Holmium-doped fluoride glass fiber can be used to create
efficient, high-power fiber lasers operating in the 3μm region.
Fiber lasers produce a high-power high-quality optical beam
and have led to many major advances in optics and photonics, including fiber
laser-based frequency combs,1 laser eye surgery,2 and industrial machining.3The
vast majority of these laser systems have been based on doping rare-earth ions
into silica glass fiber, the fabrication and performance of which has reached a
level of maturity rarely found in optics. This has enabled the construction of
robust, high-performance fiber laser systems operating in the near-IR. However,
silica fibers are only transparent at wavelengths shorter than 2μm, and many
important molecules have strong fundamental rotational-vibrational transitions
in the mid-IR range (3–5μm).4As a result, lasers based on silica fibers have
not seen extensive use in applications such as trace gas detection, ablation of
water-based tissues (e.g., human skin), and sensitive spectroscopy. Extending
the wavelength range of fiber lasers to this region is desirable as the
advantages of fiber lasers could open up new applications.