High efficiency SHG of orbital angular momentum light in an external cavity

TL;DR

This paper introduces a novel high-efficiency method for generating orbital angular momentum (OAM) light using an external cavity with a nonlinear crystal, achieving over 10% conversion efficiency and stable higher-order LG mode operation.

Contribution

The work demonstrates a new cavity-based approach for efficient OAM light generation, surpassing traditional methods and enabling stable higher-order mode operation.

Findings

Conversion efficiency up to 10.3% achieved.

Stable operation of higher-order LG modes demonstrated.

Doubled OAM value in second harmonic generation.

Abstract

Traditional methods for generating orbital angular momentum (OAM) light include holographic diffraction gratings, vortex phase plate and spatial light modulator. In this article, we report a new method for high efficient OAM light generation. By pumping an external cavity contains a quasi phase matching nonlinear crystal with a fundamental OAM carrying light and properly aligning the cavity, mode matching between the pump light and the cavitys higher order Laguerre-Gaussian (LG) mode is achieved, conversion efficiency up to 10.3 percentage have been obtained. We have demonstrated that the cavity can stably operate at its higher order LG mode just as Gaussian mode for the first time. The SHG light possesses a doubled OAM value with respect to the pump light. The parameters that affect the beam quality and conversion efficiency are discussed in detail. Our work opens a brand new field in laser optics, and makes the first step toward high efficiency OAM light processing.