Dual wavelength Q-switched cascade laser

A diode-cladding-pumped dual wavelength Q-switched Ho3+-doped fluoride cascade fiber laser operating in the mid-infrared is demonstrated. Stable pulse trains from the I-5(6) -> I-5(7) and I-5(7) -> I-5(8) laser transitions were produced, and the mu s-level time delay between the pulses from each transition was dependent on the pump power. At maximum pump power and at an acousto-optic modulator repetition rate of 25 kHz, the I-5(6) -> I-5(7) transition pulse operated at 3.005 mu m, a pulse energy of 29 mu J, and a pulse width of 380 ns; the I-5(7) -> I-5(8) transition pulse correspondingly produced 7 mu J pulse energy and 260 ns pulse width at 2.074 mu m. To the best of our knowledge, this is the first demonstration of a Q-switched fiber laser operating beyond 3 mu m. (C) 2012 Optical Society of America