Frequency locking: A distinctive feature of the coherent population trapping

We investigate the use of phase modulation to generate an error signal for frequency stabilization to a reference atomic transition. The study focuses on the high-frequency modulation regime. Our theoretical analysis shows that, in the case of coherent population trapping, the maximal slope of the error signal remains constant as the modulation frequency increases, whereas it steadily decreases for other types of resonances. Experimental results with Rb-87 atoms confirm this behavior under comparison with the double radio-optical resonance. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/).