Effects of static load and residual stress on fused silica direct bonding interface properties

Abstract

AbstractDefect free direct bonding of rigid and large area glass samples, such as prisms, becomes increasingly important for the manufacturing of modern optical and optomechanical components. Typically, in order to apply a static load during the annealing step, specialized heat-resistant pressure mountings are required. This makes manufacturing effortful and cost-intensive. In this paper, we present plasma activated bonding experiments conducted on fused silica plates where residual stress has been introduced prior to the contacting step and where annealing is performed with and without a static load. We find that in case of a sufficiently smooth surface, bonding strength is insensitive towards residual stress or static load, or more precisely, towards the interface stress. Furthermore, the residual Fresnel reflection losses of the realized bonding interface were optically measured and they amount to only $$10^{-6}$$ 10 - 6 . We propose that a consideration of the change in Gibbs free energy, dG, allows qualitatively predicting the resulting bonding strength and its spatial distribution, where dG is determined by surface energy and interface stress. At the end of this article, conceivable applications are discussed.