Electromagnetically Induced Transparency Medium Research Articles

Manipulation of single stored-photon with microwave field based on Rydberg polariton.

We demonstrate a coherent microwave manipulation of a single optical photon based on a single Rydberg excitation in an atomic ensemble. Due to the strong nonlinearities in a Rydberg blockade region, a single photon can be stored in the formation of Rydberg polariton using electromagnetically induced transparency (EIT). The manipulation of the stored single photon is performed by applying a microwave field that resonantly couples the nS1/2 and nP3/2, while the coherent readout is performed by mapping the excitation into a single photon. We achieve a single photon source with g(2)(0) = 0.29 ± 0.08 at 80S1/2 without applying microwave fields. By implementing the microwave field during the storage time and retrieval process, we show the Rabi oscillation and modulation of stored photons that can be controlled to retrieve early or late. Rapid modulation frequencies up to 50 MHz can be obtained. Our experimental observations can be well explained via numerical simulations based on an improved superatom model accounting for the dipole-dipole interactions in a Rydberg EIT medium. Our work provides a way to manipulate the stored photons by employing the microwave field, which is significant for developing quantum technologies.

Propagation of Gaussian vortex beams in electromagnetically induced transparency media.

Electromagnetically induced transparency (EIT) is an important phenomenon in quantum optics, and has a wide range of applications in the fields of quantum information processing and quantum precision metrology. Recently, with the rapid progress of the generation and detection of structured light, the EIT with structured light has attracted enormous interests and offers new and novel functionalities and applications. Here, we theoretically study the propagation and evolution of Gaussian vortex beams, a typical type of structured light, in an EIT medium with Λ-type three-level atoms. Based on the generalized Huygens-Fresnel principle, we derive the analytical expressions of fully and partially coherent Gaussian vortex beams propagating in the EIT medium, and study the evolution of the intensity and phase distributions of the beams and their dependencies on parameters such topological charge, coherence length, Rabi frequency, etc. It is shown that both the fully and partially coherent Gaussian vortex beams undergo focusing and diverging periodically during propagation. The phase singularity of the fully coherent beam keeps unchanged, while the phase singularity of the partially coherent beam experiences splitting and recombination periodically. In addition, new phase singularities with opposite topological charge are generated in the latter case. Our results not only advance the study of the interaction between structured light and coherent media, but also pave the avenue for manipulating structured light via EIT.

Theoretical study of coherent optical phenomena in a three lasers driven four-level ladder-type system involving a Rydberg state

A comparative theoretical study of two-photon electromagnetically induced transparency (EIT), absorption (EIA) and three-photon electromagnetically induced transparency (TPEIT), absorption (TPEIA) and their associated dispersion and group index profiles are presented by using a four-level ladder-type system of both stationary and moving 85Rb Rydberg atoms. We have observed EIT, EIA and their respective positive and negative dispersive slopes under two-photon conditions, while the TPEIT, TPEIA signals and the respective multiple positive and negative dispersive slopes at around zero detuning of the probe field are observed under the three-photon conditions. It is found that the control and manipulation of the coherent optical responses under three-photon conditions are much richer than the two-photon conditions. The group index profiles related to the dispersion of the medium have been studied under both two- and three-photon conditions to compare and explain the optical switching between the subluminal and superluminal modes of propagation for both stationary and moving atomic medium. The influence of the ‘pump’ Rabi frequency on the group index has also been investigated to illustrate the action of optical switching. Finally, the existence of the four-wave mixing (FWM) process due to the action of three optical fields in the EIT medium is also discussed.

Spin-orbit grating of light in coherent media

We explore the underlying spin-orbit coupling (SOC) mechanism for the interactions between complex structured light fields in a four-level tripod electromagnetically induced transparency (EIT) system. Because one coupling field in the system is a Bessel beam, the susceptibility of the EIT medium can be modulated quasiperiodically in the radial dimension. The paraxial propagation and evolution of a rotating spinor image as the probe field in the medium can be described by a Pauli-like equation with the SOC term. We calculate the spatial distributions of the diffracted patterns of the image in the near field and clearly show the tunable SOC-induced radial splitting of the oppositely polarized pseudospin states. Our scheme may be useful for all-optical processing of spatial multimode signals in coherent media.

