Getting Better SiO2 and HfO2 Results

[100]It has been observed1 that it is beneficial to the design optical coatings to have as large a difference as practical between the high and low index materials used. Most dielectric coating designs can be achieved with just two materials in any given spectral region. It is often practical to have many types of coatings produced in a given facility using only two materials that have well developed processes.  Physical, environmental, and application considerations will temper this choice of materials. In the visible spectrum, MgF2 and TiO2 offer the greatest index difference (1.38-2.4) for materials that are reasonably robust when deposited. However, due to some of the physical, process, and environmental factors many workers in the field have chosen silica (SiO2) and hafnia (HfO2) for their coating materials (1.46-2.0).