Liquid deposition photolithography for the fabrication of gradient index (GRIN) micro-optics

One photon diffusive photopolymers enable self-developing three dimensional (3D) refractive index patterning of up to cm thick solid volumes for the fabrication of micro-optics. However, one photon absorption in solid, thick materials does not yield complete control of the 3D refractive index distribution due to diffraction and the excessive development time for index features measuring 100’s of microns in diameter or larger. We present a fabrication method and photopolymer formulation that can efficiently create mm3 optical devices with programmable, gradient index of refraction with arbitrary feature size and shape. Index contrast of 0.1 is demonstrated, which is 20 times larger than commercial holographic photopolymers. Devices are fabricated by repetitive micro-fluidic 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 as the number of layers is increased, reducing the fabrication time for high axial resolution micro-optics. We demonstrate the process by fabricating thick waveguide arrays and gradient index lenses.