Factors affecting the optical performance of CVD diamond infrared optics

Diamond is a unique optical material having the combination of high strength and transparency in the visible, near and far infrared regions. As a far infrared window it has already found applications in demanding environments, e.g. high-power CO 2 laser exit windows. In this paper, the far infrared optical properties of diamond are described together with the near infrared properties and the potential for using CVD diamond at shorter wavelengths is discussed. How such optical properties as absorption, scatter and image quality are related to the characteristics of CVD diamond are described. The far infrared absorption properties of diamond at elevated temperatures are presented and the mechanisms that cause the residual absorption and its temperature dependence in this region are discussed. An empirical formula for predicting the temperature-dependent absorption coefficient is presented.