Electrically tunable metasurface for dual-band spatial light modulation using the epsilon-near-zero effect

Electro-tunable metasurfaces have attracted much attention for the active control of incident light at the nanoscale by engineering sub-wavelength meta-atoms. In this Letter, for the first time, to the best of our knowledge, a grating-assisted dual-band metasurface for spatial light modulation is reported that can operate in two crucial telecommunication wavelength bands, i.e., C-band and O-band. The proposed device consists of a silicon-nitride nanograting on top of a silicon-indium-tin-oxide (ITO)-alumina-gold stack. Effective medium theory combined with a modal analysis is used to study the guided-mode resonance dips at 1.55 mu m and 1.31 mu m in the reflectance spectra. We leverage the epsilon-near-zero effect of ITO by applying an external bias voltage to introduce large modal loss, which leads to the disappearance of the resonance dips at those wavelengths. We obtain a high modulation depth of similar to 22.3 dB at 1.55 mu m and similar to 19.5 dB at 1.31 mu m with an applied bias of -4V and -5V, respectively. Thus, the proposed metasurface may help to realize dual-band active nanophotonic devices. (c) 2022 Optica Publishing Group

Automated summary

In this Letter, a grating-assisted dual-band metasurface for spatial light modulation is proposed, which can operate at specific wavelengths in the C-band and O-band. By leveraging the properties of the silicon-nitride nanograting and the silicon-indium-tin-oxide (ITO)-alumina-gold stack, the reflectance spectra can be modulated at 1.55 mu m and 1.31 mu m wavelengths. This metasurface may offer potential applications in the development of dual-band active nanophotonic devices.