基于激光自混合的微纳米振动测量关键技术研究

发布时间：2018-03-30 00:15

本文选题：激光自混合　切入点：小波分解　出处：《南京师范大学》2017年博士论文

【摘要】：激光自混合效应是指激光器既是光的发射器又是接收器,激光内腔受反射光影响改变激发射光功率、光谱和相位等特性的现象。自混合中激光器可被外腔光程和自身驱动条件(电流注入、电子束或光束泵浦)的变化输出特定的低频光波,携带被测物的位向信息,通过分析输出光特性可获知被测物理量。出射和反射光共享传播路径,系统紧凑易准直,且外腔中可置入声光晶体引入频移或电光晶体引入相移,配合相应解调技术测量精度获极大提升(可达1个纳米),因此自混合干涉技术可满足计量环境中嵌入式高精度的要求。本文应用激光器复合谐振腔模型分别阐释和验证了单模单外腔和双纵模双外腔两种情况下激光器的光振荡特性,在课题组前辈工作基础上研制了新型自混合干涉系统,并应用研制系统对一维/亚超声频率/二维微纳振动进行测量,实验结果与商用激光多普勒测速仪(Ploytec-5000)进行比较。本文的主要内容大致分成如下四个部分:搭建基于磷化铝镓铟(ALGaInP)半导体激光器的精简激光自混合测振系统,分析激光器在适度和弱反馈范围输出光的特征,发现了条纹倾斜因子和被测相位在频域分布位置不同。应用小波分解提取低频相位进行希尔伯特变换解相,实现微米级位移的自辨向重建。该系统仅包含带量子阱结构激光器,工作电流的阈值低,不使用衰减器直接对振动表面照射测量,对比多普勒测速仪(LaserDoppler Velocity meter,简写为LDV)结果发现改半导体激光自混合干涉对微米幅度的低频(400Hz)振动分辨率优于λ/12。实验进一步表明该系统允许的反馈系数范围广,小波分解对激光散斑和环境噪声有天然抑制性,配合防静电电缆线,具有一定的可嵌入性。接着研究了半弧相移自混合干涉测振仪,特定的半个弧度相移深度由铌酸锂电光晶体的相移效应引入,激光器输出光通过与正交相依因子乘积滤波的方式对被测相位降频提取。无傅氏变换的纯时域解调流程因计算效率高,在非接触性瞬态振动测量(分析时间小于0.2秒)中的误差为几个纳米,噪声来源和大小也做了分析。本章利用该系统对非匀速振动测量,恢复出阻尼、脉冲、小幅度简谐振动的振动曲线,精度较半导体激光自混合干涉测量系统提高一个数量级,有可能发展成为一种快速在线测振仪。搭建了高测量上限的共振型相移自混合系统,相移由12MHz射频驱动共振电光调制器实现。射频自混合光信号通过高速数据传输技术转化为可分析离散数值,进而对超声换能器的幅频特性进行了测量。实验发现掺有氧化镁的铌酸锂电光晶体在射频段的驱动电压低,具备良好的高速的单偏振态电光相移效应。铌酸锂电光晶体引入正弦共振相位调制使得微波激光自混合信号的谐波频差进一步加大,因此系统对混叠效应免疫力腔,在30kHz以上的亚超声波段振动测量中得到了优于40纳米的精度。同时该系统允许的测量距离可达1米,散斑噪声弱。接着研究了偏振复用型相位调制二维激光自混合干涉仪。为拓展自混合干涉测量的被测光路数量,本文设计了基于双纵模激光器和偏振复用技术的相位调制型干涉光路,产生无光学串扰的双目标(混合型)自混合系统。由于光源的正交偏振特性,自混合微波光呈现二维矢量特性,其理论模型由复合腔结合多模He-Ne激光器Lamb半经典理论推导得出。实验发现弱反馈条件下模式竞争和偏振跳变现象明显减弱,两个纵模光强信号反向,呈现为两个正弦曲线的叠加。因正弦相移偏振态异向且频率可控,因此自混合信号谐波分量无混叠,在对二维定位、双目标和双参数的测量具有分辨率可选的优点。两个测量光路可同时或单独工作,对微米级振动的测量精度均优于10个纳米。最后研究了光纤耦合型的波导相移半导体激光自混合测振系统。近红外波段850nm半导体激光器在保偏光纤中与相位调制器耦合,可弯曲光路具备抗电磁干扰的能力。得到自混合信号和光谱不依赖与光纤长度,虽然存在一定散斑噪声,但实验表明高斯激光束传播过程中易发散的问题得到了解决。
[Abstract]:The laser self mixing effect is that laser light is the transmitter and receivers, laser cavity by reflected light effect change of the excitation light power, spectrum and phase properties. The self mixing laser can be external cavity optical path and its driving conditions (current injection, electron beam or beam pump) the change of output light of specific frequency the carrying of the measured object orientation information, through the analysis of the output characteristics of light can be obtained. The measured physical quantity emitted and reflected light propagation path sharing system is compact, easy alignment, and the external cavity can be inserted into the shift or the introduction of acousto-optic crystal electro-optic crystal phase shift is introduced, with the measurement accuracy of the corresponding demodulation technique was greatly improved (up to 1 nm), thus self mixing interference technology can meet the requirements of high precision measurement in the embedded environment. The composite resonant cavity model using laser respectively explain and verify the single and double external cavity Optical oscillation characteristics of laser longitudinal mode double external cavity two cases, we developed a new type of self mixing interference system in the research group on the basis of the work of predecessors, and application development of measuring system for one-dimensional / two-dimensional ultrasonic frequency / sub micro vibration, experimental results and commercial laser Doppler velocimetry (Ploytec-5000) were compared. The main content this article is divided into four parts as follows: build the AlGaInP semiconductor laser (ALGaInP) based on the simplified laser self mixing vibration system, analysis of laser in the moderate and weak feedback characteristic range of output light, found the fringe inclination factor and the measured phase in the frequency distribution of different positions. The application of wavelet decomposition solution phase transformation of Hilbert extraction of low frequency phase, to achieve micron level displacement since the resolution to the reconstruction. The system contains only with quantum well lasers, the working current of low threshold, not the attenuator Directly on the vibrating surface radiation measurement, contrast Doppler velocimeter (LaserDoppler Velocity meter, abbreviated as