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Structured Gradient Index Lenses

Figure 1. Differential interference contrast micrograph of a 1 mm thick polymer GRIN lens array. Each lenslet is formed by a single exposure with an approximately quadratic light intensity. The array is formed by stepping and repeating the exposure on a precision stage.
A diffusive photopolymer can be programmed with a desired gradient refractive index pattern using a raster scanned laser or an analog spatial light modulator to implement customized optical elements that are not possible with traditional processes. We have developed fabrication and metrology tools to create lithographyically-structured gradient-index lenses on the sub-mm to cm scale. These lenses can implement unusual optical functions, correct for optical aberrations or be fabricated in arbitrary arrays via step-and-repeat lithography. These lenses are particularly useful for in-vivo medical imaging due to their capabilities of direct fiber coupling, small size and tailored optical response.
Quantative index measurment of a single GRIN lens obtained by scanning differential transmission microscopy. The profile is parabolic, implementing a traditional GRIN lens.
Simulated index profile from a custom design tool. The design is for a Zernike (3,-1) polynomial, demonstrating the capability of making arbitrary phase functions, in this case for aberration correction.
This design file to the left was printed on a raster-scanning direct-write lithography tool that uses a 2D galvanometer scanner to fabricate the structure in approximately one second. The image is a DIC microphotograph of the result.

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This work has been generously funded by: