vanadate lasers (original) (raw)

Definition: lasers based on rare-earth-doped yttrium, gadolinium or lutetium vanadate crystals, usually Nd:YVO4

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Related: laser crystalsYAG lasersYLF lasersneodymium-doped laser gain mediarare-earth-doped laser gain mediamode-locked lasersQ-switched Lasers: YAG versus VanadateNd:YVO4 Laser with Polarization-Independent Pump Absorption

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Contents

What are Vanadate Lasers?

The term vanadate laser is usually used for lasers based on neodymium-doped vanadate crystals. In particular, these include yttrium vanadate (Nd:YVO4), gadolinium vanadate (Nd:GdVO4), and lutetium vanadate (Nd:LuVO4). These vanadates are also called orthovanadates. Such materials have been known for a long time [1], but became popular only many years later because for a long period it was difficult to grow them with high optical quality in sufficiently large sizes. Apart from progress in crystal growth, the advent of diode pumping increased the interest in vanadates also because much smaller crystals could be used, while lamp-pumped lasers usually require rather long laser rods.

There are also vanadate crystals doped with other rare earth ions, e.g. with ytterbium (Yb3+), erbium (Er3+), thulium (Tm3+) or holmium (Ho3+) doping. Due to the similar size, yttrium, gadolinium or lutetium ions can be replaced by laser-active rare earth ions without strongly affecting the lattice structure. This is important e.g. for preserving high thermal conductivity of the doped materials.

Vanadate crystals are naturally birefringent, which eliminates thermally induced depolarization loss in high-power lasers. Also, the laser gain is strongly polarization dependent (→ polarization of light); the highest gain is usually achieved for polarization along the ($c$) axis. The pump absorption is also strongly polarization-dependent (except at special wavelengths), which can cause problems e.g. when using a fiber-coupled pump source with drifting polarization.

For Nd:YVO4, the typical laser emission wavelength is 1064 nm, i.e., essentially the same as for Nd:YAG. Other important emission wavelengths are 914 and 1342 nm; those differ substantially from those of Nd:YAG. The 1342-nm emission line is much stronger than the corresponding 1.32-ÎŒm line in Nd:YAG, thus allowing for much better performance in 1.3-ÎŒm operation.

Property Value
chemical formula Nd3+:YVO4
crystal structure tetragonal
mass density 4.22 g/cm3
Moh hardness 5–6
Young's modulus 133 GPa
tensile strength 53 MPa
melting point 1810 °C
thermal conductivity ≈ 5 W / (m K) (values around 9–12 are also found in the literature)
thermal expansion coefficient 11 × 10−6 K−1 (($c$) direction), 4.4 × 10−6 K−1 (($a$) direction)
transparency range 0.3–2.5 ÎŒm
birefringence positive uniaxial
refractive index at 1064 nm 2.17 for ($c$) polarization (extraordinary), 1.96 ordinary index
temperature dependence of refractive index 3 × 10−6 K−1 in ($c$) direction, 8.5 × 10−6 K−1 in the ($a$) direction
Nd density for 1% at. doping 1.24 × 1020 cm−3
fluorescence lifetime 90 ÎŒs
absorption cross-section at 808 nm 60 × 10−20 cm2 (($c$) polarization)
emission cross-section at 1064 nm 114 × 10−20 cm2 (($c$) polarization)
gain bandwidth 1 nm

Table 1: Some properties of Nd:YVO4 = neodymium-doped yttrium vanadate.

Comparison of Nd:YVO4 and Nd:YAG

Nd:YVO4 lasers are usually diode-pumped, but can also be lamp-pumped. Compared with Nd:YAG (→ YAG lasers), Nd:YVO4 exhibits a much higher pump absorption and gain (due to the very high absorption and laser cross-sections), a broader gain bandwidth (around 1 nm), a much broader wavelength range for pumping (often eliminating the need to stabilize the pump wavelength), a shorter upper-state lifetime (≈ 100 ÎŒs for not too high neodymium concentrations), a higher refractive index, a lower thermal conductivity, and birefringence. The consequences of these differences for various modes of laser operation are the following:

Other Nd-doped Vanadate Crystals

Compared with Nd:YVO4, Nd:GdVO4 has a similar thermal conductivity, a slightly shorter emission wavelength (1063 nm), a somewhat larger gain bandwidth, lower emission cross-sections, and still higher pump absorption. Note, however, that the published data concerning thermal conductivity of vanadate crystals differ considerably, so there are some significant uncertainties.

