Fig. 1. (a) The Λ-type three-level scheme. (b) The experimental setup. M1 and M2, plane-concave mirrors. The polarization of the probe is horizontal and that of the coupling is vertical.

Fig. 2. (Color online) Cavity transmission spectrum versus the probe detuning in the different coupling powers at single-photon resonance (Δc=0): (I) Pc=0 (red solid line); (II) Pc=10mW (blue solid line). (III) and (IV) are the SAS (gray line) and EIT (light gray line) signals in free space, respectively. The other experimental parameters are: T=35°C, Pp=4mW.

Fig. 3. (Color online) Theoretical calculations of (a) dispersion and (b) absorption curves versus the probe frequency detuning for the Doppler-broadened medium in different cases: (1) the probe copropagates with the coupling field (red dashed lines); (2) the probe counterpropagates without the coupling field (blue solid lines). γca=γcb=2π×4.6MHz, γaa=2π×0.1MHz, Ωp=2π×2MHz, Ωc=2π×50MHz, Δc=0, and atomic density N=4.2×1015cm−3.

Fig. 4. Theoretical plots of the normalized cavity transmission function as a function of the probe frequency detuning for RC (I) (dashed line) and SC (II) (solid line). The parameters used in the calculation are: r=0.9, L≈150mm, l=75mm, and the other parameters are the same as in Fig. 3.

Fig. 5. The cavity transmission spectra versus the probe detuning at different coupling and cavity-mode detunings. The solid lines are the experimental measurement and the dashed lines are that of the theoretical simulation.

Fig. 6. Experimentally measured multipeak cavity transmission spectrum with Δc=−176MHz for different cavity-mode detunings. The experimental parameters are T=30°C, Pp=4mW, and Pc=5mW.