Non-collinear interaction of photons with orbital angular momentum

TL;DR

This paper presents a phase-matching theory for second-harmonic generation involving non-collinear light beams with orbital angular momentum, revealing reduced efficiency and experimental validation with implications for photon parametric processes.

Contribution

It introduces a new phase-matching theory for non-collinear OAM beams and demonstrates its effects on conversion efficiency, supported by experimental results.

Findings

Reduced conversion efficiency for certain OAM states

Excellent agreement between theory and experiments

Implications for photon parametric down-conversion

Abstract

We elucidate the consequences of a phase-matching theory that describes second-harmonic generation of two non-collinear incident light beams that carry orbital angular momentum (OAM). More specifically, the two incident beams generate a third that, depending on the incident OAM, may experience a significantly smaller conversion efficiency in comparison to that based on the conventional phase-matching theory. This is the case even for incident angles substantially less than those required for non-conservation of OAM in the nonlinear interaction. Experiments are performed under different conditions and are in excellent agreement with the theory. Our results have implications beyond the specific case studied here of second-harmonic generation, in particular for parametric down-conversion of photons.