Grover-Sagnac interferometer

TL;DR

This paper introduces a novel Sagnac interferometer design using a Grover multiport instead of a beam splitter, enabling resonance-based detection of non-reciprocal phase shifts with potential advantages in metrology.

Contribution

It presents a new interferometer configuration with a symmetric multiport, allowing resonance-based phase detection and offering a different approach from traditional methods.

Findings

Resonance at the origin of parameter space due to the multiport design

Phase information can be extracted from resonance features instead of power changes

Loss effects and potential metrological applications are discussed

Abstract

We demonstrate a nontraditional design of the Sagnac interferometer by replacing the commonly used beam splitter with a linear-optical Grover multiport. This substitution creates a pole at the origin of the device parameter space with an associated resonance in the output intensity. The structure of this resonance is dictated only by the non-reciprocal portion of the phase acquired in the Sagnac loop. This property directly results from adopting the more symmetric and higher-dimensional central scattering coin, and allows for a different approach to registering and detecting the non-reciprocal Sagnac phase. This parameter may be extracted from the width of a peak or dip in the interferogram instead of tracing small changes in power as in traditional Sagnac interferometry. We discuss how losses affect the system and potential metrological applications.