A Review of Silicon-Based Integrated Optical Switches

Recently, silicon-integrated optical circuits have attracted intensive interests, thanks to the compatibility with the complementary metal-oxide-semiconductor (CMOS) technology that enables mass production at low cost. The optical switch is an essential part of optical integrated circuits, with broad applications in optical communications and networks, optical computing, and sensing such as LiDAR. In general, the silicon-integrated optical switch adopts thermo-optic or carrier dispersion effect to realize reconfigurable signal routing. However, the use of thermo-optic effect leads to high power consumption, and the carrier dispersion effect has the disadvantage of small refractive index change. In addition, both effects are non-latching, and hence, continuous power consumption is required even when switching is not needed. For overcoming these drawbacks, phase-change materials (PCMs) have been introduced into silicon-integrated optical switches. In this paper, silicon-integrated optical switches are classified according to the underlying structure and recent research is reviewed. Recent studies on silicon-integrated optical switches incorporating PCMs are also reviewed. Furthermore, the pros and cons of different types of integrated optical switches with and without PCMs are compared and discussed.