title: Nonlinear coupling between axisymmetrically-polarized ultrashort optical pulses in a uniaxial crystal.
abstract: Nonlinear propagation of focused axisymmetrically-polarized ultrashort optical pulses along the optic axis in a uniaxial crystal is investigated experimentally and theoretically. The energy transfer between an azimuthally-polarized pulse and a radially-polarized pulse is observed. To analyze the nonlinear propagation, a general paraxial equation with a third-order nonlinearity for axisymmetrically-polarized pulses in a uniaxial crystal is derived and the extended Stokes parameters (ESPs) based on cylindrical coordinates are newly-introduced. The simulation results by using this equation, providing the calculated ESPs, well explain our experimental observations: 1) the energy transfer is attributed to the four-wave-mixing effect, reflecting the overlapping between the axisymmetrically polarized modes, 2) the variations of the polarization defined from the ESPs are clarified to be affected by the self- and the cross-phase modulations, which make the effective propagation length long or short.
authors.forename: Masato
authors.initials: M
authors.lastname: Suzuki
authors.forename: Keisaku
authors.initials: K
authors.lastname: Yamane
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Oka
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Toda
authors.forename: Ryuji
authors.initials: R
authors.lastname: Morita