The reflectivity of an optical surface can be reduced by the addition of one or more non-absorbing dielectric films. An anti-reflective coating will also enhance transmission in a series of optical components.
A single layer (quarter wave) of MgF2 will typically reduce reflectivity (glass with a 1.52 index) from 4% to 1.5%
A multi-layer AR design can reduce reflection from 4% to .3% in the visible
A “V” design can reduce reflection to .1% across a narrow band of wavelength
Anti Reflective coatings can be designed to function in specific bands such as UV, IR and NIR.