Smartphone-based surface plasmon resonance imaging for near-field concentration mapping

In this work, smartphone-based surface plasmon resonance imaging is used for the near-field mapping of a liquid sample's concentration distribution. The principal design uses a special coupler based on a parallel incident light beam with p-polarization from a smartphone screen; this light is used to excite surface plasmons on a gold layer 50 nm thick. Using a bespoke application, surface plasmon resonance (SPR) intensity changes are detected in the SPR images captured with the front-facing camera. The SPR intensity is converted to the corresponding concentration using the three-layer Fresnel equation. Concentration mapping observations are presented for the dilution of ethanol dilution by water in a flow cell and an array of chlorine droplets on a gold surface. The high efficiency of this device means that it can be used for photonics research and advanced laboratory experiments.