Passively Q-switching an all polarization-maintaining erbium-doped fiber laser with a rhenium disulfide (ReS2) saturable absorber

This study demonstrates a linearly polarized Er-doped fiber laser system featuring an all-polarization-maintaining (all-PM) architecture. Short pulses were generated by Q-switching operation based on drop-casting rhenium disulfide (ReS2) saturable absorber (SA) onto a fiber connector placed inside the laser cavity. The Q-switching operation of the laser was able to self-start at a low (23 mW) threshold power of the pump and without the need to use a polarization controller. The proposed laser was able to produce stable pulses with a center wavelength and 3-dB bandwidth of 1558.4 nm and 0.13 nm, respectively. The shortest pulse duration measured (2.8 μs) was achieved at a repetition rate of 37.6 kHz while the highest average output power and pulse energy were 2.2 mW and 76.5 nJ, respectively. Furthermore, as the cavity of the laser was designed to be all-PM the laser that it produced was linearly polarized and had a degree of polarization (DOP) at the level of 94.5 % and 40 dB polarization extinction ratio (PER). Therefore, the proposed laser is a suitable light source for optical applications in environments that are complex.