Accessible, All-Polymer Metasurfaces: Low Effort, High Quality Factor

Optical metasurfaces supporting resonances with high quality factors offer an outstanding platform for applications such as nonlinear optics, light guiding, lasing, sensing, light-matter coupling, and quantum optics. However, their experimental realization typically demands elaborate multistep procedures such as metal or dielectric deposition, lift-off, and reactive ion etching. As a consequence, accessibility, large-scale production, and sustainability are constrained by reliance on cost-, time-, and labor-intensive facilities. We overcome this fabrication hurdle by repurposing poly(methyl methacrylate), which is usually employed as a temporary resist, as the resonator material, thereby eliminating all steps except for spin-coating, exposure, and development. Because the low refractive index of the polymer limits effective mode formation, we present a bilayer recipe that enables the convenient fabrication of a freestanding membrane to maximize the index contrast with its surroundings. Since etching induced defects are circumvented, the membrane features high quality nanopatterns. We further examine the suspended membrane with scanning electron microscopy and extract its position-dependent spring constant and pretension with nanoindentation experiments applied with the tip of an atomic force microscope. Our all-polymer metasurface hosting bound states in the continuum experimentally delivers high quality factors (up to 523) at visible and near-infrared wavelengths, despite the low refractive index of the polymer, and enables straightforward geometry-based tuning of both line width and resonance position. We envision this methodology to facilitate accessible, high performance metasurfaces with specialized use cases such as material blending, angled writing, and mechanically based resonance tuning.