A weakly-interacting many-body system of Rydberg polaritons based on electromagnetically induced transparency

The combination of Rydberg atoms and electromagnetically induced transparency (EIT) has been extensively studied in the strong-interaction regime. Here we proposed utilizing an EIT medium with a high optical depth (OD) and a Rydberg state of low principal quantum number to create a many-body system of Rydberg polaritons in the weak-interaction regime. The phase shift and attenuation induced by the dipole–dipole interaction (DDI) were still significant, and can be viewed as the consequences of elastic and inelastic collisions among Rydberg polaritons. We further observed that the width of the transverse momentum distribution of Rydberg polaritons at the exit of the system became notably smaller as compared with that at the entrance. The observation demonstrates the cooling effect in this system. The μs-long interaction time due to the high-OD EIT medium plus the μm2-size collision cross section due to the DDI suggests a feasible platform of polariton Bose–Einstein condensation.

Surface polaritonic solitons and breathers in a planar plasmonic waveguide structure via electromagnetically induced transparency

We propose a scheme for the coupler-free excitation of surface polaritonic solitons and breathers in a planar plasmonic waveguide structure comprising of a transparent layer, a metal layer and a layer of three-level lambda-type atomic medium. In the proposed system, an enhanced Kerr nonlinearity is achieved via electromagnetically induced transparency (EIT) in the bottom atomic medium, which can be controlled through proper modulation of the frequency detunings and Rabi frequencies of the driving laser fields. This nonlinearity balances the dispersion in the system, thus providing the necessary condition for the excitation of polaritonic solitons in the proposed system. As a result, the system yields laterally self-trapped bright and dark surface polaritonic solitons which are tightly guided at the interface of the metal and the EIT medium. Furthermore, we investigate the excitation of surface polaritonic Akhmediev breathers at the metal-EIT medium interface in the proposed system. A stable propagation of the surface polaritonic Akhmediev breathers is achieved with proper choice of parameters in the proposed planar plasmonic waveguide structure. This experimentally feasible scheme could be significant in the development of highly compact nano-photonic devices in the optical regime.

Interactions of cold Rydberg atoms and metallic surfaces

We theoretically propose that electromagnetically induced transparency (EIT) with cold Rydberg atoms in the proximity to a metallic chip surface can be applied to detect and investigate the Casimir–Polder effect. The absorption spectrum of the probe laser is numerically computed by the Monte Carlo method, taking into account atom-surface interactions (Casimir–Polder effect). The results show that the Casimir–Polder effect shifts the energy level of the Rydberg state and leads to a shift in the EIT transparency window. The shift of resonant frequency depends on the principal quantum number, atom-surface distance and atomic density. The atom-surface interactions have observable impacts on the nonlinear optic response of the ‘Rydberg EIT medium’ near atom chips.

Investigation of electromagnetically induced transparency in quantum dots by using second quantization formalism

In the present work by theoretically aspect with a control laser and cylindrical quantum dots, an EIT (Electromagnetically Induced Transparency) medium has been created for a probe laser. By considering atoms and photons as a many body system, the second quantization formalism has been selected to solve the problem. In this paper by using creation and annihilation operators in the fully quantum approach the effects of different parameters on the refractive index and absorption coefficient by using density matrix method have been investigated.

Formation of a Stationary Light Pulse in a Doppler-Broadened EIT Medium

A number of experiments have been performed on light slowing and stopping in the electromagnetically induced transparency (EIT) media of hot atomic gases where the Doppler-shift may add detunings to the field frequencies in an inhomogeneous fashion. We provide here a theoretical analysis as to the effect of such a Doppler-broadened environment on the dynamics of the system in comparison to a cold atomic medium. We will show that one of the most critical factors in the formation of a stationary light pulse is the enhancement of the excited-state decay rate caused by the collisions between the atoms of the medium and the molecules of the buffer gas.

Manipulating multi-frequency light in a five-level cascade EIT medium under Doppler broadening

An electromagnetically induced transparency (EIT) medium consisting of five-level-cascade atoms is proposed to control the group velocity of multi-frequency light under Doppler broadening. An analytic expression for the group index of probe light is derived as a function of the parameters of coupling light and temperature of the medium. It is shown that by adjusting intensity and/or frequency of the solely coupling light one may manipulate simultaneously group velocity of the probe light in three separated frequency regions, each of which enables to switch between the subluminal and superluminal modes. On the other hand, the effect of Doppler broadening increases the group velocity and enlarges the tuning range of the coupling intensity to switch between the superluminal and subluminal modes. The model is helpful to find applications related to the group velocity manipulation of multi-frequency light, and to serve future experimental studies at various temperature conditions.

