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An asymmetric coupled three well system has been shown to exhibit PT-symmetry and electromagnetically induced grating (EIG), owing to electromagnetic induced transparency under the application of standing wave control and pump fields. The detuning of the probe and the uniform amplitudes of the standing wave control and pump fields could be used to tune the PT-symmetry. The probe beam is asymmetrically diffracted by the EIG either in positive or negative diffraction angles owing to the PT symmetry. The angle of diffraction can be controlled by the interaction length, probe detuning, and the uniform amplitudes of the standing wave control and pump fields.

A model of electromagnetically induced grating (EIG) assisted by the spontaneously generated coherence (SGC) in the ladder-plus-Y double quantum dot (DQD) system is proposed. Using the density matrix theory, the amplitude and phase of the transmission function are studied. It is shown that the transmission is enhanced by the presence of SGC, and the resultant diffraction intensity can increase by controlling the phase. The SGC-assisted EIG controlled by two, three, and four coupling optical fields are studied respectively. Remarkably, we find that the system acquires a huge diffraction intensity when the wetting layer-quantum dot (WL-QD) field is high in the case of four coupling fields.

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.

The characteristics of an electromagnetically induced grating (EIG) created in symmetric multiple quantum wells in the regime of electromagnetically induced transparency have been presented. The EIG is created due to absorption and phase modulation under the electromagnetically induced transparency. The increasing value of the Rabi frequency of control standing wave enhances transmission through the EIG. In addition, it is found that the diffraction efficiency of the grating and the intensity of the first-order diffraction can be controlled by controlling the Rabi frequency of the standing wave control field and the interaction length in the quantum well. Optical nonlinearities can improve the diffraction intensity of significant orders, particularly zeroth and first order. The improvement is largest in case only the Kerr is the dominant nonlinearity and moderate under quintic nonlinearity. Present results may be useful in communication and signal processing.

The radiation intensity redistribution of the probe field upon its scattering by spatially periodic atomic population gratings in a medium with a four-level tripod configuration of atomic states is investigated theoretically. Conditions are found under which a significant redistribution of the probe-wave field intensity occurs, and a “diffraction” pattern is formed with an efficient probe-field intensity transfer to the first-order maxima.

Electromagnetically induced holographic imaging using strongly interacting Rydberg atoms is investigated via electromagnetically induced grating (EIG). We consider two schemes, i.e., by direct detection of holographic imaging pattern, known as electromagnetically induced classical holographic imaging (EICHI), and by employing entangled photon pairs for imaging which is called as electromagnetically induced quantum holographic imaging (EIQHI). Both schemes are employed to obtain 1D and 2D holographic imaging. In EICHI and EIQHI, amplitude and phase information of EIG can be imaged with controllable image variation in size. It is noticed that holographic imaging is influenced by van der Waals (vdW) effect present in Rydberg atoms.

We propose a scheme to study the electromagnetically induced grating (EIG) of surface polaritons (SPs) in a negative index metamaterial/rare-earth-ion-doped crystal interface waveguide system, based on coherent population oscillation (CPO) modulating by a standing wave control field. Absorption grating can be formed via the large absorption modulation induced by the linear susceptibility of the system; the diffraction of SPs can be realized but with a very small first-order diffraction efficiency and the phase modulation in this case, is negligible. However, when the giant Kerr nonlinearity is taken into account, the phase modulation can be significantly enhanced and accompanied by high transmission at the same time, thus, a phase grating, which effectively diffracts SPs into a high-order direction, can be induced. For both the absorption and phase grating, the dependencies of the first-order diffraction efficiency on the Rabi frequency of the standing wave control field, optical detuning, and interaction length are discussed. The results obtained here have certain theoretical significance for spectral enhancements and precision measurements at the micro–nanoscales.

We propose a theoretical scheme for creating a two-dimensional Electromagnetically Induced Grating in a three-level $$\Lambda $$ Λ -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.

