Extractable energy from ytterbium-doped high-energy pulsed fiber amplifiers and lasers

An analytic model is developed to evaluate the extractable energy from high-energy pulsed ytterbium-doped fiber amplifiers and lasers. The energy extraction capabilities under the limitation of spurious lasing, due to amplified spontaneous emission, are mapped for various numerical apertures, single- and multitransverse-mode evolution, and operating wavelengths. The calculation results of the analytic model show a good match with experimental results carried out for various double-clad fiber amplifiers. The model provides an accurate assessment for the maximum pulse energy that can be extracted from a given ytterbium-doped fiber. In addition, for a specific pump power, the model can be used to determine the minimum repetition rate and optimal length, under which the laser source can be operated before spurious lasing occurs.