Optical Modulation in Hybrid Waveguide Based on Si-ITO Heterojunction

An Optical modulator based on a hybrid optical waveguide made up of Silicon and Indium Tin Oxide (ITO) is proposed. The hybrid waveguide is created by the coupling of a leaky optical mode guided in silicon with ITO. The optical modulation is realized with the heterojunction between p-type silicon and n-type ITO. The presence of ITO causes electrical tuning in permittivity and in imaginary-part of the refractive index which provide a way to modulate the intensity of the guide optical mode. The device with Si-ITO heterojunction is fabricated to show intensity modulation at 1.55 mu m wavelength. To achieve an efficient optical modulation the carrier concentration of ITO is optimized by depositing ITO on p-type Si wafer at different oxygen partial pressures using Ion assisted electro-beam deposition. The fabricated device exhibiting an extinction ratio of 7 dB for 1.7 mm long device at low voltage of -5 volts.