Design, fabrication and characterization of ultrasmall SOI-based integrated photonics devices

The photonics research community is slowly converging towards a novel optical platform and materials system for future integrated optical devices. Although several candidates are presently proposed, i.e., III-V semiconductors, polymers, silica, organics, none have been as tempting as silicon. The reason for this is that silicon is the materials system-of-choice for the electronics industry, with a mature CMOS fabrication and processing tool base. The fact that it is also compatible with optics and photonics makes it highly attractive. Monolithic integration of both optics and electronics in a common substrate would be the technological holy grail. Unfortunately, silicon has some major drawbacks; namely, it is a highly inefficient active substrate because of its indirect bandgap. Sources, detectors, and modulators are generally thought of as impossible to achieve in this platform. However, recently exceptional work in silicon nanophotonics research has given hope to the contrary. Sources based on erbium doping, detectors using silicon germanium, and modulators employing the thermooptic and the free carrier dispersion effects have been built and show promising performance. Therefore, the work that must be done at this juncture is the validation of silicon as a novel materials system for the advancement of nanophotonics research. In particular, achieving a library of optical functionalities and subsequent integration into a prospective system must be performed.; In this thesis, the design, fabrication, and characterization of photonic integrated devices in silicon-on-insulator (SOI) are studied. SOI is an attractive materials system for such devices because of its inherent high-index-contrast (Deltan), which enables the miniaturization and high-density packing of optical components. The compatibility with CMOS electronics also offers the possibility for monolithic integration of optoelectronic systems-on-a-chip (SoCs). The focus of this thesis is in achieving new optical functionalities in silicon.; An essential first step in this work involved the design of devices using numerical simulation tools. Through the use of the beam propagation method (BPM) and the finite difference time domain (FDTD), a viable device design was achieved and excellent predictions on device functionality and performance were obtained. The second important step involved conventional semiconductor micro- and nanofabrication and processing of the devices, with the emphasis on studying and optimizing key processing steps to obtain low sidewall roughness and, hence, low waveguide propagation losses. (Abstract shortened by UMI.)...