Seed laser frequency stabilization for Doppler wind lidar

We demonstrate a tunable wavelength-locked seed laser source with high-frequency stability to realize the precise measurements of global atmospheric wind field. An Nd:YAG laser at 1 064 nm is used as the master laser (ML). Its frequency is locked to a confocal Fabry-Perot interferometer by using the Pound-Drever- Hall method, which ensures the peak-to-peak value of its frequency drifts less than 180 kHz over 2 h. Another Nd:YAG laser at 1 064 nm, as the slave laser, is offset-locked to the above ML using optical phase locked loop, retaining virtually the same absolute frequency stability as the ML. The tunable ranges of the frequency differences between two lasers are up to 3 GHz, and the tuning step length was an arbitrary integral multiple of 200 kHz. The researched seed laser source is compact and robust, which can well satisfy the requirement of the Doppler wind lidar.     

Off-resonance laser frequency stabilization using the Faraday effect

We present a simple technique for stabilization of a laser frequency off resonance using the Faraday effect in a heated vapor cell with an applied magnetic field. In particular, we demonstrate stabilization of a 780 nm laser detuned up to 14 GHz from the (85)Rb D(2) 5(2)S(1/2) F = 2 to 5(2)P(3/2) F' = 3 transition. Control of the temperature of the vapor cell and the magnitude of the applied magnetic field allows locking ~6-14 GHz red and blue detuned from the atomic line. We obtain an rms fluctuation of 7 MHz over 1 h without stabilization of the cell temperature or magnetic field.     

腔外多普勒频率调制激光稳频方法的研究

利用腔外气体吸收池内的SF_6分子饱和吸收线作为参考频率,并通过振动腔外反射镜使进入吸收池的激光的频率受到多普勒调制,实现了对CO_2激光10P(16)和10P(18)支线频率的闭环锁定,最大频率漂移约为7kHz.该法得到的稳频激光输出不仅无寄生频率调制和幅度调制,并且可将激光频率锁定在独立的分子吸收线中心.     

2-microm Doppler lidar transmitter with high frequency stability and low chirp

A coherent Doppler lidar system was frequency stabilized in a master-slave configuration by a phase-modulation technique. The short-term frequency stability, ~0.2 MHz rms, was maintained in a vibrational environment on a ship during a field campaign in the tropical Pacific Ocean. The long-term frequency stability was <2.6 kHz/h. Thus, in many applications, shot-to-shot frequency correction can be disregarded, which will result in increased speed and simplicity of the data-acquisition system. A frequency chirp could not be detected. These properties permit Doppler wind measurements with high efficiency and duty cycles to be made, even on airborne and spaceborne platforms.     

A flat spectral Faraday filter for sodium lidar

We report a flat spectral Faraday anomalous dispersion optical filter (FS-FADOF) for sodium lidar. The physical and technical considerations for obtaining a FS-FADOF with a 3.5 GHz flat spectral transmission function are presented. It was found that the effective transmission of this filter was much higher (>94%) and more uniform than that of the ultranarrowband FADOF, and therefore were less sensitive to laser-frequency drift. Thus, the FS-FADOF can improve lidar efficiency and precision.     

Bichromatic laser frequency stabilization with Doppler effect and polarization spectroscopy

The interaction between polychromatic fields and atoms is an important subject in quantum optics.Frequency locking for small frequency interval multi-field is usually required in some experiments.In this letter,we experimentally demonstrate a holistic scheme for bichromatic laser frequency stabilization.Compared with traditional saturation absorption methods and complicated frequency shift schemes,offset locking for bichromatic fields is simply achieved using polarization spectroscopy and Doppler effect.Frequency locking with a wide-range asymmetry of the detuning is also shown.Our scheme makes laser spectroscopy experiments with polychromatic fields more convenient.     

Frequency stabilization of a single-frequency all-solid-state laser for Doppler wind lidar

The master laser of an injection-seeded laser for Doppler wind lidar is frequency stabilized to a FabryPerot (FP) cavity using Pound-Drever-Hall technique. The FP cavity is specially designed to gain high temperature stability with Zerodur cavity and spacer. A computer based controller is used to sample and process the error signal. After the master laser is locked, the relative frequency drift is±25 kHz in 1 s,and ±55 kHz in 1 h, which can satisfy the need of Doppler wind lidar.     

