1. A method of controlling birefringence in a rib waveguide structure manufactured in silicon, the rib waveguide structure comprising an elongated rib element having an upper face and two side faces, the method comprising:
forming a blanket layer of silicon nitride to a predetermined thickness over said rib waveguide structure directly abutting said upper face and side faces.
2. A method according to claim 1, wherein the blanket layer of silicon nitride extends over the substrate flanks on either side of the rib waveguide structure.
3. A method of controlling birefringence in a rib waveguide structure manufactured in silicon, the rib waveguide structure comprising an elongated rib element having an upper face and two side faces, the method comprising:
growing a layer of oxide over the upper face and side faces;
stripping the oxide layer to reveal the upper face and side faces; and
forming a layer of silicon nitride to a predetermined thickness over said rib waveguide structure directly abutting said upper face and side faces.
4. Use of a layer of silicon nitride in a method of fabricating a rib waveguide structure in silicon to control birefringence by depositing said layer to a predetermined thickness over said rib waveguide structure.
5. A method of manufacturing a silicon rib waveguide structure comprising:
forming an elongated rib element in a silicon substrate, the elongated rib element having an upper face and two side faces; and
forming a layer of silicon nitride to a predetermined thickness over said elongated rib element directly abutting said upper face and side faces, the predetermined thickness being selected such as to control birefringence in the rib waveguide structure.
6. A method of manufacturing a silicon rib waveguide structure, the method comprising:
forming an elongated rib element having an upper face and two side faces in a silicon substrate;
growing a layer of oxide over the upper face and side faces;
stripping the oxide layer to reveal the upper face and side faces; and
forming a layer of silicon nitride to a predetermined thickness over said rib waveguide structure directly abutting said upper face and side faces.
7. A silicon rib waveguide structure comprising an elongated rib element having an upper face and two side faces formed of silicon and a layer of silicon nitride directly abutting said upper face and side faces and having a predetermined thickness selected to control birefringence in the silicon rib waveguide structure.
8. A method or structure according to any preceding claim, wherein the predetermined thickness of the layer of silicon nitride is 1000 A for a waveguide structure having a width of 3-5 microns.
9. An evanescent coupler structure comprising first and second silicon rib waveguides each comprising an elongated rib element having an upper face and two side faces formed of silicon and a layer of silicon nitride directly abutting said upper face and side faces and having a predetermined thickness selected to control birefringence in the evanescent coupler.
10. A structure according to claim 7, 8 or 9, wherein the blanket layer of silicon nitride extends over the substrate flanks on either side of the rib waveguide structure.
11. A method or structure according to any preceding claim wherein the waveguide structure is manufactured on a silicon-on-insulator wafer.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. Device for optoelectronic monitoring of objects, with a transmitting unit (12) that transmits light beams (24) in a structured illuminating pattern, with a receiving unit (14), that contains an image recorder(28) on which the object (26) illuminated with structured illuminating pattern is recorded, and with a housing (10) in which the transmitting unit (12) and the receiving unit (14) are located and which has a faceplate (16) for the transmitting unit (12) and the receiving unit (14), characterized in that the transmitting unit (12), the receiving unit (14), and the faceplate (16) are positioned in the housing (10) so that the light beams that are directly reflected at the faceplate (16) do not travel (24) into the image recorder (28) of the receiving unit (14) and so that beams from the transmitting unit (12) that are diffusely scattered at the faceplate (16) are detected in the receiving unit (14) separately from the recording of the object (26).
2. Device according to claim 1, characterized in that the transmitting unit (12) contains a light source (18), a beam collimator (20), and a diffractive optical element (22) for purposes of producing the light beams (24).
3. Device according to claim 1 or 2, characterized in that the light beams (24) are individual beams spread fan-like in a scanning plane and in that the receiving unit (14) observes the object (26) at a viewing angle that is inclined with respect to this scanning plane.
4. Device according to one of the preceding claims, characterized in that the image recorder (28) contains a matrix arrangement of photoelectric elements.
5. Device according to claim 4, characterized in that light beams (24) diffusely scattered at the faceplate (16) are recorded by the image recorder (28) separate from recording of the object (26).
6. Device according to claim 5, characterized in that the faceplate (16) has a diffusely scattering zone (46) whose recording (48) on the image recorder (28) is used for monitoring functionality.
7. Device according to one of the preceding claims, characterized in that the receiving unit contains an additional receiving element (52) that is separate from the image recorder (28).
8. Device according to claim 7, characterized in that the receiving element receives beams from the transmitting unit (12) that are diffusely scattered at the faceplate (16).
9. Device according to claim 7, characterized in that the receiving element (52) receives beams from the transmitting unit (12) that are directly reflected at the faceplate (16).
10. Device according to claim 4, characterized in that a wide angle light source (50) is provided that completely illuminates the image recorder (28) for purposes of checking functionality.