Bifurcation Analysis in High Repetition Rate Regenerative Amplifiers

A theoretical and experimental study of the nonlinear dynamics is presented for regenerative amplifiers (RAs), operating at repetition rates in the vicinity of the inverse upper state lifetime of the active medium. In the first part, a comprehensive model for continuously pumped high repetition rate RAs is established. In the second part, we analyze their nonlinear dynamics to explain and review methods of bifurcation control. Our model can be applied for quasithree as well as four-level laser systems. It is characterized by a high computation speed and a high accuracy, regarding energy, and spectrum of the simulated pulses. We use a state-space representation of the temporal inversion fraction evolution in the gain medium to describe the RA dynamics. A comprehensive physical picture of bifurcation dynamics in RAs and its influencing parameters is developed. The results are general and can be applied to control bifurcation in any kind of high repetition RA. This knowledge enabled the experimental realization of a Ho:YLF RA operating at 2.05 μm, which delivers more than 10 mJ picosecond pulses at kilohertz repetition rate with outstanding stability.