Broadband terahertz pulse generation by optical rectification in GaP crystals

We demonstrate a broadband (0.3–7 THz) terahertz pulse generation using GaP generation and detection crystals with an 80-MHz-repetition-rate Ti:Sapphire laser. We also use simulations of cascaded terahertz generation to model the observed terahertz gain profiles. The efficient generation of the broadband terahertz pulses is based on optimizing the phase matching between the optical and terahertz pulses, which is achieved by tuning the wavelength of the laser. We observed further improvement in the generation efficiency due to a mismatching of the imaginary part of the complex wavevectors. Together, these effects allow the use of thicker crystals and thus lead to increased terahertz emission. Our results show that optical rectification by GaP can be used to generate broadband terahertz pulses with MHz-repetition-rate lasers up to a dynamic range that is comparable to commonly used sources like ZnTe and photo-conductive antennas.