Now, MIT researchers Youwei Yao, Ralf Heilmann, and Mark Schattenburg of the Space Nanotechnology Laboratory (SNL) within MIT's Kavli Institute for Astrophysics and Space Research, as well as recent graduate Brandon Chalifoux Ph.D., have devised new methods to work past this barrier.

In a paper appearing in the April 20 issue of Optica, Yao, a research scientist and the paper's lead author, explains their new approach to reshaping thin plate materials in a way that eliminates distortion and enables researchers to bend surfaces more arbitrarily into the precise and complex shapes they might need. Thin plate shaping is typically used for high-level, complex systems, like deformable mirrors or wafer-flattening processes during semiconductor manufacturing, but this innovation means future production will be more precise, scalable, and cheap. Yao and the rest of the team imagine that these thinner and more easily deformable surfaces can be useful in broader applications, like augmented reality headsets and larger telescopes that can be sent into space at lower cost. "Using stress to deform optical or semiconductor surfaces is not new, but by applying modern lithographic technology, we can overcome many of the challenges of existing methods," says Yao.

The team's work builds on the research of Brandon Chalifoux, who is now an assistant professor at the University of Arizona. Chalifoux worked with the team on earlier papers to develop a mathematical formalism to connect surface stress states with deformations of thin plates, as part of his doctorate in mechanical engineering.

In this new approach, Yao has developed a novel arrangement of stress patterns for precisely controlling general stress. Substrates for optical surfaces are first coated on the backside with thin layers of high-stress film, made of materials like silicon dioxide. Novel stress patterns are lithographically printed into the film so that researchers can change the properties of the material in specific areas. Selectively treating the film coating in different areas controls where stress and tension is applied across the surface. And because the optical surface and the coating are adhered together, manipulating the coating material also reshapes the optical surface accordingly.