Electrically Tunable Plasmonic Absorber Based on Cu-ITO Subwavelength Grating on SOI at Telecom Wavelength

Abstract

An electrically controlled optical absorption is numerically proposed in a plasmonic waveguide on silicon-on-insulator (SOI) consisting of copper-indium tin oxide (ITO) based subwavelength grating at 1.55 µm wavelength. The Cu-ITO subwavelength grating in a form of a discontinuous Cu layer filled with ITO together with electrically tunable permittivity of ITO provides us with a tunable absorption and efficient guidance of plasmonic mode. An n-type ITO is used which exhibits a significant change in the carrier concentration with the applied voltage resulting in a change in optical absorption at a telecom wavelength of 1.55 µm. We numerically observe maximum tuning in absorption at a grating period of 600 nm and a duty cycle of 50%. The proposed device shows a smaller effective mode area of Am = 0.01421/µm2 and a plasmonic confinement factor of 34.67%. The device is reported to have an extinction ratio of 10.28 dB for a 100-µm-long device at a low voltage of 6 V.