Noise suppression in coherent population-trapping atomic clock by differential magneto-optic rotation detection.

We propose and investigate a scheme for differential detection of the magneto-optic rotation (MOR) effect, where a linearly polarized bichromatic laser field is coherent population-trapping (CPT)-resonant with alkali atoms, and discuss the application of this effect to CPT-based atomic clocks. The results of our study indicate that laser noise in a vertical cavity surface-emitting laser-based CPT atomic clock can be effectively suppressed by the proposed scheme. The proposed scheme promises to realize a packaged MOR-CPT atomic clock that has significantly better frequency stability coupled with similar power consumption, volume, and cost when compared with currently available packaged CPT atomic clocks.

Quasi-bichromatic laser for a lin[perpendicular]lin coherent population trapping clock produced by vertical-cavity surface-emitting lasers.

With two vertical-cavity surface-emitting lasers working under the master-slave sideband injection-locking configuration, we have realized a quasi-bichromatic laser beam with residual phase noise Δφ(2) < 0.282 rad(2). The two wanted frequency components share more than 96% power of the beam. With the realized beam, we have carried out coherent population trapping (CPT) resonance experiment with (87)Rb in the lin[perpendicular]lin CPT scheme, and recorded CPT resonance signal with contrast of 60%. Such laser system is promising to realize a lin[perpendicular]lin CPT clock with high performance and low power consumption.

High coherent bi-chromatic laser with gigahertz splitting produced by the high diffraction orders of acousto-optic modulator used for coherent population trapping experiments.

To prepare the coherent population trapping (CPT) states with rubidium and cesium, the commonly used atoms in CPT studies, a coherent bi-chromatic light field with frequency difference of several GHz is a basic requirement. With a 200 MHz center frequency acousto-optic modulator (AOM), we have realized bi-chromatic laser fields with several GHz frequency splits through high diffraction orders. We have experimentally studied the coherence between two frequency components of a bi-chromatic laser beam, which is composed of ±6 orders with frequency split of 3 GHz diffracted from the same laser beam, and the measured residual phase noise is Δφ(2)<0.019 rad(2). The bi-chromatic laser fields were used to prepare CPT states with (85)Rb and (87)Rb atoms, and high contrast CPT signals were obtained. For CPT states preparation, our study result shows that it is a feasible approach to generate the bi-chromatic light field with larger frequency splits through high diffraction orders of AOM.