Electromagnetically induced grating in asymmetric quantum wells via Fano interference

Multi-wave-mixing-induced nonlinear modulation of diffraction peaks in an opto-atomic grating

We propose an atomic model in close-loop configuration, which exhibits controllable symmetric and asymmetric evolution of significantly enhanced diffraction peaks of the weak probe beam in an opto-atomic grating at far-field regime. Such results are obtained by the linear and nonlinear modulation of the intensities of the diffraction peaks as a result of multi-wave-mixing-induced modification of spatially modulated coherence in a closed four-level atomic system. Novelty of the results lies in predicting the diffraction pattern with uniform peak height due to the dominance of the amplitude part of the grating-transfer-function at the condition of exact atom-field resonance, which is unique to the present model. Efficacy of the present scheme is to apply it in producing nonlinear light generated by four-wave-mixing-induced control of spatially modulated coherence effect. The work also finds its importance for its applicability in the field of all-optical devices.

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 optical limiting in quantum dot molecules

We present a convenient way to obtain an optical power limiting behavior in a quantum dot molecule system, induced by an interdot tunneling. Also, the effect of system parameters on the limiting performance is investigated; interestingly, the tunneling rate can affect the limiting performance of the system so that the threshold of the limiting behavior can be a function of the input voltage, allowing the optimization of the limiting action. Furthermore, by investigating the absorption of the probe field, it is demonstrated that the optical limiting is due to a reverse saturable absorption mechanism; indeed, analytical results show that this mechanism is based on a cross-Kerr optical nonlinearity induced by the tunneling. Additionally, the limiting properties of the system are studied by using a Z-scan technique.

Tunneling-induced phase grating in quantum dot molecules

We present an alternative scheme for the preparation of the phase grating in quantum-dot molecules, where the tunnel coupling occurs between two quantum dots. In the presence of interdot tunneling, the nonlinear dispersion can be significantly enhanced with nearly vanishing linear and nonlinear absorption due to the tunneling-induced quantum coherence. With the help of a standing-wave control field, the weak probe light could be diffracted into high-order direction. It is shown that parameters such as the weak-driving intensity, driving detuning, tunneling strength, and interaction length could be used to adjust the diffraction intensity effectively. Our scheme is focused on the weak standing-wave driving and weak tunneling strength, which may provide an easy and actual way to obtain the phase grating and may have potential applications in quantum-optics and quantum-information-processing devices in the solid-state system.

Nonlinear optical induced lattice in atomic configurations

Traditional artificial lattice with untunable refractive index have been restricted to flexible applied to kinds of micro medium imaging. This study proposes a novel approach to quantifying lattice using nonlinear optically induced periodic lattice, which possesses a striking feature of tunable refractive index, to further broaden current knowledge of optical imaging equipment. We conduct self-dressed and dual-dressed nonlinear four-wave mixing (FWM) signal modulation in the atoms by using the dressing effect of standing waves, and then investigate the space amplitude modulation and synthetization (amplitude and phase) modulation of the electromagnetic induced lattice (EIL) of FWM signal at the atom surface. The EIL presented in the far-field diffraction region confirms that diffraction intensity of the FWM signal can be easily transformed from zero-order to higher-order based on the dispersion effects. The tunable EIL with ultra-fast diffraction energy change can contribute to a better understanding of nonlinear process and provides a further step toward developing two-dimensional nonlinear atomic higher-resolution.

One- and two-dimensional electromagnetically induced gratings in an Er3+ - doped yttrium aluminum garnet crystal

A coherently prepared Er3+-doped yttrium aluminum garnet (YAG) crystal with a four-level ionic configuration is exploited for realizing one-dimensional (1D) and two-dimensional (2D) electromagnetically induced gratings (EIGs). Owing to the probe gain induced by the incoherent pump, the diffraction efficiency of the crystal grating, especially the first-order diffraction, can be significantly improved via increasing the incoherent pumping rate or decreasing the probe detuning. The enhancement of the grating diffraction efficiency originates from the interference between the gain and phase gratings. It is also demonstrated that the diffraction of the crystal grating can be dynamically controlled via tuning the intensity and detuning of the standing-wave driving field or the concentration of Er3+ ion. More importantly, the probe energy of the diffraction side lobes around the central principle maximum is comparable to that of the first-order diffraction field for small driving intensity or large driving detuning. Our scheme may provide a possibility for the active all-optical control of optical switching, routing and storage in fiber communication wavelengths.

