Laser frequency stabilization apparatus

Abstract

An apparatus and a method for laser frequency stabilization include a laser, a modulator, a derivative module, a Fabry-Perot etalon, a photodetector, a balanced mixer, a signal processing module, and a feedback control module. The laser has an output and lases at a single frequency. The laser has a desired frequency and provides an optical signal including a substantial frequency chirp signal. The modulator is coupled to the laser and provides a modulation signal for modulating the laser. The derivative module is coupled to the modulator and provides a derivative signal which is a time derivative of the modulation signal. The Fabry-Perot etalon is coupled to the output of the laser and has a frequency response including a plurality of resonances. One of the plurality of resonances is centered on the desired frequency. The etalon filters the optical signal according to the frequency response. The photodetector is coupled to the etalon and receives the filtered optical signal and provides a photocurrent in response to the filtered optical signal. The balanced mixer is coupled to the photodetector and to the derivative module. The balanced mixer provides a mixed signal by mixing the photocurrent with the derivative signal. The signal processing module is coupled to the balanced mixer and provides an error signal which is a time average of the mixed signal. The feedback control module is couple to the signal processing module and the laser. The feedback control module uses the error signal in order to adjust the single frequency of the laser.