Abstract
Dielectric multilayer structures with a grating profile on the top-most layer adds an additional degree of freedom to the phase matching conditions for Bloch surface wave excitation. The conditions for Bloch surface wave coupling can be achieved by rotating both polar and azimuthal angles. The generation of Bloch surface waves as a function of azimuthal angle has similar characteristics to conventional grating coupled Bloch surface waves. However, azimuthally generated Bloch surface waves have enhanced angular sensitivity compared to conventional polar angle coupled modes, which makes them appropriate for detecting tiny variations in surface refractive index due to the addition of nano-particles such as protein molecules.
Highlights
Bloch surface waves (BSW) are electromagnetic modes propagating at the interface of truncated dielectric multilayer structures and a homogeneous medium
Previous related studies were done on surface plasmon polaritons (SPPs)—electromagnetic modes propagating at the interface of a metal and a dielectric medium—where the reflectivity is measured by fixing the azimuthal angle to a certain value followed by the conventional polar incident angle sweep
The proposed method consists in taking advantage of the surface grating profile, as illustrated in Fig. 1, to achieve sensing by selectively exciting BSWs via azimuthal interrogation
Summary
Bloch surface waves (BSW) are electromagnetic modes propagating at the interface of truncated dielectric multilayer structures and a homogeneous medium. It was recently shown that if the surface layer is periodically corrugated and the dielectric constant of the dielectric medium is real, positive, and large, it can support a leaky BSW26 Such leaky modes still lie below the light line of the homogeneous layer material but fall above that of the dielectric multilayer material. These states are radiative into the homogeneous medium, they can have a long lifetime assisted by destructive interference between different leakage channels Such leaky-mode resonances, with moderate to infinitely high quality factor (Q) that confine freely propagating electromagnetic waves at a periodically modulated surface, are of interest in applications such as lossless mirrors[30], high-performance optical filters[31], label-free biosensors[32], dielectric metasurfaces[33, 34], dielectric-based optical magnetism[35], and many others[36, 37]. It can be used to make polarization independent biosensors, due to the fact that a linear grating profile facilitates polarization conversion[40,41,42]
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