Enhanced vacuum Rabi splitting and double dark states in a composite atom-cavity system

Abstract

The transmission spectrum of four-level atoms in a cavity is calculated. It is shown that the four separate peaks associated with normal mode splitting and intra-cavity double dark states can be observed simultaneously. The position and intensity of the four peaks can be controlled by the intensity of the third interacting light. Therefore, the enhancement of normal mode splitting by a third coupling light of the intra-cavity four-level atoms is developed.Normal mode splitting (also called vacuum Rabi splitting at the low-photo limit in an atom-cavity system) has been considered as an important effect of the quantum nature in cavity quantum electrodynamics (CQED). Eberly first predicted that the double-peak radiation spectrum of single two-level atom appeared in the presence of a cavity field [1]. Later, it is proved that this effect also remained for a collection of N two-level intracavity atoms [2]. At the same time, the experimental studies of the vacuum Rabi frequency were carried out in the strong coupling regime of atom and cavity [3][4][5][6][7]. Up to now, the vacuum Rabi sidebands have been developed in many regimes, such as semiconductor quantum micro-cavity with quantum wells [8], photonic crystals [9], micro-disk micro-cavity [10], and hot-atoms ensemble [11]. Recently, the three-peak radiation spectrum with two vacuum Rabi sidebands and a central peak was observed in a system consisting of an optical cavity and three-level atoms [12,13]. The observation of two distinct Rabi sidebands or "cavity polaritons" could be taken as the characteristic of the multi-atom enhanced coupling of atom-cavity, while the central peak represented the dark-state polariton as the combination of cavity and the phenomenon of electromagnetically induced transparency (EIT). Since the central peak has a smaller line-width than the natural line-width and the cavity line-width, it may be used for frequency stabilization, high-resolution spectroscopic measurements or other interesting applications such as control of optical multi-stability [14,15].In this paper, we present an analysis of the transmission spectrum of a cavity with four-level atoms; four transmission peaks with two Rabi sidebands and double central peaks are obtained. Different from previous theories and experiments, the third control laser is applied in addition to coupling and probe laser, which results in the enhanced Rabi splitting and two intra-cavity dark states. This paper is structured as follows. First, we calculate the nonlinear susceptibility of a homogenouslybroadened medium of four-level atoms. Second, we qualitatively discuss the properties of Rabi sidebands and double intra-cavity dark states and make a comparison when the control laser is on or off.Considering a homogeneously broadened medium inside an optical cavity, the four-level (upper levels |a and |d , lower levels |b and |c ) N-type atomic system is shown in Fig. 1. The level |a and |b are coupled by a probe field of frequency ν p with Rabi frequency Ω p and detuning Δ p = ω ab − ν p , the l...

Enhanced Microwave Electric Field Measurement With Cavity-Assisted Rydberg Electromagnetically Induced Transparency

“…It can be found that the frequency interval of VRS becomes larger as coupling laser power increases [23]. The relationship between the VRS interval (Δ VRS ) and coupling laser Rabi frequency (Ω c ) is [33]. The amplitude and FWHM of the transmission peak of 5S 1/2 -56D 5/2 transition also gradually increase, and the corresponding amplitude (squares) and FWHM (dots) are extracted from the inset of Figure 4.…”

“…It can be seen that the VRS interval increases as atomic density increases, which is precisely controlled by changing the temperature of vapor. The VRS interval (Δ VRS ) can be expressed as Δ VRS = 2 g 2 N + Ω 2 c /4 [25,33], where Ω c is the Rabi frequency of coupling laser. However, the probe laser is vigorously absorbed for the VRS process as the atomic density increases, which results in the corresponding decrease of CAEIT amplitude.…”