Frequency stabilization of a 399-nm laser by modulation transfer spectroscopy in an ytterbium hollow cathode lamp

The modulation transfer spectroscopy in an ytterbium hollow cathode lamp at 399 nm is measured. The error signal for frequency locking is optimized by measuring the dependences of its slope, linewidth and magnitude on various parameters. Under the optimum condition, the laser frequency at 399 nm can be stabilized. The long-term stability of laser frequency is measured by monitoring the fluorescence signal of the ytterbium atomic beam induced by the locked laser. The laser frequency is shown to be tightly locked, and the stabilized laser is successfully applied to the cooling of ytterbium atoms.

Arbitrary frequency stabilization of a diode laser based on visual Labview PID VI and sound card output

We report a robust method of directly stabilizing a grating feedback diode laser to an arbitrary frequency in a large range. The error signal, induced from the difference between the frequency measured by a wavelength meter and the preset target frequency, is fed back to the piezoelectric transducer module of the diode laser via a sound card in the computer. A visual Labview procedure is developed to realize a feedback system. In our experiment the frequency drift of the diode laser is reduced to 8 MHz within 25 min. The robust scheme can be adapted to realize the arbitrary frequency stabilization for many other kinds of lasers.

High-performance frequency stabilization of ultraviolet diode lasers by using dichroic atomic vapor spectroscopy and transfer cavity

We develop a high-performance ultraviolet(UV)frequency stabilization technique implemented directly on UV diode lasers by combining the dichroic atomic vapor laser lock and the resonant transfer cavity lock.As an example,we demonstrate a stable locking with measured frequency standard deviations of approximately 200 kHz and 300 kHz for 399 nm and 370 nm diode lasers in 20 min.We achieve a long-term frequency drift of no more than 1 MHz for the target 370 nm laser within an hour,which is further verified with fluorescence count rates of a single trapped ^171Yb+ion.We also find strong linear correlations between lock points and environmental factors such as temperature and atmospheric pressure.Our approach provides a simple and stable solution at a relatively low cost,and features flexible control,high feedback bandwidth and minimal power consumption of the target UV laser.

Improvement of Laser Frequency Stabilization for the Optical Pumping Cesium Beam Standard

A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an important factor that limits the long-term frequency stability. We minimize the drift of the light angle by using a fiber- coupled output, and lock the frequency of a distributed-feedback diode laser to the fluorescence spectrum of the atomic beam. The measured frequency stability is about 3.5 ×10^-11 at i s and reaches 1.5 × 10^-12 at 2000s. The Allan variance keeps going down for up to thousands of seconds, indicating that the medium- and long-term stability of the laser frequency is significantly improved and perfectly fulfills the requirement for the optical pumping cesium clock.

Anomalous Variation of Beat Frequency in a Dual Frequency He-Ne Laser

The beat frequency in a dual frequency He-Ne laser varies while the resonant cavity length is tuned. As to the laser with two longitudinal modes, the variation amplitude is commonly less than 500 kHz, proven by experiments and theories. This study reveals an anomalous variation of the beat frequency when a piece of element is put into the cavity and is aligned with the laser axis. Consequently the variation amplitude couM reach 22 MHz, several dozen times larger than that without the intra-cavity element. This cannot be explained only by laser mode pulling and pushing effects. Some influencing factors are investigated experimentally, including the tilted angle of the element and the distance between its surface and cavity mirror. The qualitative analysis is discussed, which agrees with the experimental results.

基于声光调制器的光学锁相环He-Ne激光稳频方法研究

报道了一种基于声光调制器与光学锁相环相结合的高稳定度激光稳频方法,用于提高热稳频He-Ne激光器的频率稳定度和准确度。为了克服全内腔热稳频He-Ne激光精密调谐困难的缺点,发展了基于声光调制器两次移频的频率调谐光路,有效地消除声光调制器移频光束路径对衍射角θ的依赖。自行研制了具有高灵敏度与捕获带宽的光学锁相环系统,利用声光调制器的高频率响应特性实现热稳频He-Ne激光高速、准确的锁定。成功实现了热稳频He-Ne激光器偏频锁定至碘稳频HeNe激光器。实验结果表明,环路锁定后拍频频率波动在±0.2 Hz范围内,频率抖动的标准差为0.04。偏置频率为30 MHz时,系统在1 s和1000 s积分时间的相对阿伦方差分别为3.3×10^(-9)和1.4×10^(-12)。系统锁定后,压缩后的拍频线宽小于2 kHz。该研究表明,采用基于声光调制器与光学锁相环相结合的激光稳频方法可以实现亚赫兹级的激光频差控制,通过将热稳频He-Ne激光器偏频锁定至高稳定度的参考激光源可以显著提升其频率稳定度和准确度。

