Blue surface plasmon propagation along thin gold film-gas interface and its use for sensitive nitrogen dioxide detection

We demonstrate effective surface plasmon propagation along thin gold film in a blue spectral range: the measured 0.6° angular width of the plasmon excitation peak corresponds to the propagation length around 7 μm. For this end, we prepared a specially designed photonic crystal (PC; 18-layer 1D structure of altering transparent dielectric layers with relatively large and low refraction indices deposited onto a silica support) coated by a 8 nm thick gold layer. For given blue light wavelength (405 nm) and certain light incidence angle this 1D PC structure supports ultralong surface plasmon propagation along the gold nanofilm. This structure has been tested as a surface plasmon resonance sensor to detect small concentrations of nitrogen dioxide in air. This sensor exhibited the sensitivity similar to earlier works where surface plasmon resonance in red spectral range has been used for this purpose.