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.

Narrow-band transmission filter based on 1D-PCs with a defect layer.

A narrow-band transmission filter based on one-dimensional photonic crystals with SiO2/titaniumdioxide(TiO2) layers is grown by sol-gel spin-coating processing. The structural and optical properties of fabricated samples are characterized by an atomic force microscope, scanning electron microscope, and UV-visible spectroscopy. Specific wavelength transmission and bandgap in the optical filter with and without a defect layer have been investigated by engineering the layer thickness and defect layer material. For three fabricated optical filters, it is found that the maximum transmission for the TiO2 and InP defect layers reaches 58.09% and 42.21%, respectively. The layer thickness is fixed just by tuning the rotational speed of the spin-coater.

Spatial-dependent quantum dot-photon entanglement via tunneling effect.

Utilizing the vortex beams, we investigate the entanglement between the triple-quantum dot molecule and its spontaneous emission field. We present the spatially dependent quantum dot-photon entanglement created by Laguerre-Gaussian (LG) fields. The degree of position-dependent entanglement (DEM) is controlled by the angular momentum of the LG light and the quantum tunneling effect created by the gate voltage. Various spatial-dependent entanglement distribution is reached just by the magnitude and the sign of the orbital angular momentum (OAM) of the optical vortex beam.

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.

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.

High sensitive label-free optical sensor based on Goos-Hänchen effect by the single chirped laser pulse.

We consider a four-level molecular system with two ground-state vibrational levels and two excited-state vibrational levels inside a constant cavity configuration. We discuss the reflected and transmitted Goos-Hänchen (GH) shifts of a positive and negative single-chirped laser pulse. The impacts of the laser field detuning, intensity of applied laser field, and appropriately tuning the chirp rate on GH shifts are then analyzed. It is also found that this sensor is very sensitive to the refractive index of the intracavity medium, which can coherently be controlled by the medium parameters. The results show that such a sensor can be most effective for detecting biological molecules with low concentration than the large number density, where a bit variation in the concentration of sample will lead to a great variation on the GH shifts.

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.

Tunable optical and magneto-optical Faraday and Kerr rotations in a dielectric slab doped with double-V type atoms.

We theoretically investigate the optical and magneto-optical Faraday and Kerr rotations of a probe field that propagates through a nonmagnetic dielectric slab doped with double-V type atoms. Both rotations and corresponding ellipticities, as well as the intensities of transmitted and reflected beams, are modified by quantum coherence induced in the atomic system. We show that applying a control laser field makes the system optically active and simultaneously, transparent to one component of the probe field. We demonstrate that the response of the slab can be modified both electrically and magnetically. Applying the second control laser field with different Rabi frequencies improves the optical properties of the slab due to the induced coherent effects. We present analytical expressions for facilitating the detailed study of the system behaviors. Magneto-optical Faraday rotation 45° with transmission close to [Formula: see text] and large Kerr rotation with high reflection are significant results from the influence of both the control and magnetic fields on such a small structure. By prevailing over the tradeoff between reflection and rotation, the proposed model could be considered as a special candidate for rotating the polarization plane of the transmitted and reflected beams, simultaneously.

Innovative fiber Bragg grating filter based on a graphene photonic crystal microcavity.

We propose a new model for a fiber Bragg grating (FBG) filter based on one-dimensional defective photonic bandgap structures, which operates within telecom windows. The device is realized in an asymmetric $ {{\rm SiO}_2}/{{\rm TiO}_2} $SiO2/TiO2 photonic crystal (PC) microcavity with the defect layer of the graphene disk placed in the center of the structure. The theoretical analysis of the optical properties of the narrowband FBG filter is given based on the combination of the density matrix approach with the transfer matrix method. The effect of the incident angle and the polarization of the probe field on the transmittance spectra is calculated. Also, tuning the filtering wavelength and the number of guided modes is performed by changing the properties of PC's defect layer. It is shown that depending on the ratio of the coupling fields' intensity, the probe field absorption can be minimized and even be amplified in $ {\lambda _0} = 1550\;{\rm nm} $λ0=1550nm. The results show very promising potential for fabrication of FBG filters operating in the near-infrared regime for light wave communications.

All-optical switch based on doped graphene quantum dots in a defect layer of a one-dimensional photonic crystal.

We discuss the light pulse propagation in a one-dimensional photonic crystal doped by graphene quantum dots in a defect layer. The graphene quantum dots behave as a three-level quantum system and are driven by three coherent laser fields. It is shown that the group velocity of the transmitted and reflected pulses can be switched from subluminal to superluminal light propagation by adjusting the relative phase of the applied fields. Furthermore, it is found that by proper choice of the phase difference between applied fields, the weak probe field amplification is achieved through a one-dimensional photonic crystal. In this way, the result is simultaneous subluminal transmission and reflection.

