Three-level Medium Research Articles

Optical microcavity formation and ultrafast control using half-cycle attosecond pulses in two- and three-level media

Light induced population difference gratings have numerous applications in modern optics. The conventional approach of creating them by using monochromatic laser radiation makes it virtually impossible to rapidly control their properties. In recent years, there has been active discussion about using ultra-short light pulses to control such gratings. We show the possibility of ultrafast control of population difference structures, such as dynamic microresonators and Bragg-like grating formations, by the collision of extremely short light pulses in a resonant medium. This work focuses on changes in microcavity properties based on the different parameters, such as the atomic density of the medium, the form of the pulses, and whether the medium is two- or three-level.

Electromagnetically induced gratings created by extremely short non-overlapping pulses of light in a three-level resonant medium

In a fixed spectral range, single- and half-cycle electromagnetic pulses have the shortest duration. Half-cycle pulses are promising tools for ultrafast control of quantum systems. Previously, the possibility of using a sequence of single- and half-cycle attosecond pulses to generate and ultrafast control light-induced population difference gratings has been demonstrated. However, such studies have been carried out using different approximations, such as the sudden perturbation theory and the two-level model for the resonant medium. In this paper, based on the numerical solution of constitutive equations for elements of the density matrix and wave equation it is shown that it is possible to generate and control population gratings in a three-level medium without using the approximation of sudden perturbations used in previous studies. It is shown that taking into account the additional level of the medium does not lead to a violation of the effect of generating such gratings. This extends the applicability of previous results.

Spatially Control of Quantum Entropy in a Three-level Medium

Spatially Control of Quantum Entropy in a Three-level Medium

Dynamical propagation and all-optical switching in a ladder-type three-level system under the influence of spontaneously generated coherence

We investigate the dynamical of pulse propagation and all-optical switching via a spontaneously generated coherence (SGC) in a three-level ladder-type atomic medium driven by a coupling field under the presence of incoherent pumping. Results show that the SGC causes modulations at the leading edge of the pulse envelope shape. These modulations increase with the together growth of SGC and distance. Furthermore, it is shown that the continuous-wave input probe field is switched ON or OFF by periodically modulating the coupling field. The spontaneously generated coherence has a strong effect on switching efficiency and switching pulse shape. The proposed scheme may have applications in the design of optical switching and optical gain devices in optical telecommunications.

Population density gratings creation and control in resonant medium by half-cycle terahertz pulses

Electromagnetically induced gratings (EIG) are created by standing-wave laser field in resonant media. Such gratings can be also created by few-cycle electromagnetic pulses counter-propagating in the medium via coherent Rabi oscillations of atomic inversion. In this case, instantaneous cross-section of the pulses in the medium is not necessary for grating formation. In this paper, we revise our recent results in study of such grating formation and their control by few-cycle pulses coherently propagating in a resonant medium. We demonstrate the grating formation and their control in three-level medium excited by three subcycle THz pulses.

Strongly Correlated States of Light and Repulsive Photons in Chiral Chains of Three-Level Quantum Emitters.

We study the correlated transport of photons through a chain of three-level emitters that are coupled chirally to a photonic mode of a waveguide. It is found that this system can transfer a weak classical input into a strongly correlated state of light in a unitary manner. Our analysis reveals two-photon scattering eigenstates, that are akin to Fano resonances or shape resonances in particle collisions and facilitate the emergence of antibunched light with long-range correlations upon crossing a critical length of the chain. By operating close to conditions of electromagnetically induced transparency of the three-level medium, a high degree of antibunching and photon transmission can be maintained in the presence of moderate losses. These features suggest a promising mechanism for single-photon generation and may open the door to exploring correlated quantum many-body states of light with repulsively interacting photons.

Генерация предельно коротких импульсов терагерцового излучения на основе сверхизлучения трехуровневой резонансной среды

The possibility of generating extremely short pulses of terahertz (THz) radiation due to superradiance - collective spontaneous emission of stopped polarization of a thin layer of a three-level resonant medium excited by a pair of attosecond (or femtosecond) pulses is studied theoretically. The source of a terahertz pulse is a pulse of stopped nonlinear polarization of the medium, which occurs in the interval between its excitation and de-excitation. The case of a three-level medium with equidistant energy levels (as in a quantum harmonic oscillator), the transition frequency of which lies in the THz range, is considered. The influence of the populations of the excited levels of the medium on the shape of the terahertz superradiance pulse is discussed.

