High quality of optical coating

A key feature of the optical coating is its surface quality. Optical surface quality determines the performance of the device itself. High-quality optical coatings starting in super smooth polished optical substrate, and its rms roughness is 0.05 nm. Conventional optical coating will increase the roughness of the substrate surface roughness depends on the technology used. For example, the thin film deposited by evaporation surface roughness is typically 1 nm, zinc oxide and ion assisted deposition techniques to obtain the surface roughness is typically 0.4 nm. Ion beam sputter deposition of thin film surface roughness and the super-polished substrates equivalent of 0.05 nm.High quality optical coating should have low optical loss. Loss within the optical coating from scattering and absorption. Films produced by ion beam sputtering with low total loss, that require sophisticated instruments to measure them. There has two independent research group published its measurement of the loss is less than two millionths of a mirror. Both groups are using the Oxford Instruments ion beam sputtering deposition system to produce a mirror. Laser bar mirror coating: laser resonator is posed by some mirror. Laser beam from a mirror through the most efficient emitted, it is necessary to limit the beam at one end, while the other end so that the minimum loss to the outgoing beam. This can be increased in the anti-reflection layer of the surface membrane (HR), titanium dioxide an increase in exit surface layer antireflection coating (AR) to achieve. As the laser resonator rod coating each side is different, so the laser rod must be installed in a reliable device, the first surface for deposition of a coating, and then flip the laser rod, on the other side for deposition coating, At the same time to ensure that the surface is not contaminated before.