In the past few years major improvements in laser crystals have been made. This can be seen in the higher efficiency of certain materials available on the market. In the following text we would like to compare two common laser rod materials.
Neodymium yttrium vanadate (Nd:YVO4) is one of the most efficient laser crystals currently available for diode-pumped solid-state laser systems. The large stimulated emission cross-section at the lasing wavelength, the high absorption coefficient, and the large absorption bandwidth of pump wavelengths are a few of the reasons why this crystal is extremely efficient. The high damage threshold for laser applications and the strong physical, optical, and mechanical properties of the Nd:YVO4 make it an excellent crystal for high power applications in diode-pumped solid-state laser.
However, Nd:YAG laser crystals are still the most important laser rods because they are so widely used. They can be found in all types of solid-state lasers, but are mainly used in frequency-doubled and CW laser systems as well as high energy, Q-switched lasers.
In the table below, the material properties of Nd:YVO4 and Nd:YAG crystals are itemised and the resulting effects on the laser systems described with respect to parameters given.
| Properties | Nd:YVO4 | Nd:YAG | Remarks |
| Laser wavelength | 1064 nm | 1064 nm | Same |
| Emission bandwidth | 0.8 nm | 0.45 nm | |
| Stimulated emission cross | 25 x 10-19 cm² | 4.8 x 10-19 | Nd:YVO4 much more efficient. |
| Polarisation | Parallel to C-axis | Unpolarised | Nd:YVO4 already polarised. |
| Fluorescence lifetime | 98 µs | 230 µs | Nd:YAG CW also possible. |
| Pump wavelength | 808.5 nm | 807.5 nm | Standard laser diodes available. |
| Max. absorption coefficient | 28 cm-1 (doped at 1.0%) | 7.1 cm-1 (doped at 1.1%) | Nd:YVO4 much more efficient. |
| Thermal conductivity | 0.05 Wcm-1 K-1 | 0.13 Wcm-1 K-1 | Better with Nd:YAG. With Nd:YVO4 assembly more compact. |
| Absorption cross-section | 2.7 x 10-19 cm² | 0.74 x 10-19 | Assembly very compact. |
| Absorption bandwidth | 20 nm | 3 nm | Nd:YVO4: No selection or temperature stabilisation necessary for pump diodes. |
Compared to diode-pumped Nd:YAG lasers, Nd:YVO4 systems have the advantage that they depend less on the pump wavelength and temperature control of laser diodes. Furthermore, the absorption band is wider and the slope efficiency higher. The lasing threshold is lower and the laser works with polarised light as well as in single mode operation.
Nd:YVO4 crystals have a large stimulated emission cross-section at both 1.06 µm and 1.3 µm. This value is approximately 4 times higher at the a-axis section and 1064 nm. The efficiency cross section for stimulated emission in the 1.3 µm range for CW applications is over 18 times higher than with Nd:YAG. Compared to other laser crystals, the fluorescence lifetime of Nd:YAG is approximately double what it is of Nd:YVO4. The thermal conductivity of Nd:YAG is superior to that of Nd:YVO4.
Nd:YVO4 is thus an excellent laser crystal for diode-pumped solid-state lasers. With Nd:YVO4 you can generate high power IR lasers, or even green and blue lasers using frequency-doubling crystals. These advantages make Nd:YVO4 appear to be the better choice, that is as long as one is dealing with compact lasers of lower power. However, Nd:YVO4 is not suited for lamp-pumped or CW systems.
Nd:YAG is still the most commonly used type of crystal for solid-state lasers and is used in frequency-doubled systems as well as high power Q-switched systems. Blue lasers are generated by doubling the frequency of 946 nm using Nd:YAG. This material is suited for high power lasers up to the kW range. Due to the cubic symmetry and high quality, lasers can be easily operated in the TEM00 basic mode.
Regardless of which laser crystal you choose, LASER COMPONENTS offers not only Nd:YVO4 and Nd:YAG rods, but also a variety of other laser crystals.
We would be happy to assist you in this regard.
