Silicon Photonics: Fundamentals and Devices

13.7 Fabrication of Waveguides

A number of materials systems based on silicon have been used for realizing integrated optical waveguides. A description of the various materials systems used by researchers will be given in Section 9. Among all these systems, two different platforms have been widely used to fabricate Si-based waveguides. The first is silica-on-silicon. In recent years, however, SOI (silicon-on-insulator) technology has gained more importance. In this section, we shall briefly describe the technologies involved in fabricating waveguides in these two platforms. The other systems, like SiGe on Si, silicon oxynitride on silica, or amorphous silicon on silica or silicon, will be mentioned in Sections 13.9.2.2, 13.9.2.3, and 13.9.24, respectively.

13.7.1 Silica on Silicon

This structure is perhaps the most widely studied one, and several workers in AT&T Bell Labs and in NTT Laboratories have been engaged in developing useful devices using the grown layers [2, 3] Basically, two different techniques have been employed to realize waveguides in this structure: the flame hydrolysis method and plasma enhanced chemical vapor deposition (PECVD) method. A brief description of each of the processes is given below.

13.7.1.1 Flame Hydrolysis Method

The NTT group developed the waveguides and components by a process known as flame hydrolysis deposition (FHD) [2, 3], which was originally developed for optical fiber fabrication. In this process, SiO₂–GeO₂ waveguides are formed on silicon ...