We developed a novel Etchless fabrication technique which results in low loss waveguides and resonators. This technique defines the structures with selective oxidation, resulting in waveguides and resonators that are never exposed to the etching plasma and have therefore ultra-smooth sidewalls.
Grayscale Lithography
We used grayscale lithography to enable transformation optics on chip. Grayscale lithography, where the dose is modulated so that varying vertical resolutions are achieved, allows us to define graded-index multimode waveguides that have minimal inter-mode coupling.