Title: "In-Chip Volumetric Gradient Index Photonics"
Speaker: Lynford Goddard, Associate Dean for Diversity, Equity, & Inclusion and Director, Institute for Inclusion, Diversity, Equity, and Access (IDEA), The Grainger College of Engineering, Edward C. Jordan Professor, Electrical and Computer Engineering, University of Illinois Urbana Champaign.
Silicon photonics is a mature technology with many foundries worldwide. Photonic integrated circuits (PICs) are mass manufactured by patterning devices on the surface of the silicon wafer. Although great circuit functionality can be achieved, the architecture is limited to two-dimensional binary structures with fixed refractive index contrast. Recently, in collaboration with the research groups of Paul Braun and Kimani Toussaint at the University of Illinois, we developed a new three-dimensional direct laser writing technique called Subsurface Controllable Refractive Index via Beam Exposure (SCRIBE). This lithographic approach enables submicron control of the local refractive index over a continuous range of greater than 0.3 by controlling the fill fraction of photoresist inside nanoporous silicon and silica scaffolds. Utilizing SCRIBE’s unprecedented index range and 3D writing accuracy, we demonstrated novel volumetric micro-optic and photonic elements including 3D waveguides and microring resonators, compound achromatic lenses, planar axicons, photonic nanojet generators, variable-color distributed Bragg reflectors, and the world’s smallest (15 µm diameter) spherical Luneburg lens. In this talk, I will explain the method, present device results, and discuss some potential applications enabled by this paradigm shifting architecture.
