高功率高重频TEA CO2激光器激光放电腔技术

介绍了高功率、高重频TEA CO2激光器激光放电腔的放电电路、结构及特点,针对该系统的性能实施了合理的技术设想及研究方法。在分析高功率TEA激光器技术基础上,讨论了TEA CO2激光器激光放电腔的基本机理。该系统由多只具有储能充、放电功能的陶瓷电容,通过低阻抗匹配传输线、放电电极和紫外光预电离装置向激光器高能放电腔注入电能,获得高重复频率脉冲和高能量脉冲,经光学谐振腔窗口输出高功率激光。描述了储能充放电路、高压快脉冲、低阻抗匹配传输线、放电电极和紫外光预电离等技术的具体应用。     

3.39微米He-Ne激光器的输出特性和甲烷的吸收特性

在各种条件下，对3.39微米He-Ne激光器的输出功率的最佳放电和腔参数、小信号放大、输出功率对腔调谐的曲线以及CH4吸收进行了实验研究。输出功率和放电电流、压力、管直径、反射镜透射过率的关系用图表示。输出功率对腔调谐的曲线在压力低于1乇时出现拉姆凹陷，在腔内具有CH4吸收时出现反转拉姆凹陷。检验了反转拉姆凹陷的高度、宽度和剖面。测量了室温时CH4的吸收系数。     

四频差动激光陀螺腔长敏感性的研究

为了改善四频差动激光陀螺的性能,研究了腔长敏感性随温度和工作电流变化的规律。利用气体激光器模牵引效应的经典公式,推导了四频差动激光陀螺腔长敏感性的表达式。通过扫模实验研究了腔长敏感性与温度、放电电流的关系。实验结果表明:温度越高,腔长敏感性越小;放电电流越小,腔长敏感性越小。因此采取较小的放电电流可降低四频差动激光陀螺的腔长敏感性,降低稳频误差的影响。     

自持体放电的发射光谱研究

自持体放电又称大气压脉冲放电或脉冲辉光放电,是一种利用微秒-亚微秒量级脉冲在大气压下获得大体积等离子体的放电形式。为了测量自持体放电过程中气体温度的演化,采用光谱拟合的方法,对氮分子第二正带光谱进行了理论分析。并对两套横向激励大气压(TEA)气体激光器放电系统(准分子放电腔快放电系统,TEA CO2激光器放电腔慢放电系统)的等离子体时域分辨分子光谱进行了测量,并拟合了气体转动温度,取得了两种不同放电结构放电过程中气体温度演化的数据。结果表明,准分子放电腔快放电过程中总的能量注入密度为1.3105J/m3时,温度升高92K,TEA CO2激光器放电腔慢放电过程中总的能量注入密度为7104J/m3时,温度升高约50K,两套系统温度升高比对应于总的注入能量密度比。这一结果对研究自持体放电机理提高放电稳定性是有帮助的。     

MOPA结构准分子激光系统的同步控制

为了使主振荡功率放大结构的ArF准分子激光器实现双腔同步放电,采用同步逻辑快速响应双腔放电时序,根据同步控制逻辑自动对双腔延时进行精密调节,使用四位二进制计数器实现粗调搜索,快速缩小双腔延时差,而使用通用数字可编程延时芯片来实现小精度延时调节。结果表明,双腔放电同步调节之后,放电时差稳定在23ns左右,同步抖动小于±3ns,满足4kHz高重复频率下主振荡功率放大结构准分子激光器同步控制的要求。     

小型折叠腔自由振荡TEA CO2激光器实验研究

分析了TEA CO2激光器和差分吸收雷达的工作原理，研制了一种新型双通道放电激励折叠腔TEA CO2激光器。详细分析了折叠腔TEA CO2激光器的结构及其设计特点。对影响气体快放电过程的各种因素，如储能电容与峰值电容的比值、工作气压、充放电电感及输入电压的范围等进行了实验研究，确定了充放电谐振回路的最佳参数，实现了双通道的稳定辉光放电。对激光器输出能量与激励电压、混合气体工作气压等参数的关系进行了实验研究，得到最大输出能量约为722 mJ。     

印刷线路板加工工艺制作微腔等离子体阵列

采用印刷电路板工艺制作了微腔等离子体阵列,并测量了该阵列的放电特性.该器件采用标准的印刷线路板工艺制作而成,可以降低微腔等离子体器件制作的难度和提高阵列的一致性.实验结果表明,限流电阻为10kΩ情况时,直径100μm,间距150μm的微腔在一个大气压的氖气中放电电流最大值可达30mA.随着驱动电压的增加,放电电流的最大值不断升高而放电延时不断降低.     

