz conductivity of graphene is characterized using nonlinear ultrafast THz spectroscopy. Efficient carrier heating by the THz field reduces carrier scattering, yet, counter-intuitively, simultaneously suppresses the high-frequency conductivity of graphene. © 2014 OSA....

  14. Foundry-compatible SOI waveguides with a graphene top layer for wideband wavelength conversion

    Science.gov (United States)

    Vermeulen, N.; Cheng, J. L.; Sipe, J. E.; Thienpont, H.

    2016-05-01

    The tremendous progress in the fabrication of highly confining silicon-on-insulator (SOI) waveguides has been very beneficial for four-wave-mixing (FWM)-based wavelength conversion applications. Nevertheless, to establish power-efficient and wideband FWM wavelength conversion, one typically requires long (cm-scale) SOI waveguides with dispersion-engineered cross-sections that do not comply with the fabrication constraints of multiproject- wafer-oriented silicon photonics foundries. In this paper, we numerically examine the opportunities for wideband wavelength conversion through FWM in a foundry-compatible SOI waveguide covered with the highly nonlinear two-dimensional material of graphene. When combining subwatt level pump powers with a short waveguide length of only a few hundreds of microns, perfectly phase-matched conversion with significant efficiencies close to 20 dB can be obtained over a more than 40 THz-wide signal band adjacent to the pump frequency. Because of the tunability of the graphene properties, it is also possible to obtain quasi-phase matched FWM conversion through a periodic sign reversal of the graphene third-order nonlinearity along the waveguide. Conversion efficiencies exceeding 30 dB can be achieved over a 3.4 THz-wide signal band that is situated as much as 58 THz away from the pump frequency. Finally, the graphene tunability also allows for switching between the perfectly phase-matched and quasi-phase-matched operation modes.

  15. THz Electro-absorption Effect in Quantum Dots

    DEFF Research Database (Denmark)

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

    2011-01-01

    Instantaneous electro-absorption effect in quantum dots, induced by electric field of THz pulse with 3 THz bandwidth is demonstrated in THz pump - optical probe experiment. This effect may be promising for Tbit/s wireless transmission systems.......Instantaneous electro-absorption effect in quantum dots, induced by electric field of THz pulse with 3 THz bandwidth is demonstrated in THz pump - optical probe experiment. This effect may be promising for Tbit/s wireless transmission systems....

  16. Compact waveguide circular polarizer

    Energy Technology Data Exchange (ETDEWEB)

    Tantawi, Sami G.

    2016-08-16

    A multi-port waveguide is provided having a rectangular waveguide that includes a Y-shape structure with first top arm having a first rectangular waveguide port, a second top arm with second rectangular waveguide port, and a base arm with a third rectangular waveguide port for supporting a TE.sub.10 mode and a TE.sub.20 mode, where the end of the third rectangular waveguide port includes rounded edges that are parallel to a z-axis of the waveguide, a circular waveguide having a circular waveguide port for supporting a left hand and a right hand circular polarization TE.sub.11 mode and is coupled to a base arm broad wall, and a matching feature disposed on the base arm broad wall opposite of the circular waveguide for terminating the third rectangular waveguide port, where the first rectangular waveguide port, the second rectangular waveguide port and the circular waveguide port are capable of supporting 4-modes of operation.

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

    Directory of Open Access Journals (Sweden)

    Assim Boukhayma

    2016-03-01

    Full Text Available 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 . 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.

  18. 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) 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. PMID:26950131

  19. 具备阻抗和低副瓣宽带特性的脊波导缝隙阵列天线设计%Design of a Slotted Ridge Waveguide Antenna Array with Broadband Characteristic of Impedance and Low Sidelobe

    Institute of Scientific and Technical Information of China (English)

    李佳美; 官正涛

    2014-01-01

    设计了一种16×8脊波导缝隙阵列天线,线阵阵面分成两个子阵,馈电采用同轴馈电与耦合缝隙馈电结合的两级馈电方式,辐射缝隙分布为泰勒分布。天线设计采用近场诊断方法和阻抗过载技术进行优化。天线实物加工测试结果表明,天线在X频段驻波带宽(VSWR≤1.5)为7.3%,最低副瓣达到-25.8 dB,副瓣电平带宽(SLL≤-19 dB)为6.2%。与已有文献相比,该天线同时具备阻抗宽带特性和低副瓣宽带特性,工作频带内具有增益均大于16 dBi的高增益特性。%An 8í16 slotted ridge waveguide antenna array is presented. The linear array is separated into two sub-arrays. The antenna is fed by a waveguide divider,which is combined by a coaxial connector and two coupling slots. All the radiation slots are distributed in Taylor pattern. The antenna array is optimized according to the near-field on slots aperture and impedance overload technology. The antenna entity is fab-ricated and measured. Measured results show that impedance bandwidth is 7. 3%(VSWR≤1. 5),and side-lobe bandwidth(SLL≤-19 dB) is 6. 2%,sidelobe is less than-25. 8 dB. The conclusion is drawn that the antenna possesses broadband characteristic of impedance as well as low sidelobe compared with those pres-ented in existing literatures. Besides,the gains are higher than 16 dBi within its operating frequency.

  20. Highly tunable Terahertz filter with magneto-optical Bragg grating formed in semiconductor-insulator-semiconductor waveguides

    OpenAIRE

    Kangwen Li; Xunpeng Ma; Zuyin Zhang; Lina Wang; Haifeng Hu; Yun Xu; Guofeng Song

    2013-01-01

    A highly tunable terahertz (THz) filter with magneto-optical Bragg grating formed in semiconductor-insulator-semiconductor waveguides is proposed and demonstrated numerically by means of the Finite Element Method. The results reveal that a sharp peak with high Q-value presents in the band gap of Bragg grating waveguide with a defect, and the position of the sharp peak can be modified greatly by changing the intensity of the transverse magnetic field applied to the device. Compared to the situ...

  1. THz therapy and smoking: facts and hypotheses

    Directory of Open Access Journals (Sweden)

    Svetlana S. Parshina

    2013-11-01

    Full Text Available There had been studied an antianginal effect and hemodynamic effects of THz electromagnetic waves of molecular NO spectrum (150.176 ... 150.664 GHz in 19 smokers and 18 non-smokers patients with angina. It had been fixed that antianginal, pulse slowing and antihypertensive effects of THz waves in both groups did not differ.

  2. 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.

  3. Monitoring leaf water content with THz and sub-THz waves.

    Science.gov (United States)

    Gente, Ralf; Koch, Martin

    2015-01-01

    Terahertz technology is still an evolving research field that attracts scientists with very different backgrounds working on a wide range of subjects. In the past two decades, it has been demonstrated that terahertz technology can provide a non-invasive tool for measuring and monitoring the water content of leaves and plants. In this paper we intend to review the different possibilities to perform in-vivo water status measurements on plants with the help of THz and sub-THz waves. The common basis of the different methods is the strong absorption of THz and sub-THz waves by liquid water. In contrast to simpler, yet destructive, methods THz and sub-THz waves allow for the continuous monitoring of plant water status over several days on the same sample. The technologies, which we take into focus, are THz time domain spectroscopy, THz continuous wave setups, THz quasi time domain spectroscopy and sub-THz continuous wave setups. These methods differ with respect to the generation and detection schemes, the covered frequency range, the processing and evaluation of the experimental data, and the mechanical handling of the measurements. Consequently, we explain which method fits best in which situation. Finally, we discuss recent and future technological developments towards more compact and budget-priced measurement systems for use in the field. PMID:25767560

  4. THz semiconductor-based front-end receiver technology for space applications

    Science.gov (United States)

    Mehdi, Imran; Siegel, Peter

    2004-01-01

    Advances in the design and fabrication of very low capacitance planar Schottky diodes and millimeter-wave power amplifiers, more accurate device and circuit models for commercial 3-D electromagnetic simulators, and the availability of both MEMS and high precision metal machining, have enabled RF engineers to extend traditional waveguide-based sensor and source technologies well into the TI-Iz frequency regime. This short paper will highlight recent progress in realizing THz space-qualified receiver front-ends based on room temperature semiconductor devices.

  5. Self-consistent modeling of terahertz waveguide and cavity with frequency-dependent conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Y. J.; Chu, K. R., E-mail: krchu@yahoo.com.tw [Department of Physics, National Taiwan University, Taipei, Taiwan (China); Thumm, M. [IHM and IHE, Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2015-01-15

    The surface resistance of metals, and hence the Ohmic dissipation per unit area, scales with the square root of the frequency of an incident electromagnetic wave. As is well recognized, this can lead to excessive wall losses at terahertz (THz) frequencies. On the other hand, high-frequency oscillatory motion of conduction electrons tends to mitigate the collisional damping. As a result, the classical theory predicts that metals behave more like a transparent medium at frequencies above the ultraviolet. Such a behavior difference is inherent in the AC conductivity, a frequency-dependent complex quantity commonly used to treat electromagnetics of metals at optical frequencies. The THz region falls in the gap between microwave and optical frequencies. However, metals are still commonly modeled by the DC conductivity in currently active vacuum electronics research aimed at the development of high-power THz sources (notably the gyrotron), although a small reduction of the DC conductivity due to surface roughness is sometimes included. In this study, we present a self-consistent modeling of the gyrotron interaction structures (a metallic waveguide or cavity) with the AC conductivity. The resulting waveguide attenuation constants and cavity quality factors are compared with those of the DC-conductivity model. The reduction in Ohmic losses under the AC-conductivity model is shown to be increasingly significant as the frequency reaches deeper into the THz region. Such effects are of considerable importance to THz gyrotrons for which the minimization of Ohmic losses constitutes a major design consideration.

  6. Towards Ultrahigh Speed Impulse Radio THz Wireless Communications

    DEFF Research Database (Denmark)

    Yu, Xianbin; Galili, Michael; Morioka, Toshio;

    2015-01-01

    evaluate the realistic throughput and accessible wireless range of a THz impulse radio communication link based on a uni-travelling photodiode (UTC-PD) as THz emitter and a photoconductive antenna (PCA) as THz receiver. The impact of highly frequency-selective THz channel and the noise in the system...

  7. Kinetic inductance driven nanoscale 2D and 3D THz transmission lines

    CERN Document Server

    Mousavi, S Hossein; Wang, Zheng

    2015-01-01

    We examine the unusual dispersion and attenuation of transverse electromagnetic waves in the few-THz regime on nanoscale graphene and copper transmission lines. Conventionally, such propagation has been considered to be highly dispersive, due to the RC-constant-driven voltage diffusion below 1THz and plasmonic effects at higher frequencies. Our numerical modelling between the microwave and optical regimes reveals that conductor kinetic inductance creates an ultra-broadband LC region. This resultant frequency-independent attenuation is an ideal characteristic that is known to be non-existent in macro-scale transmission lines. The kinetic-LC frequency range is dictated by the structural dimensionality and the free-carrier scattering rate of the conductor material. Moreover, up to 40x wavelength reduction is observed in graphene transmission lines.

  8. THz waves: biological effects, industrial and medical

    International Nuclear Information System (INIS)

    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.)

  9. Subwavelength THz imaging of graphene photoconductivity

    CERN Document Server

    Hornett, Samuel M; Vardaki, Martha Z; Beckerleg, Chris; Hendry, Euan

    2016-01-01

    Using a spatially structured, optical pump pulse with a THz probe pulse, we are able to determine spatial variations of the ultrafast THz photoconductivity with sub-wavelength resolution (75 $\\mu m \\approx \\lambda/5$ at 0.8 THz) in a planar graphene sample. We compare our results to Raman spectroscopy and correlate the existence of the spatial inhomogeneities between the two measurements. We find a strong correlation with inhomogeneity in electron density. This demonstrates the importance of eliminating inhomogeneities in doping density during CVD growth and fabrication for photoconductive devices.

  10. Resonant-tunnelling diodes for THz applications

    Science.gov (United States)

    Feiginov, Michael; Sydlo, Cezary; Cojocari, Oleg; Meissner, Peter

    2012-10-01

    We investigate experimentally resonant-tunnelling-diode (RTD) oscillators, which are based on RTDs with heavily doped collector. We demonstrate that such RTD oscillators can work at frequencies, which are far beyond the limitations imposed by resonant-state lifetime and relaxation time. Exploiting further such RTDs, we have achieved the record operating frequency of 1.1 THz and show that substantially higher frequencies should be also achievable with RTD oscillators. RTD oscillators are extremely compact (less than a square millimeter) room-temperature sources of coherent cw THz radiation. Such sources should enable plenty of real-world THz applications.

  11. DNA detection by THz pumping

    International Nuclear Information System (INIS)

    DNA semiconductor detection and sequencing is considered to be the most promising approach for future discoveries in genome and proteome research which is dramatically dependent on the challenges faced by semiconductor nanotechnologies. DNA pH-sensing with ion-sensitive field effect transistor (ISFET) is well-known to be a successfully applied electronic platform for genetic research. However this method lacks fundamentally in chemical specificity. Here we develop the first ever silicon nanosandwich pump device, which provides both the excitation of DNA fragments’ self-resonant modes and the feedback for current-voltage measurements at room temperature. This device allows direct detection of singlestranded label-free oligonucleotides by measuring their THz frequency response in aqueous solution. These results provide a new insight into the nanobioelectronics for the future real-time technologies of direct gene observations

  12. DNA detection by THz pumping

    Energy Technology Data Exchange (ETDEWEB)

    Chernev, A. L. [Russian Academy of Sciences, St. Petersburg Academic University—Nanotechnology Research and Education Centre (Russian Federation); Bagraev, N. T.; Klyachkin, L. E. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Emelyanov, A. K.; Dubina, M. V. [Russian Academy of Sciences, St. Petersburg Academic University—Nanotechnology Research and Education Centre (Russian Federation)

    2015-07-15

    DNA semiconductor detection and sequencing is considered to be the most promising approach for future discoveries in genome and proteome research which is dramatically dependent on the challenges faced by semiconductor nanotechnologies. DNA pH-sensing with ion-sensitive field effect transistor (ISFET) is well-known to be a successfully applied electronic platform for genetic research. However this method lacks fundamentally in chemical specificity. Here we develop the first ever silicon nanosandwich pump device, which provides both the excitation of DNA fragments’ self-resonant modes and the feedback for current-voltage measurements at room temperature. This device allows direct detection of singlestranded label-free oligonucleotides by measuring their THz frequency response in aqueous solution. These results provide a new insight into the nanobioelectronics for the future real-time technologies of direct gene observations.

  13. Engineering chromatic dispersion and effective nonlinearity in a dual-slot waveguide.

    Science.gov (United States)

    Liu, Yan; Yan, Jing; Han, Genquan

    2014-09-20

    In this paper, we propose a new dual slot based on rib-like structure, which exhibits a flat and near-zero dispersion over a 198 nm wide wavelength range. Chromatic dispersion of dual-slot silicon (Si) waveguide is mainly determined by waveguide dispersion due to the manipulating mode effective area rather than by the material dispersion. Moreover, the nonlinear coefficient and effective mode area of the waveguide are also explored in detail. A nonlinear coefficient of 1460/m/W at 1550 nm is achieved, which is 10 times larger than that of the Si rib waveguide. By changing different waveguide variables, both the dispersion and nonlinear coefficient can be tailored, thus enabling the potential for a highly nonlinear waveguide with uniform dispersion over a wide wavelength range, which could benefit the performance of broadband optical signal systems.

  14. Computational Investigations of THz Transmittance in the Atmosphere

    OpenAIRE

    Yang Xingyu; Calhoun Casey; Calhoun Ronald

    2016-01-01

    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...

  15. All-optical controlling based on nonlinear graphene plasmonic waveguides.

    Science.gov (United States)

    Li, Jian; Tao, Jin; Chen, Zan Hui; Huang, Xu Guang

    2016-09-19

    We give the effective refractive index of graphene plasmonic waveguides with both linear and nonlinear effects based on the nonlinear cross-phase modulation, and address the effects of photo-induced refractive index change and absorption change. A non-resonant all-optical nonlinear graphene plasmonic switch with an ultra-compact size of 0.25 μm2 is proposed and numerically analyzed based on the dynamics of the photo-induced absorption change. The results show that the all-optical graphene plasmonic switch can realize a broad bandwidth over 5 THz, a potentially very high switching speed and an extinction ratio of 18.14 dB with the electric amplitude of the pump light of 1.5 × 107 V/m at the signal frequency of 28 THz. Our study could provide a possibility for future all-optical highly integrated optical components. PMID:27661951

  16. 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.

  17. Stabilized hot electron bolometer heterodyne receiver at 2.5 THz

    OpenAIRE

    Hayton, D.J.; Gao, J. R.; Kooi, J. W.; Ren, Y; Zhang, W; de Lange, G.

    2012-01-01

    We report on a method to stabilize a hot electron bolometer (HEB) mixer at 2.5 THz. The technique utilizes feedback control of the local oscillator (LO) laser power by means of a swing-arm actuator placed in the optical beam path. We demonstrate that this technique yields a factor of 50 improvement in the spectroscopic Allan variance time which is shown to be over 30 s in a 12 MHz noise fluctuation bandwidth. Furthermore, broadband signal direct detection effects may be minimized by this tech...

  18. Porous-core honeycomb bandgap THz fiber

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Jepsen, Peter Uhd;

    2011-01-01

    In this Letter we propose a novel (to our knowledge) porous-core honeycomb bandgap design. The holes of the porous core are the same size as the holes in the surrounding cladding, thereby giving the proposed fiber important manufacturing benefits. The fiber is shown to have a 0:35-THz......-wide fundamental bandgap centered at 1:05 THz. The calculated minimum loss of the fiber is 0:25 dB=cm....

  19. THz Near-Field Microscopy and Spectroscopy

    OpenAIRE

    von Ribbeck, Hans-Georg

    2015-01-01

    Imaging with THz radiation at nanoscale resolution is highly desirable for specific material investigations that cannot be obtained in other parts of the electromagnetic spectrum. Nevertheless, classical free-space focusing of THz waves is limited to a >100 μm spatial resolution, due to the diffraction limit. However, the scattering- type scanning near-field optical microscopy (s-SNOM) promises to break this diffraction barrier. In this work, the realization of s-SNOM and spectroscopy for the...

  20. 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...... communications enabled by photonics technologies, as well as the needed technical breakthroughs for achieving ultrafast data rates beyond 100Gbit/s...

  1. Modeling the THz spectrum of the bentazon

    Institute of Scientific and Technical Information of China (English)

    Huali Wang; Qiang Wang

    2011-01-01

    Bentazon, with chemical name 3-isopropyl-lH-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide,is a colorless to slightly brown,odorless crystalline solid.Bentazon is one of the synthetic,contact,and post-emergence herbicide used for selective control of broadleaf weeds and sedges in numerous crop fields.%Terahertz (THz) spectra of bentazon are determined within the range of 0.3-2.4 THz at room temperar ture. Density functional methods are used to compute the THz spectra using three different programs: GaussianO3 for isolated-molecule form, DMol3 and CRYSTAL09 for solid-state forms. Among the three, the computed THz spectrum of CRYSTAL09 shows better bond length and angle agreements with X-ray experimental results, and corresponds with observed THz experiment spectral characteristics. The isolated-molecule vibrational mode values are less by half than those derived from solid-state calculations. The last five peak positions of the two solid-state computations coincide with each other. Moreover, all the experimental THz absorption peaks are assigned by utilizing CRYSTAL09.

  2. THz Detection and Imaging using Rydberg Atoms

    Science.gov (United States)

    Wade, Christopher; Sibalic, Nikola; Kondo, Jorge; de Melo, Natalia; Adams, Charles; Weatherill, Kevin

    2016-05-01

    Atoms make excellent electromagnetic field sensors because each atom of the same isotope is identical and has well-studied, permanent properties allowing calibration to SI units. Thus far, atoms have not generally been exploited for terahertz detection because transitions from the atomic ground state are constrained to a limited selection of microwave and optical frequencies. In contrast, highly excited `Rydberg' states allow us access to many strong, electric dipole transitions from the RF to THz regimes. Recent advances in the coherent optical detection of Rydberg atoms have been exploited by a number of groups for precision microwave electrometry Here we report the demonstration of a room-temperature, cesium Rydberg gas as a THz to optical interface. We present two configurations: First, THz-induced fluorescence offers non-destructive and direct imaging of the THz field, providing real-time, single shot images. Second, we convert narrowband terahertz photons to infrared photons with 6% quantum efficiency allowing us to use nano-Watts of THz power to control micro-Watts of laser power on microsecond timescales. Exploiting hysteresis and a room-temperature phase transition in the response of the medium, we demonstrate a latching optical memory for sub pico-Joule THz pulses.

  3. 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...

  4. Laser mode complexity analysis in infrared waveguide free-electron lasers

    Science.gov (United States)

    Prazeres, Rui

    2016-06-01

    We analyze an optical phenomenon taking place in waveguide free-electron lasers, which disturbs, or forbids, operation in far infrared range. Waveguides in the optical cavity are used in far-infrared and THz ranges in order to avoid diffraction optical losses, and a hole coupling on output mirror is used for laser extraction. We show that, when the length of the waveguide exceeds a given limit, a phenomenon of "mode disorder" appears in the cavity, which makes the laser difficult, or impossible, to work properly. This phenomenon is even more important when the waveguide covers the whole length of the cavity. A numerical simulation describes this effect, which creates discontinuities of the laser power in the spectral domain. We show an example with an existing infrared Free-Electron Laser, which exhibits such discontinuities of the power, and where no convincing explanation was proposed until now.

  5. An ultra-broadband frequency-domain terahertz measurement system based on frequency conversion via DAST crystal with an optimized phase-matching condition

    International Nuclear Information System (INIS)

    By applying the frequency conversion technique to 4-dimethylamino-N-methyl-4-stilbazolium tosylate crystal, a monochromatic terahertz (THz) measurement system, including both generation and detection, has been developed over quite a broad frequency band, from 1.85 to 30 THz. In the case of frequency upconversion detection of THz waves, for the first time, we used gratings instead of filters to tackle the tough phase-matching conditions for broadband operations. By synchronizing the rotation of two gratings to extract the frequency upconverted signal, the infrared (IR) pumping beam can be tuned freely over 300 nm with decent diffraction efficiency and sufficient isolation between the weak frequency upconversion signal and the strong IR pumping beam to be realized. Such a large tuning range has overcome the limit of commercial filters with a fixed passband, while such a high optical density value has been beyond the limit of commercial tunable filters. Consequently, the proposed frequency domain system gives the largest THz frequency band. Unlike THz time-domain spectroscopy systems in which a fs laser is applied and broadband THz pulses are applied, our system works based on a ns laser and it can function at a single THz frequency with random frequency access ability from pulse to pulse. (letter)

  6. Corrugated waveguide monopulse feed

    Science.gov (United States)

    Elliott, R. D.; Clarricoats, P. J. B.

    1980-04-01

    The excitation coefficients of modes in a circular corrugated waveguide that arise when dominant modes are incident from a cluster of four square waveguides are calculated. Monopulse-like radiation patterns arise when modes in the input guides are appropriately phased. Factors influencing the crosspolar performance of the feed are discussed, and the dependence of the excitation coefficients on waveguide and junction parameters is predicted.

  7. Fractal Photonic Crystal Waveguides

    OpenAIRE

    Monsoriu, Juan A.; Zapata-Rodriguez, Carlos J.; Silvestre, Enrique; Furlan, Walter D.

    2004-01-01

    We propose a new class of one-dimensional (1D) photonic waveguides: the fractal photonic crystal waveguides (FPCWs). These structures are photonic crystal waveguides (PCWs) etched with fratal distribution of grooves such as Cantor bars. The transmission properties of the FPCWs are investigated and compared with those of the conventional 1D PCWs. It is shown that the FPCW transmission spectrum has self-similarity properties associated with the fractal distribution of grooves. Furthermore, FPCW...

  8. Fabrication of Ge nanocrystals doped silica-on-silicon waveguides and observation of their strong quantum confinement effect

    DEFF Research Database (Denmark)

    Ou, Haiyan; Rottwitt, Karsten

    2009-01-01

    cross-sectional waveguide structures were investigated by scanning electron microscopy. Transmission of the waveguide was measured using a broadband light source covering the wavelength range from 500 nm to 1700 nm, and the results were compared against transmission through a standard waveguide. Strong......Germanium (Ge) nanocrystals embedded in silica matrix is an interesting material for new optoelectronic devices. In this paper, standard silica-on-silicon waveguides with a core doped by Ge nanocrystals were fabricated using plasma enhanced chemical vapour deposition and reactive ion etching. The...

