Experimental observation of wave localization at the Dirac frequency in a two-dimensional photonic crystal microcavity

Abstract

Trapping light within cavities or waveguides in photonic crystals is an effective technology in modern integrated optics. Traditionally, cavities rely on total internal reflection or a photonic bandgap to achieve field confinement. Recent investigations have examined new localized modes that occur at a Dirac frequency that is beyond any complete photonic bandgap. We design AlO dielectric cylinders placed on a triangular lattice in air, and change the central rod size to form a photonic crystal microcavity. It is predicted that waves can be localized at the Dirac frequency in this device without photonic bandgaps or total internal reflections. We perform a theoretical analysis of this new wave localization and verify it experimentally. This work paves the way for exploring localized defect modes at the Dirac point in the visible and infrared bands, with potential applicability to new optical devices.

From graphene to fullerene: experiments with microwave photonic crystals

“…Since then there has been a tremendous development regarding experimental studies of various aspects related to the hexagonal structure of graphene like, e.g. with dielectric photonic crystals [15,36,[97][98][99][100]. Such systems have the great advantage with respect to superconducting microwave photonic crystals that their shape can be varied, e.g.…”

Photonic Dirac cavities with spatially varying mass term

“…In future research our Dirac cavities, emulating relativistic trapping, effective "Dirac atoms," can also be spatially arranged to form spin-degenerate and particle-hole symmetric arrays of "molecules" or even crystals that may exhibit even more exciting physics properties stemming from the collective response. Complementing to other ways of trapping in Dirac systems (49,50), our work suggests that optical spin-full metasurfaces with Dirac dispersion can serve as an efficient toolkit to probe relativistic wave physics on a silicon chip and also envisions applications, such as source of arbitrary vector beams for on-chip generation of structured light.…”

Topological Phases of Photonic Crystals under Crystalline Symmetries

“…Relevant to PhC design, these invariants can be useful for finding spectrally-isolated Dirac points for applications such as creating cavity states that are algebraically localized to embedded point defects [28][29][30][31]89] or enabling large-area single-mode lasing [90,91].…”

“…A wide variety of topological phases have been realized using PhC-based platforms (as distinct from waveguide-arrays [6,7], coupled-resonator [8,9] or microwave-circuit [10] realizations). In one and two dimensions, this includes analogs of the SSH model with quantized polarization [11][12][13], Chern insulators [14][15][16][17][18][19], quantum spin-Hall-like phases [20][21][22][23][24], Dirac semi-metals [25][26][27][28][29][30][31], valley-Hall phases [32][33][34][35], bulkobstructed higher-order topological insulators (HOTIs) [36][37][38][39][40][41], including quadrupolar HOTIs [42][43][44], and fragile phases [45]. Several of these have also been proposed for photonic device applications such as for lasing [13,[46][47][48], harmonic generation [49,50]…”