Enhanced spectral profile in the study of Doppler-broadened Rydberg ensembles

Abstract

Combination of the electromagnetically-induced-transparency (EIT) effect and Rydberg-state atoms has attracted great attention recently due to its potential application in the photon-photon interaction or qubit operation. In this work, we studied the Rydberg-EIT spectra with room-temperature 87Rb atoms. Spectroscopic data under various experimental parameters all showed that the contrast of EIT transparency as a function of the probe field intensity is initially enhanced, reaches a maximum value and then decays gradually. The contrast of spectral profile at the optimum probe field intensity is enhanced by 2–4 times as compared with that at weakest intensity. Moreover, the signal-to-noise ratio of the spectrum can potentially be improved by 1 to 2 orders of magnitude. We provided a theoretical model to explain this behavior and clarified its underlying mechanism. Our work overcomes the obstacle of weak signal in the Rydberg-EIT spectrum caused by an apparent relaxation rate of the Rydberg polariton and weak coupling transition strength, and provides the useful knowledge for the Rydberg-EIT study.

Room-temperature biphoton source with a spectral brightness near the ultimate limit

“…We systematically studied the generation rate and linewidth of biphotons and the background counts as functions of the pump power, P pump , and the vapor cell temperature, T cell , [i.e., equivalently the optical depth (OD) of the atomic vapor]. P pump was varied from 2 to 16 mW, and T cell ranged between 38 and 65 • C. We kept the coupling power to 4.0 mW throughout the study, which corresponds to the Rabi frequency of 5.4Γ as determined by the EIT spectrum [47][48][49] . This coupling Rabi frequency enables the biphoton linewidths measured here to be always around 1 MHz, which is well below the natural linewidths of the atomic transitions.…”

Cavity-enhanced spectra of hot Rydberg atoms

“…通讯作者.E-mail: †gangli@sxu.edu.cn ‡tczhang@sxu.edu.cn 第一作者.E-mail: 819661603@qq.com 1 引 言 里德堡原子 [1,2] 是主量子数 n 远大于 1 的激发态原子，有较大的偶极矩和激 发态寿命。其对外界电磁场十分敏感，因此，利用里德堡原子光谱进行电磁场 的精密测量 [3][4][5][6][7] 。同时，精密的里德堡原子光谱也可以检测能级结构 [8,9] 和里德 堡原子之间相互作用 [10] 。这些测量的灵敏度取决于里德堡原子光谱的对比度、 线宽和噪声大小。因此，提高里德堡原子光谱的对比度和信噪比具有很重要的 实际意义。近年来，人们通过多种方式压窄里德堡原子光谱的线宽并提高其光 谱的对比度和信噪比。 2007 年，Adams 小组首次在 87 Rb 原子蒸气中用双光子激发的方式观测到了 里德堡原子的电磁诱导透明光谱 [11] (electro magnetically transmission 简称 EIT) 。 2011 年，杨保东等人提出了区别于传统获得 EIT 光谱的扫描方式 [11,12,13] ，通过 固定探测光频率，扫描耦合光的频率来获得无多普勒轮廓的 EIT 光谱，提高了 光谱的精度 [14] 。2017 年，Chen Yi-Hsin 小组在室温下研究了 87 Rb 原子的里德堡 原子 EIT 光谱，通过优化探测光的强度，将里德堡原子 EIT 光谱的峰值提高到 10%，此外，光谱的信噪比可以潜在地提高 1 或 2 个数量级 [15] 。2022 年，他们 小组通过优化磁场和激光的偏振，将里德堡原子 EIT 光谱的峰值提高到 13% [16] ， 提出高对比度的里德堡原子光谱可以用作量子传感器来检测环境中的电磁场。 2018 年，彭延东等人在理论上提出腔可以增强里德堡原子光谱的对比度，从而 提高微波电场测量的灵敏度 [17] ，2022 年，元晋鹏等人在实验上证实这一理论 [18] ， 用腔将里德堡原子光谱的对比度提高 7.5 倍，从而将微波场测量的灵敏度提高 了 2 倍。 本文中，我们首次从光学腔阻抗匹配 [19−21] 实验装置如图…”