Enhanced Second Harmonic Generation Efficiency via Wavefront Sha

Optical second harmonic generation is a fundamental nonlinear effect with a large impact on laser technology and optical imaging/sensing. For most practical applications of second harmonic generation, high conversion efficiency is required. However, many techniques used to achieve high efficiency are limited to fabrication methods and optical energy requirements. Here, we investigate and demonstrate substantial enhancement in the conversion efficiency of second harmonic generation in a nonlinear crystal via the application of wavefront shaping. In a one dimensional understanding of second harmonic generation, a phase offset applied to the fundamental wave has no effect on the intensity of the generated light. We show that when the pump field is not a plane wave, enhanced conversion efficiency can be controlled by the application of a phase mask to the fundamental beam. This investigation of the dependence of conversion efficiency upon the transverse phase profile of the incident pump laser yields the promise of new ways to enhance nonlinear generation with limited optical energy and without the need for specific fabrication techniques.