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A cascaded ytterbium-doped all-fiber master oscillator power amplifier (MOPA) with 1064-nm pulsed laser is demonstrated, and it can produce up to 20-W average power and 0.1-mJ pulse energy at tunable repetition rates from 10 to 200 kHz. Two main di±culties of the all-fiber configuration are overcome: all fiber isolator and mode field adapter between single mode fiber (SMF) and double cladding fiber (DCF). Gain saturation and nonlinear effect are analyzed theoretically, and the possibility of further power-scaling of this cascade scheme is predicted.

We report on hundred watts range ytterbium-doped all-fiber laser assembly based on the master oscillator power amplifier structure. It consisted of an oscillator and an amplifier with all-fiber components. And fiber fusion splice made the laser be an integrated fiber system. It generated up to 175.5 W of continuous-wave (CW) output power at 1085 nm with more than 75% extraction efficiency in the amplifier when the total coupled pump power into the double clad fiber was 270 W.

The fusion splicing of double-clad (DC) specialty fibers based on active alignment is crucial to the investigation of high-power monolithic fiber lasers. Given the wave-guiding characteristic of DC fiber, a light stripper is introduced in an active alignment experiment. We propose a novel method for stripping light that is convenient, highly efficient, and low cost. This method is also effective for low-numerical-aperture beams that escape from the fiber core. A splice loss as low as 0.05 dB is achieved.