Coherent population trapping magnetometer by differential detecting magneto–optic rotation effect
Zhang Fan, Tian Yuan, Zhang Yi, Gu Si-Hong†,
       

The modulation frequency is 1 kHz, the lock-in time constant is 50 ms, the voltage sensitivity of the lock-in amplifier is 5 mV, the laser intensity is 3 mW/cm2, and B = 3 μT. (a) CPT signal, (b) lock-in CPT signal.