LDV) the semiconductor laser self mixing interference amplitude of low-frequency vibration (400Hz) micron resolution better than lambda /12. experiments indicated that the system allows a wide range of feedback coefficient, wavelet decomposition of a natural inhibition of laser speckle and environmental noise, with anti-static cable, can be embedded. Then study the semi arc phase self mixing interference vibrometer, half a radian specific phase shift depth by LiNbO3 electro-optic crystal phase shift introduced laser with orthogonal product dependent factor filtering method of the measured phase frequency reduction extraction. Pure time domain demodulation process without Fourier transform due to high computation efficiency in non-contact vibration measurement (transient analysis time less than 0.2 seconds) in the error of a few nanometers, The noise source and size are also analyzed. This chapter uses the measurement system for non uniform vibration, restoring damping, pulse, vibration curve of small amplitude harmonic vibration, accuracy of semiconductor laser self mixing interference measurement system is improved by one order of magnitude, which is likely to become a fast online set up resonance type vibrometer. High measurement limit of phase shift from the hybrid system, the phase shift is realized by the 12MHz RF resonance modulator. The RF self mixing light signal through the high-speed data transmission technology into discrete numerical analysis, and the ultrasonic transducer and amplitude frequency characteristics were measured. The experimental results showed that doped LiNbO3 electro-optic crystal in the Magnesium Oxide radio frequency drive low voltage, good high-speed single polarization phase-shifting electro-optic effect. Lithium niobate electro-optic crystal by using the sine phase modulation makes the microwave resonance harmonic laser self mixing signal To further increase the frequency difference, so the system of aliasing effect immunity cavity, sub band ultrasonic vibration measurement in the 30kHz above are better than 40 nm. The precision of measuring distance up to 1 meters at the same time, the system allows, the speckle noise is weak. Then study the polarization multiplexing type two-dimensional phase modulated laser self mixing interferometer. Expand the self mixing interference measured by the optical quantity, this paper designed interferometer based on phase modulation of double longitudinal mode laser and polarization multiplexing technology based on dual target without optical crosstalk (hybrid) self mixing system. Since the orthogonal polarization of light source, self mixing microwave light showing two-dimensional vector characteristics, its theory by combining the model of composite cavity multimode He-Ne laser Lamb semi classical theory is derived. The experimental results showed that under the condition of weak feedback mode competition and polarization jump phenomenon is weakened, the two longitudinal mode light intensity signal reverse Present, as the superposition of two sine curve. For sinusoidal phase shift polarization and to different controllable frequency, so the self mixing signal harmonic component without aliasing in the two-dimensional positioning, the advantages of measuring dual target and double parameter resolution is optional. The two optical path at the same time or work alone, measurement accuracy the micron vibrations were better than the 10. At the end of the nano waveguide fiber coupling type phase shift of semiconductor laser self mixing vibration system. Near infrared 850nm semiconductor laser in polarization maintaining fiber coupling and phase modulator, flexible optical path has the ability of anti electromagnetic interference. The self mixing signal spectrum and do not rely on the fiber length, although there are some speckle noise, but experiments show that the divergence problem of Gauss laser beam propagation process has been solved.

【学位授予单位】：南京师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN24

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