Coherent population trapping in a crystalline solid at room temperature

Abstract

Observation of coherent population trapping (CPT) at ground-state Zeeman sublevels of ${\mathrm{Cr}}^{3+}$ ion in ruby at room temperature is reported. A mechanism of CPT, not owing to optical pumping, is revealed in a situation when the optical pulse duration is shorter than the population decay time from the excited optical state.