Transparency induced by the quantum interference of a six-level atom in photonic crystals with defect modes

The absorption-dispersion spectra of a six-level atom embedded in double-band photonic crystals are investigated. It is shown that if there is no defect mode in the photonic band gap, there are three types of transparency windows appear in the absorption-dispersion spectra. If a defect mode is introduced into the photonic band gap, we found some additional transparency windows in the absorption-dispersion spectra. One type of them appears as long as the defect mode exists, but the others appear only when the quantum interference occurs. The transparency windows can be changed by varying the parameters of the defect mode.     

XOR/XNOR directed logic circuit based on coupled‐resonator‐induced transparency

The coupled‐resonator‐induced transparency (CRIT) effect in parallel‐coupled double microring resonators (MRRs) has been widely studied, and various applications based on the CRIT have been demonstrated. As an application of the CRIT, we propose and demonstrate a directed logic circuit that can implement the XOR and XNOR operations. Two electrical signals applied to the two MRRs represent the two operands of the logical operations, and the operational results are represented by the output optical signal. As a proof‐of‐concept, the thermo‐optic modulating scheme is employed with an operational speed of 10 kbps.     

Control of dispersion in fiber coupled resonator-induced transparency structure

Induced transparency phenomena and strong dispersion can be produced in a coupled resonator induced transparency(CRIT) structure.In this paper,we investigate the influences of structure parameters,such as amplitude reflection coefficient and loss,on transmission spectrum and dispersion of CRIT structure,and further study the control of dispersion in the structure.The results show that in the CRIT structure,adjusting the loss of resonators is an effective method of controlling dispersion and producing simultaneous normal and abnormal dispersion.When we choose approximate amplitude reflection coefficients of the two couplers,the decrease of transmittance due to loss could be effectively made up.In the experiment,we achieve the control of dispersion and simultaneous strong normal and abnormal dispersion in the CRIT structure comprised of fiber.The results indicate the CRIT structure has potential applications in optical signal processing and optical communication.     

光子晶体中四能级系统的量子相干效应

研究了处于光子带隙材料中的四能级原子系统的电磁感应透明、自发辐射和光子开关效应，分析了其稳态与瞬态特性, 发现特殊的模密度能够导致反常的吸收、色散、自发辐射及瞬态无反转增益, 并可以通过外加调制场进行控制.详细讨论了特殊频率处模密度的变化对透明窗口和光子开关效应的影响. 关键词： 光子带隙材料 电磁感应透明 模密度 光子开关     

Coupled-resonator-induced transparency in two microspheres as the element of angular velocity sensing

We proposed a two-coupled microsphere resonator structure as the element of angular velocity sensing under the Sagnac effect.We analyzed the theoretical model of the two coupled microspheres,and derived the coupled-resonatorinduced transparency(CRIT) transfer function,the effective phase shift,and the group delay.Experiments were also carried out to demonstrate the CRIT phenomenon in the two-coupled microsphere resonator structure.We calculated that the group index of the two-coupled sphere reaches n_g = 180.46,while the input light at a wavelength of 1550 nm.     

Using Josephson vortex lattices to control terahertz radiation: tunable transparency and terahertz photonic crystals

The Josephson vortex (JV) lattice is a periodic array that scatters electromagnetic waves in the THz-frequency range. We show that JV lattices can produce a photonic band-gap structure (THz photonic crystal) with easily tunable forbidden zones controlled by the in-plane magnetic field. The scattering of electromagnetic waves by JVs results in a strong magnetic-field dependence of the reflection and transparency. Fully transparent or fully reflected frequency windows can be conveniently tuned by the in-plane magnetic field. These proposals are potentially useful for controllable THz filters.     

基于新型三环谐振器的诱导透明效应分析

针对谐振式微腔的应用需求, 提出了一种新型三环谐振式微腔结构, 类似于原子系统中的电磁诱导透明, 耦合诱导透明(CRIT)效应在一个新的光学微腔系统中已被实验证明. 该结构在硅基上由三个尺寸完全一样的微环腔组成, 通过理论分析、制备和实验测试, 能够观察到CRIT现象, 其频谱具有低群速的狭窄透明峰, 与光栅耦合器的耦合效率为34%, 并且谐振器的品质因数达到了0.65×10⁵, 同时, 失谐的谐振波长可以通过温度变化来控制, 这在旋转传感、光滤波器、光存储器等方面的应用有重要意义.     

