Eur. Phys. J. D 53, 153-161 (2009)
https://doi.org/10.1140/epjd/e2009-00126-5

Coherent population trapping and strong electromagnetically induced transparency resonances on the D₁ line of potassium

¹ Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche – Area della Ricerca, via G. Moruzzi 1, 56124 Pisa, Italy
² Institute of Electronics, BAS, boul. Tzarigradsko shosse 72, 1784 Sofia, Bulgaria
³ CNISM Dipartimento di Fisica dell'Università di Siena, via Roma 56, 53100 Siena, Italy
⁴ Department of Physics, University of California at Berkeley, Berkeley, CA, 94720-7300, USA

Corresponding author: ^a silvia@ipcf.cnr.it

Received: 1 September 2008
Revised: 1 December 2008
Published online: 17 April 2009

Abstract

In this paper we report the first experimental observation of coherent population trapping (CPT) in thermal potassium vapor in a three levels Λ scheme. We demonstrate that K presents the advantage of a reduced modulation frequency with a large resonance contrast (up to 40%), in comparison to similar approaches with other alkalis. We report also the first evidence of electromagnetically induced transparency (EIT) resonances in K in the so called Hanle configuration. We tested different kinds of cells, demonstrating strong enhancement of the resonance contrast and amplitude for antirelaxation coated and buffered cells containing K vapor: resonance contrast up to 90% (for coated cells) and 65% (for buffered cells) is achieved with a linewidth of about 13 mG, while under similar conditions, the EIT resonance contrast in Cs vapor buffered by Ar gas is about 1%. Such relevant improvement is due to the reduced optical pumping in K, because of the overlapping of the hyperfine levels Doppler profiles, which does not occur in the case of Rb and Cs vapor. For this reason, K can be considered very promising for further CPT and EIT applications, especially for those where optical pumping losses represent a major limiting factor, such as light slowing and magnetometry.