Through computer simulations and surface plasmon resonance (SPR) measurements, we establish optimum parameters for the design and fabrication of SPR sensors of high sensitivity, resolution, stability, and long decay-length evanescent fields. We present simulations and experimental SPR data for variety of sensors fabricated by using bimetal (Ag/Au) and multilayer waveguide-coupled Ag/Si3N4/Au structures. The simulations were carried out by using the transfer matrix method in MATLAB environment. Results are presented as functions of the thickness of the metal (Ag or Au) and the waveguide dielectric used in Ag/Si3N4/Au structures. Excellent agreement is observed between the simulations and experiments. For optimized thickness of the Si3N4 waveguide (150 nm), the sensor exhibits very high sensitivity to changes in the refractive index of analytes, Sn≈52°/RIU, extremely high resolution (FWHM≤0.28°), and long penetration depth of evanescent fields (δ≥305nm).
We present evidence for surface plasmons (SPs) in a nematic liquid crystal (LC) containing dispersion of gold nanoparticles (Au NPs). The evidence originates from observations of attenuated total reflection (ATR) of p-polarized laser incident upon a high-index prism/LC-Au NPs/glass structure. We argue that SPs are generated through evanescent waves interacting with Au NPs embedded in the LC and NPs' dispersing medium.
Hafnium dioxide has been recognized as an excellent dielectric for microelectronics. However, its usefulness for the surface plasmon based sensors has not yet been tested. Here we investigate its usefulness for waveguide-coupled bi-metallic surface plasmon resonance sensors. Several Ag/HfO2/Au multilayer structure sensors were fabricated and evaluated by optical measurements and computer simulations. The resulting data establish correlations between the growth parameters and sensor performance. The sensor sensitivity to refractive index of analytes is determined to be Sn=∂θSPR∂n≥470. The sensitivity data are supported by simulations, which also predict 314 nm for the evanescent field decay length in air.
Surface plasmon excitations can result from the absorption of light incident on gold films. Adding a ferromagnetic metal, in our case iron, allows the surface plasmon resonance peak energy to be manipulated not only by the free electrons present in metals, but by an external magnetic field as well. Surface plasmon resonance is being used by devices found in industry, however manipulations of the surface plasmon resonance peak energy condition need further studies. Two experimental results are reported in this paper based on thin films of iron on gold/chromium, one based on the thickness of iron and the other with an application of a large 4000 Gauss DC magnetic field. Both of these changes result in a shift in the peak energy of the surface plasmon.
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