title: Rapid assessment of nonlinear optical propagation effects in dielectrics.
abstract: Ultrafast laser processing applications need fast approaches to assess the nonlinear propagation of the laser beam in order to predict the optimal range of processing parameters in a wide variety of cases. We develop here a method based on the simple monitoring of the nonlinear beam shaping against numerical prediction. The numerical code solves the nonlinear Schrödinger equation with nonlinear absorption under simplified conditions by employing a state-of-the art computationally efficient approach. By comparing with experimental results we can rapidly estimate the nonlinear refractive index and nonlinear absorption coefficients of the material. The validity of this approach has been tested in a variety of experiments where nonlinearities play a key role, like spatial soliton shaping or fs-laser waveguide writing. The approach provides excellent results for propagated power densities for which free carrier generation effects can be neglected. Above such a threshold, the peculiarities of the nonlinear propagation of elliptical beams enable acquiring an instantaneous picture of the deposition of energy inside the material realistic enough to estimate the effective nonlinear refractive index and nonlinear absorption coefficients that can be used for predicting the spatial distribution of energy deposition inside the material and controlling the beam in the writing process.
authors.affiliation: Laser Processing Group, Instituto de Optica (CSIC), Serrano 121, Madrid 28006, Spain.
authors.forename: J
authors.initials: J
authors.lastname: del Hoyo
authors.affiliation: Formerly at Laser Processing Group, Instituto de Optica (CSIC), Serrano 121, Madrid 28006, Spain.
authors.forename: A Ruiz
authors.initials: AR
authors.lastname: de la Cruz
authors.affiliation: Formerly at Photonics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW, UK.
authors.forename: E
authors.initials: E
authors.lastname: Grace
authors.affiliation: Institute of Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Ferrer
authors.affiliation: Laser Processing Group, Instituto de Optica (CSIC), Serrano 121, Madrid 28006, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Siegel
authors.affiliation: Department of Physics and Astronomy, University of Sussex, Sussex House, Falmer Brighton, BN1 9QH, UK.
authors.forename: A
authors.initials: A
authors.lastname: Pasquazi
authors.affiliation: NooEL-Nonlinear Optics and OptoElectronics Lab, CNISM and Department of Electronic Engineering - University "Roma Tre", Via della Vasca Navale 84, 00146 Rome, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Assanto
authors.affiliation: Laser Processing Group, Instituto de Optica (CSIC), Serrano 121, Madrid 28006, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Solis