$\beta$ -BBO: Optical Properties and Phase-Matching for THz Wave Generation

Optical properties of β -BBO crystals i. e. absorption coefficient and refractive index dispersions, were studied using a custom-made terahertz time-domain spectrometer (THz-TDS) in the range of 0.2-2.0 THz at the room temperature (RT) of 293 K and at liquid nitrogen (LN) temperature of 81 K. The measured ordinary and extraordinary wave refractive indices were approximated in the form of Sellmeier equations. Phase-matching conditions for the IR- THz and THz- THz frequency conversion were calculated.