Ytterbium (Yb) is a chemical element belonging to the group of rare earth metals. In laser technology, it has acquired a prominent role in the form of the trivalent ion Yb3+, which is used as a laser-active dopant in a variety of host materials, including crystals, glasses and ceramics, also often in active optical fibers. It is often used in various types of high-power lasers and for wavelength-tunable solid-state lasers.

Special Properties of Ytterbium-doped Gain Media
Ytterbium-doped laser crystals and glasses have a number of interesting properties, which differ from those of, e.g., neodymium-doped laser gain media:

Special Properties of Ytterbium-doped Gain Media

Ytterbium-doped laser crystals and glasses have a number of interesting properties, which differ from those of, e.g., neodymium-doped laser gain media:

They have a very simple electronic level structure, with only one excited state manifold within reach from the ground-state manifold with near-infrared or visible photons.

The quantum defect is always small, potentially allowing for very high power efficiencies of lasers and reducing thermal effects in high-power lasers.

The simple electronic structure excludes excited-state absorption and also a variety of detrimental quenching processes.

The gain bandwidth of the laser transitions is typically fairly large, compared with, e.g., neodymium-doped crystals. This allows for wide wavelength tuning ranges or for generating ultrashort pulses in mode-locked lasers.

The upper-state lifetimes are relatively long (typically of the order of 1–2 ms), which is beneficial for Q switching and for pulsed amplifiers. However, it also implies substantially lower transition cross sections than neodymium-doped gain media, for example, and that is detrimental in various cases.