Electromagnetically induced transparency and electromagnetically induced absorption in Y-type system

The propagation of a probe field through a four-level Y-type atomic system is described in the presence of two additional coherent radiation fields, namely, the control field and the coupling field. An expression for the probe response is derived analytically from the optical Bloch equations under steady state condition to study the absorptive properties of the system under probe field propagation through an ensemble of stationary atoms as well as in a Doppler broadened atomic vapor medium. The most striking result is the conversion of electromagnetically induced transparency(EIT) into electromagnetically induced absorption(EIA) as we start switching from weak probe regime to strong probe regime. The dependence of this conversion on residual Doppler averaging due to wavelength mismatch is also shown by choosing the coupling transition as a Rydberg transition.     

Frequency‐sensitive switching control effect induced by two‐photon resonance in an EIT‐based layered medium

The optical response of an atomic vapor can be coherently manipulated by tunable quantum interference occurring in atomic transition processes. A periodic layered medium whose unit cells consist of a dielectric and an EIT (electromagnetically induced transparency) atomic vapor is designed for light propagation manipulation. Such an EIT‐based periodic layered medium exhibits a flexible frequency‐sensitive optical response, where a very small change in probe frequency can lead to a drastic variation of reflectance and transmittance. As the destructive quantum interference relevant to two‐photon resonance arises in EIT atoms interacting with both control and probe fields, the controllable optical processes that depend sensitively on the external control field will take place in this EIT‐based periodic layered medium. Such a frequency‐sensitive and field‐controlled optical behavior of reflection and transmission in the EIT photonic crystal can be applicable to designs of new devices such as photonic switches, photonic logic gates and photonic transistors, where one laser field can be controlled by the other one, and would have potential applications in the areas of integrated optical circuits and other related techniques (e.g., all‐optical instrumentations).     

Simultaneous electromagnetically induced transparency and absorption in thermal atomic medium

A three-level lambda system driven by multicolor control, pump, and probe fields is investigated. The pump and probe fields are derived from the same laser with opposite propagating directions. Due to the Doppler effect, the zero group-velocity atoms face bichromatic fields, while other atoms face trichromatic fields. The atomic medium shows distinct characteristics and exhibits simultaneous electromagnetically induced transparency(EIT) and electromagnetically induced absorption(EIA) at two frequencies. EIT and EIA peaks have a fixed relationship with frequency, which is determined by the Doppler shifts.     

Study of radiofrequency radiation by means of optical effect of electromagnetically induced transparency

We propose a method of all-optical investigation of radiofrequency (RF) radiation based on the coherent effect of electromagnetically induced transparency (EIT). It is shown that if the atomic coherence is perturbed by an RF field, the shape of probe pulse propagating in a three-level ??-type atomic medium under EIT conditions is modified correspondingly to the temporal structure of the RF pulse. The effect is sensitive to the parameters of the pulse which enables measuring the intensity and the spectrum of the RF pulse. The method can be used for storage and lossless transfer of RF information over long distances using optical pulses.     

Controllable beating signal using stored light pulse

We experimentally study the controllable generation of a beating signal using stored light pulses based on electromagnetically induced transparency(EIT) in a solid medium. The beating signal relies on an asymmetric procedure of light storage and retrieval. After storing the probe pulse into the spin coherence under the EIT condition, two-color control fields with opposite detunings instead of the initial control field are used to scatter the stored spin coherence. The controllable beating signal is generated due to alternative constructive and destructive interferences in the retrieved signal intensities. The beating of the two-color control fields is mapped into the beating of weak probe fields by using atomic spin coherence. This beating signal will be important in precise atomic spectroscopy and fast quantum limited measurements.     

Absorption-Dispersion Properties in a Four-Level Atomic System with Vacuum-Induced Coherence

We discuss and analyze absorption-dispersion response for the probe field in a typical four-level atomic system with vacuum-induced coherence (VIC) arising from the cross coupling pathways associated with a pair of upper excited hyperfine levels. We find that VIC effect can preserve electromagnetically induced transparency (EIT) by using the detailed numerical simulations based on the density-matrix equations and analytical calculations in the dressed-state picture. We also show that the atomic hyperfine structure cannot be a hindrance to obtaining EIT.     

Absorption-Dispersion Properties in a Four-Level Atomic System with Vacuum-Induced Coherence

We discuss and analyze absorption-dispersion response for the probe field in a typical four-level atomic system with vacuum-induced coherence (VIC) arising from the cross coupling pathways associated with a pair of upper excited hyperfine levels. We find that VIC effect can preserve electromagnetically induced transparency (FIT) by using the detailed numerical simulations based on the density-matrix equations and analytical calculations in the dressed-state picture. We also show that the atomic hyperfine structure cannot be a hindrance to obtaining EIT.     

