Active Devices Based on Rare-Earth-doped Fluoroindate Fibers in Mid-Infrared Range

Rare-earth-doped fluoroindate fibers have emerged as promising materials for active photonic devices operating in the mid-infrared (Mid-IR) range, allowing low phonon energy and extended transmission from near infrared till 5.5 μm wavelength. These fibers enable efficient Mid-IR lasing and amplification by leveraging the spectroscopic properties of rare-earth ions such as Er³⁺, Dy³⁺, Pr³⁺ and Ho³⁺, which exhibit strong emission in this spectral region. Moreover, fluoroindate glasses can provide reduced multiphonon quenching, enhancing lasing efficiency. They can be employed to fabricate Mid-IR fiber lasers, optical amplifiers, to be integrated into sensing systems for environmental monitoring, biomedical diagnostics, and defense technologies. This paper explores the design approaches of fiber lasers and amplifiers, highlighting recent advancements, optimization strategies, and challenges in achieving high efficiency.