Transients in all-optical bistability using transverse optical pumping: Observation of critical slowing down

We report on the transient response of an all-optical bistable device to step-inputs of light. The nonlinear mechanism used for bistable switching relies on transverse optical pumping within the Zeeman sublevels of the sodium ground state. Our measurements demonstrate the crucial role of critical slowing down for switching time. We also find that time-dependent diffusion processes can strongly affect the dynamics of this bistable device. Numerical calculations are shown to yield results in satisfactory agreement with experimental data.     

The “lamp-laser”: Realization of a very long cavity dye laser

We describe in this paper a 17 m long cw dye laser, having a splitting between longitudinal mode frequencies of 8.8 MHz. Power, stability and spectral characteristics are specified. The detailed mode structure is shown to depend strongly on the position of the active medium inside the laser cavity. Applications to different physical problems are considered.     

Single atom as a mirror of an optical cavity

By tightly focusing a laser field onto a single cold ion trapped in front of a far-distant dielectric mirror, we could observe a quantum electrodynamic effect whereby the ion behaves as the optical mirror of a Fabry-Pérot cavity. We show that the amplitude of the laser field is significantly altered due to a modification of the electromagnetic mode structure around the atom in a novel regime in which the laser intensity is already changed by the atom alone. We propose a direct application of this system as a quantum memory for single photons.     

Towards a monolithic optical cavity for atom detection and manipulation

We study a Fabry-Perot cavity formed from a ridge waveguide on a AlGaAs substrate. We experimentally determined the propagation losses in the waveguide at 780 nm, the wavelength of Rb atoms. We have also made a numerical and analytical estimate of the losses induced by the presence of the gap which would allow the interaction of cold atoms with the cavity field. We found that the intrinsic finesse of the gapped cavity can be on the order of F∼30, which, when one takes into account the losses due to mirror transmission, corresponds to a cooperativity parameter for our system C∼1.     

Feedback control of a single atom in an optical cavity

We discuss feedback control of the motion of a single neutral atom trapped inside a high-finesse optical cavity. Based on the detection of single photons from a probe beam transmitted through the cavity, the position of the atom in the trap is estimated. Following this information, the trapping potential is switched between a high and a low value in order to counteract the atomic motion. This allowed us to increase the storage time by about one order of magnitude. Here, we describe the technical implementation of the feedback loop and give a detailed analysis of its limitations as deduced from Monte-Carlo simulations. We also discuss different strategies to further improve the performance of the feedback.     

Continuous optical discharge in a laser cavity

Optical discharge in a laser cavity is experimentally studied. A significant increase in the absorption of laser radiation (up to total absorption) is revealed. Optical schemes for initiation and maintaining of optical discharge in the cavity are proposed for technological applications of the optical discharge.     

光学PAM-PDM转换:光学临界慢变效应的一种应用

基于光学临界慢变效应对光学双稳器件本文提出了一种新的功能——光学脉冲振幅调制(PAM)到光学脉冲持续时间调制(PDM)的转换,并且在实验上证实了这种功能的可行性.     

Initial results utilizing optical pumping with a laser to produce spin-polarized hydrogen

Spin-polarized hydrogen was produced by laser optical pumping of rubidium and subsequent spin exchange with hydrogen atoms created by an rf discharge. Initial experiments produced approximately 10¹⁴ hydrogen atoms with a polarization of about 64%. Utilization of a suitable wall coating will allow significant improvement in these results.     

Enhanced cooling of a V-type three-level atom in an optical cavity

We have studied theoretically and numerically the enhanced cooling of a V-type three-level atom in a high-finesse optical cavity and shown that the cooling rate can be increased by one order of magnitude over that of a two-level atom, and the momentum amplitude tends to a stationary state much smaller than that of a two-level atom. We have further shown that the cooling rate can be significantly improved by using feedback and a time-dependent pump.     

