Session Index

We experimentally demonstrated an unprecedented simple way to excite strong and broadband toroidal dipole (TD) response in the optical regime using dielectric metasurfaces upon plane-wave excitation. The peculiar electromagnetic portrait of TD metamaterials leads to an ultrahigh sensitivity for local refractive-index sensing. In addition, the effect of the coupling between TD and magnetic dipole (MD) moments on the nonlinear third-harmonic generation (THG) was investigated. A strong THG enhancement was found at the generalized Kerker effect, referring to the constructive interference between the total electric dipole (the sum of electric dipole and TD moments) and the MD mode. In order to further narrow down the resonant linewidth, several asymmetric structures such as tilted nanorod pairs and asymmetry kite-shaped nanopillars were designed to excite high quality factor resonances based on the concept of quasi-bound state in the continuum (quasi-BIC) and applied to sensing and nonlinear signal conversion.

  Preview abstract

The quasi-Bound States in the Continuum (quasi-BIC) is a resonance characterized by ultrahigh quality factor (Q-factor) with strong near-field distributions. We designed periodic amorphous silicon kite-shaped nanopillar arrays to achieve Fano-lineshaped quasi-BIC resonance supported by magnetic dipole (MD) and electric quadruple (EQ). Varying the asymmetry parameters of the kite-shaped structure leads to dramatic Q-factor variations and strong field confinement, which is beneficial for boosting nonlinear effects for third-harmonic generation (THG). The simulated (experimental) TH signal reaches more than four orders (one order) of magnitude enhancement at the quasi-BIC resonant frequency. This approach offers a platform for realizing tunable nonlinear metasurfaces.

  Preview abstract

Two-dimensional perovskites have become the trending materials for various photoelectric applications because of their excellent optoelectronic performance. However, the formation of self-trapped exciton attributed to the strong exciton-phonon (E-P) interaction in 2D perovskites, affects the optoelectronic performance significantly. Here, various optical spectroscopy analyses study the influence of E-P interaction on carrier dynamics for phenethylammonium lead bromide (PEA2PbBr4). Results suggest the strength of E-P interaction is relative to the residual strain of thin films. Moreover, the numerical fitting result of time-resolved photoluminescence (TRPL) shows the reduction in E-P interactions further enhances the recombination process of free excitons.

  Preview abstract

We demonstrated GeSn micro-disk monolithically-integrated on silicon substrate. The introduction of sufficient Sn (~10%) into the GeSn active layer successfully transfer the material into a direct-bandgap material. High-Q micro-disk cavity was fabricated. Under optical pumping, lasing action was achieved with a lasing wavelength of 2201 nm up to 120 K. These developed GeSn micro-disk lasers provide a practical solution for compact light sources for silicon photonics.

  Preview abstract