Nonlinear optics determination of the symmetry group of a crystal using structured light

TL;DR

This paper introduces a method using structured light in nonlinear optics to determine the symmetry group of a crystal by analyzing the angular dependence of generated light in parametric down-conversion.

Contribution

It presents a novel technique that links the spatial angular patterns of nonlinear optical processes to the crystal's symmetry group, enabling direct symmetry identification.

Findings

The method successfully identifies the symmetry group from angular light patterns.

Structured Bessel beams reveal symmetry properties through nonlinear interactions.

The approach offers a new way to characterize crystals non-destructively.

Abstract

We put forward a technique to unveil to which symmetry group a nonlinear crystal belongs, making use of nonlinear optics with structured light. We consider as example the process of spontaneous parametric down-conversion. The crystal, which is illuminated with a special type of Bessel beam, is characterized by a nonlinear susceptibility tensor whose structure is dictated by the symmetry group of the crystal. The observation of the spatial angular dependence of the lower-frequency generated light provides direct information about the symmetry group of the crystal.