Thulium-doped passively mode-locked all polarization-maintaining fiber lasers

Abstract

This chapter discusses our findings in all-fiber mode-locked lasers emitting around 2 μm. Although these lasers were designed to serve different purposes, they share several characteristics, such as the use of an all-fiber polarization-maintaining cavity, the selection of a thulium-doped fiber as a medium gain, a semiconductor saturable absorber mirror as a mode locker, and, finally, resonant pumping in the C-telecommunication band. As a result, we were able to create first a low-repetition rate, all-polarization-maintaining, thulium-doped, passively mode-locked fiber laser running at 2.3 MHz. Next, we have examined the possibility of emission at a wavelength well beyond the maximum for the transition for thulium-doped fibers (1837 nm) for potential applications in spectroscopy. As a result, we have designed a passively mode-locked thulium-doped fiber laser emitting at 2070 nm, one of the longest wavelengths reported for solitonic emission using thulium-doped fibers. Finally, we present the first thulium-doped mode-locked fiber laser that maintains polarization and operates at the ultra-high fundamental repetition rate of 1 GHz in a laser cavity built entirely from commercially available components. The entire performance of these lasers is described, including a stability analysis.