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The optical polarization from a hybrid system including a closely spaced spherical SQD (modeled as a three-level V-type system) and a metal nanoparticle which are considered classically and are connected by the dipole–dipole interaction mechanism is investigated. The interaction between the SQD and the MNP shows an interesting optical response. In the weak probe field regime and MNP nonlocality correction, the absorption spectrum of the hybrid system exhibits an EIT window with two absorption peaks and the plasmon-assisted quantum interference plays an important role in the position and amplitude of these peaks, which are intensely altered by including the nonlocal effects. The probe diffraction grating is created based on the excitons-induced transparency by applying a standing-wave coupling field. The results of this study are useful in numerous areas of all-optical communications.

In this work, we revisit the optical response of a one-dimensional photonic crystal consisting of graphene monolayers and a plasmonic nanocomposite as a defect layer in the structure. By taking advantage of the modified transfer matrix approach, the analytical solution of the light transmission and field distribution of the photonic crystal are evaluated. Besides, by considering one of the layers as a Kerr-nonlinear medium, we delve into optical bistability phenomenon in the model for two different cases. Our numerical results reveal that the proposed photonic crystal can enhance the field distribution and reduce the optical bistability’s threshold in comparison to the conventional photonic crystals. Furthermore, the optical bistable switch-up and switch-down thresholds of the proposed resonator can be tailored flexibly by plasmon-plasmon interactions in the defect layer. Finally, the electric field distribution amelioration and optical bistability by means of graphene layers in the structure are attainable. The influences of the parameters such as the graphene and the nanocomposite on the performance of OB are analyzed and compared in the two different cases. Therefore, present approach can lay the groundwork for designing highly sensitive surface plasmon resonance biosensors and switches where the proposed technique may find unprecedented capabilities.

In this paper, we study the optical properties and surface plasmon resonance of a bimetallic core-shell spherical nanoparticle exhibiting monolayer graphene coatings. The extinction cross section (Qex) and slow light factor of this structure are investigated. The effect of coated graphene, host medium, and geometrical parameters such as the core radius and thickness of the shell on the Qex and the slow light factor are studied. The results show that the monolayer of graphene enhances the absorption and also leads to a redshift in the Qex and the slow light spectrums. These unique optical properties of bimetallic nanoparticles render them attractive for a broad range of applications such as biological sensors and optical communication devices.

In this study, we investigate tunable broadband optical cavity via a medium with four-level atoms interacting with two strong pump fields and a weak probe field in an N-type configuration. The results indicate the amplitude of the Stokes field causes an additional control mechanism of the dispersion behavior. Moreover, the four-wave mixing condition induces higher linear gain for the probe field. Therefore, it allows the compensation of unavoidable optical losses through the optical cavity. By adjusting the control fields in the four-wave mixing condition, the negative dispersion of the atomic medium is able to balance the normal dispersion of cavity in the zero-absorption area, consequently a white-light cavity with tunable wideband is achievable. The present scheme is interesting for development of white-light-cavity applications such as gravitational wave detection.

A new approach for diffracting the weak probe beam into higher-order directions is proposed via electromagnetically induced grating in second field quantization formalism, offering a new way for implementations of quantum information with semiconductor quantum dots. The formalism of second field quantization allows describing atoms and photons as a many-body system. An induced diffraction grating is formed based on the electromagnetic induced transparency when a standing-wave coupling field is applied to a spherical quantum dot as a three-level system. Due to phase modulation, the zeroth-order light intensity becomes weak, and the first-order diffraction is improved affectedly. On the contrary, the probe beam is barely diffracted via absorption modulation. The simulation results verify that photon numbers of probe and control fields, as well as other parameters in the QD, can lead to the diffraction efficiency of phase grating to be improved. Phase diffraction grating accompanied with a high transmissivity is demonstrated, and the first-order diffraction efficiency reaches $$30\%$$. Also, the impact of QD dimensions on its optical response is investigated. This model may find potential applications in designing the semiconductor quantum dot-based photonic devices in optical communications and quantum information networks.

