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

TL;DR

This paper introduces an accessible method to create high-quality all-polymer optical metasurfaces using simple fabrication steps.

Contribution

The novel contribution is using poly(methyl methacrylate) as a resonator material to simplify metasurface fabrication.

Findings

The all-polymer metasurface achieves high quality factors up to 523 at visible and near-infrared wavelengths.

The fabrication method eliminates complex steps like etching and uses spin-coating, exposure, and development.

Nanoindentation experiments reveal the mechanical properties of the suspended polymer membrane.

Abstract

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.

Figures