Simple method for locking birefringent resonators

TL;DR

This paper introduces a straightforward polarization spectroscopy method for locking lasers to birefringent resonators, eliminating the need for modulation and simplifying the setup, especially useful for fiber ring resonators.

Contribution

The authors present a novel, modulation-free polarization spectroscopy technique for laser locking to birefringent cavities, applicable even with unknown birefringence properties.

Findings

Successful experimental demonstration with a fiber ring resonator.

Error signal extraction without light or resonator modulation.

Applicable to various birefringent optical resonators.

Abstract

We report on a simple method of locking a laser to a birefringent cavity using polarization spectroscopy. The birefringence of the resonator permits the simple extraction of an error signal by using one polarization state as a phase reference for another state. No modulation of the light or the resonator is required, reducing the complexity of the laser locking setup. This method of producing an error signal can be used on most birefringent optical resonators, even if the details of birefringence and eigenpolarizations are not known. This technique is particularly well suited for fiber ring resonators due to the inherent birefringence of the fiber and the unknown nature of that birefringence. We present an experimental demonstration of this technique using a fiber ring.