Anti-reflection in the visible and near-IR wavelengths can be
achieved with a variety of different deposited compounds.
Silicon monoxide, yttrium fluoride, and magnesium fluoride
are three popular low-index-of-refraction materials. Silicon
monoxide is used primarily in the infrared wavelengths, while yttrium fluoride and magnesium fluoride are used mostfrequently in the visible region. The primary drawback of thesecompounds is their durability. While anti-reflective coatings
utilizing either of these can be cleaned, care must be taken not
to cause damage. Anti-reflective coatings also can be made
using harder oxide compounds that are more durable, but they
tend not to perform quite as well and require that the optic be
subjected to high temperatures during deposition. In general,
the more energetic (higher temperature) the process that is
used to deposit the anti-reflective coating, the more durable
the resultant coating is.