衰荡腔测量中的腔参数选择

 基于谐振腔失调灵敏度参量随腔长的变化关系,提出了一种衰荡腔,它是由共焦腔将腔长缩短为原来的0.73得到的稳定腔。根据光束传输规律和失调腔矩阵方法,以及光腔衰荡法测量原理和曲线拟合方法,建立了腔长、腔镜角度失调下光腔衰荡法的反射率测量模型。通过数值模拟,研究了这种稳定衰荡腔中,腔微小失调对反射率测量结果的影响,并与相同失调情况下共焦衰荡腔的测量结果进行了对比分析。结果表明,这种稳定腔用作衰荡腔,测量结果受腔镜角度失调影响较大,而受腔长失调影响小;其长度较短,便于工程应用;衍射损耗较小,测量精度高。     

三维曲面腔顶盖驱动流的MRT-LBM研究

采用多松弛时间格子玻尔兹曼方法(MRT-LBM)的D3Q15模型分别对长方体腔、圆柱腔、半圆柱腔、旋转双曲面腔、旋转椭球面腔、半球腔以及两种组合腔体的三维顶盖驱动腔流进行数值模拟, 比较分析各腔体内流线分布、流速等值线分布和涡心的发展, 对于典型腔体模拟不同雷诺数下的流动情况。结果表明: 在同一雷诺数下, 曲面边界不仅能消除从边界产生的次涡, 还会导致腔内主涡的分离, 增大中心纵剖面纵向回流速度; “上长方体+下半圆柱”腔内流函数分布与边界贴合度最高。当雷诺数不断增大时, 半圆柱腔内主涡逐渐分离成两个同向涡, “上圆柱+下半球”腔内始终保持着圆柱腔与半球腔内的基本流动特征; 而长方体腔内主涡涡心保持在同一高度, 次涡逐渐增强, “上长方体+下半圆柱”腔内流动愈加规则, 主涡逐渐下沉, 流速等值线分布逐渐趋于中心小、四周大。     

Design of a higher harmonic cavity for the SSRF storage ring

Higher harmonic cavity used in the third generation synchrotron light source increases the Touschek lifetime.The higher harmonic cavity of Shanghai Synchrotron Radiation Facility(SSRF)is a 1.5 GHz passive superconducting cavity.Its higher order modes(HOM)are extracted by a ferrite HOM damper out of the cryostat.Multi-cell cavity is chosen concerning the voltage.The harmonic cavity dynamics,beam dynamics with passive harmonic cavity and the design of single cell cavity are included in this paper.     

一种220 GHz分布作用速调管的高频系统模拟

对一种基于双排矩形波导慢波结构(SDRWS) 结构的3腔EIK进行了详细计算机模拟计算, 通过对基于SDRWS结构的EIK用输入输出腔的S11的模拟计算及对分布作用速调管用中间腔的本征频率的模拟计算, 初步确定了EIK用输入输出腔及中间腔的结构参数, 进而对EIK进行了PIC互作用模拟计算, 结果表明: 该EIK的3dB工作频带为219.5~220.5GHz, 3dB带宽为1GHz, 最大功率为456 W, 最大增益为40.06dB。在此基础上, 通过调整中间腔的波导头宽度以进行参差调谐, 用PIC互作用模型模拟计算研究了中间腔谐振频率对EIK整体性能的影响。结果表明, EIK的3dB工作频带主要由输入输出腔的通频带决定, 而中间腔的谐振频率也具有重要影响。当中间腔的谐振频率分别处于输入输出腔的通频带的低频端或高频端时, 可以使EIK的3dB工作频带向低频端或高频端得到一定程度展宽; 当中间腔的谐振频率高于输入输出腔的通频带的高频端时, EIK的增益在其3dB工作频带内较为平坦, EIK的输出信号在其3dB工作频带内比较稳定, 频谱的纯净程度较好。参差调谐的最终结果表明, 当中间腔的波导头宽度为0.747mm时, EIK获得了接近最优的性能, 3dB工作频带为219.5~220.0GHz, 3dB带宽扩展到1.2GHz, 最大功率为630W, 相应的最大电子效率为11.3%, 最大增益为47dB。     

Acoustic transmission analysis on cavity resonance sound in a cylindrical cavity system: application to a Korean bell

This paper presents an analytical model for acoustic transmission characteristics of a cylindrical cavity system representing the acoustic resonance conditions of a Korean bell. The cylindrical cavity system consists of an internal cavity, a gap, an auxiliary cavity, and a rigid base. Since the internal cavity is connected to the external field through a gap, determination of the acoustic transmission characteristics becomes a coupling problem between the internal cavity and external field. The acoustic field of the internal cavity is considered by expanding the solution method of the mixed boundary problem, and the external field is addressed by modifying the radiation impedance model of a finite cylinder. The analytical model is validated by comparison with both experiment and a boundary element method. Using the analytical model, the resonance conditions are determined to maximize the resonance effect. Thus, the resonance frequencies of the bell cavity system are investigated according to the gap size and auxiliary cavity depth. By adjusting gap size or auxiliary cavity depth, the cavity resonance frequency is tuned to resonate partial tones of the bell sound. Finally, the optimal combination of gap size and auxiliary cavity depth is determined.     

