Phase control of electromagnetically induced transparency in a double-Λ system

It is experimentally demonstrated that the effect of electromagnetically induced transparency (EIT) can be controlled through the radiation phases. Corresponding investigations are performed by exciting a sodium atomic vapour by four-frequency laser radiation in a double-Λ configuration. In such a system the nonabsorbing (dark) state, responsible for EIT, is created only for particular values of the relative radiation phase. This phase dependency is confirmed using three different methods of phase control. Additionally, the relative phase is set at defined values in order to adjust the medium to a fixed transmission behaviour.     

Three-photon electromagnetically induced absorption and transparency in an inhomogeneously broadened atomic vapour

We study both theoretically and experimentally three-photon electromagnetically induced transparency and electromagnetically induced absorption resonances in inhomogeneously broadened 85 Rb atomic vapour driven by probe and drive laser radiations. We observe narrow Doppler-free absorption as well as transmission resonances for the probe field when the driving laser field is redshifted from the D₁ or D₂ lines of ⁸⁵Rb; the frequency difference between the drive and probe fields is equal to the hyperfine splitting of the ground state of the atoms, and the probe field is tuned to the centre of the Doppler broadened atomic transition. We theoretically study the spectroscopic effect in both homogeneously and inhomogeneously broadened media. Our numerical simulations are in good agreement with the experimental results.     

Classical analog of electromagnetically induced absorption in plasmonics

The ability to manipulate the phase shift between two resonantly coupled plasmonic oscillators in a controlled fashion has been unavailable up to now. Here we present a strategy to overcome this limitation by employing the benefits of near-field coupling on the one hand and retardation effects due to far-field coupling on the other hand. We theoretically and experimentally demonstrate that in the intermediate regime the coupling of a broad dipolar to a narrow dark quadrupolar plasmon resonance is possible while simultaneously allowing for a retardation-induced phase shift. This leads to constructive interference and enhanced absorption. The observed phenomenon can thus be termed a classical analog of electromagnetically induced absorption.     

Radiation trapping under conditions of electromagnetically induced transparency

Reabsorption of spontaneously emitted photons, or radiation trapping, is a process that occurs when light interacts with optically thick media. It is shown, both theoretically and experimentally, that this effect in optically thick atomic vapour leads to a decrease in transmission of coherent laser radiation propagating under conditions of electromagnetically induced transparency (EIT). A simple theory is developed taking into account the radiation trapping, which is in a good agreement with the experimental observations and exact numerical simulation. This allows better understanding of the physics of EIT in general, and properties of dense coherent atomic media in particular.     

All-optical switching based on the electromagnetically induced transparency effect of an active photonic crystal microcavity

We report a new all-optical switching in a two-dimensional photonic crystal microcavity made of semiconductor multiple quantum wells and realized based on the electromagnetically induced transparency effect with exciton and two-exciton energy levels. We use the quantum coherence effects to achieve small absorption of the probe field, and the absorption of the probe field can be adjusted by controlling the pump field and decay rate. We turn the control field into pulses of light field so that we can regulate the efficiency of the switch. Through selecting the appropriate control light field intensity, we can obtain a switching efficiency of 85% and a switching time is 10 ps. This result can be used for the development of new types of nanoelectronic devices for realizing the switching process.     

Co-existing of dressed non-linear gain and electromagnetically induced absorption

The dressed parametric four-wave mixing (FWM) process has been investigated in hot atomic rubidium vapor. We use a strong pumping field to generate entangled photon pairs of spontaneous parametric FWM (SP-FWM) which can be enhanced by an external dressing effect. Seeding probe beam into the Stokes or anti-Stokes (SP-FWM) channel will form the parametric amplified FWM (PA-FWM) process, then the non-linear gain and electromagnetically induced absorption (EIA) are observed, caused by the internal dressing effect. However, with scanning of pumping field the absorbing background will vanish, which will result in drastic increase in PA-FWM signal gain.     