基于双F-P干涉仪的多普勒测风激光雷达的性能分析

 自行研制了一台基于双边缘技术的多普勒激光雷达,用于测量对流层大气风场。该雷达采用具有高光谱分辨率的双Fabry-Perot干涉仪来检测气溶胶后向散射的多普勒频移量。给出了多普勒测风激光雷达的结构和参数。利用干涉仪参数讨论了雷达系统的测量精度。实验测定了双干涉仪的频谱曲线。通过计算和分析,由测量的干涉仪频谱曲线的的标准偏差引起的系统测量误差为0.5 m/s。系统的测量误差随着测量的高度和所测速度的增加在增大,在高度10 km测量50 m/s的风速时系统的测量误差小于2 m/s。     

基于双F-P干涉仪的多普勒测风激光雷达的性能分析

自行研制了一台基于双边缘技术的多普勒激光雷达,用于测量对流层大气风场。该雷达采用具有高光谱分辨率的双Fabry-Perot干涉仪来检测气溶胶后向散射的多普勒频移量。给出了多普勒测风激光雷达的结构和参数。利用干涉仪参数讨论了雷达系统的测量精度。实验测定了双干涉仪的频谱曲线。通过计算和分析,由测量的干涉仪频谱曲线的的标准偏差引起的系统测量误差为0.5 m/s。系统的测量误差随着测量的高度和所测速度的增加在增大,在高度10 km测量50 m/s的风速时系统的测量误差小于2 m/s。     

Wind measurements with 355-nm molecular Doppler lidar

A Doppler lidar system based on the molecular double-edge technique is described. The system is mounted in a modified van to permit deployment in field operations. The lidar operates with a tripled Nd:YAG laser at 355 nm, a 45-cm-aperture telescope, and a matching azimuth-over-elevation scanner to permit full sky access. Validated atmospheric wind profiles were measured from 1.8 to 35 km with a 178-m vertical resolution. The range-dependent rms deviation of the horizontal wind speed is 0.4-6 m/s. The measured wind speed and direction are in good agreement with the rawinsonde wind measurements made simultaneously from the same location.     

铬原子感生荧光稳频频率稳定性的分析

激光会聚铬原子沉积实验所需时间可长达几十分钟至几个小时,实验过程中要求激光频率的波动小于5MHz,感生荧光稳频技术能够解决原子沉积实验中激光频率漂移的问题。为了保证激光频率的长时间稳定性,对稳频系统的误差信号随激光功率及原子炉温度的变化情况进行了研究。结果显示,在光强为8mW,原子炉温度为1923K时,激光频率的长期漂移可抑制到最小,在200分钟内的频率波动仅有±0.6MHz。同时,重复实验的结果也表明稳频系统具有很好的稳定性,从而为原子沉积技术提供了保障,并提高了沉积实验的重复性。     

Ramsey-CPT spectrum with the Faraday effect and its application to atomic clocks

A method that obtains the Ramsey-coherent population trapping(CPT) spectrum with the Faraday effect is investigated.An experiment is implemented to detect the light polarization components generated from the Faraday effect.The experimental results agree with the theoretical calculations based on the Liouville equation.By comparing with the method without using the Faraday effect,the potential of this method for a CPT-based atomic clock is assessed.The results indicate that this method should improve the short-term frequency stability by several times.     

一种新型的用于差分吸收激光雷达中脉冲式光学参量振荡器的种子激光器的频率稳定方法

提出了一种新型的用于差分吸收激光雷达中脉冲式光学参量振荡器的种子激光器的频率稳定方法. 详细介绍了该稳频方法的工作原理和实验装置, 并在理论上对该方法的稳频精度及其影响因素进行了分析. 利用该方法, 在实验中将种子光激光器稳定在水汽的吸收峰中心(935.6849 nm)处, 频率抖动的标准差小于8 MHz. 测试了种子注入后的光学参量振荡器输出的脉冲光的频率抖动, 测试结果表明, 脉冲光频率能够与种子光保持一致, 频率抖动的标准差小于28.7 MHz, 该稳频结果完全能够满足差分吸收激光雷达的需求.     

