Optical bonding of tellurite glass film on silicate glass

Abstract Tellurite glass thin film was successfully bonded on a silicate glass substrate by the direct‐bonding (DB) method. Glass film (thickness 1‐3 μm) was fabricated by the glassblowing technique and the DB process was performed at room temperature at relative humidity (RH) of 62% or 15%. The surface adhesive strengths of the glass films bonded at 15% and 62% RH were measured as 250 and 96 mJ/m ² , respectively, by the Obreimoff‐Metsik method. The hydroxyl (–OH) functional groups on the interface between the film and silicate glass were analyzed by Fourier‐transform infrared spectroscopy. The major bonding forces between the tellurite thin film and silicate glass were hydrogen bonds at 62% RH and bonds between Te on the tellurite glass and O on the silicate glass were concerned at 15% RH. These forces, contributed by Si–OH, were important for bond formation at 62%. The large amounts of water and OH groups on the silicate glass, determined by thermogravimetric analysis, indicated a weaker bonding process at 62% RH. This work will contribute toward reliable, high‐integrity components for integrated optical circuits, which are increasingly needed for high‐throughput data transfer.