title: Interferometric analysis of reorientational nonlinear phenomena at 10.6 microm in a nematic liquid crystal.
abstract: We describe an infrared interferometric technique based on a two-dimensional spatial fringe analysis Fourier method for investigating the characteristic ring diffraction pattern generated by the self-phase-modulation effect induced in nematic liquid crystals (NLCs) by an infrared laser beam and for measuring the nonlinear refractive index of the NLCs. The experimental setup employs a Mach-Zehnder interferometer with a cw CO2 laser emitting at 10.6 microm and a pyroelectric optoelectronic sensor matrix to detect the modulated ring-pattern intensity distribution formed in the far field by a nematic E7 sample. A Fourier-transform-based analysis of the interference fringe pattern allows comparison of the measurements with the theoretical ring-pattern intensity distribution. We show that accurate determination of the nonlinear refractive index can be obtained by analyzing the two-dimensional phase distribution of the modulated ring pattern.
authors.affiliation: Istituto Nazionale di Ottica Applicata, Largo E. Fermi 6, 50125 Firenze, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Allaria
authors.forename: Stefano
authors.initials: S
authors.lastname: Brugioni
authors.forename: Sergio
authors.initials: S
authors.lastname: De Nicola
authors.forename: Pietro
authors.initials: P
authors.lastname: Ferraro
authors.forename: Simonetta
authors.initials: S
authors.lastname: Grilli
authors.forename: Riccardo
authors.initials: R
authors.lastname: Meucci