Room-Temperature Lasing in Colloidal Nanoplatelets via Mie-Resonant Bound States in the Continuum

Abstract

Solid-state room-temperature lasing with tunability in a wide range of wavelengths is desirable for many applications. To achieve this, besides an efficient gain material with a tunable emission wavelength, a high quality-factor optical cavity is essential. Here, we combine a film of colloidal CdSe/CdZnS core−shell nanoplatelets with square arrays of nanocylinders made of titanium dioxide to achieve optically pumped lasing at visible wavelengths and room temperature. The all-dielectric arrays support bound states in the continuum (BICs), which result from lattice-mediated Mie resonances and boast infinite quality factors in theory. In particular, we demonstrate lasing from a BIC that originates from out-of-plane magnetic dipoles oscillating in phase. By adjusting the diameter of the cylinders, we tune the lasing wavelength across the gain bandwidth of the nanoplatelets. The spectral tunability of both the cavity resonance and nanoplatelet gain, together with efficient light confinement in BICs, promises low-threshold lasing with wide selectivity in wavelengths.

Single and Multi‐Mode Directional Lasing from Arrays of Dielectric Nanoresonators

“…[ 24,25 ] However, the experimental realizations of BICs and their applications in the visible wavelength range have been considerably limited and started to gain interest only recently. [ 22,24,26 ]…”

High‐Q Transparency Band in All‐Dielectric Metasurfaces Induced by a Quasi Bound State in the Continuum

“…[ 1 ] These are states that, despite lying in the continuum of modes, remain localized. Such properties make them particularly interesting in Photonics, [ 2–6 ] for their diverging Q‐factors without the need of complex fine optical cavities, thus leading to a rich phenomenology being explored these days such as lasing, [ 7–9 ] enhanced non‐linearities [ 10,11 ] and photoluminescence, [ 12 ] sensing, [ 13 ] chirality, [ 14 ] and spin‐directive coupling. [ 15 ] Interestingly, upon slightly perturbing the parameter that governs the BIC condition, high‐Q resonances are observed, termed in turn quasi‐BICs, [ 16–18 ] which, if interacting with another broad resonance, may as well induce Fano resonances with extremely narrow, asymmetric line shapes.…”

Photonic Bound States in the Continuum: From Basics to Applications

“…The flexibility that BICs have introduced to the design and realizations of high-Q resonances in nanophotonic systems has positioned them to benefit the nonlinear photonics community immensely. BICs have thus far been utilized to boost a plethora of nonlinear effects, including the optical Kerr effect, [57,58] lasing action, [18,55,[59][60][61][62][63][64] second-and third-harmonic generation, [56,[65][66][67][68][69][70] four-wave mixing, [65] dynamical nonlinear image tuning, [71] and many more. This section will shed a brief light on the latest advancements pertinent to the role of BICs in intensifying nonlinearities in nanophotonic platforms.…”

“…The use of the high-Q BIC resonances to provide feedback for lasing has enabled directional, scalable, controllable, and low threshold microlasers. [18,55,[59][60][61][62] In addition, due to the nonzero topological charges associated with BICs, the laser emission at the BIC points is naturally a vector beam. [63,64] While the first experimental demonstration of BICs in optical structures did not take place until around a decade ago, [4,25,27] BIC-based lasers had been reported long before that.…”

“…This enables flexibility in the design of lasing cavities that can be on the scale of a few hundred nanometers. [ 62 ] Additional exciting advancements in BIC‐based lasing include multi‐wavelength lasing, [ 61 ] Figure 2m, low‐threshold room temperature lasers, [ 60 ] topological lasers, [ 59 ] and many others.…”