Diffraction efficiency

About: Diffraction efficiency is a research topic. Over the lifetime, 10320 publications have been published within this topic receiving 158298 citations.

Multichannel optical diode with unidirectional diffraction relevant total transmission

Abstract: We will show that broadband unidirectional optical transmission with a total transmission maximum inside the band can be obtained for linearly polarized incident waves in the nonsymmetric photonic crystal gratings made of isotropic linear materials at a fixed nonzero or zero angle of incidence. Being based on the merging of diffraction and dispersion effects, the basic physical mechanism studied exploits the transmission channels associated with higher orders, for which asymmetry in the coupling conditions at the two grating interfaces appears when spatial inversion symmetry is broken. Total transmission in one direction and zero transmission in the opposite direction can be obtained due to hybridization of Fabry-Perot type resonances with a diffraction anomaly that yields a diode-like operation regime. Single-beam deflection and two-beam splitting can be obtained, for which transmission can be (nearly) total, if the corrugated side is illuminated. In contrast to the previous studies, it is also shown that unidirectional transmission can appear only at a fixed frequency and only due to diffractions, when total transmission occurs at the noncorrugated-side illumination, being in agreement with the Lorentz Lemma.

3D structures using surface relief gratings of azobenzene materials

Abstract: We present here a method of step-by-step 3D structure fabrication using holographic formation of surface relief gratings (SRG) in azobenzene-containing layers alternated with spacer layers. The method possesses opportunities that could not be realized by other holographic approaches, especially the variation of grating periods or the shape of the SRG in different layers (hierarchical structures), full flexibility of the structure type and parameters. One of the main problems to be solved is the compatibility of active azobenzene-containing polymers and a material for the spacer layers. We resolved the problem and found active and spacer polymers with excellent compatibility. The materials allow the preparation of films with good optical quality and the inscription of SRG with modulation amplitudes up to 1 µm in reasonable time. The refractive index difference between active and spacer polymers (currently 0.15–0.2) results in appreciable diffraction efficiency of the SRG after the application of the spacer layer. The phase correlation technique between adjacent layers has been developed. The fabrication of multilayer structures has been demonstrated by examples of a combination of linear, tetragonal and hexagonal SRG with three active layers and hierarchical structures.

Robust design method for highly efficient beam-shaping diffractive optical elements using an iterative-Fourier-transform algorithm with soft operations

Abstract: Beam-shaping diffractive optical elements give a desired intensity distribution in the diffraction plane over areas much larger than the diffraction limited spot size. Such elements can be designed using geometrical optics methods or iterative-Fourier-transform algorithms (IFTAs). The usefulness of geometrical optics methods is considerably limited for two reasons: first the number of cases for which a solution exists is small and second the design solution, if it exists, often does not work in practice. Then IFTAs can be used. They are applicable for any desired intensity distribution in the diffraction plane with any intensity cross-section of the incident beam. The IFTA presented in this paper uses a novel set of operations that introduce a minimum disturbance of the fields while still leading to an improved performance. This makes the method robust, insensitive to stagnation and capable of iteratively distributing an increasing portion of the light in the diffraction plane into the desired ar...

Integral method for echelles covered with lossless or absorbing thin dielectric layers.

Abstract: We make a generalization of the integral method in the electromagnetic theory of gratings to study diffraction by echelles covered with dielectric lossless or absorbing layers. Numerical examples are given that show that, as in the resonance domain, the diffraction efficiency is more complicated than being a simple product of lossless diffraction efficiency curves and plane surface reflectivity.