Analysis of two stacked cylindrical dielectric resonators in a TE₁₀₂ microwave cavity for magnetic resonance spectroscopy

The frequency, field distributions and filling factors of a DR/TE??? probe, consisting of two cylindrical dielectric resonators (DR1 and DR2) in a rectangular TE??? cavity, are simulated and analyzed by finite element methods. The TE(+++) mode formed by the in-phase coupling of the TE??(δ)(DR1), TE??(δ)(DR2) and TE??? basic modes, is the most appropriate mode for X-band EPR experiments. The corresponding simulated B(+++) fields of the TE(+++) mode have significant amplitudes at DR1, DR2 and the cavity's iris resulting in efficient coupling between the DR/TE??? probe and the microwave bridge. At the experimental configuration, B(+++) in the vicinity of DR2 is much larger than that around DR1 indicating that DR1 mainly acts as a frequency tuner. In contrast to a simple microwave shield, the resonant cavity is an essential component of the probe that affects its frequency. The two dielectric resonators are always coupled and this is enhanced by the cavity. When DR1 and DR2 are close to the cavity walls, the TE(+++) frequency and B(+++) distribution are very similar to that of the empty TE??? cavity. When all the experimental details are taken into account, the agreement between the experimental and simulated TE(+++) frequencies is excellent. This confirms that the resonating mode of the spectrometer's DR/TE??? probe is the TE(+++) mode. Additional proof is obtained from B?(x), which is the calculated maximum x component of B(+++). It is predominantly due to DR2 and is approximately 4.4 G. The B?(x) maximum value of the DR/TE??? probe is found to be slightly larger than that for a single resonator in a cavity because DR1 further concentrates the cavity's magnetic field along its x axis. Even though DR1 slightly enhances the performance of the DR/TE??? probe its main benefit is to act as a frequency tuner. A waveguide iris can be used to over-couple the DR/TE??? probe and lower its Q to ≈150. Under these conditions, the probe has a short dead time and a large bandwidth. The DR/TE??? probe's calculated conversion factor is approximately three times that of a regular cavity making it a good candidate for pulsed EPR experiments.     

Atomic NOON state generation in distant cavities by virtual excitations

A general scheme of generating NOON states of virtually-excited 2N atoms is proposed. The two cavities are fibre-connected with N atoms in each cavity. Although we focus on the case of N = 2, the system can be extended to a few atoms with N 〉2. It is found that all 2N atoms can be entangled in the form of NOON states if the atoms in the first cavity are initially in the excited states and atoms in the second cavity are all in the ground states. The feasibility of the scheme is carefully discussed, it shows that the NOON state with a few atoms can be generated with good fidelity and the scheme is feasible in experiment.     

非链式化学HF（DF）激光器工作气体中电子分离的非稳定性和气体放电等离子体的自组织现象

报道了放电引发的非链式HF（DF）激光器中的激活介质由电子碰撞负离子分离引起的电离非稳定性。这种非稳性出现在电极空间分离、脉冲CO2激光加热的基于sF6的混合气体的大体积放电中。实验研究了自引发体放电过程中由激光加热引起的放电等离子体的自组织现象以及由此在放电间隙的大部分区域形成的准周期等离子体结构。重点分析了等离子体结构随气体温度和注入能量的变化,讨论了等离子体自组织对电子碰撞分离不稳定性所产生的影响,解释了混合气体中由于电子碰撞使负离子消失导致的单等离子体通道移动的产生机理。     

电子俘获材料的研究现状及在红外检测方面的应用

电子俘获材料在辐射剂量测定、光信息处理、光存储、红外光检测等许多技术领域具有广泛的应用。本文详细介绍了电子俘获材料的发光原理、材料种类、制备方法以及研究现状,并针对该材料在红外光检测方面的应用,提出了在室温下该材料存在红外光检测上限的观点。针对电子俘获材料存在性质不稳定及在制备过程中需用到硫化类材料易造成污染等问题,建议进一步改进材料制备方法。最后,文中指出玻璃陶瓷类电子俘获材料会有很好的发展前景,并对该种材料未来的发展前景进行了展望。     