Generation of an Attosecond Pulse Based on Collective Spontaneous Radiation Emission of a Layer of Three-Level Atoms Excited by a Pair of Unipolar Pulses

A method of coherent controlling the polarization of a medium has been proposed recently for the generation of extremely short pulses. The method is based on the excitation of atomic polarization oscillations and their subsequent stop using a pair of ultrashort pulses. The so-called stopped pulse of the polarization of a medium, which arises in the interval between its excitation and deexcitation, can be a source of an extremely short radiation pulse. In this work, the above-indicated possibility of generation of an isolated attosecond ultraviolet pulse in a three-level resonant medium whose parameters correspond to a hydrogen atom excited by a pair of unipolar X-ray pulses is considered theoretically. In this case, the generation mechanism is of the antenna-type, that is, it is caused by the collective spontaneous emission of pre-phased atoms in the absence of a noticeable decay of their free polarization.

Population Gratings Created by a Pair of Unipolar Attosecond Pulses in a Three-Level Atomic Medium

The possibility of inducing population gratings in a three-level resonant medium using a pair of unipolar attosecond pulses that do not overlap in the medium has been studied theoretically. It has been shown that the results of the approximate solution of the Schrodinger equation agree with the results of the numerical solution of the system of equations for the density matrix of a three-level medium whose parameters are close to the parameters of atomic vapors of rubidium.

Electromagnetically induced transparency (EIT) amplitude noise spectroscopy

Intensity noise cross-correlation of the polarization eigenstates of light emerging from an atomic vapor cell in the Hanle EIT configuration results in high resolution spectroscopy even with free-running semiconductor lasers. We show that the character of the observed intensity noise in any output polarization basis can be modeled as a Markov process in the input light fields’ amplitudes that excite the response of a three-level medium. This method has promise as an inexpensive and simpler approach to vector magnetometry and has applications in timekeeping and as a probe of dynamics of atomic coherence in warm vapor cells.

Селективное возбуждение и создание инверсной населенности в квантовых системах с помощью униполярных аттосекундных и терагерцовых импульсов

The possibility of selective population of the energy levels of quantum systems was studied using a single unipolar subcycle pulse and a pair of pulses. Selective population of quantum levels is clearly illustrated based on the numerical solution of the system of equations for the density matrix of a three-level medium interacting with a pair of subcycle attosecond and terahertz pulses. The possibility of creating an population inversion in a three-level medium is shown using a pair of such pulses. The dynamics of population density gratings in a three-level medium is studied at the impact on the system of a pair of large-amplitude Gaussian pulses. If in a weak field the shape of the gratings is harmonic, according to analytical calculations performed according to perturbation theory, then in in the case of a strong field, the spatial profile of the gratings can differ from the sinusoidal one and has complex spike structure.

Решетки населенностей, создаваемые парой униполярных аттосекундных импульсов в трехуровневой атомарной среде

The possibility of population gratings creation in a three-level resonant medium using a pair of unipolar attosecond pulses that do not overlap in the medium is studied theoretically. It is shown that the results of the approximate solution of the Schrödinger equation agree with the results of the numerical solution of the system of equations for the density matrix of a three-level medium, the parameters of which are close to the parameters of atomic vapors of rubidium.

Soliton Pair Propagation in Three-Level Unbalanced Medium

Soliton Pair Propagation in Three-Level Unbalanced Medium

Low-noise optical field phase-shifting manipulated using a coherently-prepared three-level atomic medium

We propose a multifunction phase-shifting manipulator with low noise at a single-photon level,by using a threelevel atomic scheme.This three-level system interacts with a strong pumping field and a weak probe field with a large detuning.Due to this large detuning,two lower states can be coherently prepared prior to the injection of the pump and probe fields.In our configuration,the duration of the pumping field is much longer than that of the probe field. By solving the Heisenberg-Langevin equations of our system under the steady state approximation,we calculate the linear susceptibility of the system and examine the quantum noise properties of the probe field in detail.We show that this scheme,which rests on the process of two-wave mixing with initial atomic coherence,exhibits many interesting properties that neither typical electromagnetically induced transparency (EIT) schemes nor active Raman gain (ARG) schemes possess.Although both EIT-and ARG-based schemes have been widely investigated in atomic medium,the direct generalizations of these schemes to the single/few photon limit prove to be more problematic.The low fidelity due to the significant probe-field attenuation in EIT medium and the large quantum noise due to the amplification of the probe field in an active Raman gain medium are the main obstacles that prohibit a high-fidelity,low-noise phase shifter from being realized in the single/few photon limit.Physically,this scheme can be viewed as a hybrid scheme in which two processes of different physical principles are allowed to interfere with each other to achieve many desired functionalities. For instance,it can be used as a lossless two-photon-broadband phase-shifter with suitable system parameters.It can also be used as an attenuator/amplifier and a total transparency with a zero phase shift.In particular,we show that by locking the pump field intensity and the two-photon detuning simultaneously a flat constant π-phase shift can be realized with unit probe fidelity in a broad probe field frequency range.Applying the quantum regression theorem,we calculate the noise spectrum of the outgoing probe field as a large phase shift is achieved,and show that this two-photon-insensitive π-phase shift may significantly reduce the quantum noise fluctuations associated with a Raman gain process,and have a lot of potential applications for quantum information processing and optical telecommunication.The realization of this broadband π-phase-shift with significantly reduced quantum noise fluctuations makes this scheme attractive for the realization of low-noise phase-gate/polarization-gate at single-photon level.

