Widely tunable 70-MHz near-infrared source of ultrashort pulses based on a mode-locked ytterbium laser and a photonic-crystal fiber

Abstract

Soliton self-frequency shift in a highly nonlinear photonic-crystal fiber is shown to enable an efficient wavelength conversion of 100-fs 70-MHz output of a solid-state ytterbium laser, allowing the generation of sub-100-fs laser pulses with a central wavelength tunable from 1060 to 1400 nm. In the single-soliton regime, laser pulses are efficiently converted into isolated wavelength-tunable bands, with a photon-number conversion efficiency of 82% achieved for ytterbium-laser pulses converted to a spectral band at 1125 nm supporting 35-fs transform-limited pulses. For high input powers, the ytterbium-laser pulses are coupled to multiple solitons inside the fiber, enabling efficient supercontinuum generation through involved soliton dynamics.