We introduce a maskless lithography tool and optically-initiated diffusive photopolymer that enable arbitrary two-dimensional gradient index (GRIN) polymer lens profiles. The lithography tool uses a pulse-width modulated deformable mirror device (DMD) to control the 8-bit gray-scale intensity pattern on the material. The custom polymer responds with a self-developing refractive index profile that is non-linear with optical dose. We show that this nonlinear material response can be corrected with pre-compensation of the intensity pattern to yield high fidelity, optically induced index profiles. The process is demonstrated with quadratic, millimeter aperture GRIN lenses, Zernike polynomials and GRIN Fresnel lenses.

Photonic devices increasingly require three-dimensional control of refractive index, but existing fabrication methods such as femtosecond micromachining, multilayer lithography and bulk diffusion can only address a select scale range, are often limited in complexity or thickness and have low throughput. We introduce a new fabrication method and polymeric material that can efficiently create mm 3 optical devices with programmable, gradient index of refraction with arbitrary feature size. Index contrast of 0.1 is demonstrated, which is 100 times larger than femtosecond micromachining, and 20 times larger than commercial holographic photopolymers. This is achieved by repetitive microfluidic layering of a self-developing photopolymer structured by projection lithography. The process has the unusual property that total fabrication time for a fixed thickness decreases with the number of layers, enabling fabrication 10 5 faster than femtosecond micromachining. We demonstrate the process by sequentially writing 100 layers to fabricate a mm thick waveguide array.

A general strategy for characterizing the reaction/diffusion kinetics of photopolymer media is proposed, in which key processes are decoupled and independently measured. This strategy enables prediction of a material's potential refractive index change, solely on the basis of its chemical components. The degree to which a material does not reach this potential reveals the fraction of monomer that has participated in unwanted reactions, reducing spatial resolution and lifetime. This approach is demonstrated for a model material similar to commercial media, achieving quantitative predictions of refractive index response over three orders of exposure dose (~1 to ~10 3 mJ cm −2) and feature size (0.35 to 500 μm).

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