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Influence of THz waves resonant to molecular vibrations to coherent Raman signal is studied by using THz time-domain coherent Raman spectroscopy. Enhancement of coherent Raman signal in THz region is observed depending on the intensity and polarization of irradiated THz waves.
We present a novel photoconductive terahertz source that can generate high power and broadband terahertz radiation with high optical-to-terahertz conversion efficiency. The high optical-to-terahertz conversion efficiency is achieved by confining the optical pump photons very tightly around the radiating elements of the photoconductive source. A distributed Bragg reflector and plasmonic nanostructures...
Approaches towards a linear THz accelerator technology based on a novel multilayer waveguid structure, are discussed. Theoretical and first experimental results on laser based THz generation, guns, accelerators as well as compact X-ray sources based on those devices are presented.
The photo-thermal effects of plasmonic nanoparticles are promising for cancer therapies. These treatments would greatly benefit from real time, multi-scale temperature mapping by non-invasive means. Here we show that intense terahertz time domain spectroscopy can be used as a non-contact and high resolution thermometer of water solutions. Using this technique we measure the temperature change, triggered...
Using degenerate four-wave mixing (DFWM), we have investigated the coherent polarization between the lowest Landau levels in graphene under resonant excitation with narrowband THz pulses. A pronounced DFWM signal is observed and its dependence on THz field strength and magnetic field detuning is explored and compared with theoretical expectations.
We experimentally demonstrate linear frequency conversion on time-variant terahertz (THz) metasurface. The proposed metasurface is originally designed to have two resonances, and with optical pumping, the resonances are merged into one. When a THz pulse passes through the metasurface during this merging process, a frequency component corresponding to the merged mode is generated.
We report the time-profile of the THz wave from GaAs-based photovoltaic devices depending on its structure. Bias dependence of the THz waveforms indicates that the picosecond drift current depends on the device structure even with the same depletion layer condition. This result is critical for the photovoltaic device characterization with the measurement of the THz radiation.
We characterized the terahertz emission from a thin metal film with quasi-randomly distributed porous nanostructures. Unlike many demonstrated nanostructured metal terahertz sources, the emission is in the forward direction when the laser excitation illuminates the metal film at normal incidence, making its integration in a time-domain terahertz system straightforward. We attribute the generation...
We synthesized an ultrathin, nonlinear, optical OH1 crystal structure suitable for prism-coupled Cherenkov phase-matching terahertz (THz) wave generation. Physical vapor deposition was used to grow the crystal to a few micrometers thick. We observed THz wave generation from the thin-film crystal and characterized the crystal structure.
We examined the effect of material dispersion in nonlinear crystals, waveplate, and plasma to the generation efficiency of ultrabroadband coherent infrared pulses from two-color pumped air plasma. We attribute the mechanism for intensity enhancement, which enabled the coherent detection over the frequency range of 1–200 THz, to the optimized polarization, group delay, and minimized dephasing between...
The W-band signal near the antenna surface is detected using a THz probing system, by assuming near/far electric field distribution measurement on a phased array antenna coupled to an RoF radar system. By using 10 GHz + 12.5 kHz optical sampling pulse with a ZnTe EO probing head, the 80-GHz signal generated by a UTC-PD could be successfully detected as a down-converted signal of 100 kHz. It suggests...
We present the study of generation mechanism of terahertz (THz) radiation from tightly focused femtosecond laser pulses in a gas medium. The analysis of the experimental data led to the assumption that the dipole radiation prevails in most cases despite the existing conception regarding the dominating role of the quadrupole mechanism of radiation.
The optical excitation effect on the transmission of a terahertz pulse through aligned silver nanowires on a silicon substrate was studied. Terahertz pulses almost pass through the silver nanowires without optical excitation. However, the optically excited sample significantly reduces the transmittance, comparing with the excited silicon substrate only.
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