Bandwidth-tunable optical spatial filters with nanoparticle arrays

Modeling a nanoparticle array (NPA) inside a thin glass slab as a lumped optical resonator, we propose a systematic approach to design for an efficient optical filter with bandwidth tunability. The quality factor and bandwidth of the resonator are related to the physical, geometrical, and electrical parameters of an NPA and its surrounding medium, whose permittivity is varied to change the bandwidth. We propose a structure amenable to our design approach consisting of an NPA slab surrounded by liquid crystal whose permittivity can be altered. We validate the design procedure with examples of tunable-bandwidth filters at different frequency regimes from NIR to blue.