Theoretical modeling of FM mode locking in Er,Ti:LiNbO3 waveguide lasers

A new theoretical model for actively mode-locked Er-doped LiNbO ₃ waveguide lasers has been developed starting from the semiclassical laser theory. Based on the coupled longitudinal mode equations, it enables one to calculate the proper oscillation frequency and the evolution of the amplitude and phase of each cavity mode. All of the main cavity features have been included in the model. The overlap between the dopant and optical field profiles in the waveguide, the longitudinal and transverse gain saturation and hole burning, the waveguide and material chromatic dispersion, and the wavelength-dependent absorption and emission cross sections were all taken into account. The distributed interaction with the externally driven integrated electrooptic phase modulator has been treated assuming lossy electrodes and nonideally matched line termination. Simulation results on the spectral width and pulse duration for fundamental mode locking at different RF modulation powers for an Er,Ti-LiNbO₃ laser emitting at 1.602 μm and pumped at 1.48 μm are also reported. The effect of the detuning between the modulator driving frequency and cavity free spectral range has been investigated in detail: the mode-locking regime quenching has also been studied. Significant differences from previous models are reported