Self- and cross-phase modulation effects on the nonlinear propagation of ultrashort pulses in optical fibers

The thesis describes the effects of self- and cross-phase modulation on the propagation of ultrashort pulses in optical fibers.;In the first part of the thesis, we review the theory of self-phase modulation and studies the generation and compression of femtosecond supercontinua using single-mode optical fibers and high-refractive index prisms.;In the second part of the thesis, we investigate theoretically and experimentally spectral and temporal effects of cross-phase modulation on the propagation of interacting ultrashort pulses in optical fibers. In addition, we study XPM and SPM effects on the generation processes of picosecond stimulated Raman pulses and stimulated four photon mixing pulses. All these effects are important for their potential applications for the generation and control of terahertz pulses.;In the third part of the thesis, we report on the generation of ultrashort pulses with terahertz repetition rates. In an experiment using short lengths of a single-mode optical fibers, we have for the first time generated modulation instability pulses in the normal dispersion regime of optical fibers. In an other experiment we have generated up to 15 terahertz repetition rate pulses by modulation instability oscillations in a femtosecond dye laser.;In the fourth part of the thesis, we study spatial effects on the nonlinear propagation of picosecond pulses in multimode optical fibers. We demonstrate the self-focusing and single-mode propagation of Raman pulses in a fiber able to sustain more than 100,000 modes. In addition, we have developed a new theory for the nonlinear propagation of ultrashort pulses in graded-index waveguides. Our theory predicts new results such as a reverse of the frequency-chirp sign, i.e. sign of the self-phase modulation, due to diffraction effects inside the waveguide. A major consequence of this theoretical prediction is the possibility to propagate solitons and to compress pulses in the normal dispersion regime of optical fibers.;In the fifth part of the thesis, we give some insights to future works that could investigate applications of XPM for the generation and control of ultrashort pulses with teraherz repetition rates.;The final section highlights the problems that need to be addressed which are the outgrowth of my research.