Stress Induced Birefringence Of Glass-To-Metal Bonded Components

We report on the stress induced birefringence of 10 mm BK7 cubes bonded to 15 mm x 15 mm x 5 mm aluminium coupons using ultrashort pulse laser welding, hydroxide catalysis bonding, and an optical adhesive using a standard approach used in industry. It was observed that ultrashort pulse laser welding results in a low level of stress induced birefringence within an 85% optical aperture of the 10 mm cube. These levels are suitable for use in photography and microscopy applications as defined by the relevant ISO standard for permissible stress induced birefringence limits in optics. Hydroxide catalysis bonding was shown to approach and possibly exceed this limit, however, it must be noted that the bonding area of the hydroxide catalysis samples greatly exceeds that of the welding and adhesive bonded samples by a factor of 20 and thus will likely experience grater mechanical stress from defects on the metal surface.