Gradient refractive index planar microlens in Si using porous silicon

Abstract

Significant effort is being expended on the integration of silicon electronics and optoelectronics. Here the authors describe a method to create planar gradient refractive index (GRIN) lenses in Si using porous silicon (PSi) technology. The authors’ approach allows the fabrication of a single planar lens or an array of such lenses with focal length that can be adjusted to match existing device(s) on the chip. The lenses are transparent in the near IR, including the optical communication window (1.3μm<λ<1.6μm). In addition to being potential components in future Si based integrated optical circuits, PSi GRIN lenses can also be used to improve the light coupling efficiency of existing Si based devices, such as sensors, detectors, and waveguides.