title: Implementation of a graded-index medium by use of subwavelength structures with graded fill factor.
abstract: We present a novel configuration for the implementation of subwavelength-based graded-index devices. The proposed concept is based on the etching of one-dimensional subwavelength gratings into a high-index slab waveguide to achieve the desired effective index distribution. A graded-index profile can be achieved by gradually modifying the duty ratio of the grating along the horizontal axis, while the beam is confined in the vertical direction by the slab waveguide. On the basis of this concept, novel graded-index lenses and waveguides are both proposed and characterized numerically by use of finite-difference time-domain and finite-element analysis. The proposed devices can be used for guiding, imaging, optical signal processing, mode matching, coupling, and other applications while offering the intrinsic advantages of on-chip integration such as miniaturization, eliminating the need to align each component separately, and compatibility with standard microfabrication techniques for manufacturability.
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0407, USA. ulevy@ece.ucsd.edu
authors.forename: Uriel
authors.initials: U
authors.lastname: Levy
authors.forename: Maziar
authors.initials: M
authors.lastname: Nezhad
authors.forename: Hyo-Chang
authors.initials: HC
authors.lastname: Kim
authors.forename: Chia-Ho
authors.initials: CH
authors.lastname: Tsai
authors.forename: Lin
authors.initials: L
authors.lastname: Pang
authors.forename: Yeshaiahu
authors.initials: Y
authors.lastname: Fainman