Transport tuning of photonic topological edge states by optical cavities

Abstract

Crystal-symmetry-protected photonic topological edge states (PTESs) based on air rods in conventional dielectric materials are designed as photonic topological waveguides (PTWs) coupled with side optical cavities. We demonstrate that the cavity coupled with the PTW can change the reflection-free transport of the PTESs, where the cavities with single mode and twofold degenerate modes are taken as examples. The single-mode cavities are able to perfectly reflect the PTESs at their resonant frequencies, forming a dip in the transmission spectra. The dip full width at half depth depends on the coupling strength between the cavity and PTW and thus on the cavity geometry and distance relative to the PTW. While the cavities with twofold degenerate modes lead to a more complex PTES transport whose transmission spectra can be in the Fano form. These effects well agree with the one-dimensional PTW-cavity transport theory we build, in which the coupling of the PTW with cavity is taken as δ or non-δ type. Such PTWs coupled with side cavities, combining topological properties and convenient tunability, have wide diversities for topological photonic devices.

Active topological photonics

“…They can function as nanocavities embedded in 2D systems, offering a natural platform for developing integrated photonic circuits. Meanwhile, one may consider the introduction of defect-based nanocavities into 2D topological photonic crystals by, for example, fulling some airholes with dielectric [64] or introducing topological disorder [65]. These types of cavities have been far less investigated in the context of topological photonics, despite their possibilities to function as high performance nanocavities in topological nanophotonic systems.…”

Recent Progress in Chiral Topological Quantum Interface

“…Topological photonics has attracted widespread interest once proposed as it provides a new paradigm in the further development of various robust photonic devices for integrated quantum photonic circuits and quantum computing [9][10][11][12][13]. The robust edge states protected by band topology enable the highly potential possibility for chiral light-matter interaction [52][53][54][55], which have been observed in various photonic systems, including 1D photonic structures based on SSH model and AAH model [56,57], 2D topological photonic structures based on metamaterials, synthetic gauge field and ring resonator arrays [58][59][60][61] as well as complicated higher dimensional photonic structures [62]. Nevertheless, some limitations existing in these topological structures impose serious restrictions on the further development of topological photonic devices and cannot satisfy on-chip integration requirements.…”

Fragile topologically protected perfect reflection for acoustic waves

“…The fragile transport requires that the cavity eigenfrequency should be in the topological band gap. In photonic systems, one previous work proposed a similar idea to tune the transport of the phonic TESs, but it neglected the relation between the perfect reflection with the system topology [81]. In general, the ATES reflection can be explained as the breaking of the C 6v symmetry near the AC, which breaks the pseudo time-reversal symmetry (TRS) and leads to the pseudospin mixing.…”