In order to investigate optical pulling forces exerted by an electromagnetic field, we develop a theoretical framework based on electrostatic theory and Maxwell stress tensor. We apply this framework to calculate the optical pulling force on elliptical cylinder nanoparticles with gain medium, which we put forward as an alternative material platform to optimize and tailor tractor beams. Moreover, the optical force can be further enhanced and flexibly tuned by controlling the physical and geometrical parameters of the proposed structure. The pulling and pushing force could be switched by changing the location of the hemisphere witch has complex susceptibility in the structure. Altogether, our theoretical findings can pave the way to increase the use of this structure for further applications based on active nanoparticles

We study the interaction of electromagnetic field with two of the most tunable nanostructure geometries for nanoplasmonics including the magneto-optical nanoshell structure and the spheroidal geometry. We investigate the effect of combining both geometry and magneto-optical properties within the same nanostructure on the field enhancement factor and optical bistability behaviors. Since the coupling between the inner and outer surface plasmons of the nanoshell is stronger for the elongated spheroidal geometry as compared to that for the spherical case, field enhancement in ellipsoid nanoparticles is much more saleintiant. Moreover, the plasmonic field enhancement is four orders of magnitude larger for the spheroidal nanoshells as compared to spherical nanoshells. In addition to the appearance of optical bistability in this system, it is found that the threshold and window of bistability are strongly dependent on magneto-optical properties and geometry of the core–shell nanoparticle.

In this study, we investigate the optical bistability of graphene-coated nanoparticles with cylindrical core–shell structure at terahertz frequency, because graphene displays optical bistability and multistability in a broad range of incident optical intensity. The choice of core–shell system is due to its larger local electric field enhancement, where this characteristic is important for the optical bistable systems. This optical bistability strongly depends on the geometry of the nanoparticle, the fractional volume of the metallic core as well as Fermi energy of graphene. The surrounding medium could also finely affect the optical bistability and induce switching from optical bistability to optical tristability. Since the prosperity of optoelectronics properties of graphene and the importance of core–shell nanoparticles have attracted enormous interest, this model may find potential applications in optical bistable devices such as all-optical switches and biosensors at terahertz communication in near future.

Optical response of a complex nanodimer comprising a semiconductor quantum dot via Coulomb interaction to a metal nanorod is analyzed theoretically. Optical bistability (OB) behavior of a coherently coupled exciton-plasmon (plexcitonic) hybrid system under a laser field is investigated. The bistable exciton population in a hybrid metal–semiconductor nanodimer response is shown, and it could be pointed out that OB behavior is strongly influenced by various parameters such as size of metal nanoparticle, interparticle distance as well as intensity of probe laser field. We show that OB can be observed for a plexcitonic system and depends strongly on the type of the metals which are good candidates for plasmonic applications. The numerical calculations show the gold nanorod exhibits significant optical bistability. The result promises various applications in the field of all-optical information processing at the nanoscale, the most basic of them being the optical switching, optical memory, optical transistor and optical logic.

In this research, the optical absorption condition in a nanostructure slab consisting of three layers of graphene is theoretically investigated. This structure is distinct from the previous models and is a geometrically asymmetric structure. By means of Maxwell equations and the appropriate boundary conditions in the present model, the absorption coefficient is calculated. One of the most important features of this absorbent is owning $$100\%$$ absorption at the incident angles smaller than reported in the previous works that makes this nanostructure much more applicable in integrated carbon-based photonics, especially graphene-based photodetectors. In this structure, one can reduce the incident angle which leads to coherent perfect absorption (CPA) at $$16.29^{\circ }$$. Furthermore, by doing the optimization analysis, the optimal parameters for achieving the CPA condition are estimated.

A novel two-dimensional phase and amplitude electromagnetically induced grating is proposed. This model improves the sensitivity of electromagnetically induced grating to the microwave field. The system experiences electromagnetically induced transparency (EIT) via interacting dark resonances. When two-dimensional standing control fields are applied to a Rydberg five-level EIT system, two sub-EIT systems appear and the central peak in the EIT window is splitted. Frequency splitting of two central absorption peaks is proportional to the microwave field strength. The simulations show that the efficiency of higher orders of two-dimensional EIG could be enhanced compared to a common four-level single-dark-state system without microwave field. Therefore, one can take advantage of the phase modulation to control the probe light dispersing into the required high orders. This proposed model is appropriate to be utilized as an all-optical switch and router in optical networking and communication based on microwave field.

