Molecule-surface plasmon interactions in hole arrays: Enhanced absorption, refractive index changes, and all-optical switching

The phenomenon of, surface plasmon interactions in hole arrays, and its applications, are discussed. The use of EOT to enhance the absorbance in the visible spectrum and to induce refractive-index changes by the presence of molecular absorption bands was investigated. A surface plasmon is (SP) light trapped at the surface of a metal due to its interaction with the free electrons of the metal. The extraordinary or enhanced optical transmission (EOT) phenomenon involves the transmission of light through holes with lateral dimensions smaller than half the incident wavelength. All the hole arrays were milled in optically thick Ag films deposited on quartz substrate using a focused ion beam apparatus. The polymer films were spin coated from dichloromethane solutions at a speed of 2000 revolutions/min for 1 min. The rhodamine LD700 was dissolved with PMMA and the resulting film thicknesses were measured by atomic force microscopy and scanning electron microscopy.