Patent ID: 7221843

Claim:
A waveguide, which is part of an integrated optical circuit, the waveguide being arranged onto a planar substrate and having a core section propagating light in a certain direction of propagation, characterised in that the waveguide is a conversion waveguide ( 60 ) between a ridge-type waveguide ( 61 ) and a strip waveguide ( 62 ), in said conversion waveguide the core section being made of the one and same material so that a cross-section of the core section transverse to the direction of propagation (z) of light is two-step ( 6 ; 6 1a , 6 2a ; 6 1b , 6 2b ) from both edges ( 60 a , 60 b ), said conversion waveguide comprising first and second layers ( 60 1 , 60 2 ) of different widths (l 60a , l 60b ), a height (h 60a ) of the first layer ( 60 1 ) being equal to a height of a ridge ( 61 1 ) of the ridge-type waveguide ( 61 ), and a height (h 60b ) of the second layer ( 60 2 ) being equal to a height of a base part ( 61 2 ) of the ridge-type waveguide ( 61 ), a sum of the heights ( h60a , h 60b ) of the first and second layers ( 60 1 , 60 2 ) being equal to a height of the strip waveguide ( 62 ), the widths of the two layers ( 601 , 602 ) being arranged to change uniformly between the ridge-type and strip waveguides to be connected for fitting the ridge-type and strip waveguides together laterally.