Development of 3D metallic nano-structures for sensing applications

The interaction of a light with an array of sub-wavelength holes in a thin metal film has given rise to a unique optical property, the so-called extraordinary optical transmission (EOT). Not only does EOT of a sub-wavelength hole array exceed the incident light on the holes, but also could surpass the diffraction limit of the light and provide an intensified electric field at vicinity of the holes. These phenomena have introduced many new possibilities in the field of photonic applications. Surface Plasmon Resonance (SPR) sensing is one of the most common applications of a metallic sub-wavelength hole array structure and it results from EOT spectral shifts due to changes in the refractive index of materials on the top or bottom of the structure. In this thesis, novel sub-wavelength hole array structures with a surface plasmon energy matching property between the top and bottom of the structure have been fabricated and tested in a bulk-SPR sensing application. The numerical and experimental results demonstrated improved SPR sensitivities and higher electric field intensity at the edges of the holes at the EOT wavelength for an energy-matched structure compared to a conventional sub-wavelength hole array structure. However, in order to fabricate the novel structure, two systematic studies were performed to elucidate the effects of various geometrical parameters and different composition and thickness of the adhesion layers on the EOT properties of sub-wavelength hole array structures. Many other applications of a sub-wavelength hole array could potentially benefit from these novel structures due to their enhanced EOT properties over conventional structures.