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Neodymium-doped Laser Gain Media

Author: the photonics expert (RP)

Definition: laser gain media containing laser-active neodymium ions

More general term: solid-state laser gain media

Categories: article belongs to category optical materials optical materials, article belongs to category laser devices and laser physics laser devices and laser physics

DOI: 10.61835/xxh   Cite the article: BibTex plain textHTML   Link to this page   LinkedIn

Neodymium (chemical symbol: Nd) is a chemical element belonging to the group of rare earth metals. In laser technology, it is widely used in the form of the trivalent ion Nd3+ as the laser-active dopant of gain media based on various host materials, including both crystals and glasses.

The usual pump wavelength is 808 nm (for Nd:YAG; wavelengths for other host materials can somewhat differ), but a higher slope efficiency can be achieved by direct pumping into the upper laser level 4F3/2 with 869-nm light (which is sometimes called in-band pumping, although this is inaccurate). The strongest laser transition is that from 4F3/2 to 4I11/2 for 1064 nm, but other transitions are available with longer or shorter wavelengths (see Figure 1). In order to achieve lasing on those, lasing at the 1064-nm line needs to be suppressed by inserting an appropriate wavelength filter (usually consisting of one or more dichroic mirrors) into the laser resonator. Via multi-phonon emission, the populations in levels 4I11/2 to 4I15/2 are quickly transferred to the ground-state manifold 4I9/2. (The lower-state lifetime is much smaller than the upper-state lifetime.) Hence, there is normally negligible population in all these levels, so that neodymium-doped gain media exhibit pure four-level behavior. The exception is the case where the lower level is the ground-state manifold 4I9/2: 946-nm Nd:YAG lasers (and other Nd-based lasers emitting between 900 and 1000 nm) are quasi-three-level lasers, exhibiting a fairly high threshold pump power.

energy level structure of the trivalent neodymium ion in Nd^{3+}:YAG
Figure 1: Energy level structure of the trivalent neodymium ion (with wavelength numbers for Nd:YAG).

For high excitation densities, as can occur particularly in Q-switched lasers, but also in lasers operating on the weaker laser transitions, there can be significant energy losses due to energy transfer (→ upconversion) to higher-lying levels with small lifetimes.

Overview on Neodymium-doped Gain Media

The most common neodymium-doped gain media are:

Less common neodymium-doped gain media are:

  • Nd:GdVO4 (gadolinium vanadate) for 1064 and 1341 nm: similar to Nd:YVO4, but having a larger gain bandwidth
  • Nd:GDD (gadolinium gallium garnet): used for high-power heat capacity lasers
  • the tungstates Nd:KGW = Nd:KGd(WO4)2 and Nd:KYW = Nd:KY(WO4)2: birefringent, large gain bandwidth, large Raman cross-sections
  • Nd:YALO = Nd:YAlO3 for 1079 and 930 nm: birefringent
  • Nd:YAP = Nd:YAlO3 for 1079 or 1340 nm: high thermal conductivity, birefringent
  • Nd:LSB = Nd:LaSc3(BO3)4 for 1062, 905 and 1348 nm: birefringent; allows very high neodymium concentration
  • Nd:S-FAP = Nd:Sr5(PO4)3F for 1059, 923 and 1328 nm: birefringent

In all these media (except for some glasses), the neodymium dopant ions replace other ions (often yttrium) of the host medium which have about the same size.

Neodymium-doped gain media face competition from ytterbium-doped media in the 1-μm spectral region. Those have a smaller quantum defect, usually a higher emission bandwidth and a higher upper-state lifetime, also a simpler energy level structure which avoids various quenching processes. However, they exhibit quasi-three-level behavior, which tends to lead to a higher threshold pump power, so that the power efficiency is not necessarily better than for neodymium-doped media.

More to Learn

Encyclopedia articles:

