Surface plasmon resonance (SPR) is often taught as a “thin-film thickness problem”: adjust the metal thickness, add a dielectric overlayer, and the reflectance dip shifts. In practice, thickness is a relatively blunt instrument. Once you start adding anisotropic layers—birefringent dielectrics, columnar films, liquid-crystal-like coatings, 2D crystals with in-plane anisotropy, or engineered metamaterial layers—the resonance can […]
