Rare-earth-doped fiber lasers are promising contenders in the development of spectroscopy, free-space communications, and countermeasure applications in the 3–5 μm spectral region. However, given the limited transparency of the commonly used fluorozirconate glass fiber, these systems have only achieved wavelength coverage up to 3.8 μm, hence fueling the development of more suitable fiber glass compositions. To this extent, we propose in this Letter a novel heavily holmium-doped fluoroindate fiber, providing extended transparency up to 5 μm, to demonstrate the longest wavelength room-temperature fiber laser at 3.92 μm. Achieving $\sim 200\mathrm{mW}$ of output power when cladding pumped by a commercial 888 nm laser diode, this demonstration paves the way for powerful mid-infrared fiber lasers emitting at and beyond 4 μm.

中文翻译：

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室温光纤激光器3.92μm

掺杂稀土的光纤激光器是光谱技术，自由空间通信以及在3–5μm光谱区域中对策应用的发展中有希望的竞争者。但是，鉴于常用的氟锆酸盐玻璃纤维的透明性有限，这些系统仅实现了高达3.8μm的波长覆盖，因此为开发更合适的玻璃纤维组合物提供了动力。在这个程度上，我们在这封信中提出了一种新型的重度掺-氟代碳酸盐光纤，该光纤可提供高达5μm的扩展透明性，以证明波长最长的室温光纤激光器为3.92μm。实现目标$〜200\mathrm{兆瓦}$ 当通过商用888 nm激光二极管泵浦包层时，输出功率达到5％，该演示为发射4μm及以上波长的强大中红外光纤激光器铺平了道路。