Linear distributed Bragg cavity effects on optical limiting in two- and three-level media

A lumped distributed Bragg reflector (DBR)-nonlinear layer-DBR system is used to explore how nonlinear optical effects (in particular, optical limiting) are modulated by the dispersive character of the (optically linear) DBR. A three-level quantum optics model of the nonlinear layer is used to find self-consistent numerical solutions to the (nonlinear) optical transport in the composite system. We find that the intensity dependence of the real part of the index can be combined with the dispersion in the (linear) DBR to cause optical limiting even for materials that have only a saturated absorber (two-level) response.

Coupling of a nanomechanical oscillator and an atomic three-level medium

We theoretically investigate the coupling of an ultracold three-level atomic gas and a nano-mechanical mirror via classical electromagnetic radiation. The radiation pressure on the mirror is modulated by absorption of a probe light field, caused by the atoms which are electromagnetically rendered nearly transparent, allowing the gas to affect the mirror. In turn, the mirror can affect the gas as its vibrations generate opto-mechanical sidebands in the control field. We show that the sidebands cause modulations of the probe intensity at the mirror frequency, which can be enhanced near atomic resonances. Through the radiation pressure from the probe beam onto the mirror, this results in resonant driving of the mirror. Controllable by the two photon detuning, the phase relation of the driving to the mirror motion decides upon amplification or damping of mirror vibrations. This permits direct phase locking of laser amplitude modulations to the motion of a nano-mechanical element opening a perspective for cavity-free cooling through coupling to an atomic gas.

Giant Goos–Hänchen shift via spontaneous generated coherence

The influence of spontaneous generated coherence (SGC) on the Goos–Hänchen (GH) shift in the reflected light is presented. A weak probe light is incident on a cavity containing three-level gaseous atomic medium consist of 85Rb atoms. The atom–field interaction follows electromagnetically induced transparency configuration, and the SGC modifies the dispersion and absorption properties of a system [Y. Niu and S. Gong, Phys. Rev. A 73, 053811 (2006)]. The SGC enhances the Kerr nonlinearity which leads to giant negative and positive GH shifts in the reflected light. Further, the control of negative and positive GH shifts is achieved via manipulation of probe field detuning.

Anisotropy-Induced Transparency in Optically Dense Media

The effect of anisotropy-induced transparency, which is analogous to electromagnetically induced transparency in the three-level medium located in a resonance field, is predicted and studied theoretically. This effect is connected with destructive interference between oscillations in different degrees of freedom of an anisotropic medium, which are connected with each other, as radiation propagates at an angle to one of the optical axes in a triaxial or uniaxial crystal. In this case, a hybrid-type polariton is formed in the “transparency window,” which combines the quasi-longitudinal polarization with the “vacuum” refractive index. Such a wave is excited easily by radiation incident from the vacuum and should have enhanced impedance of coupling with active or nonlinear elements, which can be useful for the creation of small-size optical systems. Due to the interest in quantum-optical effects displayed recently, the regime of anisotropy-induced transparency is considered within the framework of the quantum theory of radiation in an optically dense medium.

Pulse propagation, population transfer, and light storage in five-level media

We consider adiabatic interaction of five-level atomic systems and their media with four short laser pulses under the condition of all two-photon detunings being zero. We derive analytical expressions for eigenvalues of the system's Hamiltonian and determine conditions of adiabaticity for both the atom and the medium. We analyse, in detail, the system's behaviour when the eigenvalue with non-vanishing energy is realized. As distinct from the usual dark state of a five-level system (corresponding to zero eigenvalue), which is a superposition of three states, in our case the superposition of four states does work. This seemingly unfavourable case is nevertheless demonstrated to imitate completely a three-level system not only for a single atom but also in the medium, since the propagation equations are also split into those for three- and two-level media separately. We show that, under certain conditions, all the coherent effects observed in three-level media, such as population transfer, light slowing, light storage, and so on, may efficiently be realized in five-level media. This has an important advantage that the light storage can be performed twice in the same medium, i.e., the second pulse can be stored without retrieving the first one, and then the two pulses can be retrieved in any desired sequence.

Reversible storage of a weak light pulse optimized by spontaneously generated coherence

We investigate the storage and retrieval of a weak light pulse in a -type three-level atomic gas medium with spontaneously generated coherence and pumped by an incoherent field. The scheme works based on electromagnetically induced transparency and can promote retrieval efficiency. We show how to make the combination choice of the system parameters required not only for the perfect retrieval operation but also for the high atom-field coupling efficiency.