Nonlinear cascade-configuration multi-wave mixing scheme based on electromagnetically induced transparency

A nonlinear optical cascade-configuration multi-wave mixing (CCMWM) scheme is presented and analysed for the generation of coherent light in a six-level atomic system in the context of electromagnetically induced transparency (EIT). A detailed semi-classical study of the propagation of the generated mixing and probe fields is demonstrated. We show by numerical simulations that EIT is capable of suppressing linear and nonlinear photon absorption. The analytical dependence of the generated mixing field on the probe field and the respective detuning is also predicted. Such a nonlinear optical process can be used for generating coherent short-wavelength radiation.     

Electromagnetically induced transparency-like effect in the degenerate triple-resonant optical parametric amplifier

We investigate experimentally the absorptive and dispersive properties of the triple-resonant optical parametric amplifier (OPA) for the degenerate subharmonic field. In the experiment the subharmonic field is utilized as the probe field and the harmonic wave as the pump field. We demonstrate that the electromagnetically induced transparency (EIT)-like effect can be simulated in the triple-resonant OPA when the cavity linewidth for the harmonic wave is narrower than that for the subharmonic field. However, this phenomenon cannot be observed in a double-resonant OPA. The narrow transparency window appears in the reflected field. Especially in the measured dispersive spectra of the triple-resonant OPA, a very steep variation of the dispersive profile of the subharmonic field is observed, which can result in a slow light as that observed in an atomic EIT medium.     

Electromagnetically Induced Transparency in a Four-Level Atomic System

In this paper, we analyze and discuss the absorption properties of the probe beam in a four-level atomic system with a nearly hyper-fine doublet structure of two higher-lying excited levels based on electromagnetieally induced transparency (EIT) for the two cases of transient process and steady-state process. The main gain of this work is to investigate theoretically the influence of the nearly hyper-fine levels on the probe absorption. For the transient process, using the numerical calculations by a simple Mathematica code we find that the magnitude of the probe absorption at the line center is small compared to the typical three-level atomic system in the context of electromagnetieally induced transparency. For the case of the steady state, our results show that the probe absorption can be completely eliminated at the line center of the probe transition just as the usual three-level EIT scheme.     

Electromagnetically Induced Transparency in a Four-Level Atomic System

In this paper, we analyze and discuss the absorption properties of the probe beam in a four-level atomic system with a nearly hyper-fine doublet structure of two higher-lying excited levels based on electromagnetically induced transparency (EIT) for the two cases of transient process and steady-state process. The main gain of this work is to investigate theoretically the influence of the nearly hyper-fine levels on the probe absorption. For the transient process,using the numerical calculations by a simple Mathematica code we find that the magnitude of the probe absorption at the line center is small compared to the typical three-level atomic system in the context of electromagnetically induced transparency. For the case of the steady state, our results show that the probe absorption can be completely eliminated at the line center of the probe transition just as the usual three-level EIT scheme.     

Observation of V-type electromagnetically induced transparency and optical switch in cold Cs atoms by using nanofiber optical lattice

Optical nanofiber (ONF) is a special tool to achieve the interaction between light and matter with ultralow power. In this paper, we demonstrate V-type electromagnetically induced transparency (EIT) in cold atoms trapped by an ONF-based two-color optical lattice. At an optical depth of 7.35, 90% transmission can be achieved by only 7.7 pW coupling power. The EIT peak and linewidth are investigated as a function of the coupling optical power. By modulating the pW-level control beam of the ONF-EIT system in sequence, we further achieve efficient and high contrast control of the probe transmission, as well as its potential application in the field of quantum communication and quantum information science by using one-dimensional atomic chains.     

Observations of Autler-Townes spatial splitting of four-wave mixing image

We report the self- and external-dressed Autler-Townes (A-T) splittings of the images of the generated four-wave mixing signal (FWM) and electromagnetically induced transparency (EIT) of probe images in cascade three-level atomic system. Such spatial properties of probe and FWM signals are induced by the enhanced cross-Kerr nonlinearity. We demonstrate the controlled electromagnetically induced spatial dispersion (EISD), splitting and focusing of probe and FWM signals images by adjusting self- and external-dressing fields. Studies on such controllable A-T spatial splitting and spatial EIT effect can be very useful in applications of spatial signal processing and optical communication.     

