Formation mechanism and modulation of electromagnetically induced transparency-like transmission in side-coupled structures

Based on Fabry model and finite-different time-domain(FDTD) method, the plasmonic structure composed of a metal-insulator-metal(MIM) bus waveguide and a side-coupled resonator was investigated. It is found that the transmission features can be regulated by the cavity width and coupling distance. Electromagnetically induced transparency(EIT)-like transmission can be excited by adding an identical resonator on the pre-existing structure. Combining the foregoing theoretical analysis with coupled mode theory(CMT), the formation process of the EIT-like transmission was detailedly analyzed. EIT-like transmission can also be excited in plasmonic structure with two detuned resonators. By altering the structure parameters, the transparency window can be purposefully modulated. With the merits of compact structure and simplicity in fabrication, the proposed structures may have a broad prospect of applications in highly integrated optical circuits.

Double-resonance optical-pumping effect and laddertype electromagnetically induced transparency signal without Doppler background in cesium atomic vapour cell

In a Doppler-broadened ladder-type cesium atomic system （6S1/2 6P3/2-8S1/2）, this paper characterizes electro- magnetically induced transparency （EIT） in two different experimental arrangements, and investigates the influence of the double-resonance optical-pumping （DROP） effect on EIT in both arrangements. When the probe laser is weak, DROP is explicitly suppressed. When the probe laser is moderate, population of the intermediate level （6P3/2 FI = 5） is remarkable, therefore DROP is mixed with EIT. An interesting bimodal spectrum with the broad component due to DROP and the narrow part due to EIT has been clearly observed in cesium 6S1/2 F = 4-6P3/2 F^1= 5-8S1/2 F^11 = 4 transitions.

A Metamaterial Design Based on Electromagnetic Induction Transparency-Like Effect and Its Slow-Wave Performance

This paper proposes a new metamaterial design that can achieve electromagnetic induction transparency-like (EIT-like) effects in the microwave band. The unit structure of metamaterials consists of square rings and metal wires. The square ring acts as the “bright state” and the metal wire acts as the “dark state”. The destructive interference between the bright state and the dark state produces an EIT-like effect. In the simulation results, a transparent window centered at 4.00 GHz can be observed in the transmission spectrum. By studying the phase change of the transparent window, it is found that the group delay of the metamaterial structure can reach 0.39 ns at 4.00 GHz. This paper also studies the influence of the refractive index of the medium on the EIT-like effect. Numerical simulations show that such metamaterial is very sensitive to the refractive index of the medium, and the sensitivity is 15 mm/RIU. Our design can be extended to other frequency bands and may have potential applications in filtering, sensing, slow-light devices, and nonlinear optics.

Off-resonant double-resonance optical-pumping spectra and their application in a multiphoton cesium magneto-optical trap

We present an investigation of double-resonance optical pumping （DROP） spectra under the condition of single-photon frequency detuning based on a cesium 6S1/2-6P3/2-8S1/2 ladder-type system with a room-temperature vapor cell. Two DROP peaks are found, and their origins are explored. One peak has a narrow linewidth due to the atomic coherence for a counterpropagating configuration; the other peak has a broad linewidth, owing to the spontaneous decay for a coprop-agating configuration. This kind of off-resonant DROP spectrum can be used to control and offset-lock a laser frequency to a transition between excited states. We apply this technique to a multiphoton cesium magneto-optical trap, which can efficiently trap atoms on both red and blue sides of the two-photon resonance.

Sideband-Induced Two-Photon Transparency

We show that it is possible to use a single sideband to induce two-photon transparency in a three-level cascade medium. The medium simultaneously absorbs two photons as a one-step process when the middle level is far off one-photon resonance. A resonant sideband coupling on the upper transition and the two-photon one-step process drive the medium into a trapped state, and the dominant component is the ground state. Thus almost all population is trapped in the ground state and the two-photon absorption is dramatically suppressed. We present a numerical calculation for arbitrary values of the atomic and field parameters and also provide an analytic description for the required conditions.

Electromagnetic interference assessment of a train-network-pipeline coupling system based on a harmonic transmission model

The harmonics and resonance of traction power supply systems(TPSSs)aggravate the electromagnetic interference(EMI)to adjacent metallic pipelines(MPs),which has aroused widespread concern.In this paper,an evaluation method on pipeline interference voltage under harmonic induction is presented.The results show that the Carson integral formula is more accurate in calculating the mutual impedance at higher frequencies.Then,an integrated train-network-pipeline model is established to estimate the influences of harmonic distortion and resonance on an MP.It is revealed that the higher the harmonic cur-rent distortion rate of the traction load,the larger the interference voltage on an MP.Particularly,the interference voltage is amplified up to 7 times when the TPSS resonates,which is worthy of attention.In addition,the parameters that affect the variation and sensitivity of the interference voltage are studied,namely,the pipeline coating material,locomotive position,and soil resistivity,indicating that soil resistivity and 3PE(3-layer polyethylene)anticorrosive coating are more sensitive to harmonic induction.Field test results show that the harmonic distortion can make the interference voltage more serious,and the protective measures are optimized.

