Passively Q-switched TM3+-doped silica fiber lasers

By splicing on a length of Ho3+-doped silica fiber onto a diode-pumped double-clad Tm3+-doped silica fiber, stable passive Q switching of the Tm3+-doped silica fiber laser is demonstrated. The formation of Q-switched pulses was found to depend on both the length and the position of the Ho3+-doped silica fiber that was inserted into the fiber laser cavity. For stable Q-switched pulse generation, Ho3+-doped silica fiber lengths shorter than twice the absorption depth must be used. For long Ho3+-doped silica fiber lengths, randomly generated pulses are observed at operating wavelengths longer than 2090 nm, which are attributed to intracavity pumping of the Ho3+-doped silica fiber. (c) 2007 Optical Society of America.