Double-rod gold metasurface for Q-switched polarization-maintaining fiber laser

Optical metasurfaces, i.e., consisting of subwavelength meta-atoms, have emerged as a versatile platform for shaping light in both linear and nonlinear regimes. However, rare researches have focused on their saturable absorption properties and corresponding applications. Here we report a Q-switched polarization-maintaining fiber laser working at 1 μm based on double-rod gold metasurface as an SA. The periodic double-nanorod gold metasurface can provide a strong field enhancement by introducing Fano resonance and surface lattice resonance simultaneously, which is of benefit to significant nonlinear effects. Experimental results successfully confirm that the proposed gold metasurface can be implemented as a saturable absorber in a polarization-maintaining fiber laser for Q-switching operation. Typically, the passively Q-switched fiber laser could give output pulses at 1031.4 nm with a repetition rate of 34.1 kHz and a pulse width of 2.12 μs when pumped by a 976 nm laser diode of 155 mW. The repetition rate increases from 21.82 kHz to 35.76 kHz and the pulse width decreases from 3.38 μs to 1.92 μs when the pump power ranges from 105 mW to 160 mW.