Fiber-Based Laser Frequency Stabilization by Polarization Spectroscopy

Systems and methods to stabilize a laser frequency include a birefringent resonator that introduces an arbitrary phase difference between two polarization components of the laser beam, a polarizing beam splitter to separate the two polarization components after the birefringent resonator, and a differential detector to monitor the separated two polarizations, based on which an error signal can be produced to control a servo to adjust the laser frequency or resonator resonance frequency accordingly. The birefringent resonator can comprise a fiber ring, a whispering gallery mode (WGM) resonator, or any other birefringent ring resonator. A servo can be included in the systems and methods to lock the laser frequency to the resonant frequency of the birefringent resonator or to lock the resonator resonant frequency to the laser frequency. One or more polarization controllers can also be employed to adjust the polarization state of the laser beam.