(Invited) Glass-Glass Direct Bonding

Glass-glass direct bonding is closely rated to proven processes in Si-Si wafer bonding. We describe plasma-assisted hydrophilic direct bonding of different glass materials for various applications in optical and high precision engineering. Dedicated ""zero-expansion"" glass has been used in constructive type ""sandwich"" bonding of stiff platforms and mirrors as required in space or lithography applications. For transmissive optical applications in the visual and near infra-red spectral range, fused silica is the material of choice and the technology of direct bonding allows to join optical surfaces without an interlayer in a perfectly materials adapted manner. Binary gratings were fabricated and successfully encapsulated in this way for pulse shaping in high power laser devices. The corresponding activities at Fraunhofer IOF are presented and results of supportive laser damage and transmission efficiency measurements for optical characterization are outlined.