Controllable Hartman effect by vortex beam in a one dimensional photonic crystal doped by graphene quantum dots.

The Hartman effect is studied in a one dimensional photonic crystal doped with graphene quantum dots. It is shown that the Hartman effect can be switched from negative to positive by increasing the Rabi-frequency of the controlling field and also by manipulating the relative phase of the applied fields. The effect of the vortex beam on the Hartman effect is also presented. We show that the orbital angular momentum (OAM) and the azimuthal phase of the vortex beam do not affect the probe filed transmission while they change the Hartman effect from positive to negative.

Polarized induced phase grating in a quantized four-level graphene monolayer system.

We discuss the electromagnetically induced grating (EIG) and electromagnetically induced phase grating (EIPG) in a four-level quantized graphene monolayer system. By using the density matrix technique and perturbation theory, we first obtain the self-Kerr nonlinear susceptibility of the graphene system; afterwards, we study the amplitude and phase modulations of the probe light. We discovered that the EIG and EIPG can be found by controlling the elliptically polarized coupling fields that interact with the monolayer graphene system. Owing to the phase modulation of the transmitted light beam, we recognized that the probe strength can also additionally switch from zeroth-order to high-order diffraction. Moreover, we found that the diffraction performance of the grating may be adjusted through tuning the polarization of the coupling light.

Controllable atom-photon entanglement via quantum interference near plasmonic nanostructure.

A five-level atomic system is proposed in vicinity of a two-dimensional (2D) plasmonic nanostructure with application in atom-photon entanglement. The behavior of the atom-photon entanglement is discussed with and without a control laser field. The amount of atom-photon entanglement is controlled by the quantum interference created by the plasmonic nanostructure. Thus, the degree of atom-photon entanglement is affected by the atomic distance from the plasmonic nanostructure. In the presence of a control field, maximum entanglement between the atom and its spontaneous emission field is observed.

Azimuthal modulation of electromagnetically induced grating using structured light.

We propose a theoretical scheme for creating a two-dimensional Electromagnetically Induced Grating in a three-level [Formula: see text]-type atomic system interacting with a weak probe field and two simultaneous position-dependent coupling fields-a two dimensional standing wave and an optical vortex beam. Upon derivation of the Maxwell wave equation, describing the dynamic response of the probe light in the atomic medium, we perform numerical calculations of the amplitude, phase modulations and Fraunhofer diffraction pattern of the probe field under different system parameters. We show that due to the azimuthal modulation of the Laguerre-Gaussian field, a two-dimensional asymmetric grating is observed, giving an increase of the zeroth and high orders of diffraction, thus transferring the probe energy to the high orders of direction. The asymmetry is especially seen in the case of combining a resonant probe with an off-resonant standing wave coupling and optical vortex fields. Unlike in previously reported asymmetric diffraction gratings for PT symmetric structures, the parity time symmetric structure is not necessary for the asymmetric diffraction grating presented here. The asymmetry is due to the constructive and destructive interference between the amplitude and phase modulations of the grating system, resulting in complete blocking of the diffracted photons at negative or positive angles, due to the coupling of the vortex beam. A detailed analysis of the probe field energy transfer to different orders of diffraction in the case of off-resonant standing wave coupling field proves the possibility of direct control over the performance of the grating.

Strongly confined atomic localization by Rydberg coherent population trapping.

We investigate the possibility to attain strongly confined atomic localization using interacting Rydberg atoms in a coherent population trapping ladder configuration, where a standing-wave is used as a coupling field in the second leg of the ladder. Depending on the degree of compensation for the Rydberg level energy shift induced by the van der Waals interaction, by the coupling field detuning, we distinguish between two antiblockade regimes, i.e., a partial antiblockade (PA) and a full antiblockade. While a periodic pattern of tightly localized regions can be achieved for both regimes, the PA allows much faster convergence of spatial confinement, yielding a high-resolution Rydberg state-selective superlocalization regime for higher-lying Rydberg levels. In comparison, for lower-lying Rydberg levels, the PA leads to an anomalous change of spectra linewidth, confirming the importance of using a stable uppermost state to achieve a superlocalization regime.

Optically induced diffraction gratings based on periodic modulation of linear and nonlinear effects for atom-light coupling quantum systems near plasmonic nanostructures.

We investigate the quantum linear and nonlinear effects in a novel five-level quantum system placed near a plasmonic nanostructure. Such a quantum scheme contains a double-V-type subsystem interacting with a weak probe field. The double-V-subsystem is then coupled to an excited state by a strong coupling field, which can be a position-dependent standing-wave field. We start by analyzing the first-order linear as well as the third and fifth order nonlinear terms of the probe susceptibility by systematically solving the equations for the matter-fields. When the quantum system is near the plasmonic nanostructure, the coherent control of linear and nonlinear susceptibilities becomes inevitable, leading to vanishing absorption effects and enhancing the nonlinearities. We also show that when the coupling light involves a standing-wave pattern, the periodic modulation of linear and nonlinear spectra results in an efficient scheme for the electromagnetically induced grating (EIG). In particular, the diffraction efficiency is influenced by changing the distance between the quantum system and plasmonic nanostructure. The proposed scheme may find potential applications in future nanoscale photonic devices.

