|Transmitting Wavefront Distortion||less than λ/4 @ 633nm||Clear Aperture||>90% central area|
|Flatness||λ/8 @ 633 nm||Surface Quality||10/5 S/D|
|Parallelism||better than 10 arc seconds||Perpendicularity||≤5 arc minutes|
|Angle Tolerance||≤0.5°||Quality Warranty Period||one year under proper use|
Physical and Optical Properties:
|Atomic Density||1.26x1020 atoms /cm3 (Nd1.0%)||Crystal Structure||Zircon Tetragonal, space group D4h-I4/amd
|Thermal Expansion Coefficient (300K)||αa=4.43x10-6 /K
|Thermal Conductivity Coefficient (300K)||//C:0.0523W/cm/K
|Lasing Wavelength||1064nm,1342nm||Thermal Optical Coefficient (300K)||dno/dT=8.5×10-6 /K
|Stimulated Emission Cross-section||25×10-19cm2 @ 1064nm||Thermal Optical Coefficient (300K)||dno/dT=8.5×10-6 /K
|Stimulated Emission Cross-section||25×10-19cm2@ 1064nm||Fluorescent Lifetime||90μs(1% Nd doping)|
|Absorption Coefficient||31.4cm-1@810nm||Intrinsic Loss||0.02cm-1@1064nm|
|Gain Bandwidth||0.96nm@1064nm||Polarized Laser Emission||π polarization; parallel to optic axis(c-axis)|
|Diode Pumped Optical to Optical Efficiency||>60%||Sellemeier equations (λ in μm)||n02=3.77834+0.069736/(λ2-0.04724)-0.010813λ2
Laser Properties of Nd:YVO4
1. One of the most attractive character of Nd:YVO4 is, compared with Nd:YAG, it has 5 times larger absorption coefficient in a broader absorption bandwidth around the 808 nm peak pump wavelength, which just matches the standard of high power laser diodes currently available. This means a smaller Nd:YVO4 crystal that could be used for the laser, leading to a more compact laser system. For a given output power, this also means a lower power level at which the laser diode operates, thus extending the lifetime of the expensive laser diode. The broader absorption bandwidth of Nd:YVO4 which may reaches 2.4 to 6.3 times that of Nd:YAG, is also valuable. Besides more efficient pumping, Nd:YVO4 also means a broader range of selection of diode specifications. This will be helpful to laser system makers for wider tolerance and lower cost choice.
2. Nd:YVO4 crystal has larger stimulated emission cross-sections, both at 1064nm and 1342nm. When a-axis cut Nd:YVO4 crystal lasing at 1064m, it is about 4 times higher than that of Nd:YAG, while at 1340nm the stimulated cross-section is 18 times larger, which leads to a CW operation completely outperforming Nd:YAG at 1320nm. These make Nd:YVO4 laser be easy to maintain a strong single line emission at the two wavelengths.
3. Another important character of Nd:YVO4 lasers is, because it is an uniaxial rather than a high symmetry of cubic as Nd:YAG, what it emits is only a linearly polarized, thus avoiding undesired birefringent effects on the frequency conversion. Although the lifetime of Nd:YVO4 is about 2.7 times shorter than that of Nd:YAG, its slope efficiency can be still quite high for a proper design of laser cavity, because of its high pump quantum efficiency.
The major laser properties of Nd:YVO4 vs Nd:YAG are listed in Table below, including stimulated emission cross-sections (σ), Absorption Coefficient (α) Fluorescent lifetime (τ),Absorption Length (La),threshold Power (Pth) and Pump Quantum Efficiency (ηs).
Laser Properties of Nd:YVO4 vs Nd:YAG
|Laser Crystal||Doping (atm%)||σ
Typical Results of Nd:YVO4
Diode pumped Nd:YVO4 laser output comparing with diode pumped Nd:YAG laser.
|Crystals||Size (mm3)||Pump Power||Output (at 1064nm)|
Nd:YVO4’s advantages over Nd:YAG
As high as about five times larger absorption efficient over a wide pumping bandwidth around 808nm (therefore, the dependency on pumping wavelength is much lower and a strong tendency to the single mode output).
As large as three times larger stimulated emission cross-section at the lasing wavelength of 1064nm.
Lower lasing threshold and higher slope efficiency.
As a uniaxial crystal with a large birefringence, the emission is only linearly polarized.