Nonlinear Optics in Guided Geometries - Abstract
Fallnich, Carsten
Meanwhile the use of mode-locked ultra-short light pulses and microstructured fibers is a common procedure to generate broadband supercontinua for precision frequency metrology, ultrafast spectroscopy or coherence tomography. Octave-spanning supercontinua can be generated reliably as high intensities are easily achieved inside the small fiber core diameter and as soliton formation is accomplished by dispersion management related to the specific Bragg cladding structure. But the generation of all these new optical frequency components is depending on a mixture of nonlinear effects, like self-phase modulation, self-steepening, four-wave mixing, and Raman scattering.
Therefore, the stability in amplitude and phase of the supercontinuum -- meaning the coherence from pulse to pulse -- can be substantially reduced. In order to counteract, the driving pump pulses of the supercontinuum generation have to be controlled in amplitude and phase below certain limits depending on the needed measurement accuracy.
In contrast to further improving only the stability of the laser system, we investigated the nonlinear dynamics of femtosecond supercontinuum generation with feedback and, hence, a synchronously pumped white-light oscillator is set-up. We observed that such a supercontinuum oscillator is able to show different nonlinear dynamics like period multiplication, limit cycles as well as chaotic behaviour. By exploring these regimes in more detail we are gathering for optimum parameters that probably a self-stabilization of the supercontinuum generator can be observed, meaning a self-synchronization of several ten thousands of longitudinal modes within the broad supercontinuum spectrum.
The talk will present numerical simulation results based on the generalized nonlinear Schrödinger equation and first experimental verifications of the above mentioned nonlinear dynamics in synchronously-pumped supercontinuum generation using a polarization-maintaining microstructured fiber driven with mode-locked femtosecond pulses from a Titanium-Sapphire laser.