Biomimetic Gradient Index (GRIN) Lenses

A new class of hierarchically structured polymer optical materials possessing an internal refractive index gradient that mimics biological optical materials is described. The new materials permit the fabrication of gradient refractive index (GRIN) lenses with an unprecedented variety of index gradients. Gradients with different functional forms in both the radial and axial directions have been fabricated. Materials with gradients with a Δn ~ 0.17 have been made, and larger index ranges are possible. Flat GRIN lenses and shaped lenses with specified internal index gradients have been fabricated from the new materials. The new polymer materials show promise for use in optical systems that have fewer, lighter lenses than traditional lens systems. They encourage the exploration of new paradigms for bio-inspired optical designs that could not be implemented by using homogeneous lens materials. The fabrication of practical GRIN polymer optical materials involved a series of advances. The first was the recognition that a transparent polymer film with a specified refractive index could be fabricated using nanolayer polymer extrusion technology. The nanolayered films are stacked to create a material with an index gradient defined by the order in which the different nanolayered films are stacked. The stacking order, and thus the gradient, can be defined as desired. These materials are then molded into the GRIN lenses. To take advantage of the ability to construct a specific index gradient in a shaped lens, an optimum index gradient for such lenses had to be designed. These new materials facilitate the application of GRIN optics to a variety of optical systems and devices. They support the development of bio-inspired lenses and optical systems. The wide range of lens shapes and index profiles that can be fabricated gives an optical designer substantial control over the focal properties of each lens.