半导体泵浦铯蒸气实现激光输出

采用线宽0.26nm的Littrow外腔巴条半导体激光器泵浦增益长度8mm缓冲气体为80kPa甲烷的铯(Cs)蒸气室,在Cs蒸气室温度120℃时,我们获得了394mW的894.6nm线偏振Cs蒸气激光,光光效率7.4%,斜率效率11.2%,阈值功率为1.72W。     

Diode-pumped 10 W continuous wave cesium laser

An efficient cesium vapor laser pumped with a continuous wave laser diode array has been demonstrated. The linewidth of the pump source was narrowed using the external cavity to match it to the cesium absorption line. The output power of the continuous wave cesium laser was 10 W, which exceeds previous results by more than a factor of 10, and the slope efficiency was 68%. The overall optical efficiency was 62%, which is a factor of 6 higher than previous pulsed laser results for alkali lasers with diode laser array pumping.     

A kinetic model for diode pumped Rubidium vapor laser

A physical model is established to describe the kinetic processes and laser mechanism of diode pumped rubidium vapor laser. Influences of some parameters such as the output coupler reflectivity, the cell length, the temperature and the buffer gases on the output power and the optical–optical efficiency are calculated and analyzed. The simulation results agree well with the experiments. A set of optimization parameters is obtained for designing an efficient diode pumped Rb vapor laser.     

Analysis of temperature distributions in diode-pumped alkali vapor lasers

Assuming the pump light to be a Gaussian beam and considering the medium absorption, we establish the heat conduction model to describe the temperature distribution in diode-pumped alkali vapor lasers (DPALs) with two different pumping ways. Combining with the experimental parameters in cesium laser, the spatial temperature distribution picture, the longitudinal and the radial temperature distributions of two cesium lasers are obtained by numerical solving the model. Influences of the pump power, the beam waist and the absorption coefficient on the axial and the radial temperature distribution are calculated and compared for the two Cs lasers. The result suggests that Cs laser pumped by two laser diode arrays can improve the spatial temperature distribution condition and reduce the longitudinal temperature gradient, which is good for reducing the thermal effects and improving the output characteristics of DPALs.     

光泵铯蒸气激光的动力学模型

建立了一个物理模型描述了光泵铯蒸气激光的动力学过程和激光机理.结合实验参量,经数值求解该模型,定量分析了抽运光参量、缓冲气压和输出镜反射率等对激光输出功率和光光效率产生的影响,得到了与实验基本一致的模拟结果.表明该模型较好地反映了光泵銫蒸气激光的动力学机理和发射过程,为该类激光的优化设计提供了借鉴和参考.     

室温下光纤耦合二极管泵浦Tm:YAP激光器

 为实现室温下小型化、高效率的1.9 mm激光输出,采用793.5 nm激光二极管泵浦Tm:YAP晶体，晶体采用热电制冷及风冷的方式控制在18 ℃，采用1∶1的聚焦耦系统，获得功率为2.2 W、中心波长为1 928 nm的激光输出，光光转换效率为31%，斜率效率达41%。对影响激光输出的耦合输出率、腔型、腔长、晶体工作温度等因素进行了实验分析，实验结果表明：输出功率的变化与温度基本成线性关系,当增加激光谐振腔长时，由于高阶模式损耗加大以及晶体热透镜效应的加重导致腔内损耗加大，输出功率和斜率效率都有所下降。     

A direct frequency comb for two-photon transition spectroscopy in a cesium vapor

A phase-stabilized femtosecond frequency comb is used to measure high-resolution spectra of two-photon transition 62S1/2-62P1/2,3/2-82S1/2 in a cesium vapor.The broadband laser output from a femtosecond frequency comb is split into counter-propagating parts,shaped in an original way,and focused into a room-temperature cesium vapor.We obtain high-resolution two-photon spectroscopy by scanning the repetition rate of femtosecond frequency comb,and through absolute frequency measurements.     

