Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Inhomogenous Light Shifts of Coherent Population Trapping Resonances



Juniper Pollock, Valera Yudin, Alexey Taichenachev, Maxim Basalaev, D Kovalenko, Azure Hansen, John Kitching, William McGehee


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 elds can impact the spectral pro le 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 elds. We measure this e ect using Gaussian laser beams in a bu er gas cell and show strong agreement with a 4-level model describing the CPT \Lambda-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.
Applied Physics Letters


coherent population trapping, light shifts


Pollock, J. , Yudin, V. , Taichenachev, A. , Basalaev, M. , Kovalenko, D. , Hansen, A. , Kitching, J. and McGehee, W. (2022), Inhomogenous Light Shifts of Coherent Population Trapping Resonances, Applied Physics Letters, [online],, (Accessed June 15, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created April 13, 2022, Updated November 29, 2022