Ni-NPs doped PVA: An efficient saturable absorber for generation multiwavelength Q-switched fiber laser system near 1.5 μm

We report on the use of Nickel nanoparticles (Ni-NPs) as saturable absorber (SA) to generate Q-switched fiber laser pulses in C-band. The Ni-NPs were incorporated in polyvinyl alcohol (PVA) to produce thin film-based saturable absorber (SA) and integrated into an erbium-doped fiber laser (EDFL) ring cavity to generate passively Q-switching. The Ni-doped PVA SA reveals modulation depth of 15% and a saturation intensity of 200 MW/cm(2). Lasing in CW region begins at 77 mW pump power, whereas stable self-starting Q-switching with a central wavelength of 1563.1 nm begins at 85 mW. By fine adjustment of the laser diode pump power up to 236.4 mW dual-, and triple- lasing lines have been observed at 1563.1, 1563.3 and 1563.4 with side mode suppression ratio (SMSR) of more than 49 dB. The proposed laser is useful for generating pulse laser with a minimum pulse width of 1.5 mu s and a maximum repetition rate of 56.79 kHz with a pulse energy of about 4.33 nJ at the maximum pump power of 275 mW. The stability of the pulse is verified from the radio-frequency (RF) spectrum with a measured signal-to-noise ratio (SNR) of 44 dB. The ability of Ni-PVA as an effective SA may lead to further development of pulsed fiber laser in the field of photonics.