title: Measurement of nonlinear refractive index and ionization rates in air using a wavefront sensor.
abstract: A wavefront sensor has been used to measure the Kerr nonlinear focal shift of a high intensity ultrashort pulse beam in a focusing beam geometry while accounting for the effects of plasma-defocusing. It is shown that plasma-defocusing plays a major role in the nonlinear focusing dynamics and that measurements of Kerr nonlinearity and ionization are coupled. Furthermore, this coupled effect leads to a novel way that measures the laser ionization rates in air under atmospheric conditions as well as Kerr nonlinearity. The measured nonlinear index n₂ compares well with values found in the literature and the measured ionization rates could be successfully benchmarked to the model developed by Perelomov, Popov, and Terentev (PPT model) [Sov. Phys. JETP 50, 1393 (1966)].
authors.affiliation: Sandia National Laboratories, Albuquerque, New Mexico 87123, USA. jschwar@sandia.gov
authors.forename: Jens
authors.initials: J
authors.lastname: Schwarz
authors.forename: Patrick
authors.initials: P
authors.lastname: Rambo
authors.forename: Mark
authors.initials: M
authors.lastname: Kimmel
authors.forename: Briggs
authors.initials: B
authors.lastname: Atherton