Phase-controlled electromagnetically induced symmetric and asymmetric grating in an asymmetric three-coupled quantum well

Fraunhofer light diffraction of a weak probe field passing through an asymmetric three-coupled quantum well, which is driven by a standing wave and two coupling laser fields, is investigated. Depending on which transitions are coupled by the probe and standing field, two schemes are considered. It is demonstrated that owing to the closed-loop transition, optical properties and the diffraction pattern of the probe field in both schemes are highly affected by the relative phase of the applied fields and can be controlled by this parameter. Moreover, it is shown that the proposed schemes have multifunction capabilities. In the first scheme, as a result of varying relative phase, the electromagnetically induced absorption phase grating turns to the electromagnetically induced gain phase grating with remarkable efficiency, while in the latter scheme, a significant result is revealed: Tuning the relative phase can lead to inducing optical parity-time symmetry, which gives rise to an asymmetric diffraction grating. Such an all-optical phase-sensitive operation could be useful in optical switching and optical communications.

Electromagnetically induced gain-phase grating in a double V-type quantum system

Finding schemes to promote the efficiency of phase gating nowadays is a main concern. We address this issue by devising a feasible and innovative scheme that enables us to obtain a gain-phase grating. It is shown that a linearly polarized probe field traveling through a double V-type closed-loop atomic system, which is driven by a standing wave and a microwave field, can be efficiently diffracted in higher orders. As a significant result, we find that intensity of the diffracted field is highly amplified in every single order direction compared with the intensity of the input probe field. The responsible mechanism is induced gain accompanied by the large dispersion arising due to the applying microwave field. It is shown that in the presence of a microwave field, among various parameters, the relative phase of the applied fields has the most appreciable effect on enhancing the intensity of diffraction orders. It is also demonstrated that quantum interference between decay channels of the quantum system can be used as a tool to manipulate the intensity of diffraction orders.

Control of electromagnetically induced grating by surface plasmon and tunneling in a hybrid quantum dot-metal nanoparticle system

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.

Beam splitter and router via an incoherent pump-assisted electromagnetically induced blazed grating

We propose a scheme for a beam splitter and a beam router via an electromagnetically induced blazed grating in a four-level double-Λ system driven by an intensity-modulated coupling field and an incoherent pump field. The blazed grating relies on the incoherent pump process, which helps in inducing large refractivity with suppressed absorption or even gain. Consequently, the weak probe beam can be effectively deflected with high diffraction efficiency, and, meanwhile, its energy is amplified. When using an intensity mask with two symmetric domains in the coupling field, the presented blazed grating provides the possibility of a symmetric beam splitter. The diffraction efficiency and diffraction order of the gratings are sensitive to the intensity of the coupling field, and, thus, the gratings can function as a tunable asymmetric beam splitter or a beam router, which distributes the probe field into different spatial directions. Therefore, the proposed scheme may have potential applications in optical communication and networking.

Squeezing induced high-efficiency diffraction grating in two-level system

We show the effect of squeezed vacuum on laser-induced grating in a weak standing-wave-driving two-level atomic system. Using the optical Bloch equation and the Floquet harmonic expansion, we obtain the linear response of the medium with respect to the probe field, which determines the transmission spectrum and diffraction intensity. At the presence of the squeezing, the grating with large intensity both in the first- and higher-order directions can be obtainable even though the driving is relatively weak. The responsible mechanism is due to squeezing-induced gain accompanied by the large dispersion. Based on the spatial gain and phase modulations, the first- and high-order diffraction intensities simultaneously could have the large values. Such a scheme we present could have potential applications in implementing lensless imaging and developing the photon devices in quantum information processing.

