用于铯原子内态操控的双光子拉曼激光的产生及应用

双光子拉曼过程是一种有效制备和控制原子内态的方法, 在原子内态操控和基于原子的量子信息处理中具有重要意义. 研制用于特定原子的拉曼激光是实现该过程的重要一步. 报道了利用光纤波导相位调制器及滤波器等实现用于铯原子内态操控的拉曼激光的方法, 并成功用于单个铯原子的内态精密操控. 通过4.6 GHz的微波信号源直接驱动波导相位调制器高效地获得光场的调制边带, 并利用自由光谱区为9.19 GHz的法布里-珀罗腔将载波及二阶边带滤掉, 获得了频率精确、相差9.19 GHz的拉曼激光. 经过基于光纤振幅调制器的功率稳定系统, 最终可以获得总功率为73 μupW、长时间内波动为2.2%的拉曼激光束, 并将此光束用于激发单个铯原子, 实现了|6S_1/2, F=4, mF=0和|6S_1/2, F=3, mF=0 之间的可控拉比操作.     

用于原子干涉仪的拉曼光的制备

原子干涉仪是利用原子物质波的特性而实现的干涉仪,广泛应用于精密测量领域.在原子干涉仪中,通过拉曼光对原子进行相干操作,拉曼光的质量直接影响着干涉仪的技术指标.基于注入锁定技术,采用普通半导体激光器、声光调制器,实现了功率、频率和位相稳定的拉曼光的制备,并对拉曼光的相位噪声技术指标进行了测试.     

粒子数转移的几种方法及比较

在理论上介绍了用非相干光和相干的激光脉冲实现二能级或三能级原子或分子能态间转移的各种方法,包括光泵浦,受激辐射泵浦,共振相干激发,受激拉曼绝热过程(STIRAP),并在转移的效率和转移速度等方面进行了比较,指出适当运用相干脉冲序列转移粒子数要优于非相干脉冲,特别是受激拉曼绝热过程(STIRAP),可以实现粒子数的完全快速转移.     

超冷原子-分子转化动力学：受激拉曼绝热过程

超冷分子是超冷原子分子物理领域的新的热点研究课题。分子具有更多的自由度,能级结构密集、复杂,直接激光冷却存在困难。目前,人们一般借助外场把超冷原子耦合获得超冷分子。受激拉曼绝热暗通道技术~(stimulated Raman adiabatic passage,STIRAP)作为其中一种非常有效地将超冷原子转化为超冷分子的方法已被广泛地研究。该文主要针对STIRAP过程中超冷原子-分子转化系统的动力学,绝热性、稳定性等理论研究的进展进行综述。     

超冷原子-分子转化动力学:受激拉曼绝热过程

获得超冷分子是超冷原子分子物理领域的新的热点研究课题。分子具有更多的自由度,能级结构密集、复杂,直接激光冷却存在困难。目前,人们一般借助外场把超冷原子耦合获得超冷分子。受激拉曼绝热通道技术(stimulated Raman adiabatic passage,STIRAP)作为其中一种非常有效地将超冷原子转化为超冷分子的方法已被广泛地研究。该文主要针对STIRAP过程中超冷原子-分子转化系统的动力学,绝热性、稳定性等理论研究的进展进行综述。     

激光诱导的四能级系统电子布居转移H

受激拉曼绝热通道(STIRAP)为我们提供了一种有效转移原子与分子中电子布居的方法.采用数值方法系统地分析了不同的四能级系统在受激拉曼迁移过程中电子布居的转移情况,计算了各种系统处于双光子共振和共振失谐时的转移率,并且讨论了在不同情况下第四能级对转移率的影响.计算结果表明,对于许多原子或分子系统,获得高的转移率所必须满足的条件是非常严格的,而有些四能级系统根本就不能获得高的转移率.(     

基于增强拉曼散射的光子-原子双模压缩态的实现

拉曼散射过程中利用原子系综中初始制备的自旋激发(原子相干性),以及注入与原子系综中初始制备的自旋激发相关联的种子光场都可以极大的提高光场频率转换的效率,实现增强拉曼散射.本文理论上计算了增强拉曼散射过程中原子-光场量子界面的正交分量的量子起伏,得到了相干性导致的增强拉曼散射,只能在一定的范围内稍微提高初始光子-原子的压缩度;而关联增强拉曼散射,能够制备很强的光子-原子间的双模压缩.这样强压缩度的光子-原子量子界面,对于利用光场和原子系统实现量子精密测量研究有着非常重要的应用.     

