Forming structure comprising light guide with aligned cavity

摘要

A buffer layer (2) on a substrate (1) is covered by a layer of higher refractive index which will form the core (3). It is covered by an initial mask and the unmasked regions are etched and covered with a layer (7) of lower refractive index than the core. A mask then covers the layer at right angles to the guide and the uncovered regions are etched to a depth of the covering and buffer layers. The resultant etching down to the substrate is covered by a mask (M3) which is a thickness of the buffer layer. The substrate is then etched to define the cavity (8).which will receive an optical fibre.