Abstract
A new rigorous vector-based design and analysis approach of diffractive lenses is presented. It combines the use of two methods: the Finite-Difference Time-Domain for the study in the near field, and the Radiation Spectrum Method for the propagation in the far field. This approach is proposed to design and optimize effective medium cylindrical diffractive lenses for high efficiency structured light illumination systems. These lenses are realised with binary subwavelength features that cannot be designed using the standard scalar theory. Furthermore, because of their finite and high frequencies characteristics, such devices prevent the use of coupled wave theory. The proposed approach is presented to determine the angular tolerance in the cases of binary subwavelength cylindrical lenses by calculating the diffraction efficiency as a function of the incidence angle.
Highlights
Subwavelength diffractive optical elements (SWDOE) refer to diffractive optical elements (DOE) that have features sizes smaller than the wavelength of the illumination light
A new rigorous vector-based design and analysis approach of diffractive lenses is presented. It combines the use of two methods: the Finite-Difference Time-Domain for the study in the near field, and the Radiation Spectrum Method for the propagation in the far field
This approach is proposed to design and optimize effective medium cylindrical diffractive lenses for high efficiency structured light illumination systems. These lenses are realised with binary subwavelength features that cannot be designed using the standard scalar theory
Summary
Subwavelength diffractive optical elements (SWDOE) refer to diffractive optical elements (DOE) that have features sizes smaller than the wavelength of the illumination light. Prism-like gratings [4], antireflective surfaces [5], computer generated holograms [6], array illuminator [7] or diffractive lenses [8,9,10] designed by effective medium theory have been introduced in the past years These elements are made up of subwavelength structures that define an effective medium. By varying the lateral feature size, the index of refraction of the effective medium, defined by the subwavelength structures, varies and creates a SWDOE corresponding to a multilevel element. In this case, light “sees” a medium containing an effective modulation of the refractive index. A f/6 subwavelength diffractive lens has been designed by pulse width modulation and has been studied by the FDTD-RSM method that we propose
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