A Precision Angle Sensor using an Optical Lever inside a Sagnac Interferometer

TL;DR

This paper presents an ultra low noise angle sensor combining an optical lever and Sagnac interferometer, achieving record sensitivity of 1.3 prad/Hz^{1/2} at 2.4 kHz, with potential for further improvements.

Contribution

The paper introduces a novel combination of optical lever and Sagnac interferometer for highly sensitive angle measurement, demonstrating record low noise levels.

Findings

Measured noise floor of 1.3 prad/Hz^{1/2} at 2.4 kHz

Achieved record angle sensitivity with N=11 bounces

Potential to reach sub-picoradian/Hz^{1/2} sensitivities with optimization

Abstract

We built an ultra low noise angle sensor by combining a folded optical lever and a Sagnac interferometer. The instrument has a measured noise floor of 1.3 prad / Hz^(1/2) at 2.4 kHz. We achieve this record angle sensitivity using a proof-of-concept apparatus with a conservative N=11 bounces in the optical lever. This technique could be extended to reach sub-picoradian / Hz^(1/2) sensitivities with an optimized design.