UV-Written Long-Period Grating Based on Long-Range Surface Plasmon-Polariton Waveguide

This letter proposes a long-period grating based on coupling between the long-range surface plasmon mode and a cladding mode of a thin Au film stripe fully buried in polymer SU-8. Periodical surface corrugation and accompanied refractive index variation on the SU-8 upper-cladding were induced by ultraviolet-written technique. This configuration along the Au stripe gives rise to the observation of strong resonance in a 3-mm long periodic grating. A rejection band with a contrast of -23.5 dB at the wavelength 1561 nm was achieved, which can be tuned by ~30 nm with a temperature change of 6 °C. The grating offers potential applications in surface plasmon waveguide circuits and biosensors.