高品质光学微球腔谐振特性及鉴频特性分析

光学微球腔的回音壁模式使其存储能量大,从而获得高的品质因数。该文介绍了微球腔的制备方法;介绍了微球腔与锥形光纤的耦合理论,并对其耦合特性作出了分析;搭建了微球腔谐振谱探测系统并分析了不同耦合模式下的谐振特性;设计了微球腔谐振频率跟踪与锁定系统。通过仿真得到了不同调制频率下的鉴频曲线,分析了其吸收谱线与色散谱线特性。实验制得微球腔直径为440μm,耦合状态下的品质因数可达1.08×108;调制频率对鉴频曲线特性影响很大,低频调制下,优化调制后,可提升跟踪锁定效果,为后续的实验奠定了良好的基础。     

微球腔谐振频率的锁定及频移测量实验

对微球腔耳语回廊模式下的谐振特性所表现出的光学非线性进行了分析,对直径1 mm的SiO2微球腔的谐振谱线和解调曲线进行了仿真;搭建了微球腔耦合测试系统,得到了微球腔半高全宽值为78.42 MHz、Q值为2.5106的谐振谱线;基于正弦波相位调制技术对谐振谱线进行了同步解调,以减小相位复位脉冲噪声的影响;采用环路锁频技术实现了谐振频率的跟踪和锁定,对锁定精度和锁定时间进行了分析,实验结果为锁定透射谱强度至1%的时间为8 ms,锁定后可测频移分辨率为375 kHz,为微球腔的传感测量提供了实验依据。     

T型反馈网络在谐振式光纤陀螺频率锁定中的应用

谐振式光纤陀螺（R-FOG）的频率锁定是陀螺信号检测的关键技术,尤其在长时间的测试中,谐振频率的锁定稳定度决定了陀螺的输出性能。根据光纤环形谐振腔的传输理论,分析了其谐振特性及其一次谐波特性;搭建了R-FOG测试系统,采用正弦波相位调制解调技术实现谐振谱线一次谐波的输出;在分析由运算放大器构成的传统模拟比例积分（PI）电路的漂移误差源的基础上,给出了可以有效抑制漂移误差的T型反馈网络,应用到谐振式光纤陀螺的谐振频率锁定中,得到了较好的锁定效果,经Allan方差分析,谐振频率长时间（4000s）的锁定稳定度优于910-12。     

谐振式光纤陀螺数字闭环系统锁频技术

谐振式光纤陀螺(R-FOG)是基于Sagnac效应产生的谐振频率差来测量旋转角速率的一种新型光学传感器。利用数字调制、解调技术实现陀螺系统的闭环锁定,可以克服模拟电路的热漂移,使系统更加简单灵活。以谐振频率偏差作为研究对象,提出了基于一阶惯性环节的最简闭环锁定分析模型。利用该简化模型,对数字闭环系统中的频率反馈跟踪技术进行了研究,得到了在一定积分时间常数下环路的最佳增益系数,实现了环路的快速、稳定锁定,并在实验中得到进一步的验证。     

调相谱检测技术下光纤环腔的谐振特性

调相谱检测技术是谐振式光学陀螺信号检测的重要手段。根据贝塞尔函数展开与光场叠加原理,理论分析了光纤环形谐振腔的传输特性;搭建了谐振特性测试系统,采用LiNbO3相位调制,针对不同调制频率与调制电压条件下光纤环的谐振特性和解调曲线特性开展了实验,对实验结果进行分析,得到了调制频率、调制电压与光纤环形谐振腔谐振信号及解调信号之间的关系,实验结果与理论分析相符;并对调制过程中出现的谷裂现象进行了测试与分析,通过实验数据拟合,得到了产生谷裂现象的临界调制频率与调制电压值之间的关系。     

光学微腔相位调制解调技术分析及实现

理论分析了相位调制的原理及锁相放大器的解调原理。利用多光束干涉原理对微腔的谐振特性进行了分析并对其及环形谐振腔进行了相位调制解调仿真分析。设计搭建了基于光学谐振腔的相位调制解调系统。基于搭建的光学谐振腔的相位调制解调系统利用正弦波对微腔进行了调制解调测试, 得到了良好的测试结果并使用光纤环形谐振腔验证了调制解调系统及调制方法的可行性, 得到了光纤谐振腔的低频调制解调信号及边带调制解调信号, 为进一步研究光学谐振腔谐振点的跟踪锁定奠定了基础。     