Efficient images storage via modulating the atomic spin coherence in a N-type system

A four-level N-type cold atomic system is proposed for optimizing images storage based on the electromagnetically induced transparency (EIT). Both analytical analysis and numerical simulation clearly show that the application, during the storage time, of an additional intensity-modulated signal field and an additional microwave field can impose an intensity and a phase-dependent factors on the atomic spin coherence in a controlled manner, then the amplitude of the retrieved images can be increased or decreased with an enhancement in the visibility. Our results are very promising for the realization of all-optical information processing of images coherently stored in EIT media in the future.

Ultranarrow-bandwidth filter based on a thermal EIT medium

We present high-contrast electromagnetically-induced-transparency (EIT) spectra in a heated vapor cell of single isotope 87Rb atoms. The EIT spectrum has both high resonant transmission up to 67% and narrow linewidth of 1.1 MHz. We get rid of the possible amplification resulted from the effects of amplification without population inversion and four-wave mixing. Therefore, this high transmitted light is not artificial. The theoretical prediction of the probe transmission agrees well with the data and the experimental parameters can be derived reasonably from the model. Such narrow and high-contrast spectral profile can be employed as a high precision bandpass filter, which provides a significant advantage in terms of stability and tunability. The central frequency tuning range of the filter is larger than 100 MHz with out-of-band blocking ≥15 dB. This bandpass filter can effectively produce light fields with subnatural linewidth. Nonlinearity associating with the narrow-linewidth and high-contrast EIT profile can be very useful in the applications utilizing the EIT effect.

Storage and retrieval of electromagnetic waves using electromagnetically induced transparency in a nonlinear metamaterial

We investigate the storage and retrieval of electromagnetic waves using a nonlinear metamaterial, analogous to the electromagnetically induced transparency (EIT) observed in atomic systems. We experimentally demonstrate the storage of the electromagnetic wave by reducing an auxiliary “control” wave; the stored wave is then released by recovering the control wave. We also confirm that the metamaterial can store and reproduce the phase distribution of the original input wave. These effects confirm a remarkable analogy between the metamaterial and an atomic EIT medium.

Controlling the sing and magnitude of Kerr nonlinearity in four-level N-type EIT medium

Third-order nonlinear susceptibility in a four-level system with N-type configuration is studied by applying the electromagnetically induced transparency (EIT). The system is irradiated with a weak probe and two strong coupling fields. Behaviour of real (Kerr nonlinearity) and imaginary parts of third-order susceptibility and linear absorption spectrum of probe field is investigated with coupling field intensity and its frequency detuning. Results are shown that, the sign of both imaginary and real parts of third-order nonlinear susceptibility in one of Kerr peaks, changes from positive to negative with increasing the coupling field intensity. The EIT windows are not sensitive for intensity but extend for negative and shortened for positive detuning's. Furthermore, the magnitude of Kerr and nonlinear absorption (or gain) peaks efficiently modify with increasing the intensity. This can be important in practical applications such as lasing without inversion, subluminal and superluminal propagation and optical limiting effect based on self-focusing or self-defocusing process.

Controlling of dark or bright soliton type in a cascade-type electromagnetically induced transparency semiconductor quantum well by the coupling longitudinal optical phonons

In the past few years, with developing the technology of electromagnetically induced transparency (EIT) and improving the semiconductor technology, it has become possible to realize the application of optical soliton to communication device. Studies show the reduction of group velocity of the optical soliton in EIT medium under weak driving condition, which possibly realizes the storing of optical pulses in information storage. More importantly, semiconductor quantum wells have the inherent advantages such as large electric dipole moments of the transitions, high nonlinear optical coefficients, small size, easily operating and integrating. So it is considered to be the most potential EIT medium to realize the application of quantum devices. The optical soliton behavior in the semiconductor quantum well is studied, which can provide a certain reference value for the practical application of information transmission and processing together quantum devices. Although there has been a series of researches on both linear and nonlinear optical properties in semiconductor quantum wells structures, few publications report the effects of the cross-coupling longitude-optical phonon (CCLOP) relaxation on its linear and nonlinear optical properties. However, to our knowledge, the electron-longitude-optical phonon scattering rate can be realized experimentally by varying the sub-picosecond range to the order of a picosecond. According to this, we in the paper study the effects of the CCLOP relaxation on its linear and nonlinear optical properties in a cascade-type three-level EIT semiconductor quantum well. According to the current experimental conditions, we first propose a cascade-type three-level EIT semiconductor quantum well model. And in this model we consider the longitudinal optical phonons coupling between the bond state and anti-bond state. Subsequently, by using the multiple-scale method, we analytically study the dynamical properties of solitons in the cascade-type three-level EIT semiconductor quantum well with the CCRLOP. It is shown that when the CCRLOP strength is smaller, there exhibits the dark soliton in the EIT semiconductor quantum well. Only if the strength of the CCRLOP is larger, will in the system there exists bright soliton. That is to say, with increasing the strength of the CCRLOP, the soliton type of the system is converted from dark to bright soliton little by little. So, the temporal soliton type can be effectively controlled by the strength of the CCRLOP. In addition, we also find that the group velocity of the soliton can also be controlled by the strength of CCRLOP and the control light. These results may provide a theoretical basis for manipulating experimentally the dynamics of soliton in semiconductor quantum wells.

