SURFACE PLASMON RESONANCE IMAGING OF METASURFACES PATTERNED VIA PYRAMIDIAL INTERFERENCE LITHOGRAPHY

Abstract

This study successfully demonstrates, for the first time, surface plasmon resonance (SPR) imaging of plasmonic metasurfaces using the pyramidal interference lithography (PIL) technique. The research focuses on designing, simulating, fabricating, and characterizing metasurfaces with various rotational symmetries. To accomplish this, azobenzene-based thin films were spin-coated onto glass substrates and patterned using PIL, employing pyramids with 3, 4, 6, and 8 faces to generate metasurfaces with corresponding rotational symmetries. Python-based simulations of multi-beam interference were employed to visualize pattern formations that closely resembled the experimental results from PIL. SPR spectrometry revealed distinct plasmonic responses for each metasurface, with observed deviations in SPR wavelengths and pitch values generally within a 10% margin of expected values. Notably, metasurfaces with 6-fold symmetry demonstrated excellent accuracy in the infrared range, with deviations of less than 1%. The study also introduces a dualpyramid setup capable of generating larger pitch sizes suitable for infrared SPR measurements. In addition, this work developed a lens-pyramid system capable of fabricating metasurfaces with a range of periodicities and demonstrated its capability to achieve this on the micron scale. Overall, this work establishes PIL as a viable technique for fabricating plasmonic metasurfaces that can be imaged through SPR and supports the continued development of SPR imaging and sensing platforms.