SINGLE-MODE OPTICAL-FIBER SURFACE PLASMA-WAVE CHEMICAL SENSOR

We describe a new design of optical fibre surface plasma wave chemical sensor. The basic sensor consists of a tapered single-mode optical fi bre with a thin layer of silver evaporated onto the tapered section. T he gradually changing diameter of the fibre along the taper and the va riation in silver depth around the taper result in a distributed coupl ing between the guided mode of the fibre and the surface plasma wave. As a result, the coupling to the surface plasma wave occurs over an en larged spectral range. The device shows good sensitivity to refractive index with refractive index changes of 5 x 10(-4) being delectable. T he device is compact, simple to make, and has applications as a bioche mical or immunosensor. (C) 1997 Elsevier Science S.A.