Nonlinear spectroscopy with a vertical-cavity surface-emitting laser (VCSEL)

We have evaluated the suitability of a vertical-cavity surface-emitting laser diode (VCSEL) for spectroscopic applications. Despite its low output power it is possible to observe narrow resonances in a saturated absorption spectroscopy experiment on the cesium D ₂ transition at 852 nm, limited in width by the laser linewidth of several tens of MHz. High modulation efficiency of the VCSEL allows us to create modulation sidebands at 9.2 GHz frequency via direct modulation of the laser injection current. Using the carrier and either one of the sidebands coherent population trapping (CPT) resonances in a buffered cesium vapor can be prepared with linewidths below 130 Hz. With this very compact setup we have studied the dependence of CPT resonance position and linewidth as a function of optical detuning and find evidence of the influence of the excited state hyperfine structure. Received: 30 April 1999 / Revised version: 25 June 1999 / Published online: 30 November 1999     

LED pumped polymer laser sensor for explosives

A very compact explosive vapor sensor is demonstrated based on a distributed feedback polymer laser pumped by a commercial InGaN light‐emitting diode. The laser shows a two‐stage turn on of the laser emission, for pulsed drive currents above 15.7 A. The ‘double‐threshold’ phenomenon is attributed to the slow rise of the ∼30 ns duration LED pump pulses. The laser emits a 533 nm pulsed output beam of ∼10 ns duration perpendicular to the polymer film. When exposed to nitroaromatic model explosive vapors at ∼8 ppb concentration, the laser shows a 46% change in the surface‐emitted output under optimized LED excitation.     

铯原子nP_(3/2)(n=70—94)里德伯态的紫外单光子激发及量子亏损测量

基于成熟的光纤激光器、光纤放大器及高效激光频率转换技术,我们在实验中研制了一套瓦级输出的窄线宽连续波单频可调谐318.6 nm紫外激光系统,并在室温铯原子气室中实现了6S_(1/2)—nP_(3/2)(n=70—94)单光子跃迁里德伯激发.借助由铯原子6S_(1/2)(F=4)基态、6P_(3/2)(F′=5)激发态和nP_(3/2)(n=70—94)里德伯态构成的V型三能级系统,通过频率锁定于铯原子6S_(1/2)(F=4)—6P_(3/2)(F′=5)超精细跃迁的852.3 nm探测光束的吸收减弱信号获得了里德伯态的信息,并利用高精度波长计测量了铯原子nP_(3/2)(n=70—94)里德伯态的量子亏损值.经过与理论计算值的变化趋势进行对比,我们认为由于原子气室的里德伯屏蔽效应并不能完全屏蔽外部直流电场,铯原子气室内存在残余的直流电场,影响了对里德伯态的量子亏损值的实验测量.利用残余直流电场的Stark效应理论模型及其与有效主量子数n*的依赖关系,对铯原子里德伯态的量子亏损实验测量值进行了修正.修正后的铯原子nP_(3/2)(n=70—94)态量子亏损测量值为3.5591±0.0007,与理论计算值相吻合.     

Thermal-energy Pooling Collisions in Cesium Vapor6P3/2+6P3/2→7PJ+6S1/2

In this paper, the results of an experimental study on 6P3/2+6P3/2→7PJ+6S1/2 energy pooling collisions are presented. The experiment was carried out in cesium vapor using an external cavity diode laser for excitation under different temperatures. It is found that the response of fluorescence intensity to the frequency of excitation laser shows a two-peak phenomenon.     

Thermal-energy Pooling Collisions in Cesium Vapor 6P_(3/2) 6P_(3/2) →7P_J 6S_(1/2)

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基于艳原子线性法拉第磁光效应的应用

分析了(銫) (Cs)原子作为旋光介质的线性法拉第磁光效应.采用二能级模型解释了(銫)原子与光的相互作用,并利用琼斯矩阵推导了当激光器的频率处于(銫)原子共振线时,经过(銫)气室的线偏振光的旋转角与外加磁场的关系式,利用此关系式可测量磁场强度的大小和气室内(銫)原子的浓度.实验采用852nm分布反馈半导体激光器作为光源...     

