External cavity diode laser around 657 nm

Operating a laser diode in an external cavity, which provides frequency-selective feedback, is a very effective method to tune the laser frequency to a range far from its free running frequency. For the Ca atomic Ramsey spectroscopy experiment, we have constructed a 657-nm laser system based on the Littman-Metcalf configuration with a 660-nm commercial laser diode. Continuously 10-GHz tuning range was achieved with about 100-kHz spectral linewidth, measured with beat-note spectrum of two identical laser systems.     

EXPERIMENTAL STUDY ON LASER COOLING OF CESIUM ATOMS BY OPTICAL MOLASSES

We have studied the relationship between the temperature of Cs cold atoms and the parameters of the cooling laser. The atoms are first cooled and captured by a magnetooptical trap and then further coaled by optical molasses. The temperature of atoms la measured by a time-of-flight method. For relatively large laser intensity and small detuning, the temperature depends linearly on the intensity-to-detuning ratio, and nonlinear relationship has alao been found in other case.     

一套实用的铯原子喷泉光学系统的设计及建立

介绍了实现铯原子喷泉的过程及条件,并详细讨论了光路中各种光学元件对铯原子喷泉光学系统性能的影响。在对各种光学元件性能综合考虑的基础上,设计并建立了一套用于进行激光冷却和上抛的铯原子喷泉的光学系统,使光强控制、失谐调整、光束开关、光束质量等多种参量的控制达到了技术要求。在此基础上,实现了铯原子磁光阱,为实现铯原子喷泉奠定了基础。     

一种测量磁光阱中冷原子密度和温度的新方法

报道了对磁光阱中冷铯原子吸收谱的实验观察,由于冷原子的多普勒增宽远小于激光发态超精细分裂,实验观察到三个孤立的吸收峰（Cs,6S1/2,F=4→6P3／2,F＝3,4,5,）其吸收系数比为3：7：12,这与相应跃迁振子强度一致。利用吸收信号测量了冷原子云的密度.结果与荧光探测法在10％的精度内符合;用吸收信号测量了冷原子的温度,测量结果与用荧光飞行时间法和释放捕捉法的结果吻合。     

铯饱和吸收光谱随抽运光强度的变化

研究了铯饱和吸收光谱随抽运光强度变化的情况，特别是６^２Ｓ_１／２Ｆ＝４→６^２Ｐ_３／２Ｆ′＝５的谱线的变化行为．在线偏振光抽运、线偏振光检测的情况下，计入所有相关的Ｚｅｅｍａｎ子能级之间的跃迁，考虑光抽运与饱和效应的共同作用，运用Ｒｕｎｇｅ-Ｋｕｔａ法则求解粒子数方程，计算得出的饱和吸收谱与实验结果符合得较好．还给出了较直观的物理解释 关键词：     

Evaluation of Light Frequency Shift in a Caesium Beam Frequency Standard with Sharp Angle Incident Detecting Laser

Light frequency shift measured in a small optically pumped caesium beam frequency standard is reported and analysed. Two light sources, the diffused laser light scattered from the caesium beam tube parts and the fluorescence light from the beam atoms excited by the laser light, for the light frequency shift are discussed.     

Reduce of the Linewidth of a Diode Laser by Locking to a High-Finesse Fabry-Perot Cavity

We report frequency locking of a commercial 657nm diode laser to a high finesse Fabry-Perot cavity by the_ Pound-Drever-Hall method. The laser linewidth relative to the cavity is estimated to be about 6 kHz.     

Compact extended cavity diode laser system for small optically pumped cesium beam frequency standards

A compact extended cavity diode laser (ECDL) system operating at 852 nm for small optically pumped cesium (Cs) beam frequency standards was reported. ECDL and a saturated absorption spectroscopy setup were all built in an aluminum box with dimension of 10×10×7 (cm). ECDL was based on a Littman-Metcaff configuration, whose free-running linewidth was less than 600 kHz. A digital automatic frequency lock unit (AFLU) was developed to lock the laser frequency to specify Cs absorption lines automatically and re-lock it in case of lock broken. With AFLU, the laser frequency was continuously locked for several weeks.     

光抽运小型铯束频标中光频移的测量与分析

在弥漫激光场抽运斜入射光检测小型铯原子束频标实验系统上 ,对弥漫激光场产生的散射光所引起的光频移 (主要是交流斯塔克移动 )以及光抽运区产生的荧光引起的光频移对铯束频标准确度的影响作了仔细的实验测量 ,并与理论计算结果作了比较分析。测量结果表明在正常工作条件下 ,散射光引起的光频移小于 - 2× 10 -13 ,荧光引起的光频移值在 0 8× 10 -13 左右 ,这样的光频移对小型光抽运铯束频标来说是可以接受的。     

近红外光谱法田间快速估测新鲜紫花苜蓿品质

田间快速估测苜蓿品质对于适时刈割具有重要意义。试验共采集来自不同地域、不同品种、不同生育期和不同茬次的新鲜紫花苜蓿样170份,经便携式近红外光谱仪(1 100～1 800 nm)扫描得到近红外光谱,利用偏最小二乘法(PLS)在国内首次建立基于紫花苜蓿新鲜样品的干物质(DM)、粗蛋白(CP)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)化学分析值的近红外校正模型,探讨利用近红外漫反射光谱技术(NIRS)在田间快速估测紫花苜蓿品质的可行性,摸索设备选择和制样方法。四项指标所建模型的交互验证决定系数(R2CV)分别为0.831 4,0.597 9,0.803 6和0.786 1;交互验证均方根误差(RMSECV)为1.241 1,0.261 4,0.990 3和0.830 6;外部验证决定系数(R2_V)为0.815 0,0.401 1,0.784 9和0.752 1,外部预测均方根误差(RMSEP)分别为1.06, 0.31, 0.95和0.80。对于苜蓿鲜样来说,DM,NDF和ADF的近红外模型可以进行粗略的定量分析,CP的建模效果较差,但因苜蓿中的粗蛋白含量一般都能满足家畜需求,DM,NDF和ADF是在适时刈割中最关键的估测指标,DM,NDF和ADF模型可以满足田间快速估测苜蓿品质的要求。