Effect of pulse to pulse variation of divergence, pointing and amplitude of copper vapor laser radiations on their second harmonic and sum frequency conversion

This paper presents the effect of single pulse stability of divergence angle, beam pointing angle and amplitude of green and yellow radiation pulses of an unstable resonator copper vapor laser (CVL) oscillator in the sum frequency (SF) mixing and second harmonic (SH). The conversion efficiency of sum frequency generation was lower compared to second harmonic processes despite larger fundamental power being used in sum frequency experiments. However the net UV power obtained at the sum frequency was higher than both of the second harmonic UV frequencies. Lower sum frequency generation (SFG) conversion efficiency compared to second harmonic generation (SHG) of individual CVL radiation is attributed to difference in single pulse stability of beam pointing, divergence and amplitude fluctuation of both CVL radiations in addition to commonly known fact of spatio-temporal mis-match. At the same fundamental input power, higher SH conversion efficiency of yellow compared to green is attributed to its better single pulse stability of beam pointing and divergence.

► Effect of divergence, pointing and amplitude stability is studied in CVL frequency conversion.
► Conversion efficiency of sum frequency generation was lower compared to second harmonic.
► Lower SFG efficiency compared to SHG is attributed to difference pulse stability parameters of CVL.
► Higher SH efficiency of yellow is attributed to better stability of beam pointing and divergence.