Abstract
In this study, a surface diffraction two-dimensional (2D) grating structure was placed on the topmost layer of distributed Bragg reflectors (DBRs) for biosensing. Bloch surface wave (BSW) resonance was realized by coupling a 2D subwavelength hole-array grating and could be excited at different locations: the surface of 2D-grating layer or the inter-face between the DBR and bio-solution. Material losses in the multilayer dielectric were measured to test the robustness of this scheme. Both the surface diffraction-grating BSW (DG-BSW) and the alternative guided grating-coupled BSW (GC-BSW) configuration showed markedly enhanced angular sensitivity compared to conventional prism-coupled schematics. Exciting these modes using a grating-coupling technique appears to yield different extreme sensitivity modes with a maximum of 1190°/RIU for DG-BSW and 2255°/RIU for GC-BSW. Refractive index sensors with a high figure of merit may be realized via such compact configurations.
Highlights
Designed photonic devices represent the possibility of real-time, label-free selective detection of various chemical and biological species for a variety of medical research and environmental monitoring applications and for the optical detection of miniscule quantities of molecules in highly diluted solutions [1,2,3]
We present one configuration to demonstrate the possibility of coupling a Bloch surface waves (BSWs) on the tip of the grating-coupled Bragg mirror structure, as well as an alternative scheme which demonstrates the influence of available dielectric loss
We found that the sensitivity characteristics during dynamic monitoring of the solution to be tested can be improved by the proposed scheme
Summary
Designed photonic devices represent the possibility of real-time, label-free selective detection of various chemical and biological species for a variety of medical research and environmental monitoring applications and for the optical detection of miniscule quantities of molecules in highly diluted solutions [1,2,3]. The most popular surface wave resonance-based sensing technology is the surface plasmon resonance (SPR) method [4, 16] which works by exciting surface plasmon polaritons along a metal/dielectric interface by incident light. BSW is a promising alternative to SPPs. BSW technology based on the low optical loss all-dielectric structure has higher sensitivity and adjustable field enhancement than other surface waves and can be combined with different chemical surface modification methods and optical detection mechanisms [19,20,21]. Most 1D photonic crystal (1DPC)-based sensors utilize complicated Kretschmann prism-coupled structures to excite BSW. Few researchers have explored grating-coupled-based BSW sensors or other new designs to reduce the complexity of bulk optical components. Vijay et al [27] did report enhanced sensitivity in a topmost layer grating profile assessed via azimuthal interrogation; the BSW leakage
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