Broadband terahertz time domain spectroscopy with a femtosecond oscillator laser*

We have investigated broadband coherent terahertz (THz) generation and detection using a femtosecond oscillator laser. Our time-domain THz spectroscopic system adopts nonlinear crystals to generate and detect broadband (0.1~10 THz) THz radiation. Here we have used various nonlinear crystals (ZnTe, GaP, and LiNbO3 in many different thicknesses) as THz emitters and detectors and optimized their performance to maximize THz output power and/or spectral bandwidth. In particular, thin (0.1-0.3 mm) GaP crystals are used to achieve a large spectral bandwidth (~10 THz) with moderate laser power (<400 mW).