Abstract

Efficient coupling of light between fibres and integrated optic circuits is necessary if integrated optics is to be used in optical fibre communication systems. It would also be advantageous if the fibre could be coupled to any chosen part of the integrated optic circuit. Butt jointing to the film edge⁽¹⁾ is feasible only between two accurately aligned guide ends with matched field distributions. However distributed coupling can occur between any two sections of fibre and film and a chosen amount of energy can be transferred. This paper describes a theoretical and experimental study of the distributed coupling, shown in Fig. 1, between a single-mode fibre and a thin film. Both guides have a step index profile and the two modes are phase matched by a spatially periodic grating deposited on the film. This particular configuration provides in principle for complete coupling but also introduces possible unwanted interactions which must be avoided by careful design.

© 1976 Optical Society of America