Manufacturing and Characterization of Buried Optical Waveguide Stack in Glass Substrate

On silicate optical glass substrate, buried optical waveguide stacks were obtained. The stacks were composed of two layers of buried optical channel waveguide at different depth beneath the glass substrate surface, and each layer was manufactured by thermal Ag+/Na+ ion-exchange and field-assisted ion-diffusion. Microstructure of the optical waveguide chips was observed with optical microscope, and insertion loss of each layer in waveguide stacks is measured. Results show that the buried waveguide stack is composed of two layers of buried waveguide with their core center located at 14 mu m and 35 mu m, respectively. Beneath the glass surface, core dimension of top layer and bottom layer waveguide are 12 mu m x 7 mu m and 9 mu m x 8 mu m, respectively. Waveguides in both layers are single mode at operating wavelength of 1.55 mu m. There is no directional coupling observed between waveguides at different layers. Insertion loss characterization indicates that propagation loss of both layers in the stack is 0.12 dB/cm, and coupling losses with single mode fiber are 0.78 dB/facet and 0.73 dB/facet, for top and bottom layer waveguides, respectively. The analysis suggests that this kind of optical waveguide stack is promising in application of high density integration of glass-based optical chip.