Pump-wavelength dependence of terahertz radiation via optical rectification in (110)-oriented ZnTe crystal
ABSTRACT The optical pump-wavelength-dependent generation and detection of terahertz wave in (110)-oriented ZnTe crystal were demonstrated. By using femtosecond laser pulses, terahertz radiation was generated. Both simulations and experimental results show that the terahertz wave in the frequency range of about 4–1 THz can be obtained by tuning the pumping wavelength from 700 to 900 nm. The theoretical analysis shows that the matching between the optical group velocity and terahertz phase velocity plays an important role for terahertz frequency tuning. The present studies also demonstrate that both the terahertz generation and detection are applicable in a single nonlinear optical crystal.
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ABSTRACT: The process of terahertz generation through optical rectification in a nonlinear crystal is modeled using discretized equivalent current sources. The equivalent terahertz sources are distributed in the active volume and computed based on a separately modeled near-infrared pump beam. This approach can be used to define an appropriate excitation for full-wave electromagnetic numerical simulations of the generated terahertz radiation. This enables predictive modeling of the near-field interactions of the terahertz beam with micro-structured samples, e.g. in a near-field time-resolved microscopy system. The distributed source model is described in detail, and an implementation in a particular full-wave simulation tool is presented. The numerical results are then validated through a series of measurements on square apertures. The general principle can be applied to other nonlinear processes with possible implementation in any full-wave numerical electromagnetic solver.Optics Express 07/2012; 20(16):18397-414. DOI:10.1364/OE.20.018397 · 3.53 Impact Factor
Photodetectors, 03/2012; , ISBN: 978-953-51-0358-5
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ABSTRACT: We report the optical characterization of low temperature (LT)-GaAs and Semi Insulating (SI)-GaAs based dipole types Photoconductive (PC) antennas with gap of 5 μm for the generation and detection of Terahertz (THz) signals. We have used tunable 140 femto-seconds laser pulses at 80 MHz repetition rate of different power and biasing voltage to evaluate the performance of our antennas as a THz generator and detector. Interestingly, we found that LT-GaAs and SI-GaAs have high photocurrent (density of charge carriers) response at some specific laser wavelengths such as 840 nm and 880 nm, respectively. We have employed these selected wavelengths for the generation and detection of THz radiation from these materials made PC antennas. The comparative study shows that the intensity of THz radiation in case of SI-GaAs is higher than the LT-GaAs made PC antennas. The THz frequency spectrum range of LT-GaAs and SI-GaAs antennas are extended up to 3.6 THz and 2.5 THz respectively. Finally, we have cross verified the reliability of our antennas to detect the THz radiation generated from ZnTe crystal.Optical Materials 01/2014; 36(3):596–601. DOI:10.1016/j.optmat.2013.10.021 · 2.08 Impact Factor