Detecting orbital angular momentum through division-of-amplitude interference with a circular plasmonic lens

TL;DR

This paper introduces a new method for detecting the orbital angular momentum of light using a circular plasmonic lens, leveraging interference patterns that reveal OAM characteristics.

Contribution

A novel OAM detection scheme based on division-of-amplitude interference with a circular plasmonic lens, validated experimentally and supported by analytical models.

Findings

Interference patterns rotate with OAM sign and magnitude.

The detection scheme is experimentally validated.

Analytical expressions explain the interference behavior.

Abstract

We demonstrate a novel detection scheme for the orbital angular momentum (OAM) of light using circular plasmonic lens. Owing to a division-of-amplitude interference phenomenon between the surface plasmon waves and directly transmitted light, specific intensity distributions are formed near the plasmonic lens surface under different OAM excitations. Due to different phase behaviors of the evanescent surface plasmon wave and the direct transmission, interference patterns rotate as the observation plane moves away from the lens surface. The rotation direction is a direct measure of the sign of OAM, while the amount of rotation is linked to the absolute value of the OAM. This OAM detection scheme is validated experimentally and numerically. Analytical expressions are derived to provide insights and explanations of this detection scheme. This work forms the basis for the realization of a compact and integrated OAM detection architect that may significantly benefit optical information processing with OAM states.