Pulse repetition rate-switchable linearly polarized harmonic noise-like pulse at 2 μ m

A pulse repetition rate-switchable harmonic noise-like pulse (NLP) is demonstrated in an all-polarization-maintaining thulium-doped fiber laser. By enhancing both the intracavity linear and nonlinear phase shifts, an NLP up to the fourth harmonic is achieved. Benefiting from the all-polarization-maintaining configuration, the repetition rate of the NLP increases from 0.583 to 2.334 MHz simply by raising the pump power. The maximum powers of the NLP at different repetition rates are 4.4, 7.9, 10.8, and 15.3 mW, respectively. Using a single-stage all-polarization-maintaining amplifier, the average powers are further boosted to 3.1, 3.45, 3.67, and 3.74 W, with a pulse energy of 1.6 μJ for the 4th harmonic NLP. To the best of our knowledge, this is the first report of a high-energy, repetition rate-switchable NLP from an all-polarization-maintaining fiber laser system. Such a laser source could be applied in research on the spectral manipulation characteristics of supercontinuum and so on.