Simulation of harmonic and supercontinuum generation in polycrystalline media

Highly efficient, broadband frequency conversion in polycrystalline zinc-blende media receives increasing interest, motivated by both applications and understanding of the underlying processes. However, realistic simulations of the complex physics, in which random quasi-phase-matching plays a major role, is challenging because of the disorder. Here we present a family of models of increasing complexity, including a (3 + 1)D model with full resolution in time and space. Using ZnSe as the demonstration medium, we show that while a small-beam, axially symmetric approximation is able to provide qualitatively correct spectra at a low computation cost, the computationally more demanding (3 + 1)D approach achieves semi-quantitative agreement between the simulated supercontinuum spectrum and experiment results. The fully resolved (3 + 1)D simulations thus provide an accurate new tool for the characterization and optimization of supercontinuum generation in transparent polycrystals.