Large and tunable lateral shifts in one-dimensional PT-symmetric layered structures

Abstract

The lateral shifts of the wave reflected and transmitted from PT-symmetric one-dimensional multilayer-structures are investigated near the coherent-perfect-absorption (CPA)-laser point and the exceptional points. We predict that at the CPA-Laser point, the reflections from both sides and transmission as well as the related shifts are all very large, reaching their negative (or positive) maxima. Moreover, we show that although the reflections are direction-dependent in the PT-symmetric multilayer-structure, the related lateral shifts have same behaviors from both sides. Additionally, one may realize the reversal of the lateral shift through the suitable adjustment of the incident angle and the layer numbers. Numerical simulations for Gaussian incident beams are performed, and reasonable agreement between the theoretical results and numerical simulations is found.

Characterizing optical resonances using spatial mode reshaping

“…The magnitude of the lateral shift is given by the slope of the phase change, −∂φ∕∂k ∥ , where φ is the phase of the complex reflection coefficient and k ∥ k sin θ is the parallel momentum (PM) of the incident radiation (i.e., the projected k-vector parallel to the interface) [3,4]. Similar effects have also been observed in systems that exhibit resonances [5][6][7] caused by the dramatic phase change near the resonant conditions. Unlike the simpler case of total internal reflection, these examples can exhibit a more complicated amplitude and phase response, particularly when the linewidth of the resonance is small.…”

Reflection Enhancement and Giant Lateral Shift in Defective Photonic Crystals with Graphene

“…The loss of graphene decreased greatly as the chemical potential exceeded 0.41 eV. Low loss in materials can induce a sharp change in the reflection coefficient phase [6]. As an incident beam impinges upon the structure, the lateral shift of the reflected beam can be derived by Δ = −dφ/dk [33].…”

“…Giant lateral shift has also been reported inside the reflection band, and become extremely large at exceptional points (EPs) in parity-time-symmetric (PT-symmetric) PCs [5]. Furthermore, a great lateral shift may also exist in non-Hermitian systems and periodic dielectric multilayers with PT-symmetry [6,7]. Meanwhile, low loss in slabs and defects embedded in PCs can greatly enhance the lateral shift [8,9].…”

“…On the other hand, non-Hermitian systems can induce many unique optical phenomena, and have become a hot topic in optics and other fields [10][11][12][13][14][15][16][17]. In non-Hermitian systems, large lateral shift can be obtained near exceptional point (EP) and coherent-perfect-absorption (CPA)-laser state [5,6,18], but the reflectivity of the EP is also zero and the reflectivity is very low near it [19][20][21] while the CPA-laser state is unstable, so these are not conducive to the observation of lateral shift for reflected beams.…”

Exceptional Points in Non-Hermitian Photonic Crystals Incorporated With a Defect

“…EPs and coherent perfect absorption-laser points (CPA-LPs) exist in PT-symmetric PCs [46]; however, it is more difficult to make complex dielectrics obey PT symmetry experimentally. Here, we embedded a defect in PCs.…”