Phase-controlled Optical PT symmetry and asymmetric light diffraction in one- and two-dimensional optical lattices
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Phase-controlled Optical PT symmetry and asymmetric light diffraction in one- and two-dimensional optical lattices Ali Akbar Naeimi1, Elham Darabi1, Ali Mortezapour2,a
, Ghasem Naeimi3
1 Department of Physics, Science and Research Branch, Islamic Azad University, Tehran, Iran 2 Department of Physics, University of Guilan, P. O. Box 41335-1914, Rasht, Iran 3 Department of Physics, Qazvin Branch, Islamic Azad University, Qazvin, Iran
Received: 5 August 2020 / Accepted: 28 September 2020 © Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract We propose a novel scheme for asymmetric light diffraction of a weak probe field in a one-dimensional (1D) and two-dimensional (2D) lattice occupied with cold atoms. The atoms are driven into the double-lambda-type configuration by a standing wave, two coupling laser fields and a probe. Our study suggests the proposed scheme is capable of forming an asymmetric diffraction as a result of inducing optical parity-time symmetry in both 1D and 2D lattices. Moreover, it is demonstrated that the asymmetric pattern of diffraction can be dynamically manipulated by means of adjusting the relative phase. Furthermore, it is revealed that in the case of 1D lattice (grating), intensity variation of the coupling fields has a significant impact on the intensity of diffraction orders.
1 Introduction Parity-time (PT) symmetry is an active area of research in physics owing to its significance in the realm of science and technology. Bender and Boettcher [1] had pioneering role in introducing concept of the parity-time (PT) symmetry (1998) in quantum mechanics. A decade later, the reports indicated that optical systems can be considered as a candidate to provide a foundation for experimental investigation of PT -symmetric ideas. Moreover, it has been demonstrated that the necessary condition for realization of PT symmetry in optical systems relies on satisfying n( r ) n ∗ (− r ) term, which means the real and imaginary parts of complex refractive index, respectively, must be an even and odd function of r. So far the experimental realization of the optical PT -symmetry in various structures such as lattices [2–5], waveguides [6, 7] and micro-cavities [8, 9] has been reported. Furthermore, it has found potential applications in diverse fields like unidirectional propagation [10–13], lasing [14–18], perfect absorbers [19–21] and sensors [22]. In this context, a couple of interesting phenomena such as Bloch oscillations [23], electromagnetically induced transparency (EIT) [24], PT-symmetric Talbot effect [25], Giant Goos–Hänchen shift [26, 27] and optical solitons [28] have also been investigated in optical PT-symmetric structures. In 1998, it was revealed that as a result of substituting a standing wave for the traveling wave of EIT, a diffraction grating could be formed in the atomic medium which yields the
a e-mail: [email protected] (corresponding author)
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