Novel method to measure the refractive index and the absorption coefficient of organic nonlinear crystals in the ultra wideband THz region

A method for simultaneously measuring the refractive index and absorption coefficient of nonlinear optical crystals in the ultra-wideband terahertz (THz) region was developed. This method is based on the analysis of a collinear difference frequency generation (DFG) process using a tunable, dual-wavelength, optical parametric oscillator. The refractive index and the absorption coefficient in the organic nonlinear crystal DAS were experimentally determined in the frequency range of 2.5-26.2 THz.