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(a) Sketch of the experimental set-up. AOM: acousto-optic modulator; SHG: second-harmonic generation stage; PC: polarization control stage; MO: microscope objective. The sample is a PTR glass whose composition is given in the text. (b) Unpolarized white light imaging of the photomodified glass using pulses and increasing fluence values F = 6.28, 7.26, 7.73, 8.15, 8.25, 8.35, 8.41, and 8.46 J.cm−2 that refer to numbering from 1 to 8, respectively. (c) Crossed linear polarization white light imaging with inverted grayscale, where LP and LP’ refer to the direction of the linear polarizers. (d) Crossed circular polarization imaging at 532 nm wavelength. Here, m.
Sketch of the optical vortex generation from spin-to-orbital optical angular momentum conversion for the geometry used for the evaluation of the fs-laser-induced radial birefringence, where the photomodified region is assumed to be a cylinder of height H and diameter D with radial distribution of the optical axis. The input field is circularly polarized (here right-handed) and the output light field component whose polarization state is orthogonal to the input one carries a phase singularity with topological charge two, as illustrated by the equiphase surfaces.
Diameter D of the thermally affected zone (a), spin-to-orbital angular momentum conversion efficiency η (b), and the estimated radial birefringence Δn (c) [see text for details] as a function of the fluence. Data are shown for different polarization states of the writing beam as indicated in the legend panel.
(a) Array of spin-to-orbital optical angular momentum converters over 1 cm2 area, each individual converters being obtained using pulses, a fluence F = 8.46 J.cm−2, and depth m. (b) Enlargement on array of optical vortices obtained at the output of the sample at 532 nm wavelength. (c) Enlargement of panel (b) exhibiting the phase profile of the obtained optical vortices with topological charge two. (d) Zoom on the phase spatial distribution of a single optical vortex.
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