633 nm热稳频He-Ne激光真空波长校准研究

633 nm热稳频He-Ne激光是激光干涉测量技术中应用最广泛的波长标准光源。633 nm激光波长是几何量计量中最重要的溯源路径。该文分析了633 nm热稳频He-Ne激光的频率特性,并以此为依据详细探讨了633 nm热稳频He-Ne激光器真空波长的校准内容和校准方法。在激光平均波长测量和波长不确定度评定中均考虑了波长复现性产生的影响,给出了校准数据处理方法和不确定度评定示例。结果显示,在633 nm热稳频He-Ne激光真空波长校准中,考虑复现性的影响是必要的。

A long-term frequency-stabilized erbium-fiber-laser-based optical frequency comb with an intra-cavity electro-optic modulator

We demonstrate an optical frequency comb based on an erbium-doped-fiber femtosecond laser with the nonlinear polarization evolution scheme. The repetition rate of the laser is about 209 MHz. By controlling an intra-cavity electro- optic modulator and a piezo-transducer, the repetition rate can be stabilized with a high-bandwidth servo in a frequency range of 3 kHz, enabling long-term repetition rate phase-locking. The in-loop frequency stability of repetition rate is about 1.6× 10-13 in an integration time of 1 s, limited by the measurement system; and it is inversely proportional to integration time in the short term. Furthermore, using a common path f-2f interferometer, the carrier envelope offset frequency of the comb is obtained with a signal-to-noise ratio of 40 dB in a 3-MHz resolution bandwidth. Stabilized cartier envelope offset frequency exhibits a deviation of 0.6 mHz in an integration time of 1 s.

A New Kind of Self-Frequency-Stabilization 1.3μM Single Frequency Coherent Source with 10MW and a Spectrum Linewidth in the Order of Kilohertz

The design of 1.3μm He-Ne single frequency laser for optical fiber communication is in-troduced.The scheme for obtaining steady single-mode oscillation by raising gas pressureand the method of getting linear-polarization single frequency output by longitudinal Zeemaneffect are present.The relations of linewidth to some factors are discussed.

Dual-mode stabilization for laser to radio-frequency locking by using a single-sideband modulation and a Fabry-Pérot cavity

The dual-mode stabilization scheme has been demonstrated as an efficient way to stabilize laser frequency.In this study,we propose a novel dual-mode stabilization scheme that employs a sizable Fabry-Pérot cavity instead of the microcavity used in previous studies and has enabled higher bandwidth for locking.The results demonstrate a 30-fold reduction in laser frequency drift,with frequency instability below 169 kHz for integration time exceeding 1 h and a minimum value of 33.8 kHz at 54 min.Further improvement could be achieved by optimizing the phase locking.This scheme has potential for use in precision spectroscopic measurement.

Flexible control of semiconductor laser with frequency tunable modulation transfer spectroscopy

We introduce a new method of simultaneously implementing frequency stabilization and frequency shift for semiconductor lasers. We name this method the frequency tunable modulation transfer spectroscopy （FTMTS）. To realize a stable output of 780 nm semiconductor laser, an FTMTS optical heterodyne frequency stabilization system is constructed. Before entering into the frequency stabilization system, the probe laser passes through an acousto-optical modulator （AOM） twice in advance to achieve tunable frequency while keeping the light path stable. According to the experimental results, the frequency changes from 120 MHz to 190 MHz after the double-pass AOM, and the intensity of laser entering into the system is greatly changed, but there is almost no change in the error signal of the FTMTS spectrum. Using this signal to lock the laser frequency, we can ensure that the frequency of the laser changes with the amount of AOM shift. Therefore, the magneto-optical trap （MOT）-molasses process can be implemented smoothly.

Stable continuous-wave single-frequency intracavity frequency-doubled laser with intensity noise suppressed in audio frequency region

We demonstrated a continuous wave(cw) single-frequency intracavity frequency-doubled Nd:YVO_4/LBO laser with 532 nm output of 7.5 W and 1.06 μm output of 3.1 W, and low intensity noise in audio frequency region.To suppress the intensity noise of the high power 532 nm laser, a laser frequency locking system and a feedback loop based on a Mach-Zehnder interferometer were designed and used.The influences of the frequency stabilization and the crucial parameters of the MZI, such as the power splitting ratio of the beam splitters and the locking state of the MZI, on the intensity noise of the 532 nm laser were investigated in detail.After the experimental optimizations, the laser intensity noise in the frequency region from 0.4 kHz to 10 kHz was significantly suppressed.

Study of a low power dissipation,miniature laser-pumped rubidium frequency standard

This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping ^87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line, it records a 5 × 10^-11τ-1/2 （τ〈500 s） frequency stability with a table-top system in a primary experiment. The study reveals that the evaluated scheme is at the level of 2.7 watts power consumption, 90 cm^3 volume and 10^-12τ-1/2 short-term frequency stability.

