Optical waveguide in thermally developed photo-thermo-refractive glass substrate

Abstract

Photo-thermo-refractive (PTR) glasses are a new category of materials that possess special characteristics of refractive index decrement induced by UV exposure and subsequent thermal development. PTR glasses have been extensively utilized for the fabrication of various volume Bragg grating and are expected to play an important role in the construction of high-performance guided-wave devices. Investigations on the optical waveguide fabrication process in thermally developed PTR glass Substrate are demonstrated. Optical grade PTR glass of the SiO₂-Al₂O₃-Na2O-ZnO-NaF-KBr system and doped with Ce, Ag, Sb, and Sn, is firstly melted, and then glass wafers made of the homemade PTR glass are UV exposed and thermal developed, during which nanometer-sized NaF crystalline is formed in these PTR glass wafers. The thermally developed PTR glass wafers are finally subjected to conventional glass-based optical waveguide melt salt thermal Ag⁺/Na⁺ ion exchange and subsequently field-assisted ion diffusion for waveguide fabrication. Results exhibited that buried channel optical waveguide, with Ag⁺ doped waveguide core dimension of approximately 9.5μm×8.6μm buried 5.2μm under the substrate surface can be obtained by the current procedure. In the current paper, the feasibility of implementing buried waveguide fabrication in thermally developed PTR glass materials is experimentally demonstrated. Since the shape and dimension of the waveguide core is well matched to that of single-mode fiber, and the buried waveguide eliminates scattering loss at the glass substrate surface, the buried optical waveguide is expected to find applications in guided-wave device fabrication.