We propose a scheme of electromagnetically induced grating in 3-level symmetric quantum wells. Based on electromagnetically induced transparency, we obtain the intensity distribution of the Fraunhofer diffraction pattern of the probe field that is governed by a control field. The distribution of the intensity of the diffraction pattern of the grating can be controlled by controlling the Rabi-frequency of the control field, and the interaction length of the QW. Our results could be potentially used in semiconductor quantum well based photonic devices.

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.

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.

Graphene exhibits remarkable optical and electronic properties when interacts with electromagnetic field. These properties play a vital role in a broad range of applications, such as, optical communication, optical storage, biomedical imaging and security purposes. Based on electromagnetically induced grating (EIG), we study lensless holographic imaging via quantized energy levels of two-dimensional (2D) monolayer graphene model. We observe that by exploiting electromagnetically induced grating (EIG), holographic interference patterns via electromagnetically induced classical holographic imaging (EICHI) and, non locally, electromagnetically induced quantum holographic imaging (EIQHI) can be obtained in the infrared range (THz) of the spectrum. We notice that for EIQHI one can obtain image magnification using monolayer graphene via manipulation of certain controllable parameters. The scheme provides an experimentally viable option for the classical and quantum mechanical holographic imaging and possibilities for the design of graphene-based quantum mechanical devices which can have many applications.

Electromagnetically induced grating (EIG) in the ladder-plus-Y double quantum dot system is modeled and the diffraction grating properties are explored in this structure. A high transmission function is obtained under the high pump field. This function is reduced under increasing the probe field due to the Kerr effect. The phase of this function depends on pumping. It is shown that the application of another two fields from the wetting layer (WL)-quantum dot (QD) type is more efficient in obtaining very high diffraction intensity. So, EIG with high diffraction intensity is obtained under a four-field application. Note that, WL-QD field effect is not studied earlier. Neglecting the WL effect reduces the transmission by five times. The diffraction intensity of this system is six times higher than that obtained from a single QD structure.

We propose a scheme for generating an electromagnetically induced grating in a three-level Λ-type atomic system via multicolor coherence. Using the multicolour coupling field, the diffraction inten...

We theoretically propose a scheme for two-dimensional electromagnetically induced grating in a five-level atomic system interacting with two orthogonal standing-wave fields. In such atomic system, nonlinear absorption or refractivity can be significantly enhanced with nearly vanishing linear absorption under different resonant conditions. When applying two coupling fields with standing-wave pattern, absorption grating or phase grating, which efficiently diffracts a probe beam into high-order directions, can be formed in the media. The diffraction efficiencies of the gratings depend strongly on the interaction length, the intensities and detunings of the coupling fields. By investigating the third-order nonlinearity of the system, it is found that the spatial variations of amplitude and phase arise from the nonlinear modulation. The proposed gratings can be used as multi-channel beam splitter and have potential applications in optical information processing and optical networking.

A reflective diffraction grating with a periodic square-wave profile will combine the effects of thin-film interference with conventional grating behavior when composed of features having a different refractive index than that of the substrate. A grating period of 700–1300 nm was modeled and compared for both silicon (Si) and silicon dioxide (SiO2) to determine the behavior of light interaction with the structures. Finite element analysis was used to study nanostructures having a multirefractive index grating and a conventional single material grating. A multimaterial grating has the same diffraction efficiency as that of a grating formed in a single material, but had the advantage of having an ordered relationship between the grating dimensions (thickness and period) and the intensity of reflected and diffracted optical wavelengths. We demonstrate a color-selective feature of the modeled SiO2 grating by fabricating samples with grating periods of 800 and 1000 nm, respectively. A high diffraction efficien...

We propose a scheme for creating electromagnetically induced grating in a four-level double- Λ atomic system driven by a coupling field and an incoherent pump field. Owing to the incoherent pumping process, large refractivity accompanied with vanishing absorption or even gain across the probe field can be built up in the atoms, thus phase grating or gain-phase grating, which diffracts a probe light into different directions, can be formed with the help of a standing-wave coupling field. The diffraction efficiency of the gratings can be tuned by the coupling field intensity and the incoherent pump rate, hence the proposed gratings should be suitable for beam splitter and optical switching in optical communication and networking.

We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication.