二能级原子与高品质因子腔的自发辐射特性

用全量子理论研究二能级原子单模腔耦合系统,通过理论推导和数值计算得出系统的自发辐射光谱和平均粒子数密度.共振时腔与原子的发射光谱在强耦合与弱耦合区域有所不同,腔发射光谱分裂只出现于强耦合区域,而原子发射光谱由于腔感应透明效应在弱耦合区域出现了缺口.本文系统地研究了原子与腔在失谐时的发射光谱,在好腔机理(腔线宽小于原子线宽g)原子与腔即使在大失谐时腔发射出腔频率的光子,这给当前实验上困惑的特性提供了一个理论依据.为了给腔感应透明效应一个新的深入了解,还研究了原子与腔平均粒子数密度随时间的演化,以及平均粒子数密度与光强度之间的关系. 关键词： 自发辐射 强耦合 腔感应透明 好腔机理     

Kinetics of helium 3 laser optical pumping

We report on optical pumping experiments in helium-3 using a new broad-band, all fiber laser at 1083 nm. The kinetics of polarization build-up are compared to the numerical results of an appropriate model. Effects of laser power and bandwidth are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Coupling laser radiation to a fabry-perot cavity with a single-mode optical fiber

Three aspects of coupling to Fabry-Perot cavities used in optical frequency standards are discussed: the use of a single-mode optical fiber to maintain coupling stability while improving vibration isolation of the cavity, the required stability of the coupling geometry, and the phase and polarization variations resulting from fiber movement. Optical fiber coupling should be useful when laser linewidths and stabilities at the Hertz level are desired.     

Modulation-free optical locking of an external-cavity diode laser to a filter cavity

Optical locking to a filter cavity is an effective method to eliminate the limitations of an external-cavity diode laser, such as broad spontaneous emission backgrounds and frequency jitters. Stable operation of the optical locking requires simultaneous control of the feedback phase and the diode-laser frequency. Frequency dither is usually used to extract the two error signals, but this causes extra frequency modulation in the output beam. A modulation-free method for deriving the error signals by modulating the laser-cavity coupling strength is demonstrated with a violet diode laser. A modulation-free linewidth upper limit of about 7 kHz for a 1 s measurement is realized by the method.     

光外差腔衰荡光谱理论研究

提出了简化的光外差腔衰荡光谱技术，避免了通常腔衰荡光谱对衰荡时间的直接测量，同时消除了腔镜损耗的共模直流信号的测量.理论上其测量灵敏度可以达到量子噪声极限，而且技术实现相对简单，更适合于分子振转光谱研究.此外，还在理论上分析了该光谱技术具有的Gauss线型的一次微分光谱线型的特点，并讨论了一些实验参量对谱线强度和线型的影响，进而给出了最佳实验参量. 关键词： 光外差 腔衰荡光谱     

Feedback on the motion of a single atom in an optical cavity

We demonstrate feedback on the motion of a single neutral atom trapped in the light field of a high-finesse cavity. Information on the atomic motion is obtained from the transmittance of the cavity. This is used to implement a feedback loop in analog electronics that influences the atom's motion by controlling the optical dipole force exerted by the same light that is used to observe the atom. In spite of intrinsic limitations, the time the atom stays within the cavity could be extended by almost 30% beyond that of a comparable constant-intensity dipole trap.     

Raman lasing with a cold atom gain medium in a high-finesse optical cavity

We demonstrate a Raman laser using cold (87)Rb atoms as the gain medium in a high-finesse optical cavity. We observe robust continuous wave lasing in the atypical regime where single atoms can considerably affect the cavity field. Consequently, we discover unusual lasing threshold behavior in the system causing jumps in lasing power, and propose a model to explain the effect. We also measure the intermode laser linewidth, and observe values as low as 80 Hz. The tunable gain properties of this laser suggest multiple directions for future research.     

Semiconductor optical amplifier-based laser with 25 km long cavity length utilizing sagnac fiber ring structure

In the investigation, we propose and demonstrate a Sagnac ring based fiber laser structure using a semiconductor optical amplifier (SOA) to act as a gain medium with short to long fiber cavity lengths for wavelength lasing and tuning. Here, ten fiber Bragg gratings (FBGs) with different reflected Bragg wave-lengths are used serving as the reflected element in the proposed laser configuration for wavelength lasing and remote sensing simultaneously. Furthermore, the different cavity fiber lengths of a few ten m to 25 km, which are used in the proposed laser scheme, has been analyzed and discussed.