This paper presents a comparative study on second harmonic conversion and saturation behavior of three copper vapor laser (CVL) beams of same average power up to 11 W (510 nm), however with different spatial coherence width of 17%, 35%, and 100% of the full beam cross-section. The nonlinear crystal employed is beta barium borate. It is observed that the trends in second harmonic (SH) conversion efficiency and its saturation are widely different for the three CVL pump beams. As expected, the conversion efficiency scaled up with increase in pump power. However, very interesting trends are observed in SH saturation characteristics with scaling of pump beams spatial coherence. For lower coherence CVL beam, the saturation of SH efficiency is observed at lower pump flux and at higher average power. Also, the saturation occurred at lower SH efficiency for CVL beam of lower spatial coherence. The fall in the SH efficiency after the peak is more rapid for lower spatial coherence pump beam. The experimental trends are explained in terms of combined effect degree of spatial coherence of pump beams and the thermal dephasing in the nonlinear crystal by high pump average power.
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