A fiber-based source for high-energy picosecond and nanosecond pulses is described. By minimizing nonlinear energy limitations in fiber amplifiers, pulse energies close to the damage threshold of optical fibers can be generated. The implementation of optimized seed sources in conjunction with amplifier chains comprising at least one nonlinear fiber amplifier allows for the generation of near bandwidth-limited high-energy picosecond pulses. Optimized seed sources for high-energy pulsed fiber amplifiers comprise semiconductor lasers as well as stretched mode locked fiber lasers. The maximization of the pulse energies obtainable from fiber amplifiers further allows for the generation of high-energy ultraviolet and IR pulses at high repetition rates.