Physics of electromagnetically induced chirality and anti-symmetric wave transmission

ABSTRACT

Chiral materials possess some unusual properties which make them interesting for useful applications in nanophotonics. In this work, we review the basic techniques used to achieve electromagnetically induced chirality in initially isotropic materials and mention some of their novel operations. Next, we investigate the transmission characteristics of two different multi-level atomic models in which chirality is introduced by magnetoelectric cross coupling of external electromagnetic fields with atomic transitions, leading to quantum coherence. The left-(lcp) and right-circularly polarized (rcp) beams, the two eigenmodes of a chiral medium, are shown to transmit in an anti-symmetric manner with respect to the probe field detuning and control field magnitude variations. This selective transmission of a particular mode at specific detunings may find applications in optical isolation and storage. We further demonstrate that the driving control fields and their effective phase can be used as tuning knobs to manipulate the medium's birefringence and the transmission of the eigenmodes.     

Applications of electromagnetically induced transparency to quantum information processing

Abstract

We provide a broad outline of the requirements that should be met by components produced for a Quantum Information Technology (QIT) industry, and we identify electromagnetically induced transparency (EIT) as potentially key enabling science toward the goal of providing widely available few-qubit quantum information processing within the next decade. As a concrete example, we build on earlier work and discuss the implementation of a two-photon controlled phase gate (and, briefly, a one-photon phase gate) using the approximate Kerr nonlinearity provided by EIT. In this paper, we rigorously analyze the dependence of the performance of these gates on atomic dephasing and field detuning and intensity, and we calculate the optimum parameters needed to apply a π phase shift in a gate of a given fidelity. Although high-fidelity gate operation will be difficult to achieve with realistic system dephasing rates, the moderate fidelities that we believe will be needed for few-qubit QIT seem much more obtainable.     

High-speed impact of electromagnetically sensitive fabric and induced projectile spin

This work deals with the dynamic contact of a rigid body with a deformable electromagnetically sensitive fabric structure, represented by a network model. Of particular interest are the electromagnetically induced forces generated on the fabric, which are proportional to the external electric field (E ^EXT ) and the velocity crossed with the external magnetic field (v × B ^EXT ). These forces transmit reactions to the rigid contacting object, which can induce rotational motion. Modeling and simulation of this effect can be useful in ballistic shielding applications, because the rotation of an incoming, ogival, projectile allows it to be more easily impeded. A modular formulation for the deformation of impacted fabric structures, represented by a network model, is developed in this paper, characterized by (1) stretching of interconnected yarn networks, described by simple constitutive relations, including yarn damage, (2) interaction with impacting objects, incorporating contact with friction and (3) electromagnetic sensitivity and actuation, demonstrating how the Lorentz force can be harnessed to break symmetric deformation patterns in order to induce spin onto an incoming object, whether that object is electromagnetically sensitive or not.     

Observation of electromagnetically induced photonic band gaps in hot two-level atoms

In this paper, two-level thermal Cs atoms are used to observe electromagnetically induced photonic band gaps with a strong symmetric and two types of asymmetric standing-wave (SW) driving fields. One main band and two sidebands are measured for the transmitted and reflected spectra. We carry out physical interpretation about the observations in SW-dressed atom picture and employ method of Fourier transformation to solve density-matrix equations for hot two-level system to simulate the experimental results. The numerical analyses are consistent with the experimental observations for properties of electromagnetically induced photonic band gaps.     