Understanding and manipulating the non-Hermitian optical property based on coherent atomic gases is of great importance and has attracted much theoretical and experimental attentions. Advancing this study to the nonlinear optics regime is highly desirable due to its importance in fundamental physics and potential applications. In this work, we propose to realize a tunable electromagnetically induced grating (EIG) with parity-time ($\mathcal{PT}$) symmetry in a cold gas of Rydberg atoms, where interatomic interactions between Rydberg states are mapped to strong and long-range optical interactions, and investigate nonlinear light diffractions in this system. We show that for far-field diffraction, laser beams incident upon the $\mathcal{PT}$-symmetric EIG display distinctive asymmetric diffraction fringes, which can be actively manipulated through tuning the gain-absorption coefficient of the EIG, the incident intensity of the laser beam, and the nonlocality provided by Rydberg atoms. For near-field diffraction, the nonlinear Talbot diffraction carpets emerge and can be modulated by $\mathcal{PT}$ symmetry in the presence of strong nonlocal interactions, allowing the realization of controllable optical self-imaging. The results are not only imperative for the study of non-Hermitian nonlinear optics but also useful for characterizing the interatomic interaction in Rydberg gases and for designing new optical devices useful in optical information processing and transmission.

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.

A controllable electromagnetically induced grating (EIG) is experimentally realized in a coherent rubidium ensemble with 5S1/2-5P3/2-5D5/2 cascade configuration. In our work, a whole picture describing the relation between the first-order diffraction efficiency and the power of the coupling field is experimentally presented for the first time, which agrees well with the theoretical prediction. More important, by fine tuning the experimental parameters, the first-order diffraction efficiency of as high as 25% can be achieved and a clear three-order diffraction pattern is also observed. Such a controllable periodic structure can provide a powerful tool for studying the control of light dynamics, pave the way for realizing new optical device.

Two-dimensional (2D) optical lattices of driven cold atoms can provide a useful platform to construct 2D electromagnetically induced grating (EIG) with parity-time (PT) antisymmetry. This atomic grating is achieved by the spatial modulations of the atomic density and frequency detunings in the four-level double-Λ atomic system. Gain-assisted PT antisymmetry allows us to realize lop-sided Raman–Nath diffraction with high diffraction efficiency at the exception point. It is shown that the nontrivial phenomenon originates from non-Hermitian degeneracy of PT antisymmetry. Our scheme may provide the possibility for active all-optical control and conversion of the spatial beam in optics.

We have theoretically studied the electromagnetically induced grating (EIG) in a three-level \textbf{closed $\Lambda$-type atomic system}. The upper level is coupled to the two lower levels via a strong control and a weak probe \textbf{field}. In addition to these two optical fields a weak microwave field is also applied to couple the lower two levels. Our results show that the relative phase of the three fields \textbf{in the} presence of microwave field enhances the dispersion in the medium and consequently provides control over magnitude of the diffraction intensities. We \textbf{have optimized} the system parameters such as \textbf{strength of the fields} and interaction length to attain increased first order diffraction. Furthermore, we have also studied the effects of probe detuning on diffraction intensities. Interestingly, the probe detuning results in suppression of the zeroth order intensity while increasing the higher order intensities.

We investigate the effect of doped E r 3 + ion concentration on an electromagnetically induced grating in an E r 3 + -doped yttrium aluminum garnet (YAG) crystal. Due to the change of electric dipole moment and spontaneous emission decay induced by E r 3 + ion concentration, the Fraunhofer diffraction of the solid-state grating is sensitively dependent upon E r 3 + ion concentration. The three-level E r 3 + ion system with a closed loop leads to probe gain appearing in some concentrations of the E r 3 + ion, which significantly improves the first-order diffraction efficiency of the solid-state grating. Furthermore, it is demonstrated that the relative phase, signal detuning, and grating thickness have different effects on the first-order diffraction efficiency of the solid-state grating under different concentrations of the E r 3 + ion. Therefore, our scheme may provide a basis for selecting a suitable concentration to realize high-efficiency optical switching and routing in future integrated systems.