CPT原子钟参数设计及其光谱实验研究

通过建立被动型CPT铯原子钟的理论模型,开展CPT信号与铯原子气室特性参量间关系的仿真分析和研究,建立铯原子气室设计及分析方法,得到了被动型CPT铯原子钟最佳设计参数,直径10 mm、长度10 mm、缓冲气体为N₂的圆柱形铯原子气室,最佳工作参数为：工作温度为320 K、气体压强值50 Torr。并经多波长多普勒吸收光谱、CPT信号锁定及频率稳定度测试等实验,验证了理论模型的正确性,为开展高性能芯片级CPT铯原子钟的设计、参数优化提供了一种研究方法。     

Laser frequency stabilization based on Sagnac interferometric spectroscopy

A simple method based on Sagnac interferometric spectroscopy (SIS) is applied for frequency stabilization of diode lasers. Sagnac interferometric spectra of rubidium vapor are investigated both theoretically and experimentally. The interference signal at the output of the Sagnac interferometer displays a sharp dispersion feature near the atomic resonance. This dispersion curve is used as the feedback error signal to stabilize the laser frequency. Linewidth of a diode laser is stabilized down to 1 MHz by this modulation-free method.     

808 nm高占空比大功率半导体激光器阵列

 采用渐变折射率分别限制单量子阱宽波导结构,通过降低非辐射复合、有源层载流子泄露、散射和吸收损耗来提高出射效率和降低激光阈值电流,从而提高半导体激光器阵列的输出功率;同时使P面具有更高的粒子掺杂数密度,优化N面合金条件,降低半导体激光器的串联电阻,降低焦耳热,提高了半导体激光器阵列的转换效率。利用金属有机化学气相淀积技术生长GaInAsP/InGaP/AlGaAs渐变折射率分别限制单量子阱宽波导结构激光器材料,利用该材料制成半导体激光线阵列在20%高占空比的输入电流下,半导体激光器的输出峰值功率达到189.64 W(180 A),斜率效率为1.1 W/A,中心波长为805.0 nm,阈值电流为7.6 A,电光转换效率最高可达55.4%;在1%占空比的输入电流下,阵列的输出峰值功率可达324.9 W(300 A),斜率效率为1.11 W/A,阈值电流为7.8 A,电光转化效率最高达55.6%,中心波长为804.5 nm。     

Analytical and Experimental Studies on Nd:YVO4/KTP Lasers Pumped by High-brightness Laser Diodes

We report analytical and experimental studies on the characteristics of a high-brightness laser diode endpumped Nd:YVO₄/KTP laser. A simple model was developed to optimize the cavity parameters and estimate the green output power of intracavity frequency doubled lasers. Using a 1 W high-brightness laser diode as the pump source, high efficiency operation was realized. The second-harmonic output power at 532 nm was measured to be 286.5 mW at an incident pump power of 881.4 mW, corresponding to an optical to optical efficiency of 32.5%.     

Modeling of an alkali vapor laser MOPA system

A physical model is established to describe the kinetic processes and the laser amplification in an alkali vapor laser MOPA system. The good agreement between the simulation and the experiment result shows the validation of the model. Influences of some parameters such as the working temperature, the pump power and the cell length on the output performance are calculated and analyzed. A better set of working parameters is achieved for improving the output characteristics of an optically pumped alkali laser MOPA system.     

Selective reflection by atomic vapor: experiments and self-consistent theory

Selective reflection of laser radiation from the interface between atomic vapor and a dielectric is studied for a wide range of vapor density. A self-consistent model is developed, some analytical results are obtained, as well as a number of curves are computed that are in good agreement with experimental spectra measured in cesium and rubidium vapor cells.     

Cesium 6S(1/2) --> 8S(1/2) two-photon-transition-stabilized 822.5 nm diode laser

A cesium 6S(1/2) --> 8S(1/2) two-photon-transition (TPT)-stabilized 822.5 nm diode laser is reported for the first time to our knowledge. Allan deviation of 4.4 x 10(-13) (60 s) was achieved, and the possible systematic errors were evaluated as smaller than 2 kHz. We demonstrate that the cesium TPT-stabilized diode laser could be a reliable frequency reference at 822.5 nm wavelength.