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.
Highlights
Gradient index (GRIN) lenses and micro-optics are important devices in photonics and optoelectronics because they offer appealing form factors, simplified mounting and packaging for many applications, and additional degrees of freedom in lens design, enabling aberration or lens element reduction
The fidelity was quantified by comparing the point spread function (PSF) at the focal plane, Fig. 4(c), and the lens phase profile, Fig. 4(a), to the simulated performance of a GRIN lens with an ideal phase profile, shown in Fig. 4(b) and (d)
We have presented a method to fabricate arbitrary GRIN optics by patterning optically driven diffusive photopolymer media with a projection gray-scale maskless lithography instrument
Summary
Gradient index (GRIN) lenses and micro-optics are important devices in photonics and optoelectronics because they offer appealing form factors, simplified mounting and packaging for many applications, and additional degrees of freedom in lens design, enabling aberration or lens element reduction. Ricated by laminating nanometer thick polymer sheets with controllable refractive index together [6] This technique is limited to producing high quality axial GRIN and has not demonstrated index modulation transversely. The underlying physical principle of these methods limits their ability to fabricate high fidelity transverse GRIN lenses with arbitrary index profiles To overcome this limitation we propose and demonstrate a new form of GRIN lens fabrication that can print complex parts with optical control over the refractive index profile. This method utilizes optically driven diffusive photopolymers illuminated by a deformable mirror device (DMD) and a light emitting diode (LED). In addition to greater control over the refractive index profile, this fabrication method and material improves upon previous work [10] by significantly reducing scatter in the sample, improving the optical clarity throughout the entire visible spectrum and improving the environmental stability by increasing the glass transition temperature of the material by 50 ◦C
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