双光子失谐对慢光和光存储影响的实验研究

利用电磁感应透明(EIT)效应在87Rb热原子气室中进行了慢光和光存储的实验研究,在单光子红失谐650 MHz处测量了双光子失谐对光脉冲延迟和光存储的影响.结果表明:在双光子失谐0—0.5 MHz范围内存在显著的光脉冲延迟和光存储恢复信号,其慢光波形与理论计算结果基本相符;而恢复光脉冲信号随着双光子失谐的变化出现形变,这是由于多个EIT子系统之间的干涉引起的.这一研究结果为连续变量光场在热原子系综中的存储提供了实验参考.

Exp erimental study of the effects of two-photon detuning on slow light and light memory

Electromagnetically induced transparency (EIT) effect is an effective means to store light field into the atom ensemble. The extra noise introduced in the stored procedure can be suppressed greatly under the condition of large one-photon detuning and proper two-photon detuning. In this paper, we experimentally investigate the slow light and light storage in ⁸⁷Rb vapor by using EIT effect, and study the effects of the two-photon detuning on light pulse delay and light memory at 650 MHz one-photon red detuning. In order to avoid some unwanted effects under the high optical depth condition, such as four-wave mixing, etc., the temperature of the atomic cell is controlled at 65 degrees Celsius. The experimental results show that the delay and the retrieval signals are significant in a two-photon detuning range from 0 to 0.5 MHz. The pulse delay decreases with the increase of two-photon detuning. The delay is 0.36 μups at two-photon resonance, and it is 0.07 μups at 1 MHz two-photon detuning. We simulate the delayed light pulse by using a three-level Λ-type EIT model. The shapes of the measured slow light are in agreement with the theoretical results. The retrieval signals are observed at different two-photon detunings. The shapes of the retrieval pulses change with the two-photon detuning. The shape variations of the retrieval pulses cannot be explained by the three-level EIT theoretical model. By considering the atomic Zeeman sublevels interacting with the left-circular and right-circular polarized components of probe and coupling fields, multiple Λ-type EIT systems will be formed. The interference between the retrieval signals from multiple EIT subsystems causes the shape distortions of retrieval pulses. The retrieval efficiency is measured as a function of two-photon detuning. The retrieval efficiency oscillates, and multiple peaks appear with the increase of two-photon detuning. The first peak appears at two-photon resonance, and the second peak appears at 0.48 MHz two-photon detuning. Finally, we measure the retrieval efficiency as a function of the coupling power at 0.48 MHz two-photon detuning. The optimal retrieval efficiency reaches 25% when the coupling power is 100 mW. These results provide experimental reference for the quantum memory of continuous variables in the hot atom ensemble.