Dynamic pulse buildup in continuous-wave passively mode-locked picosecond Ti: Sapphire/DDI and Ti: Sapphire/IR140 lasers

Abstract

We have studied both theoretically and experimentally the buildup of mode-locked pulses out of noise in continuous wave (cw) passively mode-locked Ti: sapphire lasers with DDI and IR140 dye saturable absorbers, which have significantly different optical properties. The evolution of the laser output from cw, to partial mode-locking, to complete mode-locking was investigated experimentally by measuring the contrast ratio of transient autocorrelation trace, the second-harmonic-generation (SHG) conversion efficiency, the fractional energy, optical and radio frequency (RF) spectra at consecutive delay times using the time-gating technique. Theoretically, we have simulated the pulse buildup numerically by adopting the two-level model for the saturable absorber. The experimental results are in good agreement with the predictions of numerical simulation.