Precision frequency measurements with interferometric weak values

Abstract

We demonstrate an experiment which utilizes a Sagnac interferometer to measure a change in optical frequency of 129 $\ifmmode\pm\else\textpm\fi{}$ 7 $\text{kHz}/\sqrt{\text{Hz}}$ with only 2 mW of continuous-wave, single-mode input power. We describe the measurement of a weak value and show how even higher-frequency sensitivities may be obtained over a bandwidth of several nanometers. This technique has many possible applications, such as precision relative frequency measurements and laser locking without the use of atomic lines.