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.     

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.     

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.     

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.     

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.     

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.     

Effective tunability and realistic estimates of group index in plasmonic metamaterials exhibiting electromagnetically induced transparency

We study the phenomenon of the electromagnetically induced transparency in planar and stacked plasmonic metamaterials (MMs) using the finite integration time domain and finite element methods. For such structures, the dependence of the tunability of the inherent structural resonances on geometry design is clarified. We also analyze the performance of recently demonstrated MM designs in terms of the achievable group refractive index and losses, which are of great interest for slowing light applications.     

Quantitative analysis of nanoparticle growth through plasmonics

Plasmon excitation appears to be a powerful and flexible tool for probing in situ and in real time the growth of supported conducting metal nanoparticles. However, although models exist for analysing optical profiles, limitations arise in the realistic modelling of particle shape from the lack of knowledge of temperature effects and of broadening sources. This paper reports on the growth of silver on alumina at 190-675 K monitored by surface differential reflectivity spectroscopy in the UV-visible range. In the framework of plasmonic response analysis, particles are modelled by truncated spheres. Their polarizabilities are computed within the quasi-static approximation and used as an input to the interface susceptibilities model in order to determine the Fresnel reflection coefficient. The pivotal importance of the thermal variation of the metal dielectric constant is demonstrated. Finite-size effects are accounted for. As size distribution fluctuations contribute marginally to the lineshape compared to the aspect ratio (diameter/height) distribution, a convolution method for representing the experimental broadening is introduced. Effects of disorder on the lineshape are discussed. It is highlighted that beside the quality of the fit (not a proof by itself!), physical meaning of the parameters related to the sticking probability, growth and wetting is crucially required for validating models. The proposed modelling opens interesting perspectives for the quantitative study of growth via plasmonics, in particular in the case of noble metals.     

Subluminal and superluminal light propagation via electromagnetically induced transparency in radiatively and inhomogeneously broadened media

Contrary to popular belief, we demonstrate the feasibility of generating superluminal (and subluminal) probe (and signal) light via electromagnetically induced transparency in a medium comprising coupled double-ladder systems. This scheme can be realized in both homogeneously (radiative) as well as in inhomogeneously (Doppler) broadened atomic systems. Unlike more intricate earlier schemes, our scheme is based simply on steady-state propagation dynamics resulting from compensation of the inevitable absorption losses by large nonlinear gain generated through appropriate choice of the pump and coupling fields. We show how easily in this scheme the speed of weak probe (and signal) fields can be switched from subluminal to superluminal by simply varying the strengths of the coherent pump and coupling fields. Furthermore, it is shown that under these conditions both the signal and probe fields are intensity matched and both propagate with the same subluminal (or superluminal) group velocity without suffering loss or gain for long distance in the medium.     

Cavity plasmonics: large normal mode splitting of electric and magnetic particle plasmons induced by a photonic microcavity

We couple localized plasmon modes in nanowire pairs with resonator modes of a microcavity. Depending on the position of the nanowire pair in the resonator, the electric (symmetric) or magnetic (antisymmetric) plasmon mode is coupled, manifested by a huge anticrossing in the dispersion diagram. We explain this behavior by taking the symmetry and spatial distribution of the electric fields in the resonator into account. Experimental spectra verify the predicted mode-splitting due to the resonant coupling and agree well with theory. Our work can serve as a model system for far-field plasmon-plasmon coupling and paves the way toward enhanced localized plasmon-plasmon interaction in photonically coupled three-dimensional Bragg structures.     

Controlled in situ nanoscale enhancement of gold nanowire arrays with plasmonics

The controlled in situ growth of ordered gold nanoparticles and nanowire arrays has been studied by optically tracking changes in the local surface plasmon resonance (LSPR) spectrum. A spectrometer and custom-programmed analysis software track changes in the LSPR spectrum. The peak position, peak height (i.e. extinction intensity) and peak width (e.g. radius of curvature) were tracked over time to quantify the dynamic growth of gold as soon as the system was exposed to a commercial gold enhancement solution. This enables the controlled dynamic growth of nano-objects without the necessity of characterizing the growth and aggregation kinetics of the gold enhancement solution. The result was the successful enhancement of their electrically conductive and plasmonic properties, as well as the controlled growth and transformation of line-patterned nanoparticles into conductive particle-based nanowires.