Low lasing threshold and high slope efficiency
Large stimulated emission cross-section at lasing wavelength
High absorption over a wide pumping wavelength bandwidth
Optically uniaxial and large birefringence emits polarized laser
1. Basic Properties
Atomic Density: ~1.37x10 20 atoms/cm 2 |
Crystal Structure: Zircon Tetragonal, space group D 4h , a=b=7.12, c=6.29 |
Density: 4.22 g/cm 2 |
Mohs Hardness: Glass-like, ~5 |
Thermal Expansion Coefficient: a a =4.43x10 -6 /K, a c =11.37x10 -6 /K |
Thermal Conductivity Coefficient:||C: 5.23 W/m/K; ^C: 5.10 W/m/K |
2. Optical Properties (typically for 1.1 atm% Nd:YVO4, a-cut crystals)
Lasing Wavelengths |
914nm, 1064 nm, 1342 nm |
Crystal class |
positive uniaxial, n o =n a =n b , n e =n c ,
n o =1.9573, n e =2.1652, @ 1064nm
n o =1.9721, n e =2.1858, @ 808nm
n o =2.0210, n e =2.2560, @ 532nm |
Sellmeier Equation (for pure YVO4 crystals):
n o 2 =3.77834+0.069736/(l 2 - 0.04724) - 0.0108133.l 2
n e 2 =4.59905+0.110534/(l 2 - 0.04813) - 0.0122676.l 2 |
| Thermal Optical Coefficient: |
dn a /dT=8.5x10 -6 /K, dn c /dT=3.0x10 -6 /K |
| Stimulated Emission Cross-Section |
25.0x10 -19 cm 2 , @1064 nm |
Fluorescent Lifetime |
90 ms (about 50 ms for 2 atm% Nd doped) @ 808 nm |
Absorption Coefficient |
31.4 cm -1 @ 808 nm |
Absorption Length |
0.32 mm @ 808 nm |
Intrinsic Loss |
Less 0.1% cm -1 , @1064 nm |
| Gain Bandwidth |
0.96 nm (257 GHz) @ 1064 nm |
Polarized Laser Emission |
p polarization; parallel to optic axis (c-axis) |
Diode Pumped Optical to Optical Efficiency |
> 60% |
3. Absorption Curves of Different Doping Nd:YVO4
Nd:YVO4 shows high absorption coefficients at pumping wavelengths. Therefore, a crystal short-in-length (e.g. 1mm) is preferred, and more compact lasers can be constructed by using Nd:YVO4 than using Nd:YAG. Furthermore, it has a wide and smoothly-varied bandwidth of absorption, so that it allows of less stringent requirements of diode laser selection and wavelength control as compared with Nd:YAG. Different doping levels Nd:YVO4 are shown showed as follow
 |
 |
Absorption Curve of 0.5% doping YVO4
(Thickness:1 mm) |
Absorption Curve of 3% doping YVO4
(Thickness:1 mm)
|
4. Fluorescence Spectra Curve
 |
 |
| (a) |
(b) |
Normalized fluorescence spectra from 800 nm to 1600 nm of Nd 1.1 at. % doped Nd:YVO4 for p polarization (a) and for s porlarization (b).
5. Laser Properties
The Nd:YVO4 crystal has large stimulated emission cross-sections (s) at both 1.06 mm and 1.3 mm. The stimulated emission cross-section of an a-axis cut Nd:YVO4 crystal at 1.064mm is about 4 times that of the Nd:YAG crystal. Although the lifetime (t) of Nd:YVO4 is about 2.7 times shorter than that of Nd:YAG, a figure of merit (FOM) for minimum threshold of a-cut Nd:YVO4, which is proportional to the products, is reasonably higher than that of Nd:YAG crystal. Because of its high pump quantum efficiency (hp), the slope efficiency of Nd:YVO4 can be very high if the laser cavity is properly designed. The following Table lists the major laser properties of Nd:YVO4 in comparison with those of Nd:YAG.
