SINGLEMODE OPTICAL-FIBER SURFACE PLASMA-WAVE CHEMICAL SENSOR

A novel singlemode optical fibre surface plasma wave sensor which operates over an extremely broad spectral range is reported. This is achieved by coating a gradually tapering singlemode fibre with a thin layer of silver similar to 50nm thick on top of an adhesive layer of chromium 3nm thick. The gradual change in the taper cross-section results in distributed phase matching between the fibre mode and the surface plasma wave, permitting a plasma wave to be excited over a spectral range from similar to 600 to 1000nm. The device shows extreme sensitivity to small changes in the external refractive index, with changes in refractive index of similar to 5 x 10(-4) being detectable. The device has considerable potential as a biochemical sensor using surface immobilisation techniques.