Nanolasers based on photonic bound state in the continuum

Описание: Dr. (Tony) Son Tung Ha presents his research:
Dielectric nanoparticles supporting Mie-resonances at visible wavelengths are receiving significant attention from the nanophotonic community as an alternative for metal-based plasmonic counterparts. On the one hand, the dielectric particles show minimal Ohmic loss at visible wavelengths. On the other hand, they can be made with active materials tailoring great functionalities for nanophotonic devices [1]. One of the applications for such nanoparticles is as a coherent light source (a.k.a laser) by coupling with a suitable gain medium. However, a single nanoparticle supporting low-order Mie resonances (i.e., dipole, quadrupole) has a relatively low quality (Q) factor (i.e, in order of 10) and thus cannot be used alone as an optical resonator. In order to achieve a sufficiently high Q factor, engineering these resonances by means of coupling with adjacent resonances is needed. In this talk, I will present several design concepts for nanolasers based on the collective resonances of dielectric nanoantennas. The interference of collective resonances associated with the bound state in the continuum (BIC) or Van Hove singularity will be discussed based on Mie theory analysis. I will show experimentally and theoretically directional nanolasers based on two-dimensional arrays [2], one-dimensional arrays [3], and a single nanoantenna [4] made out of GaAs. In these cases, GaAs act both as resonance and as gain medium (a.k.a active nanoantenna). However, due to its poor gain characteristic, lasing can only be achieved at a cryogenic temperature (i.e., 77 K). By using a more efficient gain material such as CdSe/CdxZn1-xS nanoplatelets or InGaP multi-quantum well, room temperature lasing operation can be achieved [5, 6]. This work presents design guidelines for high-performance in-plane and out-of-plane lasers, which may find broad applications in optoelectronics.