多外腔自混合干涉现象的理论与实验

考虑激光器外有多个反射体时所产生的自混合干涉现象，运用薄膜干涉理论，对弱光反馈条件下的多外腔自混合干涉理论进行了研究。基于复合腔激光器结构，建立了理论模型。理论分析构造了一个含有五个反射面的自混合干涉模型，模型是由三个外腔构成的多外腔自混合干涉。对模型进行了理论分析及数值仿真，得出在弱光反馈条件下，多外腔自混合干涉信号类似于传统的自混合干涉信号，为一类正弦波(外部反射率较小时)或类锯齿波(外部反射率较大时)。设计了实验系统，给出了实验结果并进行了验证。如果忽略多外腔的结构，理论所得结果与简单的三镜腔自混合干涉结构所得结果一致。     

基于时间门方法的随机耦合模型在复杂腔体电磁预测中的应用

利用随机耦合模型(random coupling model,RCM)预测复杂腔体电磁效应时,通常要通过测量辐射阻抗来实现,但实验过程中满足混沌腔体以及耦合通道的腔体加工、实验过程模拟等条件要求较高,且实验步骤繁琐.为了克服上述问题,文中采用时间门方法(time gating method,TGM),通过对散射参数进行...     

脉冲腔衰荡技术探测气溶胶消光系数的研究

为了高灵敏度地测量气溶胶消光系数,采用高反射率腔镜以及脉冲腔衰荡的方法,搭建了气溶胶消光系数检测装置。对不同条件下的实际大气进行了测量,对实验结果进行了分析和研究,并与国内外研究成果进行比较。结果表明,由实验装置测量的腔衰荡时间大于40s,稳定性优于0.3%,探测灵敏度大于1.810-7m-1。高反射率腔镜及脉冲腔衰荡方法在研制高灵敏度气溶胶消光系数检测装置中具有较强的可行性。     

Study on microwave excited by virtual cathode oscillation in cavity

Microwave excited by virtual cathode (VC) oscillation in a cylindrical cavity is analyzed. The VC is regarded as a oscillating charged disk. By the means of model expansion method, the relation between microwave frequency and VC oscillation in a specific cylindrical cavity is obtained. The expressions of mode expansion coefficients are derived. The results show that at longer cavity length, the microwave excited is more pure, this is in good agreement with experiment results. Analysis confirms that the closer is the characteristic freuency of a mode to the oscillating frequency of VC, the larger is the mode expansion coefficient.     

偏振态稳定型光纤激光器的仿真与实验

提出了一种以价格较为经济的非保偏掺铒光纤作为增益介质的新型结构的Sigma谐振腔光纤激光器.使用Jones矩阵对该光纤激光器的偏振特性进行了分析,并在不同温度条件下进行了实验的验证.实验表明Sigma腔光纤激光器能够提供偏振状态稳定的输出光,因而可应用于光网络测量系统和光纤传感等领域.     

Equivalent surface impedance of an infinite periodic array of slot impedance loads based on a semicylinder cavity

A problem of finding the equivalent surface impedance of an infinite periodic array of slot impedance loads based on a semicylinder cavity. The problem is solved by the integral-equation method. As the numerical method for solving the integral equation, the Krylov-Bogoliubov method is used. The results of the numerical experiment are presented in the form of dependences of the impedance on the cavity radius, slot width, conductor width, and angle of electromagnetic-wave incidence. The angular dependences of the impedance are compared to the earlier results obtained for an array of rectangular grooves and a single impedance load based on a semicylinder cavity.     

多面开孔腔体孔缝耦合效应研究

为研究任意入射角度平面波对多面开孔腔体的孔缝耦合效应,根据矢量分析和矩形波导内场强分布对等效传输线法进行了改进,计算了多面开孔腔体内任意位置的屏蔽效能。将改进等效传输线法计算结果与CST仿真结果、实验测量结果进行比较,验证了改进等效传输线法的正确性,相比数值计算方法,改进等效传输线法所需计算时间和内存更少。采用改进等效传输线法对相同体积不同尺寸的多面开孔腔体的屏蔽效能进行了研究,结果表明:在相同体积下,腔体为正方体时的屏蔽效能和其他尺寸腔体的屏蔽效能基本一致,但是正方形的屏蔽效能极小值点大大减少,从而减少了电子设备受电磁干扰的几率。     

