Optical beam diffraction tensor in birefringent crystals

TL;DR

This paper introduces a planar tensor to quantify anisotropic Fresnel diffraction in birefringent crystals, revealing eigenvector directions related to beam divergence and autocollimation, with applications in phase matching and three-wave mixing.

Contribution

It presents a novel tensor-based method to analyze anisotropic diffraction in birefringent media, linking tensor eigenvectors to beam propagation characteristics.

Findings

Eigenvectors indicate directions of minimum and maximum divergence.

Zero eigenvalues correspond to autocollimated propagation.

Application demonstrated in phase matching and three-wave mixing.

Abstract

We demonstrate that anisotropy of Fresnel diffraction in a birefringent medium can be quantitatively characterized by a planar tensor. Eigenvectors of the tensor correspond to directions of minimum and maximum beam divergence. Zero eigenvalues exist for the fast eigenmode near the optic axis of biaxial crystals and correspond to autocollimated beam propagation. Applications of the beam diffraction tensor are demonstrated for analysis of noncritical phase matching in acousto-optics and three-wave mixing.