Optical-collisional nonlinearity and the coherent population trapping effect

M. B. Gornyi, Boris G. Matisov, Yu. V. Rozhdestvenskiǐ

Hong Yuan Ling, P. Maenner, Han Pu

Coherent population trapping (CPT) is an important concept in many subfields of physics and chemistry. Here we analyze the collective excitation spectrum of the CPT states in a coupled atom-molecule condensate system. We find that collisions between particles can cause the CPT state to be dynamically unstable, which is a unique feature of the nonlinear system. We obtain a set of analytical criteria for determining the stability properties of the CPT state in the long-wavelength limit. We construct stability diagrams and provide a systematic classification of various instabilities according to collisional interaction strengths.

Martin Graf, E. Arimondo, Edward S. Fry +4 more

In the early experiments on optical pumping and coherent population trapping (``dark resonances'') increasing buffer gas pressure enhances the effect. In our recent lasing-without-inversion experiments, based on population trapping, we find the opposite behavior, namely, decreasing atomic coherence with increasing buffer gas pressure. We provide a theoretical explanation of this result in agreement with experiment.

Bryan J. Dalton, P. L. Knight

E. R. Eliel, Marc C. de Lignie

J. W. Pollock, Valeriy I. Yudin, А. В. Тайченачев +5 more

Coherent population trapping (CPT) in atomic vapors using all-optical interrogation has enabled the miniaturization of microwave atomic clocks. Light shifts induced by the CPT driving fields can impact the spectral profile of CPT resonances and are a common limit to the long-term stability of CPT clocks. Nonlinear light shifts have been observed in several CPT systems and have not been explored in detail. In this Letter, we demonstrate that nonlinear light shifts in CPT clocks can arise from spatially inhomogeneous CPT driving fields. We measure this effect using Gaussian laser beams in a buffer gas cell and show strong agreement with a four-level model describing the CPT Λ-system with a noninteracting “trap” state. We estimate the effect of this nonlinearity on recently developed light shift mitigation techniques and suggest improvements to existing techniques.