Manufacturers of optical coatings and components

Single layer anti-reflection (SLAR) coatings are the simplest and least expensive AR coatings since they employ only one layer that is phase matched to provide destructive interference between the film material and substrate.  The SLAR has the advantage of providing anti-reflective properties over a fairly broad wavelength region, although SLAR coated surfaces are typically more reflective than those coated with more sophisticated anti-reflection coatings.

Single layer MgF2 on 1.52 index glass at normal incidence