Two-dimensional Talbot self-imaging via Electromagnetically induced lattice

We propose a lensless optical method for imaging two-dimensional ultra-cold atoms (or molecules) in which the image can be non-locally observed by coincidence recording of entangled photon pairs. In particular, we focus on the transverse and longitudinal resolutions of images under various scanning methods. In addition, the role of the induced nonmaterial lattice on the image contrast is investigated. Our work shows a non-destructive and lensless way to image ultra-cold atoms or molecules that can be further used for two-dimensional atomic super-resolution optical testing and sub-wavelength lithography.

Tunneling induced absorption with competing Nonlinearities

We investigate tunneling induced nonlinear absorption phenomena in a coupled quantum-dot system. Resonant tunneling causes constructive interference in the nonlinear absorption that leads to an increase of more than an order of magnitude over the maximum absorption in a coupled quantum dot system without tunneling. Resonant tunneling also leads to a narrowing of the linewidth of the absorption peak to a sublinewidth level. Analytical expressions show that the enhanced nonlinear absorption is largely due to the fifth-order nonlinear term. Competition between third- and fifth-order nonlinearities leads to an anomalous dispersion of the total susceptibility.

Electromagnetically induced holographic imaging in hybrid artificial molecule

We propose two schemes of holographic imaging with an object that has no any macro structure itself. The tunable electromagnetically induced grating (EIG) is such a kind of object. We obtain an EIG based on the periodically modulated strong susceptibility in a three-level ladder-type hybrid artificial molecule, which is comprised of a semiconductor quantum dot and a metal nanoparticle coupled via the Coulomb interaction. The holographic interference pattern is detected either directly in the way of classical holographic imaging with a coherent field being the imaging light, or indirectly and nonlocally in the way of two-photon coincidence measurement with a pair of entangled photons playing the role of imaging light. This work provides a practical prototype of electromagnetically induced transparency-based holographic solid-state devices for all-optical classical and quantum information processing.

Phonon induced phase grating in quantum dot system

Electromagnetically induced phase grating is theoretically investigated in the driven two-level quantum dot exciton system at the presence of the exciton-phonon interactions. Due to the phonon-induced coherent population oscillation, the dispersion and absorption spectra are sharply changed and the phase modulation is enhanced via the high refractive index with nearly-vanishing absorption, which could effectively diffract a weak probe light into the first-order direction with the help of a standing-wave control field. Moreover, the diffraction efficiency of the grating can be easily manipulated by controlling the Huang-Rhys factor representing the exciton-phonon coupling, the intensity and detuning of the control field, and the detuning of the probe field. The scheme we present has potential applications in the photon devices for optical-switching and optical-imaging in the micro-nano solid-state system.

Theoretical investigation of electromagnetically induced phase grating in RF-driven cascade-type atomic systems

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.

Coherent manipulation of spontaneous emission spectra in coupled semiconductor quantum well structures

In triple coupled semiconductor quantum well structures (SQWs) interacting with a coherent driving filed, a coherent coupling field and a weak probe field, spontaneous emission spectra are investigated. Our studies show emission spectra can easily be manipulated through changing the intensity of the driving and coupling field, detuning of the driving field. Some interesting physical phenomena such as spectral-line enhancement/suppression, spectral-line narrowing and spontaneous emission quenching may be obtained in our system. The theoretical studies of spontaneous emission spectra in SQWS have potential application in high-precision spectroscopy. Our studies are based on the real physical system [Appl. Phys. Lett.86(20), 201112 (2005)], and this scheme might be realizable with presently available techniques.

Electromagnetically induced self-imaging in four-level atomic system

In this paper, a special gradient-index electromagnetically induced transparency medium is induced with a Gaussian control field, which can be realized in a four-level ⁸⁷Rb cold atomic cloud. Special directional self-imaging and imaging transforming properties are studied in this work. Simulated results show that a complex object can be imaged in the cold atoms, as the control field substituted with the elliptical Gaussian beam, then the self-imaging is directional, which has potental application in encryption.