Two-frequency pulsed YLiF_4:Nd lasing out of the principal axes and THz generation

Thanks to a propagation direction at 50.3° from the c axis in a LiYF4:Nd crystal, we have equalized the emission cross-sections at 1047 and 1053 nm, respectively, for extraordinary and ordinary waves. The double refraction is used to balance the "o" and "e" pumping. Actively Q-switching the laser cavity leads to simultaneous pulses with duration less than 10 ns. Frequency conversion to THz radiation was performed through difference frequency mixing in two nonlinear crystals: GaSe and OH1. In the first case, we obtained 132 nW and in the second case we obtained 51 nW THz power at 6.67 kHz repetition rate.