Cladding-free efficiently tunable nanobeam cavity with nanotentacles.

We propose a cladding-free, efficiently tunable, high-quality factor (Q) nanobeam cavity with subwavelength-period nanotentacles (NT), adequately investigate the performance of the cavity, and study the directional heat transfer. By virtue of the excellent heat transfer of Si nanotentacles, a tuning range of more than 6 nm wavelength, with 24mW and 10 KHz switching rate, and 13 μs raising time is experimentally obtained. This result is about twentyfold better than the previous work by Fegadolli [ACS Photon. 2, 470-474 (2015)]. A potential 12nm tuning range with identical power is also theoretically suggested by modifying the silicon structure. With an optimized design, these nanotentacles are demonstrated to have a minimal effect to the cavity and are available to serve as photonic waveguides. This cladding-free design, with a simple fabrication process, is comparable to other proposals in which deep etching, suspended treatment, and troublesome heterogeneous-integration may be needed. Finally but importantly, this smart design can be applied to other photonic cavities, particularly cavities such as ring/disk resonators, in which we reasonably predict a better tuning efficiency due to the thermal circulation. We believe this design is fairly suitable for applications in which light-matter interaction is of primary importance, such as sensing, particle trapping, cavity quantum electrodynamics (CQED), and III-V/Si hybrid lasers with external cavities.