Temperature Dependence of Refractive Indices of Nonlinear LiB 3 O 5 Crystals in THz Range

Spectral-temperature dependences of the refractive indices of nonlinear LBO crystals 30 × 30 × 10 mm 3 in size are derived by terahertz time-domain spectroscopy in the 0.05–0.5-THz range upon heating from 20 to 200°C. Intersection of the spectral dependences of the refractive index components n x and n y is found at ∼84°C. The results can be used for selection of types and phase-matching conditions for frequency conversion into the long-wavelength part of the THz region, which is promising for monitoring the gas composition of the atmosphere due to the low sensitivity to aerosol attenuation.