Ultrasensitive guided-mode resonance biosensors superimposed with vertical-sidewall roughness
Journal
Applied Optics
Journal Volume
50
Journal Issue
26
Pages
5139-5148
Date Issued
2011
Author(s)
Jao, C.-S.
Abstract
In this paper, we present our investigations of the effects of vertical-sidewall roughness (VSR) on guidedmode resonance (GMR) filters made of subwavelength grating for applications to ultrasensitive biosensors operated underIRillumination. We designed the spectral FWHM of the grating filter to be as narrow as possible in order to emphasize the sensitivity and VSR effects. Three types of VSR morphologies on the grating-in terms of the correlation length ζ and the rms of the maximum roughness deviation σ-were considered and evaluated. Rigorous coupled-wave analysis was then implemented to quantify the shifts in the reflective resonance peak wavelength value (PWV) of the grating filter. Our simulations show that for specific ζ values, the PWVs remain constant even if σ becomes as large as 10 nm; this indicates dramatic bandgaplike stripes, which are similar to the bandgaps observed in the band diagrams of photonic crystals in the ζ-σ diagram that we have proposed in this study. In other words, the effects of VSR on the GMR biosensor performance are insignificant when ζ is located at certain bands; therefore, this type of roughness is highly tolerable even if the linewidth of the filter is decreased to only a few tens of nanometers. © 2011 Optical Society of America.
SDGs
Type
journal article