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We have carried out a theoretical and computational study of the nonlinear optical conductance in terahertz to infrared regime of a single layer graphene p-n junction (GPNJ) with intra and inter band transition under moderate electric field. It is shown that the negative connectivity of single layer graphene can be enhanced and affected by the bias voltage. The result can be important to the application...
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.
Gallium Selenide crystals having compositions modified with a range of elements are investigated using THz time-domain spectroscopy, Raman, FTIR and ellipsometry. The optical properties are related to modifications in the crystal structure.
We combine spectrally and spatially resolved measurements of the ultra-broadband THz-mid-infrared (IR) emission from a two-color-excited gas plasma, which provides a more detailed picture of the emission process and allows one to simulate the predicted spatio-temporal propagation through a subsequent focal region.
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 demonstrated fast 3D terahertz computed tomography by using real-time line projection of an intense terahertz beam. Peak-to-peak amplitude of the pulsed terahertz electric field and a standard reconstruction algorithm were used to performed final 3D reconstruction of test samples with a total acquisition time to only 6 minutes.
Results on THz pulse generation in the 0.1–2.5 THz band via optical rectification of femtosecond laser pulses in a wedge crystal are presented. The finite-element method was employed to model and simulate the THz wave propagation in a LiNbO3 wedge antenna in order to analyze experimental results; and to visualize how the form of the crystal influences the THz radiation both inside and outside the...
The intrinsic linewidth of Surface Plasmon Polariton resonance in a micrometric metal mesh has been measured with a collimated mid-infrared beam, provided by an External-Cavity, tunable Quantum Cascade Laser. The use of a collimated beam yields a resonance linewidth of 12 cm−1, much narrower than by conventional black-body sources. This opens more favorable perspectives to the use of metal meshes...
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.
Terahertz induced Kerr effect in a (100) GaP crystal is reported. The measured dependence of the optical birefringence with respect to the azimuthal orientation of the crystal agrees with theoretical calculations. Additional electro-optic contribution to the detected signal is observed and attributed to crystal abnormity.
A high-efficiency etalon operated in the THz region has been proposed to generate a THz pulse train. To achieve high-conversion efficiency to the pulse train, an optical shutter is employed in this etalon. A THz pulse train and its comb-shaped spectrum have been realized by the use of the proposed etalon with the optical shutter.
Laser driven terahertz radiation sources have been developed to enable energy modulation of relativistic electron bunches on a sub-picosecond timescale. Photoconductive and nonlinear optical generation schemes capable of providing the required > 1MV cm−1 field strengths, and longitudinal polarisation components, are discussed.
Upon femtosecond laser pumping of a topological insulator Bi2Se3, we observed efficient THz generation from the surface electrons. By performing polarization-resolved studies on the emitted THz spectrum, two emission mechanisms are identified. THz emission spectroscopy provides a valuable spectroscopic tool for studies of the dynamics of the surface electrons in centrosymmetric topological insulators.
We report nonlinear terahertz effects in monolayer graphene using intense few-cycle THz pulses. We observe enhancement in the THz transmission through graphene when we increase the THz electric field. Following photo-excitation, we observed reduction in the THz transmission. This photo-induced reduction in the THz transmission is found to decrease when we increase the THz electric field.
We demonstrate efficient generation of narrowband (< 100 GHz) THz pulses in the nanosecond range by using difference frequency generation in organic electro-optic crystals DSTMS and OH1. The terahertz output is tunable in the range of 1–20 THz and can be used for THz imaging and spectroscopy.
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