  9. THz Electro-absorption Effect in Quantum Dots

    DEFF Research Database (Denmark)

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

    2011-01-01

    In a THz pump - optical probe experiment we demonstrate an instantaneous electroabsorption effect in InGaAs/GaAs quantum dots, induced by electric field of a THz pulse with 3 THz bandwidth. Temporal features as fast as 460 fs were encoded onto an optical probe signal.......In a THz pump - optical probe experiment we demonstrate an instantaneous electroabsorption effect in InGaAs/GaAs quantum dots, induced by electric field of a THz pulse with 3 THz bandwidth. Temporal features as fast as 460 fs were encoded onto an optical probe signal....

  10. A broadband micro-machined far-infrared absorber

    Science.gov (United States)

    Wollack, E. J.; Datesman, A. M.; Jhabvala, C. A.; Miller, K. H.; Quijada, M. A.

    2016-05-01

    The experimental investigation of a broadband far-infrared meta-material absorber is described. The observed absorptance is >0.95 from 1 to 20 THz (300-15 μm) over a temperature range spanning 5-300 K. The meta-material, realized from an array of tapers ≈100 μm in length, is largely insensitive to the detailed geometry of these elements and is cryogenically compatible with silicon-based micro-machined technologies. The electromagnetic response is in general agreement with a physically motivated transmission line model.

  11. Intracavity generation of broadband biphotons in a thin crystal

    Science.gov (United States)

    Katamadze, K. G.; Borshchevskaya, N. A.; Dyakonov, I. V.; Paterova, A. V.; Kulik, S. P.

    2013-04-01

    We propose and realize a method of high intensity generation of broadband biphotons and achieve its value up to 150 THz. The source is based on a thin BBO crystal with a thickness of 100 microns, in which spontaneous parametric down-conversion takes place. To compensate for the intensity decrease of the down-conversion caused by the small thickness of the crystal, it is placed inside the cavity of an Ar+ laser. In general, this experiment relates to the widely discussed problem of two-photon shaping in the frequency and/or angular domain.

  12. A Broadband Micro-machined Far-Infrared Absorber

    CERN Document Server

    Wollack, Edward J; Jhabvala, Christine A; Miller, Kevin H; Quijada, Manuel A

    2016-01-01

    The experimental investigation of a broadband far-infrared meta-material absorber is described. The observed absorptance is $>\\,0.95$ from ${\\rm 1-20\\,THz}$ (${\\rm 300-15\\,\\mu m}$) over a temperature range spanning ${\\rm 5-300\\,K}$. The meta-material, realized from an array of tapers ${\\rm \\approx 100\\,\\mu m}$ in length, is largely insensitive to the detailed geometry of these elements and is cryogenically compatible with silicon-based micro-machined technologies. The electromagnetic response is in general agreement with a physically motivated transmission line model.

  13. Broadband Telecommunications Benchmarking Study

    OpenAIRE

    2004-01-01

    This report assesses Ireland's competitiveness relative to 21 countries, with particular focus on the broadband telecommunications requirements of the enterprise sector. The report outlines strengths and weaknesses that currently exist and progress that has already been made. It also makes a series of recommendations to further promote the development of the broadband market in Ireland.

  14. The Broadband Buzz.

    Science.gov (United States)

    Buchanan, Bruce

    2003-01-01

    "Broadband," the term for a variety of high-speed Internet options, opens up many opportunities for online classroom learning. Challenges for school districts include keeping the network running, training teachers, and paying for it. A sidebar lists broadband resources. (MLF)

  15. Waveguide arrangements based on adiabatic elimination

    Energy Technology Data Exchange (ETDEWEB)

    Suchowski, Haim; Mrejen, Michael; Wu, Chihhui; Zhang, Xiang

    2016-09-13

    This disclosure provides systems, methods, and apparatus related to nanophotonics. In one aspect, an arrangement of waveguides includes a substrate and three waveguides. Each of the three waveguides may be a linear waveguide. A second waveguide is positioned between a first waveguide and a third waveguide. The dimensions and positions of the first, the second, and the third waveguides are specified to substantially eliminate coupling between the first waveguide and the third waveguide over a distance of about 1 millimeter to 2 millimeters along lengths of the first waveguide, the second waveguide, and the third waveguide.

  16. 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)

  17. Mode-resolved Fabry-Perot experiment in low-loss Bragg-reflection waveguides.

    Science.gov (United States)

    Pressl, B; Günthner, T; Laiho, K; Geßler, J; Kamp, M; Höfling, S; Schneider, C; Weihs, G

    2015-12-28

    Based on the interaction between different spatial modes, semiconductor Bragg-reflection waveguides (BRWs) provide a highly functional platform for non-linear optics. For achieving any desired quantum optical functionality, we must control and engineer the properties of each spatial mode. To reach this purpose we extend the Fabry-Perot technique and achieve a detailed linear optical characterization of dispersive multimode semiconductor waveguides. With this efficient broadband spectral method we gain direct experimental access to the relevant modes of our BRWs and determine their group velocities. Furthermore, we show that our waveguides have lower than expected loss coefficients. This renders them suitable for integrated quantum optics applications.

  18. The Representation of a Broadband Vector Field

    Institute of Scientific and Technical Information of China (English)

    Qunyan Ren; Jean Pierre Hermand; Shengchun Piao

    2011-01-01

    Compared to a scalar pressure sensor,a vector sensor can provide a higher signal-to-noise ratio (SNR)signal and more detailed information on the sound field.Study on vector sensors and their applications have become a hot topic.Research on the representation of a vector field is highly relevant for extending the scope of vector sensor technology.This paper discusses the range-frequency distribution of the vector field due to a broadband acoustic source moving in a shallow-water waveguide as the self noise of a surface ship,and the vector extension of the waveguide impulse response measured over a limited frequency range using an active source of known waveform.From theory analysis and numerical simulation,the range-frequency representation of a vector field exhibits an interference structure qualitatively similar to that of the corresponding pressure field but,being quantitatively different,provides additional information on the waveguide,especially through the vertical component.For the range-frequency representation,physical quantities that can better exhibit the interference characteristics of the waveguide are the products of pressure and particle velocity and of the pressure and pressure gradient.An image processing method to effectively detect and isolate the individual striations from an interference structure was reviewed briefly.The representation of the vector impulse response was discussed according to two different measurement systems,also known as particle velocity and pressure gradient.The vector impulse response representation can not only provide additional information from pressure only but even more than that of the range-frequency representation.

  19. Improved Coupling to Plasmonic Slot Waveguide via a Resonant Nanoantenna

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Zenin, Vladimir A.; Malureanu, Radu;

    the effective index and propagation length of the slot waveguide mode. All experimental data are in very good correspondence with the numerical simulations. It was also confirmed that the serially connected dipole antennas represent the most efficient and simple design of nanocouplers. We report 26- and 15-fold......-limited optical waves into deep-subwavelength plasmonic waveguides. In this contribution we provide a systematic approach to design, fabricate and characterize an efficient, broadband, and compact dipole antenna nanocoupler for the telecom wavelength range around 1.55 µm. We consider the vertical coupling...... improvements in the coupling efficiency with two serially connected dipole and modified bow-tie antennas, respectively, as compared to that of the short-circuited waveguide termination. We also emphasize that the s-SNOM-based characterization procedure will become a standard robust technique for the plasmonic...

  20. THz lasing in a polariton system: Quantum theory

    OpenAIRE

    del Valle, Elena; Kavokin, Alexey

    2011-01-01

    We study the laser regime of terahertz (THz) emission from a semiconductor microcavity in the strong coupling regime, where optical transitions between upper and lower exciton-polariton modes are allowed due to the mixing of the upper mode with one of the dark exciton states. Using a system of master-Boltzmann equations describing both polariton modes and the THz mode, we calculate the first and second order coherences and the spectral shape of THz emission. This analysis shows that THz lasin...

  1. 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...... be controlled by the waveguide width and the dielectric spacer thickness and thus allows for straightforward fabrication of highly integrated waveguides by a single lithography step....

  2. Broadband adoption by SMES

    OpenAIRE

    Oni, Oluwasola

    2007-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. Because the benefits of broadband for businesses have been widely publicized, the UK government has tried to ensure that there is a wide and fast take-up of the technology. Initial figures showed that broadband adoption by SMEs was particularly slow and there has been little research on the use of broadband by businesses, particularly SMEs. An in-depth study into the roles and activities of t...

  3. 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...

  4. 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...

  5. An all-cryogenic THz transmission spectrometer

    OpenAIRE

    Burke, P. J.; Eisenstein, J. P.; Pfeiffer, L. N.; West, K.W.

    2002-01-01

    This paper describes a THz transmission spectrometer for the spectral range of 2-65 cm^-1 (100 GHz to 2 THz) with a spectral resolution of at least 1.8 cm^-1 (50 GHz) where the source, sample, and detector are all fully contained in a cryogenic environment. Cyclotron emission from a two-dimensional electron gas heated with an electrical current serves as a magnetic field tunable source. The spectrometer is demonstrated at 4.2 K by measuring the resonant cyclotron absorption of a second two di...

  6. 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....

  7. Output Enhancement of a THz Wave Based on a Surface-Emitted THz-Wave Parametric Oscillator

    Institute of Scientific and Technical Information of China (English)

    LI Zhong-Yang; YAO Jian-Quan; XU De-Gang; BING Pi-Bin; ZHONG Kai

    2011-01-01

    High-power nanosecond pulsed THz-wave radiation is achieved via a surface-emitted THz-wave parametric oscillator.One MgO:LiNbO3 crystal with large volume is used as the gain medium.THz-wave radiation from 1.084 THz to 2.654 THz is obtained.The maximum THz-wave average power is 5.8 μ W at 1.93 THz when the pump energy is 84 m J,corresponding to a energy conversion efficiency of 6.9 × 10-6.The polarization characteristics of THz wave are analyzed.During the experiments the radiations of the first-order and the second-order Stokes wave are observed.The THz wave has great scientific research value and wide applications in imaging,material detection,environmental monitoring,communication,astronomy,life sciences,national defense security and so on.[1-4] THz-wave parametric oscillators (TPOs)based on stimulated polariton scattering have many advantages,such as high efficient,coherent,tuning,narrow linewidth,compactness and room-temperature operation.[5-7] In recent years,TPOs have been developed rapidly.Stothard et al.[8] reported on a line-narrowed and widely tunable intracavity TPO,in which the linewidth of the THz wave is about 1 GHz,the tunning range is from 1 to 3 THz,and the peak power of the THz wave is about 3W.Wu et al.[9]reported on a TPO with recycled pump beam,and their experiment results show that the THz-wave out-put power increases almost four times in magnitude.%High-power nanosecond pulsed THz-wave radiation is achieved via a surface-emitted THz-wave parametric oscillator. One MgO:LiNbO3 crystal with large volume is used as the gain medium. THz-wave radiation from 1.084THz to 2.654THz is obtained. The maximum THz-wave average power is 5.8μW at 1.93THz when the pump energy is 84mJ, corresponding to a energy conversion efficiency of 6.9×10-6. The polarization characteristics of THz wave are analyzed. During the experiments the radiations of the first-order and the second-order Stokes wave are observed.

  8. 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

  9. Optical waveguide enhanced photovoltaics.

    Science.gov (United States)

    Rühle, Sven; Greenwald, Shlomit; Koren, Elad; Zaban, Arie

    2008-12-22

    Enhanced light to electric power conversion efficiency of photovoltaic cells with a low absorbance was achieved using waveguide integration. We present a proof of concept using a very thin dye-sensitized solar cell which absorbed only a small fraction of the light at normal incidence. The glass substrate in conjunction with the solar cells reflecting back contact formed a planar waveguide, which lead to more than four times higher conversion efficiency compared to conventional illumination at normal incidence. This illumination concept leads to a new type of multi-junction PV systems based on enforced spectral splitting along the waveguide.

  10. Photonic-integrated circuit for continuous-wave THz generation.

    Science.gov (United States)

    Theurer, Michael; Göbel, Thorsten; Stanze, Dennis; Troppenz, Ute; Soares, Francisco; Grote, Norbert; Schell, Martin

    2013-10-01

    We demonstrate a photonic-integrated circuit for continuous-wave (cw) terahertz (THz) generation. By comprising two lasers and an optical phase modulator on a single chip, the full control of the THz signal is enabled via a unique bidirectional operation technique. Integrated heaters allow for continuous tuning of the THz frequency over 570 GHz. Applied to a coherent cw THz photomixing system operated at 1.5 μm optical wavelength, we reach a signal-to-noise ratio of 44 dB at 1.25 THz, which is identical to the performance of a standard system based on discrete components.

  11. 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.

  12. 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 Eu...

  13. 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.

  14. 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...

  15. 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

  16. Broadband terahertz time-domain spectroscopy of ferroelectric LiTaO{sub 3}: Phonon-polariton dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, Seiji, E-mail: kojima@bk.tsukuba.ac.jp; Mori, Tatsuya, E-mail: kojima@bk.tsukuba.ac.jp [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan)

    2014-11-05

    The lowest frequency IR active A{sub 1}(z) and E(x) modes of a ferroelectric congruent lithium tantalate crystal were studied by the broadband polarized Terahertz Time-Domain Spectroscopy using the coherent THz radiation from 0.2 to 6.5 THz. The dispersion relations of the real and imaginary parts of a polariton wave vector were determined from the complex extraordinary and ordinary refractive indices for the A{sub 1}(z) and E(x) symmetry phonon-polaritons, respectively. The observed complex dispersion relations of two symmetries are in agreement within the experimental uncertainty with the calculated dispersion curves by the damped harmonic oscillator model.

  17. The contribution of microbunching instability to solar flare emission in the GHz to THz range of frequencies

    CERN Document Server

    Klopf, J Michael; Raulin, Jean-Pierre; Szpigel, Sérgio

    2014-01-01

    Recent solar flare observations in the sub-THz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the GHz range. Suggested interpretations explain the THz spectral component, but do not account for the simultaneous microwave component. We present a mechanism for producing the observed double-spectra. Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at higher frequency, thus producing a...

  18. Nonlinear ultrafast dynamics of high temperature YBa2Cu3O7–δ superconductors probed with THz pump / THz probe spectroscopy

    Directory of Open Access Journals (Sweden)

    Chen H. T.

    2013-03-01

    Full Text Available High power THz pulses induce near transparency in superconductive YBCO thin films below the critical temperature. THz pump/THz probe measurements reveal a decay of the induced transparency on the time scale of a few picoseconds.

  19. 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.

  20. Extreme skin depth waveguides

    CERN Document Server

    Jahani, Saman

    2014-01-01

    Recently, we introduced a paradigm shift in light confinement strategy and introduced a class of extreme skin depth (e-skid) photonic structures (S. Jahani and Z. Jacob, "Transparent sub-diffraction optics: nanoscale light confinement without metal," Optica 1, 96-100 (2014)). Here, we analytically establish that figures of merit related to light confinement in dielectric waveguides are fundamentally tied to the skin depth of waves in the cladding. We contrast the propagation characteristics of the fundamental mode of e-skid waveguides and conventional waveguides to show that the decay constant in the cladding is dramatically larger in e-skid waveguides, which is the origin of sub-diffraction confinement. Finally, we propose an approach to verify the reduced skin depth in experiment using the decrease in the Goos-H\\"anchen phase shift.

  1. Nanoscale waveguiding methods.

    Science.gov (United States)

    Wang, Chia-Jean; Lin, Lih Y

    2007-05-01

    While 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.

  2. High-temperature operation of broadband bidirectional terahertz quantum-cascade lasers

    Science.gov (United States)

    Khanal, Sudeep; Gao, Liang; Zhao, Le; Reno, John L.; Kumar, Sushil

    2016-09-01

    Terahertz quantum cascade lasers (QCLs) with a broadband gain medium could play an important role for sensing and spectroscopy since then distributed-feedback schemes could be utilized to produce laser arrays on a single semiconductor chip with wide spectral coverage. QCLs can be designed to emit at two different frequencies when biased with opposing electrical polarities. Here, terahertz QCLs with bidirectional operation are developed to achieve broadband lasing from the same semiconductor chip. A three-well design scheme with shallow-well GaAs/Al0.10Ga0.90As superlattices is developed to achieve high-temperature operation for bidirectional QCLs. It is shown that shallow-well heterostructures lead to optimal quantum-transport in the superlattice for bidirectional operation compared to the prevalent GaAs/Al0.15Ga0.85As material system. Broadband lasing in the frequency range of 3.1-3.7 THz is demonstrated for one QCL design, which achieves maximum operating temperatures of 147 K and 128 K respectively in opposing polarities. Dual-color lasing with large frequency separation is demonstrated for a second QCL, that emits at ~3.7 THz and operates up to 121 K in one polarity, and at ~2.7 THz up to 105 K in the opposing polarity. These are the highest operating temperatures achieved for broadband terahertz QCLs at the respective emission frequencies, and could lead to commercial development of broadband terahertz laser arrays.

  3. Ultra-fast pulse propagation in nonlinear graphene/silicon ridge waveguide.

    Science.gov (United States)

    Liu, Ken; Zhang, Jian Fa; Xu, Wei; Zhu, Zhi Hong; Guo, Chu Cai; Li, Xiu Jian; Qin, Shi Qiao

    2015-11-18

    We report the femtosecond laser propagation in a hybrid graphene/silicon ridge waveguide with demonstration of the ultra-large Kerr coefficient of graphene. We also fabricated a slot-like graphene/silicon ridge waveguide which can enhance its effective Kerr coefficient 1.5 times compared with the graphene/silicon ridge waveguide. Both transverse-electric-like (TE-like) mode and transverse-magnetic-like (TM-like) mode are experimentally measured and numerically analyzed. The results show nonlinearity dependence on mode polarization not in graphene/silicon ridge waveguide but in slot-like graphene/silicon ridge waveguide. Great spectral broadening was observed due to self-phase modulation (SPM) after propagation in the hybrid waveguide with length of 2 mm. Power dependence property of the slot-like hybrid waveguide is also measured and numerically analyzed. The results also confirm the effective Kerr coefficient estimation of the hybrid structures. Spectral blue shift of the output pulse was observed in the slot-like graphene/silicon ridge waveguide. One possible explanation is that the blue shift was caused by the ultra-fast free carrier effect with the optical absorption of the doped graphene. This interesting effect can be used for soliton compression in femtosecond region. We also discussed the broadband anomalous dispersion of the Kerr coefficient of graphene.

  4. MEASUREMENTS OF HIGH-FIELD THZ INDUCED PHOTOCURRENTS IN SEMICONDUCTORS

    Energy Technology Data Exchange (ETDEWEB)

    Wiczer, M.; Lindenberg, A.

    2008-01-01

    THz pulses have provided a useful tool for probing the time-resolved dynamics of free carriers in a system. However, the development of methods to produce intense THz radiation has been slow. We have developed a method for producing intense ultra-short THz pulses, which have a full width at half maximum of 300 fs — approximately a half cycle of THz radiation. These intense half cycle pulses (HCPs) allowed us to use THz radiation as a source of excitation. By exposing the semiconductor indium antimonide (InSb) to intense THz HCP radiation, we have observed non-linear optical effects which suggest the generation of new free carriers by below band-gap THz photons. This generation of free carriers appears to be due to an avalanche multiplication process which then induces a current in the time-scale of our THz pulse. This amplifi cation on such a short timescale suggests the possibility of an ultrafast detector of weak above band-gap radiation. We constructed a device which detects these currents by painting an electrode structure on the surface of the semiconductor. The currents induced across the electrodes by this avalanche multiplication process were measured and compared with other measurements of this non-linear optical process. We successfully measured THz induced currents in InSb, suggesting promise towards the development of an ultra-fast detector. Further, we have gained insight into a possible physical explanation of the THz induced free carriers we observe in InSb.

  5. Passive broadband acoustic thermometry

    Science.gov (United States)

    Anosov, A. A.; Belyaev, R. V.; Klin'shov, V. V.; Mansfel'd, A. D.; Subochev, P. V.

    2016-04-01

    The 1D internal (core) temperature profiles for the model object (plasticine) and the human hand are reconstructed using the passive acoustothermometric broadband probing data. Thermal acoustic radiation is detected by a broadband (0.8-3.5 MHz) acoustic radiometer. The temperature distribution is reconstructed using a priori information corresponding to the experimental conditions. The temperature distribution for the heated model object is assumed to be monotonic. For the hand, we assume that the temperature distribution satisfies the heat-conduction equation taking into account the blood flow. The average error of reconstruction determined for plasticine from the results of independent temperature measurements is 0.6 K for a measuring time of 25 s. The reconstructed value of the core temperature of the hand (36°C) generally corresponds to physiological data. The obtained results make it possible to use passive broadband acoustic probing for measuring the core temperatures in medical procedures associated with heating of human organism tissues.

  6. 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 o...

  7. Theoretical and Experimental studies on CH3OH THz Laser Pumped by Pulse Carbon Dioxide Laser

    Science.gov (United States)

    Fei, Fei; Jing, Wang; Zhaoshuo, Tian; Yanchao, Zhang; Shiyou, Fu; Qi, Wang

    2011-02-01

    In this paper, according to the molecular structure and vibration mode of micro-asymmetric gyroscope CH3OH molecule, dynamic process of optically pumped Terahertz laser is analyzed theoretically. The rate equation models based on three level systems are given according to the theory of typical laser rate equation. The output THz pulsed laser waveform is obtained by solving the rate equation model. An all-metal Terahertz laser pumped by RF waveguide carbon dioxide laser is designed with CH3OH as its working gas. The pulsed Terahertz laser output is obtained. The waveform and repetition frequency of the optically pumped laser are measured in the experiments. The Terahertz laser designed does not need water cooling system. It also has the advantages of simple structure and small size.

  8. 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.; 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 (x 12) from a microwave synthesizer at approx. 15 GHz. Both laser and reference radiations are coupled into a bolometer mixer, resulting in a beat signal, which is fed into a phase-lock loop. The spectral analysis of the beat signal confirms that the QCL is phase locked. This result opens the possibility to extend heterodyne interferometers into the far-infrared range.

  9. Photonic generation for multichannel THz wireless communication.

    Science.gov (United States)

    Shams, Haymen; Fice, Martyn J; Balakier, Katarzyna; Renaud, Cyril C; van Dijk, Frédéric; Seeds, Alwyn J

    2014-09-22

    We experimentally demonstrate photonic generation of a multichannel THz wireless signal at carrier frequency 200 GHz, with data rate up to 75 Gbps in QPSK modulation format, using an optical heterodyne technique and digital coherent detection. BER measurements were carried out for three subcarriers each modulated with 5 Gbaud QPSK or for two subcarriers modulated with 10 Gbaud QPSK, giving a total speed of 30 Gbps or 40 Gbps, respectively. The system evaluation was also performed with three subcarriers modulated with 12.5 Gbaud QPSK (75 Gbps total) without and with 40 km fibre transmission. The proposed system enhances the capacity of high-speed THz wireless transmission by using spectrally efficient modulated subcarriers spaced at the baud rate. This approach increases the overall transmission capacity and reduces the bandwidth requirement for electronic devices. PMID:25321815

  10. Photonic generation for multichannel THz wireless communication.

    Science.gov (United States)

    Shams, Haymen; Fice, Martyn J; Balakier, Katarzyna; Renaud, Cyril C; van Dijk, Frédéric; Seeds, Alwyn J

    2014-09-22

    We experimentally demonstrate photonic generation of a multichannel THz wireless signal at carrier frequency 200 GHz, with data rate up to 75 Gbps in QPSK modulation format, using an optical heterodyne technique and digital coherent detection. BER measurements were carried out for three subcarriers each modulated with 5 Gbaud QPSK or for two subcarriers modulated with 10 Gbaud QPSK, giving a total speed of 30 Gbps or 40 Gbps, respectively. The system evaluation was also performed with three subcarriers modulated with 12.5 Gbaud QPSK (75 Gbps total) without and with 40 km fibre transmission. The proposed system enhances the capacity of high-speed THz wireless transmission by using spectrally efficient modulated subcarriers spaced at the baud rate. This approach increases the overall transmission capacity and reduces the bandwidth requirement for electronic devices.

  11. WSPEC: A Waveguide Filter Bank Spectrometer

    CERN Document Server

    Che, George; Underhill, Matthew; Mauskopf, Philip; Groppi, Christopher; Jones, Glenn; Johnson, Bradley; McCarrick, Heather; Flanigan, Daniel; Day, Peter

    2015-01-01

    We have designed, fabricated, and measured a 5-channel prototype spectrometer pixel operating in the WR10 band to demonstrate a novel moderate-resolution (R=f/{\\Delta}f~100), multi-pixel, broadband, spectrometer concept for mm and submm-wave astronomy. Our design implements a transmission line filter bank using waveguide resonant cavities as a series of narrow-band filters, each coupled to an aluminum kinetic inductance detector (KID). This technology has the potential to perform the next generation of spectroscopic observations needed to drastically improve our understanding of the epoch of reionization (EoR), star formation, and large-scale structure of the universe. We present our design concept, results from measurements on our prototype device, and the latest progress on our efforts to develop a 4-pixel demonstrator instrument operating in the 130-250 GHz band.