Design of a higher harmonic cavity for the SSRF storage ring

Higher harmonic cavity used in the third generation synchrotron light source increases the Touschek lifetime. The higher harmonic cavity of Shanghai Synchrotron Radiation Facility (SSRF) is a 1.5GHz passive superconducting cavity. Its higher order modes (HOM) are extracted by a ferrite HOM damper out of the cryostat. Multi-cell cavity is chosen concerning the voltage. The harmonic cavity dynamics, beam dynamics with passive harmonic cavity and the design of single cell cavity are included in this paper.     

Fano interference and transparency in a waveguide-nanocavity hybrid system with an auxiliary cavity

We investigate theoretically single photon transport in one-dimensional waveguide coupled to a pair of cavities, which are denoted by the first cavity and the auxiliary cavity. Two cases with no atom and one atom embedded in the first cavity are discussed. The Fano dips in the transmission spectrum and locations of transparency window are calculated. When no atom is embedded in the first cavity, there exists a transparency window under the condition that the first cavity and the auxiliary cavity are not resonant. The locations of the transparency window and Fano line type depend strongly on the eigen frequency of the auxiliary cavity and the coupling strength between the auxiliary cavity and the waveguide. When one atom is embedded in the first cavity, we show that the transparency window exists even though the first cavity, the atom and the auxiliary cavity are resonant. The Fano line type is strongly dependent on the eigen frequency of the auxiliary cavity and the coupling strength. Our results have potential applications in design of quantum devices at the level of single photon,such as single photon switch and single photon routers.     

任意时间分布电子束与单间隙微波腔的非线性自洽过程研究

将电子束作为激励源，根据Maxwell方程和电子受到的洛伦兹力，给出了描述工作模式在电 子束作用下的激励方程和电子束电子在工作模式作用下的运动方程（即微波谐振腔中电子束 与微波场相互作用的自洽方程组）.根据该自洽方程组，进一步研究了任意时间分布电子束 与单间隙微波腔的相互作用.通过分析微波腔中电子束与微波作用的线性和非线性过程，给 出了电子束调制深度、微波腔作用间隙对微波输出功率的影响.最后从理论上给出了影响微 波输出功率的综合物理参量. 关键词： 微波腔 模式 自洽方程 单间隙微波腔     

STF数字微波低电平系统研究

STF是KEK为国际直线对撞机(ILC)建立的试验装置. 在STF中, 数字微波低电平系统用于控制超导腔的RF相位和幅度. 在没有实际腔运行的情况下, 设计了一个基于FPGA技术的实时超导腔模拟器, 用于测试微波低电平系统的硬件和算法. 超导腔的数字控制器用FPGA实现, 其中采用了PI反馈控制和前馈控制算法. 测试表明, 超导腔模拟器和控制器都工作良好, 可用于STF微波低电平系统的进一步开发.     

对光纤布拉格光栅法布里-珀罗腔纵模间隔问题的研究

对光纤布拉格光栅(FBG)法布里-珀罗(F-P)腔的透射特性进行了深入分析,指出了FBG F-P腔透射谱中纵模位置的影响因素,讨论了与普通F-P腔的联系和区别.应用光栅的有效镜面模型对FBG反射主瓣内反射系数的相位因子进行线性模拟,定义了FBG有效长度的概念并得出其表达式.提出将FBG的有效长度纳入到FBG F-P腔的等效腔长中,用等效腔长来计算FBG F-P腔中的纵模间隔.数值仿真和实验结果都表明,用等效腔长计算所得的纵模间隔与实际的FBG F-P腔中的纵模间隔符合很好,误差极小. 关键词： 光纤布拉格光栅 法布里-珀罗腔 纵模间隔 有效镜面模型     

FP腔腔长的测量新方法

ＦＰ腔是ＷＤＭ光纤通信系统中用于波长控制和解调的关键器件。为了进行匹配系统的设计以及计算已制成腔的自由谱区，准确测定腔长是必不可少的工作，但是由于ＦＰ腔的具体结构，测定腔长无法用直接的方法进行。本文通过谐振腔的谐振特性分析，推导出一种测量腔长的新方案。     

Implementation of Deutsch-Jozsa Algorithm with Superconducting Quantum-Interference Devices via Raman Transition

In this paper, a theoretical scheme is proposed to implement the Deutsch-Jozsa algorithm with SQUIDs (superconducting quantum-interference devices) in cavity via Raman transition. The scheme only requires a quantized cavity field and classical microwave pulses. In this scheme, no transfer of quantum information between the SQUIDs and the cavity is required, the cavity field is only virtually excited and thus the cavity decay is suppressed.     

