Sub-10 picosecond pulses from a fiber-amplified and optically compressed passively Q-switched microchip laser

Abstract

We report on nonlinear optical compression of passively Q-switched pulses accessing sub-10 ps domain, which is so far dominated by mode-locked systems. The concept implements the SPM-induced spectral-broadening of passively Q-switched microchip pulses in optical waveguides and a supplementary compression with bulk optics e.g. a pair of diffraction gratings or a chirped-Bragg-grating. Used seed-source is a fiber-amplified, passively Q-switched microchip laser operating on a single longitudinal mode and consists of a monolithically bonded combination of Nd:YVO₄-crystal and semiconductor saturable absorber mirror. The microchip laser provides pulses with durations of 100-150 ps, pulse energies of ~200 nJ at various repetition rates from hundreds of kilohertz to more than a megahertz, and line width of ~20 pm at wavelength of 1064nm. During the amplification process in the photonics crystal fiber, the pulses are spectrally broadened to up to ~0.7nm at energy of 17μJ. Using a diffraction grating compressor with 1740 l/mm, the pulses are compressed to duration as short as 6ps assuming a numerically calculated de-convolution factor of 0.735. To the best of our knowledge, this is the first reported realization of nonlinear compression of the Q-switched pulses and the shortest pulses from a passively Q-switched laser system.