  12. Current activities at the DELTA THz beamline

    Energy Technology Data Exchange (ETDEWEB)

    Ungelenk, Peter; Hoener, Markus; Huck, Holger; Khan, Shaukat; Molo, Robert; Schick, Andreas; Zeinalzadeh, Maryam [Center for Synchrotron Radiation (DELTA), TU Dortmund University, 44227 Dortmund (Germany)

    2013-07-01

    In addition to an InSb Bolometer, which detects laser-induced coherent THz pulses at the synchrotron light source DELTA since June 2011, a Fourier transform infrared spectrometer is currently being commissioned. Furthermore, a fast hot-electron bolometer has been used in cooperation with the Karlsruhe Institute of Technology to study the evolution of the laser-induced electron density modulation over several revolutions in the storage ring.

  13. Current activities at the DELTA THz beamline

    International Nuclear Information System (INIS)

    In addition to an InSb Bolometer, which detects laser-induced coherent THz pulses at the synchrotron light source DELTA since June 2011, a Fourier transform infrared spectrometer is currently being commissioned. Furthermore, a fast hot-electron bolometer has been used in cooperation with the Karlsruhe Institute of Technology to study the evolution of the laser-induced electron density modulation over several revolutions in the storage ring.

  14. 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....

  15. THz imaging system with the IJJ emitter

    Science.gov (United States)

    Tsujimoto, Manabu; Minami, Hidetoshi; Sawamura, Masashi; Delfanazari, Kaveh; Yamamoto, Takashi; Kashiwagi, Takanari; Kadowaki, Kazuo

    2011-03-01

    The intrinsic Josephson junction (IJJ) emitter consisted of thousands of IJJs uniformly stacked in single crystalline high-Tc superconductor Bi 2 Sr 2 CaCu 2 O8 + δ (Bi-2212) [L. Ozyuzer et al., Science 318, (2007) 1291.] is expected to be a novel source of the continuous terahertz electromagnetic waves (THz-waves). The maximum emission power of tens of microwatts recently obtained with the mesa structure of IJJs seems to be sufficient to make use of the IJJ emitter for some practical applications such as THz imaging. According to the cavity resonance condition, we can control the radiation frequency by changing the geometrical size of the mesa. In this study, we develop the THz imaging system with IJJ emitter. In the presentation, we will show some transparent images of standard specimens obtained by the raster scanning method. Also, we will mention some problems to be solved for the future applications of the IJJ emitter. CREST-JST, WPI-MANA, Strategic Initiative A (University of Tsukuba).

  16. THz polarization difference imaging of aqueous targets

    Science.gov (United States)

    Sung, Shijun; Bajwa, Neha; Ramirez, Lucia; Grundfest, Warren; Taylor, Zachary

    2015-08-01

    This paper describes the basic design, implementation, and testing of a polarization difference imaging system for use on aqueous targets. The ultimate performance limitation of THz imaging in many active areas of research is clutter from surface geometry. While the signal to nose ratio (SNR) of standard THz imaging systems is quite large, the signal to clutter ratio (SCR) often faced in an imaging application is orders of magnitude lower and, in many cases, lower than the contrast to noise (CNR) resulting in imagery where the contrast mechanism of interest does not significantly contribute to the overall observed contrast. To overcome these limitations we develop a system that uses a circularly polarized source and linearly polarized detectors to acquire images of transverse electric (TE) and transverse magnetic (TM) reflectivities of the target over the same field of view. Geletin based tissue mimicking phantoms are fabricated with spatially varying water content and modified with a range of surface topologies and surface roughness. TE and TM images are combined to yield self-calibrated clutter-suppressed images. The resulting image indicates that the imaging field clutter affected both polarization channels nearly equally allowing the system to resolve differences in phantom water content. This design is a step toward windowless THz imaging capability critical for clinical translation where patient imaging is dominated by clutter.

  17. Experimental and theoretical study on THz spectrum artesunate

    Science.gov (United States)

    Zhang, Ai-Bing; Kong, Ling-Gao; Wang, Shi-Jin; Li, Lei; Zheng, Xiang-Zhi

    2008-10-01

    Artesunate is a very effective drug to treat malaria. They are studied experimentally by Terahertz (THz) time-domain spectroscopy (THz-TDS), and the characteristic absorption spectra are obtained in the range of 0.2 to 2.6 THz. The vibrational frequencies are calculated using the density functional theory (DFT). Theoretical results show that 0.71, 1.94 and 2.46 THz are significant agreement with the experimental results in 0.87, 1.82 and 2.46THz, and identification of vibrational modes are given. The calculated results further confirm that the characteristic frequencies come from the collective vibrational modes. The results suggest that the use of the THz-TDS technique can be an effective way to inspect for Chinese medicine.

  18. High density THz frequency comb produced by coherent synchrotron radiation

    CERN Document Server

    Tammaro, S; Roy, P; Lampin, J -F; Ducournau, G; Cuisset, A; Hindle, F; Mouret, G

    2014-01-01

    Frequency combs (FC) have radically changed the landscape of frequency metrology and high-resolution spectroscopy investigations extending tremendously the achievable resolution while increasing signal to noise ratio. Initially developed in the visible and near-IR spectral regions, the use of FC has been expanded to mid-IR, extreme ultra-violet and X-ray. Significant effort is presently dedicated to the generation of FC at THz frequencies. One solution based on converting a stabilized optical frequency comb using a photoconductive terahertz emitter, remains hampered by the low available THz power. Another approach is based on active mode locked THz quantum-cascade-lasers providing intense FC over a relatively limited spectral extension. Alternatively, here we show that dense powerful THz FC is generated over one decade of frequency by coherent synchrotron radiation (CSR). In this mode, the entire ring behaves in a similar fashion to a THz resonator wherein electron bunches emit powerful THz pulses quasi-synch...

  19. DESIGN OF INTEGRATING WAVEGUIDE BIOSENSOR

    Science.gov (United States)

    The Integrating Waveguide Biosensor allows for rapid and sensitive detection of pathogenic agents, cells and proteins via immunoassay or PCR products. The analytes are captured on the surface of the waveguide and then tagged with fluorescent labels. The waveguides are illuminated by excitation light...

  20. 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...... crystal semiconductor optical amplier. As a step towards such a component, photonic crystal waveguides with a single quantum well, 10 quantum wells and three layers of quantum dots are fabricated and characterized. An experimental study of the amplied spontaneous emission and a implied transmission...... are presented in this thesis. A variation of photonic crystal design parameters are used leading to a spectral shift of the dispersion, it is veried that the observed effects shift accordingly. An enhancement of the amplified spontaneous emission was observed close to the band edge, where light is slowed down...

  1. Design of an on-line measuring system for 0.14 THz high-power terahertz pulse

    Energy Technology Data Exchange (ETDEWEB)

    Wang Guangqiang [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Wang Jianguo; Li Xiaoze; Tong Changjiang; Wang Xuefeng, E-mail: wgq02@mails.tsinghua.edu.cn [Northwest Institute of Nuclear Technology, Xi' an 710024 (China)

    2011-02-01

    An on-line measuring system, including an aperture-coupling structure and a novel high-power pulse detector, is proposed in this paper to measure the output pulses from high-power 0.14THz surface wave oscillator (SWO). At first a T-type coupling structure between the TM{sub 01} mode of circular waveguide with radius of 6mm and TE{sub 10} mode of rectangular waveguide WR6 is designed. Based on loose coupling theory,the coupling degree of this structure is derived and calculated, reaching about -47dB with the aperture radius of 0.4mm and length of 0.5mm. The reasonable coincidence is found between the theoretical computation and numerical simulation employing the three-dimensional finite difference time domain method. Then a novel high-power terahertz pulse detector based on hot electron effect in semiconductors is developed for the detection of output pulses from T-type coupling structure. With hot electron theory, the working principle of the detector is elucidated, also its sensitivity is simply analyzed, showing that this detector is capable of handling the pulse power as high as 2kW. The present 0.14THz on-line measuring system would be convenient to monitor the terahertz pulse shape and pulse power during the application researches of SWO besides increasing the accuracy of its pulse power measurement.

  2. Untersuchung breitbandiger THz-Komponenten: Schottkydetektoren und photokonduktive Elemente

    OpenAIRE

    Schönherr, Daniel

    2012-01-01

    Der Terahertz (THz)-Bereich des elektromagnetischen Spektrums bietet aufgrund der besonderen Interaktion zwischen THz-Strahlung und vielen Materialien eine Reihe von interessanten Applikationsmöglichkeiten. Für einen breiten Einsatz fehlen jedoch nach wie vor kosteneffektive und kompakte Komponenten und Systeme. An diesem Punkt setzt die vorliegende Arbeit an. Der erste Teil der Arbeit behandelt die direkte Detektion von THz-Strahlung mittels antennengekoppelten Schottkydioden. Diese biet...

  3. Waveguide apparatuses and methods

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, James E.

    2016-05-10

    Optical fiber waveguides and related approaches are implemented to facilitate communication. As may be implemented in accordance with one or more embodiments, a waveguide has a substrate including a lattice structure having a plurality of lattice regions with a dielectric constant that is different than that of the substrate, a defect in the lattice, and one or more deviations from the lattice. The defect acts with trapped transverse modes (e.g., magnetic and/or electric modes) and facilitates wave propagation along a longitudinal direction while confining the wave transversely. The deviation(s) from the lattice produces additional modes and/or coupling effects.

  4. Waveguides for walking droplets

    CERN Document Server

    Filoux, Boris; Schlagheck, Peter; Vandewalle, Nicolas

    2015-01-01

    When gently placing a droplet onto a vertically vibrated bath, a drop can bounce permanently. Upon increasing the forcing acceleration, the droplet is propelled by the wave it generates and becomes a walker with a well defined speed. We investigate the confinement of a walker in different rectangular cavities, used as waveguides for the Faraday waves emitted by successive droplet bounces. By studying the walker velocities, we discover that 1d confinement is optimal for narrow channels. We also propose an analogy with waveguide models based on the observation of the Faraday instability within the channels.

  5. Design, Optimization & Evaluation of Tapered Waveguide With Cylindrical Waveguide

    Directory of Open Access Journals (Sweden)

    Harshukumar Khare

    2011-12-01

    Full Text Available Tapered Waveguide is a waveguide in which a physical or electrical characteristic changes continuously with distance along the axis of the waveguide. Tapered waveguide offer an excellent means of converting microwave mode sizes to connect Microwave devices of different cross-sectional dimensions. This paper discusses the waveguide component for interconnecting rectangular and circular waveguide using elliptical tapering. Model is designed for the frequency range from 2 to 4 GHz. Dominant Mode conversions ie from TE10 to TM11 is considered for tapering techniques. All simulations are done with CST Microwave studio. Simulation result shows that wave is properly propagated with no power reflection and low power loss. The resonant frequency is mainly varied with the diameter of cylindrical waveguide.

  6. Monitoring leaf water content with THz and sub-THz waves

    OpenAIRE

    Gente, Ralf; Koch, Martin

    2015-01-01

    Terahertz technology is still an evolving research field that attracts scientists with very different backgrounds working on a wide range of subjects. In the past two decades, it has been demonstrated that terahertz technology can provide a non-invasive tool for measuring and monitoring the water content of leaves and plants. In this paper we intend to review the different possibilities to perform in-vivo water status measurements on plants with the help of THz and sub-THz waves. The common b...

  7. THz quantum cascade lasers for standoff molecule detection.

    Energy Technology Data Exchange (ETDEWEB)

    Chow, Weng Wah; Wanke, Michael Clement; Lerttamrab, Maytee; Waldmueller, Ines

    2007-10-01

    Remote optical detection of molecules, agents, and energetic materials has many applications to national security interests. Currently there is significant interest in determining under what circumstances THz frequency coverage will aid in a complete sensing package. Sources of coherent THz frequency (i.e. 0.1 to 10 THz) electromagnetic radiation with requisite power levels, frequency agility, compactness and reliability represent the single greatest obstacle in establishing a THz technology base, but recent advances in semiconductor-based quantum cascade lasers (QCLs) offer huge improvements towards the ultimate THz source goals. This project advanced the development of narrow-linewidth THz quantum cascade lasers. We developed theoretical tools to guide the improvement of standard THz quantum cascade lasers, the investigation of nonlinear optics employing infrared QCLs, and the exploration of quantum coherence to improve QCL performance. The latter was aimed especially towards achieving high temperature operation. In addition we developed a computer algorithm capable of shifting the frequencies of an existing THz QCL to a different frequency and invented a new type of laser that may enable room temperature THz generation in a electrically driven solid-state source.

  8. 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.

  9. Compact THz radiation source based on photocathode RF gun

    Institute of Scientific and Technical Information of China (English)

    URAKAWA; JunJi

    2011-01-01

    Terahertz (THz) science and technology have already become the research highlight at present. In this paper, we put forward a proposal to generate THz radiation at tens of MW peak power. As a result of the ultrafast laser and the high accelerating field of photocathode RF gun, we can generate and accelerate an electron beam to several MeV, of which the bunch length is less than sub-ps. When the short electron bunches are injected into the wiggler, THz radiation based on Coherent Synchrotron Radiation could be achieved with tens of MW peak power. The whole THz FEL facility can be scaled to the size of a tabletop.

  10. Planar metamaterial-based beam-scanning broadband microwave antenna

    Energy Technology Data Exchange (ETDEWEB)

    Dhouibi, Abdallah [IEF, CNRS, UMR 8622, Univ. Paris-Sud, 91405 Orsay Cedex (France); Burokur, Shah Nawaz, E-mail: shah-nawaz.burokur@u-psud.fr; Lustrac, André de [IEF, CNRS, UMR 8622, Univ. Paris-Sud, 91405 Orsay Cedex (France); Univ. Paris-Ouest, 92410 Ville d' Avray (France)

    2014-05-21

    The broadband directive emission from the use of waveguided metamaterials is numerically and experimentally reported. The metamaterials, which are composed of non-resonant circular complementary closed ring structures printed on a dielectric substrate, are designed to obey the refractive index of a Luneburg lens. An arc array of planar radiating slot antennas placed at the periphery of the lens is used as wave launchers. A prototype of the lens associated with the feed structures has been fabricated using standard lithography techniques. To experimentally demonstrate the broadband focusing properties and directive emissions, far-field radiation patterns have been measured. Furthermore, this metamaterial-based lens can be used to achieve beam-scanning with a coverage of up to 120 °. Far-field measurements agree qualitatively with calculated near-field distributions.

  11. 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....

  12. Ultrafast nonlinear carrier dynamics in doped semiconductors in high THz fields

    OpenAIRE

    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.

  13. Realization of broadband cross-polarization conversion in transmission mode in the terahertz region using a single-layer metasurface.

    Science.gov (United States)

    Liu, Wenwei; Chen, Shuqi; Li, Zhancheng; Cheng, Hua; Yu, Ping; Li, Jianxiong; Tian, Jianguo

    2015-07-01

    We present the design specifications and in-depth analysis of a terahertz (THz) broadband cross-polarization converter composed of a single-layer metasurface. This device can convert linearly polarized light into its cross-polarization in transmission mode. Different from other polarization conversion devices, this effect results from the suppression and enhancement for different electric components. The broadband characteristic is also achieved by specific partial symmetries designed in the structure. The proposed polarization converter can aid in the development of novel plasmonic polarization devices, and can help to overcome certain limitations of the customary designs that have been proposed thus far. PMID:26125398

  14. 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.

  15. THz near-field spectral encoding imaging using a rainbow metasurface.

    Science.gov (United States)

    Lee, Kanghee; Choi, Hyun Joo; Son, Jaehyeon; Park, Hyun-Sung; Ahn, Jaewook; Min, Bumki

    2015-01-01

    We demonstrate a fast image acquisition technique in the terahertz range via spectral encoding using a metasurface. The metasurface is composed of spatially varying units of mesh filters that exhibit bandpass features. Each mesh filter is arranged such that the centre frequencies of the mesh filters are proportional to their position within the metasurface, similar to a rainbow. For imaging, the object is placed in front of the rainbow metasurface, and the image is reconstructed by measuring the transmitted broadband THz pulses through both the metasurface and the object. The 1D image information regarding the object is linearly mapped into the spectrum of the transmitted wave of the rainbow metasurface. Thus, 2D images can be successfully reconstructed using simple 1D data acquisition processes. PMID:26400502

  16. High efficiency THz-wave modulators based on conjugated polymer-based organic films

    International Nuclear Information System (INIS)

    A study of the modulation mechanisms of conjugated polymer-based organic films and high-efficiency, broadband and all-optically controlled terahertz modulators based on these films is presented in this paper. Under very low-level external laser excitation, modulation efficiency of more than 99% is achieved using MEH-PPV/Si, PFO/Si and F8BT/Si bilayers. By analyzing the changes in the photo-excited carrier density and photoconductivity with changes in the external laser intensity, we introduce a nonlinear photo-induced absorption process to explain the strong attenuation mechanism for the transmitted terahertz waves. Finally, a simple THz communication test is carried out to demonstrate the potential future applications of the high-efficiency all-optically controlled terahertz modulator. (paper)

  17. High efficiency THz-wave modulators based on conjugated polymer-based organic films

    Science.gov (United States)

    He, Ting; Zhang, Bo; Wang, Guo-cui; Zang, Meng-di; Hou, Yan-bing; Shen, Jing-ling

    2016-02-01

    A study of the modulation mechanisms of conjugated polymer-based organic films and high-efficiency, broadband and all-optically controlled terahertz modulators based on these films is presented in this paper. Under very low-level external laser excitation, modulation efficiency of more than 99% is achieved using MEH-PPV/Si, PFO/Si and F8BT/Si bilayers. By analyzing the changes in the photo-excited carrier density and photoconductivity with changes in the external laser intensity, we introduce a nonlinear photo-induced absorption process to explain the strong attenuation mechanism for the transmitted terahertz waves. Finally, a simple THz communication test is carried out to demonstrate the potential future applications of the high-efficiency all-optically controlled terahertz modulator.

  18. Coherent detection of THz waves based on THz-induced time-resolved luminescence quenching in bulk gallium arsenide.

    Science.gov (United States)

    Chu, Zheng; Liu, Jinsong; Wang, Kejia

    2012-05-01

    A kind of photoluminescence quenching, in which the time-resolved photoluminescence is modulated by a THz pulse, has been theoretically investigated by performing the ensemble Monte Carlo method in bulk gallium arsenide (GaAs) at room temperature. The quenching ratio could reach up to 50% under a strong THz field (100  kV/cm). The range in which luminescence quenching is linearly proportional to the THz field could be over 60  kV/cm. On the basis of these results, a principle for THz modulation and coherent detection is proposed. PMID:22555695

  19. Folded waveguide resonator

    DEFF Research Database (Denmark)

    2013-01-01

    A waveguide resonator comprising a number of side walls defining a cavity enclosed by said sidewalls defining the cavity; and two or more conductive plates extending into the cavity, each conductive plate having a first side and a second side opposite the first side, and wherein the conductive...

  20. Optical waveguide sensors

    NARCIS (Netherlands)

    Fluitman, J.; Popma, Th.

    1986-01-01

    An overview of the field of optical waveguide sensors is presented. Some emphasis is laid on the development of a single scheme under which the diversity of sensor principles can be arranged. First three types of sensors are distinguished: intrinsic, extrinsic and active. Next, two steps are disting

  1. 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.

  2. THz optics and metamaterials: Design, fabrication and characterization

    Science.gov (United States)

    Turaga, Shuvan Prashant

    In the past decade, terahertz(THz) based optics and metamaterials have been extensively researched to create components and devices in the frequency range of 0.1 to 5 THz also known as 'THz gap'. Metamaterials, in particular, have realized concepts such as negative refraction, slow light and superlensing through artificially engineered media. The naturally available materials have very weak interaction of terahertz light. Therefore, the design of THz metamaterials to manipulate THz radiation is an important task towards furthering the usage of terahertz light for practical applications. The thesis involved the development of two lab facilities for fabrication and characterization. A state-of-the-art two photon lithography( TPL) system was developed which enables us to manufacture 3D structures with sub-diffraction limit resolution(280nm at 800 nm wavelength). The software was written to enable easy fabrication of multiple structures with different algorithms. For characterizing our metamaterial structures in the terahertz regime, a THz time-domain spectroscopy(THz-TDS) and imaging system was built. This transmission based spectrometer has a dynamic range of 50 dB at 0.5 THz and a bandwidth of about 2.5 THz. To demonstrate the application of these home-built facilities, the metamaterials in the THz regime were fabricated using TPL and UV lithography. To investigate conductive coupling effects in meta-atoms, a new design was proposed, fabricated and characterized. As an application of TPL, free standing polymer helices were fabricated and coated with silver electroless plating. These silver helical metamaterials have potential application as circular polarizers in the MIR and THz regimes. The aspect ratio effects of these helical metamaterials were also studied in order to improve their polarizing performance.

  3. Design of terahertz metal-dielectric-metal waveguide with microfluidic sensing stub

    Science.gov (United States)

    Li, Xiangjun; Song, Jian; Zhang, John X. J.

    2016-02-01

    We design a terahertz (THz) metal-dielectric-metal (MDM) waveguide sensor with embedded microfluidic channel suitable for sensing the refractive index variations in liquid. The transmission properties are described using transmission line model (TLM) and numerically simulated using finite-difference time domain (FDTD) method. The sensing characteristics of the structure are systematically analyzed through the examination of the transmission spectrum. The results reveal a series of pronounced resonance peaks in the transmission spectrum, which has linear relationship with the refractive index variation of the material under investigation. For detecting the presence of various cancer cells flowing through the microfluidic channel, we designed and optimized the structural parameters of the THz-MDM sensor and achieved a theoretical value of the refractive index detection sensitivity as high as 0.457 THz/RIU for a 20 μm × 24 μmcross-section channel. This work shows great promise toward realizing a compact THz refractive index sensor with high sensitivity for identifying the signatures of biological samples in liquid.

  4. THz and above THz electron or hole oscillations in DNA dimers and trimers

    Energy Technology Data Exchange (ETDEWEB)

    Lambropoulos, Konstantinos; Kaklamanis, Konstantinos; Georgiadis, Georgios; Simserides, Constantinos [National and Kapodistrian University of Athens, Faculty of Physics, Department of Solid State Physics, Zografos (Greece)

    2014-07-15

    A non conventional source or receiver of THz and above THz electromagnetic radiation is proposed. Specifically, electron or hole oscillations in DNA dimers (two interacting DNA base-pairs or monomers) are predicted, with frequency in the range f ∼ 0.25-100 THz (period T ∼ 10-4000 fs) i.e. potentially absorbing or emitting electromagnetic radiation mainly in the mid- and far-infrared with wavelengths ∼ 3-1200 μm. The efficiency of charge transfer between the two monomers which make up the dimer is described with the maximum transfer percentage p and the pure maximum transfer rate pf. For dimers made of identical monomers p = 1, but for dimers made of different monomers p < 1. The investigation is extended to DNA trimers (three interacting DNA base-pairs or monomers). For trimers made of identical monomers the carrier oscillates periodically with f ∼ 0.5-33 THz (period T ∼ 30-2000 fs); for 0 times crosswise purines p = 1, for 1 or 2 times crosswise purines p < 1. For trimers made of different monomers the carrier movement may be non periodic. Generally, increasing the number of monomers above three, the system becomes more complex and periodicity is lost; even for the simplest tetramer the carrier movement is not periodic. (copyright 2014 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. A study of different metals employed in metal-metal waveguides for terahertz quantum cascade lasers

    Science.gov (United States)

    Szymański, Michał; Szerling, Anna; Kosiel, Kamil; Płuska, Mariusz

    2016-07-01

    We consider the possibility of improvement of metal-metal waveguides designed for terahertz quantum cascade lasers (THz QCL) with respect to waveguide losses. We calculate {α\\text{wg}} solving Helmholtz equation by transfer matrix method. The essence of our work is the error analysis. We notice that the refractive indices of metals in THz range are known with very poor accuracy. We present divergences among numerous measurements and calculations reported in the literature. In addition, we point out that optical properties of metals and semiconductors depend on temperature which varies throughout the working device. At last, we present our scanning electron microscope photos showing that semiconductor-metal and metal-metal interfaces are not perfect. In adjacent areas mixing of materials occurs and hence the spatial refractive index distribution is perturbed. Our error analysis shows that today’s accuracy of refractive index data (±37% is the best reported in the literature) makes the problem of optimization of considered waveguides ambiguous. According to our calculations the precision level of about  ±10% is required. Once improving the precision turns out to be impossible, we suggest focusing the design works on criteria such as choosing metals minimizing the risk of damaging the active region by atom migration, providing the best ohmic contact or allowing the most effective heat removal.

