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THz microscopic imaging is used to extract the Gouy phase shift of the transverse and longitudinal field components of a tightly focused, radially polarized beam. We demonstrate that the applied THz time domain approach allows to observe directly the evolution of the geometric phase as the wave propagates through the focus. Our method yields a Gouy phase shift of 2π for the transverse component and...
1-THz continuous-wave signal is generated by an optical frequency comb generator utilized as a 41st-order multiplier. Phase noise characteristics of generated signal are evaluated by heterodyne detector and microwave electrical spectrum analyzer.
Wood exhibits a strong birefringence at Terahertz frequencies. In this paper we show that at specific polarization angles the THz transmission spectra show distinct frequency gaps. We present results for spruce and beech wood with different sample thickness and orientations. We demonstrate that the main effect can be modeled with appropriate values for the refractive index and absorption coefficient...
The motion of spin-polarized carriers in the direction perpendicular to an electrical bias constitutes the anomalous velocity. So far, this phenomenon has been studied in time-integrated spin and anomalous Hall effect experiments. Here, we excite GaAs with optical and terahertz radiation to induce the anomalous velocity on an ultrafast time scale. Studying the shape of the terahertz radiation emitted...
Separating and detecting specific polarisations at multiple frequencies can be required for a number of scientific cases. However, in some cases, constraints on polarisation are defined by the choice of detectors used. In this paper we will present two devices that have been designed and built to increase performance when designing an optical system with these constrains. They are a polarisation sensitive...
Simultaneously oscillated 48-μm and 57-μm CH3OD lasers pumped by a 9R(8) CO2 laser have been developed for fusion plasma diagnostics. A back reflection from an optically pumped far-infrared (FIR) laser cavity affects not only the FIR laser stability but also the pump CO2 laser stability. The back reflection has been reduced by an optical isolator using a quarter-wave plate and an absorbing thin-film...
We present a study on a dolmen structure, where a bright resonator couples to a dark resonator, to investigate near-field signatures of electromagnetically induced transparency. We demonstrate an enhancement of the near-fields in the spectral vicinity of the transparency, and observe mode hybridization resulting from the coupling between the two resonant structures.
We report a significant signal enhancement on the periphery of the probe optical beam in the “heterodyne EO sampling” of pulsed terahertz radiation. Our experimental results coincide with the theoretical prediction. By using this enhancement effect, it is possible to increase the heterodyne EO sampling signal ΔI/I by several folds with optimized detection optics.
We have measured stress distributions in ceramic thermal barrier coatings using reflection-based polariscopes working at GHz and THz frequencies. Such coatings are routinely used in aerospace, automotive and energy applications. Understanding stress distributions within these coatings during manufacture and after use is vital to improving their performance. Stress optic coefficient measurements of...
We report on terahertz radiation from topological insulator (TI) Sb2Te3 thin film under ultrafast optical excitation with different helicity. Polarity-reversals of the emitted THz radiation were observed as the helicity of optical pulses reversed. The observed phenomena are coincident with the characteristics of the helicity-dependent photocurrent on TIs. Our work demonstrates the potential applications...
We explore the third order nonlinear optical conductivity of the bilayer graphene in the terahertz regime where the Rashba spin-orbit coupling interaction is taken into account. It is found that nonlinear optical conductivity of the BLG with ROI is significantly enhanced in comparison with the case without the ROI.
The mid-infrared electroluminescence spectra related to the direct interband electron-hole recombination under impact ionization in strong electric fields are experimentally studied in the InAsSb epilayer and in the monocrystalline n-InSb. The polarization anisotropy of recombination radiation in the monocrystalline n-InSb arising due to electron heating and drift in strong electric fields is observed...
We demonstrate that the spectral analysis of the optical spectrum produced by the interaction of optical and THz pulses in a ZnTe crystal makes it possible to characterize the group delay dispersion of an optical pulse.
THz generation under the excitation by ultrashort optical pulses from ordered arrays of GaAs nanowires is reported. It was found that the efficiency of THz radiation generation increases due to the resonant leaky mode excitation in nanowires. The THz generation mechanisms have been identified. It is shown that the efficiency of the terahertz generation at optimum geometrical parameters of an array...
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