Passive Q-switching by Tm3+co-doping of a Yb3+-fiber laser

Q-switching of a wavelength tunable Yb3+-doped double-clad fiber laser by a Tm3+-codoping in the gain fiber is demonstrated. This system showed up to 2.4 W output power, up to 140 kHz repetition rate, a maximum pulse energy of 21.8 microJ and a minimum pulse duration of 1.1 micros. Using a grating pair in Littrow-Littman configuration the emission wavelength was tunable between 1055 nm and 1090 nm. The output radiation showed a maximum spectral linewidth of 4 GHz.