Plasmonic Broadband Filters via Fourier Surface Modulation

It remains a significant challenge to achieve broadband and polarization-independent performance optical filtering for integrated photonics. In this work, we propose and experimentally validate a type of plasmonic broadband filter via Fourier surface modulation (BFFSM), realized by superimposing sinusoidal gratings on an Al–UV curing adhesive–SiO2 structure. By enabling spatial frequency multiplexing, our design facilitates coherent coupling of multiple surface plasmon polariton modes, which can significantly broaden the reflection dip without added structural complexity. Experimental results confirm that the one-dimensional BFFSM achieves a reflection bandwidth of 49 nm, which is 2.7 times wider than that of conventional single-period gratings. When extended to two-dimensional square and hexagonal configurations, they further enhance the polarization robustness with minimal reflectance over polarization angles between 0 and 90°. Moreover, the wide bandwidth property is also well preserved within the incidence angles from 20 to 45°. Fabricated via wafer-scale nanoimprint lithography, the BFFSM offers high fidelity, scalability, and compatibility with cost-effective manufacturing. This work establishes a new route to realize broadband filters featuring novel properties, robust performance, and easy fabrication, which are promising for wide applications.