Abstract
Mid-infrared (MIR) fiber pulsed lasers are of tremendous application interest in eye-safe LIDAR, spectroscopy, chemical detection and medicine. So far, these MIR lasers largely required bulk optical elements, complex free-space light alignment and large footprint, precluding compact all-fiber structure. Here, we proposed and demonstrated an all-fiberized structured gain-switched Ho<sup>3+</sup>-doped ZBLAN fiber laser operating around 2.9 μm. A home-made 1146 nm Raman fiber pulsed laser was utilized to pump highly concentrated single-cladding Ho<sup>3+</sup>-doped ZBLAN fiber with different lengths of 2 m or 0.25 m. A home-made MIR fiber mirror and a perpendicular-polished ZBLAN fiber end construct the all-fiberized MIR cavity. Stable gain-switched multiple states with a sub-pulse number tuned from 1 to 8 were observed. The effects of gain fiber length, pump power, pump repetition rate and output coupling ratio on performance of gain-switched pulses were further investigated in detail. The shortest pulse duration of 283 ns was attained with 10 kHz repetition rate. The pulsed laser, centered at 2.92 μm, had a maximum average output power of 54.2 mW and a slope efficiency of 10.12%. It is, to the best of our knowledge, the first time to demonstrate a mid-infrared gain-switched Ho<sup>3+</sup>:ZBLAN fiber laser with compact all-fiber structure.
Highlights
On account of abroad applications in remote sensing[1], scientific research, medical surgery[2] and electro-optical countermeasure[3], mid-infrared (MIR) lasers have attracted increased interest
Pulse evolution as pump power In our experiment, we studied the establishment of the output ~3 μm gain-switching pulses from the 2 m and 0.25 m long fibers with increasing pump power at 1146 nm
When the pump power continued to be increased, steady gain-switching pulse trains were obtained at the repetition rate of 20 kHz in accordance with pump
Summary
On account of abroad applications in remote sensing[1], scientific research, medical surgery[2] and electro-optical countermeasure[3], mid-infrared (MIR) lasers have attracted increased interest. The repetition rate of the 1.15 μm pump source was fixed at a value of 20 kHz. It should be pointed out that the pump pulse duration in this part of experiment vary from 35 μs to 45 μs, while the lifetime of the high energy level 5I6 in Ho3+-doped zirconium fluoride fiber measured as ~3.5 ms[33] is relatively long, so that stabilized gain-switch pulses can be generated.
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