Au nanocages saturable absorber for 3-µm mid-infrared pulsed fiber laser with a wide wavelength tuning range.

ABSTRACT

Au nanocages (Au-NCs) have attracted wide attention as low-dimensional materials with broadband absorption, ultrafast optical response, large third-order optical nonlinearity coefficient, and high photothermal stability and thermal tolerance. By employing Au-NCs as saturable absorbers, we demonstrate a widely tunable passively Q-switched erbium-doped fluoride fiber laser at the wavelength of 2.8 µm. When operates at 2778.0 nm, this laser delivers stable Q-switched pulses with a maximum average power of 584.6 mW at a pulse repetition rate of 80.6 kHz. The minimum pulse duration attained was 1.16 µs corresponding with the single pulse energy of 7.25 µJ. Our results present onefold increase in pulse energy over previously published values achieved from Au nanoparticles based 3-µm passively Q-switched fiber lasers. By introducing a plane ruled grating, a tuning rage of 57.0 nm from 2753.0 to 2810.0 nm is achieved, while maintaining stable Q-switched operation. To our knowledge, this is the first time to demonstrate that Au-NCs can realize mid-infrared pulsed laser. Our research results show that Au-NCs are promising broadband nonlinear modulators for mid-infrared pulse generation.