Parity‐Time‐Symmetric Optical Lattice with Alternating Gain and Loss Atomic Configurations

Abstract

Since the periodic parity‐time (PT)‐symmetric potential can possess unique properties compared to a single PT cell (with only two coupled components), various schemes have been proposed to realize PT symmetry in optical lattices. Here, a PT‐symmetric optical lattice is experimentally constructed with simultaneous gain and loss in an atomic medium. The gain and loss arrays are created in the four‐level N‐type configurations excited by spatially alternating strong and weak pump fields, respectively, which do not require discrete diffractions and can be realized more easily with more relaxed operating conditions. Also, the gain and loss coefficients can be modified independently. The dynamical behaviors of the system are investigated by measuring the phase difference between two adjacent gain and loss channels. The demonstrated PT‐symmetric lattice with easy accessibility and better tunability shows obvious advantages in exploiting more peculiar properties and great improvements in practical applications of periodic PT‐symmetric potentials.

Lopsided diffractions of distinct symmetries in two-dimensional non-Hermitian optical gratings

“…We have examined the far-field Fraunhofer diffraction off a thin 2D atomic lattice subject to transversely periodic cross modulations, including pure PT -symmetry ones as well as hybrid ones as a combination of Hermitian, PT -symmetry, and non-Hermitian modulations along two orthogonal axes. These spatial modulations, now realizable through standard laboratory routines [66], can be all-optically controlled to generate nontrivial far-field patterns that span from double diagonal symmetric diffraction in two diagonal quadrants to single axial symmetric diffraction in two adjacent quadrants and single diagonal symmetric diffraction in a single quadrant. These patterns appear to be fairy robust against standard sources of noises (fluctuations), e.g., in the atomic density or in the intensity of trapping or pumping lasers [67].…”

RETRACTED ARTICLE: Optical rectification and absorption coefficients studied by a short-range topless exponential potential well with inverse square root

“…Nonlinear optics is a new field in optical theories which is becoming more and more mature 21–25 . And now it has been done well in experiments 26–28 . The optical rectification effect is a process of generating a low-frequency electrode field (THz) by the interaction of a pulsed laser and a nonlinear medium, and belongs to a special nonlinear optical effect 29,30 .…”

Enhanced nonreciprocal transmission through a saturable cubic-quintic nonlinear dimer defect

“…On the other hand, nonlinear processes can lead to asymmetric wave propagation without the need of an external magnetic field. Recent experimental advances have demonstrated that nonlinear optical lattices with alternating gain and loss atomic configurations are ideal realizations of non-Hermitian parity-time symmetric systems that can be explored to better understand the peculiar physical properties of these non-Hermitian systems in atomic settings [15,16].…”