Microwave Photonic Signal Processing Using On-Chip Nonlinear Optics

Abstract

The field of microwave photonics (MWP) emerged as a solution to the challenges faced by electronic systems when dealing with high-bandwidth RF and microwave signals. Photonic devices are capable of handling immense bandwidths thanks to the properties of light. MWP therefore employs such devices to process and distribute the information carried by RF and microwave signals, enabling significantly higher capacity compared to conventional electronics. The photonic devices traditionally used in MWP circuits have mainly comprised bulky components, such as spools of fibre and benchtop optical amplifiers. While achieving impressive performance, these systems were not capable of competing with electronics in terms of size and portability. More recently, research has focused on the application of photonic chip technology to the field of MWP in order to reap the benefits of integration, such as reductions in size, weight, cost, and power consumption. Integrated MWP however is still in its infancy, and ongoing research efforts are exploring new ways to match integrated photonic devices to the unique requirements of MWP circuits. This work investigates the application of on-chip nonlinear optical interactions to MWP. Nonlinear optics enables light-on-light interactions (not normally possible in a linear regime) which open a vast array of powerful functionalities. In particular, this thesis focuses on stimulated Brillouin scattering, resulting from the interaction of light with hypersonic sound waves, and four-wave mixing, where photons exchange energies. These two nonlinear effects are applied to implement MWP ultra-high suppression notch filters, wideband phase shifters, and ultra-fast instantaneous frequency measurement systems. Experimental demonstrations using integrated optical waveguides confirm record results