Bibliography

[1]J. R. O'Connor, “Unusual crystal-field energy levels and efficient laser properties of YVO4:Nd”, Appl. Phys. Lett. 9, 407 (1966); https://doi.org/10.1063/1.1754631
[2]M. Ross, “YAG laser operation by semiconductor laser pumping”, Proc. IEEE 56, 196 (1968); https://doi.org/10.1109/PROC.1968.6220
[3]J. R. Thornton et al., “Properties of neodymium laser materials”, Appl. Opt. 8 (6), 1087 (1969); https://doi.org/10.1364/AO.8.001087
[4]G. A. Massey, “Measurements of device parameters for Nd:YAlO3 lasers”, IEEE J. Quantum Electron. 8 (7), 669 (1972); https://doi.org/10.1109/JQE.1972.1077254
[5]R. W. Waynant and P. H. Klein, “Vacuum ultraviolet laser emission from Nd3+:LaF3”, Appl. Phys. Lett. 46, 14 (1985); https://doi.org/10.1063/1.95833
[6]T. Y. Fan et al., “Nd:MgO:LiNbO3 spectroscopy and laser devices”, J. Opt. Soc. Am. B 3 (1), 140 (1986); https://doi.org/10.1364/JOSAB.3.000140
[7]A. I. Zagumennyi et al., “The Nd3+:GdVO4 crystal: a new material for diode-pumped lasers”, Sov. J. Quantum Electron. 22, 1071 (1992); https://doi.org/10.1070/QE1992v022n12ABEH003672
[8]S. Kück et al., “Excited state absorption and stimulated emission of Nd3+ in crystals. Part 1: Y3Al5O12, YAlO3, and Y2O3”, Appl. Phys. B 67 (2), 151 (1998); https://doi.org/10.1007/s003400050486
[9]L. Fornasiero et al., “Excited state absorption and stimulated emission of Nd3+ in crystals. Part 2: YVO4, GdVO4, and Sr5(PO4)3F”, Appl. Phys. B 67, 549 (1998); https://doi.org/10.1007/s003400050543
[10]J. L. Blows et al., “Heat generation in Nd:YVO4 with and without laser action”, IEEE Photon. Technol. Lett. 10 (12), 1727 (1998); https://doi.org/10.1109/68.730483
[11]N. Hodgson et al., “High power TEM00 mode operation of diode-pumped solid-state lasers”, Proc. SPIE 3611, 119 (1999); https://doi.org/10.1117/12.349265
[12]L. Fornasiero et al., “Excited state absorption and stimulated emission of Nd3+ in crystals III: LaSc3(BO3)4, CaWO4, and YLiF4”, Appl. Phys. B 68, 67 (1999); https://doi.org/10.1007/s003400050587
[13]Y. Sato and T. Taira, “The studies of thermal conductivity in GdVO4, YVO4, and Y3Al5O12 measured by quasi-onedimensional flash method”, Opt. Express 14 (22), 10528 (2006); https://doi.org/10.1364/OE.14.010528
[14]D. Krennrich et al., “A comprehensive study of Nd:YAG, Nd:YAlO3, Nd:YVO4 and Nd:YGdVO4 lasers operating at wavelengths of 0.9 and 1.3 μm. Part 1: cw-operation”, Appl. Phys. B 92, 165 (2008); https://doi.org/10.1007/s00340-008-3069-4
[15]D. Krennrich et al., “A comprehensive study of Nd:YAG, Nd:YAlO3, Nd:YVO4 and Nd:YGdVO4 lasers operating at wavelengths of 0.9 and 1.3 μm. Part 2: passively mode-locked operation”, Appl. Phys. B 92, 175 (2008); https://doi.org/10.1007/s00340-008-3070-y

(Suggest additional literature!)


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Suppliers

The RP Photonics Buyer's Guide contains 55 suppliers for neodymium-doped laser gain media. Among them:

Laserton

neodymium-doped laser gain media

Laserton has neodymium-doped laser crystals, specifically Nd:YAG and Nd:YVO4.

EKSMA OPTICS

neodymium-doped laser gain media

EKSMA Optics has high optical quality Nd:YAG laser crystals – rods with high damage threshold AR@1064 nm coatings. Custom Nd:YAG rods can be manufactured on request.

Shalom EO

neodymium-doped laser gain media

Shalom EO offers three types of Nd-doped laser gain media, including Nd:YAG, Nd:Ce:YAG and Nd:YVO4 laser crystals for solid-state lasers.

  • Nd: YAG laser crystals are the most popular lasing media for solid-state lasers. Shalom EO offers the standard Nd:YAG rods with AR coating at 1064 nm and customized rods or crystals upon the customer's special request.
  • Nd:YVO4 crystals are often utilized in combination with high-coefficient NLO crystals (such as LBO, BBO, KTP) to convert the wavelengths of laser output from infrared to green, blue, and ultra-violet. Shalom EO offers the Nd:YVO4 crystals with an Nd doping range of 0.1% – 3% and with a maximum size of 20 × 20 mm diameter.
  • Nd:Ce:YAG crystal is an excellent laser gain media used for non-water-cooled lasers and miniature laser systems. Shalom EO offers Nd:Ce:YAG crystals, different doping concentrations and specifications are available for selection.

Exail

neodymium-doped laser gain media

Exail (formerly iXblue) offers a complete range of neodymium-doped fibers with some unique properties, ideal for fiber lasers between 890 and 1100 nm.

Exail neodymium aluminosilicate double clad fibers have been developed to maximize fiber efficiency through a precisely controlled host composition. Compared to a standard neodymium-doped fiber, the 1.06-μm emission is reduced through careful fiber design optimization. Our double clad fibers are routinely tested to various parameters such as photodarkening and environmental behavior.

Single clad fibers are also proposed and would be ideal to build seeder sources.

Benefits and features:

  • host composition optimized for high energy efficiency and low clustering
  • high NA, high performance low-index cladding
  • low splicing losses, low background losses, low macrobending losses at the operating wavelength

Applications: 0.9 to 1.064-μm fiber lasers, seeder sources at 10xx nm.

Optogama

neodymium-doped laser gain media

Optogama offers various types of neodymium-doped laser crystals:

  • Nd:KGW crystals exhibit strong and broad absorption and emission bands without significant luminescence quenching even for high doping concentrations. Optogama offers Nd:KGW crystals for medium-power but highly efficient continuous-wave (CW), Q-switched and mode-locked lasers with diode-laser and flashlamp pumping. In addition, it is possible to use Nd:KGW crystal for efficient self-Raman conversion.
  • Nd:YLF is characterized by a long lifetime of the 4F3/2 upper laser level. Compared to Nd:YAG, the negative dn/dT leads to lower thermal distortions and thus to a better output beam quality. Another distinctive feature is high UV transparency, which is favorable for pumping with xenon flashlamps.

Fibercore

neodymium-doped laser gain media

Fibercore has delivered over 40 years of innovation and excellence in developing and manufacturing speciality optical fiber. All of our fiber products have been developed with our customers in mind with market leading capabilities to produce an extensive range of fibers including;

We are continuously expanding our product ranges to cover wider and more demanding customer applications. So if you have a specific development project or require a custom fiber, we would like to discuss it further with you. We will work together with you to find the best solution.

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