Nano-Assembled Plasmonic Crystals Devices for Sensing Applications.

摘要

The ability of plasmonic nano-structures to concentrate light into sub-wavelength volumes offers the potential for developing new devices and applications. Surface plasmons are electron oscillations that propagate on a metal surface. The interaction of light with surface plasmons can be tailored by periodic nano-structures on a surface, thus allowing miniaturized photonic devices with length scales much smaller than those currently achieved. The purpose of this dissertation is to develop a low cost self-assembly method to fabricate large area plasmonic crystals and study the physical properties of surface plasmons. Several plasmonic devices are designed using the self-assembled gold nanobump arrays.;A polystyrene sphere self-assembly technique was developed for fabricating holes or bumps as small as 150 nm with spacing controlled by the sphere diameter (typically 500–700 nm). Several applications were developed, which were based on the sensitivity of the photon-plasmons coupling to 1) the surface dielectric and 2) the incident angle. A sensitivity to refractive index changes of about 100 nm per refractive index units was demonstrated by varying the surrounding dielectric environment with several chemicals for sensing applications. An increasing variation in the color of a vanadium oxides thermochromic device was observed by using surface plasmons to enhance the variation in reflection. Surface plasmons were also used in an optical modulator, where excitation by one wavelength was used to changes the transmission at a different wavelength.;Using the angular sensitivity of the nano-structured plasmonic thin films, an angle of arrival sensor was fabricated. This sensor can be used to track the position of the sun or other collimated light sources like lasers. The polarization dependency of the device was studied and its behavior was explained by the lattice momentum matching mechanism. Inspired by the novel concept of this angle of arrival sensor, a wavefront sensor was theoretically examined. It measured the incident angles of the incoming wavefront on a pixel array and reconstructed the wavefront with a least-squares fitting algorithm.