Photonic substrate preparation method and photonic waveguide preparation or fabrication method

Photonic integrated circuit optical waveguide device preparation or fabrication method comprising providing a silicon substrate, depositing at least one copper gettering silicon nitride layer or material, depositing at least one optical waveguide cladding layer or material, forming at least one optical waveguide or optical waveguide structure and thermally annealing the at least one silicon substrate after the formation of the at least one optical waveguide or optical waveguide structure on the at least one silicon substrate to remove hydrogen impurities or hydrogen-related impurities from the at least one optical waveguide, and to capture or trap copper impurities of the at least one silicon substrate in the at least one copper gettering silicon nitride layer or material.