Subnanosecond visible two-stage optical parametric generator and amplifier based on MgO:PPLN and LBO crystals at strong pump depletion

Theoretical and experimental investigation of two-stage optical parametric generator based on magnesium oxide doped periodically poled lithium niobate (MgO:PPLN) crystal and optical parametric amplifier based on lithium triborate (LBO) crystal is presented. The first stage crystal was pumped by the subnanosecond fundamental harmonic at 1064 nm wavelength. In the theoretical description, the input signal and idler photons are described by the quantum model and their further amplification is tracked by simulating the nonlinear coupling equations. Such description allows the analysis of pulsed beam evolution during the propagation in the nonlinear crystal under strong pump depletion regime. The second stage crystal was seeded by the output signal wave of the first stage and pumped by the third harmonic of the laser radiation. Experimentally, tuning in the visible wavelength ranges and high pulse power (up to 20 mW at 475 nm wavelength) were achieved.