O-band femtosecond mode-locked laser by using Ni-MOF in praseodymium-doped fluoride fiber

This work reports an ultrafast mode-locked fiber laser at the less investigated region of the O-band using a nickel metal-organic framework (Ni-MOF), which works as a saturable absorber (SA). Ni-MOF was prepared using the high-power laser-induced method. A stable mode-locked laser of 450 fs pulse duration was obtained. The repetition rate and signal-to-noise ratio (SNR) were 0.408 MHz and 52.5 dB, while the lasers operate at a wavelength of 1298.1 nm. At the pump power of 88 mW, the mode-locked laser was characterized to have an average output power of 0.69 mW, corresponding to a pulse energy of 1.69 nJ and a pulse peak power of 3.53 kW. Additionally, harmonic mode-locked laser operation was also achieved above the pump power of 88 mW. With the harmonic mode-locked laser operation, the pulse repetition rate increased to 2.45 MHz when the pump power was 125.7 mW. To the author's knowledge, this is the first report of novel MOF material used as an SA in praseodymium-doped fluoride fiber (PDFF) laser. •Generation of mode-locked pulses using nickel metal-organic framework (Ni-MOF).•The femtosecond mode-locked laser had a center wavelength of 1298.1 nm.•The fundamental mode-locked pulses had a frequency of 0.408 MHz.•The highest stable harmonics frequency was 2.45 MHz, observed at the 6th harmonics.•A short pulse width of 450 fs was obtained for the fundamental pulse.