Optical waveguides in InGaAsP and InP

Method for manufacturing an optical device comprising an optical waveguide in a semiconductor material, the method comprising

• (a) depositing a patterned processing layer on a surface of said semiconductor, thereby defining the waveguiding region,
• (b) maintaining the semiconductor material carrying the processing layer at a temperature of at least 400.degree. C. for at least about one hour, and
• (c) contacting during at least part of the time of step (b) at least a part of the semiconductor carrying the processing layer with metal atoms, where the metal is selected from the group consisting of Si, Ge, Sn, Te, Se, As, P, Sb, Cd, Zn, In, Ga, Al, Fe, Cr, Cu, Ag, and Au whereby said metal atoms diffuse into said material thereby defining an optical waveguide.