High peak power pulsed single-mode linearly polarized LMA fiber amplifier and Q-switch laser

We report on the recent progress in the design and development of completely monolithic linearly-polarized pulsed fiber amplifiers seeded by Q-switched fiber laser oscillators. We demonstrate near diffraction limited beam quality with ~20kW peak power (1mJ pulse energy, ~45nsec) pulses and an average power ~20W at 20kHz repetition rate with linearly polarized (>17dB PER) output from a simple MOPA design. The laser produces spectrally narrow pulses with ~0.5nm linewidth centered at 1064nm, suitable for various non-linear applications including generation of visible and UV light. The simple MOPA design consists of a monolithic fiber amplifier based on an optimized coil of polarization maintaining large mode area (PM-LMA) fiber with 30μm-core and low power Q-switched fiber oscillator. Excellent output beam quality is achieved through the mode selectivity of the coiled PM-LMA fiber in the amplifier stage. Such compact and robust fiber lasers are suitable for a variety of applications, such as nonlinear wavelength conversion processes using a variety of nonlinear materials, laser radars, etc.