Type I and type II second harmonic generation of conically refracted beams

TL;DR

This paper investigates the second harmonic generation of conically refracted beams, deriving analytical models and experimentally confirming the distinct intensity patterns for type I and type II processes.

Contribution

It provides the first analytical description of SHG patterns in conically refracted beams and compares these with experimental results.

Findings

Type I SHG produces a light ring with a null point.

Type II SHG results in a ring with two dark regions.

Second harmonic signals behave as conically refracted beams.

Abstract

Type I and type II second harmonic generation (SHG) of a beam transformed by the conical refraction phenomenon are presented. We show that, for type I, the second harmonic intensity pattern is a light ring with a point of null intensity while, for type II, the light ring possesses two dark regions. Taking into account the different two-photon processes involved in SHG, we have derived analytical expressions for the resulting transverse intensity patterns that are in good agreement with the experimental data. Finally, we have investigated the spatial evolution of the second harmonic signals, showing that they behave as conically refracted beams.