  6. Metasurface Broadband Solar Absorber

    OpenAIRE

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Milan Sykora; Nina R. Weisse-Bernstein; Luk, Ting S.; Antoinette J. Taylor; Dalvit, Diego A. R.; Hou-Tong Chen

    2016-01-01

    We demonstrate a broadband, polarization independent, omnidirectional absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low emissivity at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experiment...

  7. Silicon Micromachined Microlens Array for THz Antennas

    Science.gov (United States)

    Lee, Choonsup; Chattopadhyay, Goutam; Mehdi, IImran; Gill, John J.; Jung-Kubiak, Cecile D.; Llombart, Nuria

    2013-01-01

    5 5 silicon microlens array was developed using a silicon micromachining technique for a silicon-based THz antenna array. The feature of the silicon micromachining technique enables one to microfabricate an unlimited number of microlens arrays at one time with good uniformity on a silicon wafer. This technique will resolve one of the key issues in building a THz camera, which is to integrate antennas in a detector array. The conventional approach of building single-pixel receivers and stacking them to form a multi-pixel receiver is not suited at THz because a single-pixel receiver already has difficulty fitting into mass, volume, and power budgets, especially in space applications. In this proposed technique, one has controllability on both diameter and curvature of a silicon microlens. First of all, the diameter of microlens depends on how thick photoresist one could coat and pattern. So far, the diameter of a 6- mm photoresist microlens with 400 m in height has been successfully microfabricated. Based on current researchers experiences, a diameter larger than 1-cm photoresist microlens array would be feasible. In order to control the curvature of the microlens, the following process variables could be used: 1. Amount of photoresist: It determines the curvature of the photoresist microlens. Since the photoresist lens is transferred onto the silicon substrate, it will directly control the curvature of the silicon microlens. 2. Etching selectivity between photoresist and silicon: The photoresist microlens is formed by thermal reflow. In order to transfer the exact photoresist curvature onto silicon, there needs to be etching selectivity of 1:1 between silicon and photoresist. However, by varying the etching selectivity, one could control the curvature of the silicon microlens. The figure shows the microfabricated silicon microlens 5 x5 array. The diameter of the microlens located in the center is about 2.5 mm. The measured 3-D profile of the microlens surface has a

  8. Realization of THz Band Mixer Using Graphene

    Directory of Open Access Journals (Sweden)

    Ensieh Ghasemi Mizuji

    2014-04-01

    Full Text Available In this article a new method for creating mixer component in infrared and THz is suggested. Since the nonlinear property of admittance creates frequency components that do not exist in the input signal and the electrical conductivity is associated with admittance, in our work we have proven and simulated that the nonlinear property of graphene admittance can produce mixer component. The simulation results show that the mixer component is larger than other components, therefore the mixer works properly. Because of nano scale of graphene structure, this method paves the road to achieve super compact circuits.

  9. Material Inspection Using THz and Thermal Wave

    Science.gov (United States)

    Zhang, Cunlin; Mu, Kaijun; Li, Yanhong; Zhang, X.-C.

    2007-03-01

    Terahertz (THz) and thermal wave imaging technologies are complementary inspection modalities for use in non-contact and non-destructive evaluation. Both of them are applied in order to evaluate damages on a variety of composite samples. We will also report the test of a large number of insulation foam panels used in NASA's External Fuel Tank through pulse and CW terahertz systems. The study of defects using the two techniques in selected materials, including metal plates, carbon fibers, glass fibers, carbon silicon composites, etc is also shown.

  10. THz and infrared metamaterial polarization converter with tunable ellipticity

    DEFF Research Database (Denmark)

    Markovich, D. L.; Andryieuski, Andrei; Lavrinenko, Andrei

    2012-01-01

    In this contribution we present the metamaterial based polarization converter from linear to elliptical polarization with a desired ellipticity and ellipse orientation. We show two designs with the conversion efficiency 50% for the frequencies around 1 THz and 193 THz. The proposed device is...... realistic for fabrication and can be used as a polarizer or a polarization compensator....

  11. Direct Visualization of a Polariton Resonator in the THz Regime.

    Science.gov (United States)

    Stoyanov, Nikolay; Feurer, T; Ward, David; Statz, Eric; Nelson, Keith

    2004-05-31

    We report fabrication of a THz phonon-polariton resonator in a single crystal of LiNbO3 using femtosecond laser machining with high energy pulses. Fundamental and overtone resonator modes are excited selectively and monitored through spatiotemporal imaging. The resonator is integrated into a single solid-state platform that can include THz generation, manipulation, readout and other functionalities. PMID:19475075

  12. 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 th...

  13. 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...

  14. A scanned beam THz imaging system for medical applications

    Science.gov (United States)

    Taylor, Zachary D.; Li, Wenzao; Suen, Jon; Tewari, Priyamvada; Bennett, David; Bajwa, Neha; Brown, Elliott; Culjat, Martin; Grundfest, Warren; Singh, Rahul

    2011-10-01

    THz medical imaging has been a topic of increased interest recently due largely to improvements in source and detector technology and the identification of suitable applications. One aspect of THz medical imaging research not often adequately addressed is pixel acquisition rate and phenomenology. The majority of active THz imaging systems use translation stages to raster scan a sample beneath a fixed THz beam. While these techniques have produced high resolution images of characterization targets and animal models they do not scale well to human imaging where clinicians are unwilling to place patients on large translation stages. This paper presents a scanned beam THz imaging system that can acquire a 1 cm2 area with 1 mm2 pixels and a per-pixel SNR of 40 dB in less than 5 seconds. The system translates a focused THz beam across a stationary target using a spinning polygonal mirror and HDPE objective lens. The illumination is centered at 525 GHz with ~ 125 GHz of response normalized bandwidth and the component layout is designed to optically co-locate the stationary source and detector ensuring normal incidence across a 50 mm × 50 mm field of view at standoff of 190 mm. Component characterization and images of a test target are presented. These results are some of the first ever reported for a short standoff, high resolution, scanned beam THz imaging system and represent an important step forward for practical integration of THz medical imaging where fast image acquisition times and stationary targets (patients) are requisite.

  15. 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...

  16. Characterizing THz Coherent Synchrotron Radiation at Femtosecond Linear Accelerator

    Institute of Scientific and Technical Information of China (English)

    LIN Xu-Ling; ZHANG Jian-Bing; LU YU; LUO Feng; LU Shan-Liang; YU Tie-Min; DAI Zhi-Min

    2009-01-01

    The generation and observation of coherent THz synchrotron radiation from femtosecond electron bunches in the Shanghai Institute of Applied Physics femtosecond accelerator device is reported.We describe the experiment setup and present the first result of THz radiation properties such as power and spectrum.

  17. Investigation of bovine serum albumin glycation by THz spectroscopy

    Science.gov (United States)

    Cherkasova, Olga P.; Nazarov, Maxim M.; Shkurinov, Alexander P.

    2016-04-01

    Protein glycation is accelerated under hyperglycemic conditions resulting to loss in the structure and biological functions of proteins. The transmission THz spectroscopy has been used for measuring of bovine serum albumin glycation dynamics. It was found that amplitude of albumin THz absorption depends on type of sugars and incubation time.

  18. Broadband multi-interferometer spectroscopy in high magnetic fields: From THz to visible

    Science.gov (United States)

    Padilla, W. J.; Li, Z. Q.; Burch, K. S.; Lee, Y. S.; Mikolaitis, K. J.; Basov, D. N.

    2004-11-01

    We present a system capable of broad band frequency domain spectroscopy in the range 6-20 000 cm-1 at cryogenic temperatures. The apparatus couples two different interferometers to a 9 Tesla superconducting split coil magnet and is designed to work with various detectors, including thermal bolometers and semiconducting detectors. The optical layout utilizes an intermediate focus while preserving optical f/#'s throughout enabling DC magnetic field measurements of small crystals with polarized light in both Voight and Faraday geometries. A reference channel eliminates errors associated with system drift and facilitates determination of the optical constants. For transparent samples, simultaneous reflection and transmission can be performed.

  19. THz time-domain spectroscopy of amino acids

    Institute of Scientific and Technical Information of China (English)

    WANG Weining; YUE Weiwei; YAN Haitao; ZHANG Cunlin; ZHAO Guozhong

    2005-01-01

    The optical characteristics of four kinds of amino acids (tyrosine, arginine, histidine and glutamine) filled with nitrogen at room temperature were studied by THz time-domain spectroscopy (THz-TDS). Well-resolved absorption and refractive spectrums between 0.1 and 2.8 THz were obtained based on the physical model for extracting the optical parameters of materials in THz range. The results not only fill up the spectra gap of amino acids in far-infrared range, supply data for amino acid molecular identification and conformation analysis, but also demonstrate significantly potential to promote the research and application of biological materials in bio-chemical and medical fields by THz-TDS.

  20. Design and Fabrication of a 1 THz Backward Wave Amplifier

    DEFF Research Database (Denmark)

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

    2011-01-01

    The THz frequency range represents a true challenge for designers, fabrication technologies and characterization systems. So far, huge technological obstacles have prohibited any system realization different from laboratory one. Furthermore, most of the applications in the THz frequency range...... require a level of power not achievable by optoelectronic devices at room temperature or by solid-state technology. The recent availability of three-dimensional simulators and high aspect ratio micro-fabrication techniques has stimulated a class of vacuum electron devices operating in the THz regime......, 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...

  1. Fizeau Interferometery for THz-Waves' Frequency and Intensity Measurement

    Institute of Scientific and Technical Information of China (English)

    SIDDIQUE Muhammad; YANG Su-hui; LI Zhuo; LI Ping

    2007-01-01

    A terahertz-wave generator based on optical parametric oscillator principle, detection based on combination of Fizeau wedged interferometer and an electro-optical crystal ZnTe has been studied. The analytical solution based on the basic principle of operation of solid wedge Fizeau interferometer has been realized. The mathematical calculations for THz frequency and intensity measurement dependent on wedge angle and fringe spacing have been considered. The efficiency of THz wave detection depends upon optimized wedge angle has been also realized. The feasibility of detection of THz waves' frequency and intensity by solid Fizeau interferometer (THz-waves' range of 1-3THz) has been studied. By optimization of other parameters like thickness of Fizeau film, refractive index, material of Fizeau film, we can proceed towards the design of Fizeau interferometer for required research plans as it is a simple and inexpensive interferometer.

  2. Broadband Radio Service (BRS) and Educational Broadband Service (EBS) Transmitters

    Data.gov (United States)

    Department of Homeland Security — The Broadband Radio Service (BRS), formerly known as the Multipoint Distribution Service (MDS)/Multichannel Multipoint Distribution Service (MMDS), is a commercial...

  3. Colloidal superlattices for unnaturally high-index metamaterials at broadband optical frequencies

    CERN Document Server

    Lee, Seungwoo

    2015-01-01

    The recent advance in the assembly of metallic nanoparticles (NPs) has enabled sophisticated engineering of unprecedented light-matter interaction at the optical domain. In this work, I expand the design flexibility of NP optical metamaterial to push the upper limit of accessible refractive index to the unnaturally high regime. The precise control over the geometrical parameters of NP superlattice monolayer conferred the dramatic increase in electric resonance and related effective permittivity far beyond the naturally accessible regime. Simultaneously, effective permeability, another key factor to achieving high refractive index, was effectively suppressed by reducing the thickness of NPs. By establishing this design rule, I have achieved unnaturally high refractive index (15.7 at the electric resonance and 7.3 at the quasi-static limit) at broadband optical frequencies (100 THz ~ 300 THz). I also combined this NP metamaterial with graphene to electrically control the high refractive index over the broad opt...

  4. Proton implanted sapphire planar and channel waveguides

    NARCIS (Netherlands)

    Laversenne, L.; Crunteanu, A.; Hoffmann, P.; Pollnau, M.; Moretti, P.; Mugnier, J.

    2003-01-01

    We report low-order transverse-mode planar waveguides in sapphire fabricated for the first time by proton implantation. The waveguides show good guiding properties without post-implantation annealing. Channel waveguiding was achieved by polyimide strip-loading.

  5. Miniaturized dielectric waveguide filters

    Science.gov (United States)

    Sandhu, Muhammad Y.; Hunter, Ian C.

    2016-10-01

    Design techniques for a new class of integrated monolithic high-permittivity ceramic waveguide filters are presented. These filters enable a size reduction of 50% compared to air-filled transverse electromagnetic filters with the same unloaded Q-factor. Designs for Chebyshev and asymmetric generalised Chebyshev filter and a diplexer are presented with experimental results for an 1800 MHz Chebyshev filter and a 1700 MHz generalised Chebyshev filter showing excellent agreement with theory.

  6. 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

  7. Spectrally engineered broadband photon source for two-photon quantum interferometry

    CERN Document Server

    Thomas, Abu; Minaeva, Olga; Simon, David; Sergienko, Alexander V

    2016-01-01

    We present a new approach to engineering broadband sources of entangled photon pairs for quantum interferometry. The source is based on quasi-phase-matched spontaneous parametric down conversion in a titanium diffused periodically poled lithium niobate waveguide with a strongly-chirped poling period. The proposed non-standard asymmetric poling mitigates phase distortions associated with the process of chirping. Asymmetric poling significantly broadens the entangled source bandwidth while preserving high visibility quantum interferometric sensing.

  8. 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

  9. Fixed-Tuned Waveguide 0.6 THz SIS Mixer with Wide Band IF

    NARCIS (Netherlands)

    Baryshev, A.; Lauria, E.; Hesper, R.; Zijistra, T.; Wild, W.

    2002-01-01

    The Atacama Large Millimeter Array (ALMA) requires low noise SIS receivers for frequencies from about 80 GHz to 950 GHz with a very large IF bandwidth (8 GHz SSB upper or lower sideband, 8 GHz DSB or 4 GHz dual sideband, upper and lower sideband). Since there will be a large number of antennas in th

  10. Broadband frequency conversion

    DEFF Research Database (Denmark)

    Sanders, Nicolai; Jensen, Ole Bjarlin; Tidemand-Lichtenberg, Peter;

    We present a simple, passive and static setup for broadband frequency conversion. By using simple optical components like lenses, mirrors and gratings, we obtain the spectral angular dispersion to match the second harmonic generation phasematching angles in a nonlinear BiBO crystal. We are able to...... frequency double a single-frequency diode laser, tunable in the 1020-1090 nm range, with almost equal efficiency for all wavelengths. In the experimental setup, the width of the phasematch was increased with a factor of 50. The method can easily be extended to other wavelength ranges and nonlinear crystals...

  11. Fabrication and characterization of fiber optical components for application in guiding, sensing and molding of THz and mid-IR radiation

    Science.gov (United States)

    Mazhorova, Anna

    The terahertz (THz) range refers to electromagnetic waves with frequencies between 100 GHz and 10 THz, or wavelengths between 3 mm and 30 µm. Light between radio waves and infrared has some unique properties. Within the scope of this work I would like to address three main research topics. In Chapter 2, I describe fabrication method and THz characterization of composite films containing either aligned metallic (tin alloy) microwires or chalcogenide As2Se3 microwires. The microwire arrays are made by stack-and-draw fiber fabrication technique using multi-step co-drawing of low-melting-temperature metals or semiconductor glasses together with polymers. Fibers are then stacked together and pressed into composite films. Transmission through metamaterial films is studied in the whole THz range (0.1-20 THz) using a combination of FTIR and TDS. Metal containing metamaterials are found to have strong polarizing properties, while semiconductor containing materials are polarization independent and could have a designable high refractive index. Using the transfer matrix theory, it was shown how to retrieve the complex polarization dependent refractive index of the composite films. We then detail the selfconsistent algorithm for retrieving the optical properties of the metal alloy used in the fabrication of the metamaterial layers by using an effective medium approximation. Finally, we study challenges in fabrication of metamaterials with sub-micrometer metallic wires by repeated stack-and-draw process by comparing samples made using 2, 3 and 4 consecutive drawings. When using metallic alloys we observe phase separation effects and nano-grids formation on small metallic wires. In Chapter 3, we have studied fabrication and bacteria detection application of the lowloss subwavelength THz microstructured fibers. One of the key difficulties in the design of terahertz waveguides lies in the fact that almost all materials are highly absorbing in the terahertz region. Since the

  12. 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...

  13. 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.)

  14. 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 < .01) ranging between 0.0209 - 0.038% (reflectivity: %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.

  15. Broadband pendulum energy harvester

    Science.gov (United States)

    Liang, Changwei; Wu, You; Zuo, Lei

    2016-09-01

    A novel electromagnetic pendulum energy harvester with mechanical motion rectifier (MMR) is proposed and investigated in this paper. MMR is a mechanism which rectifies the bidirectional swing motion of the pendulum into unidirectional rotation of the generator by using two one-way clutches in the gear system. In this paper, two prototypes of pendulum energy harvester with MMR and without MMR are designed and fabricated. The dynamic model of the proposed MMR pendulum energy harvester is established by considering the engagement and disengagement of the one way clutches. The simulation results show that the proposed MMR pendulum energy harvester has a larger output power at high frequencies comparing with non-MMR pendulum energy harvester which benefits from the disengagement of one-way clutch during pendulum vibration. Moreover, the proposed MMR pendulum energy harvester is broadband compare with non-MMR pendulum energy harvester, especially when the equivalent inertia is large. An experiment is also conducted to compare the energy harvesting performance of these two prototypes. A flywheel is attached at the end of the generator to make the disengagement more significant. The experiment results also verify that MMR pendulum energy harvester is broadband and has a larger output power at high frequency over the non-MMR pendulum energy harvester.

  16. Subwavelength imaging of sparse broadband sources surrounded by an open disordered medium from a single antenna

    CERN Document Server

    Li, Lianlin; Cui, Tie Jun

    2014-01-01

    In this letter we study the subwavelength imaging of sparse broadband sources inside a disordered medium by processing the data acquired by a single antenna. A mathematical model has been developed for solving such problem based on the idea of sparse reconstruction. We show that the strongly disordered medium can serves as an efficient apparatus for compressive measurement, which shifts the complexity of devising compressive sensing (CS) hardware from the design, fabrication and electronic control. The proposed method and associated results can find applications in several imaging disciplines, such as optics, THz, RF or ultrasound imaging.

  17. Realization of Tapered Waveguide by Stretching the Rod Waveguide

    Institute of Scientific and Technical Information of China (English)

    XIA Ke-yu; YU Rong-jin; MENG Hua-mao

    2004-01-01

    By stretching the rod waveguide with different velocities in opposite directions,the tapered waveguide can be fabricated.In condition of taking no account of volume expansion caused by heating and under the assumptions of volume conservation,the rod waveguide can be stretched freely in the heated region without being stretched outside of the heated region. A model,which shows the relation of the transition shape and the two factors,that is the ratio of two velocity and the heated region length,is presented for the shape of the taper transition through mathematic deduction.Based on this model,a desired tapered waveguide can be fabricated.The tapered waveguide are widely used for fabricating tapered fiber couplers and sensors.In addition,the conclusion can be used for fabricating fused fiber coupler.

  18. Slab waveguide theory for general multi-slot waveguide

    Science.gov (United States)

    Le, ZiChun; Yin, LiXiang; Zou, Yu; Wu, Xiang

    2016-07-01

    Optical devices based on slot waveguide are of considerable interest in numerous applications due to the distinct feature of strong electric field confinement in a low-refractive index region. A theoretical model based on multi-slab waveguide theory is used to reveal the physical mechanism of the slot waveguide. The calculation results derived from the basic Helmholtz equation for the conventional single-slot waveguide with a ~2% validation of the effective refractive index are compared to the former experiment results by the Cornell University group. Moreover, we extend the theoretical model to a general multi-slot waveguide. Its electric field distribution and key properties such as optical power confinement factor and enhancement factor in slot are deduced theoretically and fully discussed.

  19. Two-Dimensional Fractal Metamaterials for Applications in THz

    DEFF Research Database (Denmark)

    Malureanu, Radu; Jepsen, Peter Uhd; Zalkovskij, Maksim;

    2011-01-01

    The concept of metamaterials (MTMs) is acknowledged for providing new horizons for controlling electromagnetic radiations thus their use in frequency ranges otherwise difficult to manage (e.g. THz radiation) broadens our possibility to better understand our world as well as opens the path for new...... 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 1 THz for TE polarized light while the TM waves have almost 80% field...

  20. Optically-electrically pumped THz source

    Science.gov (United States)

    Haji-Saeed, Bahareh; Khoury, Jed; Buchwald, Walter; Woods, Charles; Wentzell, Sandra; Krejca, Brian; Kierstead, John

    2010-08-01

    In this paper, we propose a design for a widely tunable solid-state optically and electrically pumped THz source based on the Smith-Purcell free-electron laser. Our design consists of a thin dielectric layer sandwiched between an upper corrugated structure and a lower layer of thin metal, semiconductor, or high electron mobility material. The lower layer is for current streaming, which replaces the electron beam in the Smith-Purcell free-electron laser design. The upper layer consists of two micro-gratings for optical pumping, and a nano-grating to couple with electrical pumping in the lower layer. The optically generated surface plasmon waves from the upper layer and the electrically induced surface plasmon waves from the lower layer are then coupled. Emission enhancement occurs when the plasmonic waves in both layers are resonantly coupled.

  1. One THz. Beamed Energy - Mission Capabilities

    Science.gov (United States)

    Johansen, Donald G.

    2005-04-01

    Gyrotrons now used for nuclear fusion experiments are a possibile source for beamed energy electro-thermal propulsion. Water vapor absorption is likely to bar 1 THz. transmission through the atmosphere. A space-based source in low equatorial orbit offers beamed energy velocity increments for upper stage orbit insertion. Transfer orbits to geosynchronous and lunar destinations and escape velocities to Mars and Venus are considered. Rapid acceleration (1 g) at high specific impulse implies very high source power and mass. Altitudes for BEP source satellites are in 600 to 800 kilometer range, set by atmospheric drag and avoidance of van Allen belt. Earth oblateness plus lunar and solar tidal forces are important factors governing source orbit selection and maintenance.

  2. Perspective: Ultrafast magnetism and THz spintronics

    Science.gov (United States)

    Walowski, Jakob; Münzenberg, Markus

    2016-10-01

    This year the discovery of femtosecond demagnetization by laser pulses is 20 years old. For the first time, this milestone work by Bigot and coworkers gave insight directly into the time scales of microscopic interactions that connect the spin and electron system. While intense discussions in the field were fueled by the complexity of the processes in the past, it now became evident that it is a puzzle of many different parts. Rather than providing an overview that has been presented in previous reviews on ultrafast processes in ferromagnets, this perspective will show that with our current depth of knowledge the first applications are developed: THz spintronics and all-optical spin manipulation are becoming more and more feasible. The aim of this perspective is to point out where we can connect the different puzzle pieces of understanding gathered over 20 years to develop novel applications. Based on many observations in a large number of experiments. Differences in the theoretical models arise from the localized and delocalized nature of ferromagnetism. Transport effects are intrinsically non-local in spintronic devices and at interfaces. We review the need for multiscale modeling to address the processes starting from electronic excitation of the spin system on the picometer length scale and sub-femtosecond time scale, to spin wave generation, and towards the modeling of ultrafast phase transitions that altogether determine the response time of the ferromagnetic system. Today, our current understanding gives rise to the first usage of ultrafast spin physics for ultrafast magnetism control: THz spintronic devices. This makes the field of ultrafast spin-dynamics an emerging topic open for many researchers right now.

  3. 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.

