Phase-matched DAST DFG THz-wave generation using independently controllable dual wavelength light source

We report on the demonstration of an effective and widely tunable terahertz (THz)-wave generation using difference frequency generation (DFG) in an organic 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) by optimization of the pumping wavelength. We calculated the Type 0 phase-matching condition of DAST-DFG THz-wave generation over an ultrawide band (1.5-20 THz). A dual-wavelength optical parametric oscillator (OPO) with two KTP crystals mounted on a galvano scanner was constructed. To satisfy phase-matching conditions over the whole THz-wave region, pump wavelengths lambda₁ and lambda₂ were controlled independently from 1.25 to 1.6 mum. A comparison of the calculated and experimental results established the optimum phase-matching condition of DAST-DFG.