Fabrication of ultra-compact photonic components in semiconductors

As optical communication becomes ubiquitous, the demand for smaller photonic devices for large-scale integration is expected to grow. Unlike electronics, where silicon has been virtually uncontested as the material of choice, no clear winner has emerged for optoelectronics as far as the choice of material system is concerned. Although fused silica-based optical fibers have fared relatively well so far for long-haul communications, neither silica nor any single material is suitable for every application. As a result, various II-VI, III-V and type IV semiconductors, myriad polymers and multitudes of ferrorelectrics are being used for signal routing, signal splitting, switching, modulation, wavelength conversion, multiplexing and demultiplexing.; This thesis explores the feasibility and develops the fabrication technology of novel semiconductor-based integrated optical devices. A fabrication technology on ultra-compact devices on GaSb-based semiconductors has been developed for their use in various mid-infrared applications. Although no integrated optical devices on GaSb, per se, were described in thesis, the processes developed here can easily be adapted for photonic integrated circuit fabrication in various III-V-based semiconductors.; The thesis deals extensively with the design and fabrication on high refractive-index-contrast systems, such as silicon-on-insulators (SOI). In addition to being one of the strongest candidates for integration with conventional electronics, SOI materials can also take advantage of its well established fabrication technique. Moreover, we are among the first to point out that the use of a thin Si on a relatively thick Si0₂ can be utilized to significantly reduce the size of the integrated optical device.; The feasibility of this concept was shown with the design and fabrication of ultrasmall bends, sputters and multimode interference-based devices. All the devices fabricated here are the smallest of their kinds fabricated to date in any material system using traditional integrated optics. The results presented here are expected to lead to further emphasis on high-index-contrast systems in general, and SOI in particular, in the quest for hybrid, high-density and highly efficient planar photonic integrated circuit.