Arbitrary GRIN component fabrication in optically driven diffusive photopolymers

Abstract

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.

Tuning the refractive index in 3D direct laser writing lithography: towards GRIN microoptics

“…Commonly, GRIN elements are manufactured using well‐known methods: chemical vapor deposition , ion exchange , neutron irradiation , and thermal , UV , and diffusion‐assisted lithography . However, all of them lack the possibility of embodying arbitrary‐shape components, except for a very recent study . In contrast, the TPP technique is distinguished by the unique feature of allowing fabrication of complex‐shape 3D structures including free‐form microoptical elements .…”

Deflectometry for measuring inhomogeneous refractive index fields in two-dimensional gradient-index elements

“…This contribution depends on the quality of interpolation used in obtaining the quantities involved in the integral, namely, d s l;k and θ l;k in Eq. (10) or analogous parameters in similar discrete expressions of Eq. (7) employing higher-order interpolation schemes.…”

“…However, several new methods have been developed (e.g., Ref. [10]) that permit unprecedented control over the index profile in two and three dimensions.…”

Light‐Directed Soft Mass Migration for Micro/Nanophotonics

“…Traditionally, the spatial modulation of the refractive index of a material with microscale and nanoscale precision has been foundational in the development of functional micro/nanophotonic materials and devices. The gradient‐index (GRIN) lens is a representative example . Many other materials and device technologies, including holographic recording media, diffractive surface relief gratings (SRGs), photonic crystal color pixels and sensors, spatial light modulators, and metasurfaces, have undergone significant progress with the recent advances in methods that can control the refractive index of materials with micro and nanoprecision.…”

“…Aside from the concept of metasurfaces, where differently shaped, sized, and oriented antennas made of metals or highly transparent semiconductors are designed to be spatially arranged in a nonperiodic manner for a phase (or refractive index) discontinuity, the bulk refractive index of a homogeneous medium is generally defined by the material density. Accordingly, a spatially modulated density in a homogeneous medium has enabled the development of functional micro/nanophotonic materials and devices . Additionally, for a heterogeneous medium, the spatially controlled separation of different elements, which starkly contrast with each other in terms of their refractive indices, enables an efficient spatial variation in the refractive index .…”