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 broad band tunable graphene based silicon–air grating structure is proposed. Electromagnetically-induced-transparency (EIT) window can be successfully tuned by virtually setting the desired Fermi energy levels on graphene sheets. Carrier mobility plays an important role in modulating the resonant depth. Furthermore, by changing the grating periods, light can be trapped at corresponding resonant positions where slow down factor is relatively larger than in the previous works. This structure can be used as a highly tunable optoelectronic device such as optical filter, broad-band modulator, plasmonic switches and buffers.

In this work, the electromagnetically induced transparency in a strained GaN/InGaN/AlGaN quantum well system, is theoretically studied. Energy levels and wave functions are calculated using the transfer matrix method. Effects of In and Al compositions, the well and barrier widths on the real and imaginary parts of the optical susceptibility are investigated. Results show that the electromagnetically induced transparency can be controlled via the structural parameters and geometrical size.

We present two schemes of Lau effect for an object, an electromagnetically induced grating generated based on the electromagnetically induced effect. The Lau interference pattern is detected either directly in the way of the traditional Lau effect measurement with a classical thermal light being the imaging light, or indirectly and nonlocally in the way of two-photon coincidence measurement with a pair of entangled photons being the imaging light.

We investigate the response of the molecular system to the magnetic field modulation. Molecular magnets are subjected to a strong standing ac magnetic field and a weak probe magnetic field. The transmission and absorption of the weak probe magnetic field can be changed due to quantum coherence and the spatially modulating of the standing field. And a electromagnetically induced grating is formed in the crystal of molecular magnets via electromagnetically induced transparency (EIT). The diffraction efficiency of the grating can be adjusted efficiently by tuning the intensity of the standing wave field and the single photon detuning.

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.

We theoretically study a two-dimensional electromagnetically induced phase grating in a four-level quantum system located near plasmonic metamaterials consisting of a periodic two-dimensional array of metal-coated dielectric nanospheres. The four-level quantum system interacts with a weak-probe laser field and a strong coherent coupling field with a standing-wave pattern. In the presence of plasmonic metamaterials the quantum system becomes sensitive to the relative phase between applied light. Therefore, the linear absorption and Kerr nonlinearity of the medium become phase dependent. Here, due to the standing-wave pattern of coupling light, an absorptive grating or phase grating can be formed in the quantum system. In our proposed model, we show that the diffraction efficiencies of the grating are related to the relative phase between applied fields, when the quantum system is located at different distances from plasmonic metamaterials.

In this paper, we investigate two-dimensional parity-time (PT) symmetry and electromagnetically induced grating (EIG) in four-level asymmetric triple quantum wells (QWs). Here, PT-symmetry and EIG are realized by appropriately varying the detuning value of the probe, and the modulation amplitudes of a coupling field and standing wave (SW) pump. By virtue of its PT symmetry, the EIG asymmetrically diffracts the probe beam. The angular switching of the diffracted beam can be achieved either by varying the probe or the coupling and SW pump fields. The intensity distribution of the diffracted beam over higher-order diffraction peaks depends on the interaction length in the QW. For small interaction lengths, most of the energy is distributed close to the central diffraction peak. With an increase in the interaction length, energy is gradually transferred to higher order diffraction peaks.

Electromagnetically induced grating (EIG) is extensively investigated as an artificial periodic structure in recent years owed to its simple reconfiguration and flexible adjustability. We report the experimental observation of EIG in cold rubidium atoms. The coupling and probe lasers are corresponding to the 5S1/2&minus, 5P1/2 and 5S1/2&minus, 5P3/2 transitions of a V-type electromagnetically induced transparency (EIT) configuration, respectively. A clear spatial intensity distribution of the probe laser with distinguished third-order diffraction pattern is recorded to character the EIG. The influence of the pertinent experimental parameters, such as coupling laser intensity and two-photon detuning on the diffraction pattern is investigated in detail. This is the first observation in visual form of the EIG in cold rubidium atoms. These results may potentially provide a nondestructive method to image cold atoms and pave the way for investigating non-Hermitian physics and the control of light dynamics.