  4. 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

    2016-01-01

    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. PMID:26861341

  5. 2D THz and GHz signature for identification of explosive on reflected THz signal

    Science.gov (United States)

    Trofimov, Vyacheslav A.; Varentsova, Svetlana A.; Chen, Jian

    2010-11-01

    The method of THz spectrum dynamics analysis (SDA - Spectral dynamics analysis - method) is applied for the detection and identification of substances by using the signal reflected from sample. It allows to obtain the spectrogram - composite Fourier spectrum dynamics - of the signal and to analyze the dynamics of many spectral lines simultaneously, even if the measurements are made on short time interval (less than 50 ps). The efficiency of the SDA method used for longer time intervals (more than 100 ps) is discussed also. The Fourier-Gabor sliding window method is used for obtaining the spectrogram. We consider the examples of finding the pure RDX and harmless materials (L-Tartaric Acid, Sucrose, PTFE) or their mixture in pellets by using a THz pulse reflected from them. A THz pulse with a few cycles falls on the sample and reflects from it. The receiver makes the discrete measurements of electric field strength of signal reflected from the sample. To restore the signal to the required accuracy the SVD - Single Value Decomposition - technique is used. Our investigations show that the spectrograms and dynamics of several spectral lines of the THz pulse reflected differ from the corresponding spectrograms and dynamics of spectral lines for the reference pulse under certain conditions and hence it is possible to detect the presence of the material in the sample of interest. The comparison of the Fourier spectrum of the substance with the corresponding spectrum calculated on the base of using an autocorrelation function for obtaining the spectrum shows that the AC-spectrum gives us essential less information about substance. From our consideration follows that in some cases the analysis of reflected signal on the short time interval (less than 50 ps) is insufficient for the reliable identification. It is necessary to analyze the response on the long time interval (about 300 - 400 ps). The analysis of spectrogram and spectral lines dynamics on the long time intervals

  6. Design of Pass Band Filter in Hybrid Architecture Planar/Non-Radiative Dielectric Waveguide Integration Technology

    Directory of Open Access Journals (Sweden)

    Harizi Hanen

    2012-01-01

    Full Text Available Problem statement: The expansion of RF, microwave and millimeter devices has revolutionized today’s ommunication and sensor systems. Low-cost, high-performance and mass producible millimeter wave technologies are vital for commercial broadband systems. Challenging issues are commonly faced in the design of low-loss integrated circuits for example high-Q band pass filter, which the planar technique is fundamentally limited in performance. Approach: In this study, we present a design of a nonradiative dielectric waveguide band pass filter based on hybrid architecture of micro strip line and non-radiative dielectric waveguide. Results: The simulation with High Frequency Structure Simulator (HFSS three dimensional analyses is presented. Conclusion: The non radiative dielectric resolves most of the drawbacks of dielectric waveguide in connection with the radiation loss."

  7. THz time-domain spectroscopy imaging for mail inspection

    Science.gov (United States)

    Zhang, Liquan; Wang, Zhongdong; Ma, Yanmei; Hao, Erjuan

    2011-08-01

    Acquiring messages from the mail but not destroying the envelope is a big challenge in the war of intelligence. If one can read the message of the mail when the envelope is closed, he will benefit from the message asymmetry and be on a good wicket in the competition. In this paper, we presented a transmitted imaging system using THz time-domain spectroscopy technology. We applied the system to image the mail inside an envelope by step-scanning imaging technology. The experimental results show that the THz spectroscopy can image the mail in an envelope. The words in the paper can be identified easily from the background. We also present the THz image of a metal blade in the envelope, in which we can see the metal blade clearly. The results show that it is feasible of THz Time-Domain Spectroscopy Imaging for mail inspection applications.

  8. THz SPECTROSCOPY AND NANOSTRUCTURES: A SHORT INTERESTING REVIEW

    Directory of Open Access Journals (Sweden)

    Paolo Di Sia

    2012-03-01

    Full Text Available I present a short detailed interesting review regarding importance and results of THz spectroscopy in studying nanostructures, in particular in relation to the most studied materials at today.

  9. Ultrafast two-dimensional THz spectroscopy of graphene

    Directory of Open Access Journals (Sweden)

    Woerner M.

    2013-03-01

    Full Text Available With two-dimensional THz spectroscopy the dynamics of low-energy carriers in graphene is determined. Both intra- and interband absorption contribute to the observed ultrafast pump-probe signals.

  10. LBO: optical properties and potential for THz application

    Science.gov (United States)

    Andreev, Yu M.; Naftaly, M.; Molloy, J. F.; Kokh, A. E.; Lanskii, G. V.; Svetlichnyi, V. A.; Losev, V. F.; Kononova, N. G.; Kokh, K. A.

    2015-11-01

    High quality lithium borate (LBO) samples cut along (1 0 0), (0 1 0) and (0 0 1) axes were studied by terahertz time-domain spectroscopy (THz TDS) between 0.2-3 THz. It was found that in the direction of crystallographic axis X the optical absorption coefficient is the lowest amongst all known anisotropic nonlinear crystals, and that birefringence is as large as 0.42. Dispersion equations for the entire transparency range of LBO were developed for the first time. Phase matching for down-conversion into the THz range was found to be possible. Phase matching availability, low optical loss in the transparency band, and high optical damage threshold make LBO one of the most promising nonlinear materials for THz generation.

  11. Modelling, fabrication and characterisation of THz fractal meta-materials

    DEFF Research Database (Denmark)

    Xiao, S.; Zhou, L.; Malureanu, Radu;

    2011-01-01

    We present theoretical predictions, fabrication procedure and characterisation results of fractal metamaterials for the THz frequency range. The characterisation results match well the predicted response thus validating both the fabrication procedure as well as the simulation one. Such systems sh...

  12. Ballistic deflection transistors and their application to THz amplification

    Science.gov (United States)

    Margala, M.; Wu, H.; Sobolewski, Roman

    2015-10-01

    We present implementation of recently proposed ballistic deflection transistors (BDTs) as THz amplifiers. BDT is a planar device based on InGaAs/InAlAs/InP heterostructure with quasi-ballistic transport obtained in the two-dimensional electron gas layer that facilitates ultra-short transit time and high performance needed for THz-range circuitry. The BDT performance is optimized through its structural modification and the use of high-k dielectrics. Our time-domain, electrical transient measurements demonstrate sub-THz switching performance of a BDT with a ∼1-μm-wide channel. Independently, circuit simulations using experimental parameters of BDTs with a channel width of 430 nm and with the BDTs themselves connected as a multi-stage travelling-wave amplifier, designed for 6-dB gain, predict a 2.7- THz bandwidth with a gain flatness of ±0.3 dB.

  13. Nano-Antenna For Terahertz (THz) Medical Imaging Applications Project

    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...

  14. Metasurface Broadband Solar Absorber

    CERN Document Server

    Azad, A K; Sykora, M; Weisse-Bernstein, N R; Luk, T S; Taylor, A J; Dalvit, D A R; Chen, H -T

    2015-01-01

    We demonstrate a broadband, polarization independent, omnidirectional absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low emissivity at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. Furthermore, we discuss the potential use of our metasurface absorber design in solar thermophotovoltaics by exploiting refractory plasmonic materials.

  15. Metasurface Broadband Solar Absorber

    Science.gov (United States)

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-02-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure.

  16. Metamaterial Broadband Angular Selectivity

    CERN Document Server

    Shen, Yichen; Wang, Zhiyu; Wang, Li; Celanovic, Ivan; Ran, Lixin; Joannopoulos, John D; Soljacic, Marin

    2014-01-01

    We demonstrate how broadband angular selectivity can be achieved with stacks of one-dimensionally periodic photonic crystals, each consisting of alternating isotropic layers and effective anisotropic layers, where each effective anisotropic layer is constructed from a multilayered metamaterial. We show that by simply changing the structure of the metamaterials, the selective angle can be tuned to a broad range of angles; and, by increasing the number of stacks, the angular transmission window can be made as narrow as desired. As a proof of principle, we realize the idea experimentally in the microwave regime. The angular selectivity and tunability we report here can have various applications such as in directional control of electromagnetic emitters and detectors.

  17. Metasurface Broadband Solar Absorber.

    Science.gov (United States)

    Azad, Abul K; Kort-Kamp, Wilton J M; Sykora, Milan; Weisse-Bernstein, Nina R; Luk, Ting S; Taylor, Antoinette J; Dalvit, Diego A R; Chen, Hou-Tong

    2016-01-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999

  18. A Study of Tunable Metamaterial Devices for the THz Region

    Science.gov (United States)

    Chikhi, N.; Di Gennaro, E.; Esposito, E.; Andreone, A.

    In order to cope with the "THz Gap", metamaterial based devices operating at about 1 THz have been designed to have a tunable response. We studied the electromagnetic behaviour of periodic structures consisting of different "unit cells" based on the concept of Split Ring Resonator (SRR). The devices response in the required frequency region is simulated using a commercial electromagnetic code. Different modulation mechanisms have been investigated, including the use of liquid crystals, MEMS, semiconducting substrates.

  19. 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....

  20. Infrared nanoantenna couplers for plasmonic slot waveguide

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei

    A slot plasmonic waveguide is promising solution as a replacement of electrical interconnects in the future optical integrated circuits. In this contribution we consider a set of compact solutions for coupling the infrared light from free space to the plasmonic slot waveguide. We systematically...... study various designs: dipole antennas outside the waveguide, antennas inside the waveguide and bow-tie antennas in the slots....

  1. Nonlinear Femtosecond Pulse Reshaping in Waveguide Arrays

    OpenAIRE

    Darren D. Hudson; Shish, Kimberlee; Schibli, Thomas R.; Kutz, J. Nathan; Christodoulides, Demetrios N.; Morandotti, Roberto; Cundiff, Steven T.

    2008-01-01

    We observe nonlinear pulse reshaping of femtosecond pulses in a waveguide array due to coupling between waveguides. Amplified pulses from a mode-locked fiber laser are coupled to an AlGaAs core waveguide array structure. The observed power-dependent pulse reshaping agrees with theory, including shortening of the pulse in the central waveguide.

  2. Design and applications of THz metamaterials and metasurfaces%太赫兹超材料和超表面器件的研发与应用

    Institute of Scientific and Technical Information of China (English)

    王波; 张岩

    2015-01-01

    Terahertz(THz) optoelectronics has promoted the development of the THz generation, transparent control, and detection methods,and hastened many devices in the past decades. Especially, THz metamaterials and metasurfaces will exhibit extraordinary electromagnetic response when the subwavelength scale metal structure is excited by the THz illumination. Therefore, they have been applied to the devices such as wave beam shaper, waveguide, and modulator etc. The THz metamaterials and metasurfaces also show the potential applications in the research fields such as sensors, communications, and radars. In this paper, the works about the spectrum and wavefront modulation with THz metadevices carried out in our group are summarized. The basic theory and corresponding experiment results for different devices are introduced. It is expected these works can pave the avenue of the application of the THz metadevices.%太赫兹光电子学的兴起推动了太赫兹波产生、传输和探测3方面理论和器件的快速发展。通过调控亚波长金属结构与太赫兹波相互作用的特异光学响应,太赫兹超材料和超表面器件已在太赫兹光束整形、导波和调制方面显示了巨大的潜力和优势,并可能推动太赫兹光源和探测器的发展。进一步发展和丰富太赫兹超材料和超表面器件,也将对太赫兹波在传感、通信和雷达等应用方面产生有益影响。本文综述了首都师范大学超材料与器件课题组近年来在太赫兹波段开展的基于超材料和超表面材料的光谱调制器件、光场调制衍射光学元件和主动光学元件的工作,介绍了超材料与器件的基本物理理论以及相应的实验研究成果,希望能够推动超材料与超表面太赫兹调制器件的发展与应用。

  3. Theoretical and Experimental studies on CH{sub 3}OH THz Laser Pumped by Pulse Carbon Dioxide Laser

    Energy Technology Data Exchange (ETDEWEB)

    Fei Fei; Wang Jing; Tian Zhaoshuo; Zhang Yanchao; Fu Shiyou; Wang Qi, E-mail: tianzhaoshuo@126.com [Information Optoelectronics Research Institute, Harbin Institute of Technology at Weihai, Sandong, Weihai, 264209 (China)

    2011-02-01

    In this paper, according to the molecular structure and vibration mode of micro-asymmetric gyroscope CH{sub 3}OH molecule, dynamic process of optically pumped Terahertz laser is analyzed theoretically. The rate equation models based on three level systems are given according to the theory of typical laser rate equation. The output THz pulsed laser waveform is obtained by solving the rate equation model. An all-metal Terahertz laser pumped by RF waveguide carbon dioxide laser is designed with CH{sub 3}OH as its working gas. The pulsed Terahertz laser output is obtained. The waveform and repetition frequency of the optically pumped laser are measured in the experiments. The Terahertz laser designed does not need water cooling system. It also has the advantages of simple structure and small size.

  4. The physical theory and propagation model of THz atmospheric propagation

    Science.gov (United States)

    Wang, R.; Yao, J. Q.; Xu, D. G.; Wang, J. L.; Wang, P.

    2011-02-01

    Terahertz (THz) radiation is extensively applied in diverse fields, such as space communication, Earth environment observation, atmosphere science, remote sensing and so on. And the research on propagation features of THz wave in the atmosphere becomes more and more important. This paper firstly illuminates the advantages and outlook of THz in space technology. Then it introduces the theoretical framework of THz atmospheric propagation, including some fundamental physical concepts and processes. The attenuation effect (especially the absorption of water vapor), the scattering of aerosol particles and the effect of turbulent flow mainly influence THz atmosphere propagation. Fundamental physical laws are illuminated as well, such as Lamber-beer law, Mie scattering theory and radiative transfer equation. The last part comprises the demonstration and comparison of THz atmosphere propagation models like Moliere(V5), SARTre and AMATERASU. The essential problems are the deep analysis of physical mechanism of this process, the construction of atmospheric propagation model and databases of every kind of material in the atmosphere, and the standardization of measurement procedures.

  5. Low-noise THz MgB2 Josephson mixer

    Science.gov (United States)

    Cunnane, Daniel; Kawamura, Jonathan H.; Acharya, Narendra; Wolak, Matthäus A.; Xi, X. X.; Karasik, Boris S.

    2016-09-01

    The potential applications for high frequency operation of the Josephson effect in MgB2 include THz mixers, direct detectors, and digital circuits. Here we report on MgB2 weak links which exhibit the Josephson behavior up to almost 2 THz and using them for low-noise heterodyne detection of THz radiation. The devices are made from epitaxial film grown in the c-axis direction by the hybrid physical-chemical vapor deposition method. The current in the junctions travels parallel to the surface of the film, thus making possible a large contribution of the quasi-two-dimensional σ-gap in transport across the weak link. These devices are connected to a planar spiral antenna with a dielectric substrate lens to facilitate coupling to free-space radiation for use as a detector. The IcRn product of the junction is 5.25 mV, giving confirmation of a large gap parameter. The sensitivity of the mixer was measured from 0.6 THz to 1.9 THz. At a bath temperature of over 20 K, a mixer noise temperature less than 2000 K (DSB) was measured near 0.6 THz.

  6. Computational Investigations of THz Transmittance in the Atmosphere

    Science.gov (United States)

    Yang, Xingyu; Calhoun, Casey; Calhoun, Ronald

    2016-06-01

    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).

  7. 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.

  8. Near-field characterization of plasmonic waveguides

    DEFF Research Database (Denmark)

    Zenin, Volodymyr

    2014-01-01

    and their imaging techniques is included additionally to the main research of plasmonic waveguides (channel plasmon polariton, long-range dielectric-loaded surface plasmon polariton, and plasmonic slot waveguides) and waveguide components (antennas, S-bends, and directional couplers) included as a reprint of papers....... 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...

  9. Analysis of impact factors of output characteristics for optically pumped THz lasers

    Science.gov (United States)

    Huang, Renshuai; Meng, Qinglong; Guo, Xiaoyang; Zhang, Bin

    2016-08-01

    Optically pumped terahertz (THz) lasers as a reliable THz radiation sources have been widely used in THz application area. Considering the Doppler-broadened effects and the two-photon light shift effects, the physical model for the THz output power and the THz output frequency drift of optically pumped THz lasers has been established based on the rate equations. The main factors affecting THz laser output have been analyzed quantitatively. The results indicate that the THz output power increases with the increasing of the pump power, while decreases with the increasing of the pump frequency offset from the operating gas absorption centre. The THz output frequency drift is mainly caused by two-photon light shift when the pump offset is small, whereas Doppler-broadened becomes main factor if the pump frequency offset is relatively larger. Furthermore, the THz output frequency drift increases in proportion to the pump power. The stability of the THz output frequency can be enhanced and the THz output power can be improved by choosing pressure in the cavity reasonably, and the optimal working gas pressure range is 15-20 Pa. Stabilizing the pump laser frequency in the range of gas absorption centre, choosing reasonable working gas pressure in the THz cavity and the pump power can efficiently improve the performance of the THz laser output.

  10. Resonant THz sensor for paper quality monitoring using THz fiber Bragg gratings

    CERN Document Server

    Yan, Guofeng; Mikulic, Predrag; Bock, Wojtek J; Skorobogatiy, Maksim

    2013-01-01

    We report fabrication of THz fiber Bragg gratings (TFBG) using CO2 laser inscription on subwavelength step-index polymer fibers. A fiber Bragg grating with 48 periods features a ~4 GHz-wide stop band and ~15 dB transmission loss in the middle of a stop band. The potential of such gratings in design of resonant sensor for monitoring of paper quality is demonstrated. Experimental spectral sensitivity of the TFBG-based paper thickness sensor was found to be ~ -0.67 GHz / 10 um. A 3D electromagnetic model of a Bragg grating was used to explain experimental findings.

  11. Grating-Coupled Waveguide Cloaking

    Institute of Scientific and Technical Information of China (English)

    WANG Jia-Fu; QU Shao-Bo; XU Zhuo; MA Hua; WANG Cong-Min; XIA Song; WANG Xin-Hua; ZHOU Hang

    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.

  12. Hollow waveguide for urology treatment

    Science.gov (United States)

    Jelínková, H.; Němec, M.; Koranda, P.; Pokorný, J.; Kőhler, O.; Drlík, P.; Miyagi, M.; Iwai, K.; Matsuura, Y.

    2010-02-01

    The aim of our work was the application of the special sealed hollow waveguide system for the urology treatment - In our experimental study we have compared the effects of Ho:YAG (wavelength 2100 nm) and Er:YAG (wavelength 2940 nm) laser radiation both on human urinary stones (or compressed plaster samples which serve as a model) fragmentation and soft ureter tissue incision in vitro. Cyclic Olefin Polymer - coated silver (COP/Ag) hollow glass waveguides with inner and outer diameters 700 and 850 μm, respectively, were used for the experiment. To prevent any liquid to diminish and stop the transmission, the waveguide termination was utilized.

  13. Broadband Advanced Spectral System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NovaSol proposes to develop an advanced hyperspectral imaging system for earth science missions named BRASS (Broadband Advanced Spectral System). BRASS combines...

  14. Generation of broadband spontaneous parametric fluorescence using multiple bulk nonlinear crystals

    CERN Document Server

    Okano, Masayuki; Tanaka, Akira; Subashchandran, Shanthi; Takeuchi, Shigeki; 10.1364/OE.20.013977

    2012-01-01

    We propose a novel method for generating broadband spontaneous parametric fluorescence by using a set of bulk nonlinear crystals (NLCs). We also demonstrate this scheme experimentally. Our method employs a superposition of spontaneous parametric fluorescence spectra generated using multiple bulk NLCs. A typical bandwidth of 160 nm (73 THz) with a degenerate wavelength of 808 nm was achieved using two beta-barium-borate (BBO) crystals, whereas a typical bandwidth of 75 nm (34 THz) was realized using a single BBO crystal. We also observed coincidence counts of generated photon pairs in a non-collinear configuration. The bandwidth could be further broadened by increasing the number of NLCs. Our demonstration suggests that a set of four BBO crystals could realize a bandwidth of approximately 215 nm (100 THz).We also discuss the stability of Hong-Ou-Mandel two-photon interference between the parametric fluorescence generated by this scheme. Our simple scheme is easy to implement with conventional NLCs and does not...

  15. Generation of broadband spontaneous parametric fluorescence using multiple bulk nonlinear crystals.

    Science.gov (United States)

    Okano, Masayuki; Okamoto, Ryo; Tanaka, Akira; Subashchandran, Shanthi; Takeuchi, Shigeki

    2012-06-18

    We propose a novel method for generating broadband spontaneous parametric fluorescence by using a set of bulk nonlinear crystals (NLCs). We also demonstrate this scheme experimentally. Our method employs a superposition of spontaneous parametric fluorescence spectra generated using multiple bulk NLCs. A typical bandwidth of 160 nm (73 THz) with a degenerate wavelength of 808 nm was achieved using two β-barium-borate (BBO) crystals, whereas a typical bandwidth of 75 nm (34 THz) was realized using a single BBO crystal. We also observed coincidence counts of generated photon pairs in a non-collinear configuration. The bandwidth could be further broadened by increasing the number of NLCs. Our demonstration suggests that a set of four BBO crystals could realize a bandwidth of approximately 215 nm (100 THz). We also discuss the stability of Hong-Ou-Mandel two-photon interference between the parametric fluorescence generated by this scheme. Our simple scheme is easy to implement with conventional NLCs and does not require special devices.

  16. Generation of broadband spontaneous parametric fluorescence using multiple bulk nonlinear crystals.

    Science.gov (United States)

    Okano, Masayuki; Okamoto, Ryo; Tanaka, Akira; Subashchandran, Shanthi; Takeuchi, Shigeki

    2012-06-18

    We propose a novel method for generating broadband spontaneous parametric fluorescence by using a set of bulk nonlinear crystals (NLCs). We also demonstrate this scheme experimentally. Our method employs a superposition of spontaneous parametric fluorescence spectra generated using multiple bulk NLCs. A typical bandwidth of 160 nm (73 THz) with a degenerate wavelength of 808 nm was achieved using two β-barium-borate (BBO) crystals, whereas a typical bandwidth of 75 nm (34 THz) was realized using a single BBO crystal. We also observed coincidence counts of generated photon pairs in a non-collinear configuration. The bandwidth could be further broadened by increasing the number of NLCs. Our demonstration suggests that a set of four BBO crystals could realize a bandwidth of approximately 215 nm (100 THz). We also discuss the stability of Hong-Ou-Mandel two-photon interference between the parametric fluorescence generated by this scheme. Our simple scheme is easy to implement with conventional NLCs and does not require special devices. PMID:22714463

  17. Grating THz laser with optical pumping

    Science.gov (United States)

    Khoury, Jed; Haji-saeed, Bahareh; Woods, Charles; Kierstead, John

    2010-04-01

    In this paper, we present a design for a widely tunable solid-state optically and electrically pumped THz laser based on the Smith-Purcell free-electron laser. In the free-electron laser, an energetic electron beam pumps a metallic grating to generate surface plasmons. Our solid-state optically pumped design consists of a thin layer of dielectic, such as SiNx, sandwiched between a corrugated structure and a thin metal or semiconductor layer. The lower layer is for current streaming, and replaces the electron beam in the original design. The upper layer consists of one micro-grating for coupling the electromagnetic field in, another for coupling out, and a nano-grating for coupling with the current in the lower layer for electromagnetic field generation. The surface plasmon waves generated from the upper layer by an external electromagnetic field, and the lower layer by the applied current, are coupled. Emission enhancement occurs when the plasmonic waves in both layers are resonantly coupled.

  18. Towards large area THz electromagnetic metamaterials

    Science.gov (United States)

    Moser, H. O.; Bahou, M.; Chen, A.; Heussler, S. P.; Jian, L. K.; Kalaiselvi, S. M. P.; Liu, G.; Maniam, S. M.; bin Mahmood, Shahrain; Gu, P. D.; Wen, L.; Kong, J. A.; Chen, H. S.; Cheng, X. X.; Wu, B. I.; Casse, B. D. F.; Rockstuhl, C.; Lederer, F.

    2008-08-01

    Up to date, electromagnetic metamaterials (EM3) have been mostly fabricated by primary pattern generation via electron beam or laser writer. Such an approach is time-consuming and may have limitations of the area filled with structures. Especially, electron beam written structures are typically confined to areas of a few 100×100 μm2. However, for meaningful technological applications, larger quantities of good quality materials are needed. Lithography, in particular X-ray deep lithography, is well suited to accomplish this task. Singapore Synchrotron Light Source (SSLS) has been applying its LIGA process that includes primary pattern generation via electron beam or laser writer, X-ray deep lithography and electroplating to the micro/nano-manufacturing of high-aspect ratio structures to produce a variety of EM3 structures. Starting with Pendry's split ring resonators, we have pursued structure designs suitable for planar lithography since 2002 covering a range of resonance frequencies from 1 to 216 THz. More recently, string-like structures have also been included. Latest progress made in the manufacturing and characterization of quasi 3D metamaterials having either split ring or string structures over areas of about ~1 cm2 extension will be described.

  19. THz Spectroscopy and Spectroscopic Database for Astrophysics

    Science.gov (United States)

    Pearson, John C.; Drouin, Brian J.

    2006-01-01

    Molecule specific astronomical observations rely on precisely determined laboratory molecular data for interpretation. The Herschel Heterodyne Instrument for Far Infrared, a suite of SOFIA instruments, and ALMA are each well placed to expose the limitations of available molecular physics data and spectral line catalogs. Herschel and SOFIA will observe in high spectral resolution over the entire far infrared range. Accurate data to previously unimagined frequencies including infrared ro-vibrational and ro-torsional bands will be required for interpretation of the observations. Planned ALMA observations with a very small beam will reveal weaker emission features requiring accurate knowledge of higher quantum numbers and additional vibrational states. Historically, laboratory spectroscopy has been at the front of submillimeter technology development, but now astronomical receivers have an enormous capability advantage. Additionally, rotational spectroscopy is a relatively mature field attracting little interest from students and funding agencies. Molecular data base maintenance is tedious and difficult to justify as research. This severely limits funding opportunities even though data bases require the same level of expertise as research. We report the application of some relatively new receiver technology into a simple solid state THz spectrometer that has the performance required to collect the laboratory data required by astronomical observations. Further detail on the lack of preparation for upcoming missions by the JPL spectral line catalog is given.

