Effects of temperature and ground-state coherence decay on enhancement and amplification in aΔatomic system

Abstract

We study phase-sensitive amplification of electromagnetically induced transparency in a warm 85 Rb vapor wherein a microwave driving field couples the two lower energy states of a Λ energy-level system thereby transforming into a ∆ system. Our theoretical description includes effects of groundstate coherence decay and temperature effects. In particular, we demonstrate that driving-field enhanced electromagnetically induced transparency is robust against significant loss of coherence between ground states. We also show that for specific field intensities, a threshold rate of groundstate coherence decay exists at every temperature. This threshold separates the probe-transmittance behavior into two regimes: probe amplification vs. probe attenuation. Thus, electromagnetically induced transparency plus amplification is possible at any temperature in a ∆ system.

Phase-sensitive amplification of an optical field using microwaves

“…More importantly, if our scheme is implemented with cold atoms, it can readily serve as an ideal interface for coherent transfer and amplification of quantum signals created in the microwave domain [29] to the optical domain. The amplification which will be obtained with such ultra-cold atoms will be several fold higher as was explicitly calculated in our earlier publication [22] Low-field-few-atom nonlinearity is a desirable goal [30] for design of quantum logic gates. In this experiment we demonstrated nonlinear amplification of the probe with very low optical densities of our Rb vapour, achieving a high gain of 7 dB with an optical density 0.45.…”

“…All our results are obtained with an optical depth of 0.45 of our atomic sample. Amplification in the probe field with a ∆ system configuration of energy levels and electromagnetic fields is possible under two-photon and three-photon resonance conditions even with a room temperature [22] sample of 85 Rb atoms. In the context of nonlinear interactions amongst the applied fields, a three-photon resonance condition δ p − δ c − δ µ = 0 is a statement of energy conservation.…”

“…In our numerical modeling based on [22], the optical probe and coupling fields are propagating fields through the vapor cell. Denoting the propagation direction as the z-axis, the fields are represented by…”

“…We explicitly include the propagation phases that give rise to an effective position-dependent microwave Rabi frequency, which is Ω µ (z) = Ω µ e iφ µ e i(k p −k c )z . Dynamical evolution of density matrix elements, in the interaction picture, is given by the master equation [22]…”

Storage and retrieval of light pulses in a fast-light medium via active Raman gain

“…Refs. [48][49][50]). However, the closed Λ systems used in all those works [47][48][49][50] are very different from our system shown in Fig.…”