Controlling Optical Bistability in a Five-level Cascade EIT Medium

Optical bistability (OB) of an electromagnetically induced transparency (EIT) medium placed in a conventional unidirectional ring cavity is investigated numerically. The medium is excited by a coupling and probe laser lights via a five-level cascade scheme. It is shown that optical bistabe states with controllable switching threshold intensities and width are established simultaneously in three spectral regions corresponding to EIT windows. The current numerical result is compared to a previous analytical result showing influence of coherence terms neglected in the analytical model.

Coherent control of group index and magneto-optical anisotropy in a multilevel atomic vapor.

We study electromagnetically induced transparency (EIT) in a heated potassium vapor cell, using a simple optical setup with a single free-running diode laser and an acousto-optic modulator. Despite the fact that the Doppler width is comparable to the ground state hyperfine splitting, transparency windows with deeply sub-natural line widths and large group indices are obtained. A longitudinal magnetic field is used to split the EIT feature and induce magneto-optical anisotropy. Using the beat note between co-propagating coupling and probe beams, we perform a heterodyne measurement of the circular dichroism (and therefore birefringence) of the EIT medium. The observed spectra reveal that lin‖lin polarizations lead to greater anisotropy than lin⊥lin. A simplified ‖analytical model encompassing sixteen Zeeman states and eighteen Λ subsytems reproduces the experimental observations.

Optical bistability in a five-level cascade EIT medium: an analytical approach

We propose an optical bistability (OB) model consisting of a five-level cascade electromagnetically induced transparency (EIT) medium placed in a unidirectional ring cavity. An input-output intensity relationship for a weak probe light field is derived as a function of parameters of a strong coupling light and cooperation C. The OB behaviors of the system are investigated with variation of the parameters. It has been shown that the OB behaviors occur simultaneously in three EIT windows. Furthermore, switching thresholds and the hysteresis loop can be controlled by the parameters of the coupling light and/or a cooperation of atomic medium. Such controllable OB behaviors can find interesting applications in bistable photonic devices working at low light intensity and multiple frequencies.

Electromagnetically induced transparency in a five-level cascade system under Doppler broadening: an analytical approach

We develop an analytical approach on electromagnetically induced transparency (EIT) in a Doppler broadened medium consisting of five-level cascade systems excited by a strong coupling and weak probe laser fields. In a weak field limit of the probe light, EIT spectrum is interpreted as functions of controllable parameters of the coupling light and temperature of the medium. The theoretical interpretation of EIT spectrum is applied to the case of 85Rb atoms and compared with available experimental observation. Such an analytical interpretation provides quantitative parameters to control properties of the Doppler broadened EIT medium, and it is useful to find related applications.

Quantum theory for pulse propagation in electromagnetically-induced-transparency media beyond the adiabatic approximation

Beyond the adiabatic approximation, we develop a quantum theory for optical probe pulses propagating in electromagnetically-induced-transparency (EIT) media by including Langevin noise operators and asking the field operator to satisfy bosonic commutation relation. Influences on the degradation of quantum noise squeezing from optical depth of atomic ensemble, strength of control field, and ground-state decoherence are studied in the slow light, as well as storage and retrieval, for a squeezed probe pulse. Moreover, to give guidelines for realization of quantum interfaces based on EIT media, we demonstrate that the quantum squeezing of output probe pulses could be preserved with a stronger classical control field.