The electromagnetically induced grating is investigated in a four-level double V-type quantum system. It is shown that the electromagnetically induced transparency established by the cross-Kerr nonlinear effect can be canceled by the four-wave mixing in a closed-loop atomic system and that the diffraction of the probe beam depends on the relative phase of the applied fields and can be controlled by this parameter. We find that an additional nonlinear contribution is established in the medium response by applying a microwave field to the system and that the electromagnetically induced absorption grating turns to the electromagnetically induced phase grating. This contribution leads to 100% diffraction efficiency in the first-order direction, so we can say that the proposed grating could be considered as a special candidate for the optical networking and communication.
The electromagnetically induced grating is investigated in a four-level double V-type quantum system. It is shown that the electromagnetically induced transparency established by the cross-Kerr nonlinear effect can be canceled by the four-wave mixing in a closed-loop atomic system and that the diffraction of the probe beam depends on the relative phase of the applied fields and can be controlled by this parameter. We find that an additional nonlinear contribution is established in the medium response by applying a microwave field to the system and that the electromagnetically induced absorption grating turns to the electromagnetically induced phase grating. This contribution leads to 100% diffraction efficiency in the first-order direction, so we can say that the proposed grating could be considered as a special candidate for the optical networking and communication.
Abstract We proposed a theoretical scheme for two-dimensional (2D) electromagnetically induced grating (EIG) in a closed-loop four-level atomic system driven by a weak probe field, a traveling-wave control field, two orthogonal standing-wave fields and a microwave field. Due to low amplitude modulation accompanied with large phase modulation, EIG can be obtained and the probe energy can be diffracted into first-order and even high-order directions with high efficiency. The results show that the diffraction pattern and efficiency of the EIG could be adjusted effectively by the probe field detuning, the coherent field intensity, the interaction length. Meanwhile, the quantum interference between the amplitude modulation and phase modulation can be manipulated by the relative phase, which can be used to regulate the diffraction pattern and efficiency of the 2D EIG. Our scheme of 2D EIG may be useful in beam splitting and all-optical switching.
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.
Abstract A probe laser beam can be completely absorbed in an atomic resonance frequency region, however, if a coupling laser beam is further applied to the atom, the atomic medium can exhibit electromagnetically induced transparency, i.e the probe beam can be completely transmitted through the atomic medium. Thus, if the coupling beam is a standing wave field with nodes and antinodes, it will cause in space a periodic modulation of the transmitted spectrum of the probe field. This means that the probe field propagates through the atomic medium just as it passes through a diffraction grating which is called electromagnetically induced grating. Based on amplitude or phase modulation of transmission function, the absorption grating or the phase grating can be formed, respectively. In this work, based on controllable absorption and dispersion properties of a three-level V-type atomic system, we study the control of the absorption grating and the phase grating with respect to the intensity and the frequency of the laser fields. The absorption diffraction pattern at the two-photon resonance is obtained, while the phase diffraction pattern appears when there is a frequency shift of either the coupling frequency or the probe frequency compared to the corresponding atomic resonance frequency. By adjusting the coupling or/and probe laser frequency, the absorption grating can be converted into the phase grating and the high-order diffraction efficiency can also be improved.
The optical properties of a four-level double-V-type closed-loop system is studied in the multiphoton resonance condition. It is shown that the phase-dependent electromagnetically induced transparency (EIT) window is established and by changing the relative phase of the applied fields, EIT switches to electromagnetically induced absorption. Moreover, the optical bistability (OB) behavior of the system is studied, and it is demonstrated that the cross-Kerr-effect-induced OB depends on the relative phase of the applied fields, and it can be controlled by either intensity or relative phase of laser fields. By applying a microwave field to drive the hyperfine transition between two lower states, the optical properties change and OB switches to optical multistability. This can be used for detection of longer wavelengths than visible light.
We investigate a four-level double-Λ atomic scheme interacting with four laser fields, a weak probe field, a weak signal field and two driven fields, in a closed-loop configuration. We study the Kerr nonlinearity associated with cross-phase modulation based on electromagnetically induced transparency. Our results show, in this closed-loop system, that the strength of cross-phase modulation and two-photon absorption are dependent critically on the relative phase between the excitation paths. By choosing the parameters appropriately, large cross-phase modulation can be achieved within a wide transparency window, while two-photon absorption is cancelled completely. The strength of cross-phase modulation can be enhanced much more by decreasing the intensities of two driven fields.
We investigate a four-level double-Lambda atomic scheme interacting with four laser fields, a weak probe field, a weak signal field and two driven fields, in a closed-loop configuration. We study the Kerr nonlinearity associated with cross-phase modulation based on electromagnetically induced transparency. Our results show, in this closed-loop system, that the strength of cross-phase modulation and two-photon absorption are dependent critically on the relative phase between the excitation paths. By choosing the parameters appropriately, large cross-phase modulation can be achieved within a wide transparency window, while two-photon absorption is cancelled completely. The strength of cross-phase modulation can be enhanced much more by decreasing the intensities of two driven fields.