1000MW发电机出口半绝缘电压互感器交流耐压试验方法研究

对1000MW火力发电机组的发电机出口浇筑型电磁式电压互感器(简称PT)进行交流耐压试验时,因为PT变比较大且单个二次绕组对一次绕组、其他二次绕组及地的电容较大,如果采用传统的三倍频感应耐压试验,其二次绕组很容易过载,解决办法有两个:其一可以采用电抗器并联补偿的方式减少流过二次绕组的电流;其二采用串联谐振装置直接从一次侧加压。

Reversible switching of electromagnetically induced transparency in phase change metasurfaces

Metasurface analogue of the phenomenon of electromagnetically induced transparency(EIT)that is originally observed in atomic gases offers diverse applications for new photonic components such as nonlinear optical units,slow-light devices,and biosensors.The development of functional integrated photonic devices requires an active control of EIT in metasurfaces.We demonstrate a reversible switching of the metasurface-induced transparency in the near-infrared region by incorporating a nonvolatile phase change material,Ge2Sb2Te5,into the metasurface design.This leads to an ultrafast reconfigurable transparency window under an excitation of a nanosecond pulsed laser.The measurement agrees well with both theoretical calculation and finite-difference time-domain numerical simulation.Our work paves the way for dynamic metasurface devices such as reconfigurable slow light and biosensing.

Coherent effect of triple-resonant optical parametric amplification inside a cavity with injection of a squeezed vacuum field

In theory, we study the quantum tluctuatlons ot tlae suDllarmonlc renecteu nela Irom a ulplc-rc^ulltUtt IdU^ClIClatC optical parametric amplifier （OPA） inside an optical cavity. We discuss two cases, where the linewidth of the harmonic field is either much narrower or broader than the subharmonic field. Since an electromagnetically-induced-transparency （EIT）-like effect can be simulated in a triple-resonant OPA, the output spectra from a triple-resonant OPA with a squeezed vacuum input may simulate the phenomenon of the response of an EIT medium for squeezed states. This scheme can be implemented with present experimental setups.

一种取向诱导的多共振超材料及折射率传感性能分析

提出了一种新型取向诱导的多谐振太赫兹超材料。超材料由双金属线(DCW)和非对称开口环谐振器(ASR)构成。数值仿真表明,当改变SR绕其中心旋转的角度时,导致亮模式和暗模式的耦合作用发生改变,产生不同类型的谐振现象。当SR旋转角为15°时,由于谐振结构对称性被打破,分别在0.67 THz、0.82 THz和0.83 THz出现了类EIT、四偶极子共振和Fano共振现象;当SR旋转角度为90°时,所有共振现象最终消失。此外分析了SR旋转角度为15°时的超材料传感性能,类EIT谐振峰、四偶极子共振和Fano共振灵敏度分别为127、107和108 GHz/RIU。该超材料作为折射率传感器,最大理论灵敏度达到127 GHz/RIU,表明该超材料具良好的传感特性。

双光子共振激发的里德堡原子数目估计

现有量子微波测量系统中,碱金属原子气室是其核心物理组件。目前,原子气室的检测性能参数主要包括气室玻壳折射率、透光率及内部原子配比、密度等,不能直接体现出气室内被激发的里德堡原子数目,不利于装置整体性能的表征和优化。根据理想气体状态方程,综合里德堡阻塞效应、气体原子分布等因素,建立了双光子共振激发的里德堡原子数目理论计算模型,提出了基于最优化电磁诱导透明光谱的里德堡原子数目估计方法,并采用两种不同形状铯原子气室进行实验估算,其结果与理论计算结果基本一致。

类电磁诱导透明效应在硅基微环谐振腔中的实现与优化

为在硅基光波导上实现类电磁诱导透明效应,设计并加工了基于绝缘体上硅的串联双环结构.通过300℃到1 200℃热氧化退火、缓冲刻蚀液湿法腐蚀以及1 000℃高温氮气退火等波导结构的后期处理,利用垂直光栅耦合的方式输入及输出信号,观测到了类电磁诱导透明效应.分析了两环间不同间距对类电磁诱导透明效应的影响,结果表明:工艺中单环Q值达到5.1×104,类电磁诱导透明效应透明峰的带宽约为500MHz.

