Integrated Photonics Structure for THz Systems Based on Silicon and Photoconductive Material

The field of terahertz (THz) technology has been immensely progressed over the past two decades, but integrated on-chip THz circuits and systems are still under development. This thesis is an effort to propose an integrated THz system by trapping a generated photocurrent THz wave and its coupling to the waveguide for on-chip propagation and processing. The proposed system consists of three parts; an optically-excited photoconductive THz source based on low-temperature grown (LT)-GaAs, a photonic crystal nanobeam cavity for THz wave confinement, and its coupling to a waveguide, both are based on a silicon platform. The thesis first investigates how the THz signal is generated by the photomixing techniques. It presents an analytical model to calculate the time-varying photocurrent acting as a THz source. Considering the THz dipole current exciting a cavity, I propose a photonic crystal nanobeam cavity inside a waveguide with high quality factor to confine the THz wave. The design and simulation of such a cavity are presented where the THz field mode has been found in a single-mode regime. Finally, the cavity is coupled to the waveguide using a tapering technique in the photonic crystal structure for efficient coupling and subsequent propagation by modal field matching. The proposed structure exhibits potential applications for integrated THz sources for various on-chip applications such as sensing, spectroscopy, and signal processing.