Spectroscopy of fractional orbital angular momentum states

TL;DR

This paper introduces a novel spectroscopic method for measuring and distinguishing fractional and integer orbital angular momentum states of light, with potential applications in semiconductor system analysis.

Contribution

It develops a new approach based on OAM sorting to identify mixed and fractional OAM states, advancing optical measurement techniques.

Findings

Mixed and fractional OAM states can be identified using intensity distribution moments.

The method distinguishes between intrinsic and total OAM in fractional states.

Experimental results align well with simulations, demonstrating effectiveness.

Abstract

We present an approach for measuring the orbital angular momentum (OAM) of light tailored towards applications in spectroscopy and non-integer OAM values. It is based on the OAM sorting method (Berkhout et al., Phys. Rev. Lett. 105, 153601 (2010)). We demonstrate that mixed OAM states and fractional OAM states can be identified using moments of the sorted output intensity distribution and OAM states with integer and non-integer topological charge can be clearly distinguished. Furthermore the difference between intrinsic OAM and total OAM for fractional OAM states is highlighted and the importance of the orientation of the fractional OAM beam is shown. All experimental results show good agreement with simulations. Finally we discuss possible applications of this method for spectroscopy of semiconductor systems such as exciton-polaritons in microcavities.