Widely Tunable Gain-Switched Er³⁺-Doped ZrF₄ Fiber Laser From 3.4 to 3.7 μm

We present wide wavelength tuning of a gainswitched Er³⁺-doped ZrF₄ fiber laser in the 3.5 μm band for the first time to our knowledge. In this case, a dual-wavelength pumping (DWP) scheme is used including a continuous wave (CW) LD at 976 nm and two home-made Tm³⁺-doped fiber lasers (TDFLs) at 1981 nm operating in Q-switched and CW regimes, respectively. At the pump repetition rate of 50 kHz, stable gain-switched pulses can always be obtained within the whole tuning range of 3397.1~3690.2 nm (~293 nm) realized with a plane ruled grating. At a wavelength of 3450.5 nm, a maximum average power of 264.5 mW with a corresponding pulse energy of 5.29 μJ and width of 1.02 μs are achieved. The effects of pump power and laser wavelength on the output characteristics have also been investigated. The results indicate that such a gain-switched laser can be a versatile pulsed source for many applications.