  20. Optical waveguide theory

    CERN Document Server

    Snyder, Allan W

    1983-01-01

    This text is intended to provide an in-depth, self-contained, treatment of optical waveguide theory. We have attempted to emphasize the underlying physical processes, stressing conceptual aspects, and have developed the mathematical analysis to parallel the physical intuition. We also provide comprehensive supplementary sections both to augment any deficiencies in mathematical background and to provide a self-consistent and rigorous mathematical approach. To assist in. understanding, each chapter con­ centrates principally on a single idea and is therefore comparatively short. Furthermore, over 150 problems with complete solutions are given to demonstrate applications of the theory. Accordingly, through simplicity of approach and numerous examples, this book is accessible to undergraduates. Many fundamental topics are presented here for the first time, but, more importantly, the material is brought together to give a unified treatment of basic ideas using the simplest approach possible. To achieve such a goa...

  1. Diamond nanobeam waveguide optomechanics

    CERN Document Server

    Khanaliloo, Behzad; Hryciw, Aaron C; Lake, David P; Kaviani, Hamidreza; Barclay, Paul E

    2015-01-01

    Optomechanical devices sensitively transduce and actuate motion of nanomechanical structures using light, and are central to many recent fundamental studies and technological advances. Single--crystal diamond promises to improve the performance of optomechanical devices, while also providing opportunities to interface nanomechanics with diamond color center spins and related quantum technologies. Here we demonstrate measurement of diamond nanobeam resonators with a sensitivity of 9.5 fm/Hz^0.5 and bandwidth >120 nm through dissipative waveguide--optomechanical coupling. Nanobeams are fabricated from bulk single--crystal diamond using a scalable quasi--isotropic oxygen plasma undercut etching process, and support mechanical resonances with quality factor of 2.5 x 10^5 at room temperature, and 7.2 x 10^5 in cryogenic conditions (5K). Mechanical self--oscillations, resulting from interplay between optomechanical coupling and the photothermal response of nanobeams in a buckled state, are observed with amplitude e...

  2. Investigation of a broadband refractory metal metamaterial absorber at terahertz frequencies.

    Science.gov (United States)

    Hu, Dan; Wang, Hongyan; Tang, Zhenjie; Zhang, Xiwei

    2016-07-01

    A broadband, polarization-independent, and wide-angle refractory metal metamaterial absorber is numerically investigated at terahertz frequencies, which consists of a periodic array of a chromium metallic loop and a chromium metallic film separated by a polyimide layer. Results show that a higher than 90% broadband absorption can be achieved for the range of frequencies from 1.00 through 2.43 THz, and the full absorption width at half-maximum can attain 110.80%, which is considerably larger than in previously reported results. Moreover, the greater than 90% broadband absorption response can still be maintained when the incidence angle increases to 45°. The physical origin of the proposed broadband absorber originates from localized surface plasmon resonances of the single metallic loop resonator. Furthermore, the designed concept also can be achieved in the visible and near-infrared region by rationally designing the dimensions of the absorber. This compact design has potential applications in stealth technology, energy harvesting, and thermal imaging. PMID:27409218

  3. Sensitivity Limits of Deep Average Broadband Microwave and Mm-Wave Spectra

    Science.gov (United States)

    Muckle, Matt T.; Zaleski, Daniel P.; Steber, Amanda; Harris, Brent; Pate, Brooks H.

    2012-06-01

    High-speed digitizers have enabled the field of broadband molecular rotational spectroscopy at microwave-to-THz frequencies. Improvements in data throughput from these digitizers makes it feasible to perform deep averages (often more than 1 million time-domain averages of the free induction decay) to increase the measurement sensitivity. The use of broadband signal detection introduces new issues that are key for determining the practical sensitivity limits of these spectrometers. The practical limit on spectrometer sensitivity is often set by the number of spurious signals that are generated by the molecular signals themselves. For example, in cases where the molecular signals are down converted prior to digitization, the spectral purity of the local oscillator is crucial with spurious frequencies introducing spectral images. It is also possible to generate new local oscillator frequencies within the broadband mixers typically used in the broadband down conversion. A second issue it the potential for a vast number of intermodulation (IM) spurious signals resulting from the beating of two strong molecular transitions. This beat frequency can subsequently modulate all other molecular signals adding sidebands to all transitions at the beat frequency of the transition pair. This talk will summarize our experience with the spurious signal levels coming from these effects and the strategies we have adopted to minimize spurious signals in spectra where high sensitivity is necessary.

  4. Heterogeneous broadband network

    Science.gov (United States)

    Dittmann, Lars

    1995-11-01

    Although the vision for the future Integrated Broadband Communication Network (IBCN) is an all optical network, it is certain that for a long period to come, the network will remain very heterogeneous, with a mixture of different physical media (fiber, coax and twisted pair), transmission systems (PDH, SDH, ADSL) and transport protocols (TCP/IP, AAL/ATM, frame relay). In the current work towards the IBCN, the ATM concept is considered the generic network protocol for both public and private network, with the ability to use different underlying transmission protocols and, through adaptation protocols, provide the appropriate services (old as well as new) to the customer. One of the major difficulties of heterogeneous network is the restriction that is usually given by the lowest common denominator, e.g. in terms of single channel capacity. A possible way to overcome these limitations is by extending the ATM concept with a multilink capability, that allows us to use separate resources as one common. The improved flexibility obtained by this protocol extension further allows a real time optimization of network and call configuration, without any impact on the quality of service seen from the user. This paper describes an example of an ATM based multilink protocol that has been experimentally implemented within the RACE project 'STRATOSPHERIC'. The paper outlines the complexity of introducing an extra network functionality compared with the added value, such as an improved ability to recover an error due to a malfunctioning network component.

  5. Broadband transmission EPR spectroscopy.

    Directory of Open Access Journals (Sweden)

    Wilfred R Hagen

    Full Text Available EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9-10 GHz range. Most (biomolecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin - nuclear spin interactions and electron spin - electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8-2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.

  6. Complete power concentration into a single waveguide in large-scale waveguide array lenses.

    Science.gov (United States)

    Catrysse, Peter B; Liu, Victor; Fan, Shanhui

    2014-10-16

    Waveguide array lenses are waveguide arrays that focus light incident on all waveguides at the input side into a small number of waveguides at the output side. Ideal waveguide array lenses provide complete (100%) power concentration of incident light into a single waveguide. While of great interest for several applications, ideal waveguide array lenses have not been demonstrated for practical arrays with large numbers of waveguides. The only waveguide arrays that have sufficient degrees of freedom to allow for the design of an ideal waveguide array lens are those where both the propagation constants of the individual waveguides and the coupling constants between the waveguides vary as a function of space. Here, we use state-of-the-art numerical methods to demonstrate complete power transfer into a single waveguide for waveguide array lenses with large numbers of waveguides. We verify this capability for more than a thousand waveguides using a spatial coupled mode theory. We hereby extend the state-of-art by more than two orders of magnitude. We also demonstrate for the first time a physical design for an ideal waveguide array lens. The design is based on an aperiodic metallic waveguide array and focuses ~100% of the incident light into a deep-subwavelength focal spot.

  7. Metal-clad waveguide sensors

    DEFF Research Database (Denmark)

    Skivesen, Nina

    This work concerns planar optical waveguide sensors for biosensing applications, with the focus on deep-probe sensing for micron-scale biological objects like bacteria and whole cells. In the last two decades planar metal-clad waveguides have been brieflyintroduced in the literature applied...... can only detect substances in the close vicinity to the sensor surface limited to below 200 nm. Bacteria andwhole cells with sizes of micron-scale exceed that range and thus sensors suitable for deepprobe sensing are important. The present thesis deals with optical, planer waveguide sensors for deep...... by Qi et al [Zm Qi et al, Sens. Actuators B 81, 2002] before, however the sensing principle we present results in a broad detection range from gasses to solid materials and is different from the principle suggested by Qi et al with a highlylimited detection range. Metal-clad waveguide sensors...

  8. Quantum mechanical description of waveguides

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Yong; Xiong Cai-Dong; He Bing

    2008-01-01

    Applying the spinor representation of the electromagnetic field,this paper present a quantum-mechanical description of waveguides.As an example of application,a potential qubit generated by photon tunnelling is discussed.

  9. Perfect imaging with geodesic waveguides

    Science.gov (United States)

    Miñano, Juan C.; Benítez, Pablo; González, Juan C.

    2010-12-01

    Transformation optics is used to prove that a spherical waveguide filled with an isotropic material with radial refractive index n=1/r has radially polarized modes (i.e. the electric field is only radial) with the same perfect focusing properties as the Maxwell fish-eye (MFE) lens. An approximate version of that device, comprising a thin waveguide with a homogeneous core, paves the way to experimentally attaining perfect imaging in the MFE lens.

  10. Intense multi-octave supercontinuum pulses from an organic emitter covering the entire THz frequency gap

    CERN Document Server

    Vicario, C; Jazbinsek, M; Lee, S -H; Kwon, O -P; Hauri, C P

    2014-01-01

    In Terahertz (THz) technology, one of the long-standing challenges has been the formation of intense pulses covering the hard-to-access frequency range of 1-15 THz (so-called THz gap). This frequency band, lying between the electronically (15 THz) accessible spectrum hosts a series of important collective modes and molecular fingerprints which cannot be fully accessed by present THz sources. While present high-energy THz sources are limited to 0.1-4 THz the accessibility to the entire THz gap with intense THz pulses would substantially broaden THz applications like live cell imaging at higher-resolution, cancer diagnosis, resonant and non-resonant control over matter and light, strong-field induced catalytic reactions, formation of field-induced transient states and contact-free detection of explosives. Here we present a new, all-in-one solution for producing and tailoring extremely powerful supercontinuum THz pulses with a stable absolute phase and covering the entire THz gap (0.1-15 THz), thus more than 7 o...

  11. Multifrequency broadband polarized horn antenna

    Science.gov (United States)

    Green, K. A.

    1981-03-01

    A corrugated conical horn antenna is simultaneously fed a multiplicity of signals, two for each of five frequencies, with each of a pair of signals fed in each of two orthogonal planes for excitation of a desired spherical hybrid mode. The lowest frequency is fed into the horn through orthogonal pairs of colinear slots, each pair being fed by coaxial tee power dividers. Other signals are fed through a circular waveguide connected to the vertex. The highest frequency signals are fed through orthogonal ports near the far end of the circular waveguide. The intermediate frequency signals are fed through orthogonal ports spaced along the waveguide. Filtering is incorporated for each to maintain isolation and low insertion loss.

  12. Graphene electrically reconfigurable patterns for THz imaging applications

    Science.gov (United States)

    Sensale-Rodriguez, Berardi; Rafique, Subrina; Yan, Rusen; Zhu, Mingda; Protasenko, Vladimir; Jena, Debdeep; Liu, Lei; Xing, Huili Grace

    2013-03-01

    THz waves are attractive for several imaging applications, since they can propagate through non metallic media such as paper, cloth, plastics, and ceramics, and do not scatter over nano-scale defects or ionize the material under imaging -as might shorter wavelengths do- while offering an image resolution similar to that of the human eye. In this work we propose and experimentally demonstrate electrically reconfigurable patterns for single-pixel terahertz imaging based on arrays of graphene THz electro-absorption modulators. In an optical setup, in conjunction with mirrors, the modulator array can transform the output radiation from a CW THz source into a pixelated and collimated beam of illumination. Single-atom-thick graphene is employed as the active element of these modulators, achieving a modulation of the THz wave reflectance >50% with a potential modulation depth approaching 100% (i.e. each region of the pixelated collimated beam can be potentially completely turned-off). Although the proof-of-concept device here discussed only consists of 4x4 elements, we foresee that this technology can enable low-cost video rate THz imaging systems.

  13. 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 ...

  14. Nonlinear THz response of a one-dimensional superlattice

    International Nuclear Information System (INIS)

    The dynamics of an electron in a one-dimensional superlattice is investigated under the action of a THz electric field. The density matrix equations of motion within a single miniband are solved using a relaxation-time approximation for scattering. The electronic response to THz radiation is obtained by calculating the dipole moment, whence we compute the power dissipated, the THz reflection coefficient and dipole radiation. Collisions are essential in eliminating transients and bringing the electron in phase with the field at dynamic localization. The optical properties of the superlattice bear strong signatures of dynamic electron localization such as oscillations with varying field strengths. In addition, the response is multivalued in the incident field owing to the nonlinear relation between the incident and internal fields of the superlattice. The optical properties are robust with respect to the inclusion of higher harmonics, weak collisions, and deviations from a tight-binding miniband dispersion. (c) 2000 The American Physical Society

  15. Coherent Cherenkov radiation as an intense THz source

    Science.gov (United States)

    Bleko, V.; Karataev, P.; Konkov, A.; Kruchinin, K.; Naumenko, G.; Potylitsyn, A.; Vaughan, T.

    2016-07-01

    Diffraction and Cherenkov radiation of relativistic electrons from a dielectric target has been proposed as mechanism for production of intense terahertz (THz) radiation. The use of an extremely short high-energy electron beam of a 4th generation light source (X-ray free electron laser) appears to be very promising. A moderate power from the electron beam can be extracted and converted into THz radiation with nearly zero absorption losses. The initial experiment on THz observation will be performed at CLARA/VELA FEL test facility in the UK to demonstrate the principle to a wider community and to develop the radiator prototype. In this paper, we present our theoretical predictions (based on the approach of polarization currents), which provides the basis for interpreting the future experimental measurements. We will also present our hardware design and discuss a plan of the future experiment.

  16. Relative infrared (IR) and terahertz (THz) signatures of common explosives

    Science.gov (United States)

    Sharpe, S. W.; Johnson, T. J.; Sheen, D. M.; Atkinson, D. A.

    2006-10-01

    Pacific Northwest National Laboratory (PNNL) has recently recorded the infrared (IR) and far-infrared (FIR, sometimes also called the terahertz, THz) spectral signatures of four common explosives in the condensed phase. The signatures of RDX, PETN, TNT and Tetryl were recorded both in the infrared and the THz domains, using Fourier transform infrared (FTIR) spectroscopy. Samples consisted of thin films and were made by depositing and subsequent evaporation of an acetone-explosive mixture. The complete spectrum spanned the range from 4,000 to 8 cm-1 at 2.0 cm-1 spectral resolution. Preliminary results in the infrared agree with those of previous workers, while the THz signatures are one order of magnitude weaker than the strongest IR bands.

  17. Terahertz Quantum Cascade Laser at 3.39 THz

    Institute of Scientific and Technical Information of China (English)

    CAO Jun-Cheng; LI Hua; HAN Ying-Jun; TAN Zhi-Yong; L(U) Jing-Tao; LUO Hui; LAFRAMBOISE Sylvain; LIU Hui-Chun

    2008-01-01

    @@ We demonstrate the growth of terahertz quantum cascade laser (THz QCL) by gas source molecular beam epitaxy.X-ray diffraction and cross-sectional transmission electron microscopic measurements show the high crystalline quality of the THz QCL active region.From the cross-sectional transmission electron microscopy image,sharp interfaces are observed and the deduced cascade period thickness is consistent with the result of x-ray diffraction.The test device is lasing at 3.39 THz and operating up to 100K in pulsed mode.At 10 K,the maximum output power is greater than 1 mW with a threshold current density of 738 A/cm2.

  18. A new mechanism for THz-frequency radiation generation: Nonlinear strain waves in piezoelectrics

    Science.gov (United States)

    Reed, Evan; Armstrong, Michael

    2007-03-01

    Using molecular dynamics simulations and analytics, we show that extremely large strain amplitude THz frequency acoustic waves can spontaneously form in crystalline GaN at the front of a shock wave and generate THz frequency radiation at an interface with AlN or another piezoelectric material. This new mechanism for the generation of THz radiation can be realized using a table-top ultrafast laser and has fundamentally different limiting properties than existing nonlinear optical ultrafast techniques for THz generation.

  19. A graphene-based broadband optical modulator

    Science.gov (United States)

    Liu, Ming; Yin, Xiaobo; Ulin-Avila, Erick; Geng, Baisong; Zentgraf, Thomas; Ju, Long; Wang, Feng; Zhang, Xiang

    2011-06-01

    Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects. Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties. Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms. Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances. Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6µm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25µm2, which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.

  20. Broadband enhancement of light harvesting in luminescent solar concentrator

    CERN Document Server

    Xiao, Yun-Feng; Xiao, Lixin; Sun, Fang-Wen; Gong, Qihuang

    2010-01-01

    Luminescent solar concentrator (LSC) can absorb large-area incident sunlight, then emit luminescence with high quantum efficiency, which finally be collected by a small photovoltaic (PV) system. The light-harvesting area of the PV system is much smaller than that of the LSC system, potentially improving the efficiency and reducing the cost of solar cells. Here, based on Fermi-golden rule, we present a theoretical description of the luminescent process in nanoscale LSCs where the conventional ray-optics model is no longer applicable. As an example calculated with this new model, we demonstrate that a slot waveguide consisting of a nanometer-sized low-index slot region sandwiched by two high-index regions provides a broadband enhancement of light harvesting by the luminescent centers in the slot region. This is because the slot waveguide can (1) greatly enhance the spontaneous emission due to the Purcell effect, (2) dramatically increase the effective absorption cross-section of luminescent centers, and (3) str...

  1. Broadband Passive Sonar Signal Simulation in Shallow Ocean

    Directory of Open Access Journals (Sweden)

    Baiju M. Nair

    2011-07-01

    Full Text Available The broadband plane wave model is valid only in the far-field of a point source under free-field propagating conditions. However the acoustics in ocean is characterized by multi-modal acoustic propagation due to its top-bottom limited boundary conditions. The effect of multi-modal field is to alter the source spectrum while the effect of dispersion is to modify the pulse shape. Moreover the use of a plane wave beamformer in a multi-modal field leads to a bias in the bearing estimates. These effects are highly dependant on the environment parameters and have important ramifications for target localization and classification in an ocean waveguide. We propose a more realistic simulator which essentially models these effects and therefore serves to provide test signals for first hand verification of signal processing algorithms to be developed for such scenarios. This model is to be understood as a better model than the naïve plane wave model which is entirely oblivious of even the gross features such as wave propagation in an oceanic waveguide. The channel parameter so estimated from the present simulation can be convolved with the radiated noise spectra of the source to generate the passive sonar signal.Defence Science Journal, 2011, 61(4, pp.370-376, DOI:http://dx.doi.org/10.14429/dsj.61.89

  2. Integration of a waveguide self-electrooptic effect device and a vertically coupled interconnect waveguide

    Science.gov (United States)

    Vawter, G. Allen

    2008-02-26

    A self-electrooptic effect device ("SEED") is integrated with waveguide interconnects through the use of vertical directional couplers. Light initially propagating in the interconnect waveguide is vertically coupled to the active waveguide layer of the SEED and, if the SEED is in the transparent state, the light is coupled back to the interconnect waveguide.

  3. Optical and THz reflectance investigations of organic solar cells

    Science.gov (United States)

    Sporea, Dan; Mihai, Laura; Sporea, Adelina; Galagan, Yulia

    2016-04-01

    Two Organic Photovoltaic devices having a photoactive layer containing Poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5- (4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM, 99%), and the layer sequences - glass/ITO/ZnO/PAL/PEDOT:PSS/Ag/encapsulation were non-destructively investigated by diffuse optical spectral reflectance, THz spectroscopy and THz imaging. The proposed methods proved to be powerful tools to support quality assurance in organic solar cells development, facilitating both the localization of manufacturing defects and the device degradation, as they are combined with "classical" evaluation means.

  4. Experimental and Theoretical Study of Carnosine in THz Range

    Science.gov (United States)

    Yan, Hai-Tao; Wang, Wei-Ning

    2005-12-01

    The characteristic fingerprints of carnosine from 0.2 to 2.6 THz are first measured by terahertz time-domain spectroscopy at room temperature. For the pure carnosine, the refractive index varies between 1.79 and 1.85 with the average value 1.84, while for the carnosine-polyethylene mixture, four absorption peaks centred at 1.37, 1.56, 1.85 and 2.49 THz are detected. A comparison of the theoretical predictions using the density functional theory with the experimental results shows satisfactory agreement except somewhat blue shift.

  5. Terahertz Transmission Imaging with 2.52 THz Continuous Wave

    Institute of Scientific and Technical Information of China (English)

    Xiao-Tong Guan; De-Wei Zheng; Min Hu; Wen-Jie Fu; Yu-Meng Cui; Xiang Fan; Liang Zhang; Ye Yuan; Jing-Yuan Xu; Yuan Li

    2013-01-01

    In this article, two terahertz transmission imaging systems are built with a 2.52 THz continuous wave laser and two types of sensors. One is array scanning system using a 124×124 pyro-electric array camera as the detector; the other is a point-wise scanning system utilizing a Golay cell as the detector. The imaging speed and quality is briefly analyzed. Terahertz (THz) imaging results demonstrate that the array scanning system has higher imaging speed with lower resolution. The point-wise scanning system has higher imaging quality with lower speed.

  6. Tunable graphene antennas for selective enhancement of THz-emission

    KAUST Repository

    Filter, Robert

    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.

  7. Tunable Graphene Antennas for Selective Enhancement of THz-Emission

    CERN Document Server

    Filter, R; Steglich, M; Alaee, R; Rockstuhl, C; Lederer, F

    2012-01-01

    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.

  8. Towards large scale HTS Josephson detector arrays for THz imaging

    Science.gov (United States)

    Du, J.; Hellicar, A. D.; Leslie, K. E.; Nikolic, N.; Hanham, S. M.; Macfarlane, J. C.; Foley, C. P.

    2013-11-01

    We present the design and implementation of a high-temperature superconducting (HTS) Josephson junction detector array for terahertz (THz) imaging. The array device is made of ten YBa2Cu3Ox-7 (YBCO) step-edge junctions coupled to gold thin-film ring-slot antennas on a MgO substrate. The design and characterization of the detector array in response to a 0.6 THz signal are presented. The development of multi-channel biasing and read-out electronics and the system integration with a commercial cryocooler are also described.

  9. Towards large scale HTS Josephson detector arrays for THz imaging

    International Nuclear Information System (INIS)

    We present the design and implementation of a high-temperature superconducting (HTS) Josephson junction detector array for terahertz (THz) imaging. The array device is made of ten YBa2Cu3Ox−7 (YBCO) step-edge junctions coupled to gold thin-film ring-slot antennas on a MgO substrate. The design and characterization of the detector array in response to a 0.6 THz signal are presented. The development of multi-channel biasing and read-out electronics and the system integration with a commercial cryocooler are also described. (paper)

  10. THz reflectometric imaging of of contemporary panel artwork

    DEFF Research Database (Denmark)

    Dandolo, Corinna Ludovica Koch; Jepsen, Peter Uhd

    2013-01-01

    Terahertz time-domain reflectometry has been applied to the investigation of a tempera panel replica. The technique has given useful information about the surface as well as the internal structure of the artworks. Ultrathin layers of leaf gold are penetrated by THz radiation, revealing the underl......Terahertz time-domain reflectometry has been applied to the investigation of a tempera panel replica. The technique has given useful information about the surface as well as the internal structure of the artworks. Ultrathin layers of leaf gold are penetrated by THz radiation, revealing...... the underlying wood structure....

  11. Writing Waveguide in LN With fs Laser

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    We investigated the waveguide formation in Lithium Niobate with Femtosecond laser pulse writing directly. The output optical field through waveguide has been observed and refractive-index change was characterized by using grating method.

  12. Miniaturized Waveguide Fourier Transform Spectrometer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To characterize the IR optical properties of the metal-coated hollow waveguide ensemble; configure the Hollow Waveguide FTS (HWFTS) chip in such a way that we...

