Multi-Millijoule Nanosecond Fiber Amplifier at 2.8 μm

High-energy, short-pulse laser sources operating near water absorption peak <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(2.94 \mu \mathrm{m})$</tex> has crucial importance for many applications especially in biomedicine. This significance comes from high water content of biomedical tissues which allows such lasers to take full advantage of the strong water absorption near this wavelength. The use of high-energy pulses near this peak enhances ablation efficiency, enables penetration into dense or hard materials such as bone and calcified tissues and facilitates faster, cleaner process by minimizing residue and debris. The ideal duration of pulses for minimizing thermal effects in biomaterials needs to be shorter than the thermal relaxation time <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(10 \mu \mathrm{s})$</tex> and comparable to or shorter than the thermoelastic stress propagation time, which is around 1 ns [1], [2]. The laser operation at this short pulse duration and near water absorption peak is output energy limited to sub-mJ level and one of the ideal approaches is to use fluoride fiber amplifiers to boost the limited energy of such systems to multi-millijoule levels.