Probe beam frequency stabilization in an atomic sensor system

A method for stabilizing a frequency of an optical probe beam in an atomic sensor system, the method comprising:

• providing the optical probe beam through a vapor cell of the atomic sensor system comprising a precessing alkali metal vapor;
• beam-splitting the optical probe beam exiting the vapor cell into orthogonal polarization components;
• measuring an intensity of each of the orthogonal polarization components to generate a first intensity signal and a second intensity signal;
• adding the first and second intensity signals to generate a summation signal;
• generating a feedback signal associated with a magnitude of the summation signal;
• and
• stabilizing the frequency of the optical probe beam based on the feedback signal.

An atomic sensor system comprising:

• a vapor cell comprising an alkali metal vapor that precesses in response to a magnetic field;
• a probe laser configured to generate an optical probe beam that is modulated about a center frequency via a square-wave modulation signal and which is provided through the vapor cell;
• a photodetector assembly configured to generate a first intensity signal and a second intensity signal that correspond, respectively, to orthogonal polarizations of a detection beam corresponding to the optical probe beam exiting the vapor cell;
• and
• a detection system configured to add the first and second intensity signals to generate a summation signal and to demodulate the summation signal at a frequency of the square-wave modulation signal to generate a feedback signal that is provided to the probe laser to substantially stabilize the center frequency of the optical probe beam.