激光双法-珀干涉纳米测量系统总体设计

设计了一套集光、机、电为一体的新型纳米测量系统:以激光为光源、双法珀干涉仪及轻拍式探针为纳米传感部件、以柔性铰链机构的微动工作台为纳米扫描测试系统,并采用计算机数字PID实时控制处理;提出了通过测量双法珀干涉仪透射光强基波幅值差或基波等幅值过零时间间隔的方法进行纳米测量的理论基础;理论分析了检测探针振动的方法;给出了基于柔性铰链机构的微动工作台的有限元设计新方法;设计了以电容传感器为精密位置反馈的PID闭环控制系统,解决了压电陶瓷等元件对系统造成的非线性影响;对系统误差进行了分析。     

以激光冷却干涉仪反射镜

法国高师、皮埃尔和玛丽·居里大学的研究人员报道了用激光冷却反射镜 ,可提高干涉仪测量精度。由固有热噪声导致的布朗运动是干涉仪引力波探测器精度的最大障碍。该组用 810 nm Ti∶蓝宝石激光注入反射镜后高精密腔产生的同相振动测量布朗运动。用腔信号的反馈环路调制 50 0 m W辅助光 ,以减弱相位噪声。研究人员称 ,该系统可在不影响装置灵敏度的情况下将干涉仪的热噪声减至 1/ 2 0。以激光冷却干涉仪反射镜     

632.8nm高精度移相菲佐干涉仪测量误差分析

为了满足高精度光学系统对光学元件纳米级的检测精度要求,提出了一种理论可实现纳米级测量的632.8nm移相菲佐干涉仪的设计方案。通过对检测凹面和凸面的632.8nm移相菲佐干涉仪的基本结构和测量原理的分析,指出影响干涉仪测量精度的几种主要误差:移相误差、几何结构误差、振动误差、探测器误差(非线性误差和量化误差)、光源误差(波长不稳定和强度不稳定)、空气扰动和折射率变化误差。通过对这些误差理论分析和模拟,量化了各误差对测量精度的影响,其中移相误差、几何误差、振动误差和空气折射率误差影响最为显著。根据测量精度要求和仿真结果,得到实现纳米级测量的干涉仪系统参数和环境参数设置要求。     

用于纳米测量的集成化单频激光干涉仪

研究了一种基于偏振光的集成式单频激光干涉仪。利用偏振光学变换方法,实现了干涉仪的光学4细分结构,提高了测量灵敏度;构建4路正交探测结构,实现了干涉仪的无源偏振调制,扩大了干涉仪测量范围;采用光路集成化的设计方法,实现了一体化干涉仪光路集成。对激光干涉仪进行振动测量实验研究,结果表明,静态位移测量误差小于±0.3 nm,振动测量的分辨率达10 pm/Hz1/2;上述集成单频激光干涉仪具有测量精度高、稳定性好、动态范围宽、受环境影响小等优点,可被广泛用于纳米测量的各个领域。     

单频长基线激光干涉仪的在线稳定性监测方法

研究了一种长基线激光干涉仪的在线稳定性监测技术,可用于纳米量级的位移和振动测量。构建了一个臂长22m的激光干涉仪用于位移和振动测量。基于相位生成载波(PGC)解调技术,通过在相位调制载波中增加已知频率、固定幅值的指示信号,利用指示信号的幅度变化,实现激光干涉仪的工作状态监测,以及测量环境的变化与波动的指示。实验结果表明,加入已知幅度频率的指示信号可以实现激光干涉仪在线运行状态的监测。该方法的优点是没有增加硬件负载,可实现激光干涉仪的在线稳定性监测,简化了干涉仪调试过程,提高了运行效率。     

1阶反馈稳定光纤3×3耦合器干涉测量系统

为了消除环境干扰对光纤干涉测量系统的影响,采用光纤3×3耦合器和光纤光栅构成光路复合在一起的两个光纤迈克尔逊干涉仪构成了光纤干涉测量系统.利用光纤光栅作为反射镜,两个光纤迈克尔逊干涉仪共有几乎相同的光路.其中一个光纤迈克尔逊干涉仪通过一个1阶反馈来补偿环境干扰的影响,实现对该测量系统的稳定;另一个光纤迈克尔逊干涉仪用于完成测量工作.结果表明,1阶反馈可以对0Hz～21Hz的干扰进行补偿,使得该测量系统适合于在线精密测量.     