Frequently Asked Questions

This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).

What is a vanadate laser?

A vanadate laser is a type of solid-state laser that uses a vanadate crystal as the laser gain medium. The most common types are based on crystals like yttrium vanadate (YVO4) or gadolinium vanadate (GdVO4), typically doped with neodymium ions.

What are the main advantages of Nd:YVO4 compared to Nd:YAG?

Compared to Nd:YAG, Nd:YVO4 has a much higher pump absorption and laser gain, a broader gain bandwidth, and a wider pump wavelength range. Its natural birefringence also eliminates thermally induced depolarization loss in high-power operation.

For which applications are Nd:YVO4 lasers particularly well suited?

Nd:YVO4 is excellent for low-threshold continuous-wave lasers and for passively mode-locked lasers operating at very high pulse repetition rates. It is also well suited for Q-switched lasers with high repetition rates, though not for achieving the highest pulse energies.

What are the common emission wavelengths of an Nd:YVO4 laser?

The primary emission wavelength is 1064 nm, just like for Nd:YAG. Other important transitions are at 914 nm and 1342 nm. The 1342-nm emission is particularly strong compared to the corresponding line in Nd:YAG.

Do vanadate lasers always emit polarized light?

Yes, because vanadate crystals are birefringent, their laser gain is strongly dependent on polarization. This leads to a naturally linearly polarized output, typically along the crystal's c-axis where the gain is highest.

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Bibliography

[1] J. R. O'Connor, “Unusual crystal-field energy levels and efficient laser properties of YVO4:Nd”, Appl. Phys. Lett. 9, 407 (1966); doi:10.1063/1.1754631
[2] A. I. Zagumennyi et al., “The Nd3+:GdVO4 crystal: a new material for diode-pumped lasers”, Sov. J. Quantum Electron. 22, 1071 (1992); doi:10.1070/QE1992v022n12ABEH003672
[3] J. L. Blows et al., “Heat generation in Nd:YVO4 with and without laser action”, IEEE Photon. Technol. Lett. 10 (12), 1727 (1998); doi:10.1109/68.730483
[4] N. Hodgson et al., “High power TEM00 mode operation of diode-pumped solid-state lasers”, Proc. SPIE 3611, 119 (1999); doi:10.1117/12.349265
[5] 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); doi:10.1364/OE.14.010528
[6] N. Pavel et al., “In-band pumping of Nd-vanadate thin-disk lasers”, Appl. Phys. B 91 (3-4), 415 (2008); doi:10.1007/s00340-008-3013-7
[7] J. Liu et al., “Comparative study of high-power continuous-wave laser performance of Yb-doped vanadate crystals”, IEEE J. Quantum Electron. 45 (7), 807 (2009); doi:10.1109/JQE.2009.2014253
[8] Y. Yan et al., “Near-diffraction-limited, 35.4 W laser-diode end-pumped Nd:YVO4 slab laser operating at 1342 nm”, Opt. Lett. 34 (14), 2105 (2009); doi:10.1364/OL.34.002105
[9] D. Sangla et al., “Highly efficient Nd:YVO4 laser by direct in-band diode pumping at 914 nm”, Opt. Lett. 34 (14), 2159 (2009); doi:10.1364/OL.34.002159
[10] G. Turri et al., “Temperature-dependent stimulated emission cross-section in Nd3+:YVO4 crystals”, J. Opt. Soc. Am. B 26 (11), 2084 (2009); doi:10.1364/JOSAB.26.002084
[11] X. DĂ©len et al., “Temperature dependence of the emission cross-section of Nd:YVO4 around 1064 nm and consequences on laser operation”, J. Opt. Soc. Am. B 28 (5), 972 (2011); doi:10.1364/JOSAB.28.000972
[12] Yu Fu et al., “Photon–phonon collaboratively pumped laser”, Nature Commun. 14, 8110 (2023); doi:10.1038/s41467-023-43959-9

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