Abstract

Mode-locked ytterbium-fiber lasers typically require external grating compressors for positive chirp removal to achieve pulse durations below 200 fs [1]. Compression and delivery of the pulses using photonic band-gap fiber producing anomalous dispersion are, however, problematic because of its high third-order dispersion. Here we demonstrate a laser, shown in Fig. 1 that delivers sub-100 fs chirp-free pulses directly at the fiber output. The cavity is optimized to supply both large optical spectrum and negative chirp at the input of the output fiber lead. The laser gain medium is 16-cm highly doped ytterbium-doped fiber. The ytterbium-doped fiber is pumped with via a dichroic fiber coupler by a 980 mil laser diode delivering up to 300 mW (not shown in the figure). Dispersion compensation is provided by a pair of 1250- lines/mm transmission gratings with separation of 4 nun, generation a dispersion of ≈-0.02 ps². Self-starting mode- locked operation was initiated through the use of a semiconductor saturable absorber mirror ( SESAM).

© 2007 IEEE