Efficiency improvement of an optical parametric oscillator using top-hat transverse profile for the pump beam

Pulsed nanosecond optical parametric oscillators, in general, are pumped by a direct laser beam having Gaussian intensity profiles in temporal and spatial domains, which limits the conversion efficiency due to energy consumption during build-up of signal and idler intensities, and back-conversion effects. Efficiency optimization in an OPO involves reducing the loss due to these effects; however, spatial distribution of amplitude across the beam limits the optimized efficiency. We show that by using a spatially uniform intensity profile for the input pump beam, one can achieve much higher optimized efficiency because of optimum conversion across the whole cross-section of the beam. Our simulation results predict a significant improvement of ~41% in the optimized efficiency using a pump beam with top-hat transverse intensity profile.