A resource-saving realization of the polarization-independent orbital-angular-momentum-preserving tunable beam splitter

TL;DR

This paper presents a resource-efficient, polarization-independent, orbital-angular-momentum-preserving tunable beam splitter with high extinction ratios and low polarization dependence, suitable for scalable quantum information applications.

Contribution

It introduces a novel, simplified TBS design that reduces optical elements by 75% while maintaining high performance, advancing scalable quantum optical systems.

Findings

Extinction ratio of tunableness >30 dB

Polarization dependence <6%

OAM preservation >20 dB

Abstract

Tunable beam splitter (TBS) is a fundamental component which has been widely used in optical experiments. We realize a polarization-independent orbital-angular-momentum-preserving TBS based on the combination of modified polarization beam splitters and half-wave plates. Greater than 30 dB of the extinction ratio of tunableness, lower than $6\%$ of polarization dependence and more than 20 dB of the extinction ratio of OAM preservation show the relatively good performance of the TBS. In addition, the TBS can save about 3/4 of the optical elements compared with the existing scheme to implement the same function\cite{yang2016experimental}, which makes it have great advantages in scalable applications. Using this TBS, we experimentally built a Sagnac interferometer with the mean visibility of more than $99\%$, which demonstrates its potential applications in quantum information process, such as quantum cryptography.