Octave-spanning supercontinuum generated in SF6-glass PCF by a 1060 nm mode-locked fibre laser delivering 20 pJ per pulse

We report the generation of an octave-spanning supercontinuum in SF6-glass photonic crystal fiber using a diode-pumped passively modelocked fs Yb-fiber laser oscillating at 1060 nm. The pulses (energy up to 500 pJ and duration 60 fs) were launched into a 4 cm length of PCF (core diameter 1.7 mu m and zero-dispersion wavelength similar to 1060 nm). Less than 20 pJ of launched pulse energy was sufficient to generate a supercontinuum from 600 nm to 1450 nm, which represents the lowest energy so far reported for generation of an octave-spanning supercontinuum from a 1 mu m pump. Since the laser pulse energy scales inversely with the repetition rate, highly compact and efficient sources based on SF6-glass PCF are likely to be especially useful for efficient spectral broadening at high repetition rates (several GHz), such as those needed for the precise calibration of astronomical spectrographs, where a frequency comb spacing > 10 GHz is required for the best performance. (C) 2009 Optical Society of America