Transition-metal-doped Laser Gain Media
Author: the photonics expert Dr. Rüdiger Paschotta
Definition: laser gain media which are doped with transition metal ions
More general term: laser gain media
Categories: optical materials, laser devices and laser physics, optical amplifiers
DOI: 10.61835/gk1 Cite the article: BibTex plain textHTML Link to this page LinkedIn
A number of solid-state laser gain media are doped with transition metal ions. Those have optical transitions involving the electrons of the 3d shell. Table 1 gives an overview of the most common transition metal ions and their host media.
Ion | Common host media | Typical emission wavelengths |
---|---|---|
titanium (Ti3+) | sapphire | 0.65–1.1 μm |
divalent chromium (Cr2+) | zinc chalcogenides such as ZnS, ZnSe, and ZnSxSe1-x | 1.9–3.4 μm |
trivalent chromium (Cr3+) | ruby (Al2O3), alexandrite (BeAl2O4); LiSAF, LiCAF, LiSAF, and similar fluorides | 0.7–0.9 μm |
tetravalent chromium (Cr4+) | YAG, MgSiO4 (forsterite) and other silicates | 1.1–1.65 μm |
divalent iron (Fe2+) | ZnSe, ZnS, CdSe | 4–5 μm |
More exotic ions for lasers are cobalt (Co2+) and nickel (Ni2+).
A common property of transition metal ions is that the corresponding absorption and laser transitions have a very broad bandwidth, leading in particular to a very large gain bandwidth. This results from the strong interaction of the electronic transitions with phonons (→ vibronic lasers), which is a kind of homogeneous broadening. Nevertheless, the transition cross-sections can be reasonably high – of the same order as those of rare-earth-doped laser gain media having a much smaller transition bandwidth.
Laser-active transition metal ions are basically always used in crystals rather than glasses as host media, since crystals offer a higher thermal conductivity and the additional inhomogeneous broadening from glasses would hardly be useful.
The most important lasers based on transition-metal-doped gain media are titanium–sapphire lasers and various lasers based on chromium-doped laser gain media such as Cr4+:YAG or Cr3+:LiSAF. Less common are lasers based on media such as Co2+:MgF2, Co2+:ZnF2 and Ni2+:MgF2. They are particularly used for mode-locked lasers, generating ultrashort pulses, and for broadly tunable lasers.
More to Learn
Encyclopedia articles:
- chromium-doped laser gain media
- rare-earth-doped laser gain media
- vibronic lasers
- titanium–sapphire lasers
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Bibliography
[1] | R. Scheps, “Cr-doped solid-state lasers pumped by visible laser diodes”, Opt. Mater. 1, 1 (1992); https://doi.org/10.1016/0925-3467(92)90011-B |
[2] | E. Sorokin et al., “Ultrabroadband infrared solid-state lasers”, J. Sel. Top. Quantum Electron. 11 (3), 690 (2005); https://doi.org/10.1109/JSTQE.2003.850255 (a review mainly concerning Cr2+ and Cr4+ lasers) |
[3] | S. B. Mirov et al., “Recent progress in transition-metal-doped II–VI mid-IR lasers”, J. Sel. Top. Quantum Electron. 13 (3), 810 (2007); https://doi.org/10.1109/JSTQE.2007.896634 |
[4] | V. V. Fedorov et al., “3.77–5.05-μm tunable solid-state lasers based on Fe2+-doped ZnSe crystals operating at low and room temperatures”, IEEE J. Quantum Electron. 42 (9), 907 (2006); https://doi.org/10.1109/JQE.2006.880119 |
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