光学微腔相位调制解调技术分析及实现

理论分析了相位调制的原理及锁相放大器的解调原理。利用多光束干涉原理对微腔的谐振特性进行了分析并对其及环形谐振腔进行了相位调制解调仿真分析。设计搭建了基于光学谐振腔的相位调制解调系统。基于搭建的光学谐振腔的相位调制解调系统利用正弦波对微腔进行了调制解调测试,得到了良好的测试结果并使用光纤环形谐振腔验证了调制解调系统及调制方法的可行性,得到了光纤谐振腔的低频调制解调信号及边带调制解调信号,为进一步研究光学谐振腔谐振点的跟踪锁定奠定了基础。     

谐振式光学陀螺锁频偏差的消除方法研究

谐振式光学陀螺系统需要使用激光器跟踪锁定谐振频率进行角速度检测,但其所用的半导体激光器存在光功率波动问题,受到相位调制器残余强度调制的影响,会使系统的解调曲线中心点发生偏移,导致陀螺系统出现锁定偏差,输出路形成长期漂移,该文对此进行了仿真分析与实验测试,并通过标定光功率与解调曲线中心点的方式得到两者线性关系,实时检测光功率补偿陀螺系统锁频点,消除光功率波动引起的陀螺输出误差,在本方案下陀螺系统的零偏稳定性测试为80 (°)/h,且输出路无漂移现象,能够提升陀螺系统的长期工作稳定性。     

闭环方波调制谐振型光纤陀螺标度因子非线性分析

对采用方波频率调制的谐振型光纤陀螺(R-FOG)的闭环控制方案进行了分析.当光波频率偏离谐振中心频率时,R-FOG反射光强将出现方波强度调制信号,利用此误差信号可以实现R-FOG的闭环控制,将CW和CCW两束光的光波频率分别锁定为其谐振频率.两束光的闭环频率锁定分别通过激光器频率调节和频率偏置调制实现,锁定精度由控制系统的精度决定.对基于方波调制的闭环R-FOG的标度因子非线性进行了分析.分析表明,标度因子非线性受闭环频率控制精度的影响,影响的大小与谐振腔的谐振精细度相关.谐振精细度越高,频率控制精度的影响越大.对于50精细度的谐振腔,100 ppm的标度因子非线性要求频率控制精度优于1 113 Hz,而对于100精细度的谐振腔,对频率控制精度的要求提高为605 Hz.     

压电式微固体模态陀螺谐振频率自动跟踪电路

压电式微固体模态陀螺振子通过交变电压激振、传感电极感应出电荷。当激励电压频率为某阶振动模态谐振频率时,感应电荷达到最大值。设计了谐振频率自动跟踪电路,使陀螺稳定工作在谐振模态。使用现场可编程门阵列(FPGA)控制直接数字频率合成器(DDS)产生频率精确可调的激励电压,驱动陀螺振子振动。检测谐振点对应的激励电压和感应信号间的相位差,作为反馈信号调节激励电压频率。实验结果表明,当相位差锁定区域处在98.48°~100.27°时,振子感应电极输出信号最大,振子处于谐振状态,实现了振子谐振频率的跟踪锁定。该系统可用于以谐振器为核心器件的振子工作模态锁定与跟踪。     

F-P腔锁频压窄窄线宽激光器输出波长精度测试

基于谐振式光纤陀螺系统要求窄线宽、高稳定性激光输出以满足谐振信号频差检测要求,设计了两种不同光路锁频系统并搭建了测试平台,利用波长计实时监控窄线宽激光器锁频前后两种状态下波长的变化情况。对方案二设置两种不同的仪器锁频参数,分别对激光器输出波长的锁频精度进行监控分析,得到不同设置参数可导致锁频精度降低1倍。两种方案测试结果均为锁频后的激光波长变化幅度仅为锁频前的0.2倍,且曲线频率变化光滑平缓,很大程度地压窄了窄线宽激光器输出波长变化幅度,波长变化稳定性得到了很大改善,提高了锁定信息反馈的实时性。进一步实施窄线宽激光谱线的压窄以及PI电路对窄线宽激光频率的有效快速跟踪锁定提供技术支撑。     

Measurement of Bandwidth of Microwave Resonator by Phase Shift of Signal Modulation

Bandwidth is measured by transmission of a signal with sine-wave modulation through a microwave resonator under test. The modulation frequency is adjusted so that the envelope is delayed 45/spl deg/ with respect to the input, indicating that the two sideband frequencies are separated by the half-power bandwidth. The resonance ratio (Q) is then equal to the ratio of carrier frequency over twice the modulation frequency. This depends on observations of these frequencies and the modulation phase shift, but not on the amplitude. It is insensitive to detuning or incidental frequency variation of the resonator or the signal. In a resonant cavity tested, an observed bandwidth of 30 kc at 700 mc indicated that Q =23,300.     

