Germanium and Silicon Nitride Metasurfaces in Photoenergy Conversions

Silicon photonics technology has been widely applied in communication and data centers. In this work, we experimentally demonstrate a special class of true bound state in the continuum (BIC), lattice resonance, and Kerker effect in group IV metasurface, including Si-based semiconductor and germanium (Ge). The photodetection in silicon photonics has become the very important research area. In silicon photonics, germanium (Ge) is an ideal candidate for on-chip photodetection due to the small bandgap of 0.66 eV and the compatibility with the modern CMOS technology. It has widely been used in near infrared (NIR) photodetection. However, the bulky and thick Ge film for photodetector limits the development of system minimization. By the design of metasurface, the absorption in thin Ge metasurface could have much larger absorption than the pure Ge thin-film. In addition, we also present directional emission normal to Si3N4 BIC metasurface laser with hybrid surface lattice resonances (SLRs).