Er-doped crystalline active media for ~ 3 μm diode-pumped lasers

Lasers based on erbium ions using ⁴I_11/2 ​→ ​⁴I_13/2 transition can generate laser radiation in the spectral range from 2.7 ​μm to 3 ​μm. Since the strong absorption peak of water is located at 3 ​μm, there has been an effort to develop a suitable laser source for various medical applications, e.g. dentistry, dermatology, urology, or surgery. Laser radiation from this wavelength range can also be used in spectroscopy, as a pumping source for optical parametric oscillators, or for further mid-infrared conversion.

This paper represents an overview of the erbium-doped active media (e.g. Er:YAG, Er:YAP, Er:GGG, Er:SrF₂, Er:YLF, Er:Y₂O₃, Er:KYW, etc.) for laser radiation generation in the spectral range 2.7–3 ​μm. In the first part of this paper, the particular active media are discussed in detail. On the other hand, the experimental results summarized absorption and emission cross-section spectra together with decay times at upper (⁴I_11/2) and lower (⁴I_13/2) laser levels of all tested Er-doped samples at room temperature. Moreover, laser results in CW and pulsed laser regime with tunability curves, achieved in recent years, are presented, too.