Effect of CO 2 -laser power density on the absorption coefficient of polycrystalline CVD diamonds

The effect of 1-s irradiation of an uncooled polycrystalline CVD diamond plate by a focused cw CO 2 laser beam with a power density of 300 – 800 kW cm −2 is investigated. The absorption coefficient of the sample at a power density of 800 kW cm −2 is found to be 0.035 cm −1 larger as compared with that at 300 kW cm −2 , which is related to the temperature dependence of its phonon-induced absorption with a change in temperature from 44 to 100 °C. It is shown that polycrystalline diamond, in contrast to other optical materials, does not exhibit nonlinear (avalanche-like) rise in absorption at high CO 2 -laser power densities, at least up to 800 kW cm −2 .