Zero Order Gratings: Homogenisation and the Effective Index Model
Surface relief high spatial frequency gratings, commonly referred to as Zero Order Gratings (ZOGs) can be used to produce layers with physical properties intermediate between those of the groove (trench) material and the material in the step, or comb. Such artificial material layers find a wide range of applications as antireflection coatings and birefrigent layers for polarization elements. In this paper the development of approximate homogenization methods to model ZOGs are discussed and placed in the context of rigorous theories. Emphasis is placed on examining the range of validity of the Effective Index Model (EIM) for lamellar gratings made in Si, n(s) = 3.41, for use with CO(2) laser light wavelength = 10.6 mm. The predicted reflection intensities for both polarizations of the best possible EIM result is examined in comparison with more rigorous results as a function of grating period, for various grating depths, duty cycles and small angles of incidence.
Bibliographic Reference: EUR 16373 EN (1996) 27pp., FS, free of charge
Availability: Available from the Public Relations and Publications Unit, JRC Ispra, I-21020 Ispra (IT)
Record Number: 199610530 / Last updated on: 1996-05-13
Original language: en
Available languages: en