Microwave photonics refers to a field that utilizes light as carrier to process high frequency electrical signals. It has shown great success in both defense and civilian applications. The future applications of microwave photonics demand a dramatic improve in performance while, in the same time, electronic devices should have more favorable features such as small size, lightweight, and low-power consumption. This project proposes to develop a new "Integrated Microwave Photonics chip" which could potentially integrate several functions of microwave photonic components on a single chip and also offer reduced size-weight-and-power at a very low cost. If successful, the developed technology would find tremendous applications in defense systems, such as Radar, and many civilian applications, such as cell phones, sensing, and datacom. The proposed research activities provide comprehensive training for graduate students in the areas of integrated photonics; semiconductor device design, simulation, fabrication, and characterization; as well as in preparation, analysis, interpretation, and dissemination of scientific data and results. The project will be used to recruit undergraduate honor students who may use certain aspects of this research for their thesis. A strong interaction plan with a local Historically Black Colleges and Universities/Minority Institution has been formed to inspire underrepresented minority students to participate research.
Integrated Microwave Photonics (IMWP) incorporates the functions of microwave-photonic components/subsystems in a monolithic or hybrid photonic chip, which offers reduced size-weight-and-power at a very low cost. This project proposes to utilize R-plane sapphire as a transformative, high-performance and self-consistent IMWP platform which provides a feasible approach for realizing fully-integrated MWP systems. The proposed approach enables the integration of complete sets of microwave and optical components such as light sources, analog and digital signal processing circuits, light detectors, control circuits, and Silicon on Sapphire (SOS) radio-frequency (RF) circuits all-in-one sapphire platform to achieve high-performance and low-cost mixed-signal optical links. Sapphire has a lower refractive index with an index difference of 0.3 with Si3N4. Therefore, it could leverage the mature Si3N4 low-loss waveguide technology to produce similar low-loss waveguide-based passive components by drop-in replacing quartz wafers with sapphire wafers. For RF applications, the sapphire platform has a potential to obtain much higher dynamic range due to low-loss optical waveguides while the competing Si-photonics platform combined with off-chip 1.55 micron laser suffers from the strong two-photon absorption and therefore has a limited dynamic range. As a transparent substrate, sapphire would enable a versatile 3-D photonics/electronics integration architecture. This project aims to, first, study the "feasibility" of the proposed approach by identifying and investigating key "fundamental challenges", then, conduct a proof-of-concept study to provide an effective route for overcoming the identified obstacles, and, eventually, provide a conclusive recommendation as to whether the proposed research is feasible. As a fully integrated solution to fundamentally address the most important technical challenge in IMWP, if successful, the new platform would find tremendous applications in defense systems, such as Radar signal processing, and many civilian applications. The broad wavelength coverage enables on-chip sensing applications. It could potentially replace the current Si-photonics for datacom and be used in harsh environments such as space and nuclear applications.