We propose a scheme for intracavity electromagnetically induced transparency and white light cavity via three-level Ladder-type Rb atoms. The system is driven by coherent and incoherent fields. Due to the position dependent atom-field interaction, the tunable optical susceptibility of the probe field can be achieved. By using an incoherent pump field and choosing proper parameters, one can control dispersion behavior of the probe field. In weak probe field limit, cavity bandwidth narrowing and broadening could be controlled via atomic systems in different conditions. Assuming the intracavity electromagnetic-induced transparency and the white light cavity conditions, it’s possible to control the susceptibility to satisfy the resonance condition over a wide frequency range. Tuning and controlling bandwidth of the optical cavity may find interesting applications in investigating cavity-QED phenomena and designing novel all-optical devices such as optical switches.

In regards to the interaction between 2D materials and laser beams, electrical conductivity is the cornerstone due to the fact that the optical absorption is correlated to electrical and opto-electrical properties. In this paper, the linear electrical conductivity (σ(1)) and nonlinear properties (σ(2) and σ(3)) for MoS2 will be investigated theoretically. So as to study the linear electro-optics effect (Pockels effect) in monolayer and the quadratic electro-optics (Kerr effect) in a bilayer of MoS2, σ(2) and σ(3) are derived, respectively. In this work, in order to achieve the σ(1), σ(2) and σ(3), we calculate the first, second and third order of susceptibility of MoS2 (χ(1), χ(2) and χ(3)) by implication of the first order electrical permeability of MoS2 (ɛ(1)), which has been reported in preceding studies. In the next step, by taking advantage of ɛ(E) = ɛ(1) + χ(2)|E| and σ(E) = σ(1) + σ(2)|E|, which express the linear electro-optics (Pockels) effect, the second order of electrical conductivity (σ(2)) can be acquired. Moreover, by considering ɛ(E) = ɛ(1) + χ(3)|E|2 and σ(E) = σ(1) + σ(3)|E|2 as the embodiment of the quadratic electro-optics (Kerr) effect, the third order of electric conductivity (σ(3)) are being calculated. Having this potential for calculating the optical nonlinear response in TMDs would lay the groundwork for designing and engineering a new generation of nonlinear devices premised upon TMDs.

In this paper, the effect of radial anisotropy on optical bistability in the cylindrical nanoshells is theoretically investigated within the quasi-static approximation. We consider two cases: when the shell is anisotropic and the core is nonlinear metal and when the core is anisotropic and the shell is a nonlinear metal. The dependence of optical bistability on the size of the nonlinear/anisotropic shell or core, the embedding medium, the anisotropy parameter, and the type of noble metals as candidates for plasmonics is studied and demonstrated. We show that by changing the type of the plasmonic metal, the switching threshold field changes can be used to design nanoparticle-based all-optical sensors. It is also shown that significant optical bistability and all-optical switching behavior can be obtained in the cylindrical nanoshells due to nonlinearity enhancement via the plasmonic structure.

Some optical properties including the linear and nonlinear susceptibility and electromagnetically induced phase grating (EIG) in graphene under Raman excitation is studied. A single-layer graphene nanostructure driven by coherent and incoherent fields is investigated theoretically. It is revealed that by adjusting the amplitude of control and incoherent fields, the linear and nonlinear absorption as well as Kerr nonlinearity of the medium can be optimized. It is realized that the enhanced Kerr nonlinearity can occur with zero linear absorption and nonlinear amplification. Furthermore, it should be noted that EIG in graphene is studied for the first time. The results indicate that the diffraction efficiency of the phase grating is dramatically enhanced by controlling the amplitude of coherent and incoherent fields, and an efficient electromagnetically induced phase grating can be obtained. A novel result shows a considerable improvement of the intensity of higher-order diffractions and switching between different orders of grating via incoherent pumping field. Therefore, this model can be used in real experiments for the development of new types of nanoelectronic devices used for the realization of all-optical switching processes.

A new scheme for investigating electromagnetically induced grating (EIG) in the vanishing two-photon absorption condition in a three-level ladder-configuration n-doped semiconductor quantum well is presented. By applying a standing-wave field interacting with the system, the absorption and dispersion of the probe field will change with the spatial periodical modulation. It is shown that the first-order diffraction intensity sensitively depends on the intensity of coupling fields, detuning of applied laser fields and interaction length. Moreover, it can reach its maximum on varying the system parameters. A novel result shows the considerable efficiency of higher order diffractions is significantly improved via relative phase between applied laser fields. Furthermore, it is found that the intensity of the switching and coupling fields can increase the efficiency of the phase grating in the present model. Such a unique feature of the cooperative Electromagnetic Induced Grating may be extended to further develop diffraction based new photonic devices in quantum information networks and new photonic devices in all-optical switching and optical imaging.

