Low dispersion, high spectral efficiency, RF photonic transmission systems and low loss grating couplers for silicon -on -insulator nanophotonic integrated circuits

There has been tremendous interest in applying the sophistication present in electrical communication to the field of fiber optic communications. This includes the area of coherent detection, which has eluded optics due to the absence of stable and noise free optical local oscillators. The first half of this dissertation discusses the design and experimental demonstration of high spectral efficiency, low dispersion transmission systems that use the strengths of electrical communication to compensate for areas in which optics is lacking. We propose a system that achieves high spectral efficiency by using microwave filtering to compensate for the slow roll-off in optical filters. We also demonstrate coherent detection without an optical local oscillator, by using microwave photonic mixing rather than all-optical mixing.;The receivers described here use high-performance modulators to perform the function of microwave photonic mixing. Adding such sophistication to optical communications circuits is currently impeded by the cost and complexity of the different optical components that currently exist in diverse material systems. In order to truly exploit the potential of optical functionalities across a broad range of applications, it is essential to realize ultra-compact multi-functional optics on a single platform. Silicon-on-Insulator (SOI) is a material system that shows great promise in this regard. Silicon is ubiquitous in the electronics industry, and processing techniques are well established. The superficial silicon of SOI presents us with a high index contrast layer in which miniaturized optics and electronics could coexist in a high density optoelectronic IC. This could lead to a hybrid photonic/electronic circuit that would be compatible with CMOS technology.;However, the high index contrast system comes with a penalty. The need for single mode optical waveguides in the silicon, requires a waveguiding layer that is 200--300 nm thick. This results in a huge mode mismatch with single mode fiber, precluding the use of simple end-fire coupling to interface the fiber with the nanophotonic chip.;The second half of this dissertation discusses the design, fabrication and characterization of a grating coupler that addresses this problem. A novel design is proposed to enhance coupling efficiency, and a proof-of-concept experiment is performed.