GRATING MICROSTRUCTURES FOR OPTICAL WAVEGUIDE SENSORS

摘要

Waveguide grating structures are being used both as coupling and as sensing elements in integrated optical sensors of physical and chemical parameters; here we present two microfabrication technologies which can be used for the realisation of periodic structures in glass substrates. The first process, which has been already optimised, uses the holographic writing of the grating in a photoresist layer and the subsequent transfer of the grating into the glass by means of reactive ion etching. The second process, which is at a preliminary stage of development, can be applied only in the case of photorefractive glasses, and has the aim of writing a phase grating directly into the substrate by means of the exposure to an excimer laser beam, through a proper phase mask. Gratings have been fabricated by both the techniques, and their characteristics are discussed.