A compact and low-driving-voltage silicon electro-absorption modulator utilizing a Schottky diode operating up to 13.2 GHz in C-band

This paper demonstrates a 1 Vpp low-driving-voltage silicon electro-absorption modulator (EAM) utilizing a Schottky diode. Optical modulation using a Schottky diode was achieved through the intensity change of the guiding light due to free-carrier absorption in the semiconductor to change its absorption coefficient, not through conventional interference effects. The proposed EAM consists of a lateral metal-semiconductor junction that helps maximize free-carrier injection and extraction through a Schottky contact on rib waveguide. In order to achieve high-speed operation, traveling-wave type electrodes were designed. The fabricated EAM demonstrates a broad operational wavelength range of 50 nm for C-band with a uniform extinction ratio (ER) of 3.9 dB, even for a compact modulation length of 25 μm with a driving voltage of 1 Vpp. Also, the traveling-wave type electrodes enabled the modulator to operate at up to 26 GHz with 13.2 GHz of 3 dB electro-optic bandwidth experimentally.