Abstract

Tapered velocity couplers have been applied to a number of problems in integrated optics since their introduction in 1974.¹ This technique has pro­ven useful for transferring optical energy between waveguide modes whenever the β’s, i.e. the wavevector components parallel to the surface, cross. The fraction of energy transferred depends on the optical wavelength, the coupling between the guides and the length of the interaction region. Furthermore, tapered couplers are quite insensitive to tolerance errors, as long as a velocity crossing occurs. This technique has been used to transfer light between waveguide modes on the same substrate,² from thin films to rectangular fibres,³ from in-diffused guides to thin films⁴ and to fabricate a 3 db coupler.⁵ In this paper we describe three additional applications, namely efficient transfer between waveguides on two separate substrates, from a thin film to a cylindrical fibre and as a frequency filter.

© 1978 Optical Society of America