THz generation by optical rectification of near-infrared laser pulses in the organic nonlinear optical crystal HMQ-TMS

We show that the organic electro-optic crystal HMQ-TMS [2-(4-hydroxy-3-methoxystyryl)-1-methylquinolinium 2,4,6-trimethylbenzenesulfonate] has favorable properties for the parametric generation of THz waves in a collinear type-0 phase-matching scheme, i.e., a low absorption coefficient at wavelengths from 800 to 1500 nm (alpha < 1.5 cm(-1)), a relatively low absorption coefficient at frequencies from 0.3 to 1.5THz (alpha < 100 cm(-1)), and a large coherence length in these spectral ranges (l(c) > 0.5mm). We demonstrate efficient generation of broadband THz pulses through optical rectification of sub-picosecond laser pulses in a 0.2mm thick HMQ-TMS crystal at the wavelength of 1000 nm. The energy conversion efficiency achieved in this crystal was 41 times higher than the one achieved in a 0.3mm thick GaP crystal, which is an often used material for collinearly phase-matched THz generation at this laser wavelength. The peak amplitudes of the THz signal obtained with the HMQ-TMS crystal were 5.4 times larger in the time-domain and 7.1 times larger in the frequency-domain than the ones obtained with the GaP crystal. (C) 2014 Optical Society of America