Scheme for Implementation of Quantum Game in Cavity QED

We propose an experimentally feasible scheme to implement two-player quantum game in cavity quantum electrodynamics （QED）. During the process, the cavity is only virtually excited, thus our scheme is insensitive to the cavity field states and cavity decay. The scheme can be realized in the range of current cavity QED techniques.     

双光子过程耦合腔系统中光场的量子特性

本文研究了双光子过程原子与耦合腔相互作用系统中腔场的压缩效应和反聚束效应.考虑系统总激发数等于2的情况,利用数值计算方法讨论了腔场间的耦合强度变化和原子与腔场间耦合强度变化对反聚束效应的影响.研究结果表明:腔场不呈现出压缩效应;腔场的反聚束效应与原子与腔场的耦合系数之间,以及与腔场间的耦合系数之间都存在着非线性关系,     

基于宽度可调节的线缺陷平板型光子晶体的空气槽微腔

研究了一种空气槽光子晶体微腔,这种腔是由在平板型光子晶体上引入一条宽度可以调节的线缺陷空气槽形成的,腔模的电场被强烈局限在空气槽中,由于介电常量的不连续性,电场得到很大的提高,同时模体积被大大地降低.数值模拟与分析了微腔的能带结构和场分布,考虑到腔模的谐振频率和对称性,发现一阶偶膜同时具有较高的品质因子和较小的模体积;应用有限时域差分法,得到腔模的品质因子可以高达106,模体积仅为0.02(λ/n)3.计算了一阶偶模谐振波长随空气槽宽度以及空气孔半径的变化,发现随着宽度的增加,波长越来越短.而随着空气孔半径的增加,波长近似线性地减小;当空气孔半径为170 nm时,可以获得最高的腔品质因子.     

Optical feedback cavity ring-down technique for accurate measurement of ultra-high reflectivity

A novel cavity ring-down (CRD) technique, based on the optical feedback effect of Fabry–Perot diode lasers, is developed for accurate reflectivity measurement of highly reflective cavity mirrors. The strong optical feedback, including the direct reflection from the front cavity mirror of a linear ring-down cavity, is re-injected into the oscillator cavity of the diode laser, and large resonant peaks are observed in the ring-down cavity output signals. The diode laser is switched off by a threshold circuit when the amplitude of a resonant peak exceeds a pre-defined threshold. Exponentially decayed signals recorded immediately after switching off the laser are used to determine the cavity decay time. The ultra-high reflectivity of cavity mirrors is measured to be 99.99606% with a reproducibility of 0.00003%. Compared with the previous phase-shift CRD technique, the signal-to-noise ratio of the cavity output signals is improved with an enhancement factor of over 100.     

Intensity tuning characteristics of double-mode He--Ne laser with optical feedback

This paper investigates the intensity tuning characteristics of a double longitudinal modes He--Ne laser subjected to optical feedback. The intensity undulations of the total light and the two modes are observed for different external cavity length. Two modulations of the internal cavity length are performed. One is only for the internal cavity length being modulated and the other is for both the internal and the external cavity length being modulated. The undulation frequency of the total light is found to be determined by the ratio of external cavity length to internal cavity length in both modulations. When the external cavity length is integral times of the internal cavity length, the fringe frequency of the total light could be seven or even more times of that in conventional optical feedback. A simple theoretical analysis is presented, which is in good agreement with the experimental results. The potential use of the experimental results is also discussed.     

A scheme for implementing quantum game in cavity QED

In this paper, we propose a scheme for implementing quantum game (QG) in cavity quantum electrodynamics(QED). In the scheme, the cavity is only virtually excited and thus the proposal is insensitive to the cavity fields states and cavity decay. So our proposal can be experimentally realized in the range of current cavity QED techniques.     

双反馈半导体激光器的混沌特性研究

实验利用双反馈半导体激光器获得了关联维数为3.8的高维混沌光.同时对比分析了双反馈与单反馈两种不同模式产生混沌的区别.结果表明：在反馈强度均为-26 dB时,双反馈产生混沌的关联维数高于单反馈产生混沌的关联维数2.6;双反馈可获得带宽为11 GHz的混沌光,为单反馈产生混沌带宽5.5 GHz的两倍.当双反馈的两个外腔长度不相等时,混沌的自相关曲线能很好的隐藏外腔长度信息,可提高混沌通信的保密性. 关键词： 双反馈 半导体激光器 混沌 带宽     

耦合孔对微波腔的影响研究

从Maxwell方程出发,将微波腔中的实际微波场按其本征模式展开,进行微波腔的工作特性(如工作频率、场分布等)的研究.在具体处理过程中,根据复杂结构微波腔的具体边界,将微波腔分成规则形状微波腔和非规则(含耦合孔)部分,建立实际微波腔模式同规则形状微波腔模式之间的场耦合方程,从而确定耦合孔对微波腔模式的影响,并对开耦合孔的圆柱腔进行了相应的理论和模拟研究. 关键词： 微波腔 模式 场耦合 圆柱微波腔