Tunneling induced two-dimensional phase grating in a quantum well nanostructure via third and fifth orders of susceptibility.

We study the nonlinear optical properties in an asymmetric double AlGaAs/GaAs quantum well nanostructure by using an external control field and resonant tunneling effects. It is found that the resonant tunneling can modulate the third-order and fifth-order of susceptibilities via detuning frequency of coupling light. In presence of the resonant tunneling and when the coupling light is in resonance with the corresponding transition, the real parts of third-order and fifth-order susceptibilities are enhanced which are accompanied by nonlinear absorption. However, in off-resonance of coupling light, real parts of third-order and fifth-order susceptibilities enhance while the nonlinear absorption vanishes. We investigate also the two-dimensional electromagnetically induced grating (2D-EIG) of the weak probe light by modulating the third-order and fifth-order susceptibilities. In resonance of coupling light, both amplitude and phase grating are formed in the medium due to enhancement of third-order and fifth-order probe absorption and dispersion. When the coupling light is out of resonance, most of probe energy is transferred from zero-order to higher-order directions due to resonant tunneling effect. The efficiency of phase grating for third-order of susceptibility is higher than phase grating for fifth-order susceptibility. Our proposed model may be useful for optical switching and optical sensors based on semiconductor nanostructures.

Enhancement of Goos-Hänchen shift due to a Rydberg state.

This paper hints at the Goos-Hänchen shift properties of a cavity containing an ensemble of atoms using a four-level atomic system involving a Rydberg state. By means of the stationary phase theory and density matrix formalism in quantum optics, we study theoretically the Goos-Hänchen shifts in both reflected and transmitted light beams. It is realized that as a result of the interaction between Rydberg and excited states in such a four-level atom-light coupling scheme the maximum positive and negative Goos-Hänchen shifts can be obtained in reflected and transmitted light beams owning to the effect of the Rydberg electromagnetically induced transparency (EIT) or Rydberg electromagnetically induced absorption. In particular, when the switching field is absent and the Rydberg EIT is dominant in the medium, a giant Goos-Hänchen shift can be achieved for both reflected and transmitted light beams.

Goos-Hänchen shifts due to spin-orbit coupling in the carbon nanotube quantum dot nanostructures.

The properties of Goos-Hänchen (GH) shifts for transmitted and reflected light pulses in a cavity with an intracavity medium consist of carbon nanotube quantum dot nanostructures, which have been discussed theoretically by using the stationary phase theory. Our findings show that due to the presence of spin-orbit coupling, the maximum negative and positive shifts can be realized by modifying the absorption and dispersion properties of the intracavity medium. Moreover, the effect of the transverse magnetic field has been also considered as a new parameter for controlling the GH shifts in reflected and transmitted light beams. We hope that our proposed structure may be suitable for the generation of future all-optical system devices based on carbon nanotube quantum dot nanostructures.

All-optical switching between optical bistability and multistability in a defect dielectric medium doped with a multiple quantum well nanostructure.

In this paper, optical bistability (OB) and multistability (OM) properties of a defect dielectric slab are studied. A GsAs multiple quantum well nanostructure (MQW) with 17.5 nm GaAs wells and 15 nm Al(0.3) Ga(0.7) barriers is used in the dielectric medium as a defect layer. Therefore, properties of the refractive index of the slab can be changed in the presence of MQWs. It is observed that switching from OB to OM can be obtained by controlling some external parameters. We find that the exciton spin relaxation and thickness of the slab have essential roles in adjusting the OB and OM properties of the probe light through the slab. Moreover, transmission, reflection, and absorption properties of the propagating pulse through the slab are also discussed. We show that the subluminal and superluminal light transmission or reflection can be obtained via amplification of the probe pulse through the medium. We hope that our proposed model may be suitable for the development of nanoscale devices in all-optical quantum information technology.

Phase control of light transmission and reflection based biexciton coherence in a defect dielectric medium.

Phase control of two weak probe lights' transmission and reflection based biexciton coherence in a defect dielectric medium doped by four-level GaAs/AlGaAs multiple quantum wells with 15 periods of 17.5 nm GaAs wells and 15 nm Al0.3Ga0.7As barriers is theoretically investigated. The biexciton coherence in this scheme is set up by two continuous wave control fields that couple to a resonance of biexcitons. It is shown that the transmission and reflection properties versus relative phase between applied fields can be controlled by the intensity of control fields and exciton spin relaxation between exciton states. Our studies show that many-particle interactions due to Coulomb correlations in semiconductors can be harnessed by quantum coherence in an interacting many-particle system.