substrates, such as ultraviolet light cured polymer substrates, quartz, gallium arsenide, indium phosphide and crystalline silicon and which when used in optical waveguide structures have optical attenuation values less than 3 dB per cm after heating at 300??? C. for 3 minutes and preferably have optical attenuation values less than 3 dB per cm after heating at 300??? C. for 5 minutes.