Perfectly asymmetric Raman-Nath diffraction in disordered atomic gratings

Azimuthal modulation of electromagnetically induced grating using structured light

We propose a theoretical scheme for creating a two-dimensional Electromagnetically Induced Grating in a three-level \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\Lambda $$\end{document}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.

High-precision three dimensional atom localization via multiphoton quantum destructive interference

We propose an effective scheme for high-precision three dimensional(3D) atom localization via measuring the population of excited state in a four-level atomic system driven by a probe field and three orthogonal standing-wave fields. In this scheme, the position-dependent multiphoton quantum destructive interference leads to multiphoton excitation of the excited state and enhances the fluorescence emission. We show that adjusting the frequency detuning and phase shifts associated with the standing-wave fields can modify the multiphoton quantum destructive interference and lead to a redistribution of the atoms. The maximal probability of finding the atom at the certain position in one period of the standing-wave fields can be 100% and the highest spatial precision is about 0.02λ.

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.