Sub-250 fs, 650 kW Peak Power Harmonic Mode-Locked Fiber Laser with InN-based SESAM

Abstract

Recent years have seen an increasing demand for ultrafast radiation sources, owing to their wide variety of applications. Fiber-based passively mode-locked sources relying on saturable absorbers are particularly interesting thanks to their simple implementation and relatively low cost, but they present some limitations especially in terms of achievable peak power (up to a few kW). Increasing the length of the resonator is a direct way to increase pulse energy, but this happens at the expense of the temporal width, which typically increases to the ns range. Here, we demonstrate ultrafast harmonically mode-locked fiber lasing in up to 6-km-long rings at 1.56 ¿m with InN SESAM. Fundamental mode-locking with pulse width of 239 fs, pulse energy of 155 nJ and peak power of 650 kW is achieved with a 1-km-long cavity. The system presented combines all the advantages of traditional ultrafast fiber lasers while overcoming its power limitation. Furthermore, by studying the dynamics of the system as a function of gain and cavity length, we demonstrate the possibility of generating multiple harmonics with high peak power and faster repetition rates