Evanescent field characterisation of tapered optical fibre sensors in liquid environments using near field scanning optical microscopy and atomic force microscopy

Near field scanning optical microscopy (NSOM) is used to measure the evanes cent field surrounding a biconically tapered optical fibre sensor in air, w ater and dimethyl sulfoxide solution. These measurements are found to be in good agreement with those theoretically predicted using the finite differe nce-beam propagation method in combination with refractive and atomic force microscope measurements, demonstrating the validity of the model described for a number of environments.