Nickel oxide (NiO) nanoparticles were synthesized by a facile sonochemical method to fabricate saturable absorber (SA) composite film with a modulation depth of 39% and saturation intensity of 0.025 MW cm −2 . By inserting the NiO SA into a laser cavity, a stable Q-switched operation is achieved at 1561.2 nm. The laser has a pump threshold of 25 mW, a pulse repetition rate tunable from 19.57 to 52.18 kHz, a high signal-to-noise ratio of 55 dB and a minimum pulse duration of 5.2 µs. Such results imply that NiO nanoparticles are a comparable candidate for an SA in passively Q-switched fiber lasers at a low pump intensity. To the best of our knowledge, this is the first demonstration of a fiber laser based on NiO SA.
We experimentally demonstrate a passive mode-locked erbium-doped fiber laser (EDFL) using a multi-layer black phosphorus saturable absorber (BPSA). The BPSA is fabricated by mechanically exfoliating a BP crystal and sticking the acquired BP flakes onto scotch tape. A small piece of the tape is then placed between two ferrules and integrated into an EDFL cavity to achieve a self-started soliton mode-locked pulse operation at 1560.7 nm wavelength. The 3 dB bandwidth, pulse width, and repetition rate of the laser are 6.4 nm, 570 fs, and 6.88 MHz, respectively. The average output power is 5.1 mW at pump power of 140 mW and thus, the pulse energy and peak power are estimated at 0.74 nJ and 1.22 kW, respectively. The BPSA was constructed in a simple fabrication process and has a modulation depth of 7% to successfully produce the stable mode-locked fiber laser.
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