ANTIREFLECTION-COATED DIFFRACTIVE OPTICAL-ELEMENTS FABRICATED BY THIN-FILM DEPOSITION

The use of thin-film deposition in the fabrication of antireflection-c oated diffractive optical elements is discussed. The antireflection co atings for these diffractive elements are optimized on the basis of an angular spectrum approach and the method of characteristic matrices. A minimum reflectivity as low as 1x10(-4) is realized using in situ co ntrolled multilayers of TiO2 and SiO2. The blazed profile of the diffr active optical elements is approximated by a stepped profile with up t o 32 phase levels. The highest measured diffraction efficiency for 32- level Fresnel zone lenses was 97%.