Terahertz operation of quantum-well intersubband hot-electronphototransistors

A novel infrared photodetector utilizing intersubband electron transitions and plasma wave excitation in a quantum well (QW)-the QW intersubband hot-electron phototransistor (IHEPT)-is proposed and evaluated. It is shown that the excitation of standing plasma waves in the QW base by incident modulated infrared radiation can result in resonant response of IHEPTs. The plasma resonance peaks of the linear responsivity of IHEPTs with a base contact spacing of about 1 μm correspond to the terahertz range of modulation (signal) frequencies. The resonant peaks of the responsivity can be tuned by the biasing voltage. The peak value of the IHEPT resonant responsivity can be of the order of the steady-state responsivity of standard QW intersubband infrared photodetectors, significantly exceeding the high-frequency performance of the latter. Relatively large values of the IHEPT resonant responsivity are associated with strong injected current stimulated by the plasma waves in the QW-base. Finally, it is shown that the nonlinear dependence of the injected current on the potential of the QW base results in the variation of the dc current with changing signal amplitude. The nonlinear response current as a function of the modulation frequency also exhibits resonant behavior with the peaks at the plasma resonance frequencies and can be used for the detection of the signal component envelope     

Phase-sensitive interrogation of fiber Bragg grating resonators for sensing applications

This paper discusses a phase-sensitive technique for remote interrogation of passive Bragg grating Fabry-Pe/spl acute/rot resonators. It is based on Pound-Drever-Hall (PDH) laser frequency locking, using radio-frequency phase modulation sidebands to derive an error signal from the complex optical response, near resonance, of a Fabry-Pe/spl acute/rot interferometer. We examine how modulation frequency and resonance bandwidth affect this error signal. Experimental results are presented that demonstrate, when the laser is locked, this method detects differential phase shifts in the optical carrier relative to its sidebands, due to minute fiber optical path displacements.     

A Microwave Frequency Standard Employing Optically Pumped Sodium Vapor

An instrument in which a simple microwave triode oscillator is stabilized by reference to a natural atomic resonance---the field-independent hyperfine resonance of sodium---is described. Light from a sodium lamp is transmitted through an absorption cell containing sodium vapor and argon, which is placed in a resonant cavity. This light produces population differences between the two quantum levels which are involved in the desired atomic resonance and provides a means of detecting resonance, The cavity is excited by an external microwave triode oscillator which is frequency modulated to a small degree at 60 cycles. When the exciting oscillator frequency coincides with the center of the atomic resonance line, the signal observed by a photocell will be a modulation of the transmitted light at 120 cycles and higher even-order harmonics. Any deviation from line center will introduce a 60-cycle component whose phase and magnitude may be detected to produce an error signal to retune the oscillator in the usual servo loop manner. Theory predicts that an accuracy of possibly one part in 10/sup 10/ can be achieved by systems using sodium and suitable local oscillators. It is evident also that such systems can be engineered into quite small packages, making possible many new applications of microwave oscillators stabilized to high order.     

一种纵向共振光声池谐振频率测量方法

为了快速准确测量共振光声池的谐振频率，采用基于共振声谱的光声池谐振频率测量法，搭建了光声光谱检测系统和共振声谱检测系统。对影响测量准确性的因素进行了实验分析。在不同气体体积分数的情况下，分别采用共振声谱法和光声信号强度标定法测量光声池的谐振频率。结果表明，共振声谱法测量的光声池共振频率与声信号激励电压、声源传播距离及角度无关；在5种不同体积分数的乙炔气体条件下，所测得的光声池谐振频率与通过光声信号强度法的结果最大偏差为1.1Hz，可认为两种方法测量结果具有一致性。该方法简单快速、可靠和准确，可用于确定光声池谐振频率。