Utilizing electromagnetically induced transparency in InAs quantum dots for all-optical transistor design.

We propose a multilayer medium with semiconductor quantum dot nano-structures as a defect layer for all-optical control of the 1.55 µm probe beam. The effect of the coupling field and incoherent pump on absorption and dispersion properties of the quantum dot defect layer is investigated. Depending on the intensity of the coupling field and rate of the incoherent pump field, the possibility of the absorption cancellation and even amplification are demonstrated. The optimum values of the coupling field intensity and incoherent pump field for complete transmission or amplification are obtained. The dynamical behavior of the structure is investigated, and the estimated switching time scales are about tens of picoseconds.

Proposal for a compact design for real-time optical bistability switching via a semiconductor cavity containing quantum wells.

A compact design for semiconductor cavities including coupled AlGaN/AlGaAs quantum wells is proposed for all-optical switching of the bistability process. First, physical and geometrical parameters are optimized to engineer the conducting electrons' energy levels in the quantum wells. Then, finite element simulations based on Schrödinger equations are executed to estimate the states of the charge carriers for AlGaN/AlGaAs as the active region. Next, the optical coupling and pumping fields are applied to the active region to both initiate the bistability and facilitate its real-time control. The Maxwell-Bloch approach based on rotating-wave approximation is employed to analyze the optimal conditions for controlling the behavior of optical bistability (OB). It is found that the threshold of OB can be optimized to have low values by tuning the intensity of coupling fields and the rate of an incoherent pumping field. This provides a fast real-time switching facility to control output intensity of the systems. The proposed scheme could have potential applications in optical memories, in which it is paramount to have active control over the readout of the system's quantum states. Thanks to the high nonlinear response of semiconductors, the featured device would be a prospective candidate for on-chip ultrasubluminal wave propagation studies and narrowband real-time switching and filtering applications.

Colossal Kerr nonlinearity based on electromagnetically induced transparency in a five-level double-ladder atomic system.

The paper is aimed at modeling the enhanced Kerr nonlinearity in a five-level double-ladder-type atomic system based on electromagnetically induced transparency (EIT) by using the semi-classical density matrix method. We present an analytical model to explain the origin of Kerr nonlinearity enhancement. The scheme also results in a several orders of magnitude increase in the Kerr nonlinearity in comparison with the well-known four- and three-level atomic systems. In addition to the steady-state case, the time-dependent Kerr nonlinearity and the switching feature of EIT-based colossal Kerr nonlinearity is investigated for the proposed system.

Wideband slab photonic crystal waveguides for slow light using differential optofluidic infiltration.

A new type of wideband slow light with a large delay bandwidth product in a slab photonic crystal waveguide with a triangular lattice of circular air holes in a silicon-on-insulator substrate based on optofluidic infiltration is demonstrated. It is shown that dispersion engineering through infiltrating optical fluids-with different refractive indices n(1f) and n(2f)--in the first two rows of the air holes innermost to the waveguide results in an improved normalized delay bandwidth product ranging from 0.187 to 0.377 with large bandwidth (12 nm<Δλ<32 nm) and group index (14.20< n(g)< 24.62) around 1550 nm. The nearly zero group velocity dispersion on the order of 10-(20) s(2)/m is achieved in all of the structures. These results are obtained by numerical simulation based on a three-dimensional-plane-wave expansion method.

Compact triple coupled quantum well system for electrical/optical control of optical bi/multistability.

Optical bistability (OB) and optical multistability (OM) are investigated in a triple coupled quantum wells system inside a semiconductor cavity sandwiched by distributed Bragg reflector mirrors. By proper manipulation of the optical and electrical parameters, the behaviors of OB and OM can be efficiently controlled. We show that, by tuning the tunneling rates between the quantum wells, the threshold and hysteresis cycle of OB and OM can be engineered. The effect of the incoherent pump field as well as the cooperation parameter on creation of OB is also discussed.

Optically controllable switch for light propagation based on triple coupled quantum dots.

A switch is proposed for controlling the subluminal and superluminal light propagation through the triple coupled quantum dots system. The steady-state and transient behavior of the absorption and the dispersion of a probe pulse through a triple quantum dots molecule are investigated. We demonstrate that the group velocity of a light pulse can be controlled from subluminal to superluminal or vice versa by controlling the rates of incoherent pumping and tunneling between electronic levels. Switching time is calculated by discussing the dependency of optical transient properties on the incoherent pumping and inter-dot tunneling rates. We introduce three controlling parameters that make it possible to control the wave propagation electrically or even optically in such coupled quantum dot systems.