CVD diamond optical components, multi-spectral properties and performance at elevated temperatures.

Chemical Vapour Deposited (CVD) Diamond can now be fabricated in the form of large planar windows (up to 120mm in diameter and 2mm thick) and hemispherical domes (up to 70mm in diameter) suitable for operation as ultra-robust, aerospace infrared (IR) apertures. This paper describes the optical and IR properties of such components, reporting in detail on the short wavelength IR properties and the variation in optical properties with sample temperature. Flat CVD diamond windows are currently being used with great success in a number of long wavelength infrared (LWIR) applications. The paper discusses how the optical properties, such as absorption and scatter, differ when operating at shorter wavelengths and speculates on the usefulness of CVD diamond as a multi-spectral window. Aerospace windows and domes are often required to perform at elevated temperatures and thus the change in IR properties under these conditions is of interest. The paper describes a series of studies into the transmission, emission and absorption of CVD diamond as a function of temperature, using spectroscopic techniques. The extension of the CVD diamond growth and processing technologies to geometries other than flats is at an advanced stage of development and data on the IR properties of state-of-the-art, high geometrical tolerance diamond domes will be presented, including MTF assessment at 10.6mum.