title: Transformation inverse design.
abstract: We present a new technique for the design of transformation-optics devices based on large-scale optimization to achieve the optimal effective isotropic dielectric materials within prescribed index bounds, which is computationally cheap because transformation optics circumvents the need to solve Maxwell's equations at each step. We apply this technique to the design of multimode waveguide bends (realized experimentally in a previous paper) and mode squeezers, in which all modes are transported equally without scattering. In addition to the optimization, a key point is the identification of the correct boundary conditions to ensure reflectionless coupling to untransformed regions while allowing maximum flexibility in the optimization. Many previous authors in transformation optics used a certain kind of quasiconformal map which overconstrained the problem by requiring that the entire boundary shape be specified a priori while at the same time underconstraining the problem by employing "slipping" boundary conditions that permit unwanted interface reflections.
authors.affiliation: Department of Physics, MIT, Cambridge, MA 02139, USA. daveliu@mit.edu
authors.forename: David
authors.initials: D
authors.lastname: Liu
authors.forename: Lucas H
authors.initials: LH
authors.lastname: Gabrielli
authors.forename: Michal
authors.initials: M
authors.lastname: Lipson
authors.forename: Steven G
authors.initials: SG
authors.lastname: Johnson
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008027:Light; D008962:Models, Theoretical; D055096:Optical Devices; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance / Q000295:instrumentation*