激光合成波长纳米测量干涉仪的非线性误差分析

描述了激光合成波长纳米测量干涉仪的测量原理,分析了非线性误差对该干涉仪的影响,得出了由偏振光非正交、椭偏化和光学元件偏振非正交及椭偏化等对该干涉仪造成的非线性误差为偏振态误差的二阶或高阶小量。进行了激光合成波长纳米测量干涉仪和激光外差干涉仪的对比实验,结果表明激光合成波长纳米测量干涉仪的最大误差为2.1nm,优于激光外差干涉仪的最大误差7.5nm,验证了激光合成波长纳米测量干涉仪的优越性。     

标准型光学重循环的一个实验

理论分析表明,激光干涉仪的最小探测极限由信噪比为1时噪声水平所决定。一类为技术噪声,如电噪声、振动噪声等,由实验技术条件和水平所限制,可由技术水平的提高而克服;另一类为非技术噪声,如光量子噪声,它由光的统计特性所决定,是无法避免的。一般来说,激光干涉仪的极限探测灵敏度由光量子噪声所决定。 利用光压缩态技术是降低干涉仪量子噪声水平的一种途径。光学重循环(opticalrecycling)是提高干涉仪量子噪声限探测灵敏度的另一种途径。     

基于平面反射式全息光栅的激光自混合纳米位移测量研究

纳米位移测量技术是实现高精度纳米制造的基础。激光自混合干涉为精密纳米位移测量提供了一种结构简便、成本低廉,同时测量精度可达纳米量级的精密位移测量方法。区别于传统基于反射镜或散射面为反馈元件的激光自混合干涉测量方案,研究了一种基于平面反射式全息光栅的激光自混合纳米位移测量方法,该方法的位移测量结果以光栅的周期为基准。实验测得了在弱反馈强度条件下的光栅自混合干涉信号,通过阈值设定的方法确定位移方向的反转点,结合反余弦的相位解包裹算法处理光栅自混合信号,获得了对应的位移测量值。最终采用商用激光干涉仪与自组装的光栅自混合干涉仪进行位移测量数据的比对测量,实验结果表明,经过线性修正后,其位移误差不超过0.241%。     

1阶反馈稳定光纤3×3耦合器干涉测量系统

为了消除环境干扰对光纤干涉测量系统的影响,采用光纤3×3耦合器和光纤光栅构成光路复合在一起的两个光纤迈克尔逊干涉仪构成了光纤干涉测量系统。利用光纤光栅作为反射镜,两个光纤迈克尔逊干涉仪共有几乎相同的光路。其中一个光纤迈克尔逊干涉仪通过一个1阶反馈来补偿环境干扰的影响,实现对该测量系统的稳定;另一个光纤迈克尔逊干涉仪用于完成测量工作。结果表明,1阶反馈可以对0Hz～21Hz的干扰进行补偿,使得该测量系统适合于在线精密测量。     

面向空间引力波探测的低噪声平衡零拍探测系统研究（特邀）

空间引力波探测频段位于0.1 mHz~1 Hz范围内,在该频段内包含了更大特征质量和尺度的引力波波源信息。目前,基于不同尺寸及空间轨道的大型激光干涉空间引力波探测计划已经逐步实施,其中在干涉仪的激光光源系统中,需要抑制激光强度噪声及频率噪声等,光电探测作为激光噪声表征及抑制的第一级器件,其性能将直接影响激光噪声抑制效果。通过选定低噪声芯片、高稳定偏压系统的基础上,采用自减电路及跨阻放大电路进行整体电路设计;在电磁屏蔽、低温漂系数元件、低噪声供电以及主动温控等技术手段实现了高增益低噪声平衡零拍探测系统的研制;结合快速傅里叶变换法以及对数轴功率谱密度算法对其增益、带宽等性能进行评估测试,并进一步对激光的强度噪声在0.05 mHz~1 Hz频段进行探测表征。实验结果表明:所研发平衡零拍探测电子学噪声谱密度在1 mHz~1 Hz的频率范围内在3.6×10?5 V/Hz1/2以下,小于空间引力波探测对激光光源噪声要求;进一步当入射光功率为400 μW时,测量得到平衡零拍探测系统在0.1 mHz~1 Hz的频率范围内增益在20 dB以上;激光强度噪声谱密度在1 mHz处为3.6×10?2 V/Hz1/2,实现低噪声光电探测及激光强度噪声表征,为空间引力波探测中激光强度噪声表征及抑制等方面提供关键器件支撑。     

Semiconductor laser noise in an interferometer system

The noise of semiconductor laser light after passing a Michelson interferometer has been measured for gain guided as well as index guided double-heterostructure injection lasers. This noise is mainly due to the partition noise and the frequency noise of the laser emission. Unless the interferometer is perfectly balanced, the observed noise is several orders of magnitude larger than the usual intensity noise of semiconductor lasers.     

FM noise reduction and subkilohertz linewidth of an AlGaAs laser bynegative electrical feedback

Negative electrical feedback was applied to a CSP-type AlGaAs laser, reducing its FM noise at the Fourier frequency range of f⩽40 MHz. The magnitude of the FM noise was far lower than the quantum noise level of the free-running laser at 100 Hz⩽f ⩽4.4 MHz. It was as low as 1×10^-7~1×10 ^-6 that of the free-running laser at 100 Hz⩽f⩽1 kHz. The full width at half maximum of the field spectrum was reduced to 560 Hz. The major factors necessary for realizing the very low FM noise level were: (1) the laser had almost constant FM response characteristics for a wide Fourier frequency range; (2) a high-finesse Fabry-Perot interferometer was employed for highly-sensitive FM noise detection and to get higher feedback gain; (3) the reflection mode of the Fabry-Perot interferometer was employed to increase the bandwidth and efficiency of the FM noise detection; and (4) a computer simulation was utilized for optimum design of the feedback loop     

