structurally chiral

In the Kretschmann configuration, the bulk metal is in the form of a thin film of uniform thickness, bounded on one side by a high–refractive–index dielectric material and on the other side by a low–refractive–index dielectric material. A plane wave is launched in the optically denser dielectric material towards the metal film, in order to excite a surface–plasmon wave at the interface of the metal with the optically rarer dielectric material [3]. The plane wave must be p–polarized, The telltale sign is a sharp peak in absorbance (i.e., a sharp trough in reflectance without a compensatory peak in transmittance) as the angle of incidence (with respect to the thickness direction) of the launched plane wave is changed [4]. Because the angle of incidence for exciting the surface–plasmon wave is a delicate function of the constitutive properties of all three materials, surface–plasmon waves in the visible and the near–infrared regimes are exploited for sensing, imaging, and other applications [5, 6].