High-power wavelength-tunable photonic-crystal-fiber-based oscillator-amplifier-frequency-shifter femtosecond laser system and its applications for material microprocessing

A high-power wavelength-tunable femtosecond fiber laser source is developed based on photonic-crystal fiber technology. Laser oscillator and amplifier stages in this system employ diode-pumped ytterbium-doped single-polarization large-mode-area photonic-crystal fibers in a stretcher-free configuration, delivering laser pulses with an average power of 10.4 W, a pulse width of 52 fs, and a peak power of 4 MW at a repetition rate of 50 MHz after pulse compression. Nonlinear transformation of such laser pulses in a highly nonlinear photonic-crystal fiber yields light pulses smoothly tunable within the range of wavelengths from 1.0 to 1.4 μm and allows the generation of supercontinuum stretching from 450 to at least 1750 nm. We report experiments on silicon microprocessing and chromium nanofilm patterning at a high repetition rate, demonstrating the potential of the developed fiber-laser source for fast micromachining, microfabrication, and microprocessing.