"Today, silicon photonics, the technology for building low-cost and complex optics on a chip, is a thriving community and a blossoming business. The roots of this promising new technology date back to the late 1980s and early 1990s to the work of Soref, Peterman, and others. There were three early findings that paved the path for much of the subsequent progress. First, it was recognized that micrometer-size waveguides, compatible with the CMOS technology of the time, could be realized despite the large refractive index difference between silicon and silicon dioxide (SiO2). Previously, this large refractive index was thought to result in multimode waveguides that are undesirable for building useful interferometric devices such as directional coupler, Mach-Zehnder modulators, and so on. Although, today's submicron (nanophotonic) waveguides are routinely realized and desired for their more efficient use of wafer real estate, the advance fabrication capability needed to fabricate such structures was not widely available to photonic device researchers. Second, it was proposed by Soref that by modulating the free-carrier density, which can be done easily with a diode or a transistor, electro-optic switching can be achieved through the resulting electroabsorption and electrorefraction effects. Third, it was shown that infrared photodectors operating in the telecommunication band centered at 1550 nm can be monolithically integrated onto silicon chips using strained layer GeSi (and eventually Ge) grown directly on silicon. The potential for creating low cost photonics using the silicon CMOS chip manufacturing infrastructure was gradually recognized by the photonics research and business community in the late 1990s and early 2000s"-- Provided by publisher.