Flexible, fibre-addressable surface-plasmon-resonance chip

Abstract

Surface plasmon resonance (SPR) sensors exploit optical coupling to surface plasmons, light waves bound to a metal surface. In the most common configuration, a SPR sensor is used with an external light source, optical components to polarize incident light and guide light to and from a metal surface, a coupling device to convert free-space light into surface plasmons and back into free-space light, and a light detector. The light source, the optical components, and the light detector are external to the SPR device, and the coupling structure is often integrated directly with the surface-plasmon-sustaining metal surface. The requirement of several external components restricts the miniaturization of SPR devices and prohibits low-cost implementation. To address these limitations, we design, fabricate, and test a new SPR device chip that is fibre-addressable, does not require a discrete coupling structure, and integrates light delivery, light polarization control, surface plasmon coupling onto a thin, flexible substrate. Our SPR chip is constructed from a thin gold layer deposited on top of a clear plastic sheet, which is then optically connected from the bottom surface onto a plastic linear polarizer sheet. Two cleaved fibres, one to input light and the other to collect reflected light, are then optically attached to SPR device. We experimentally characterize the SPR device and find good agreement between our measurements and a theoretical model based on transfer matrix formalism.