Experimental demonstration of single-mode topological valley-Hall lasing at telecommunication wavelength controlled by the degree of asymmetry

Abstract

Topology plays a fundamental role in contemporary physics and enables new information processing schemes and wave device physics with built-in robustness. However, the creation of photonic topological phases usually requires complex geometries that limit the prospect for miniaturization and integration and dispossess designers of additional degrees of freedom needed to control topological modes on-chip. By controlling the degree of asymmetry (DoA) in a photonic crystal with broken inversion symmetry, we report single-mode lasing of valley-Hall ring cavities at telecommunication wavelength. The DoA governs four photon confinement regimes at the interface of topologically distinct valley-Hall domains and evidences an interplay between the width of the topological bandgap and the quality factor of ring-like modes for single-mode operation. Our results open the door to novel optoelectronic devices and systems based on compact topological integrated circuits.

Robust valley polarized states beyond topology

“…Our results reveal the role of interface effects in forming gapless chiral edge (kink) states and expand how we can exploit valley DOF and engineer valleytronic devices. This includes new opportunities to develop low-loss compact delay lines 11 , on-chip isolation, slow-light optical buffers, and lasers 10,33 . Lastly, the waveguiding phenomenon demonstrated here is applicable not only to the electromagnetic spectrum and various optical systems, but also to other wave systems such as plasmonics, mechanics and acoustics.…”

“…This has changed with the advent of PTIs [13][14][15][16][17][18][19][20][21][22][23][24] , which, like their electronic counterparts 25 , enable backscattering-immune edge modes along almost arbitrarily shaped interfaces. Among the three basic topological phases -quantum Hall 26 , quantum spin-Hall 27, 28 , and quantum valley-Hall 29,30 topological insulators-the latter, which relies on the valley degree of freedom (DOF) 1 in crystals is arguably the easiest to implement in bosonic systems 2,[5][6][7][8][9][10][11][31][32][33] and is of the most interest to the development of on-chip optical devices, motivating of this work.…”

Topological Valley Photonics: Physics and Device Applications

“…The topological cavities have also been proved to be very useful for topological lasers. [ 32,120–123 ] In the previous study, [ 32 ] Zeng et al demonstrated a terahertz QCL based on the topological cavity with sharp corners (see Figure a). The QCLs are compact, electrically pumped semiconductor lasers operating at the mid‐infrared and terahertz frequencies.…”

“…The topological valley‐Hall lasers at optical frequencies have also been investigated experimentally in the previous studies. [ 120,121 ] In the previous study, [ 120 ] the authors realized a room‐temperature laser from the triangle‐shaped topological cavities formed by two domains of VPCs with opposite valley‐Chern numbers (Figure 11c). Different from other works, the previous study [ 120 ] identified a unique triade lasing mode whose emission exhibits hot spots at the three corners of the cavity (see Figure 11d).…”

“…Different from other works, the previous study [ 120 ] identified a unique triade lasing mode whose emission exhibits hot spots at the three corners of the cavity (see Figure 11d). In the previous study, [ 121 ] Noh et al demonstrated a single‐mode lasing action in a topological valley‐Hall laser at telecommunication wavelength. The measured output power versus input power spectrum (Figure 11e) clearly shows a threshold behavior characteristic of lasing.…”