An artificial molecule consisting of an SQD and an MNR embedded in 3D photonic crystal is proposed to realize EIG. Using the quantum mechanical density matrix approach, we have derived an expression of the absorption coefficient in the SQD in presence of MNR. Nanoparticle geometry can modify the local fields that determine SQD-MNP coupling and to engineer the hybrid optical response. The probe absorption is reduced via a strong coupling field, demonstrating spectral transparency window. It is worth noting that the background affects the relaxations of SQD. So, by making use of 3D photonic crystal as the background medium, reduced decay rate and consequently substantial local-field enhancement rate are provided. Based on EIT effect and a strong standing-wave field, diffraction grating is achievable. The first-order diffraction intensity can reach its maximum by tuning the system parameters. This model may be useful in designing new devices in all-optical communication.

In this paper, dual optical bistability in a sandwich structure including graphene monolayers, dielectric layers, and a composite of golden plasmonic nanoparticles layers is proposed and studied. The theoretical and numerical results show that the asymmetric sandwich structure offers suitable dual optical bistability in THz range. Moreover, wide dual optical bistability behavior can be achieved via inserting plasmonic nanoparticle composite as two sided layers in the multilayer graphene structure, in which the said composite counterbalances the reduced graphene nonlinearities at higher frequencies. Therefore, we can have appropriate optical bistability in the favorable THz frequency range. The results provide using multilayer graphene structures for future all-optical bistability-based, low-power, and tunable optical devices in all-optical communication technology.

In this study, we investigate the transfer of energy from a donor molecule to an acceptor molecule nearby a spherical multilayer nanoparticle consisting of a core surrounded by two shells (core@shell@shell nanoparticle), with focus on the role of graphene and gain medium in the resonance energy transfer between molecules. We obtain analytical expressions for the interaction energy between the dipoles and the energy enhancement factor in a hybrid plasmonic nanoshell-molecular system consisting of a pair of molecules positioned near a plasmonic three-layer nanoparticle. Owing to the more flexible tunability of multishell nanoparticles, the resonance energy transfer can be enhanced and tuned from IR-visible-UV regions by controlling the size of the nanosphere core or shells. In addition to the effect of the gain medium which enhances the plasmonic resonance in order of magnitude, the impact of a graphene-coated three-layer nanosphere on the energy transfer is studied by taking into account the role of dipolar, quadrupolar, octupolar, hexadecapolar, and triakontadipolar plasmonic modes.

We study the nonlinear optical response of graphene in nanostructures. The spherical nanoparticle coated with a monolayer of graphene displays enhanced optical Kerr nonlinearity and, consequently, optical bistability and multistability in a broad range of incident optical intensity. This optical bistability significantly appertains on the geometry of the shell-coated nanoparticle, the fractional volume of the metallic core, as well as the core genre and Fermi energy of graphene. In particular, Fermi energy could also affect the optical bistability and induce switching from optical bistability to optical multistability. Due to the importance of core–shell nanoparticles, this model may find potential applications in optical bistable devices such as all-optical switches, optical transistors, and memories.

We study the interaction of an electromagnetic field with a core-shell nanostructure and propose a nonlocal effective medium theory for a core-shell structure made of a nonlocal core and a magneto-optical shell cylinder embedded in the host medium. In addition to the appearance of optical bistability and tristability in this system, it is found that the threshold and window of bistability are strongly dependent on the nonlocality and magneto-optical properties of the core-shell nanoparticle, the size of the nanoparticle, and the incident wavelength. By fine modification of these parameters, it is possible to achieve maximal enhancement of optical nonlinearity from the proposed system. Our study offers a theoretical direction to further structure design and optimization and also applications in the high speed all-optical signal processing.

A new scheme for obtaining an electromagnetically induced grating (EIG) via biexciton coherence in quantum well nanostructures is developed. It is theoretically shown that exciton spin relaxation and biexciton binding energy have important roles in producing efficient dual electromagnetically induced phase grating. In this structure, due to biexciton coherence, the higher order diffraction intensities of the grating can be observed. Furthermore, it is shown that the efficiency of different orders in the grating patterns could be controlled by biexciton energy renormalization (ESR) and relative phase between the applied laser fields.