控制场对M型原子系统吸收色散性质的影响

运用数值模拟方法讨论了控制场的变化对M型五能级原子系统相对于探测场的吸收和色散等光学性质的影响.结果表明,改变控制场拉比频率时,系统的吸收和色散性质会发生规律性变化.在特定区域会呈现电磁感应透明窗口,其中透明窗口的数量与外加控制场数目成正比,而透明窗口宽度与拉比频率大小相关,拉比频率越大,透明窗口越平坦,当拉比频率减小,透明窗口变窄同时介质色散增强可获得慢光速光脉冲.     

Optical properties and electromagnetically induced grating in a hybrid semiconductor quantum dot-metallic nanorod system

An artificial molecule consisting of an SQD and an MNR embedded in 3D photonic crystal is proposed to realize EIG. Using the quantum mechanical density matrix approach, we have derived an expression of the absorption coefficient in the SQD in presence of MNR. Nanoparticle geometry can modify the local fields that determine SQD-MNP coupling and to engineer the hybrid optical response. The probe absorption is reduced via a strong coupling field, demonstrating spectral transparency window. It is worth noting that the background affects the relaxations of SQD. So, by making use of 3D photonic crystal as the background medium, reduced decay rate and consequently substantial local-field enhancement rate are provided. Based on EIT effect and a strong standing-wave field, diffraction grating is achievable. The first-order diffraction intensity can reach its maximum by tuning the system parameters. This model may be useful in designing new devices in all-optical communication.     

Optical precursors in coupled-resonator-induced transparency

We experimentally examined the propagation of temporally square modulated optical pulses through a coupled ring resonator. Sharp transient spikes appeared as the square pulses entered the system. The main signal gradually grew up through coupled-resonator-induced transparency (CRIT), with the time constant determined by a second resonator. Transient spikes were attributed to the higher and lower spectral components of the incident pulse, to which the resonators cannot respond; hence, they were interpreted as optical precursors. The experiments, therefore, demonstrated that precursors and the main signal can be observed separately, with amplitudes comparable to that of the incident step in CRIT.     

Zitterbewegung in the honeycomb photonic lattice

The propagation of a wave packet in a honeycomb photonic lattice has been studied using the time-dependent wave packet dynamics. It is found that the wave packet, superposed from the positive and negative energy modes at the vicinity of the two inequivalent Dirac points, can transform into a double-ring structure, which is caused by the interference between the two positive and negative energy modes around the Dirac points and is closely related to the Zitterbewegung (ZB). Also, a possible way to detect the ZB effect is proposed in the honeycomb photonic lattice.     

Manipulation of tunneling induced transparency windows and optical switching features in fivefold quantum dot molecules

Transient and steady-state behavior of the probe absorption in a multiple quantum dot (QD) molecule composed of five quantum dots molecules (with a center dot and four satellite dots) is explored with application in all-optical switching. We find that the absorption spectra of the light pulse can be efficiently modified via the effect of inter-dot tunnel couplings of QDs and incoherent pumping field. Results show that depending on the values of system parameters, at least one and at most four tunneling induced transparency (TIT) windows can be established in the multiple QD medium. We then investigate the dynamical behavior of the probe absorption-amplification as well as the optical switching in pulsed regime. By adjusting the incoherent pumping rate, the required switching time for changing the gain to the absorption or vice versa is then estimated approximately to be 20.7 nanosecond (ns), that is an appropriate time for such a QDM-based switch.     

A high sensitivity optical gyroscope based on slow light in coupled-resonator-induced transparency

We designed ring-in-ring planar resonator which is coupled with a straight waveguide to yield coupled-resonator-induced transparency (CRIT). The model shows an obvious effect which has a direct analogy with the phenomenon of the electromagnetically induced transparency in quantum systems. Based on this structure, a high sensitive optical gyroscope for measuring absolute rotation is proposed and analyzed. Its sensitivity scales directly with the group index whose can be reached to ¹⁰²-¹⁰⁴ orders of magnitude by using proper parameters.     

