Feedback enhancement of the amplitude of dynamically excited coherent population trapping resonance in Rb vapour

This work reports on possibilities of contrast enhancement of dynamically excited coherent population trapping (CPT) resonance in ⁸⁷Rb vapour arising from application of feedback methods. Controlling the bichromatic pump radiation power through a feedback loop that stabilises Rb atom luminescence when scanning the frequency difference of the bichromatic pump radiation resulted in a more than an order-or-magnitude improvement in the amplitude of the CPT resonance at scanning frequencies over 100 Hz. It is established that the excursion of the pump radiation power controlled by the feedback loop under dynamic excitation is by an order of magnitude smaller than that under quasistationary excitation at scan frequencies < 1 Hz.