Diamond optical components for high - power and high-energy laser applications

High-power and high-energy laser systems have firmly established their industrial presence with applications that span materials processing; high-precision and high-throughput manufacturing; semiconductors, and defense. Along with high average power CO2 lasers operating at wavelengths of similar to 10 microns, solid state lasers and fiber lasers operating at 1 micron wavelength are now increasingly being used, both in the high average power and high energy pulse regimes. In recent years, polycrystalline diamond has become the material of choice when it comes to making optical components for multi-kilowatt CO2 lasers at 10 micron, outperforming ZnSe due to its superior thermo-mechanical characteristics. For 1 micron laser systems, fused silica has to date been the most popular optical material owing to its outstanding optical properties. This paper characterizes high-power/high-energy performance of anti-reflection coated optical windows made of different grades of diamond (single crystal, polycrystalline) and of fused silica. Thermo-optical modeling results are also presented for water cooled mounted optical windows. Laser-induced damage threshold tests are performed and analyzed. It is concluded that diamond is a superior optical material for working with extremely high-power and high-energy laser beams at 1 micron wavelength.