Q-switched and Mode-Locked pulse generation in fiber laser with micro particles polyacrylonitrile absorber

This paper investigates the use of polyacrylonitrile (PAN) absorber in an erbium-doped fiber laser (EDFL) for generating Q-switched and mode-locked pulses. PAN absorber was prepared by dispersing its micro-particles onto scotch tape, which was then added into the EDFL cavity. This absorber successfully enabled cavity loss modulation, with stable Q-switched operation achieved at a pump power threshold of 61.1 mW. The repetition frequency rose from 33.39 kHz to 45.35 kHz, and pulse width reduced from 8.55 μs to 6.42 μs as pump power rose from 61.1 mW to 155.0 mW. The Q-switched EDFL, operating at a central wavelength of 1560 nm, achieved the highest pulse energy of 240.4 nJ and a slope efficiency of 7.61 %. By adding 100 m of single-mode fiber (SMF) to the ring cavity, self-starting mode-locked operation was initiated, with stable pulses observed between 123.7 and 254.13 mW pump power. The laser operated at a central wavelength of 1566 nm, with a repetition rate of 1.8 MHz and a pulse width of 4.40 ps. These results demonstrate that polyacrylonitrile is an effective absorber for pulse generation in fiber lasers.