The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Two backward wave oscillator (BWO) designs are proposed for a 346 GHz source for fusion plasma diagnostics applicable for the MAST and NSTX-U devices. Both designs feature a double grating machined from bulk copper, using nano-machining technology.
A novel beam scanning antenna in 0.2 Terahertz band based on frequency-scanning grating-reflector was studied in this paper. A bilayer structure is introduced and optimized to improve the diffraction efficiency and to suppress the specular beam. The frequency-controlled beam steering concept was verified by the quasi-optical measurements in 0.2THz band. The measured scanning range is 13.55° over the...
To improve the coupling efficiency of Quantum Well Infrared Photo-detector (QWIP), a new grating was proposed. By optimizing the grating, it can work in 3∼5µm and realize an enhanced peak at 4.5µm. With the uniform result of simulation and experiment, an optimizing metallic grating was designed.
In this paper, with the help of a two-dimensional (2D) particle-in-cell (PIC) code, a simulation of Smith-Purcell (SP) radiation from the dielectric loaded grating is performed in the terahertz regime. The results show that the SP radiation frequency is in good agreement with the theoretical curve. Comparing with the general grating, the usage of dielectric loaded grating enhances the evanescent wave,...
We present a series of aspherical lenses and diffraction gratings 3D printed for use as optical components in terahertz spectroscopy systems. Commercially available plastics for 3D printing (VisyJet Crystal, Acrylonitrile Butadiene Styrene (ABS) Plastic and acrylic based polymers) have also been characterized via Terahertz Time Domain Spectroscopy (TDS) and two-color wave photomixing. In addition,...
We present a high-efficiency photoconductive terahertz source based on three-dimensional plasmonic contact electrodes. We experimentally demonstrate 105 μW broadband terahertz radiation in 0.1–2 THz frequency range in response to a 1.4 mW optical pump, exhibiting a record-high optical-to-terahertz conversion efficiency of 7.5%
Phase grating structure has the ability to converge light. We have introduced it to couple with superconducting nanowire single photon detector (SNSPD) to enhance its response for light. The effects of the coupling structure parameters on the enhancement have been studied systematically by FDTD method. Our numerical simulation show that the optical density arriving on nanowires of SNSPDs can be enhanced...
A monolithic tunable single mode terahertz quantum cascade laser source based on intra-cavity difference frequency generation with a tuning range of ∼580 GHz is demonstrated at room temperature.
We propose a method to generate THz vector Bessel beams by converting spoof surface plasmon polaritons into a series of backward radiation titled towards the optical axis using a concentric metal corrugation structure. The proposed method enables replacing a conventional bulky axicon lens with a flat device and contributes to the implementation of integrated THz systems.
We report an observation of cavity modes in a grating plasmonic cavity sandwiching a QWIP in the wavelength range of 10–13 μm. The normal incident light is squeezed into the 0.9 μm-thick subwavelength cavity to form standing wave modes, causing the QWIP photocurrent responses to be 25-fold enhanced comparing with its 45-degree coupled counterpart. The cavity modes are recognized to be localized surface...
We present room-temperature broadly tunable external cavity terahertz sources based on Cherenkov intra-cavity difference frequency generation in mid-infrared quantum cascade lasers bonded with Si substrate. Laser chips are integrated into a Littrow-type external cavity system. Devices demonstrate continuous THz emission tuning from 1.2 THz to 5.9 THz at room temperature with peak power output varying...
This study is aimed at development of a moderate power sheet-beam traveling wave tube (TWT) amplifier with grating slow-wave structure (SWS). A fast and accurate code for calculation of eigenwaves in the grating SWS is developed, and results of numerical modeling of a G-band TWT are presented. Electron gun producing an intensive sheet electron beam is developed. Beam focusing and transportation is...
Surface plasmon polaritons at the n-GaN/vacuum interface are investigated. Experimental studies of terahertz radiation reflection and emission are performed on heavily silicon-doped GaN epitaxial layers grown on sapphire substrates. To provide interaction of THz radiation with the surface plasmon polaritons, a regular grating was fabricated on the outer surface of the epitaxial layer. Study of terahertz...
Reflection phase gratings offer great potential as local oscillator beam multiplexers in THz imaging heterodyne receivers. Using the Lagrange's multipliers method, we have optimized the phase profiles to achieve high diffraction efficiencies for three, four and five beam linear multiplexers. Experimental results at 2.5 THz are reported for a three-beam bulk aluminum multiplexing device.
We implement optical pulse shaping into a photo-conductive antenna (PCA) based THz time domain spectroscopy (THz-TDS) system using fiber coupling between emitter and pulse shaper. We use phase-only pulse shaping for the generation of bit patterns. An additional phase mask is applied in the pulse shaper to cancel dispersion introduced by the optical fiber. The generated waveforms are coupled into a...
We report on room-temperature plasmonic detection of the thermal emission from a black body in the terahertz and mid-infrared domains by dual-grating-gate InAlAs/InGaAs/InP high electron mobility transistors (HEMTs). In such detectors, the asymmetric grating gate of a large area acts as an effective antenna that improves the performance in the two spectral domains.
We demonstrate an ultra-broadband all-optical terahertz modulator based on a semiconductor-integrated hybrid metamaterial. Under photoexcitation using near-infrared laser pulses, the semiconductor regions become highly conducting, causing a transition of the metamaterial from an array of dipole patch grid to a metal wire grating. This transition exhibits dramatically different transmission properties...
A beam splitter based on the concept of a reflectarray is designed for polarization-dependent bidirectional deflection at 1 THz. A unit cell is composed of two sets of orthogonally oriented dipole resonators arranged in an interlaced triangular lattice. A subarray is constructed from multiple unit cells to create two independent progressive phase distributions to respond to the TE and TM polarized...
We describe a two-dimensional imager in W-band using a single heterodyne transceiver and no mechanical scanning. By using an echelle grating spectrometer, frequencies are mapped onto a 2-D surface in space, so that spectral analysis of the signals provides a two-dimensional image.
We demonstrate a low-loss terahertz waveguide Bragg grating (TWBG) fabricated using a plasmonic two-wire waveguide and a micromachined paper grating for potential applications in THz communications. Two TWBGs were fabricated with different periods and lengths and investigated experimentally. TWBG modal dispersion relations, modal loss, and field distributions were studied numerically. Additionally,...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.