Laser properties of Nd:YVO4 crystals vs Nd:YAG
Laser crystal |
Nd doped(atm%) |
ó
(x10 -19 cm 2 ) |
a
(cm -1 ) |
t
(ms) |
l a
(mm) |
P th
(mw) |
? s
( %) |
Nd:YVO4(a-cut) |
1.1
2 |
25 |
31.2
72.4 |
90
50 |
0.32
0.14 |
78 |
48.6 |
Nd:YVO4(c-cut) |
1.1 |
7 |
9.2 |
90 |
|
231 |
45.5 |
Nd:YAG |
0.85 |
6 |
7.1 |
230 |
1.41 |
115 |
38.6 |
Furthermore, the 1.34 mm CW operation of the Nd:YVO4 laser completely outperformed that of Nd:YAG at 1.32 mm because of an 18 times larger stimulated cross-section.
Nd:YVO4 crystal has a low thermal conductivity coefficient, therefore, long-in-length with low dopant level Nd:YVO4 is recommended for high power diode laser application in order to reduce thermal lasing effects. Gold metalization on the side of Nd:YVO4 crystals is the solutions not only for thermal lasing effects for high power pumped, but also enhancing lasing mode of the laser. If you have any questions, please ask CASIX salesmen for assistance.
6. Diode Laser-Pumped Nd:YVO4 Lasers
tA threshold of 78 mW and a slope efficiency of 48.5% at 1.064 mm were obtained by using an a-cut 3 mm long Nd:YVO4 crystal with output coupler R = 96%. Under the same conditions, a 5 mm long Nd:YAG crystal has a threshold of 115 mW and a slope efficiency of 38.6%.
tRecently, over 30 W of TEM00 output power was achieved by using a-cut Nd:YVO4 and pumped by 60 W fiber coupled diode lasers. The optical conversion efficiency exceeds 50%. High power and stable infrared output @ 1064 nm and 1342 nm has been available with diode pumped Nd:YVO4 lasers.
tSingle-longitudinal-mode oscillation of a Nd:YVO4 microchip laser has been achieved with high power and high slope efficiency. Such a single mode source has been developed for the use of a master oscillator for injection locking of Nd laser systems.
tBecause of its large stimulated emission cross section at 1.34 mm, Nd:YVO4 is also an efficient laser crystal for diode laser-pumped 1.3 mm laser. By using 1 mm long Nd:YVO4 crystal and pumped by an 850 mW diode laser at 808 nm, 50 mW output at 1.34 mm has been observed, compared to 34 mW from 2 mm long Nd:YAG.
7. Frequency-doubled Nd:YVO4 Lasers
v By using the compact design of Nd:YVO4 + KTP crystals, high power green or red light output can be generated in a diode laser pumped Nd:YVO4 laser. When pumped by a 890 mW diode laser, more than 76 mW single mode (TEM00) green output was obtained with a 3x3x1 mm3 Nd:YVO4 and a 3x3x5 mm3 intracavity KTP.
v Diode pumped green lasers has been commercialized with the compact design of Nd:YVO4 + KTP crystals. 2.5 mW green output was achieved in a Nd:YVO4 microchip laser with a very short (9 mm) laser cavity when pumped by a 50 mW diode laser.
v Over 10 W and high stable CW green output @ 532 nm was commerially available with diode pumped Nd:YVO4 and frequency double using NCPM LBO crystals. Sigle longitudinal mode (SLM) green output, Q-switched green and UV outputs were also obtained.
v Over 400 mW blue laser @ 457 nm based on Nd:YVO4+ BBO crystals, is commerical available .
Standard Specs and Note
Standard Specs. of CASIX's Nd:YVO4 Crystals
Nd: Dopant Level |
0.1 - 3.0 atm% |
Standard Dimensions |
3x3x3 mm 3 , 3x3x1 mm 3 , 3x3x0.5 mm 3 |
Wavefront Distortion |
< l/8 at 633 nm |
Scattering Sites |
invisible, probed with a He-Ne laser |
Orientation |
±0.5 deg |
Dimensional Tolerance |
+0.1/-0.1 mm |
End-faces Configuration |
Plano/Plano |
Surface quality |
10/5 Scratch/Dig per MIL-O-13830B |
Flatness |
l/10 at 633 nm |
Clear Aperture |
> Central 90% |
Parallelism |
< 10 arc sec. |
Intrinsic Loss |
< 0.1% cm -1 |
Note:Other specifications of Nd:YVO4 crystals and coatings are available upon request.
CASIX provides the complete diode pumped laser kits, including laser crystals (Nd:YVO4 and Nd:YAG), NLO crystals (KTP) and laser optics.
Please refer to DPSS laser kits for information about diode pumped laser optics kits.
