Abstract: Silicon-on-insulator (SOI)-based high-speed electro-optic modulators are the key component in optical communication and computing systems.It is necessary to scale down the size of optical waveguides to increase integrity and modulation speed.However,many difficulties will be faced,such as changes in the single-mode conditions,increased transmission loss and coupling loss,and polarization dependence.In this paper,the single-mode conditions of SOI waveguides with different section areas are introduced,and various techniques for dealing with these difficulties are described.Then,a high-speed silicon modulator with a metal-oxide-semiconductor capacitor and a compact silicon modulator with a ring resonator are introduced and analyzed, whose modulation frequencies are as high as 10 and 1.5GHz,respectively.

Key words: silicon-on-insulator, single mode condition, polarization-dependence, transmission loss, coupling efficiency, electro-optic modulator