The cavity (or resonator) mirrors are high reflecting (HR) or output coupling (OC) mirrors for gas or solid state lasers resonators. Combined they generate the necessary feedback for the stimulated emission of the lasing wavelength. The HR mirror has a reflectivity close to 100 % for the Laser wavelength and high transmission for the pump light wavelength, while the output coupling mirror reflects the Laser beam to a certain level. Cavity mirrors can be planar or concave/convex mirrors made of N-BK7 or fused silica. The coating technology is chosen according to the requirements. Ion Beam Sputtering (IBS) can be applied if necessary.