US Patent 11209592 Integrated active devices with enhanced optical coupling to dielectric waveguides

A device comprises first, second and third elements fabricated on a common substrate. The first element comprises an active waveguide structure comprising: one portion, of effective cross-sectional area A1, supporting a first optical mode; and a second portion, butt-coupled to the first portion, of effective cross-sectional area A2>A1. The second element comprises a passive waveguide structure supporting a second optical mode. The third element, at least partly butt-coupled to the second portion, comprises an intermediate waveguide structure supporting intermediate optical modes. If the first optical mode differs from the second optical mode by more than a predetermined amount, a tapered waveguide structure in at least one of the second and third elements facilitates efficient adiabatic transformation between the first optical mode and one intermediate optical mode. No adiabatic transformation occurs between any intermediate optical mode and the first optical mode. Mutual alignments of the elements are defined using lithographic marks.