新型回旋速调管放大器链式群聚腔的模拟与设计

对新型回旋速调管放大器的链式群聚腔—TE模簇腔进行研究，通过三维电磁模拟对其进行分析和计算，讨论了损耗介质对群聚腔Q值的影响，以及内外腔耦合孔数量对谐振特性的影响．模拟计算结果和冷测实验吻合得很好．最后，为正在研制中的Ka波段三次谐波倍增回旋速调管放大器设计了一种链式群聚腔。     

"He-Ne激光器的装调与参数测试"实验的改进

介绍了"He-Ne激光器的装调与参数测试"实验的改进。针对旧的实验系统中对固定腔长、固定腔镜曲率半径的内腔式激光器进行模式观察与测量的情况,提出了采用变化腔长、变化腔镜曲率半径的半内腔式激光器系统来调光及观察、测量纵模,使得学生在该实验项目上有较大的探索空间;也促进了学生对激光理论的进一步理解。     

双端面抽运Nd:YVO_4激光器的理论和实验研究

基于传输矩阵理论,针对双端面抽运的"Z"型折叠腔Nd∶YVO_4 激光器的谐振腔设计进行了数值模拟,着重分析和比较了不同腔型稳定性的变化情况."Z"型折叠腔中关于臂长的选择对于稳定性影响较大,平凹腔在较低的泵浦功率范围更加稳定,双凹腔的稳区范围较小,但是却更适合在高泵浦功率下工作.分别采用平-凹和双凹腔型对Nd∶YVO_4的1 064 nm连续激光进行了研究,在相同腔长不同腔型下分别获得了稳定的1 064 nm高功率激光输出,谐振腔稳区范围和输出功率变化规律与理论计算吻合.     

小孔矩形腔体屏蔽特性的研究

本文提出了有孔腔体远、近场电磁屏蔽效能的计算方法，体研究了矩形腔体的屏蔽特性，讨论了各类孔对屏蔽能的影响程度。数值结果表明，理论计算与实验数据吻合较好。     

AM mode-locking of a free-electron laser oscillator

The authors present experimental and theoretical studies of a mode-locked free-electron laser (FEL) oscillator. In the experiment the FEL uses a continuous electron beam and operates in the microwave regime. AM mode-locking is performed by modulating the attenuation of the FEL ring cavity by a PIN diode modulator. The modulation period is tuned to match the RF roundtrip time in the ring cavity. The experimental results show the evolution of a single radiation macropulse, consisting of narrow micropulses in synchrony with the sinusoidal locking signal. The micropulse period (~37 ns) equals the roundtrip time and the modulation period. The micropulse width (~5 ns) is limited by the FEL slippage time and by the dispersion in the waveguide ring cavity. The effect of the mode locking consisting in suppressing asynchronous oscillations is clearly observed in the experiment. A theoretical model of the AM mode-locked FEL oscillator operating in the small signal regime is presented. This model includes the slow time variation of the e-beam energy and waveguide dispersion. The theoretical analysis agrees well with the experimental results     

In-phase mode selection of 18-core photonic crystal fiber based on Talbot resonator

An effective mode selection is important for the multi-core photonic crystal fiber（PCF）to obtain good output.Talbot cavity is popular to lock the in-phase mode,but few satisfactory experimental results have been reported.In this paper,a dual-Talbot cavity with reflected mirrors on each side of PCF is designed to lock the in-phase mode.The design gains the advantage of in-phase mode against out-of-phase mode.What＇s more,it can weaken the influence brought by the imperfect end facet of the fiber.The corresponding theoretical analyses and the experiment are taken.The experimental results suggest that the dual-Talbot cavity improves the capacity of mode selection.     

