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We report optical coherent control of the emission direction of THz radiation by excitation of bulk GaAs with femtosecond laser pulses. Changing the phase of the optical excitation, steering angles of ∼8 degrees are realized. A simple model is introduced to analyze the underlying parameters.
We present our results on THz pulse generation in the 0.1–2.5 THz band via optical rectification of femtosecond laser pulses in a tapered crystal. A simulation study for visualization of THz wave propagation in the crystal has been performed. It is shown that the mode structure and phase velocity of the THz wave in the crystal are changed.
We present broadband difference frequency generation into the mid-infrared based on a femtosecond dual-signal-wavelength optical parametric oscillator for near-field microscopy applications as well as a high-repetition-rate optical parametric amplifier for FTIR spectroscopy applications.
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.
Spectroscopic ellipsometry based on terahertz time-domain spectroscopy was used for non-contacting evaluation of SiC epilayers homo-epitaxially grown on opaque SiC substrates. The thickness, carrier density and scattering time of the epilayers were simultaneously determined.
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 THz spectrometer based onto the photomixing technique associated with a femtosecond frequency comb is a perfect tool for the study of radicals, which usually required a very large tunability. The spectra of OH, SH and SO have been revisited and updated data have been obtained.
We present an ultrafast dynamics of THz graphene-metamaterial hybrid devices, where the refractive index and the conductivity are largely modulated by electrical and optical methods. Unprecedentedly large modulation of refractive index and the pump-induced effective negative conductivity are investigated by an ultrafast time-resolved optical-pump THz-probe spectroscopy with varying gate voltage.
Photoconductive Terahertz microprobes have been crystalized as powerful measurement tools for high-resolution conductivity imaging, chip inspection and near-field imaging applications. In this work we demonstrate their integration into a high-speed system with 250 pixels/s data acquisition rate.
A compact, robust, and portable fiber-coupled THz photoconductive antenna module is described. A new technique is used to focus the output light of the fiber on the chip and fix the fiber in place to provide rugged packaging. THz measurements in pulse mode confirm the performance of this module. The fiber coupled unit is very versatile and can be used in both time domain and frequency domain THz systems...
Complex dielectric susceptibilities of MWCNT/PE composites with various contents of nanotubes were measured using THz-TDS and cw THz BWO-spectrometer in the frequency range 100 GHz – 2.2 THz and THz peak powers from microwatts to hundred kilowatts.
It has been observed that Terahertz (THz) wave was radiated from nanostructured metal gratings and metal films, which was illuminated by femtosecond laser pulse. In this paper, we got more than 60µ J intense single THz pulse, and the maximum spectrum was distributed from 0.3 to 149 THz. Theoretical calculation was performed to explain the generation mechanism.
We measured terahertz (THz) emission from the vertically aligned indium arsenide (InAs) nanowires using THz time-domain spectroscopy. The photoexcited InAs nanowires were grown by metalorganic chemical vapor deposition on type <111> silicon substrate. Experimental results shows that THz emission mechanism of InAs nanowires are very different from that of bulk InAs substrates.
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 propose and demonstrate electro-optic (EO) sampling of terahertz (THz) radiation by using GaAs in the Cherenkov phase-matching scheme. This technique can be implemented without Si-prism coupling due to a small difference between optical group and THz phase refractive indices of GaAs and its low THz absorption.
We demonstrate in the experiment and simulations that interference between two contributions into the terahertz wave generation in a femtosecond filament, namely, the free electron photocurrent and the nonlinear polarization of neutrals, can be used for the femtosecond coherent control of the THz spectra.
We report on the coherent control of terahertz (THz) spin waves in a canted antiferromagnet, YFeO3, associated with a quasi-ferromagnetic spin resonance at a frequency of 0.3 THz, using a single THz pulse. The intrinsic dielectric anisotropy of YFeO3 in the THz range allows for coherent control of both amplitude and phase of the excited spin wave.
We demonstrate all-optically induced real-space charge transfer in semiconductors, which reverses its direction upon a change of the temporal order of two excitation fields. Such charge transfer leads to a new type of photocurrent and only appears for certain polarization-shaped optical pulses while it ceases for continuous-wave excitation.
We experimentally demonstrate CEP-sensitive nonlinear transmission spectroscopy in high-Tc superconductor YBa2Cu3O7−x (YBCO) thin film. The above-threshold current changes strongly influence the THz nonlinear responses, which reveal the inherent material properties in condensed matters.
We demonstrate the combination of phase-only optical pulse shaping and terahertz time domain spectroscopy. Temporal delay of pulses and generation of bit patterns is shown.
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