Statistical properties and stabilization of a picosecond phosphate-glass laser with 2 Hz repetition frequency

Detailed investigations were made of the statistical relationships between the energy and time parameters of a picosecond phosphate-glass laser operating at a repetition frequency of 2 Hz. This was done using an original measurement system based on a nonlinear-optical correlator, amplitude analyzers, and computers. Optimization of the gain saturation and bleaching of a two-component medium ensured a reproducibility of better than 0.95 in ultrashort pulse generation. The pump energy was reduced to 260 J and the coefficient representing fluctuations of the picosecond pulse energy was lowered to 0.08. The average pulse duration in a train was 8.5 psec. Stimulated Raman scattering produced pulses of τ_p = 2.6 psec duration. The duration of a single pulse selected from the initial part of a train was 6.2 psec. The spectral Q factor was Δυτ_p = 0.5, indicating the absence of phase modulation. The high stability of the laser made it possible to use its second harmonic in pumping an optical parametric oscillator in which a crystal of α-HJO₃ was used inside the resonator. The energy conversion efficiency was up to 10% for Δυτ_p = 0.7.