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Terahertz (THz) light helicity sensitive photoresponse in GaAs/AlGaAs high electron mobility transistors and silicon metal oxide semiconductor field effect transistors is reported. The helicity dependent detection mechanism is interpreted as an interference of plasma oscillations in the channel of the field-effect-transistors (generalized Dyakonov-Shur model). The observed helicity dependent photoresponse...
We report on time-resolved photoluminescence of excitons and electron-hole plasma in GaAs quantum wells under intraband excitation by a free-electron laser in resonance with intersubband and intraexcitonic transitions, respectively, to study relaxation and intraexcitonic scattering.
We report a gate-voltage-controlled terahertz (THz) detector based on a two-dimensional electron gas (2DEG) field-effect transistor. The electron density of the 2DEG can be varied with the gate voltage. In this way, we controlled the amplitude of the THz detected signal by the gate voltage, indicating the role of the external switch for the THz detection.
We compare the photocarrier lifetime measured in Br-irradiated InGaAs and cold Fe-implanted InGaAsP. We also demonstrate the possibility of a two-photon absorption (TPA) process in ErAs:GaAs. The lifetime and the TPA were measured with a fiber-based 1550 nm time-resolved differential transmission (?T) set-up. The InGaAs-based materials show a positive ?T with sub-picosecond lifetime, whereas ErAs:GaAs...
Photoconductive switches have been extensively studied in time domain spectroscopy (TDS) as THz sources/ detectors. The commonly used devices consist of metal-semiconductor-metal (MSM) structure where Gallium Arsenide (GaAs) is the active layer. In this work, an approach consisting of using semiconducting single-walled carbon nanotubes (s-SWCNTs) instead is proposed. The pristine results showing the...
We present characteristics of terahertz pulses generated from GaAs surfaces with disordered nano-pillars under femtosecond laser excitation. Nano-pillars on a GaAs surface decreases (increases) a temporal (spectral) bandwidth of a THz pulse from the surface. The results imply that randomly distributed scattering sites due to the nanostructures make the decay time of photo-carriers short and reduce...
This paper presents a theoretical investigation on a THz pulse shaping method based on difference frequency generation of two orthogonally polarized optical pulses. This scheme is effective in controlling the amplitude and polarization of generated THz pulse. The power spectrum from ZnTe, GaAs and GaP crystals is compared when considering crystal absorption and phase mismatching condition. Simulation...
Several options for THz emitters and detectors operated at pump wavelengths around 1560 nm were investigated. Results from photoconductive antennas on In0.53Ga0.47As-based epilayers as well as DAST crystals are presented. Furthermore, the use of standard LTG GaAs antennas without frequency doubling is explored.
Surface THz pulse emission from samples containing 40 layers of InAs quantum dots grown on a AlAs/GaAs Bragg reflector as well as the picosecond photoconductivity of devices manufactured from this material was investigated as a function of the optical wavelength of femtosecond pulses generated by an optical parametric amplifier.
It is shown that a continuous wave output power of 0.35 mW at 305 GHz can be generated by photomixing in a low temperature grown GaAs photoconductor using a metallic mirror Fabry-Pérot cavity. The output power is improved by a factor of about 100 as compared to the previous works on GaAs photomixers.
We report on the development and testing of fiber-coupled, LT-GaAs photomixers operating at cryogenic temperatures which are designed for variable temperature terahertz spectroscopy of chemical, electronic and magnetic materials.
One possible way to realize high-temperature operation of terahertz quantum cascade lasers (THz-QCLs) is to introduce a new semiconductor material system instead of GaAs/AlGaAs. It is important to take into account not only longitudinal optical (LO) phonon energy of the material but broadening of subband levels caused by LO phonon-electron interaction. We propose a AlP/GaP-based THz-QCL structure...
We present a new measurement technique for the sub-Kelvin excitation and detection of on-chip terahertz frequency radiation in high magnetic fields. We present a monolithically integrated heterostructure, which allows a mesoscopic electronic system to be combined with an on-chip terahertz device, and show dynamic imaging of a THz photoconductive switch at 200 mK in a 12 T field, together with THz...
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