GaP based terahertz time-domain spectrometer optimized for the 5-8 THz range

We use GaP to generate terahertz pulses via optical rectification in a collinear phase-matched configuration relying on the dispersion of the refractive index. The GaP-based time-domain system operates up to 8 THz and is especially well suited at high frequencies, where it has high signal-to-noise ratio and power conversion efficiency similar to 30 times greater than those of commercial photoconductive emitters. These characteristics are demonstrated in measurements of ZnTe in the reflection geometry. We also discuss the power output and describe theoretically the observed THz field generation by nonlinear mixing, the field's free space propagation, and its detection. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764545]