High efficiency generation and detection of terahertz pulses using laser pulses at telecommunication wavelengths

We report on the generation and detection of few-cycle THz pulses in the organic crystal DAST (4-N,N-dimethylamino-4'-N'-methyl stilbazolium tosylate) using the telecommunication wavelength 1.5 mum. A continuous spectrum from 1.3 to 4.8 THz was generated with a very high conversion efficiency (E(THz,max) ~ 50 kV/cm at an optical pump pulse energy of 25 muJ in a 0.6 mm thick crystal) using the high nonlinear optical susceptibility of DAST (chi (2)111 = 490 pm/V at lambda = 1535 nm) and velocity-matching observed in this material. Using a frequency-doubled probe beam at lambda = 750 nm, nearly velocity-matched detection can also be realized in ZnTe crystals, resulting in a continuous spectrum from 1.3 to 4 THz.