Abstract

Antireflection coatings have been the subject of two books and of numerous scientific and technical papers.^1,2 until recently, there have been no systematic studies made to determine the optimum performance that can be achieved for a given set of specifications and coating materials. Willey has published two papers with empirical studies of this problem.^3,4 He has presented equations which, for a given set of coating materials and for an overall thickness of the multilayers, give an estimate of the lowest achievable reflectance for a normal incidence antireflection. The two equations presented by Willey are valid for a certain range of coating materials, widths of the spectral region and overall thicknesses of the multilayer. They are based on the calculated results obtained for a number of different examples . It will be shown in this paper that, whilst giving a good first estimate of the attainable results, the formulae are not accurate for any one set of coating materials.

© 1995 Optical Society of America