Over 200 mW gain-switched Er-doped ZBALN fiber laser at 3750 nm

We demonstrate a pulsed Er-doped ZBLAN fiber laser at 3750 nm based on the gain-switching scheme. A diffraction grating was introduced as a wavelength selection component to enable stable lasing in this long-wavelength region, which has deviated from the emission peak of F-4(9/2)-> I-4(9/2) transition in Er3+. Different from the convention gain-switching behavior where the pulse repetition frequency (PRF) of output laser is same as the that of the pump, three switchable gain-switched temporal states with 1/n (n=4,3,2) pump PRF rates are observed in experiment. The pulse evolution, including average output power, PRF, pulse duration, and peak power, in response to the 1950 nm pump power are investigated in detail. Over 200 mW average output power at 3750 nm was obtained under 12 W of 1950 nm pump power. The pulse repetition frequency, pulse energy and pulse duration were 35.4 kHz, 6.7 mu J and 1.2 mu s, respectively. This work represents the longest pulsed emission wavelength generated from rare-earth doped fiber lasers.