Large-Area Low-Cost Plasmonic Perfect Absorber Chemical Sensor Fabricated by Laser Interference Lithography

We employ laser interference lithography as a reliable and low-cost fabrication method to create nanowire and nanosquare arrays in photopolymers for manufacturing plasmonic perfect absorber sensors over homogeneous areas as large as 5.7 cm(2). Subsequently, we transfer the fabricated patterns into a palladium layer by using argon ion beam etching. Geometry and periodicity of our large-area metallic nanostructures are precisely controlled by adjusting the interference conditions during single- and double-exposure processes, resulting in active nanostructures over large areas with spectrally selective perfect absorption of light from the visible to the near-infrared wavelength range. In addition, we demonstrate the method's applicability for hydrogen detection schemes by measuring the hydrogen sensing performance of our polarization independent palladium-based perfect absorbers. Since palladium changes its optical and structural properties reversibly upon hydrogenation, exposure of the sample to hydrogen causes distinct and reversible changes within seconds in the absorption of light, which are easily measured by standard microscopic tools. The fabricated large-area perfect absorber sensors provide nearly perfect absorption of light at 730 and 950 nm, respectively, and absolute reflectance changes from below 1% to above 4% in the presence of hydrogen. This translates to a relative signal change of almost 400%. The large-area and fast manufacturing process makes our approach highly attractive for simple and low-cost sensor fabrication, and therefore, suitable for industrial production of plasmonic devices in the near future.