High pulse energy actively Q-switched dual-wavelength pumped Er:ZBLAN fiber laser at 3.5 µm

Abstract

In order to further improve the single pulse energy of actively Q-switched fiber laser in deep mid-infrared region, a universal and simple mechanical switch (MS) was used to achieve the high pulse energy 3.5 µm Er:ZBLAN fiber laser in dual-wavelength pumping (DWP) system. The maximum pulse energy was 9.4 µJ at the repetition rate of 8.4 kHz and the corresponding pulse width and peak power was 578 ns and 16.3 W, respectively. However, the further improvement of the pulse energy was limited by the formation of multiple pulses as the pump power increasing. According to the results of the experiment and numerical calculation, the multiple pulses were caused by relaxation oscillation and it was influenced by the pump power, the modulation rate and duty cycle of MS. Meanwhile, the Q-switched 2.8 µm laser was also found in the system, and it would also reduce the pulse energy of 3.5 µm laser. Therefore, the pulse energy could be improved in the further.