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 mu s to 6.42 mu s 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.