Coupled orbital angular momentum conversions in a quasi-periodically poled LiTaO3 crystal

TL;DR

This paper experimentally demonstrates coupled nonlinear optical processes in a quasi-periodically poled LiTaO3 crystal, showing OAM conservation and potential for efficient short-wavelength OAM generation.

Contribution

It introduces the first experimental demonstration of coupled OAM conversion via THG in a quasi-periodic LiTaO3 crystal, revealing OAM conservation in such processes.

Findings

OAM is conserved during coupled nonlinear processes

Conversion efficiency decreases with higher input OAM

Potential for efficient short-wavelength OAM generation

Abstract

We experimentally demonstrate the orbital angular momentum (OAM) conversion by the coupled nonlinear optical processes in a quasi-periodically poled LiTaO3 crystal. In such crystal, third-harmonic generation (THG) is realized by the coupled second-harmonic generation (SHG) and sum-frequency generation (SFG) processes, i.e., SHG is dependent on SFG and vice versa. The OAMs of the interacting waves are proved to be conserved in such coupled nonlinear optical processes. As increasing the input OAM in the experiment, the conversion efficiency decreases because of the reduced fundamental power intensity. Our results provide better understanding for the OAM conversions, which can be used to efficiently produce an optical OAM state at a short wavelength.