基于法布里-珀罗标准具的532 nm多普勒测风激光雷达系统设计和分析

设计了采用532 nm 种子注入稳频钇铝石榴石（YAG）激光器作为辐射源的基于四通道法布里-珀罗标准具的瑞利和米散射测风激光雷达系统。介绍了激光雷达的多普勒测量基本原理;给出了雷达系统的主要参数,重点对基于分子后向散射信号的外侧双通道标准具的带宽、自由谱间距、峰值间距等指标进行了详细设计与分析,确定了内侧双通道标准具参数;对全系统速度灵敏度、信噪比与探测距离的关系进行了理论模拟。结果表明,可以实现从边界层至对流层高低空一体化探测。     

All-optical pulse regeneration in an ultrafast nonlinear interferometer with Faraday mirror polarization stabilization

We demonstrate the folded ultrafast nonlinear interferometer (FUNI) as a 3R all-optical regenerator. Faraday rotation provides inherent polarization stabilization, and the optical fiber nonlinear medium provides ultrafast operation and switching window tunability. We demonstrate 3R regeneration of 10-Gbit/s data with 5-pJ pulse switching energy and 4-ps timing-jitter tolerance.     

基于法布里-珀罗标准具的532 nm多普勒测风激光雷达系统设计和分析

 设计了采用532 nm 种子注入稳频钇铝石榴石（YAG）激光器作为辐射源的基于四通道法布里-珀罗标准具的瑞利和米散射测风激光雷达系统。介绍了激光雷达的多普勒测量基本原理;给出了雷达系统的主要参数,重点对基于分子后向散射信号的外侧双通道标准具的带宽、自由谱间距、峰值间距等指标进行了详细设计与分析,确定了内侧双通道标准具参数;对全系统速度灵敏度、信噪比与探测距离的关系进行了理论模拟。结果表明,可以实现从边界层至对流层高低空一体化探测。     

Sample discrimination of frequency differences with distracters

This study examined the effect of the type and frequency range of remote frequency distracters on sample discrimination of frequency differences (SD-F). For baseline SD-F conditions, normal-hearing listeners judged frequency differences between pairs of target tones drawn from Gaussian frequency distributions near 2000 Hz. In experiment 1, the distracters were pairs of random-frequency tones, fixed-frequency tones, or noise bands, with one distracter above and one below the target region. Three frequency separations of targets and distracters were tested, none overlapping the target region. Effects of fixed-frequency or noise-band distracters were small compared to that of random-frequency distracters, which drove performance to near chance. In experiment 2, dominance of the low-frequency distracter was supported by the effects of changing distracter level, by presenting only the higher- or lower-frequency distracter, and by the pattern of weights derived from trial-by-trial responses. Performance recovered only when the lower-frequency distracter was attenuated 40-50 dB relative to the targets. In experiment 3, all stimulus distributions were shifted 2 octaves higher in frequency; the stronger influence of the distracter frequency below the target remained. The results demonstrate the importance of both stimulus variability and frequency relationships in the interaction of targets and distracters for SD-F.     

Green-pumped cw singly resonant optical parametric oscillator based on MgO:PPLN with frequency stabilization to an atomic resonance

We report on a green-pumped continuous-wave singly resonant optical parametric oscillator (cw SRO) based on MgO-doped periodically poled LiNbO₃. Operating the SRO at crystal temperatures between 40.0°C to 80.0°C an idler wavelength range of 1406–1451 nm can be accessed. The system provides stable single-frequency idler radiation of more than 300 mW at a pump power of 2 W while featuring a low threshold (<1.2 W). Above a pump power of 2.1 W we observe multimode operation, which is similar to the behavior reported for infrared-pumped SROs. To show the applicability of the device we demonstrate Doppler-free saturation spectroscopy of the cesium D₂ line using the signal wave and frequency stabilization to a crossover resonance of the D₂ transition.     

Design and performance simulation of a molecular Doppler wind lidar

A mobile molecular Doppler wind lidar at an eye-safe wavelength of 355 nm based on double-edge technique is being built in Hefei （China） for wind measurement from 10-to 40-km altitude. The structure of this lidar system is described. A triple Fabry-Perot etalon is employed as a frequency discriminator whose parameters are optimized. The receiver system is designed to achieve compactness and stability by putting in a standard 19-inch socket bench. Simulation results show that within the wind speed dynamic range of ±100 m/s, the horizontal wind errors due to noise are less than 1 m/s bdow 20-km altitude for 100-m vertical resolution, and less than 5.5 m/s from 20 km up to 40 km for 500-m vertical resolution with 400-mJ laser energy, 30-min temporal resolution, and a 45-cm aperture telescooe.