Spatial coherence measurement of multiple coherent laser combination

Coherent combination of laser beam is an important and challenging area of laser science, and many researchers have demonstrated a lot of multiple laser-beam combining technologies and structures. In this paper, the coherent combining principle was discussed and a novel self-coherent-combining solid state laser based on corner cube cavity is reported, for which a corner cube was utilized as a terminal mirror. The authors found that the near-field intensity distribution profile of CCR laser was divided into six fan-shaped segments by dihedral angle lines and their images, while its far-field intensity distribution presenting good centralized profile as a strong peak surrounded symmetrically by six weaker peaks. In order to get quantitative coherence details of CCR lasers, spatial coherence of two conjugate laser beams were measured. The far-field distribution of the conjugate laser beams presented very clear interference pattern and the stripe contrast visibility was calculated as high as 0.74 indicating the coherence degree should be even more than 0.74.