Multi-element, multi-frequency lens transformations enabled by optical wavefront matching

Transformation optics (TO) has brought forth a renewed interest in gradient-index (GRIN) optics due to its ability to allow arbitrary geometries to electromagnetically mimic the behaviors of more conventional structures via a spatially-inhomogeneous refractive index profile. While quasi-conformal transformation optics (qTO) has seen great success at microwave and RF frequencies, it is inherently limited to single frequency transformations: an immediate shortcoming for designs in the optical regime. Also, achieving desirable solutions from multi-element transformations is difficult for qTO. To overcome these challenges, a multi-component multi-frequency lens transformation procedure based on the wavefront-matching (WFM) design methodology is presented. Finally, the procedure is applied to a number of optical systems to advocate its efficacy as a more general transformation method.