Highly stable polarization independent Mach-Zehnder interferometer

TL;DR

This paper presents a highly stable, polarization-insensitive Mach-Zehnder interferometer with minimal phase drift over extended periods, suitable for quantum information applications where active stabilization is challenging.

Contribution

The authors demonstrate a displaced Sagnac configuration-based interferometer with exceptional phase stability and polarization insensitivity, advancing stable optical interferometry for sensitive applications.

Findings

Phase deviation less than 0.4 degrees over 250 seconds

Phase drift below 3 degrees or 7 nm over 1.5 hours without stabilization

Visibility above 93% for all polarization states and ports

Abstract

We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27x40 cm offers individually accessible paths and shows phase deviation less than 0.4 deg during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3 deg or 7 nm for 1.5 hours without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually.