Investigations of a 1018 nm gain-switched Yb-doped fiber oscillator.

In this paper, we investigate a 1018 nm gain-switched ytterbium-doped fiber oscillator at a low repetition rate in terms of theory and experiment. Theoretically, a numerical model applicable to a 1018 nm gain-switched ytterbium-doped fiber laser was established. The influence of the pump peak power and active fiber lengths on the 1018 nm gain-switched ytterbium-doped fiber laser was numerically simulated. Experimentally, a compact 1018 nm all-fiber-structured pulsed laser oscillator is constructed, in which a pulse width of 110 ns and a single-pulse energy of 0.1 mJ were obtained. Moreover, the experimental results are in agreement with the numerical simulation ones. To the best of our knowledge, this is the first time that gain-switching technology has been applied to 1018 nm fiber lasers to generate nanosecond pulsed lasers. The model and experimental results can provide a reference for the engineering design of the same type of low repetition rate fiber lasers below the kilohertz level.

All-fiber hectowatt radially polarized laser system.

A high-power all-fiber radially polarized laser system is demonstrated, in which an integrated nanograting mode convertor (S-wave plate) is used for the generation of radially polarized beam. Experimentally, a 1-W radially polarized beam was used as the seed laser, whose mode purity and mode extinction ratio (MER) were 96.5% and 98.3%, respectively. A single-stage few-mode fiber amplifier was employed to boost the 1-W seed laser to an average power of 113.2 W, when the pump power was 160 W. The corresponding slope efficiency and beam quality factor (M2) were approximately 72% and 2.3%, respectively. Moreover, the mode purity and MER of the amplified radially polarized laser were measured to be 95.7% and 97%, respectively. To the best of our knowledge, this is the highest output power from an all-fiber radially polarized laser system without obvious degradations of the mode purity and MER.