Patent ID: 7327915

Claim:
A planar integrated optical structure comprising: a principal waveguide having a core and a cladding that define a first light path for the guided propagation of light energy, operable to transmit a first portion of said propagation of light energy through said core of the principal waveguide and operable to transmit a second portion of said propagation of light energy through said cladding of the principal waveguide; means sensitive to the light energy radiated into the cladding of the principal waveguide comprising two series of secondary waveguides arranged on opposite sides of the principal waveguide, at least one of the secondary waveguides having a core and a cladding that define a second light path for the guided propagation of light energy, said at least one secondary waveguide having: an entry situated in the cladding of the principal waveguide at such a distance from the core of the principal waveguide as not to interfere, or interfere only to a negligible extent, with the propagation of the light energy along the first light path, said entry operable to receive at least a fraction of said second portion of said propagation of light energy; and a core section that becomes greater in a first part from the entry onwards; and at least two extensive regions of the same material as the cores of the waveguides, wherein the cores of the secondary wave guides each terminate in one of the extensive regions.