Multisegment oven scheme for Gouy phase shift compensation in second-harmonic generation.

Abstract

We present a theoretical model that describes a multisegment oven configuration to compensate for the Gouy phase shift in the tight focusing regime. The model is provided to obtain maximum efficiency of the second-harmonic wave. Numerical simulations are performed based on the experimental setup employing an MgO:sPPLT nonlinear crystal. It is shown by the simulation that the three-segment oven is potentially capable of reaching the highest efficiency by canceling the effect of Gouy phase when the temperature of each segment is so optimized that the phase-matching condition is re-established. It is found that by using a multisegment oven scheme with optimized temperature, the highest attainable second-harmonic generation (SHG) efficiency exceeds about 4.4% at a confocal parameter of 3.32. Moreover, it is shown that for long crystals with large confocal parameter, the only way to attain the maximum efficiency is by using multisegment ovens. The results indicate that when the number of segments is changed from one to nine, the confocal parameter can be varied from 3.90 to 5.85. In the candidate three-segment oven, by applying active control on the temperature of each segment, for a certain combination of segment lengths, ∼4% improvement in the SHG efficiency is achieved. This results in a relatively large increase in the acceptance temperature bandwidth of the crystal of up to 2 times, reflecting a comparatively large enhancement in the second-harmonic power stability and efficiency.