The process for making alumina pieces by injection molding, comprises preparing a master mixture having a powder mixed with a polymeric binder (3-50%) and solubilized in an aqueous water solvent, injecting the master mixture in a mold under pressure, cooling the mold, removing the mixture from the mold and then washing, and sintering the mixture. The mixture is maintained at a temperature greater than an evaporation temperature of solvent during pressing, and has nanopowder, whose particle size is lower than 100 nm.

An optical structure can include a nanocrystal on a surface of an optical waveguide in a manner to couple the nanocrystal to the optical field of light propagating through the optical waveguide to generate an emission from the nanocrystal.