Combined nano-imprint and photolithography (CNP) of integrated polymer optics

Abstract

We demonstrate wafer-scale fabrication of integrated polymer optics, comprising nm to mm features, by combined nanoimprint and photolithography (CNP). Active and passive polymer optical components are integrated: Distributed feed-back (DFB) polymer dye lasers and polymer waveguides. The laser devices are defined in SU-8 resist, doped with Rhodamine 6G laser dye, shaped as planar slab waveguides on a Si/SiO 2 substrate, and with a 1st-order DFB surface corrugation forming the laser resonator. In the CNP process, a combined UV mask and nanoimprint stamp is embossed into the resist, which is softened by heating, and UV exposed. Hereby the mm to (micron)m sized features are defined by the UV exposure through the metal mask, while nm-scale features are formed by mechanical deformation (nanoimprinting). The UV exposed (and imprinted) SU-8 is crosslinked by a post-exposure bake, before the stamp and substrate are separated, and the un-exposed resist is dissolved. Polymer waveguides are added to the system by an additional UV lithography step in a film of un-doped SU-8, which is spincoated on top of the lasers and substrate. When optically pumped at 532 nm, lasing is obtained in the wavelength range 559 nm - 600 nm, determined by the grating period. Our results, where 20 laser devices are defined across a 10 cm diameter wafer substrate, demonstrate the feasibility of CNP for wafer-scale fabrication of advanced nano-structured active and passive polymer optical components.