Coherent population trapping spectral line characteristics for high sensitivity magnetic field measurement

The coherent population trapping (CPT) phenomenon of atoms is used for high precision measurement of weak magnetic field. The sensitivity of the measurement is mainly affected by the resonance spectrum characteristics when this phenomenon occurs. Signal quality factor is defined to represent the characteristics of the CPT resonance signal. Its variation with temperature of the atomic chamber is analyzed and compared with signal contrast. Results show that signal quality factor and signal contrast offer different optimal working temperature which corresponding to the maximum value. The optimal temperature proposed by the signal quality factor is always lower and it makes the magnetic field measurement system to obtain a higher sensitivity.