An asymmetric double semiconductor quantum well is proposed to realize two-dimensional parity-time (PT) symmetry and an electromagnetically induced grating. In such a nontrivial grating with PT symmetry, the incident probe photons can be diffracted to selected angles depending on the spatial relationship of the real and imaginary parts of the refractive index. Such results are due to the interference mechanism between the amplitude and phase of the grating and can be manipulated by the probe detuning, modulation amplitudes of the standing wave fields, and interaction length of the medium. Such a system may lead to new approaches of observing PT-symmetry-related phenomena and has potential applications in photoelectric devices requiring asymmetric light transport using semiconductor quantum wells.

A method for diffracting the weak probe beam into unidirectional and higher-order directions is proposed via a novel Rydberg electromagnetically induced grating, providing a new way for the implementations of quantum devices with cold Rydberg atoms. The proposed scheme utilizes a suitable and position-dependent adjustment to the two-photon detuning besides the modulation of the standing-wave coupling field, bringing a in-phase modulation which can change the parity of the dispersion. We observe that when the modulation amplitude is appropriate, a perfect unidirectional diffraction grating can be realized. In addition, due to the mutual effect between the van der Waals (vdWs) interaction and the atom-field interaction length that deeply improves the dispersion of the medium, the probe energy can be counter-intuitively transferred into higher-order diffractions as increasing the vdWs interaction, leading to the realization of a controllable higher-order diffraction grating via strong blockade., Comment: 9 pages, 7 figures, Physical Review A in press

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.

We investigate the electromagnetically induced grating (EIG) in a quantum dot-metal nanoparticle (QD-MNP) hybrid system. The EIG can be controlled and improved by the surface plasmon effect and the interdot tunneling effect between quantum dots. By manipulating the tunneling effect and the QD-MNP distance, not only the first-order diffraction intensity of the grating can be efficiently enhanced, but also the EIG can be switched from the absorption grating to the gain grating. Almost two times the first-order diffraction efficiencies can be achieved in the gain gratings compared with the absorption gratings.

A quantum optical model involving a plasmonic nanostructure (PN) is proposed for controlling the diffraction efficiency of an electromagnetically induced grating in a four-level quantum system. By tuning the distance between the PN and the four-level quantum system, diffraction efficiency can be adjusted and energy can be transferred from zero order to higher orders. Moreover, due to the presence of the PN, the medium becomes phase-dependent and therefore, phase control of grating can be possible by changing the relative phase of the applied fields.

The electromagnetically induced Talbot effect offers a nondestructive and lensless way to image ultracold atoms or molecules (Wen et al., 2011 [12] ). In this paper, we propose another atomic imaging scheme based on the holographic imaging principle, in which three types of light source are employed as the imaging light to perform spatial interference. Compared to the previous self-imaging scheme, in the present one both the amplitude and phase information of the object can be imaged with the characteristic of arbitrarily controllable image variation in size, and the object to be imaged is no longer subject to the periodic structure.

In this paper, a planar polymer sub-wavelength grating whose period structure is modulated by different refractive index is proposed. The guided mode resonant of the proposed grating is analyzed with effective medium theory and the eigenvalue equation of the thin film waveguide, and the reflectance properties of the grating are simulated with rigid coupled-wave analysis. The reflectance property shows obvious polarization dependent. The influences of the grating period, thickness and the incident angle on the resonant wavelength are also analyzed. It is shown that the resonant wavelength shows redshift with the increase of grating period, dual resonant peaks occur when the grating thickness is of some certain values, and the resonant peak of normal incidence will split into 2 peaks on the condition that oblique incidence. This planar polymer sub-wavelength grating may find application in filters, polarization elements, reflectors and so on.

In this paper, diffraction properties of several gratings are considered on the basis of the Fourier physical theory. Binary gratings with unequal strip width are of particular interest, as well as the case of two interlaced gratings of the same period. Under scope are absorptive gratings, phase gratings, and mixed gratings. Some variants of binary gratings, as the so called Bi-Ronchi gratings (2D-gratings), are also discussed. In particular, phase gratings with absorption (mixed gratings) are also taken into account. The interferograms generated for this type of gratings are shown in this work. As examples, the patterns for a spherical mirror are obtained for different grating parameters and different values of primary aberrations. Some of the resulting relevant properties are remarked. Related experimental works from several structures of the gratings are shown. This study can be used not only for optical testing, but also for light gratings for particle diffraction or to describe diffraction effects of micro-gratings.

