Polarization-sensitive surface plasmon enhanced ellipsometry biosensor using the photoelastic modulation technique

Scott Wu Yuan, Ho Pui Ho, S.Y. Wu, Y.K. Suen, Siu Kai Kong

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

A surface plasmon enhanced ellipsometry (SPEE) biosensor scheme based on the use of a photoelastic modulator (PEM) is reported. We show that the polarization parameters of a laser beam, tan , cos and ellipse orientation angle , can be directly measured by detecting the modulation signals at the first and second harmonics of the modulated frequency under a certain birefringence geometry. This leads to accurate measurement of refractive index variations within the evanescent field region close to the gold sensor surface, thereby enabling biosensing applications. Our experimental results confirm that the new scheme offers a respectable detection limit of 6×10−7 refractive index unit (RIU) or 15 ng/ml of biomolecule solute concentration without any compromise in dynamic range. In addition, PEM offers the possibility of single-beam phase-sensitive SPR detection that drastically reduces the complexity of the optical system, thus readily making it possible for SPR to be adopted in label-free micro-array biochips.
Original languageEnglish
JournalSensors and Actuators A: Physical
Volume151
Issue number1
Pages (from-to)23-28
ISSN0924-4247
DOIs
Publication statusPublished - 2009

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