Temporal and spatial coherence of the second harmonic of the radiation of a multimode Nd3+-doped glass laser in various nonlinear media

The degree of the spatial and temporal coherence of the second-harmonic radiation in LiNbO₃, LiIO₃, KDP, RDP, and CDA crystals was investigated and compared for different operating conditions in an Nd³⁺-doped glass laser. It was found that the degree of the spatial coherence of the radiation increased by a factor of 1.5–2 in the second-harmonic generation process in all crystals, irrespective of the operating conditions in the laser. The coherence time of the fundamental-frequency radiation and of the second harmonic was governed by the emission spectrum.