Nonlinear polarization evolution of ultrashort pulses in microstructure fiber
We present the experimental and numerical results for nonlinear polarization evolution of fs pulses during propgation in microstructure fiber. Numerical modelling shows that fiber dispersion enables a long interaction length between the components polarized along the two principal axes, thereby enhancing the effective nonlinear polarization evolution in microstructure fiber. c 2004 Optical Society of America OCIS codes: 320.7140, 060.7140 Ultrafast processes in fibers; 060.5530 Pulse
... 30 Pulse propagation and solitons Microstructured (MS) fiber is used for external broadening of nJ energy pulses from modelocked lasers to produce a spectral continuum. 1 The remarkable versatility of the generated continuum makes the applications of MS fibers widespread, ranging from optical coherence tomography 2 to optical frequency metrology. 3,4 As a result of the wide spread use, much effort is focused on understanding the complicated interplay between nonlinearity and propagation, and their affect on the properties of the generated continuum. 5,6 The conversion of amplitude to phase noise 7 and the generation of excess noise 8,9 during continuum generation impact both the optical frequency metrology and ultrafast communities, since the broadened fiber output is used for the input to nonlinear interferometers employed in carrierenvelope stabilization. 3,10 Although it is an experimental fact that the input polarization must be adjusted to obtain optimum continuum generation, 11 little effort has been put into understanding the polarization properties of the continuum, which has theoretically been shown to be complex. 12 In this Letter, we present measurements and theory of the nonlinear polarization evolution in MS fiber of ultrashort pulses from a modelocked Ti:sapphire (Ti:S) laser. The theory shows that dispersion actually enhances the effect of nonlinear evolution and is required to obtain qualitative agreement with experiment.