Abstract
We design a non-parity-time-symmetric plasmonic waveguide-cavity system, consisting of two metal-dielectric-metal stub resonators side coupled to a metal-dielectric-metal waveguide, to form an exceptional point, and realize unidirectional reflectionless propagation at the optical communication wavelength. The contrast ratio between the forward and backward reflection almost reaches unity. We show that the presence of material loss in the metal is critical for the realization of the unidirectional reflectionlessness in this plasmonic system. We investigate the realized exceptional point, as well as the associated physical effects of level repulsion, crossing and phase transition. We also show that, by periodically cascading the unidirectional reflectionless plasmonic waveguide-cavity system, we can design a wavelength-scale unidirectional plasmonic waveguide perfect absorber. Our results could be potentially important for developing a new generation of highly compact unidirectional integrated nanoplasmonic devices.
Highlights
In the past few years, parity-time (PT ) symmetric optical systems have attracted considerable attention because they provide a route to study the physics of non-Hermitian Hamiltonians
In our proposed two-port plasmonic system (Fig. 1), by manipulating the elements of the scattering matrix, the two eigenvalues can be coalesced and form exceptional points. This leads to unidirectional reflectionless propagation in either the forward (r f = 0, rb = 0) or the backward direction
We instead tune the geometric parameters of the proposed structure (Fig. 1) to realize the exceptional point and obtain unidirectional reflectionlessness
Summary
In the past few years, parity-time (PT ) symmetric optical systems have attracted considerable attention because they provide a route to study the physics of non-Hermitian Hamiltonians. There has been significant progress in using PT -symmetric periodic optical structures with balanced gain and loss to attain unidirectional light reflectionlessness. In such structures the reflection is zero when measured from one end of the structure at exceptional points, and nonzero when measured from the other end [16,17,18]. Feng et al and Wu et al achieved unidirectional light reflection in easier to fabricate structures without gain media [20, 21] This is due to the fact that exceptional points exist in a larger family of non-Hermitian Hamiltonians [24].
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