Suppression of the spectral selectivity of two-layer phase-relief diffraction structures

Comparison of electromagnetic and scalar methods for evaluation of efficiency of diffractive lenses for wide spectral bandwidth

“…Therefore, all the results obtained in the framework of this theory are valid for any microstructure period. When using SDT, we could see that when the angle of radiation incidence θ = 0, the optimal values of the relief depths are [3]. Thus, for optimal depths, we selected the depths ensuring the maximum possible value of the DE at its minimum point within the given spectral range.…”

“…1) [3,12]. Such a microstructure composed of two commercially available optical plastics, polymethylmethacrylate (PMMA) and polycarbonate (PC), provides almost complete suppression of the spectral DE dependency in a wide spectral range of λ μ ≤ ≤ μ 0.4 m 0.7 m at a constant value of the angle of incidence.…”

“…(3), it is clear that in case of a one-layer-relief phase microstructure, the relief depth is comparable with the wavelength. In the case of a structure with a suppressed spectral DE dependency, the total relief depth can exceed the minimum wavelength of the given spectral range λ min tenfold due to a small difference in the refractive indices of the used materials (see, for example, [3]). …”

“…Unfortunately, in the case of a one-layer-relief phase microstructure, it can be performed on one wavelength only and only for one angle of incidence. To reduce the dependence of the DE in working order diffraction on a function of wavelength and angle of incidence the microstructure with multiple reliefs and layers are used (see, for example, [2][3][4]). Obviously, this technique will automatically lead to the decrease of the DE in the side diffraction orders due to the minimization of the dependence of the optical path difference on the wavelength and the angle of incidence in the predetermined range of these parameters.…”

Diffractive–refractive correction units for plastic compact zoom lenses

“…It is easy to show that within the visual spectral region, this decrease can be 7%-8%, depending on the material DL microstructure [26]. The dependence of the diffraction efficiency of the DL at the wavelength may be substantially reduced by using a multilayer, in particular, a two-layer-relief phase microstructure [5,25,[27][28][29].…”