A coherent population trapping magnetometer using a phase-delayed differential detection method

We propose an improved Coherent population trapping (CPT) magnetometer using a phase-delayed differential detection (PDD) method. The PDD approach capable of generating two linearly-polarized beams with orthogonal states that can interfere with each other can radically improve the slope of the CPT dispersion signal curve and offer the possibility of improving the CPT magnetometer sensitivity. We experimentally observed the simultaneous existence of constructive interference states and destructive interference states in the dispersion curves for different sideband excitations in a bichromatic light field and obtained an approximately two-fold increase in the slope of the dispersion curves after interference. We also utilize a differential scheme to probe the change in the slope of the dispersion curve and measure that the slope of the dispersion curve is increased by about a factor of 3 compared to the slope of the dispersion curve of the single-transmitted light. The results indicated that the proposed method has about a three-fold sensitivity enhancement effect on the CPT magnetometer.