Adhesive-free bond (AFB) CVD diamond/sapphire and CVD diamond/YAG crystal composites

We report on adhesive-free bonded (AFB"R") CVD diamond surfaces of 2 to 3 nm rms roughness to sapphire, YAG and optically coated YAG surfaces to form robust and stress free composite components. Considering the high thermal conductivity of CVD diamond with respect to YAG or sapphire, AFB"R" diamond/sapphire and diamond /YAG composites can be ideal components for thermal management of high power solid-state laser systems of certain design configurations. We ascribe the attractive bonding forces at the interface between diamond and sapphire and other single crystals such as YAG and spinel largely to Van der Waals forces. Contrary to chemical bonds, Van der Waals forces consist of non-localized dipole-dipole interactions that manifest their long range effects by allowing relative movement between two bonded surfaces of different coefficients of thermal expansion, thus avoiding local stress during thermal cycling. CVD diamond surfaces result in a much wider compatibility range for forming stress-free or low-stress composites compared to alumina compound single crystal counterparts. Feasibility of forming AFB"R" stress- free interfaces between diamond and optically coated oxide surfaces marks an important step in widening the range of AFB"R" for solid state laser and electronic applications.