Slow-light-assisted electrical tuning in hollow optical waveguide via carrier depletion in silicon and indium tin oxide subwavelength gratings

Abstract

An electrically tunable hollow optical waveguide based on silicon-indium tin oxide (ITO) gratings is proposed to achieve phase modulation. The hollow waveguide consisting of Si-ITO gratings as top and bottom reflectors supports the propagation of slow-light mode with a high group index of 71 and a loss of 0.1 dB/cm in a narrow 1 µm thick air-core at 1550 nm. Carrier depletion in p-type Si and n-type ITO enables electrically controlled phase modulation of the guided slow-light mode. With the slow-light effect, 180◦ phase modulation is obtained in a short device length of 3 mm with a maximum reverse bias of −5 volts and 3 dB modulation bandwidth of 63 GHz. © 2020 Optical Society of America