高功率碘稳频He-Ne激光波长参考源

为满足精密测量对高稳定激光单色光源功率的要求,研制了全封闭、一体化结构的高功率碘稳频He-Ne激光系统。对该系统所采用的饱和光谱探测原理、吸收峰识别与锁定方法以及激光波长的稳频效果进行了研究。首先,介绍了三次谐波方法探测饱和吸收光谱的基本原理,分析了其消除功率背景的方法。接着,分析了碘稳频激光中一体化谐振腔的稳定性,详细讨论了谐振腔轴向膨胀和横向非对称形变对输出功率的影响。然后,分析了激光输出功率与碘分子饱和吸收峰之间的对应关系,介绍了利用二次谐波信号实现吸收峰识别的可行性,并展示了高稳定谐振腔的长时间锁定能力。最后,分析了高功率碘稳频He-Ne激光波长的稳定度与复现性。实验结果表明:高功率碘稳频He-Ne激光波长抖动标准差为33 kHz,1 000 s稳定度达到4.1×10^(-13);三个月内激光波长的复现性达到3.3 kHz (7.0×10^(-12)),与国际计量委员会推荐的频率差为3.0 kHz。

弹性加力中频差He-Ne塞曼-双折射双频激光器及稳频

为了提高激光干涉仪的测量速度,研制了一种新型塞曼-双折射双频激光器(Z-B激光器),该激光器对增益管加横向磁场和对其"透射反射镜"加外力。采用了弹性加力方案,使其频差比刚性加力He-Ne激光器具有更高的赋值精度,达到±0.2MHz。同时,还报道了对该激光器进行的稳频研究。利用调谐腔中平行光和垂直光的等光强点作稳频点,以光强平衡为依据设计热伺服控制电路,考虑了成本的最小化和系统的集约化,采用纯模拟元件实现了中频差He-Ne Z-B激光器频率的稳定。对频差5.4MHz的Z-B激光器的稳频结果为:3h稳频精度优于2.1×10-8。

612nm He-Ne兰姆凹陷稳频激光系统

研制了外腔式单频兰姆凹陷612nm He-Ne激光器。激光输出端输出功率≥0.2mW,单频调谐范围为680MHz。稳频激光系统以PZT为执行元件,以兰姆凹陷中心频率为参考,用稳频系统锁定于凹陷中心。

双纵模稳频He-Ne激光器工作机理及误差分析

为深入分析双纵模稳频氦氖激光器的稳频机理和精度误差，本文提出了双纵模产生的必要条件：内腔型激光器和谐振腔长在100～300mm之间。按照激光器的工作过程，稳频分为三个阶段：跳模、过渡阶段，模式稳定。结合激光原理和热力学理论，根据光电探测器的电压变化，阐述了稳频机理。拍频实验结果表明，激光器的频率稳定度高达5×10^10。通过误差分析，确定稳频精度仅取决于腔长的变化量，且增加腔长，有助于增加频率稳定度。该方法锁定时间短。

Long-term ultrastable frequency dissemination via a 50-km spooled fiber link using a two-section DFB laser

The stable long-distance transmission of radio-frequency(RF)signals holds significant importance from various aspects,including the comparison of optical frequency standards,remote monitoring and control,scientific research and experiments,and RF spectrum management.We demonstrate a scheme where an ultrastable frequency signal was transmitted over a 50 km coiled fiber.The optical RF signal is generated using a two-section distributed feedback(DFB)laser for direct modulation based on the reconstruction equivalent chirp(REC)technique.The 3-dB modulation bandwidth of the two-section DFB laser is 18 GHz and the residual phase noise of-122.87 dBc/Hz is achieved at 10-Hz offset frequency.We report a short-term stability of 1.62×10^(-14)at an average time of 1 s and a long-term stability of 6.55×10^(-18)at the measurement time of 62,000 s when applying current to the front section of the DFB laser.By applying power to both sections,the stability of the system improves to 4.42×10^(-18)within a testing period of 56,737 s.Despite applying temperature variations to the transmission link,long-term stability of 8.63×10^(-18)at 23.9 h can still be achieved.

基于温度闭环反馈的He-Ne激光器热稳频系统

为了提升激光回馈测量系统中He-Ne激光器的性能,解决激光回馈镜不断移动时频率无法使用传统方法稳定的技术问题,采用基于温度反馈控制激光器管体温度的闭环被动稳频的方法,进行了理论分析和实验验证,研究了不同管体温度与环境温度差值下频率稳定性。结果表明,系统最佳温差为25.6℃;在此温差条件下稳频后,He-Ne激光器波长波动范围达10^(-4),即频率稳定性达到1.61×10^(-7),功率漂移量低于3.20%。该系统可以根据环境温度的变化调节稳频温度点,并且稳频结构简单,满足激光回馈一般应用系统稳定性的要求。

全内腔式632.8nm He-Ne激光器频率稳定的新方法

本文探讨了全内腔式632.8nm He-Ne激光器频率稳定的必要条件,对稳频原理进行了较详细的阐述,提出了检测激光管温度与提取激光输出信号相结合的稳频方法。通过实验获得了满意的结果。