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Proceedings Paper

Development of active gratings for the spectral selection of ultrafast pulses
Author(s): Fabio Frassetto; Stefano Bonora; Giovanna Brusatin; Gioia Della Giustina; Salvatore Stagira; Caterina Vozzi; Erika Zanchetta; Luca Poletto
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Paper Abstract

We present the design, realization and characterization of active deformable gratings for extreme-ultraviolet monochromators for ultrashort pulses. The core device consists of a bimorph deformable mirror on the top of which a diffraction grating with laminar profile is realized by UV lithography. The curvature radius of the grating substrate can be varied changing the voltage applied to an underlying piezo-actuator. The advantage of this technology is to provide gratings with high optical quality, robust, compatible with any coating deposition and realized with only vacuumcompatible materials. We present the characterization of a time-delay compensated monochromator realized with these devices, showing that the active grating can optimize the beam focusing through its rotation and deformation. Two equal active gratings have been mounted in a compensated configuration to realize a grazing-incidence double-grating monochromator for the spectral selection of ultrashort pulses and the simultaneous compensation of the pulse front-tilt given by the diffraction. The wavelength scanning is performed by the first grating through rotation. The radiation is focused on the intermediate plane, where a slit carries out the spectral selection. Finally, the second grating compensates for the pulse front-tilt given by the first one. The spectral focusing of both gratings is maintained at the different wavelengths through the variation of the radii of curvature. The instrument has been tested with a Ti:Sa laser operated at 800 nm. We have been able to demonstrate that the double-grating configuration with active gratings compensates for the pulse front-tilt, that is reduced from 1 ps at the intermediate plane to 100 fs at the output. The final value is limited by the group delay dispersion of the monochromator within the 10-nm bandwidth of the laser. A configuration for the selection on XUV ultrashort pulses has been theoretically studied and the expected performances presented. Active gratings may be considered as a cheaper and more flexible alternative to standard gratings for the realization of extremeultraviolet monochromators for ultrafast pulses, such as free-electron lasers and high-order laser harmonics.

Paper Details

Date Published: 3 May 2013
PDF: 7 pages
Proc. SPIE 8778, Advances in X-ray Free-Electron Lasers II: Instrumentation, 87780C (3 May 2013); doi: 10.1117/12.2019980
Show Author Affiliations
Fabio Frassetto, CNR, Institute of Photonics and Nanotechnologies, Politecnico di Milano (Italy)
Stefano Bonora, CNR, Institute of Photonics and Nanotechnologies, Politecnico di Milano (Italy)
Giovanna Brusatin, Univ. degli Studi di Padova (Italy)
Gioia Della Giustina, Univ. degli Studi di Padova (Italy)
Salvatore Stagira, CNR, Institute of Photonics and Nanotechnologies, Politecnico di Milano (Italy)
Caterina Vozzi, CNR, Institute of Photonics and Nanotechnologies, Politecnico di Milano (Italy)
Erika Zanchetta, Univ. degli Studi di Padova (Italy)
Luca Poletto, CNR, Institute of Photonics and Nanotechnologies, Politecnico di Milano (Italy)


Published in SPIE Proceedings Vol. 8778:
Advances in X-ray Free-Electron Lasers II: Instrumentation
Thomas Tschentscher; Kai Tiedtke, Editor(s)

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