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Proceedings Paper

Adaptive wavefront control based on genetic algorithm for the enhancement of high-order harmonic generation driven by two-cycle laser pulses
Author(s): Stefano Bonora; Michele Pascolini; Luca Poletto; G. Sansone; S. Stagira; Caterina Vozzi; Mauro Nisoli; Paolo Villoresi; Giuseppe Tondello; Sandro De Silvestri
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Paper Abstract

In this work we report on the optimization of the conversion efficiency of the harmonic generation process, by adaptive control of the wavefront of sub-10-fs light pulses, obtained by using a deformable mirror and a genetic algorithm. Sub-10-fs, 0.2-mJ energy light pulses, generated by the hollow-fiber compression technique, were focused in the gas target (argon or neon) by a 250-mm focal-length mirror. Pulse wavefront correction has been achieved by using a deformable mirror (DM) controlled by 37 actuators distributed on a honeycomb pattern of 15 mm diameter. The harmonic radiation was observed by a soft-X-ray spectrometer, with double output: time-integrated high-resolution bidimensional focal-plane image and real-time (1 kHz) intensity of a suitable spectral region. This latter signal was used as fitness parameter for the genetic algorithm; an initial population of DM configurations was initialized with random values of the actuator signals. A new generation of DM configurations is derived from ordering, selection and transformation of previous generation, up to the convergence to the fittest individual. Strong enhancement of the harmonic conversion efficiency of about one order of magnitude, as well as a significant extension of the harmonic spectrum is evident. The initial and optimal wavefronts of the fundamental beam were measured both in real time with an Hartmann sensor and off-line using a ZYGO interferometer. Using the measured beam wavefront were calculated the spatial characteristics of the fundamental beam.

Paper Details

Date Published: 1 June 2004
PDF: 8 pages
Proc. SPIE 5333, Laser Resonators and Beam Control VII, (1 June 2004); doi: 10.1117/12.529263
Show Author Affiliations
Stefano Bonora, LUXOR-INFM, Univ. degli Studi di Padova (Italy)
Michele Pascolini, LUXOR-INFM, Univ. degli Studi di Padova (Italy)
Luca Poletto, LUXOR-INFM, Univ. degli Studi di Padova (Italy)
G. Sansone, ULTRAS-INFM (Italy)
Politecnico di Milano (Italy)
S. Stagira, ULTRAS-INFM (Italy)
Politecnico di Milano (Italy)
Caterina Vozzi, ULTRAS-INFM (Italy)
Univ. degli Studi di Milano (Italy)
Mauro Nisoli, ULTRAS/INFM (Italy)
Politecnico di Milano (Italy)
Paolo Villoresi, LUXOR-INFM, Univ. degli Studi di Padova (Italy)
Politecnico di Milano (Italy)
Giuseppe Tondello, LUXOR-INFM, Univ. degli Studi di Padova (Italy)
Sandro De Silvestri, ULTRAS-INFM (Italy)
Politecnico di Milano (Italy)

Published in SPIE Proceedings Vol. 5333:
Laser Resonators and Beam Control VII
Alexis V. Kudryashov, Editor(s)

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