Influence of Side-Polished Fiber Surface Topography on Surface Plasmon Resonance Wavelengths and the Full Width at Half-Maximum

The influence of surface topography of side-polished fiber on resonance wavelengths and the full-width-at-half-maximum ( FWHM) of surface plasmon resonance was evaluated in this work, based on the power spectrum density, wavelet, and finite-difference time-domain methods. The abrasive size determined the surface topography with various spatial period components. Coarse abrasives induced obvious low-frequency waviness features and a blue shift in the resonance wavelength. Fine abrasives introduced middle frequency microwaviness ( 0.5-1.0 mu m), which led to a blue or red shift, depending on the special period extent between 0.5 and 0.75 mu m. All waviness components broadened the FWHM because of the superimposed effect and the introduction of a high-order coupling model. High-frequency roughness components were able to shift the resonance peaks toward shorter wavelengths. Larger coupling energy tended to decrease the FWH, while high-order coupled modes tended to broaden the FWHM. We established a roughness model with Maxwell-Garnett theory incorporated into fractal dimensions. Experimental results demonstrated the feasibility of such a model. Small abrasive particles were able to narrow the FWHM, which is beneficial for identification of resonance wavelengths and evaluation of the surface plasmon resonance effect.