Room temperature fiber laser at 3.92 {\mu}m

TL;DR

This paper reports the development of a novel holmium-doped fluoroindate fiber laser operating at 3.92 μm at room temperature, extending the wavelength coverage of fiber lasers into the mid-infrared region.

Contribution

Introduction of a heavily holmium-doped fluoroindate fiber enabling room temperature laser emission at 3.92 μm, surpassing previous wavelength limitations of fiber lasers.

Findings

Achieved 200 mW output power at 3.92 μm.

Extended transparency of fiber up to 5 μm.

Demonstrated potential for lasers emitting beyond 4 μm.

Abstract

Rare-earth-doped fiber lasers are promising contenders in the development of spectroscopy, free-space communications and countermeasure applications in the 3 - 5 {\mu}m 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 {\mu}m, 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 {\mu}m, to demonstrate the longest wavelength room temperature fiber laser at 3.92 {\mu}m. Achieving $\approx$ 200 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 {\mu}m.