A fiber-optic interferometric seismometer

A fiber-optic interferometric sensor has been developed which consists of a seismic mass of 520 gm supported by two rubber mandrels, each wound with a single layer of single-mode optical fiber 6.5 m long. One end of each fiber is cleaved to enhance reflection. The other ends are interconnected via a fiber-to-fiber 3-dB coupler, forming a Michelson interferometer. When the case of the sensor is displaced, the fiber around one mandrel extends in length while the other contracts. The resulting "push-pull" mechanical operation of the sensor allows both legs of the interferometer to be active, providing good common mode rejection of spurious effects, as a reference leg is not required. This, together with the fact that the light traverses each leg of a Michelson interferometer twice due to reflection, provides the sensor with four times the sensitivity of a conventionally constructed interferometric sensor. Sensitivities of 8500 rad of optical phase shift per micrometer of case displacement have been measured above the mass-spring resonance, where the sensor operates as a seismometer. Below resonance the sensor operates as an accelerometer with a measured sensitivity of 10 500 rad/g, the highest reported to date. Including both thermodynamic and demodulator noise sources (approx 10 murad/sqrt{Hz}), below resonance the sensor has a detection threshold of 1 ng/sqrt{Hz}, a 20- dB improvement over the best existing conventional low noise vibration sensors.     

30 Hz-linewidth, diode-laser-pumped, Nd:GGG nonplanar ring oscillators by active frequency stabilisation

Reports a heterodyne linewidth of less than 30 Hz for the beatnote between the outputs of two 282 THz (1.062 mu m) Nd:GGG nonplanar ring oscillators (NPROs). The lasers were independently locked to adjacent axial modes of a high-finesse interferometer. The remnant frequency noise appears to be dominated by free spectra range fluctuations in the reference interferometer rather than by residual laser noise.<>     

Multiplexing of nonlinear fiber-optic interferometric sensors

The scheme is demonstrated with a three-sensor array consisting of magnetic-field, pressure, and displacement sensors exhibiting resolutions at 1 Hz of 20 μOe/√Hz (limited by ambient noise), 0.1 kPa/√Hz, and 30 nm/√Hz, respectively. Multiplexing is accomplished by dithering each transducer at a different frequency and using parallel phase-sensitive detectors (PSD) at the interferometer output to demultiplex the information. A single Mach-Zehnder interferometer driven by a single unmodulated laser was used. Factors affecting the performance of the multiplexing scheme, including interferometric demodulation technique, PSD performance, and nonlinear transduction mechanism, are discussed     

基于FBG选频的低噪声窄线宽单频光纤激光器

采用未泵浦掺铒光纤作为饱和吸收体压缩线宽,窄带高反光纤光栅作为波长选择器件,通过偏振控制器和偏振相关隔离器控制环形腔中行波的偏振态,利用反馈电路控制980 nm泵浦源的输入电流,以减小铒离子的弛豫振荡对光强波动带来的影响。研制的光纤激光器线宽小于8 kHz,相对强度噪声（RIN）10 kHz内小于-100dB/Hz,1 kHz处1 m程差干涉仪的相位噪声小于-120 dB/（Hz）^1/2,长时间监测无跳模现象,输出激光功率稳定。     

单频激光宽频段频率和强度噪声测量技术

报道了一种mHz至MHz宽频段激光噪声的规范测量技术。通过研制基于迈克耳孙光纤干涉仪的相关延时自外差频率噪声测量装置和具有定标功能的光外差拍频测量装置,结合频谱分析仪和快速傅里叶变换分析仪等标准仪器,规范地测量出了单频激光在mHz至MHz宽频段内的频率和强度噪声特性,并验证了测量结果的准确性。该测量技术有望应用于引力波探测和精密测量等应用中的激光噪声评估。     

基于光纤激光器的微振动信号保真拾取干涉仪

提出了一种新型的远距离微振动信号的测量和保真拾取系统.该系统基于迈克尔逊干涉仪结构,以窄线宽光纤激光器为光源,采用相位载波零差解调方案实现信号的还原.通过优化压电陶瓷堆(PZT)相位调制器驱动电路,有效地提升了系统的频率响应范围.通过引入移相电路提高了系统的信噪比.系统在50 Hz～4 kHz频率范围内线性度良好,输出信号的信噪比为60 dB,谐波抑制比为50 dB,系统的灵敏度为1×10-5rad/Hz1/2.     

Quantum phase noise and linewidth of a semiconductor laser

Quantum phase noise of a single longitudinal mode AlGaAs semiconductor laser is measured by converting it into intensity noise. A Michelson interferometer is used and a time delay is introduced. Results on spectral linewidth and noise spectrum are in good agreement with theoretical analyses based on a rate equation. Spectral linewidth of the semiconductor laser decreases from 100 MHz to 4 MHz in proportion to (I/Ith?1)?1 at the bias level of I/Ith=1.05 ? 1.4.