一种适合于同轴放电气体激光器的多程环形腔

本文提出了一种适用于同轴放电气体激光器的环形腔方案,给出了这种腔的设计和光束特性。     

横流放电CO_2激光器能量转换的特性和机制

模拟计算分析了横流放电CO_2激光器中介质气压、流速、光腔位置、腔中辐射强度、输出耦合度等因素对介质各能态间能量转换特性的影响.     

稳定大功率单频输出He-Ne激光器的新进展

继文献[1～3]之后,为了提高输出功率,并消除放电毛细管不规则带来的腔损耗,作者研磨了放电毛细管的内壁,将输出功率进一步提高到24mW。此时激光器的主要结构参数为:腔长1140mm,放电管长1m,放电管内径2.48mm;采用平凹腔结构,凹面曲率半径为4m,     

Resonance characteristics of a cavity-operated electrodelesshigh-pressure microwave discharge system

To characterize the resonance behavior of cavity-operated electrodeless high-pressure microwave discharge systems, a microwave circuit is developed that allows high-power network analysis during the operation of the discharge. The frequency-dependent complex impedance of the cavity including the plasma is obtained from a reflection measurement in the range 1.5 GHz-4.5 GHz. This method allows an observation of the actual resonance frequency and the actual vectorial mismatch so that a coupling efficiency >99% can always be achieved with proper adjustment of the operation frequency and coupling probe. Experimental results with a cylindrical TM₀₁₀ cavity and a coaxially situated discharge show a decrease of the resonance frequency with increasing power (increasing plasma temperature, electron density, and electrical conductivity) depending on the discharge geometry and the plasma composition. In accordance with a simple one-dimensional model, the Q factor passes through a minimum at medium power levels, where the cavity discharge system absorbs the microwave energy most effectively     

Modeling of electromagnetic interference induced by electrostaticdischarge (ESD) inside resonant structures

This paper presents an accurate analysis of the effects produced by electrostatic discharge (ESD) inside a metallic enclosure, representing the metallic shield of an apparatus. The considered discharges are either directly generated inside the cavity or guided into the enclosure through a transmission line. The model, which makes use of a modal approach for the calculation of the electromagnetic (EM) field inside the cavity, evaluates the disturbance induced by the different kinds of ESDs on a victim line. The results both in the frequency and time domain have been validated by experimental measurements and highlight the effects of the resonant nature of the structure on the intensity and the duration of the disturbance     

贯通导线端接负载对腔体电磁耦合影响分析

为研究贯通导线端接负载对金属腔体电磁耦合的影响, 基于时域有限积分方法建立了平面波辐射条件下含贯通导线金属腔体的耦合计算模型, 通过腔内屏蔽效能变化研究了端接负载及连接方式等对腔内电磁耦合的影响, 分析了耦合机理, 提出了基于吉赫横电磁波传输室建立含贯通导线腔体电磁耦合实验的新方法, 对计算结果进行了实验验证.研究表明:腔内贯通导线负载为纯电阻及容性阻抗时, 负载接腔体或腔体接地能降低腔内的电磁耦合, 且电阻值及电容值大小对腔内耦合有显著影响; 电阻及加载电容后发现,负载开路且腔体不接地时, 腔体的低频电磁耦合效果基本不变, 负载短路且腔体接地时, 负载变化对腔内高频耦合影响不大.负载连接腔体对腔内电磁耦合的谐振频率有一定影响.       

