Optical integrated circuit comprising a light guide forming at least one optical separation

1. An optical integrated circuit with waveguide separation on a substrate ( 3 ), the circuit comprising at least one optical separating unit, the unit comprising an optical input/output interface ( 2 ) at the edge of the substrate intended for being in relation with an external means for guiding a light wave, the interface extending in the circuit through an optical guiding input section of determined length L 1 extended by at least two optical guiding branches ( 7 , 8 ) mutually spaced apart substantially symmetrically relative to the general direction of the input section,

characterised in that the input section from the interface at the edge of the substrate includes as many optical guides ( 4 a , 4 b ) as there are branches, each of the optical guides being continuous from the interface at the edge of the substrate up to its corresponding branch inclusive, the optical guides of the input section being substantially rectilinear and mutually parallel, two adjacent optical guides of the input section being separated by an aperture ( 9 ) of determined width D, the refractive index of the opening being lower than that of the optical guides, each optical guide of the input section having a determined width We 1 , and in that each branch optical guide exhibits a width increasing in the direction away from the input section from the width We 1 up to a determined width Ws, the widths We 1 and D being such that the guides are monomode at the working wavelength.

2. An optical integrated circuit according to claim 1 , characterised in that the unit includes moreover a transition zone of length L 0 between the interface and the input section, wherein the transition zone includes optical guides ( 10 a , 10 b ) continuous with those of the input section ( 4 a , 4 b ), each of the optical guides of the transition zone having a width increasing in the direction away from the interface from a determined width We 0 up to the width We 1 , and in that the opening ( 9 ) between two adjacent optical guides of the transition zone has a width increasing in the direction away from the interface from a determined width D′ up to the width D.

3. An optical integrated circuit according to claim 1 , characterised in that the variation in width of the optical guides of the branches is linear in relation to the distance of propagation.

4. An optical integrated circuit according to claim 1 , characterised in that the length L 1 of the input section ranges between 0 excluded and 10 mm.

5. An optical integrated circuit according to claim 1 , characterised in that in the case of two branches the semi-angle α for separating the branches ranges between 0.1° and 0.50° and is preferably about 0.175°.

6. An optical integrated circuit according to claim 1 , characterised in that the external guiding means is an optical fiber ( 1 ) bonded to the interface of the optical integrated circuit.

7. An optical integrated circuit according to claim 1 , characterised in that the substrate of the optical integrated circuit is made of lithium niobate (LiNbO3).

8. An optical integrated circuit according to claim 1 characterised in that it comprises a separating unit and that it is a Y-shaped optical separator/recombinator with at least two branches.

9. An optical integrated circuit according to claim 1 , characterised in that it comprises two cascaded, head to tail mounted separating units and that it is an integrated Mach-Zehnder interferometer with at least two branches.

10. An optical integrated circuit according to claim 2 , characterised in that the variation in width of the optical guides of the branches is linear in relation to the distance of propagation.

11. An optical integrated circuit according to claim 2 , characterised in that the length L 1 of the input section ranges between 0 excluded and 10 mm.

12. An optical integrated circuit according to claim 3 , characterised in that the length L 1 of the input section ranges between 0 excluded and 10 mm.

13. An optical integrated circuit according to claim 2 , characterised in that in the case of two branches the semi-angle α for separating the branches ranges between 0.1° and 0.50° and is preferably about 0.175°.

14. An optical integrated circuit according to claim 3 , characterised in that in the case of two branches the semi-angle α for separating the branches ranges between 0.1° and 0.50° and is preferably about 0.175°.

15. An optical integrated circuit according to claim 4 , characterised in that in the case of two branches the semi-angle α for separating the branches ranges between 0.1° and 0.50° and is preferably about 0.175°.

16. An optical integrated circuit according to claim 2 , characterised in that the external guiding means is an optical fiber ( 1 ) bonded to the interface of the optical integrated circuit.

17. An optical integrated circuit according to claim 3 , characterised in that the external guiding means is an optical fiber ( 1 ) bonded to the interface of the optical integrated circuit.

18. An optical integrated circuit according to claim 4 , characterised in that the external guiding means is an optical fiber ( 1 ) bonded to the interface of the optical integrated circuit.

19. An optical integrated circuit according to claim 5 , characterised in that the external guiding means is an optical fiber ( 1 ) bonded to the interface of the optical integrated circuit.

20. An optical integrated circuit according to claim 2 , characterised in that the substrate of the optical integrated circuit is made of lithium niobate (LiNbO3).