毫米波高温超导介质谐振器

本文研究了毫米波介质谐振器的TE013模式,给出屏蔽腔对谐振频率的影响,提出一些设计上的考虑,并给出了谐振腔装置的实验结果。     

一种新的横模选择概念与方法

提出并研究了利用腔中中空波导管选择横模的新概念和方法。基于这种方法的复合腔激光器实现了在不施行压缩振荡模体积情况下获得单横模高功率密度输出。理论分析与实验结果表明了这种新技术的诱人的应用前景。     

被动调Q激光器输出波动因素的实验研究

对Cr：YAG被动调QNd：YAG激光器进行了实验研究。着重研究了抽运功率、腔长、输出镜透过率以及晶体问距等因素对于激光输出脉冲序列的重复率、脉冲宽度以及峰值功率不稳定性的影响。实验结果表明,抽运功率是影响输出稳定性的最大因素,增大抽运功率加剧输出的波动,增加腔长减小输出的波动;同时存在一个最佳的输出镜透过率,可以使输出脉冲序列最稳定。在此基础上,依据被动调Q的原理,对实验现象产生的原因做了理论分析。分析结果对被动调Q激光器的设计有一定的指导意义。     

被动调Q 激光器输出波动因素的实验研究

对Cr:YAG 被动调Q Nd:YAG 激光器进行了实验研究。着重研究了抽运功率、腔长、输出镜透过率以及晶体间距等因素对于激光输出脉冲序列的重复率、脉冲宽度以及峰值功率不稳定性的影响。实验结果表明, 抽运功率是影响输出稳定性的最大因素, 增大抽运功率加剧输出的波动, 增加腔长减小输出的波动; 同时存在一个最佳的输出镜透过率, 可以使输出脉冲序列最稳定。在此基础上, 依据被动调Q 的原理, 对实验现象产生的原因做了理论分析。分析结果对被动调Q 激光器的设计有一定的指导意义。     

边缘驱动双腔可变形透镜的设计及制备

针对基于边缘驱动的可变形透镜无法进行球差像差的问题,该文提出了一种边缘驱动双腔可变形透镜结构。上腔体压电圆环32个致动器,校正除球差外的其余低阶像差,主要包括离焦、像散及慧差的校正。下腔体压电圆环1个致动器,通过与上腔致动器的相互作用,实现球差的校正。搭建了可变形透镜性能测试平台并进行了实验。实验结果表明,该可变形透镜能重构前4阶Zernike像差。     

外腔反馈半导体激光器的损耗和阈值特性研究

通过对半导体激光器(LD)的损耗和阈值电流特性的分析，引入等效反射系数的概念，根据多光束干涉的原理，导出了在外腔反馈作用下LD的阈值电流公式。从等效反射系数的推导可以看出，外腔的反馈相当于增大了LD一个端面的反射率，减小了损耗，从而使LD激光振荡的阈值降低。该公式在外腔长度和激光波长可以比拟的情况下能够准确地分析反馈注入对阈值电流的影响，但是在外腔长度远大于激光波长情况下不再适用。针对实验中外腔长度较大的情况，使用光功率的分析简化了理论模型，得出了与实验结果相吻合的结论，即外腔反馈注入使LD出光阈值电流明显降低。     

Longitudinal mode-switching dynamics in a dual external-cavitylaser diode [optical neural network]

We study the potential speed of an optical neural network that uses the longitudinal cavity modes of an external-cavity laser diode as neurons. For this purpose, we used a laser diode coupled to two external cavities, each corresponding to one longitudinal cavity mode. The process of longitudinal mode switching is investigated for the case of intracavity optical modulation. In this experiment, the feedback for the mode in one cavity is modulated, and the length of the other cavity can be controlled. Three limitations are imposed on the switching speed. A number of external-cavity round trips are needed to switch from one mode to the other. It is observed that, depending on the amount of optical feedback in both cavities, between 7 and 21 round trips are needed. When the experimental results for varying cavity length are extrapolated to zero cavity length, a residual delay of a few nanoseconds remains. It is believed that this delay is due to a change in carrier density, needed to switch from one mode to another. Modified rate equations are used to model our experiments. The results of numerical simulations are in good agreement with the experimental results and predict the residual delay. The model also predicts a turn-on delay that is related to relaxation oscillations and imposes a third limitation on the operation speed of our optical neural network. Implications of our findings on the potential operation speed of the optical neural network are discussed and suggestions are made for optimization