Correlation analysis between plasmon field distribution and sensitivity enhancement in reflection- and transmission-type localized surface plasmon resonance biosensors

We examine the correlation between the plasmon field distribution and the sensitivity enhancement for both reflectionand transmission-type localized surface plasmon resonance (LSPR) biosensors with surface-relief gold nanogratings. In our calculation, the near-field characteristics are obtained from the finite-difference time-domain method and compared with the refractive index sensitivity as a unit target sample moves along the sensor surface. The numerical results show that the highest enhancement of sensitivity is found at the lower grating corners where an interplay between the target sample and the locally enhanced field can occur efficiently. This study suggests that, by localizing biomolecular interactions to the highly enhanced field, we can achieve a significantly improved LSPR detection with high sensitivity and a great linearity in a wide dynamic range. © 2011 Optical Society of America OCIS codes: 050.2770, 280.4788, 240.6680.