Inhibiting crystal growth in optical waveguide structures, for reduced absorption and insertion loss using optically-passive dopants in the core

A method of forming an optical waveguide structure, comprising:

• selecting one or more dopant materials configured to be optically passive in a first range of optical signal wavelengths;
• forming substrate cladding layer;
• performing a high temperature deposition of a waveguide core material including the selected dopant materials on the substrate cladding layer;
• etching the waveguide core material to define a waveguide core;
• and
• subsequent to annealing the waveguide core material and etching the waveguide core material,
• forming an upper cladding material over the defined and annealed waveguide core.

An optical waveguide, comprising:

• a substrate cladding;
• an upper cladding formed over the substrate cladding;
• and
• a waveguide core formed between the substrate cladding and upper cladding, the waveguide core including:
• one or more first dopant materials configured to be optically active in a first set of one or more wavelength ranges;
• and
• one or more second dopant materials configured to optically passive in the first set of one or more wavelengths ranges and configured to not have ion-to-ion interactions that hallow energy transfer between the second dopant materials and the first dopant materials.