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We have quantified the ultrafast birefringence induced in air plasma by measuring the THz-field-induced second harmonic (TFISH) along two orthogonal directions with THz air-biased-coherent-detection technique. The time domain TFISH waveforms and polarization state were measured under different polarizations of fundamental wave. The measured polarization state of the TFISH agree well with predictions...
We present the results of calculation and experimental testing of the tunable wavelength terahertz polarization converter (TWPC) represented by set of planeparallel birefringent plates with in-plane birefringence axis. An experimental device has been produced and tested. The calculations show that the effect of interference between the interfaces, including air gaps, may be neglected. Considered device...
We present a theoretical model for the tilted-pulse-front-pump scheme to generate terahertz pulses, and used it to analyze the polarization state of the terahertz pulse. The result indicates that one can change the polarization state of terahertz pulse by changing the polarization of the pump beam.
Recent simulation and experimental work has resulted in the realization of low-cost, substrate-based, THz wire-grid polarizers fabricated on crystalline-quartz substrates that exhibit both high extinction ratios and low insertion losses. The broad bandwidth performance of these high fill-factor wire-grid polarizers are characterized using terahertz time-domain spectroscopic techniques over a frequency...
A dimer is the simplest form of cluster that exhibits some of the salient properties resulting from coupling interactions between the particles. The semiconductor nanodimer is a self-contained nanostructure supporting the intensification of the local electric field as a result of plasmon resonance and proximity effects. By means of a simulation framework based on charge transport analysis for the...
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 general theory for the pump polarization angle dependence of optical rectification has been constructed. Measurements have been taken of a 112A GaAs sample and compared to this theory. The terahertz radiation generated is a mixture of bulk (second order) and surface (third order) contributions. From this data, and a previous investigation into the azimuthal angle dependence of these samples, a value...
This contribution presents the progress towards developing an analytical electromagnetic tool for the characterization of THz antenna arrays under focusing systems.
Design considerations for an off-axis parabolic mirror based THz imaging systems are presented. The distortion of THz field and its polarization profile are shown for two different configurations of off-axis parabolic mirror trains. The field and polarization distortions along the propagation path are compared with different f/# mirrors. The distortion effects were cancelled out by symmetric orientation...
We study THz radiation from magneto-optically induced ultrafast currents in GaAs. Magnetic field and excitation intensity are found to have a distinct influence on the shape of the THz traces. The results suggest that these currents are an appropriate tool to investigate k-space carrier dynamics in semiconductors.
We recently demonstrated ultrathin, broadband, and highly efficient (reaching 88%) terahertz (THz) metamaterial structures exhibiting near-perfect anomalous (or generalized laws of) refraction. These structures redirect up to 61% of the incident power into the anomalous beam and practically eliminate the ordinary component. Here exploit this breakthrough to create more complex optical elements, specifically...
We investigated the transmittance of terahertz (THz) pulses through organic copper phthalocyanine (CuPc) thin films deposited on a Si wafer under optical excitation by varying the polarization and incident angle of the excitation. The photo-carrier induced THz transmittance modulation reflects the angle-dependent reflectivity of the CuPc thin films and the birefringence induced by the charge density...
Interpretation of the vector waveform detected by using the electro-optic (EO) sampling method in the terahertz time-domain spectroscopy is presented, especially when there is a velocity difference between the elliptically-polarized terahertz pulse and the optical probe pulse in the EO crystal. The formulation can be used to interpret the time-domain vector waveform detected by the EO sampling method...
After passing quarter of a century from its discovery, terahertz time-domain spectroscopy (THz-TDS) has made great progress and is expected to be applied to various fields from basic science to security and industry. I will review our contribution to the development and applications of THz-TDS including recent results.
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