We study the nonlinear optical response of multilayer metallic nanoparticles driven by an electromagnetic wave, which can show large field enhancement, hence significantly enhancing optical processes. In addition to optical bistability (OB), we find that optical multistability (OM), which plays a more important role in some applications than OB, is achievable and can be obtained in a multilayer plasmonic nanoparticle. Our results demonstrate that owing to strong localized fields created in the core and each layer of multilayer nanoshells, which occurs in the particles at frequencies close to the surface plasmon resonance, multilayer nanoparticles are promising systems with unique optical characteristics to control the light by light at the nanometer scale. It is demonstrated that OB can be converted to OM via adjusting the wavelength of the applied field and the size of the nanoshell, and the system can manifest optical hysteresis. It is found that the optical bistable or multistable threshold and the sha...

A new scheme for investigating electromagnetically induced grating in four-level cascade-type of 87Rb cold atoms is presented. The novel result indicates that the diffraction efficiency of phase grating is dramatically enhanced due to the presence of an RF-driven field and a diffraction efficiency up to 34% can be obtained. Furthermore, it is found that the frequency detuning of the applied laser fields with the corresponding atomic transition and the interaction length can improve the efficiency of the phase grating in the present atomic model. This work has potential applications in all-optical communication processes.

A new scheme to investigate an electromagnetically induced grating in an N-type configuration in the presence of a strong-standing coupling field, additional coherent fields, and microwave driven fields is presented. By considering the coherent population trapping (CPT) condition in a four-level microwave driven N-type atomic system, a novel nonlinear optical storage is obtained via linear absorption vanishing and giant Kerr nonlinearity during light propagation. It is revealed that nonlinear properties in this atomic medium are maximum in the CPT condition, and these nonlinear properties could be affected and modulated by means of a microwave driven field. In this condition high-phase modulated diffraction efficiency is attained. The diffraction pattern is sensitive to variables of the phase and amplitude of microwave field. Consequently one can control the efficiency of different orders of grating more conveniently. The first-order diffraction efficiency of the grating, about 45%, can be obtained by choosing optimum values for the phase and amplitude of the microwave field. It is shown that the phase and modulation grating could be controlled effectively by atomic field-radiation parameters such as the interaction length L of atomic samples and applied field detunings. It has been noted that a novel fast communication device could be obtained at the zero absorption point and on the superluminal light level.

The effect of correlated white noises on the optical bistability behavior of three-level atomic systems is theoretically investigated. Noise-induced bistability is demonstrated in an atomic optical bistable system consisting of three-level atoms in Λ-type configurations confined in an optical ring cavity. The output field as a result of enhanced Kerr nonlinearity induced by atomic coherence in the electromagnetically induced transparency system is variable due to the noises in laser parameters and the cooperativity parameter. Therefore, noise is mainly responsible for such induced bistability in the system. It is found that with the cross-correlation noises, the hysteresis loop of optical bistability can be clearly expanded in comparison with the deterministic case and the atomic system could show multistability behavior. This is specifically considerable for positive cross-correlated noises where it could expand the domain of the hysteresis loop. In the presented atomic system the numerical result shows that noise can induce bistability in the absence of spontaneously generated coherence. Furthermore, it is salient that the noise could induce bistability when the system is below its deterministic threshold for bistability.

An electromagnetically induced phase grating (EIG) controlled by coherent population trapping (CPT) in a four-level Y-type atomic system is studied. The CPT condition promotes significantly the dispersion of light into the first-order diffraction in constructing a phase modulation grating by transferring energy from zero-order to first-order diffraction. The diffraction efficiency of the phase grating is enhanced by up to 30% of the total probe intensity at the first-order diffraction. The present atomic scheme takes full advantage of the microwave-driven field for generating the EIG, which induces the quantum coherence and controls linear and nonlinear behaviors of the present system. Furthermore, it is noticed that the higher-order diffraction intensities are improved via a microwave-driven field and the phase and amplitude of the microwave field can improve the efficiency of the phase grating. These novel results could find potential applications in developing new photonic devices, such as all-optical switching at low light levels.

An electromagnetically induced phase grating controlled by spontaneous generated coherence (SGC) in a four-level N-type atomic system is studied. The results indicate that the diffraction efficiency of the phase grating is dramatically enhanced due to the existence of SGC, and an efficient electromagnetically induced phase grating can be obtained. A novel result is considerable improvement of the intensity of higher-order diffractions via relative phase between applied laser fields. Furthermore, it is found that the frequency detuning of the switching and coupling fields with the corresponding atomic transition, incoherent pumping, and the interaction length can improve the efficiency of the phase grating in the present atomic model.