Semiconductor Waveguides

Abstract

Semiconductor optical waveguides are a very important part of modern integrated optoelectronic systems, especially for electrically active devices. Applications range from semiconductor lasers, optical filters, switches, modulators, isolators, and photodetectors. Semiconductor waveguides have many advantages especially for use in slow light applications. They offer a significant enhancement of interaction length that, to first order, scales with the possible delay. With a tight confinement of the optical mode, the required optical power can be drastically reduced while the mode overlap with the active material is strongly enhanced. The use of semiconductor material is of particular interest since it offers compactness and enables for monolithic integration into optoelectronic devices using well established processing techniques. Furthermore, semiconductors are attractive since the operating wavelength, to a large extend, can be designed while performing with bandwidths in the GHz regime that is well suited for communication signals. Based on III-V, II-VI, or IV-VI group elements, two semiconductors with different refractive indices are generally synthesized for fabrication of optical waveguides. They must have different band gaps but same lattice constant. An attractive feature of the binary compounds is that they can be combined or alloyed to form ternary or quaternary compounds, or mixed crystals, for varying the band gap continuously and monotonically together with the variation of band structure, electronic, and optical properties. The formation of ternary and quaternary compounds of varying band gaps also enables the formation of heterojunctions, which have become essential for the design of high performance electronic and optoelectronic devices. This chapter will give a brief review about fundamental theory, semiconductor materials, and fabrication technologies of various semiconductor waveguides. © Springer International Publishing Switzerland 2014.