Abstract

Bandwidth limited pulses of <15 ps duration at a repetition rate of 11 GHz with an average power of 20 mW have been obtained by coupling a cw pumped fiber laser to a very short external cavity. In contrast to previous results we have used an external cavity containing no non-linear element, and no moving external mirror, cf. Fig. 1. The light of a 1W, cw diode laser is focused on a fiber possessing an annular active region. The Nd-doped silica fiber is 90 cm long. The main cavity (length l_m) is formed by the butt-coupled mirror facing the diode and the uncoated endface (reflectivity R=4%). The linear external resonator (length 1_e) is formed by the aforementioned fiber endface and a dichroic mirror. It is noteworthy that the fiber laser does not reach threshold without the dichroic mirror aligned.

© 1996 IEEE