Surface plasmon-polariton resonances in metal-coated holographic azopolymer gratings

Surface plasmon polariton (SPP) is an electromagnetic excitation that propagates along the interface between a metal and a dielectric medium and is generated by resonant interaction between the surface charge oscillation and the electromagnetic field of light. This excitation decays exponentially with increasing distance from the surface and for this reason cannot be observed in far-field experiments unless the SPP is transformed into light. Three methods are mainly applied to couple light on a metal-dielectric interface and observe SPP - using a prism, a non-periodic or periodic structure (e.g. diffraction grating) on the surface. In this article a study of surface plasmon resonance is presented using a diffraction grating to couple light on the dielectric-metal interface. Surface relief gratings holographically recorded in azopolymer film are used as a substrate and are subsequently coated with thin film of aluminum (Al). The presence of SPR is experimentally verified by the observed resonance peaks in transmission of TM polarized light.