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.
Sub-terahertz and terahertz frequencies can be generated by optical heterodyning of two wavelengths. Two laser modes, generated with a Photonic Integrated Circuit which integrates an Arrayed Waveguide Grating, are employed to create terahertz frequencies. The wavelength difference of the two optical modes defines the frequency of the generated wave, which can be discretely tunable by selecting different...
A Continuous Wave (CW) millimeter-wave photonic synthesizer based on Difference Frequency Generation (DFG) is presented. This system encompasses an Optical Frequency Comb Generator (OFCG), an optical mode selection stage and a high-bandwidth photodetector. The employed OFCG is a novel design based on Gain-Switching modulation of a VCSEL. This new OFCG offers equivalent optical span than commonly employed...
In this manuscript, we present a new antenna topology applied to the so called THz gap, based on using a dielectric rod antenna avoiding the use of the classical lens for collimating the emitted/received power. The scope and future perspective of the manuscript is beyond this idea: we develop this topology with the perspective of being the optimum antenna system to be coupled in a THz waveguide easy...
Following an established concept of IR spectroscopy, the total absorber was transferred to the THz wavelength. This allows for measurement of effects interesting for life-science applications like DNA hybridization and molecular resonances. The complete process from simulations to measurements will be addressed.
The results of investigation of terahertz generation in Al0.2Ga0.8As nanowires by the optical excitation of femtosecond pulses are presented. It is shown that the radiation is generated by excitation of photocarriers in nanowires. The time-resolved dynamics of photocarriers were studied by optical-pump terahertz generation-probe time-domain spectroscopy.
We present a review of pioneering database on terahertz spectroscopy. The database has been opened universally since 2008 and is restructured recently based on the contemporary HTML5 technology. Flexibilities to browse and search data are much improved. Besides, data upload system from general users is prepared to enrich the database further.
We report on the experimental and theoretical study of the Reststrahlen Band assisted photocurrents in epitaxial grown graphene on SiC. We show that excitation of graphene with infrared radiation results in a dc current. We demonstrate that photocurrent in response to linearly polarized radiation exhibit a resonance enhancement in the frequency range of the Reststrahlen Band of the SiC substrate....
A new terahertz fiber using polymer tube bundle with triangular structure is proposed and analyzed. An optimum tube parameters in bundle structure for low loss waveguide is clarified.
The efficiency of hot carrier multiplication in monolayer graphene was studied using optical pump-THz probe spectroscopy. An energy conversion efficiency from photon to hot electrons exceeding 75 % was found.
We present high-performance terahertz intensity modulators based on a new class of reconfigurable meta-surfaces that offer extreme diamagnetic switching capability over a broad frequency band. We experimentally demonstrate record high modulation depths (> 70%) and modulation bandwidths (> 1.5 THz) through a fully integrated platform at room temperature.
A terahertz metamaterial comprised of C-shaped SRRs was experimentally devised and demonstrated to exhibit high-efficient and broadband anomalous refraction with strong phase discontinuities. The generalized refraction properties of the proposed metamaterial, including the effect of various incident angles and polarizations were investigated at broad terahertz frequencies. By employing such metasurface,...
Here, we report on planar photonic transmitters employing high-speed 1.55 µm photodiodes. Within the 200–300 GHz band, the device exhibits a 6-dB bandwidth along with a polarization penalty of ∼2.2 dB. Besides, the chip area is reduced thanks to a novel integration approach in the antenna structure.
Terahertz emitters and detectors made from AIIIBV semiconductors were investigated by means of a tunable wavelength laser system. THz excitation spectra of InAs and InSb has been investigated. It was shown that subsidiary valley position can be determined quite accurately. As terahertz detectors, the photoconductors manufactured from GaAs and InGaAs epitaxial layers grown by MBE at low substrate temperatures...
We report a continuously tunable dual-wavelength laser based on the polymer Bragg gratings for continuous wave terahertz optical beat source generation. The polymer Bragg gratings are used to wavelength selective components in the laser cavity. The measured wavelength tuning range is about 19 nm. The side mode suppression ratio is achieved more than 30 dB for dual wavelength.
This paper reviews different mechanisms of saturation in SIS mixers and presents results of the modeling and experimental verification of the proposed solution to increase the saturation level by de-tuning the SIS mixers, to allow solar observations with ALMA.
We present numerical modeling and experimental results demonstrating strong spatial scattering of THz radiation from a randomly micro-structured air-polymer composite material. Such materials could be used as a THz diffuser.
We present a substrate integrated waveguide (SIW) antenna designed for 60 GHz indoor Radio-over-Fiber photonic transmitters. For broad-band applications (57–64 GHz) a return loss (RL) higher than 7 dB and a front-to-back ratio (FTBR) of 17 dB are achieved. Alternative resonant solutions are also introduced to achieve RL > 10 dB and FTBR = 21 dB.
The user FELIX Facility Nijmegen offers four FEL beam lines, FLARE from 0.2 to 3 THz, FELIX-2 from 12 to 75 THz, FELIX-1 from 2 to 12 THz and FELICE, a special beam line for intra-cavity experiments from 3–75 THz
Optimal control of the output energy of terahertz wave generated by optical rectification in ZnTe crystals is reported. An enhancement by factor up to 2.4 is reported. Two-photon absorption and spectral phase effects on the THz generation efficiency are numerically investigated and discussed.
We report nonlinear terahertz effects in monolayer graphene using intense few-cycle THz pulses. We observe enhancement in the THz transmission through graphene when we increase the THz electric field. Following photo-excitation, we observed reduction in the THz transmission. This photo-induced reduction in the THz transmission is found to decrease when we increase the THz electric field.
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.