  13. A 0.33-THz second-harmonic frequency-tunable gyrotron

    Science.gov (United States)

    Zheng-Di, Li; Chao-Hai, Du; Xiang-Bo, Qi; Li, Luo; Pu-Kun, Liu

    2016-02-01

    Dynamics of the axial mode transition process in a 0.33-THz second-harmonic gyrotron is investigated to reveal the physical mechanism of realizing broadband frequency tuning in an open cavity circuit. A new interaction mechanism about propagating waves, featured by wave competition and wave cooperation, is presented and provides a new insight into the beam-wave interaction. The two different features revealed in the two different operation regions of low-order axial modes (LOAMs) and high-order axial modes (HOAMs) respectively determine the characteristic of the overall performance of the device essentially. The device performance is obtained by the simulation based on the time-domain nonlinear theory and shows that using a 12-kV/150-mA electron beam and TE-3,4 mode, the second harmonic gyrotron can generate terahertz radiations with frequency-tuning ranges of about 0.85 GHz and 0.60 GHz via magnetic field and beam voltage tuning, respectively. Additionally, some non-stationary phenomena in the mode startup process are also analyzed. The investigation in this paper presents guidance for future developing high-performance frequency-tunable gyrotrons toward terahertz applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471007, 61531002, 61522101, and 11275206) and the Seeding Grant for Medicine and Information Science of Peking University, China (Grant No. 2014-MI-01).

  14. THz-circuits driven by photo-thermoelectric, gate-tunable graphene-junctions

    Science.gov (United States)

    Brenneis, Andreas; Schade, Felix; Drieschner, Simon; Heimbach, Florian; Karl, Helmut; Garrido, Jose A.; Holleitner, Alexander W.

    2016-01-01

    For future on-chip communication schemes, it is essential to integrate nanoscale materials with an ultrafast optoelectronic functionality into high-frequency circuits. The atomically thin graphene has been widely demonstrated to be suitable for photovoltaic and optoelectronic devices because of its broadband optical absorption and its high electron mobility. Moreover, the ultrafast relaxation of photogenerated charge carriers has been verified in graphene. Here, we show that dual-gated graphene junctions can be functional parts of THz-circuits. As the underlying optoelectronic process, we exploit ultrafast photo-thermoelectric currents. We describe an immediate photo-thermoelectric current of the unbiased device following a femtosecond laser excitation. For a picosecond time-scale after the optical excitation, an additional photo-thermoelectric contribution shows up, which exhibits the fingerprint of a spatially inverted temperature profile. The latter can be understood by the different time-constants and thermal coupling mechanisms of the electron and phonon baths within graphene to the substrate and the metal contacts. The interplay of the processes gives rise to ultrafast electromagnetic transients in high-frequency circuits, and it is equally important for a fundamental understanding of graphene-based ultrafast photodetectors and switches. PMID:27762291

  15. Planar waveguide sensor of ammonia

    Science.gov (United States)

    Rogoziński, Roman; Tyszkiewicz, Cuma; Karasiński, Paweł; Izydorczyk, Weronika

    2015-12-01

    The paper presents the concept of forming ammonia sensor based on a planar waveguide structure. It is an amplitude sensor produced on the basis of the multimode waveguide. The technological base for this kind of structure is the ion exchange method and the sol-gel method. The planar multimode waveguide of channel type is produced in glass substrate (soda-lime glass of Menzel-Glaser company) by the selective Ag+↔Na+ ion exchange. On the surface of the glass substrate a porous (~40%) silica layer is produced by the sol-gel method. This layer is sensitized to the presence of ammonia in the surrounding atmosphere by impregnation with Bromocresol Purple (BCP) dye. Therefore it constitutes a sensor layer. Spectrophotometric tests carried out showed about 50% reduction of cross-transmission changes of such sensor layer for a wave λ=593 nm caused by the presence of 25% ammonia water vapor in its ambience. The radiation source used in this type of sensor structure is a light emitting diode LED. The gradient channel waveguide is designed for frontal connection (optical glue) with a standard multimode telecommunications waveguide 62.5/125μm.

  16. Highly tunable Terahertz filter with magneto-optical Bragg grating formed in semiconductor-insulator-semiconductor waveguides

    Directory of Open Access Journals (Sweden)

    Kangwen Li

    2013-06-01

    Full Text Available A highly tunable terahertz (THz filter with magneto-optical Bragg grating formed in semiconductor-insulator-semiconductor waveguides is proposed and demonstrated numerically by means of the Finite Element Method. The results reveal that a sharp peak with high Q-value presents in the band gap of Bragg grating waveguide with a defect, and the position of the sharp peak can be modified greatly by changing the intensity of the transverse magnetic field applied to the device. Compared to the situation without magnetic field applied, the shift of the filtered frequency (wavelength reaches up to 36.1 GHz (11.4 μm when 1 T magnetic field is applied. In addition, a simple model to predict the filtered frequency and an effective way to improve the Q-value of the filter are proposed by this paper.

  17. Observations involving broadband impedance modelling

    Energy Technology Data Exchange (ETDEWEB)

    Berg, J.S. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

    1996-08-01

    Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)

  18. Observations involving broadband impedance modelling

    Energy Technology Data Exchange (ETDEWEB)

    Berg, J.S.

    1995-08-01

    Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impendance. This paper discusses three aspects of broadband impendance modeling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f cavity. The last is a discussion of requirements for the mathematical form of an impendance which follow from the general properties of impendances.

  19. 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)

  20. Silicon waveguide based TE mode converter.

    Science.gov (United States)

    Zhang, Jing; Liow, Tsung-Yang; Yu, Mingbin; Lo, Guo-Qiang; Kwong, Dim-Lee

    2010-11-22

    A silicon waveguide based TE mode converter was designed for the mode conversion between a horizontal waveguide and vertical waveguide in the two-layer structure waveguide based polarization diversity circuit. The TE mode converter's performance was studied. The polarization mode converter with minimum length of 5 μm was demonstrated to provide the TE mode conversion while maintaining the polarization status. The insertion loss at the transition region was less than 2 dB. PMID:21164874

  1. Slotted Polyimide-Aerogel-Filled-Waveguide Arrays

    Science.gov (United States)

    Rodriguez-Solis, Rafael A.; Pacheco, Hector L.; Miranda, Felix A.; Meador, Mary Ann B.

    2013-01-01

    This presentation discussed the potential advantages of developing Slotted Waveguide Arrays using polyimide aerogels. Polyimide (PI) aerogels offer great promise as an enabling technology for lightweight aerospace antenna systems. PI aerogels are highly porous solids possessing low density and low dielectric permittivity combined with good mechanical properties. For slotted waveguide array applications, there are significant advantages in mass that more than compensate for the slightly higher loss of the aerogel filled waveguide when compared to state of practice commercial waveguide.

  2. 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....

  3. Numerical study on vircator with stepped waveguide

    International Nuclear Information System (INIS)

    The author describes the numerical study on the vircator with stepped waveguide. Simulation results demonstrate that the length of stepped waveguide can strongly affect the microwave generation, when the resonance frequency of equivalent column cavity for stepped waveguide is about equal to the frequency of the virtual cathode oscillation, the efficiency of microwave generation is maximum and the spectrum of microwave is more singular, the efficiency of microwave generation varies periodically with the length of stepped waveguide

  4. Systematic Design of Slow Light Waveguides

    DEFF Research Database (Denmark)

    Wang, Fengwen

    Light can propagate much slower in photonic crystal waveguides and plasmonic waveguides than in vacuum. Slow light propagation in waveguides shows broad prospects in the terabit communication systems. However, it causes severe signal distortions and displays large propagation loss. Moreover it is...

  5. 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...

  6. Plasmonic waveguides cladded by hyperbolic metamaterials

    DEFF Research Database (Denmark)

    Ishii, Satoshi; Shalaginov, Mikhail Y.; Babicheva, Viktoriia E.;

    2014-01-01

    Strongly anisotropic media with hyperbolic dispersion can be used for claddings of plasmonic waveguides (PWs). In order to analyze the fundamental properties of such waveguides, we analytically study 1D waveguides arranged from a hyperbolic metamaterial (HMM) in a HMM-Insulator-HMM (HIH) structure...

  7. Mode conversion based on forward stimulated Brillouin scattering in a hybrid phononic-photonic waveguide.

    Science.gov (United States)

    Chen, Guodong; Zhang, Ruiwen; Sun, Junqiang; Xie, Heng; Gao, Ya; Feng, Danqi; Xiong, Huang

    2014-12-29

    We propose a scheme for on-chip all optical mode conversion based on forward stimulated Brillouin scattering in a hybrid phononic-photonic waveguide. To describe the mode conversion the theoretical model of the FSBS is established by taking into account the radiation pressure and the electrostriction force simultaneously. The numerical simulation is carried out for the mode conversion from the fundamental mode E11x to the higher-order mode E21x. The results indicate that the mode conversion efficiency is affected by the waveguide length and the input pump light power, and the highest efficiency can reach upto 88% by considering the influence of optical and acoustic absorption losses in the hybrid waveguide. Additionally, the conversion bandwidth with approximate 12.5 THz can be achieved in 1550nm communication band. This mode converter on-chip is a promising device in the integrated optical systems, which can effectively increase the capacity of silicon data busses for on-chip optical interconnections. PMID:25607172

  8. Design of a polymer-filled silicon nitride strip/slot asymmetric hybrid waveguide for realizing both flat dispersion and athermal operation.

    Science.gov (United States)

    Bian, Dandan; Chen, Shaowu; Lei, Xun; Qin, Guanshi; Chen, Zhanguo

    2016-06-20

    An asymmetric strip/slot hybrid silicon nitride waveguide is designed to simultaneously realize athermal operation and flat dispersion. The slot filling and upper cladding materials are negative thermal-optical coefficient (TOC), low refractive index polyurethane acrylate, while the left and right cladding layers are positive TOC, high refractive index silicon nitride. With suitable waveguide parameter selection, an optimum strip/slot hybrid silicon nitride waveguide exhibits an effective TOC of 1.263×10-7/K at 1550 nm, flattened dispersion in the wavelength range from 1200 to 1800 nm with the maximum dispersion of 30.51 ps/(nm·km), and a minimum of 10.89 ps/(nm·km). The proposed hybrid waveguide has great potential in building up broadband athermal microresonator optical frequency combs.

  9. High-power Waveguide Dampers for the Short-Pulse X-Ray Project at the Advanced Photon Source

    Energy Technology Data Exchange (ETDEWEB)

    Waldschmidt, G J; Liu, J; Middendorf, M E; Nassiri, A; Smith, T L; Wu, G; Henry, J; Mammosser, J D; Rimmer, R A

    2012-07-01

    High-power waveguide dampers have been designed and prototyped for the Short-Pulse X-ray (SPX) cavities at the Advanced Photon Source. The cavities will operate at 2.815 GHz and utilize the TM110 dipole mode. As a result, higher-order (HOM) and lower-order mode (LOM) in-vacuum dampers have been designed to satisfy the demanding broadband damping requirements in the APS storage ring. The SPX single-cell cavity consists of two WR284 waveguides for damping the HOMs and one WR284 waveguide for primarily damping the LOM where up to 2kW will be dissipated in the damping material. The damper designs and high-power experimental results will be discussed in this paper.

  10. 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......-effective-mass states in the energy-momentum space of the conduction band. Further, we observe the typical accompanying effects of saturable absorption on the THz pulses, such as an increase of the group delay, as the peak electric field of the pulse increases. In this paper we present the results of nonlinear THz time...

  11. Coupled-resonator optical waveguides

    DEFF Research Database (Denmark)

    Raza, Søren; Grgic, Jure; Pedersen, Jesper Goor;

    2010-01-01

    Coupled-resonator optical waveguides hold potential for slow-light propagation of optical pulses. The dispersion properties may adequately be analyzed within the framework of coupled-mode theory. We extend the standard coupled-mode theory for such structures to also include complex-valued paramet......Coupled-resonator optical waveguides hold potential for slow-light propagation of optical pulses. The dispersion properties may adequately be analyzed within the framework of coupled-mode theory. We extend the standard coupled-mode theory for such structures to also include complex...

  12. TSUNAMI WAVE PROPAGATION ALONG WAVEGUIDES

    Directory of Open Access Journals (Sweden)

    Andrei G. Marchuk

    2009-01-01

    Full Text Available This is a study of tsunami wave propagation along the waveguide on a bottom ridge with flat sloping sides, using the wave rays method. During propagation along such waveguide the single tsunami wave transforms into a wave train. The expression for the guiding velocities of the fastest and slowest signals is defined. The tsunami wave behavior above the ocean bottom ridges, which have various model profiles, is investigated numerically with the help of finite difference method. Results of numerical experiments show that the highest waves are detected above a ridge with flat sloping sides. Examples of tsunami propagation along bottom ridges of the Pacific Ocean are presented.

  13. Towards THz Communications - Status in Research, Standardization and Regulation

    Science.gov (United States)

    Kürner, Thomas; Priebe, Sebastian

    2013-08-01

    In the most recent years, wireless communication networks have been facing a rapidly increasing demand for mobile traffic along with the evolvement of applications that require data rates of several 10s of Gbit/s. In order to enable the transmission of such high data rates, two approaches are possible in principle. The first one is aiming at systems operating with moderate bandwidths at 60 GHz, for example, where 7 GHz spectrum is dedicated to mobile services worldwide. However, in order to reach the targeted date rates, systems with high spectral efficiencies beyond 10 bit/s/Hz have to be developed, which will be very challenging. A second approach adopts moderate spectral efficiencies and requires ultra high bandwidths beyond 20 GHz. Such an amount of unregulated spectrum can be identified only in the THz frequency range, i.e. beyond 300 GHz. Systems operated at those frequencies are referred to as THz communication systems. The technology enabling small integrated transceivers with highly directive, steerable antennas becomes the key challenges at THz frequencies in face of the very high path losses. This paper gives an overview over THz communications, summarizing current research projects, spectrum regulations and ongoing standardization activities.

  14. THz quantum-confined Stark effect in semiconductor quantum dots

    DEFF Research Database (Denmark)

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

    2012-01-01

    We demonstrate an instantaneous all-optical manipulation of optical absorption at the ground state of InGaAs/GaAs quantum dots (QDs) via a quantum-confined Stark effect (QCSE) induced by the electric field of incident THz pulses with peak electric fields reaching 200 kV/cm in the free space. As a...

  15. THz Photonic Band-Gap Prisms Fabricated by Fiber Drawing

    DEFF Research Database (Denmark)

    Busch, Stefan F.; Xu, Lipeng; Stecher, Matthias;

    2012-01-01

    We suggest a novel form of polymeric based 3D photonic crystal prisms for THz frequencies which could be fabricated using a standard fiber drawing technique. The structures are modeled and designed using a finite element analyzing technique. Using this simulation software we theoretically study...

  16. Fiber Drawn 2D Polymeric Photonic Crystal THz Filters

    DEFF Research Database (Denmark)

    Stecher, Matthias; Jansen, Christian; Ahmadi-Boroujeni, Mehdi;

    2012-01-01

    In this paper, we report on different polymeric 2D photonic crystal filters for THz frequencies which are fabricated by a standard fiber drawing technique. The bandstop filters were simulated and designed by the generalized multipole technique (GMT). The frequency and angle dependent transmission...

  17. Defect effects on THz wave emission induced by ion irradiation

    International Nuclear Information System (INIS)

    Background: As the core component of terahertz system, terahertz source determines the performance of the whole system. The THz wave emission efficiency depends decisively on the THz emitting materials which are usually made of low-temperature-grown gallium arsenide. It is found that through ion irradiation better THz wave emission material can be prepared, which overcomes the poor reproducibility of high quality material prepared by the traditional method. Purpose: In order to find out the best irradiation condition for producing the required photoconductive material, we try to clarify the mechanism of the THz wave emission induced by ion implantation. Methods: Applying Monte Carlo method, we simulated the terahertz emission under different defect conditions, and tested the emission efficiency of GaAs and InP(Fe) irradiated by N ions with the energy of 500 keV and 1.5 MeV, respectively. Results: MC simulation study shows that both capture cross-section and trap density can cause changes in terahertz pulse width and peak intensity. From the experiments conducted on ion irradiated semiconductors we found only the peak intensity changes with the irradiation fluence. Conclusion: It is proposed that intrinsic defects introduced during growth of crystals are the key defects that contribute mainly to the terahertz wave emission behavior, and defects introduced by ion irradiation may only modify the transport property of carriers through scattering in semiconductor, by which it changes the terahertz wave emission performance. (authors)

  18. A 3-Dimensional display and process software for THz spectrum

    Science.gov (United States)

    Jiang, Xiaowen; Zhang, Zhaohui; Zhao, Xiaoyan; Yin, Yixin; Ajito, Katsuhiro; Song, Hojin

    2011-02-01

    An underpinning software is devoted to THz spectrum analyzing and 3-D imaging. The paper describes the software's outline, structure, functions and some of considerations. Users in LAN (local area network) can access it and implement some basic and advanced works such as files operation, echoes cutting, spectrum calculation, baseline cancelling, peak fitting, qualitative and quantitative measuring of solid-state samples.

  19. Investigations on time stability of passive THz imaging

    Science.gov (United States)

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

    2014-10-01

    Terahertz radiation is within the frequency range from 100 GHz to 10THz. This radiation has specific characteristics in terms of imaging. The radiation is harmless to the human body because the energy transferred by electromagnetic waves in this range of frequencies are very small thus there is no ionization of matter. The development of imaging devices and exploration of new spectral bands is a chance to introduce new equipment for assuring public safety. It has been proved that objects hidden under clothing can be detected and visualized using terahertz (THz) cameras. However, passive THz cameras still offer too low image resolution for objects recognition. In order to determine the properties of terahertz imaging for detection of hidden objects several aspects need to be considered. Taking into account the fact that the image captured by the terahertz camera reflects the spatial distribution of the relative temperature of the observed objects, the effect of the measurement time on the imaging capabilities should be examined. A very important aspect is the influence of the type (material composition) of coating material, as well as the type of an object hidden under clothing (size and material). The purpose of the studies is to investigate the time stability of passive THz imaging on 250 GHz for detection of concealed objects. In the article, we present the measurement setup, the measurement methodology as well as the initial results of measurements with various types of clothing and test objects.

  20. Quantum-dot micropillars for parametric THz emission

    DEFF Research Database (Denmark)

    Mariani, S.; Andronico, A.; Favero, I.;

    2013-01-01

    We report on the design, fabrication and optical investigation of AlGaAs microcavities for THz Difference Frequency Generation (DFG) between Whispering Gallery Modes (WGMs), where the pump and DFG wavelengths (λ ≈ 1.3 μm and λ ≈ 75-150 μm, respectively) lie on opposite sides of the Restrahlen ban...

  1. Current responsivity of semiconductor superlattice THz-photon detectors

    DEFF Research Database (Denmark)

    Ignatov, Anatoly A.; Jauho, Antti-Pekka

    1999-01-01

    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...

  2. Graphene-based THz modulator analyzed by equivalent circuit model

    DEFF Research Database (Denmark)

    Xiao, Binggang; Chen, Jing; Xie, Zhiyi;

    2016-01-01

    A terahertz (THz) modulator based on graphene is proposed and analysed by use of equivalent transmission line of a homogeneous mediumand the local anisotropic model of the graphene conductivity. The result calculated by the equivalent circuit is consistent with that obtained byFresnel transfer ma...

  3. THz time-domain spectroscopy for tokamak plasma diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Causa, F.; Zerbini, M.; Buratti, P.; Gabellieri, L.; Pacella, D.; Romano, A.; Tuccillo, A. A.; Tudisco, O. [ASSOCIAZIONE EURATOM ENEA sulla Fusione, C. R. Frascati, via E. Fermi 45, 00044 Frascati (Roma) (Italy); Johnston, M. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Doria, A.; Gallerano, G. P.; Giovenale, E. [ENEA C.R. Frascati UTAPRAD, via E. Fermi 45, 00044 Frascati (Roma) (Italy)

    2014-08-21

    The technology is now becoming mature for diagnostics using large portions of the electromagnetic spectrum simultaneously, in the form of THz pulses. THz radiation-based techniques have become feasible for a variety of applications, e.g., spectroscopy, imaging for security, medicine and pharmaceutical industry. In particular, time-domain spectroscopy (TDS) is now being used also for plasma diagnostics in various fields of application. This technique is promising also for plasmas for fusion applications, where plasma characteristics are non-uniform and/or evolve during the discharge This is because THz pulses produced with femtosecond mode-locked lasers conveniently span the spectrum above and below the plasma frequency and, thus, can be used as very sensitive and versatile probes of widely varying plasma parameters. The short pulse duration permits time resolving plasma characteristics while the large frequency span permits a large dynamic range. The focus of this work is to present preliminary experimental and simulation results demonstrating that THz TDS can be realistically adapted as a versatile tokamak plasma diagnostic technique.

  4. Possible THz gain in superlattices at a stable operation point

    DEFF Research Database (Denmark)

    Wacker, Andreas; Allen, S. J.; Scott, J. S.;

    1997-01-01

    We demonstrate that semiconductor superlattices may provide gain at THz frequencies at an operation point which is stable against fluctuations at lower frequency. While an explicit experimental demonstration for the sample considered could not be achieved, the underlying principle of quantum...

  5. Broadband/Wideband Magnetoelectric Response

    Directory of Open Access Journals (Sweden)

    Chee-Sung Park

    2012-01-01

    Full Text Available A broadband/wideband magnetoelectric (ME composite offers new opportunities for sensing wide ranges of both DC and AC magnetic fields. The broadband/wideband behavior is characterized by flat ME response over a given AC frequency range and DC magnetic bias. The structure proposed in this study operates in the longitudinal-transversal (L-T mode. In this paper, we provide information on (i how to design broadband/wideband ME sensors and (ii how to control the magnitude of ME response over a desired frequency and DC bias regime. A systematic study was conducted to identify the factors affecting the broadband/wideband behavior by developing experimental models and validating them against the predictions made through finite element modeling. A working prototype of the sensor with flat bands for both DC and AC magnetic field conditions was successfully obtained. These results are quite promising for practical applications such as current probe, low-frequency magnetic field sensing, and ME energy harvester.

  6. Present Status and Results from the KAERI Compact THz FEL Facility

    CERN Document Server

    Jeong, Y U; Lee, B C; Park, S H

    2005-01-01

    We have developed a laboratory-scale users facility with a compact terahertz (THz) 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 for bio-medical researches. Transmitted THz imaging of various samples including bugs have been measured. The samples were scanned by a 2-dimensional stage at the focal point of the THz beam. The bugs were not dry because they were killed just before experiments. We could get the transmitted THz imaging of the bugs at 3 THz with the high power THz FEL. THz spectral characteristics of several materials have been studied by the FEL and a THz FTIR spectrometer. We will introduce recent results on the imaging and spectroscopy by the THz FEL.

  7. Performances of THz cameras with enhanced sensitivity in sub-terahertz region

    Science.gov (United States)

    Oda, Naoki; Ishi, Tsutomu; Kurashina, Seiji; Sudou, Takayuki; Morimoto, Takao; Miyoshi, Masaru; Doi, Kohei; Goto, Hideki; Sasaki, Tokuhito; Isoyama, Goro; Kato, Ryukou; Irizawa, Akinori; Kawase, Keigo

    2015-05-01

    Uncooled microbolometer-type 640x480 and 320x240 Terahertz (THz) focal plane arrays (FPAs) with enhanced sensitivity in sub-THz region are developed, and incorporated into 640x480 and 320x240 cameras, respectively. The pixel in the THz-FPA has such a structure that an area sensitive to electromagnetic wave is suspended above read-out integrated circuit (ROIC). A thin metallic layer is formed on the top of the sensitive area, while a thick metallic layer is formed on the surface of ROIC. The structure composed of the thin metallic layer and the thick metallic layer behaves as an optical cavity. The THz-FPAs reported in this paper have a modified pixel structure which has several times longer optical-cavity length than NEC's previous pixel does, by forming a thick SiN layer on the ROIC. The extended optical-cavity structure is favorable for detecting electromagnetic wave with lower frequency. Consequently, the Minimum Detectable Power per pixel (MDP) is improved ten times in sub-THz region, especially 0.5-0.6 THz. This paper presents spectral frequency dependences of MDP values for THz-FPA with the modified pixel structure and THz-FPA with the previous pixel structure, using THz free electron laser (FEL) developed by Osaka University. The modification of pixel structure extends high sensitivity region to lower frequency region, such as sub-THz region, and the wider spectral coverage of THz camera surely expands its applicability

  8. The time resolved measurement of ultrashort THz-band electric fields without an ultrashort probe

    CERN Document Server

    Walsh, David A; Jamison, Steven P

    2015-01-01

    The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse, and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.

