Characteristics and applications of the infrared enhanced transmission of metallic subwavelength arrays

Metal films that are periodically patterned exhibit striking optical properties when illuminated with light of wavelength near the periodicity of the film. Nickel mesh with holes spaced by 12.7mum show a higher fractional transmission than the fractional open area of the mesh. This effect is attributed to surface plasmons which allow light incident on one side of the metal mesh to be transmitted to the other side where it is released as light. The majority of surface plasmon studies up to this point have been conducted in the visible and ultraviolet. Due to the hole spacing of this mesh, the surface plasmon phenomenon is seen in the infrared.; Since this work is done in a different region of the electromagnetic spectrum, determining how the surface plasmons behave in this region will aid the overall understanding and help improve the current theories describing surface plasmons. Coating the nickel mesh with other metals allows the effect of the metal on transmission to be studied. In the visible and ultraviolet the metal is predicted to have an impact on the surface plasmons characteristics. Coating the mesh with other metals also closes down the holes so the effect of changing the size of the holes can be studied further aiding in an understanding of the importance of hole size on the surface plasmons.; This increased transmission has been used to study molecular species which are bound to the surface of the mesh. The reaction that converts methanol to formaldehyde has been studied. Due to the unique spectroscopic properties of the mesh, surface species exhibit increased spectroscopic absorptions. The absorptions are enhanced to such an extent that the reactants, products and the adsorbed methoxy radical intermediate have been observed with significant intensity.