Optical element and manufacturing method thereof

An optical element comprises a substrate (1), a passive waveguide (10) disposed in the substrate, and a laser waveguide (20) disposed in the substrate. The laser waveguide directly contacts with the passive waveguide over a contacting surface (15) to provide a butt coupling between the passive waveguide and the laser waveguide. A step extending is provided between an upper edge (11) of the passive waveguide and an upper edge (21) of the laser waveguide. A covering (30) is also disposed on the passive waveguide. The optical element comprises a substrate, a passive waveguide disposed in the substrate, and a laser waveguide disposed in the substrate. The laser waveguide directly contacts with the passive waveguide over a surface of contact for providing a butt coupling between the passive waveguide and the laser waveguide. A step extending is provided between an upper edge of the passive waveguide and an upper edge of the laser waveguide. A covering is also disposed on the passive waveguide, where the covering and the substrate are provided together with a cladding of lower refractive index around the passive waveguide. A hollow space (35) is provided between a lower edge (31) of the covering and the upper edge of the laser waveguide. An independent claim is included for a method for manufacturing optical element: (A) patterning an optical grating into a substrate; (B) depositing a photoresist onto the patterned substrate having a predetermined thickness; (C) removing photoresist from a region above the optical grating by lithography to produce a master mold; (D) producing a topological negative mold of master mold; (E) transferring an optical grating pattern of the topological negative mold to another substrate; (F) forming passive waveguide in the latter substrate; (G) depositing laser material onto the transferred optical grating pattern to produce laser waveguide in direct contact with the passive waveguide; and (H) providing covering on the upper edge of the passive waveguide.