电热火工品感应电流与连续电磁波频率的关系

电热火工品电磁波环境下的响应效应与规律性是开展电磁安全性研究及环境适应性设计的基础。为了得到影响电热火工品电磁响应的重要参数与规律,用实验室建立的连续电磁波环境模拟系统与感应电流测试装置,研究了电热火工品电磁波环境下感应电流与频率间的关系。结果表明,电热火工品感应电流与电磁波频率间存在谐振关系。以火工品垂直脚线状态为例,其脚线长度为0.72 m时,对应感应电流谐振频率约为200 MHz。在此基础上开展的理论计算与仿真研究,证实了火工品脚线的天线特性是影响其电磁响应的关键因素。电热火工品在其脚线长度对应的谐振频率点处感应电流值最大。

热原子系综中双暗共振及亚多普勒吸收谱的实现

分别通过实验和数值模拟给出了在四能级倒Y模型原子系统中的双窗口电磁感应透明现象.结果表明,通过调解2个耦合场的失谐可控制透明窗口的位置.双窗口电磁感应透明现象的物理本质是由于2个耦合场同时作用于原子系统中而形成的双暗共振,同时双暗共振间的相互作用将探测场在目标频率处的吸收谱线压窄,并在实验上得到频谱宽度(半高宽)约为30 MHz的探测场共振吸收谱线.

耦合谐振电路系统中的Fano共振现象

常见的共振响应谱表现为近似对称分布的洛伦兹线型,而Fano共振则表现出明显的非对称的响应谱.尝试在普通物理实验层次展示Fano共振现象,建立基础实验与前沿研究的联系,通过构建RLC耦合谐振电路系统,在实验上展示了Fano共振现象,作为其中的一种特殊情况,还展示了类似电磁感应透明的现象,并通过理论公式的计算解释了实验结果.

基于微环谐振腔的耦合谐振光波导反射镜

研究了一种基于微环谐振腔的耦合共振光波导反射镜。基于耦合模理论,对这种新型波导反射镜的反射光谱进行了数值分析,详细讨论了直波导与微环谐振腔之间的耦合系数和相邻微环谐振腔之间的耦合系数对反射光谱的影响。计算结果表明这种反射镜的反射光谱存在多峰结构,在弱耦合的情况下可以实现波长选择性反射滤波,并且发现在这种波导反射镜中存在类似于原子系统中电磁诱导透明现象的耦合共振诱导透明现象。

风致涡激共振对永磁直线发电机电磁特性的影响

基于风致涡激共振无叶片风力机的需要,研制了一台圆筒形永磁直线发电机,对其在匀速状态下的空载特性、负载特性进行了仿真分析,验证了该永磁直线发电机的可行性。采用反正切函数和正弦函数的乘积逼近发电机次级在共振时的运动轨迹,给出了输出电压的表达式,并探讨了发电机在不同风速和振幅下的电磁特性。结果表明,发电机在捕能柱共振区间(锁频区间)下能获得最大的电压、输出功率和效率,且随着次级运动振幅的增大,发电机的电压、输出功率和效率均增大,当其振幅倍数大于1后,发电机效率的增幅变缓。该结论可为无叶片风力发电机的研发提供指导。

基于全介质超表面的电磁诱导透明研究

设计了一种基于TiO2介质的全介质电磁诱导透明超表面模型,该结构由两根十字垂直交叉的介质棒和四个介质方块组成.在入射电磁场的作用下,介质棒中直接被入射电磁场激励的米氏电谐振通过相互耦合作用激发了介质方块中的磁共振,并产生谐振模之间的相消干涉,从而产生了类电磁诱导透明现象.利用电磁仿真软件和双谐振子耦合模理论,模拟计算和定量分析了类电磁诱导透明效应,结果表明:在电磁波正入射下,该结构在0.552THz处产生一透射率接近96%的透明窗口.由于其结构单元具有4度旋转对称性和多个暗模谐振元素,使得诱导透明效应出现较宽频带且呈现出对入射电场极化方向不敏感的特性.

串联双微环谐振器透射谱特性分析

研究串联双微环谐振器的透射谱特性.分析了环间损耗、透过率、微环半径以及环内耦合对透射谱的影响.研究结果表明,当其透射谱都是类电磁感应透明型时,随微环损耗增加,透射谱宽不影响,而其峰值改变;随微环间透射率的增加,峰值变化明显,谱宽变宽;随微环半径增加,峰值变小,谱宽变宽;随着环间耦合的变化,同样显著的影响着透射谱的形状.从而可以通过调节环内耦合、环间损耗和透过率来调控透射谱的谱宽.

单个回音壁微腔中Fano共振现象的观测（英文）

实验研究了香肠状回音壁光学微腔,测量了单个微腔的光学传输谱线.实验结果表明,当从两端拉伸香肠状微腔的时候,观测到的光学模式的共振波长会随着拉伸量的增加而减小,而且不同模式的共振波长减小的速度存在差异.通过拉伸香肠状微腔的方法,实验观察到了单个香肠状微腔中的Fano共振现象.另外,实验上也观测到了与Fano共振现象相关的类电磁诱导透明现象。实验所涉及到的回音壁模式的品质因子高达108.