Doubling of THz emission in nonlinear borate crystals

We present the possibility of effective doubling of millimeter wave radiation in the range of 400-2500 μm in borate crystals. The phase matching angles are calculated. It is shown that for LN and β-BBO crystals the realization of o + o → e and e + o → e interactions is possible, and for LB4 only o + o → e. The walk-off angle, spectral and angular phase-matching bandwidth are calculated. An estimate is given of the maximum efficiency of SHG taking into account the measured optical damage threshold of 150 TW/cm2 for the LB4 crystal and 100 TW/cm2 for β-BBO.

Ablation of BaWO4 Crystal by Ultrashort Laser Pulses

Ablation of BaWO4 Raman crystals with different impurity concentrations by ultrashort laser pulses was experimentally studied. Laser pulses with duration varying from 0.3 ps to 1.6 ps at wavelengths of 515 nm and 1030 nm were applied. A single-pulse optical damage threshold of the crystal surface changed from 1.3 J/cm2 to 4.2 J/cm2 depending on the laser pulse parameters and BaWO4 crystal purity. The optical damage threshold under multi-pulse irradiation was an order of magnitude less.