Tunable conducting oxide metasurface color filter

Optoelectronic transducing mechanism provides an unprecedented opportunity to achieve post-fabrication control in metasurface devices. However, there are only few works on electrically controlled metasurface color filters. In this work, we propose a novel color filter structure in which the light transmission can be electrically controlled. The proposed structure is a modified periodic metal-insulator-metal (MIM) configuration with ultrathin layers of indium tin oxide (ITO) and hafnium dioxide (HfO$_{\mathrm{2}})$ sandwiched between two gold nanostrips. When electrically biased the ITO layer changes its optical property due to the electron accumulation at the ITO-HfO$_{\mathrm{2}}$ interface and hence changes dispersion property of the structure. The numerical simulation shows that a high electrical modulation ratio of 20.5 dB of transmission can be achieved around the frequency region where ITO's permittivity is close to zero, known as the epsilon-near-zero (ENZ) point. Moreover, the structure exhibits the maximum resonance shift of 40 nm under the electrical bias of 5 V. The electrical modulated nanoscale color filter can be used in imaging devices and bring new functionalities to cameras or biosensing.