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.     

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.     

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.     

高Q值THz类EIT超材料及传感特性研究

设计了一种具有类电磁诱导透明(EIT)效应的高Q值太赫兹超材料。该结构单元由上下平行的双金属线及中间垂直的单金属线组成。分别对单金属线、双金属线及组合结构进行仿真,分析了组合结构中金属线的位置和尺寸对透射率及品质因数Q的影响。结果表明,随着单金属线的水平移动产生了类EIT效应,透射率和Q值随着偏移距离的增大而发生变化,通过调整结构和尺寸可以实现不同Q值。通过优化,当偏移距离为8 μm时,在0.73 THz附近得到一个3 dB带宽约为11.56 GHz的透明窗,相应的Q值为63.09,其透射率为0.50。最后,对谐振器的传感特性进行了测量,其折射率灵敏度为60.69 GHz/RIU,FOM值为5.25/RIU,具有优异的传感特性。     

Polarization-selective photonic band gap induced by electromagnetically induced transparency

A tripod-type system driven by a weak linearly polarized probe light and a π-polarized standing-wave control light is studied. The results show that double photonic band gaps (PBGs) can be obtained at two different frequencies due to Zeeman splitting induced by an external magnetic field. This allows us to selectively manipulate the σ_± components of the probe light, which exhibits polarization selective features. These peculiar features can be employed to devise schemes for a polarization beam splitter and polarization selective routing. Furthermore, the dependence of the gap position on the magnetic field provides an additional control of the PBGs structure. Thus, double tunable PBGs can be achieved.     

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.     

Nanoscale all-optical plasmonic switching using electromagnetically induced transparency

An all-optical switch composed of two interacting nanoparticles in front of an optical dielectric slab waveguide is proposed. An incident optical signal is coupled to the optical waveguide after scattering by the two nanoparticles. The scattered fields interfere constructively or destructively depending on the degree of optical transparency the nanoparticles induced by an optical control signal. The considered nanoparticles have a metallic core coated by an outer shell with three-level clusters such that the nanoparticles can exhibit electromagnetically induced transparency. A dipole-approximation model-based analysis reveals that a high rejection ratio can be achieved using the proposed configuration.     

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.     

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.     

Plasmonic electromagnetically induced transparency in metallic nanoparticle-quantum dot hybrid systems

We study the variation of the energy absorption rate in a hybrid semiconductor quantum dot-metallic nanoparticle system doped in a photonic crystal. The quantum dot is taken as a three-level V-configuration system and is driven by two applied fields (probe and control). We consider that one of the excitonic resonance frequencies is near to the plasmonic resonance frequency of the metallic nanoparticle, and is driven by the probe field. The other excitonic resonance frequency is far from both the plasmonic resonance frequency and the photonic bandgap edge, and is driven by the control field. In the absence of the photonic crystal we found that the system supports three excitonic-induced transparencies in the energy absorption spectrum of the metallic nanoparticle. We show that the photonic crystal allows us to manipulate the frequencies of such excitonic-induced transparencies and the amplitude of the energy absorption rate.     

Supercontinuum generation in quantum wells facilitated by electromagnetically induced transparency

In this paper, employing numerical simulation, we examine the possibility of generation of optical supercontinuum (SC) in a multiple quantum well (MQW) system facilitated by electromagnetically induced transparency. Within the transparency window created by a control laser beam in a MQW, another probe pulse experiences negligible loss and large optical non-linearity that has been exploited to obtain the optical SC. With 1.0 pico-second ‘sech’ probe pulses of 500 W peak power at wavelength 739.7 nm, the numerically simulated SC spectrum at the end of the 9.377 μm long MQW extends from 550 to 1000 nm. The spectrum is asymmetric, contains large number of oscillations which is attributed to the nonlinearity induced self-phase modulation and modulation instability. This investigation may lead to the fabrication of on-chip SC sources that can be easily integrated with other semiconductor devices.     

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.     

Manipulating the focal shift in a medium with electromagnetically induced transparency

By approximating the index distribution of a medium with electromagnetically induced transparency (EIT) as a gradient index (GRIN), propagation laws in the medium with EIT can be obtained. Transmission properties in an optical system with an EIT medium are analyzed. The results show that, unlike the case in the ordinary GRIN medium, the refractive index of EIT medium has the better controllability. Consequently, discussions are focused on how to conveniently manipulate the focal shift of the input in the EIT by means of controlling the index of the medium. Additionally, the speckle radius on the location of the actual focus can be diminished by adjusting some parameters in the EIT medium.     

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.     

Thermally tunable electromagnetically induced transparency in terahertz frequency with superconducting resonators

We present a design of electromagnetically induced transparency operating in terahertz regime based on near-field coupling between a metal strip and split ring resonators (SRR) made of superconducting film. When the SRR work in superconducting state, the transparency window can be thermally controlled. A pair of SRR has been introduced as the dark mode to enhance the coupling, which results in a broadening and high transmittance of near unity of the transparency window. These results may lead to potential applications in tunable terahertz devices, slowing light, and sensing technology.     

Ultra-slow soliton pairs in four-level inverted Y-system via electromagnetically induced transparency

Using the Schrödinger Maxwell equations, we theoretically investigate the propagation properties of probe and mixing fields in a lifetime-broadened inverted-Y type cold atomic medium. This system is driven by two strong control (pumping and coupling) fields. The results reveal that the probe (or mixing) field consists of two modes with different group velocity and absorption. Under slowly varying envelope approximation, we discuss the propagation equation of the probe (or mixing) field, which includes the high-order nonlinear term. The solutions show that optical solitons pairs can be generated in the cold atom medium with ultra-slow group velocities.     

Buffer-gas-induced narrowing of electromagnetically induced transparent spectra for an open system

We have investigated the spectra of the electromagnetically induced transparency (EIT) when a cell is filled with a buffer gas. Our theoretical results show that the buffer gas can induce a narrower spectra line and steeper dispersion than those of the usual EIT case in a homogeneous and Doppler broadened system. The linewidth decreases with the increase of the buffer gas pressure. This narrow spectra may be applied to quantum information processing, nonlinear optics and atomic frequency standard.     

Low-temperature plasmonics of metallic nanostructures

The requirements for spatial and temporal manipulation of electromagnetic fields on the nanoscale have recently resulted in an ever-increasing use of plasmonics for achieving various functionalities with superior performance to those available from conventional photonics. For these applications, ohmic losses resulting from free-electron scattering in the metal is one major limitation for the performance of plasmonic structures. In the low-frequency regime, ohmic losses can be reduced at low temperatures. In this work, we study the effect of temperature on the optical response of different plasmonic nanostructures and show that the extinction of a plasmonic nanorod metamaterial can be efficiently controlled with temperature with transmission changes by nearly a factor of 10 between room and liquid nitrogen temperatures, while temperature effects in plasmonic crystals are relatively weak (transmission changes only up to 20%). Because of the different nature of the plasmonic interactions in these types of plasmonic nanostructures, drastically differing responses (increased or decreased extinction) to temperature change were observed despite identical variations of the metal's permittivity.