On the role of the coherence width and its evolution in a short-pulse fundamental beam in second harmonic generation from beta-barium borate

The paper discusses the influence of the evolution of the spatial coherence of the fundamental beam on second harmonic generation (SHG) of copper vapor laser beams in beta-barium borate (BBO) crystals. It is established that a coherence parameter, defined, as the ratio of the coherence width to the full beam cross-section, can uniquely be used to compare the performance of beams from different resonators for SHG. Fundamental beams with average coherence widths varying from a fraction of the beam cross-section to the full cross-section were used. It is established, from time-resolved and averaged studies, that in line-focusing geometry, SHG is primarily governed by this coherence parameter.