Surface-plasmon-polariton (SPP) waves are used for high resolution optical sensing of chemical samples. These are created by sending light beams through the interface of a metal and a dielectric material. Because waves of only one frequency could be generated at a time in the interface, this technology was applicable for sensing unique chemical compounds.
Now researchers from Penn State are reporting in journal Scientific Reports a new technique that allows for multiple SPP waves of different frequencies to be excited along the interface. This should allow for SPP technology to become useful for diagnostics when screening for multiple chemical markers.
Conventional thin films are made by layering clumps of atoms in rows on a surface, or substrate. To make more channels for the SPP waves, Pulsifer and Swiontek slowly rotated the substrate during the fabrication of the thin film, sculpturing it to create nanoscale springs, so that the regions between the springs can be infiltrated. Lakhtakia and his students had showed earlier that the interface of this type of thin film and a metal film can guide many SPP waves at a fixed frequency.
To test the new optical sensing technique, the researchers built a prototype of an optical-sensing device that has two legs. On one leg, a laser focuses a beam of light toward a prism that rests at the apex of the device. The peak of the prism points down, so that the researchers can add the metal film and sculptured thin film to the flat surface on the prism’s hypotenuse.
The light beam is then refracted toward a photon detector on the opposite leg of the device.
Open access article in Scientific Reports: Optical sensing of analytes in aqueous solutions with a multiple surface-plasmon-polariton-wave platform