Atomic Clocks and Coherent Population Trapping: Experiments for Undergraduate Laboratories

TL;DR

This paper presents an accessible undergraduate laboratory setup for studying atomic coherence effects, specifically coherent population trapping (CPT), and demonstrates its application in precise atomic clock measurements.

Contribution

It introduces a simple, cost-effective experimental apparatus for observing CPT and exploring its use in atomic clock technology suitable for undergraduate education.

Findings

Successful construction of a CPT experiment with a VCSEL laser

Accurate measurement of hyperfine transition frequency

Potential for developing CPT-based atomic clocks in educational settings

Abstract

We demonstrate how to construct and operate a simple and affordable experimental apparatus, appropriate for an undergraduate setting, in order to produce and study coherent effects in atomic vapor and to investigate their applications for metrology. The apparatus consists of a vertical cavity surface emitting diode laser (VCSEL) directly current-modulated using a tunable microwave oscillator to produce multiple optical fields needed for the observation of the coherent population trapping (CPT). This effect allows very accurate measurement of the transition frequency between two ground state hyperfine sublevels (a "clock transition"), that can be used to construct a CPT-based atomic clock.