Topological beaming of light

Abstract

Nanophotonic light emitters are key components in numerous application areas because of their compactness and versatility. Here, we propose a topological beam emitter structure that takes advantage of submicrometer footprint size, small divergence angle, high efficiency, and adaptable beam shaping capability. The proposed structure consists of a topological junction of two guided-mode resonance gratings inducing a leaky Jackiw-Rebbi state resonance. The leaky Jackiw-Rebbi state leads to in-plane optical confinement with funnel-like energy flow and enhanced emission probability, resulting in highly efficient optical beam emission. In addition, the structure allows adaptable beam shaping for any desired positive definite profiles by means of Dirac mass distribution control, which can be directly encoded in lattice geometry parameters. Therefore, the proposed approach provides highly desirable properties for efficient micro–light emitters and detectors in various applications including display, solid-state light detection and ranging, laser machining, label-free sensors, optical interconnects, and telecommunications.

Compact coherent perfect absorbers using topological guided-mode resonances

“…In analogy to the zero-energy state solution of the Dirac equation, a junction of two topologically distinguished lattices supports a leaky JR state 16 , 17 at the center of the bandgap. In such structures, optical near-field and radiation patterns of this leaky JR state can be conveniently described, using the formal analogy of the photonic coupled-mode theory to the one-dimensional Dirac equation.…”

“…( 2 ) can be conveniently obtained by appropriately designing unit-cell geometry. For a rectangular grating-ridge unit cell of our interest here, the Dirac mass is determined primarily by fill-factor F of the grating as where sinc( x ) = sinc(π x )/(π x ) is the normalized sinc function, Δ ε = n c 2 – n d 2 is the dielectric constant contrast in the grating layer, n g is the group index of the guided mode, λ 0 is the bandgap center wavelength, and C 1 and C 2 are dimensionless constants associated with the strength of the first- and second-order diffraction processes, respectively 17 . Therefore, we can systematically configure f leak ( x ) = f inc ( x ) for a given arbitrary f inc ( x ) by taking fill-factor distribution F ( x ) according to Eqs.…”

Non-local and non-Hermitian acoustic metasurfaces

“…This can be essentially viewed as a leaky topological metasurface interacting with the surrounding environment. The interplay between topological states and the background medium has led to a series of exciting phenomena [266][267][268]. By incorporating the topological concept into a metasurface, we may pave the way for robustly rerouting wave scattering [269].…”

Phase of Topological Lattice with Leaky Guided Mode Resonance

“…The phenomenon of localized states, referring to the bulk-edge correspondence, confines light within a specific region [3,4], effectively creating a nonconventional cavity [5][6][7]. This confinement enables the light to serve as a beam emitter [8], similar to the operation of lasers [9][10][11]. By implementing such photonic structures, analogous to electronic systems, photonic topological key functionalities can be achieved despite the presence of non-Hermitian characteristics, including leakage [12][13][14].…”

“…Among these platforms, PhC slabs have gained significant popularity for exploring topological phenomena of light, particularly guided-mode resonances (GMRs) [31]. GMRs are characterized by their electromagnetic power being tightly confined within the slab while also being capable of coupling with external radiation, leading to leaky modes that can interact with extended states and radiate light [8,32].…”