Negative frequency effects in nonlinear optics
Abstract
In this thesis we analyse the impact of the new terms that appear in the nonlinear polarisation
of the equations relevant to nonlinear x(3) optical materials when the slowly
varying envelope approximation (SVEA) is not applied. These new terms introduce
new nonlinear interactions between the positive and negative frequency parts of the
spectrum of an optical pulse, giving rise to novel nonlinear phenomena that were not
present in the usual models based in SVEA, like the ubiquitous nonlinear Schrodinger
equation (NLSE). The analysis carried out in this thesis is theoretical, with both
numerical simulations and analytical results presented. These results predict new frequency
generation processes that can have a considerable impact in ultrashort pulse
propagation and supercontinuum generation. We also discuss the experimental need
for this extended model, as well as some possible signatures of these novel frequency
generation processes in recent experiments.