不同气体环境下532nm激光诱导硅表面形貌的研究

研究了在不同气体环境下,利用532nmNd：YAG纳秒脉冲激光累积辐照单晶硅表面形成的微结构,结果表明,在其他条件相同,背景气体不同的情况下,背景气体对硅表面形貌的形成起着重要的作用。具体分析了真空、N2和SF6 3种环境气氛下形成的微结构,结果显示,在sF6中形成的锥形微结构的数密度比在N2和真空中的大,并且锥形具有更大的纵横比;在N2、真空和sF6中形成的微结构尺寸依次减小。sF6气氛下,激光辅助化学刻蚀的效率比在真空和N2气氛中的高。另外,辐照区域边缘有波纹微结构形成,分析认为,该微结构的形成是由表面张力波的冷却导致的。     

基于DSP的高功率TEACO2激光器控制系统的高精度数据采集

针对基于DSP的高功率TEA CO2激光器控制系统直接利用DSP F2812内置A/D转换器（ADC）进行模拟量采样时存在转换误差较大,且模拟量易受电磁干扰等问题,从硬件和软件两个角度提出了校正DSP2812内置ADC的方法。硬件上采用硬件模拟滤波和隔离等手段对输入的模拟量进行处理;软件校正则通过将两路给定的参考电压值送入DSPF2812内置A/D转换器的两个转换通道,计算出ADC的偏置误差和增益误差,以此误差对其它通道A/D转换器进行校正。最后,实验分析了参考电压和A/D采样时钟频率对A/D转换精度的影响。结果表明,提出的方法能有效地提高A/D转换器的精度,A/D转换误差达到±3 LSB,特别是在对腔压值精度要求很高的0～12 000 Pa区段,A/D转换精度达±1 LSB,可以保证TEA CO2激光器的可靠运行。     

基于GaSe和GaSe0.7S0.3单晶的单脉冲CO2激光倍频器

描述了使用电感储能发生器和半导体转换开关泵浦的工作波长为10.6μm的高效CO2激光器。给出了激光泵浦的非线性晶体GaSe和GaSe0.7S0.3的二次谐波振荡的实验数据和理论估算结果。结果显示,GaSe晶体在输入能量为180mJ时,最大能量转换效率为0.38%,倍频激光的峰值功率为8 kW。     

非链式脉冲DF激光器的关键技术（英文）

基于化学反应的非链式脉冲DF激光器是产生3.5～4.1μm波段的有效相干辐射光源,具有存储能量水平高等优点。这些优点使得该激光器倍受中红外领域激光研究者的重视。为了更好地提高非链式脉冲DF激光器的输出性能,研制高能量水平的DF激光器,本文详细介绍了自引发大体积放电技术、混合气体配比技术、循环冷却技术等DF激光器关键技术,重点介绍了自引发大体积放电技术。这几种技术将为研制高性能DF激光器提供理论指导。     

多光束激光远场干涉实验研究

设计了多组多孔径光阑,将激光扩束后通过自制的多孔径光阑,获得多光束相干激光光源.基于多光束干涉理论,通过改变不同的光阑,得到多组点状阵列分布的远场干涉图样,结果表明远场中心主瓣具有随着占空比减小能量降低、旁瓣增多的分布规律.实验结果表明,相干源呈正三角形分布时能量集中度较好.对高功率激光相干合成具有一定的参考意义.     

舰船光电对抗中烟幕遮蔽与激光引偏的配合作战研究

通过分析舰船光电对抗作战中烟幕干扰和激光引偏干扰的特点,提出了烟幕遮蔽和激光引偏在对抗半自主激光制导武器时配合使用的作战样式,分析了各种作战样式的使用条件、工作流程和配合要素,以及作战样式的优势与不足,指出了多种干扰手段配合作战是发挥光电对抗系统综合对抗效能的关键.