当前自注入锁定频梳理论研究在不同参数对于自启动效果的影响的探究尚不完善,用于解释锁定机理的工作点理论与数值仿真的结果差异较大且无法很好地解释部分实验现象.本文利用包含微腔背散射效应的LLE(Lugiato-Lefever Equation)方程,构建了自启动克尔微梳模型,使用基于分步傅里叶算法的数值仿真并结合各参数的物理内涵,探究了模型关键参数对于频梳自启动锁定态的影响;在此基础上,针对现有自注入锁定微腔频梳锁定理论不足的问题,从模型基本公式出发,修正了工作点锁定理论,提升了对自启动数值仿真中锁定态预测的准确性,提高了理论预测与数值仿真和实验结果的契合度.
Active optical clocks, a new class of optical atomic clocks, work through stimulated emission lasing, a unique mechanism that is distinct from laser absorption spectroscopy of conventional optical clocks. With coherent weak optical feedback from a Fabry-Perot resonator operating in the bad-cavity regime, active optical clocks sustain a lasing oscillation at an atomic transition frequency. They are used directly as quantum optical frequency standards with expected stability better by about two orders of magnitude than that of the best clocks. This review starts with a simplified account of historical developments and the limitations of critical techniques in optical atomic clocks. After an introduction of the basic mechanism underlying active optical clocks, we discuss the most recent experimental results for several configurations and experimental set-ups of active optical clocks. These include those based on a 2-level atomic beam and 3-level laser-cooled trapped-atom system, those based on a 4-level atom scheme, and the Faraday active optical clock. Moreover, following the successful lasing and preliminary results on a Faraday active optical frequency standard with Faraday atomic filter using thermal Cs cell, we describe an experimental scheme of a Faraday active optical clock with a Faraday atomic filter using magic-lattice-trapped Sr atoms at the 689-nm transition, and Faraday optical clocks operating in the good-cavity regime. We conclude with a comprehensive comparison of the different active optical clocks, prospects for active Faraday optical clocks, and potential applications of active optical clocks.
为解决法布里-珀罗(Fabry-Perot,F-P)干涉仪锁频方法响应速度、抗干扰能力、长期稳定性方面存在不足的问题,提出了F-P干涉仪差分锁频方案,将存在频差的双频激光耦合入F-P谐振腔,当激光频差足够小时,两光强信号曲线存在交叉,以两光强信号的差值作为被控量,在交叉点附近构建单调过零函数,作为闭环控制系统的反馈量,实现动态差分锁频控制.基于该方案,搭建了一套F-P干涉仪微位移测量装置并开展实验验证,结果表明该装置能够实现0～300 nm范围内的微位移测量,位移测量分辨力达到23 pm,验证了F-P干涉仪差分锁频方案的有效性,为推动微位移测量领域的发展提供了重要借鉴.
声学高温计存在探头温度耐受不够,测温稳定性较差,易受气流速度影响的问题.为了提高声学高温计的测温可靠性,本文提出在Virtual.Lab中建立相应的气流温度场和声传播模型,改变现有的一套声学高温计的声探头分布直径、朝向和倾斜角度等拓扑结构,分析并研究减小声压级衰减的最佳拓扑结构参数,并进行试验对比.最终发现在常温至900℃、0～0.3 Ma的气流温度场环境中,直径15 cm,声探头与水平面倾角为30°的拓扑结构综合声压级减小数值最小;直径20 cm,声探头与水平面倾角为15°的拓扑结构次之.二者均比现有的拓扑结构数据标准差减小17%以上,提高了声源信号接收的性能,进而提高声学高温计在常温至900℃、0～0.3 Ma的气流温度场环境中测温的可靠性.
针对某型单轴摆式加速度计在使用过程中出现的电压输出异常典型故障问题进行理论分析,利用故障树综合性分析方法,层层追踪分析,表达出输出电压出现异常故障内在联系,直观指出单元故障与整体故障之间的逻辑关系,切实归纳总结了工程运用中实际遇到的单轴摆式加速度计输出电压异常故障问题.而后对故障原因进行精确细致定位,提出振荡器电路中的D4二极管正极金丝断裂为此型号加速度计故障根本原因,融入电路金丝断裂机理分析法,并通过试验测试与改进措施方式验证了此故障分析的准确性,一定程度上提升了加速度计可靠性.研究成果可以为加速度计可靠性使用提供一定参考.
