Realization of a scalable Laguerre-Gaussian mode sorter based on a robust radial mode sorter.

Dongzhi Fu,Stone Oliver,Robert W Boyd,Yunlong Wang,Zhimin Shi,Rui Qi,Jiapeng Zhao,Yiyu Zhou,Pei Zhang,Seyed Mohammad Hashemi Rafsanjani,Mohammad Mirhosseini

doi:10.1364/oe.26.033057

Abstract

The transverse structure of light is recognized as a resource that can be used to encode information onto photons and has been shown to be useful to enhance communication capacity as well as resolve point sources in superresolution imaging. The Laguerre-Gaussian (LG) modes form a complete and orthonormal basis set and are described by a radial index p and an orbital angular momentum (OAM) index ℓ. Earlier works have shown how to build a sorter for the radial index p or/and the OAM index ℓ of LG modes, but a scalable and dedicated LG mode sorter which simultaneous determinate p and ℓ is immature. Here we propose and experimentally demonstrate a scheme to accomplish complete LG mode sorting, which consists of a novel, robust radial mode sorter that can be used to couple radial modes to polarizations, an ℓ-dependent phase shifter and an OAM mode sorter. Our scheme is in principle efficient, scalable, and crosstalk-free, and therefore has potential for applications in optical communications, quantum information technology, superresolution imaging, and fiber optics.

Highlights

The transverse structure of light can be described by an infinite-dimensional Hilbert space, making it attractive for applications such as quantum information technology [1, 2] and optical communications [3,4,5,6,7]
A 633 nm HeNe laser is coupled to a single-mode fiber (SMF) and is collimated to illuminate a spatial light modulator (SLM)
The -dependent phase shifter consists of a Sagnac interferometer and a Dove prism and is cascaded to the fractional Fourier transform (FRFT) module to remove the fractional number 1/2 that appears in Eq (6) as analyzed earlier

Summary

Introduction

The transverse structure of light can be described by an infinite-dimensional Hilbert space, making it attractive for applications such as quantum information technology [1, 2] and optical communications [3,4,5,6,7]. While the OAM modes have been broadly applied to enhancing transmission rates of both classical and quantum communications [3,4,5,6,7, 9,10,11,12,13], it is desirable to multiplex the radial degree of freedom of LG modes since the OAM modes alone cannot reach the capacity limit of a communication channel [14] Multiplexing of both p and has been investigated in high-dimensional entangled quantum system [2] and shows the potential usefulness of LG modes in quantum information technology [1, 15,16,17,18,19,20,21]. Instead of detecting the position information of photons via a camera, measuring the spatial mode components can provide higher

Methods

Results

Conclusion