拉曼散射在有线电视传输中的应用

本文叙述了拉曼散射的原理,结合拉曼散射理论,讨论了光纤拉曼放大器的优缺点,并根据现阶段有线电视的传输方式和将来的发展趋势,论证了光纤拉曼放大器用于CATV的重要性和不可或缺性.     

一种增益平坦的光子晶体拉曼光纤放大器

为解决传统拉曼放大器增益系数低和增益不平坦的问题,采用级联光子晶体光纤的设计方法设计了一种增益平坦的拉曼光纤放大器.采用受激拉曼散射效应的稳态分析理论,分析了光子晶体光纤的拉曼增益谱,建立了拉曼放大器的理论模型.通过解耦合方程,推导了实现增益平坦的约束条件,发现光纤长度和泵浦功率是影响拉曼光纤放大器增益平坦度的两个参数.仿真结果表明,在1 508～1 544 nm的带宽范围内,实现了一个增益高达21 dB,增益平坦度仅为0.14 dB的光子晶体拉曼光纤放大器,可在光纤通信系统应用中发挥重要作用.     

苯C—H伸缩振动弱增益模式的受激拉曼散射

对苯的长拉曼振动模式C—H(3060 cm^-1线)伸缩振动的一阶受激拉曼散射进行了实验研究.利用在苯溶液中加入甲苯溶液,在液芯光纤内实现了苯的全对称C—H伸缩振动3060 cm^-1线的受激拉曼散射.利用等离子体解释了这一增强机理. 关键词： 液芯光纤 受激拉曼散射 等离子体     

Stimulated Raman adiabatic passage in fields with stochastic amplitudes

A theoretical analysis is presented of the effect of correlation between fluctuations of laser pulse amplitudes on population transfer between the states of a three-level atom coupled by the laser field. The carrier frequencies of the pulses are tuned to resonance with the transitions between the ground and excited states, |〈 and | 2〈, and the excited and metastable states, |2〈 and |3〈, in a lambda-type configuration. The laser pulses are timed so that population transfer between states |1〈 and | 3〈 is made possible by stimulated Raman adiabatic passage (STIRAP) in the absence of fluctuations. STIRAP does not occur when the laser fields are not correlated. When the fluctuations of one pulse amplitude duplicate those of the other, STIRAP can be observed for pulse amplitudes larger than those required in the absence of fluctuations.     

Measurement of coherence dynamics based on coherent anti-Stokes Raman scattering

Nanosecond time-resolved evolution of coherence between two nondegenerate ground levels has been investigated in Rb atomic vapor. Using STIRAP and fractional STIRAP, a time-dependent coherence is prepared and indirectly monitored by the generated coherent Raman scattering signal proportional to the coherence. The experimental data fit very well with numerical simulations. This technique have potential applications in nonlinear process based on atomic coherence.     

Stable quantum interference enabled by coexisting detuned and resonant STIRAPs

Inspired by a recent experiment [Phys. Rev. Lett. 122 253201(2019)] that an unprecedented quantum interference was observed in the way of stimulated Raman adiabatic passage(STIRAP) due to the coexisting resonant-and detunedSTIRAPs, we comprehensively study this effect. Our results uncover the scheme robustness towards any external-field fluctuations coming from laser intensity noise and imperfect resonance condition, as well as the persistence of high-contrast interference pattern even when more nearby excited levels are involved. We verify that an auxiliary dynamical phase accumulated in hold time caused by the presence of the quasi-dark state in detuned-STIRAP can sensitively manipulate the visibility and frequency of the interference pattern, representing a new hallmark to measure the hyperfine energy accurately.The robust stability of the scheme comes from the intrinsic superiority embedded in the STIRAP mechanism that preserves the coherence of population transfer, which promises a remarkable performance of quantum interference in a practical implementation.     

Broadband adiabatic conversion of light polarization

A broadband technique for robust adiabatic rotation and conversion of light polarization is proposed. It uses the analogy between the equation describing the polarization state of light propagating through an optically anisotropic medium and the Schrödinger equation describing coherent laser excitation of a three-state atom. The proposed technique is analogous to the stimulated Raman adiabatic passage (STIRAP) technique in quantum optics; it is applicable to a wide range of frequencies and it is robust to variations in the propagation length and the rotary power.     

