Copper-doped waveguides in glass substrates

Abstract

We have studied fabrication and properties of copper ion- exchanged waveguides fabricated in various types of special soda-lime silicate glass as well as commercial optical glass substrates. The ion exchange was performed in melts containing either Cu<SUP>I</SUP> or Cu<SUP>II</SUP> at temperatures from 350 degrees C to 500 degrees C for times ranging from 5 minutes to 21 hrs. Optical properties of the fabricated waveguides were studied using mode spectroscopy and photoluminescence spectroscopy and composition of the waveguides was determined by SEM, RBS, EPR and ESCA. After the ion exchange the refractive index increased, according to fabrication conditions, up to (Delta) n equals +0.0693 and the guides supported up to 16 TE and TM modes. The Cu<SUP>I</SUP> $ARLR Cu<SUP>II</SUP> redox reaction during the fabrication depended strongly on the composition as well as the temperature of the reaction melts. In the Cu<SUB>2</SUB>Cl<SUB>2</SUB>ZnCl<SUB>2</SUB> melts the oxidation of Cu<SUP>I</SUP> to Cu<SUP>II</SUP> was strongly hampered, so that Cu<SUP>I</SUP> prevailed in the waveguiding region. These samples exhibited the most intensive blue-green luminescence, in spite of those fabricated using the Cu<SUP>II</SUP>-based reaction melts, where practically no blue-green luminescence was observed. ESCA measurement revealed an easy charge transfer between the both oxidation states of copper in the very surface regions of the samples.