AFB~R CVD diamond composites with laser materials

摘要

The thermal conductivity of CVD diamond with about 18-25 W/cm.K at room temperature is one of the properties that makes diamond a unique material. Since thermal management of solid state lasers becomes increasingly difficult when scaling up to high average power, CVD diamond is an ideal heat spreader to conduct heat away to a heat sink. At the same time, diamond is transparent between 230nm and the far infrared, with two-photon absorption bands between 2.5 and 6 μm.Adhesive-Free Bonding (AFB~R) of CVD diamond sheet has been demonstrated to be possible because Van der Waals attractive forces constitute the principal bonding mechanism of AFB~R composites. The coefficient of thermal expansion of CVD diamond is with 0.8 - 1.0 × 10~(-6)/℃ much lower than any of the common solid state laser media, with YAG being about 8.2 × 10~(-6)/℃. The non-localized nature of Van der Waals bonds allows almost perfect stress equilibration without delamination, while any other bonding technique would be expected to result in highly stressed composites. Bonding mechanisms, experimental observation of stress relief and parameters for successful AFB~R CVD diamond/ single crystal composites at the interface will be reported, with relevance for disk, slab and waveguide solid state laser geometries at ambient and cryogenic temperature.