Field localization control in aperture-based plasmonics by Boolean superposition of primitive forms at deep subwavelength scale

Abstract

Aperture-based nanoplasmonics deals with an important class of structures with subwavelength hole arrays that support surface plasmons polaritons, thus ensuring control over propagation and localization of electromagnetic fields. The electromagnetic field localization in aperture-based plasmonic structures can be tailored by modifying the structure geometry at the deep subwavelength scale, in this way generating field hotspots in a controlled way. We defined subwavelength primitive objects and combined them in Boolean manner by applying logical operations like AND or OR to their shapes to generate complex forms and thus modify the subwavelength unit cell geometry. We designed our structures and simulated their scattering parameters by the finite element method and fabricated the experimental samples for the mid-wavelength infrared range using the conventional silicon-based planar technologies with gold and aluminum as plasmonic materials. We show that one can readily use the conventional, non-subwavelength photolithography to generate strong field nonlocalities without increasing the complexity of the system or requiring finer resolutions. The approach can be used for multispectral operation of plasmonic chemical or biological sensors.