The commonly-used periodic patterning for quasi phase-matching plane-waves is theoretically adequate for completely depleting and transferring a fundamental wave to its second harmonic. However, when working with Gaussian beams the conversion efficiency of such a design lacks due to the inherent Gouy phase shift and the spatially-varying beam profile, yielding roughly 88% conversion efficiency. In this work we study the possibility of adding a linear chirp and Gouy-phase shift compensation to the periodic poling. We demonstrate that this poling pattern enables us to achieve near-optimal frequency doubling efficiency of up to 97%.

Written by: Roy Shiloh