Optical Properties and Terahertz Radiation Generation in a LI 2 B 4 O 7 Crystal

Spectral dependences of components of the refractive index and absorption coefficient in a Li2B4O7 (LB4) nonlinear crystal are determined in the THz range for the first time. Measurements have been carried out in the 0.15–1.6 THz (180–2000 μm) spectral range. The measured refractive index components are approximated by the Sellmeier dispersion equations subsequently used to determine the possible interaction types and to calculate the phase-matching angles for THz wave generation at the difference frequency between a Nd:YAG laser and a tunable laser source with a close wavelength. The efficiency of the process is estimated.