电磁感应双光子带隙的产生和控制

基于电磁感应透明技术, 通过求解原子的密度矩阵方程和电磁场的传输矩阵方程, 研究了被行波场和驻波场共同耦合的一个四能级冷原子介质的稳态光学特性, 发现在特定参数下能够产生一个几乎完美的双光子带隙结构, 在这两个光子带隙对应的频率区域内反射率都均匀地超过95%. 通过改变耦合场的强度和频率, 可以方便地调节这两个光子带隙的位置和宽度. 这一双光子带隙结构可用来实现全光路由和全光开关, 有望在全光信息网络中获得应用.     

Light transmission by a three-level emitter embedded in a waveguide-coupled two-mode photonic crystal nanocavity

We investigate light transmission obtained from a three-level V-type emitter embedded in a waveguide-coupled two-mode photonic crystal nanocavity operating in the weak-coupling regime. It is shown that the composite system exhibits double electromagnetically-induced-transparency-like characteristics and a π phase shift while not suffering from absorption in the experimentally available parameter range. The double-frequency transparency of the input light expands the frequency range of EIT and may improve the controllability of EIT. The proposed scheme also provides a way to achieve integrated photonic devices on a chip for applications requiring multiple EIT effect.     

Manipulation of multi-transparency windows and fast-slow light transitions in a hybrid cavity optomechanical system

We study the generation of quadruple-transparency windows and the implementation of a conversion between slow and fast light in a hybrid optomechanical system. By demonstrating the generation of these transparency windows one by one, we analyze the physical mechanism through which each transparency window forms in detail. Additionally, we discuss how the system parameters affect the formation of transparency windows and conclude that the location, width, and absorption of each transparency window can be arbitrarily manipulated by varying the appropriate parameters. Moreover, when the pump field is changed from red to blue detuning, conversions between slow and fast light occur in the output field. These interesting properties of the output field can be applied to achieve the coherent control and manipulation of light pulses using cavity optomechanical system.     

The influence of EIT effect with double windows on electromagnetic characteristics of quasi-Λ-four-level atomic system

In this paper, the electromagnetic characteristics of quasi-Λ-four-level atomic system influenced by electromagnetically induced transparency (EIT) effect with double windows are investigated theoretically. It is shown that the permittivity can get two negative extreme values in transparent window extents and the permeability can realize negative value. Consequently, the atomic system can obtain the negative refraction in discontinuous probe detuning frequency ranges. EIT effect with double transparent windows would extend the tuning frequency range of realizing left handedness in atomic system. Furthermore, due to the strong magnetic transition, the real part of the refractive index and the absorption of atomic system can obtain negative values in the same certain frequency band. Such left-handed quasi-Λ-four-level atomic system may become an active medium.     

Dual-band plasmon induced transparency controlled by the polarization of the incident wave

In this paper, a hybridized plasmonic waveguide system is investigated numerically. By coupling plasmonic modes with different waveguide modes, two plasmon induced transparency (PIT) windows with high transmittance and deep modulation can be realized. Through the polarization of the incident wave, the transparency windows can be dynamically controlled.     

Controlled optical properties of a five-level atom embedded in photonic crystals with defect modes

The optical spectra of a five-level atom embedded in a photonic crystal are studied by considering the double-band photonic band gap reservoir with defect modes in the band gap. It is shown that some interesting phenomena such as absorption, transparency, normal or anomalous dispersion, and large amplification of a weak probe field can be observed by modulating system parameters.     

Multiple induced transparency in a hybrid driven cavity optomechanical device with a two-level system

We present a scheme with the multiple-induced transparency windows in a hybrid optomechanical device. By studying the transmission of a probe field through the hybrid device, we show the successive generations of three transparent windows induced by multiple factors including tunneling, optomechanical and qubit-phonon coupling interactions, and analyze the physical mechanism of the induced transparency based on a simplified energy-level diagram of the system. Moreover, the effects of the transition frequency and decay rate of the two-level system on the multiple-induced transparency windows are discussed. We find that the transparency windows can be modulated by the coupling interaction between the qubit and NMR, the decay of qubit and the power of the control field. Therefore, the transmission of the probe field can be coherently adjusted in the hybrid cavity optomechanical device with a two-level system.