Manipulating light flow with one-dimensional photonic crystals of an electromagnetically induced transparency medium

The band structures and equifrequency contours of one-dimensional photonic crystals (PCs), which consist of an electromagnetically induced transparency (EIT) medium and a common dielectric medium, can be dramatically changed by tuning the coupling field intensity (or coupling Rabi frequency, CRF) of the EIT medium. It is found that for a probe light at a fixed frequency, either positive or negative refraction in the EIT PC can be realized with a proper CRF. The behavior of a Gaussian beam (probe light) obliquely incident on such an EIT PC slab is simulated numerically. The probe light beam transmitted from the slab can be shifted transversely in a large range, and negative refraction enhances this effect. The present scenario can be applied in some areas such as quantum optical and photonic device designs.     

Enhanced Deflection of Light Ray by Atomic Ensemble on Coherent Population Oscillation

In recent experiments [e.g., Nature Physics 2 (2006) 332], the enhancedlight deflection in an atomic ensemble due to inhomogeneous fields is demonstrated by the electromagnetically induced transparency (EIT) based mechanism. In this paper, we explore a different mechanism for the similar phenomenon of the enhanced light deflection. This mechanism is based on the coherent population oscillation, which leads to the hole burning in the absorption spectrum. The medium causing the deflection of probe light is an ensemble of two-level atoms manipulated by a strong controlled field on the two photon resonances. In the large detuning condition, the response of the medium to the pump field and signal field is obtained with steady state approximation. And it is found that after the probe field travels across the medium, the signal ray bends due to the spatial-dependent profile of thecontrol beam.     

Theoretical Investigation of Light Transmission in a Slab Cavity via Kerr Nonlinearity of Carbon Nanotube Quantum Dot Nanostructure

In this paper, we discuss the transmission properties of weak probe laser field propagate through slab cavity with defect layer of carbon-nanotube quantum dot (CNT-QD) nanostructure. We show that due to spin-orbit coupling, the double electromagnetically induced transparency (EIT) windows appear and the giant Kerr nonlinearity of the intracavity medium can lead to manipulating of transmission coefficient of weak probe light. The thickness effect of defect layer medium has also been analyzed on transmission properties of probe laser field. Our proposed model may be useful for integrated photonics devices based on CNT-QD for applications in all-optical systems which require multiple EIT effect.     

电磁感应透明介质中非线性法拉第偏转

利用多重尺度法,解析地研究了V型五能级超冷原子电磁感应透明介质中弱的线偏振探测光的传播特性. 结果表明,仅考虑系统的线性效应,随着耦合光强度的增加,介质对探测光的吸收迅速减少,而探测光的传播速度逐渐增加,但比真空中的光速要低若干个数量级. 同时发现,在相同的外加磁场下探测光的非线性法拉第偏转方向与线性法拉第偏转相反,且偏转角更大. 这说明电磁感应透明介质中探测光的法拉第偏转主要是由系统的非线性效应调控. 关键词： 电磁感应透明 非线性法拉第偏转     

Spatial weak-light solitons in an electromagnetically induced nonlinear waveguide

We show that a weak probe light beam can form spatial solitons in an electromagnetically induced transparency (EIT) medium composed of four-level atoms and a coupling light field. We find that the coupling light beam can induce a highly controllable nonlinear waveguide and exert very strong effects on the dynamical behavior of the solitons. Hence, in the EIT medium, it is not only possible to produce spatial solitons at very low light intensities but also simultaneously control these solitons by using the coupling-light-induced nonlinear waveguide.     

Absorptive reduction and width narrowing in Λ-type atoms confined between two dielectric walls

This paper investigates the absorptive reduction and the width narrowing of electromagnetically induced transparency （EIT） in a thin vapour film of A-type atoms confined between two dielectric walls whose thickness is comparable with the wavelength of the probe field. The absorptive lines of the weak probe field exhibit strong reductions and very narrow EIT dips, which mainly results from the velocity slow-down effects and transient behaviour of atoms in a confined system. It is also shown that the lines are modified by the strength of the coupling field and the ratio of L/λ, with L the film thickness and λthe wavelength of the probe field. A simple robust recipe for EIT in a thin medium is achievable in experiment.     

Absorption spectroscopy of cold caesium atoms confined in a magneto-optical trap

Absorption spectra of cold caesium atoms confined in a magneto-optical trap are measured around D_2 line at 852nm with a weak probe beam. Absorption reduction dip due to electromagnetically induced transparency (EIT) effect induced by the cooling/trapping field in a V-type three-level system and a gain peak near the cycling transition are clearly observed. Several mechanisms mixed with EIT effect in a normal V-type three-level system are briefly discussed. A simple theoretical analysis based on a dressed-state model is presented for interpretation of the absorption spectra.