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We present a collection of new, low cost quasi-optical devices for the terahertz range. This includes a liquid-filled lens with variable focus length, lenses and transmission gratings made from micro powders, wave plates made from ordinary copy paper, and an electrically tunable notch filter.
Unusual enhancement of mid-infrared light emission from CdTe/PbTe heterostructures is observed. It is discovered that the observed intense mid-infrared luminescence in the structures comes from the inherent polar interface character and coupling of surface plasmons localized at the metallic CdTe/PbTe interface to light emitted from the narrow gap PbTe.
We report a W-band backward-wave oscillator using micro-fabrication technologies by which a fully 3-dimensional slow-wave interaction circuit is successfully employed on multi-bonded silicon wafers. MEMS (micro-electromechanical systems) technologies such as deep RIE (reactive ion etching) and thermocompressive hermetic bonding are applied to achieve highly accurate dimensional structures for high...
We present a systematic analysis of geometry-dependent parasitics for THz sub-harmonic Schottky mixer diodes. In particular, the diode RF power coupling bandwidth has been studied, showing a trade-off between the air-bridge finger length and finger separation for operating frequencies beyond 1 THz.
We have built a 2SB mixer, which has demonstrated a sideband rejection ratio as high as 15 dB over the full band of 600–720 GHz and the SSB noise temperature between 200 and 370 K. Both sideband ration and noise temperature are well within the ALMA specifications.
We report on terahertz emission from n-GaN films under steady state interband photoexcitation at low temperatures. The properties of the terahertz photoluminescence allow us to conclude that the emission occur under capture of nonequilibrium electrons to ionized donor centers.
We report on the analytical capacity analysis of terahertz wireless communications supporting 275–325 GHz frequency band. Our goal in this paper is to provide design guidelines for close proximity links with transmission capacity beyond 100 Gbit/s.
We report a very compact, laser diode-pumped, frequency-tunable THz source (1.65 – 2.65 THz) based on Stimulated Polariton Scattering in Mg:LiNbO3. The system operates with very low threshold (∼ 2.5 W diode pump power) and outputs a maximum average power of 6.45 µW at 2 THz, at a pulse repetition frequency of 3 kHz.
The propagation of THz waves on a single metallic strip will be presented. The properties and basic applications of this Planar Goubau- Sommerfeld Line (PGSL) will be shown. For example one can realize filters in different ways. The topology of this line is well suited for the excitation of metamaterial's unit cell like split ring resonators (SRR) [1]. We can also take benefit of the propagation on...
Using a cavity based on a periodic-surface-lattice (PSL) the concept of a high-power, 200GHz Cherenkov source is developed. If the PSL satisfies certain defined conditions single mode operation is observed.
Density functional theory calculations of its crystal elucidated that the absorption peaks of perylene 3,4,9,10-tetracarboxylic dianhydride in the THz region are caused by the frequency shift and the peak splitting of the in-phase and out-of-phase vibrations of two molecules in a crystal unit cell. Crystal-packing interactions are found to enable IR-inactive vibration in isolated molecules to become...
In this work, a reflectarray operating at 1 THz is designed and implemented using metal-dielectric resonant patch elements. The dimensions of the single elements are optimized through simulation to achieve a wide range of the reflection phase change. Based on the relation between the phase change and the patch size, the terahertz reflectarray is built up to function as a reflector deflecting an incident...
Sample preparation of pharmaceuticals for THz spectroscopy has much importance, as the THz spectra are often highly sensitive to crystal and/or molecular structure changes. In this study, nondestructive sample preparations will be proposed and examined.
We fully interpolated frequency gaps between THz comb modes by tuning mode-locked frequencies in dual fiber lasers used for generation and detection of THz comb. The resulting gapless THz comb implies a possibility to enhance the spectral resolution in THz spectroscopy down to the linewidth of each comb mode.
Vibrational spectroscopic analysis of theophylline in a wet granulation process was performed. An anhydride was converted to a monohydrate during the granulation and a dehydration of monohydrate progressed during the drying process. A C-N stretching would be affected by an interaction between theophylline and a binder under a wet granulation process.
A new detection technique for sampling of terahertz pulses based on heterodyne modulation of an optical probe due to the sum (or difference) frequency mixing is proposed and experimentally demonstrated in the Cherenkov phase-matched scheme using a Si-prism coupled LiNbO3 crystal. In this technique, only the variations in intensity of the sampling optical pulse are measured and no polarization optics...
The present paper describes two kinds of techniques aiming at improving THz imaging for detecting rust under coated steel plates. First, it is revealed that a THz camera considerably shortens the THz-imaging time, but fringe patterns due to high coherence light source sometimes prevent image concatenation. Second, a program flowchart to quantitatively estimate the degradation level of rust is also...
We proposed and demonstrated active control of terahertz optical activity via chiral patterned photo-excitation in a semiconductor with a spatial light modulator. This technique provides a new route to terahertz polarization modulators.
Harmonic transponders used nowadays for tracking small insects impede and obstruct their movements due to their large size and weight. The paper presents millimetre wave band unbiased harmonic transponder. It comprises of separate transmit and receive microstrip patch antennas and unbiased Schottky diode doubler. The transponder is conformal, miniaturized and suitable for short range insect tracking.
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