The goal of this project is to develop a new class of photonic circuits and devices of large complexity, in which disorder can be harnessed and controlled, for use as reconfigurable optical buffers, switches, and wavelength converters. These silicon-based Anderson's devices will comprise hundreds of individual elements, such as resonators, couplers, sequential taps etc. Such large circuits represent an orders-of-magnitude advance in complexity from the state-of-the-art, and necessitate careful attention to the effects and remedies of disorder induced by imperfect lithography or computational limitations in the design process.
Intellectual merit: The major challenge addressed by this proposal is how to design for, test and demonstrate photonic devices which can withstand and even utilize disorder. The key of our approach lies in utilizing disorder for useful behavior, such as dynamically-controlled Anderson localization of light, or ultra-low energy nonlinear optical switching. This project may help bridge the gap between optical device engineering and condensed matter physics, and advance our understanding of the cooperative behavior of photons in lithographically patterned structures. These devices can be used for packet-length switches, delay lines, and a novel "Anderson optical memory".
Broader impact: The PI commits during this project to support the mentoring and career-development of a post-doctoral researcher. Educational activities include development of a new special-topics graduate-level course for which course materials will be prepared and made freely available on the internet, the PI will work on a textbook on Micro-resonators, and opportunities will be provided for interdisciplinary education and training of underrepresented groups.
The main goal and outcome of this project was to develop a new class of silicon-based photonic circuits and devices of large complexity, in which disorder is normally manifest as a crippling limitation, but with appropriate insights and design, disorder can be mitigated, controlled or even harnessed for functionality. These circuits comprised multiple optical waveguiding elements (resonators, couplers, waveguides, etc.) and electronic control elements (diodes, metal contacts, etc.) through which an experimentalist can modify the propagation of light even in the regime where disorder dominates the performance of the device. The intellectual merit of our work was that such control had not been demonstrated before, and our research may enable a new class of devices which can overcome some of the effects of disorder which can otherwise not be ignored because of fundamental mathematical arguments related to Anderson localization. Also of importance to us was to develop a deeper understanding of possible fabrication remedies for disorder induced by imperfect lithography. If nanoscale disorder can be corrected, device performance may be improved, and we demonstrated this functionality with record-level precision in research reported during our project. Our method was based on field-induced local oxidation via a chemical reaction near an electrically-biased conducting atomic-force microscope tip ("etch-a-sketch" nano-photonics). Our work also had benefits for other technological areas, e.g., by understanding what are the main problems associated with disorder in microring filters, we were able to design a compact chip-scale optical filter which demonstrated record performance. When studying the disorder properties of a certain class of devices in detail, we were able to show that spectral correlations can be beneficial for some applications, leading to our demonstration of correlated photon pair creation in the regime of quantum optics. Among the broader impacts of this project, the work of five graduate students, two undergraduates and one post-doctoral scholar (among which are two women) was greatly benefitted. Our project was a single investigator grant, which became an three-way interaction between a university, an industrial partner (IBM) and a government lab (NIST), via a GOALI supplement and under the NSF-NIST collaboration program. This was an active and close three-way collaboration, with frequent visits by our students to both sites, and regular involvement by the relevant personnel at IBM and NIST. Both of these opportunities were highly valuable to the students as well as the researchers from all three organizations. There was also a collaboration with an overseas scientific organization for device fabrication, which is one of the most costly aspects of optoelectronics research.