一种自动测试系统软件的开放式架构设计与实现

为满足综合测试系统灵活配置和扩展要求，推出了自动测试系统软件的开放式架构设计。该架构设计结合虚拟仪器思想和面向对象技术，达到了系统灵活配置、可扩展、可复用的目的。提出了一种系统软件的通用设计方法，普遍适用于同类系统的搭建。重点介绍了关键类的设计、系统柔性的实现以及基于VC的关键功能实现。该设计体现了在需求发生变动时系统的柔性，其正确性在实践中得到了验证。     

Generation of induced Smith-Purcell radiation: free-electron laser in open system

We have used the framework of the dispersion equation to study coherent Smith–Purcell (SP) radiation induced by a relativistic magnetized electron beam in the absence of a resonator. As an important example of the application of the obtained results of our previous paper JMO v.57, 2060, (2010) the growth rate of SP FEL in the case with a rectangular grating was calculated. The growth rate of the instability is proportional to the square root of the electron beam current. The calculated results are consistent with the experimental data obtained by Urata et al. [Phys. Rev. Lett. 80, 516 (1998)].     

Chromium diffusion in GaAs in an open system

We have studied chromium diffusion from a surface layer produced by thermal evaporation into n-type GaAs in a flowing inert-reducing atmosphere. The temperature dependences of the Cr diffusivity and solubility in GaAs are well represented by Arrhenius equations with D ₀ = 1.7 × 10^?2 cm²/s and Q _D = 1.43 eV for the diffusivity and C _Cr ⁰ = 8.9 × 10²¹ cm^?3 and Q _Cr = 1.22 eV for the solubility.     

A-B两层铁磁耦合薄膜中的自旋波共振谱

在Heisenberg模型的基础上,计入垂直于膜面的磁场,考虑表面各向异性场情况下,精确求解了简立方结构双层异质铁磁薄膜中的自旋波低能量子本征值问题.又在此基础上加上平行于膜面方向的交变磁场,应用量子理论严格推导了两层异质铁磁耦合薄膜中的自旋波共振激发,并在不同表面条件下计算了各种形式的自旋波共振谱.结果表明:1)共振峰强度与交变场振幅的平方成正比,与本征态中单个自旋反转对应的几率幅的模的平方成正比,即自旋波共振的平方律关系;2)由于表面各向异性场对不同形式的自旋波激发谱都产生影响,从而也影响自旋波的共振谱.     

Doppler-enhanced gain in an open ladder inversionless lasing system

Abstract

An analysis is made of the effect of Doppler broadening on the gain in an open ladder inversionless lasing system. It is shown that for co-propagating probe and driving fields, the gain does not monotonously decrease or increase with increasing Doppler width, and at a suitable Doppler width one can obtain a maximum value much larger than that without Doppler broadening. For counterpropagating probe and driving fields, when the Doppler width is large enough, gain oscillation occurs, and the oscillation amplitude and region increase with increasing Doppler width. This conclusion is very different from that obtained in the corresponding closed system.     

Plasmonic analog of electromagnetically induced transparency in planar metamaterials: manipulation and applications

In this article, we have investigated an analog of electromagnetically induced transparency (EIT) in planar metamaterials by a metallic regular triangle (RT) embedded in split ring (SR) nanostructure. It is demonstrated that, depending on the different coupling ways between the RT and the SR, the EIT-like spectral response can be actively modulated by simply adjusting the incident light polarization angle. Based on this observation, an on-to-off active modulation of the EIT-like transparency window can be realized, and it can serve as the base for an optical switching with the switching efficiency exceeding 95%. The size of the RT finely controls the coupling strength between the RT and the SR. It is shown that the EIT-like transparency window can be enhanced or suppressed by adjusting the size of the RT, which shows the big modulation to the EIT-like spectral response. Furthermore, the transmission spectra show potential applications in sensing due to high sensitivity of about 600 nm/RIU with figure of merit exceeding 36 to the surrounding environment.     

基于Lex和Yacc的开放式并联机床后置处理系统开发

针对常见数控系统的后置处理模块具有专用、封闭等特点,从而限制了其在新型并联加工装备中的应用的问题,研究了开放式并联机床后置处理系统开发的关键环节.首先,基于Lex和Yacc编译工具实现了数控代码的解析功能,此功能能够适用于不同体系的数控代码格式,提高数控系统的开放性和通用性.其次,对并联机床后置处理中的关键算法进行了研...