Vector-sensitive electrometer

A method for detecting an external signal via an electrometer system, the method comprising:

• directing a probe beam having a first frequency through a sensor cell comprising an alkali metal vapor in a first direction;
• directing a coupling beam having a second frequency different from the first frequency through the sensor cell collinearly and anti-parallel with the probe beam;
• directing a reference signal comprising a radio frequency (RF) signal having a predetermined polarization and a predetermined frequency through the sensor cell;
• monitoring a detection beam corresponding to the probe beam exiting the sensor cell to ascertain a beat frequency that is associated with a difference between the predetermined frequency and the frequency of the external signal;
• and
• determining at least one of a frequency, an amplitude, and a polarization of the external signal based on the beat frequency.

An electrometer system comprising:

• a sensor cell comprising an alkali metal vapor within;
• a probe laser configured to generate a probe beam having a first frequency and directed through the sensor cell in a first direction, the probe beam exiting the sensor cell as a detection beam;
• a coupling laser configured to generate a coupling beam having a second frequency different from the first frequency and directed through the sensor cell collinearly and anti-parallel with the probe beam;
• optics configured to provide the probe beam and the coupling beam to be collinear and anti-parallel with respect to each other and to focus each of the probe beam and the coupling beam to a measurement point within the sensor cell;
• a reference signal generator configured to generate a reference signal comprising a radio frequency (RF) signal having a predetermined polarization and a predetermined frequency through the sensor cell;
• and
• a detection system configured to monitor the detection beam to determine signal characteristics of an external signal at the measurement point based on an intensity of the detection beam and based on the predetermined polarization and the predetermined frequency of the reference signal.