| Abstract [eng] |
Photonic crystal fibers (PCFs) open up new opportunities for the study of nonlinear phenomena, thanks to the ability to control their waveguiding properties – such as dispersion, nonlinearity, birefringence, and single-mode operation – during the manufacturing process. In this doctoral dissertation, the dynamics of coherent nonlinear phenomena occurring in PCFs are investigated and new methods are presented for characterizing the fiber’s nonlinear properties and the behavior of ultrashort optical pulses. In this dissertation supercontinuum generation in a highly nonlinear polarization-maintaining PCF is first discussed, where controlled bursts of two orthogonally polarized femtosecond pulses are used for pumping. Then, an investigation of UV-VIS light generation in a short PCF is presented. To better understand the nonlinear phenomena occurring in PCFs, it is important to have reliable methods for characterizing both the nonlinear medium and the pulses propagating through it. Therefore, this dissertation presents a new method for measuring the nonlinear refractive index of a polarization-maintaining PCF, based on measurements of the polarization state variation of the light exiting the fiber as the average power of the pump pulses is varied: the first method for determining the nonlinear refractive index of an already manufactured PCF. Finally, a non-iterative semi-analytical algorithm is presented, which enables reliable reconstruction of the intensity profile and phase of the investigated pulse from cross-correlation frequency-resolved optical gating (XFROG) measurements. |