Coherent population transfer in NO with pulsed lasers: the consequences of hyperfine structure, doppler broadening aaand electromagnetically induced absorption

Coherent population transfer between vibrational levels of the NO molecule induced by the interaction of two delayed laser pulses, also referred to as stimulated Raman scattering involving adiabatic passage (STIRAP), is studied experimentally in a molecular beam and in the bulk. The consequences of hyperfine splitting and Doppler broadening are discussed in detail. Unlike in previous studies of this kind, transfer occurs simultaneously between more than one group of non degenerate levels. In a molecular beam or in the bulk, the transfer efficiency of STIRAP exceeds that obtained by Stimulated Emission Pumping (SEP) by a factor of 3.6 or 15, respectively. We estimate the absolute transfer efficiency T in the beam to be , while is found in the bulk. In both cases, this is of the maximum value expected from numerical studies. Possible reasons for this discrepancy are discussed. Finally we show that the absorption of a pump pulse in a weakly absorbing medium is significantly enhanced by the presence of a copropagating Stokes pulse when the Rabi frequency of the latter is smaller than the width of the Doppler profile . The relation of this observation to the phenomenon of Electromagnetically Induced Transparency (EIT), which is observed for , is also discussed. Received: 11 September 1997 / Revised: 28 October 1997 / Accepted: 29 October 1997     

不同序列拉曼光脉冲对原子重力仪灵敏度的影响

研究了不同序列拉曼光脉冲对原子重力仪灵敏度的影响.结果表明,通过调节脉冲间隔可以改善原子干涉重力仪的灵敏度.在标准配置下,只考虑重力及一阶重力梯度时,三脉冲序列（π/2-π-π/2）的原子干涉重力仪具有较大的灵敏度,四脉冲序列（π/2-π-π-π/2）的原子干涉重力仪对重力不敏感,可用来测量重力梯度,五脉冲作用会降低原子干涉重力仪的灵敏度. 关键词： 原子重力仪 拉曼激光脉冲序列 灵敏度     

多波长消荧光拉曼光谱仪的研制及应用研究

拉曼光谱技术作为探究分子、晶体及其结构特征的有力手段,具有快速、无损、样品用量小、无需前处理且适应性强等优点,已被广泛应用于食品安全、石油化工等领域。但在拉曼光谱应用中,常常受到荧光背景干扰,导致拉曼信号降低,严重的情况下拉曼信号甚至会淹没在荧光背景中。为解决拉曼技术在实际应用中荧光背景干扰的问题,从仪器角度出发,采用二色镜对多波长拉曼光谱进行光路耦合设计,研制了近红外拉曼光谱与移频差分拉曼复合一体的多波长消荧光拉曼光谱检测系统,其中近红外拉曼光谱采用1 064 nm激光光源设计,移频差分拉曼光谱选取784.5和785.5 nm两组激光光源进行时分复用,在移频差分拉曼光谱检测的同时,亦可获得两组单波长拉曼光谱数据。通过对比同步测试和分时逐次测试的强度及峰位稳定性,验证了多波长消荧光拉曼光谱仪的同步测试性能;选取了多种荧光背景强弱不同的样品,进行了单波长拉曼、近红外拉曼及移频差分拉曼光谱的对比分析。针对丙酮、乙腈等荧光背景较弱的样品,可采用单波长拉曼光谱对样品进行定量及定性分析;针对食用油、红色塑胶微粒等荧光背景与拉曼信号强度相当的样品,可采用近红外拉曼光谱对样品进行定量及定性分析;针对红酒、棕色塑胶微粒等荧光背景较强的样品,需结合近红外拉曼光谱和差分拉曼光谱对样品进行定性分析。研究表明：通过多波长消荧光拉曼光谱检测系统的研制,在常规单波长拉曼光谱技术的基础上,将两种抑制荧光干扰技术有机结合,有效扩充了应用领域及样品检测范围。     

利用受激Raman跃迁制备的原子激光的相干性

研究了利用原子玻色-爱因斯坦凝聚体与光相互作用产生受激Raman跃迁制备的原子激光二阶相干性质。结果表明,这种原子激光是反聚束的,在一定条件下,是二阶相干的。