Investigation of the limit of lateral beam shifts on a symmetrical metal-cladding waveguide

This paper reports that Goos-Hǎnchen （GH） shifts occurring on a symmetrical metal-cladding waveguide are experimentally identified. It was found that there exists a critical thickness of the upper metal layer, hcr, above which negative shift is observed and, reversely, positive shift occurs. Both positive and negative GH shifts near the critical thickness do not vary dramatically and can achieve a maximum on the submillimeter scale, which is different from simulated results using the stationary-phase method. It also shows that this critical thickness, hcr, can be obtained at the position for zero reflectivity by setting the intrinsic damping to be the same as the radiative damping. The GH effects observed near the critical thickness are produced by extreme distortion of the reflected beam profiles, which limits the amplitude of the GH shift and, further, the sensitivity of the GH optical sensor based on the symmetrical metal-cladding waveguide.

A SIMPLE SOLUTION FOR MULTILAYER METALLIC OPTICAL WAVEGUIDES

A simple solution for a multilayer metallic optical waveguide by transforming it intoan equivalent three-layer slab waveguide is presented. The dispersion relation of the equivalentthree-layer slab waveguide is solved by using a simple iterative formula. This method itself isexact and can approach any accuracy desired. Moreover, the numerical results for four-layer andfive-layer structures show that the second-order solution is also accurate enough. It is simple andhas the same form of expressions for TE and TM modes and for different layer structures.

Polymer-coated symmetrical metal-cladding waveguide for chemical vapor detection with high sensitivity

An optical platform for sensitive detection of chemical vapor based on a polymer-coated symmetrical metal-cladding waveguide is proposed.The diffusion of chemical vapor usually leads to a combinational effect in the polymer layer,i.e.,swelling and refractive index change.Owing to the high sensitivity of ultrahigh-order modes,the vapor-induced effect will give rise to a dramatic variation of the reflected light intensity.For proof-of-concept,a good linearity and a low detection limit of toluene and benzene are experimentally demonstrated with an amorphous Teflon AF polymer layer.

Refractive Index Sensor Based on Metal-Clad Planar Polymer Waveguide Operating at 850nm

A metal-clad planar polymer waveguide refractive index sensor based on epoxy(EPO)polymer materials by using light intensity interrogation at 850 nm is designed.The polymethyl methacrylate(PMMA)material is deployed as the low refractive index(RI)buffer layer in order to better couple the optical guided mode and the surface plasmon polaritons(SPP)mode for working in water environment.The effects of the gold film thickness,PMMA buffer layer thickness,waveguide layer thickness,waveguide width,and gold length on the sensor sensing characteristics have been comprehensively studied.Simulation results demonstrate that the normalized transmission increases quasi-linearly with the increment of RI of the analyte from 1.33 to 1.46.The sensitivity is 491.5 dB/RIU,corresponding to a high RI resolution of 2.6×10^(9)RIU.The designed SPP-based optical waveguide sensor is low-cost,wide-range,and high-precision,and has a broad application prospect in biochemical sensing with merits of miniaturization,flexibility,and multiplexing.