Near field detector for integrated surface plasmon resonance biosensor applications

Integrated surface plasmon resonance biosensors promise to enable compact and portable biosensing at high sensitivities. To replace the far field detector traditionally used to detect surface plasmons we integrate a near field detector below a functionalized gold film. The evanescent field of a surface plasmon at the aqueous-gold interface is converted into photocurrent by a thin film organic heterojunction diode. We demonstrate that use of the near field detector is equivalent to the traditional far field measurement of reflectivity. The sensor is stable and reversible in an aqueous environment for periods of 6 hrs. For specific binding of neutravidin, the detection limit is 4 mu g/cm(2). The sensitivity can be improved by reducing surface roughness of the gold layers and optimization of the device design. From simulations, we predict a maximum sensitivity that is two times lower than a comparable conventional SPR biosensor. (C) 2008 Optical Society of America