Microwave Photonic Phase Shifters on Nanochips

Abstract

The revolution in microwave technology paralleled by the boom in photonics has led to a convergence of the two fields, and the birth of microwave photonics (MWP). Widely regarded as a prime enabling technology for an array of applications, MWP exerts a powerful impetus to the development of high frequency and large bandwidth signals. The ability to carry out wideband microwave signal processing has inspired a widespread of applications across different branches of knowledge where traditional stand-alone application-specific signal processors may no longer be sufficient to support the exhaustive demand for packing more functions onto one device. The growing emphasis on creating a synergy between these interacting features has continued to blur the lines of functional distinction. This thesis aims to build a connection between various signal processing functionalities to achieve inline processing within the same MWP link. Whilst the development of MWP systems are largely focused on the performance optimization of one specific function, the feasibility of achieving multifunctional MWP system by means of cascading multiple signal processing modules has not been dealt in great depths. One concern with scaling the functionalities is the increase in size and complexity of the system which will deter the economical justification of using bulky photonic devices. To address this challenge, integrated microwave photonics (IMWP) is set to spearhead the future of signal processing, advancing past the electronics age and establishing nanoscale footprint, yet, monumental improvement in performance to facilitate the expansion of complex functionalities which is neither possible with pure electronics nor feasible with discrete bulk optics. In addition, backed by the rising demand for integrated automation systems, the field of integrated sensing is one area that is forecast to witness enormous growth with MWP techniques set to shape the technological progress of high speed optical sensors with high sensitivity and high resolution. The goal of this thesis is not to propose a be-all and end-all method for realizing multifunctional processor, but rather to lay the foundations of achieving scalability, by first exploring integration based approaches for implementing key functionalities, and second, to develop critical modifications to existing systems in order to evoke the potentialities of implementing an inline signal processing system. The concepts presented in this thesis are backed up by theoretical simulations and experimental demonstrations.