Generalized optical spatial filter design with unequal inverter impedances

We present a generalized method for synthesizing optical spatial filters composed of arrays of periodic nanoparticles (NPs). The synthesis is based on the equivalent circuit of the nanoparticle arrays (NPAs), and uses unequal impedance inverters to construct a spatial filter in which input, output, and inverter layers´ materials can be different providing more degrees of freedom in the filter design procedure. We validate the synthesis procedure with a design example of an optical spatial filter with second-order Chebyshev bandstop response.