Manufacturing techniques and composite structures that are able to meet increasing demanding requirements for large-scale crystal composites (e.g., greater than 100-200 mm in dimensions) that can be manufactured within reasonable time frames. A method of making an optical composite comprises providing first and second components to be bonded along respective surfaces, treating at least one component over at least a portion of the respective surface, and thereafter, bringing the first and second components into optical contact for bonding along the surface having the treated layer. Treating can include one or more of processing the component to provide a porous interface layer, processing the component to form a pattern of channels on the surface to be bonded, and providing an optical coating on the surface to be bonded.