Topological photonic crystal nanocavity laser

Abstract

Topological edge states exist at the interfaces between two topologically-distinct materials.The presence and number of such modes are deterministically predicted from the bulk-band topologies, known as the bulk-edge correspondence 1 . This principle is highly useful for predictably controlling optical modes 2-5 in resonators made of photonic crystals (PhCs), leading to the recent demonstrations of micro-scale topological lasers 6-10 .Meanwhile, zero-dimensional topological trapped states in the nanoscale remained unexplored, despite its importance for enhancing light-matter interactions and for wide applications including single-mode nanolasers. Here, we report a topological PhC nanocavity with a near-diffraction-limited mode volume and its application to single-mode lasing. The topological origin of the nanocavity, formed at the interface between two topologically-distinct PhCs, guarantees the existence of only one mode within its photonic bandgap 11 . The observed lasing accompanies a high spontaneous emission coupling factor stemming from the nanoscale confinement [12][13][14][15] . These results encompass a way to greatly downscale topological photonics 2-5 .

Topological phases in ring resonators: recent progress and future prospects

“…Thanks to its simplicity and relative ease of implementation, photonic analogues of the Su-Schrieffer-Heeger model have been realized in a variety of platforms [1], including waveguide lattices [19][20][21], plasmonic and dielectric nanoparticle arrays [22,23], photonic crystals [24,25], and microring resonators [26,27]. To create two-dimensional topological phases, there are two common approaches: using synthetic gauge fields or by perturbing honeycomb lattices.…”

Active topological photonics

“…1(d)). Another way to realize topological nanocavity is to utilize 1D topological photonic crystal nanobeams [27] (Fig. 1(e)).…”

Robust localized zero-energy modes from locally embedded PT -symmetric defects

“…With such practical applications in mind, we demonstrate the creation of these states for a specific structure of experimental interest, namely, a periodic dimer chain that in the passive case corresponds to a Su-Schrieffer-Heeger (SSH) chain [65] in its trivial coupling configuration. In its topologically nontrivial counterpart configuration, topological lasing utilizing edges or interfaces has been demonstrated in a number of studies [19][20][21][22]. In particular, in Ref.…”

“…This widespread study of topological systems originated from the classification of the Hermitian topological system [15]. Currently, nontrivial extensions of closed topological systems to their open counterparts attract increasing interest, connecting this area to non-Hermitian concepts such as paritytime (PT ) symmetry [16], and resulting in novel topological applications and phenomena such as topological mode selection and lasing [17][18][19][20][21][22].…”