Apparatus comprising an optical gain device, and method of producing the device

Method of making an article that comprises an optical gain device that comprises optical waveguide means comprising a core and a cladding, associated with each of said core and cladding being a refractive index, the refractive index of the cladding being lower that the refractive index of the core, such that the waveguide means are adapted for guiding signal radiation of wavelength .lambda..sub.s, and the gain device further comprises coupling means for coupling pump radiation of wavelength .lambda..sub.p <.lambda..sub.s into the optical waveguide means,

• Characterized in that the method comprises
• (a) providing a substrate having a major surface, with a layer comprising core material on the major surface;
• (b) exposing at least a portion of said layer to rare earth ions such that at least a major portion of said ions is caused to be implanted into said core material;
• associated with the rare earth ions implanted into the core material is a concentration of rare earth ions, including a maximum concentration in a given region of the core material;
• (c) patterning, either before or after step (b), said layer such that the core of said optical waveguide means results;
• associated with the core is a cross section and a core surface that is not adjacent to the substrate surface;
• and wherein the method is practiced such that the rare earth ions are distributed in the core such that, in a given cross section of the core, the maximum concentration of rare earth ions in a first region is at least twice as high as the maximum concentration of the rare earth ions in a second region of the cross section, with at least a part of the second region disposed between the first region and a part of the core surface that is not adjacent to the substrate surface;
• and
• (d) depositing cladding material.