We study the quantum holographic imaging of one-dimensional electromagnetically induced grating created by a strong standing wave in an atomic medium. Entangled photon pairs, generated in a spontaneous parametric down-conversion process, are employed as the imaging light to realize coincidence recording. By theoretical analysis and numerical simulation, we find that both the amplitude and phase information of the object can be imaged with the characteristic of imaging nonlocally and of arbitrarily controllable image variation in size.

The spectral properties of an electromagnetically induced grating that is based on the spatial modulation of the Raman gain in the field of a standing pump wave in a three-level homogeneous medium have been discussed. It has been shown that, by varying the intensity or the frequency of the pump field, one can control the transmission and reflection spectra, while the transmission and reflection coefficients of the probe (Raman) wave can simultaneously be greater than unity. The influence of the nonideality of the standing wave on the spectral characteristics of the grating has been studied.

Reflective diffraction gratings consist of a periodic three-dimensional structure that produces appropriate constructive and destructive interference in order to redirect an incoming wave as a function of frequency. Depending upon the angle of incidence, the thickness required for this structure can range from a fraction of a wavelength to several wavelengths. While such a thickness does not present a problem for optical applications, it can make the diffraction grating very bulky for radio applications, notably in the lower frequency bands. This communication presents a new thin diffraction grating, employing resonant structures, whose thickness is only 1/34th of a wavelength. Simulations and measurements are presented for a thin diffraction grating, designed to operate in the VHF band in unfavorable outdoor conditions.

The present work theoretically investigates the electromagnetic resonance modes on two-dimensional (2-D) complex gratings consisting of a metallic grating, a dielectric film, and a metal substrate. We treat a complex grating as geometrical combination of two square grating elements with different sizes in a single unit cell. In order to identify various resonance modes, such as surface plasmon and magnetic resonance (or magnetic polariton) existing in gratings, the finite-difference time-domain method is employed in solving Maxwell’s equation. Differently from 2-D simple grating structures, we observe the diverse magnetic polariton modes associated with each grating elements in a single unit cell. Furthermore, if two different grating elements are merged together, magnetic polariton will be branched out into multiple modes. These characteristics of 2-D complex grating will be desirable for achieving broad-band absorption, which is critical for energy harvesting applications.

In this work, we proposed a simple mathematical model to explain the formation of grating structure in photosensitive germane-silica fibers written by KrF excimer laser and phasemask. In the observation, the growth of local index changes in the fiber in the bright fringes and dark fringes of the interference field share similar characteristics and can be represented by a single characteristic function. Through curve-matching technique, the interference visibility and the evolution of grating visibility during grating inscription can be determined.

Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are coupled by a radio frequency (RF) field. Both electromagnetically induced transparency and electromagnetically induced absorption can be obtained by tuning the frequency of RF field for both the linear polarization and elliptical polarization monochromatic lights. When the transfer of coherence via spontaneous emission from the excited state to the ground state is considered, electromagnetically induced absorption can be changed into electromagnetically induced transparency with the change of intensity of radio field. The transparency windows controlled by the RF field can have potential applications in the magnetic-field measurement and quantum information processing.

We theoretically investigate the phenomena of electromagnetically induced grating in a doppler-broadened Λ-type three-level atomic system with the spontaneously generated coherence (SGC) effect enhanced by an incoherence pump. It is found that the model can effectively diffract a weak probe field into high-order direction. We attribute the enhancement of diffraction mainly to the quantum interference resulting from the cross coupling between the two decay pathways. The diffraction efficiency behaves phase and doppler broadening-dependent phenomena, and can be greatly modulated by the SGC effect. Compared to the counter-propagating case, the co-propagating setting is more suitable for the purpose considered in this paper due to the effectiveness of Doppler-free.