Phys.org May 26, 2023
Compared to metasurfaces composed of the periodic arrangement of nanoparticles, inverse membrane metasurfaces offer unique possibilities for supporting multipolar resonances, while maintaining small unit cell size, large mode volume and high field enhancement for enhancing nonlinear frequency conversion. An international team of researchers (UK, Australia, China, Hong Kong) theoretically and experimentally investigated the formation of bound states in the continuum (BICs) from silicon dimer-hole membrane metasurfaces, and demonstrated that BIC-formed resonance featured a strong and tailorable electric near-field confinement inside the silicon membrane films. They showed that by tuning the gap between the holes, it is possible to open a leaky channel to transform the regular BICs into quasi-BICs, which could be excited directly under normal plane wave incidence. They demonstrated the conversion of an infrared image to the visible range, based on the third-harmonic generation (THG) process with the resonant membrane metasurfaces. According to the researchers their work holds promise for extending the applications of nonlinear structuring surfaces to new types of all-optical near-infrared imaging technologies… read more. Open Access TECHNICAL ARTICLEÂ
The schematic of THG imaging based on Si membrane metasurfaces… Credit: Compuscript Ltd