The optical constants n and k of thin polycrystalline films of CdSe, ZnSe, CdTe and ZnTe have been measured over the wavelength range 2000-300 nm. From analysis of the absorption data, the three cubic materials ZnSe, CdTe and ZnTe were found to have direct band-gaps with Eg=2.62, 1.50 and 2.23 eV respectively and spin-orbit splittings of the valence band of 0.48, 0.88 and 0.90 eV respectively. CdTe and ZnTe also have indirect band-gaps of 1.82 and 2.56 eV respectively. CdSe has a fundamental direct gap of 1.65 eV but the analysis of the absorption curve at higher energies was limited by the energy bands becoming non-parabolic.

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With a high-refractive-index mixed-oxide dielectric material of ZrTiO(4) and ZrO(2) [Substance H2 (Sub2) from E. Merck, Darmstadt, Germany], in combination with magnesium flouride (MgF(2)), design optimization and experimental production of low-loss antireflection (AR) coatings are carried out. Design-optimization studies that make use of these materials as constituents of a seven-layer coating system demonstrate that when the useful bandwidth of an AR coating is extended to cover a wider spectral range, the designs are in general found to have increased integrated reflection loss, higher ripple, and increased spectral instability. The experimental studies on Sub2 material show that the films have excellent optical performance over a wider process window, the advantage of which is demonstrated in the production of different AR coatings on a variety of glasses with refractive indices that range from 1.45 to 1.784 and different mechanical, thermal, and chemical properties. The manufacturing process of AR coatings shows a consistency better than 99% with respect to optical properties and durability.

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