A kind of magnetron cavity used in rubidium atomic frequency standards

Research on the magnetron cavity used in the rubidium atomic frequency standards is developed, through which the main characteristic parameters of the magnetron cavity are studied,mainly including the resonant frequency,quality factor and oscillation mode.The resonant frequency and quality factor of the magnetron cavity were calculated,and the test results of the resonant frequency agreed well with the calculation theory.The test results also show that the resonant frequency of the magnetron cavity can be attenuated to 6.835 GHz,which is the resonant frequency of the rubidium atoms,and the Q-factor can be attenuated to 500-1000.The oscillation mode is a typical TE₀₁₁ mode and is the correct mode needed for the rubidium atomic frequency standard.Therefore these derivative magnetron cavities meet the requirements of the rubidium atomic frequency standards well.     

Stress Controlled Silicon Nitride Thin Film Deposited by Plasma Enhanced Chemical Vapour Deposition

SiN, films are deposited on silicon wafers through plasma enhanced chemical vapor deposition （PECVD）. The relationship between the film stress and deposition factors is investigated. It is found that low stress films would be obtained by adjusting the ratio of low frequency（LF） power to high frequency（HF） power pulse time or the chamber pressure. The best of the two methods to control stress in the film is changing the percentage of LF power pulse time. The low stress condition is achieved when the percentage of low frequency power pulse time in total time（LF and HF pulse time） is close to 40%, The low stress cantilever of tunable vertical cavity surface emitting laser is obtained by using this deposition condition,     

Theory of the frequency comb output from a femtosecond fiber laser

The output of a femtosecond fiber laser will form a frequency comb that can be phase-locked through feedback to the cavity length and pump power. A perturbative theory is developed to describe this frequency comb output, in particular for a solitonic fiber laser. The effects of resonant dispersion, saturation of the self-amplitude modulation, cavity loss, third-order dispersion, Raman scattering, self-phase modulation, and self-steepening on the spacing and offset of the fiber-laser frequency comb are given. The mechanisms by which the pump power, cavity length and cavity loss control the frequency comb spacing and offset are identified. Transfer functions are derived for the comb response to change in cavity length, pump power or cavity loss. This theory can potentially be applied to other frequency comb sources as well.     

极低频垂直偶极子在地-电离层中场的数值积分算法

针对地-电离层空腔中极低频(ELF)场强问题,提出一种应用于任意复数角v的勒让德函数数值积分算法,并与已有渐近计算法、级数展开法进行比对,结果表明:该方法使用频率范围更广,计算精度、效率更高。利用此数值积分算法,计算了垂直偶极子激励的30Hz以下典型频点的场强分布,所得场强分布符合物理规律,无损耗条件下舒曼谐振频率与前人计算结果完全一致,印证了ELF垂直偶极子在地-电离层腔体中场的数值积分算法的正确性。     

Microwave electrothermal propulsion for space

The microwave electrothermal thruster (MET) is attractive for medium- or high-power spacecraft propulsion. A propellant gas is heated by passing it through a microwave plasma discharge created in a resonant cavity by tuning either the TM(011) or the TM(012) mode for impedance-matched operation. The MET is electrodeless, synergistically combines high pressure and high power capability, provides external control over the energy-conversion discharge, and operates on hydrogen propellant. Upwards of 95% efficiency has been reported. Calculations of potential MET performance are reported. Apparatus for testing the MET to power levels of 30 kW at 915 MHz is described. The low-ripple operation of the microwave generator has been verified, as has a procedure for starting the microwave discharge and raising the power applied to the cavity. Impedance-matched resonant operation of the microwave cavity has been achieved     

有限元方法计算介质腔谐振频率和品质因子

采用有限元方法计算了二维方形介质腔和二维微盘的谐振频率和品质因子,并给出了两种腔中磁场、电场振幅分布图,介质腔中的谐振问题对应亥姆霍兹波动方程的本征值问题,本征值的实部和虚部与谐振腔Q值关联;比较了近似解析解、FDTD解、FEM解的结果,对于谐振频率比较,FEM和解析解更接近,对于品质因子比较,低Q值结果FDTD和FEM结果相近,高Q值结果两者相差较大。通过比较知道,FEM方法比时域有限差分方法计算更准确,求解速度更快。