Graphene-based 2 μm Tm 3+ -doped fiber passively Q-switched laser

The output characteristics of graphene-based passively Q-switched pulses at 2 μm wavelengths were reported. On the basis of linear resonant cavity, Tm3+-doped fiber and graphene saturable absorber mirror served as gain medium and passively Q-switched device respectively. Tm3+-doped fiber was end pumped by 792 nm semiconductor laser. Light in the cavity was focused onto graphene membrane through a set of collimation and focusing lens. Passively Q-switched pulses centered at 1 958 nm wavelength were acquired successfully. The minimum pulse width of 1.02 μs was obtained when pump power rise to 3.0 W, and corresponding average output power of 26 mW, repetition rate of 116 kHz, single pulse energy of 224 nJ were obtained respectively. Furthermore, average output power and pulse width presented approximate linear relationship with incident pump power. The experimental results indicate that excellent saturated absorption characteristic of graphene is effective for passively Q-switched pulse operation at 2 μm wavelengths.