Agile management of the optical orbital angular momentum encompasses temporal, spatial, and spectral aspects that, once combined, offer new perspectives in our way to manipulate light. To date the spectral control is mainly limited to tunable operating wavelength and polychromatic capabilities. Recently, a multispectral approach has been proposed [Phys. Rev. Lett. 121, 213901 (2018)] to achieve independent orbital angular momentum state control on multiple spectral channels. Here we report on the design, fabrication and implementation of a solid-state multispectral approach that consists of arrays of optical diamond micro-metasurfaces. Obtained device exhibits superior performances with respect to the original attempt, both regarding the spectral vortex purity, the ability to deal with high photon flux, and the orbital angular momentum diversity across the spectrum. These results motivate further development of metasurface-based integrated spin-orbit photonics technologies.
We propose an approach to achieve achromatic pure geometric phase shaping of light from anisotropic media by exploiting the fundamental laws of electromagnetic waves. Its practical implementation requires a cover layer made of a dispersive isotropic medium. The approach applies to any anisotropic material and any geometric phase spatial distribution and preserves the geometric phase reversal upon the reversal of the incident polarization handedness. An experimental demonstration is made over the whole visible range but can be extended to any wavelength range without conceptual issues.
Purpose: To evaluate the performances of the motorized remote controlled multi‐leaf collimator for electron (eMLC) prototype developed in our center. To develop a Monte Carlo model of this prototype. To compare measurements and simulated data for various field configurations. Method and Materials: The model of the eMLC and the Elekta linac head for electron beam energies of 6, 8, 10, and 12 MeV was developed using the Monte Carlo package BEAMnrc/EGSnrc. The dose has been calculated in a water phantom using DOSXYZnrc software for different field sizes from 1.4×1.4 to 16.8×16.8 cm2. The measurement have been done using electron silicon diode. The simulated and measured profiles, percentage depth dose and output factor have been used to validate the Monte Carlo model. Physical parameters such as leakage trough the leaves, dose resolution, contamination dose and leaf scatter were investigated. The number of electron histories or the voxels dimensions where chosen to lead to a statistical uncertainty better than 2% (1 SD). Results: For all field configurations, the difference between measured and simulated penumbras is less than 2 mm and the agreement for output factors is within 2 %. The total leakage dose relative to the maximum central axis dose for a 9.8×9.8 cm2 eMLC field size at 12 MeV at the water surface is 1.7 %.and at dmax is 1.5%. We need to close at least two leaves in order to cut 50 % of the dose under the leaves. Conclusion: Our results showed that the eMLC and Linac Monte Carlo model is a realistic model. A combination of the Monte Carlo model and the prototype could be used to develop advanced techniques like modulated electron therapy and mixed‐beam modulated therapy.
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