  9. Focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces.

    Science.gov (United States)

    Zhong, Qiuhang; Veerasubramanian, Venkat; Wang, Yun; Shi, Wei; Patel, David; Ghosh, Samir; Samani, Alireza; Chrostowski, Lukas; Bojko, Richard; Plant, David V

    2014-07-28

    We report on the design and characterization of focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces. With implementation of waveguide dispersion engineered subwavelength structures, an ultra-wide 1-dB bandwidth of over 100 nm (largest reported to date) near 1550 nm is experimentally achieved for transverse-electric polarized light. By tapering the subwavelength structures, back reflection is effectively suppressed and grating coupling efficiency is increased to -4.7 dB. A compact device footprint of 40 µm × 20 µm is realized by curving the gratings in a focusing scheme. PMID:25089441

  10. A broadband ferromagnetic resonance spectrometer to measure thin films up to 70 GHz.

    Science.gov (United States)

    Harward, I; O'Keevan, T; Hutchison, A; Zagorodnii, V; Celinski, Z

    2011-09-01

    We report the development of a broadband ferromagnetic resonance (FMR) system operating in the frequency range from 10 MHz to 70 GHz using a closed-cycle He refrigeration system for measurements of thin films and micron/nano structures. The system is capable of carrying out measurements in frequency and field domain. Using two coplanar waveguides, it is capable of simultaneously measuring two samples in the out of plane and in plane FMR geometries. The system operates in the temperature range of 27-350 K and is sensitive to less than one atomic monolayer of a single crystal Fe film. PMID:21974627

  11. Applications of terahertz (THz) technology to medical imaging

    Science.gov (United States)

    Arnone, Donald D.; Ciesla, Craig M.; Corchia, Alessandra; Egusa, S.; Pepper, Michael; Chamberlain, J. Martyn; Bezant, C.; Linfield, Edmund H.; Clothier, R.; Khammo, N.

    1999-09-01

    An imaging system has been developed based on pulses of Terahertz (THz) radiation generated and detected using all- optical effects accessed by irradiating semiconductors with ultrafast pulses of visible laser light. This technique, commonly referred to as T-Ray Imaging or THz Pulse Imaging (TPI), holds enormous promise for certain aspects of medical imaging. We have conducted an initial survey of possible medical applications of TPI and demonstrated that TPI images show good contrast between different animal tissue types. Moreover, the diagnostic power of TPI has been elicidated by the spectra available at each pixel in the image, which are markedly different for the different tissue types. This suggests that the spectral information inherent in TPI might be used to identify the type of soft and hard tissue at each pixel in an image and provide other diagnostic information not afforded by conventional imagin techniques. Preliminary TPI studies of pork skin show that 3D tomographic imaging of the skin surface and thickness is possible, and data from experiments on models of the human dermis are presented which demonstrate that different constituents of skin have different refractive indices. Lastly, we present the first THz image of human tissue, namely an extracted tooth. The time of flight of THz pulses through the tooth allows the thickness of the enamel to be determined, and is used to create an image showing the enamel and dentine regions. Absorption of THz pulses in the tooth allows the pulp cavity region to be identified. Initial evidence strongly suggests that TPI my be used to provide valuable diagnostic information pertaining to the enamel, dentine, and the pump cavity.

  12. Simulation of FEL pulse length calculation with THz streaking method

    Energy Technology Data Exchange (ETDEWEB)

    Gorgisyan, I., E-mail: ishkhan.gorgisyan@psi.ch [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); École Polytechnique Fédérale de Lausanne, Route Cantonale, 1015 Lausanne (Switzerland); Ischebeck, R.; Prat, E.; Reiche, S. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Rivkin, L. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); École Polytechnique Fédérale de Lausanne, Route Cantonale, 1015 Lausanne (Switzerland); Juranić, P., E-mail: ishkhan.gorgisyan@psi.ch [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland)

    2016-04-02

    Simulation of THz streaking of photoelectrons created by X-ray pulses from a free-electron laser and reconstruction of the free-electron laser pulse lengths. Having accurate and comprehensive photon diagnostics for the X-ray pulses delivered by free-electron laser (FEL) facilities is of utmost importance. Along with various parameters of the photon beam (such as photon energy, beam intensity, etc.), the pulse length measurements are particularly useful both for the machine operators to measure the beam parameters and monitor the stability of the machine performance, and for the users carrying out pump–probe experiments at such facilities to better understand their measurement results. One of the most promising pulse length measurement techniques used for photon diagnostics is the THz streak camera which is capable of simultaneously measuring the lengths of the photon pulses and their arrival times with respect to the pump laser. This work presents simulations of a THz streak camera performance. The simulation procedure utilizes FEL pulses with two different photon energies in hard and soft X-ray regions, respectively. It recreates the energy spectra of the photoelectrons produced by the photon pulses and streaks them by a single-cycle THz pulse. Following the pulse-retrieval procedure of the THz streak camera, the lengths were calculated from the streaked spectra. To validate the pulse length calculation procedure, the precision and the accuracy of the method were estimated for streaking configuration corresponding to previously performed experiments. The obtained results show that for the discussed setup the method is capable of measuring FEL pulses with about a femtosecond accuracy and precision.

  13. Near-unity broadband absorption designs for semiconducting nanowire arrays via localized radial mode excitation.

    Science.gov (United States)

    Fountaine, Katherine T; Kendall, Christian G; Atwater, Harry A

    2014-05-01

    We report design methods for achieving near-unity broadband light absorption in sparse nanowire arrays, illustrated by results for visible absorption in GaAs nanowires on Si substrates. Sparse (unity absorption at wire resonant wavelengths due to coupling into 'leaky' radial waveguide modes of individual wires and wire-wire scattering processes. From a detailed conceptual development of radial mode resonant absorption, we demonstrate two specific geometric design approaches to achieve near unity broadband light absorption in sparse nanowire arrays: (i) introducing multiple wire radii within a small unit cell array to increase the number of resonant wavelengths, yielding a 15% absorption enhancement relative to a uniform nanowire array and (ii) tapering of nanowires to introduce a continuum of diameters and thus resonant wavelengths excited within a single wire, yielding an 18% absorption enhancement over a uniform nanowire array.

  14. Generation of THz-radiation in the Cherenkov decelerating structure with planar geometry at frequency ∼ 0.675 THz

    Science.gov (United States)

    Ashanin, I. A.; Polozov, S. M.

    2016-07-01

    One of the ways to generate THz-radiation is by the relativistic electron bunches travelling through Cherenkov decelerating dielectric filled capillary channel. Sapphire or other dielectric materials can be used for the internal surface coating of the capillary. Relativistic electron bunches of ∼100 µm in diameter and pulse durations of 1 ps or shorter are capable to produce substantial power of THz-radiation. The aperture of Cherenkov decelerating structure should be comparable with the sub-mm wavelength (0.05-3 mm). Such type of decelerating system allows providing of the wide range of operating parameters at the various geometrical sizes. But it is necessary to consider that such capillaries are difficult in production as there is a requirement to drill a small aperture in a long crystal of high hardness but brittle. In this regard it would be desirable to offer transition option from the axial to the planar geometry. Furthermore the ribbon beam has some advantages as focusing at low energies and possessing smaller expansion in the drift space. The authors present design and results of electrodynamics study of the decelerating planar dielectric filling Cherenkov channel at frequency 0.675 THz in this article. It is also delivered characteristic comparison with axial geometry channel. A horn antenna attached to such channel at 0.675 THz resonant frequency is considered.

  15. 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.

  16. Quantum waveguides with corners

    Directory of Open Access Journals (Sweden)

    Raymond Nicolas

    2012-04-01

    Full Text Available The simplest modeling of planar quantum waveguides is the Dirichlet eigenproblem for the Laplace operator in unbounded open sets which are uniformly thin in one direction. Here we consider V-shaped guides. Their spectral properties depend essentially on a sole parameter, the opening of the V. The free energy band is a semi-infinite interval bounded from below. As soon as the V is not flat, there are bound states below the free energy band. There are a finite number of them, depending on the opening. This number tends to infinity as the opening tends to 0 (sharply bent V. In this situation, the eigenfunctions concentrate and become self-similar. In contrast, when the opening gets large (almost flat V, the eigenfunctions spread and enjoy a different self-similar structure. We explain all these facts and illustrate them by numerical simulations. La modélisation la plus simple des guides d’ondes quantiques plans est le problème aux valeurs propres pour le laplacien dans des ouverts non bornés qui sont fins dans une direction. Ici nous considérons des guides en forme de V. Leurs propriétés spectrales dépendent essentiellement d’un seul paramètre, l’ouverture du V. La bande d’énergie libre est un intervalle semi-infini borné inférieurement. Dès que le V n’est pas plat, il existe des états liés sous la bande d’énergie libre. Ils sont en nombre fini, fonction de l’ouverture. Ce nombre tend vers l’infini quand l’ouverture tend vers 0 (V très refermé. Dans cette situation, les fonctions propres se concentrent et deviennent auto-similaires. À l’opposé, quand l’ouverture est grande (V très aplati, les fonctions propres s’étalent et jouissent d’une autre structure auto-similaire. Nous expliquons tous ces résultats et les illustrons par des expériences numériques.

  17. Plasmonic Antennas Hybridized with Dielectric Waveguides

    CERN Document Server

    Arango, Felipe Bernal; Koenderink, A Femius

    2013-01-01

    For the purpose of using plasmonics in an integrated scheme where single emitters can be probed efficiently, we experimentally and theoretically study the scattering properties of single nano-rod gold antennas as well as antenna arrays placed on one-dimensional dielectric silicon nitride waveguides. Using real space and Fourier microscopy correlated with waveguide transmission measurements, we quantify the spectral properties, absolute strength and directivity of scattering. The scattering processes can be well understood in the framework of the physics of dipolar objects placed on a planar layered environment with a waveguiding layer. We use the single plasmonic structures on top of the waveguide as dipolar building blocks for new types of antennas where the waveguide enhances the coupling between antenna elements. We report on waveguide hybridized Yagi-Uda antennas which show directionality in out-coupling of guided modes as well as directionality for in-coupling into the waveguide of localized excitations ...

  18. Numerical simulation of broadband vortex terahertz beams propagation

    Science.gov (United States)

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

    2016-08-01

    Orbital angular momentum (OAM) represents new informational degree of freedom for data encoding and multiplexing in fiber and free-space communications. OAM-carrying beams (also called vortex beams) were successfully used to increase the capacity of optical, millimetre-wave and radio frequency communication systems. However, the investigation of the OAM potential for the new generation high-speed terahertz communications is also of interest due to the unlimited demand of higher capacity in telecommunications. Here we present a simulation-based study of the propagating in non-dispersive medium broadband terahertz vortex beams generated by a spiral phase plate (SPP). The algorithm based on scalar diffraction theory was used to obtain the spatial amplitude and phase distributions of the vortex beam in the frequency range from 0.1 to 3 THz at the distances 20-80 mm from the SPP. The simulation results show that the amplitude and phase distributions without unwanted modulation are presented in the wavelengths ranges with centres on the wavelengths which are multiple to the SPP optical thickness. This fact may allow to create the high-capacity near-field communication link which combines OAM and wavelength-division multiplexing.

  19. Glass Waveguides for Periodic Poling

    DEFF Research Database (Denmark)

    Fage-Pedersen, Jacob; Jacobsen, Rune Shim; Kristensen, Martin

    2005-01-01

    Planar silica-based waveguide devices have been developed for second-harmonic generation by poling with periodic electrodes. We show that detrimental charge transport can occur along interfaces, but with proper choice of fabrication, high-quality devices are obtained....

  20. Hybrid graphene plasmonic waveguide modulators

    Science.gov (United States)

    Ansell, D.; Radko, I. P.; Han, Z.; Rodriguez, F. J.; Bozhevolnyi, S. I.; Grigorenko, A. N.

    2015-11-01

    The unique optical and electronic properties of graphene make possible the fabrication of novel optoelectronic devices. One of the most exciting graphene characteristics is the tunability by gating which allows one to realize active optical devices. While several types of graphene-based photonic modulators have already been demonstrated, the potential of combining the versatility of graphene with subwavelength field confinement of plasmonic waveguides remains largely unexplored. Here we report fabrication and study of hybrid graphene-plasmonic waveguide modulators. We consider several types of modulators and identify the most promising one for telecom applications. The modulator working at the telecom range is demonstrated, showing a modulation depth of >0.03 dB μm-1 at low gating voltages for an active device area of just 10 μm2, characteristics which are already comparable to those of silicon-based waveguide modulators while retaining the benefit of further device miniaturization. Our proof-of-concept results pave the way towards on-chip realization of efficient graphene-based active plasmonic waveguide devices for optical communications.

  1. Photonic-crystal waveguide biosensor

    DEFF Research Database (Denmark)

    Skivesen, Nina; Têtu, Amélie; Kristensen, Martin;

    2007-01-01

    A photonic-crystal waveguide sensor is presented for biosensing. The sensor is applied for refractive index measurements and detection of protein-concentrations. Concentrations around 10 μg/ml (0.15μMolar) are measured with excellent signal to noise ratio, and a broad, dynamic refractive index...

  2. Optical waveguide devices for bioanalysis

    OpenAIRE

    Wilkinson, J.S.

    2010-01-01

    Integrated optical waveguides offer great potential as versatile platforms for constructing advanced biosensors, optical cell-sorters and integrated optofluidic systems, exploiting the technological approaches of microelectronics and guided-wave optics to realise low-cost on-chip systems. Progress towards optical integration in microsystems for bioanalysis will be discussed, with examples in key applications, and challenges and opportunities will be described.

  3. Poling of Planar Silica Waveguides

    DEFF Research Database (Denmark)

    Arentoft, Jesper; Kristensen, Martin; Jensen, Jesper Bo

    1999-01-01

    UV-written planar silica waveguides are poled using two different poling techniques, thermal poling and UV-poling. Thermal poling induces an electro-optic coefficient of 0.067 pm/V. We also demonstrate simultaneous UV-writing and UV-poling. The induced electro-optic effect shows a linear dependence...

  4. Dielectric waveguide amplifiers and lasers

    NARCIS (Netherlands)

    Pollnau, M.

    2014-01-01

    The performance of semiconductor amplifiers and lasers has made them the preferred choice for optical gain on a micro-chip. In the past few years, we have demonstrated that also rare-earth-ion-doped dielectric waveguides show remarkable performance, ranging from a small-signal gain per unit length o

  5. Parabolic tapers for overmoded waveguides

    Science.gov (United States)

    Doane, J.L.

    1983-11-25

    A waveguide taper with a parabolic profile, in which the distance along the taper axis varies as the square of the tapered dimension, provides less mode conversion than equal length linear tapers and is easier to fabricate than other non-linear tapers.

  6. Tunable band-notched line-defect waveguide in a surface-wave photonic crystal

    CERN Document Server

    Gao, Zhen; Zhang, Youming; Xu, Hongyi; Zhang, Baile

    2016-01-01

    We propose and experimentally demonstrate a tunable band-notched line-defect waveguide in a surface-wave photonic crystal, which consists of a straight line-defect waveguide and side-coupled defect cavities. A tunable narrow stopband can be observed in the broadband transmission spectra. We also demonstrate that both the filtering levels and filtering frequencies of the band-notched line-defect waveguide can be conveniently tuned through changing the total number and the pillar height of the side-coupled defect cavities. The band-notch function is based on the idea that the propagating surface modes with the resonance frequencies of the side-coupled defect cavities will be tightly localized around the defect sites, being filtered from the waveguide output. Transmission spectra measurements and direct near-field profiles imaging are performed at microwave frequencies to verify our idea and design. These results may enable new band-notched devices design and provide routes for the realization of tunable surface...

  7. Terahertz hot electron bolometer waveguide mixers for GREAT

    CERN Document Server

    Pütz, P; Jacobs, K; Justen, M; Schultz, M; Stutzki, J

    2012-01-01

    Supplementing the publications based on the first-light observations with the German Receiver for Astronomy at Terahertz frequencies (GREAT) on SOFIA, we present background information on the underlying heterodyne detector technology. We describe the superconducting hot electron bolometer (HEB) detectors that are used as frequency mixers in the L1 (1400 GHz), L2 (1900 GHz), and M (2500 GHz) channels of GREAT. Measured performance of the detectors is presented and background information on their operation in GREAT is given. Our mixer units are waveguide-based and couple to free-space radiation via a feedhorn antenna. The HEB mixers are designed, fabricated, characterized, and flight-qualified in-house. We are able to use the full intermediate frequency bandwidth of the mixers using silicon-germanium multi-octave cryogenic low-noise amplifiers with very low input return loss. Superconducting HEB mixers have proven to be practical and sensitive detectors for high-resolution THz frequency spectroscopy on SOFIA. W...

  8. A Directly-Written Monolithic Waveguide-Laser Incorporating a DFB Waveguide-Bragg Grating

    CERN Document Server

    Marshall, Graham D; Ams, Martin; Piper, James A; Withford, Michael J

    2008-01-01

    We report the fabrication and performance of the first C-band directly-written monolithic waveguide-laser. The waveguide-laser device was created in an Erbium and Ytterbium doped phosphate glass host and consisted of an optical waveguide that included a distributed feedback Bragg grating structure. The femtosecond laser direct-write technique was used to create both the waveguide and the waveguide-Bragg grating simultaneously and in a single processing step. The waveguide-laser was optically pumped at approximately 980 nm and lased at 1537nm with a bandwidth of less than 4 pm.

  9. A scheme for a terahertz traveling-wave amplifier working with the TE11 mode in a circular waveguide

    International Nuclear Information System (INIS)

    To enlarge the interaction structure to a feasible dimension and to decrease the required magnetic field to an available strength, the gyrotron devices at THz frequencies must be designed with a high-order-mode interaction, which is weaker in a beam–wave interaction and more susceptible to mode competition. Using the same interaction structure (a circular waveguide) as in the gyrotron traveling-wave amplifier (gyro-TWT), but replacing the axial magnetic field of the gyro-TWT with a tapered helical magnetic field, we found that the gyrating electrons are able to perform strong interaction with the TE11 mode in the THz region. Through an example case, we explored the behavior of the particles and wave fields as in a beam–wave interaction under a modified scheme of the gyro-TWT with a numerical simulation code. The equations required for the simulation are presented. The simulation result of the example case indicates that, through the TE11 beam–wave interaction under the presented scheme, more than one quarter of the beam energy can be converted to the wave at 612.7 GHz and to heat, dissipated on the waveguide wall, of radius 2.5 cm

  10. Compact polarization rotators for integrated polarization diversity in InP-based waveguides

    Science.gov (United States)

    Beggs, Daryl M.; Midrio, Michele; Krauss, Thomas F.

    2007-08-01

    We present the design, fabrication, and operation of a polarization converter based on angled waveguides in the InP/InGaAsP material system. By combining design elements from mode evolution and birefringent devices, the total device length is kept short (less than 50μm) and the insertion efficiency high at 81%+/-19%, which corresponds to an insertion loss of 1dB. Devices operate broadband, i.e., the polarization conversion exceeds 15dB over a 100nm wavelength range. A polarization rotator with these specifications is a prime candidate for use in an integrated polarization diversity scheme.

  11. Measured depth-dependence of waveguide invariant in shallow water with a summer profile.

    Science.gov (United States)

    Turgut, Altan; Fialkowski, Laurie T; Schindall, Jeffrey A

    2016-06-01

    Acoustic-intensity striation patterns were measured in the time-frequency domain using an L-shaped array and two simultaneously towed broadband (350-650 Hz) sources at depths above and below the thermocline under summer profile conditions. Distributions of the waveguide invariant parameter β, extracted from the acoustic striation patterns, peak at different values when receivers are above or below the thermocline for a source that is below the thermocline. However, the distributions show similar characteristics when the source is above the thermocline. Experimental results are verified by a numerical analysis of phase slowness, group slowness, and relative amplitudes of acoustic modes.

  12. Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation

    CERN Document Server

    Laiho, K; Schlager, A; Suchomel, H; Höfling, S; Kamp, M; Schneider, C; Weihs, G

    2016-01-01

    We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain and provide an important feedback for designing such sources, especially in the broadband case.

  13. Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation

    Science.gov (United States)

    Laiho, K.; Pressl, B.; Schlager, A.; Suchomel, H.; Kamp, M.; Höfling, S.; Schneider, C.; Weihs, G.

    2016-10-01

    We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons, we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain, and provide important feedback for designing such sources, especially in the broadband case.

  14. Nanoconcentration of Terahertz Radiation in Plasmonic Waveguides

    CERN Document Server

    Rusina, Anastasia; Nelson, Keith A; Stockman, Mark I

    2008-01-01

    Recent years have seen an explosive research and development of nanoplasmonics in the visible and near-infrared (near-ir) frequency regions. One of the most fundamental effects in nanoplasmonics is nano-concentration of optical energy. Plasmonic nanofocusing has been predicted and experimentally achieved. It will be very beneficial for the fundamental science, engineering, environmental, and defense applications to be able to nano-concentrate terahertz radiation (frequency 1 - 10 THz or vacuum wavelength 300 - 30 microns). This will allow for the nanoscale spatial resolution for THz imaging and introduce the THz spectroscopy on the nanoscale, taking full advantage of the rich THz spectra and submicron to nanoscale structures of many engineering, physical, and biological objects of wide interest: electronic components (integrated circuits, etc.), bacteria, their spores, viruses, macromolecules, carbon clusters and nanotubes, etc. In this Letter we establish the principal limits for the nanoconcentration of the...

  15. Broadband SHF Direction-Finder

    Directory of Open Access Journals (Sweden)

    S. Radionov

    2008-06-01

    Full Text Available The original design of the compact broadband direction-finder is presented in this paper. The cylindrical monopole antenna serves as a primary source of the reflector- type antenna. "Zero-amplitude" technique is used for bearing the SHF sources. The model experiments with the proposed direction-finder prototype in the frequency band 6 GHz - 11 GHz have been carried out.

  16. Broadband Loaded Cylindrical Monopole Antenna

    OpenAIRE

    Boucher, Solene; Sharaiha, Ala; Potier, Patrick

    2013-01-01

    Ahstract-A broadband printed monopole antenna based on the variation of the conductivity along its length is proposed .. The result indicates that a non-monotonous repartition provides interesting performances in terms of impedance bandwidth but also concerning antenna gain. The achievement of the method is demonstrated through its application, using the carbon fibers to perform this conductivity variation. Monopole antenna presents a large impedance bandwidth of 123% with an interesting gain...

  17. Three-dimensional THz lumped-circuit resonators.

    Science.gov (United States)

    Todorov, Yanko; Desfond, Pascal; Belacel, Cherif; Becerra, Loïc; Sirtori, Carlo

    2015-06-29

    Our work describes a novel three dimensional meta-material resonator design for optoelectronic applications in the THz spectral range. In our resonant circuits, the capacitors are formed by double-metal regions cladding a dielectric core. Unlike conventional planar metamaterials, the electric field is perpendicular to the surface and totally confined in the dielectric core. Furthermore, the magnetic field, confined in the inductive part, is parallel to the electric field, ruling out coupling through propagation effects. Our geometry thus combines the benefit of double-metal structures that provide parallel plate capacitors, while maintaining the ability of meta-material resonators to adjust independently the capacitive and inductive parts. Furthermore, in our geometry, a constant bias can be applied across the dielectric, making these resonators very suitable for applications such as ultra-low dark current THz quantum detectors and amplifiers based on quantum cascade gain medium. PMID:26191695

  18. Three-dimensional THz lumped-circuit resonators.

    Science.gov (United States)

    Todorov, Yanko; Desfond, Pascal; Belacel, Cherif; Becerra, Loïc; Sirtori, Carlo

    2015-06-29

    Our work describes a novel three dimensional meta-material resonator design for optoelectronic applications in the THz spectral range. In our resonant circuits, the capacitors are formed by double-metal regions cladding a dielectric core. Unlike conventional planar metamaterials, the electric field is perpendicular to the surface and totally confined in the dielectric core. Furthermore, the magnetic field, confined in the inductive part, is parallel to the electric field, ruling out coupling through propagation effects. Our geometry thus combines the benefit of double-metal structures that provide parallel plate capacitors, while maintaining the ability of meta-material resonators to adjust independently the capacitive and inductive parts. Furthermore, in our geometry, a constant bias can be applied across the dielectric, making these resonators very suitable for applications such as ultra-low dark current THz quantum detectors and amplifiers based on quantum cascade gain medium.

  19. 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

  20. Sweep Distortion Removal from THz Images via Blind Demodulation

    CERN Document Server

    Aghasi, Alireza; Redo-Sanchez, Albert; Romberg, Justin; Raskar, Ramesh

    2016-01-01

    Heavy sweep distortion induced by alignments and inter-reflections of layers of a sample is a major burden in recovering 2D and 3D information in time resolved spectral imaging. This problem cannot be addressed by conventional denoising and signal processing techniques as it heavily depends on the physics of the acquisition. Here we propose and implement an algorithmic framework based on low-rank matrix recovery and alternating minimization that exploits the forward model for THz acquisition. The method allows recovering the original signal in spite of the presence of temporal-spatial distortions. We address a blind-demodulation problem, where based on several observations of the sample texture modulated by an undesired sweep pattern, the two classes of signals are separated. The performance of the method is examined in both synthetic and experimental data, and the successful reconstructions are demonstrated. The proposed general scheme can be implemented to advance inspection and imaging applications in THz ...