Generating a three dimensional dark focus from a single conically refracted light beam

TL;DR

This paper demonstrates how a single Gaussian beam undergoing conical refraction in a biaxial crystal can produce a three-dimensional dark focus, with experimental validation aligning with theoretical predictions.

Contribution

It introduces a method to generate a 3D dark focus using conical refraction, providing both theoretical analysis and experimental validation.

Findings

Successful generation of a 3D dark focus from a Gaussian beam

Identification of parameter conditions for dark focus formation

Experimental confirmation with KGd(WO4)2 crystal

Abstract

We report here the generation of a three dimensional dark focus from a single focused monochromatic Gaussian beam that undergoes conical refraction when it propagates along one of the optic axes of a biaxial crystal. We study the resulting ring intensity pattern behind the crystal as a function of the ratio between the ring radius and the beam waist and derive the particular parameter values for which a three dimensional dark focus with null intensity at the ring center is formed. We have performed experiments with a ${\rm KGd(WO_4)_2}$ biaxial crystal reporting the generation of a bottle beam in full agreement with our theoretical investigations.