Exciting surface plasmons with a Mid-IR OPO Bachelor assignment Applied Physics

Surface plasmon polaritons are commonly used in chemical and biological applications. The physical applications of surface plasmon polaritons are less common, but promises to be useful in nonlinear effects such as frequency doubling. The propagation length of a surface plasmon polariton is low (typically 10 to 100 μm) due to absorption, radiation and coupling. The propagation length might be longer for long wavelengths. The goal of this experiment was to excite surface plasmon polaritons at thin films of metal in the Kretschmann configuration with a mid-infrared optical parametric oscillator. The metals used are thin layers of aluminium, copper and gold in the range of 12 to 36 nm deposited onto a lithium niobate wafer. The wafer is attached to a gadolinium germanium garnet prism with the use of immersion oil. The excitation of a surface plasmon polariton is detected by measuring the angular reflectivity spectrum of the configuration. The goal of this research is achieved, the determined propagation lengths (if only Ohmic losses are taken into account) are in the range of 20-200 μm, which can be concluded from measurements o