$^{85}$Rb electromagnetically induced transparency and absorption on two collinear $5S_{1/2}\rightarrow5P_{1/2}\rightarrow5D_{3/2}\rightarrow 25F_{5/2}$ three-photon cascade schemes

Abstract

We present a comprehensive study of three-photon electromagnetically induced transparency (EIT) and absorption (EIA) in room-temperature Rb vapor. Using the cascade system $5S_{1/2}\rightarrow5P_{1/2}\rightarrow5D_{3/2}\rightarrow 25F_{5/2}$ in $^{85}$Rb, we explore two collinear laser-beam configurations. The detunings of the upper two lasers of the cascade system are varied. In both configurations, the probe transmission maps contain rich sets of EIT/EIA features and substructures. To explain these, we utilize a dressed-atom and a quantum Monte Carlo trajectory method. The latter includes 108 relevant fine- and hyperfine-structure levels and their magnetic substates, accounting for coherent optical drives, optical pumping, atom recycling, electromagnetic decays via the $5P_{J}$ levels, and velocity-changing and hyperfine collisions. We find quantum-trajectory solutions of the Lindblad master equation, which show good agreement with experimental data and aid in finding physical explanations for the observed spectra. To further explore collision-induced spectral features, collisional loss of EIT/EIA visibility, velocity-changing and hyperfine collisions, we acquire spectra in Rb cells with 50 and 500~mTorr of Ar gas. Our work is of interest to studies of multi-level EIT systems that underpin emerging quantum technologies, where accurate accounting of internal atomic structure, laser beam geometry, optical pumping, transit time, and collisional effects is critical.