Gadolinium vanadate doped with neodymium, Nd:GdVO4, is a promising material for diode pumped lasers. Like neodymium doped yttrium vanadate, the gadolinium vanadate exhibits a larger absorption and emission cross section compared to Nd:YAG. In fact, Nd:GdVO4 has a 7-times higher absorption cross section at 808nm and a 3-times larger emission cross section at 1.06µm than does Nd:YAG (Ref. 1). Nd:GdVO4 has the additional advantage over Nd:YVO4of a much higher thermal conductivity.
Nd:GdVO4 was first introduced as a laser material in 1992 by Zagumennyi, et al. (Ref. 2). Consequently, much less laser development and testing has occurred with gadolinium vanadate. The early results are, however, quite promising. Wang, et al. compared Nd:GdVO4 and Nd:YVO4 in a diode pumped arrangement (Ref. 3). In each case of cw laser performance at 1.06µm and 1.34µm and intracavity doubling with KTP and LBO, the gadolinium vanadate had a higher slope efficiency or optical conversion efficiency than did yttrium vanadate.
Poly-Scientific uses the Czochralski method to grow gadolinium vanadate. The crystal is tetragonal which means that there are two equivalent "a" directions and a "c" direction, all mutually orthogonal. A typical laser rod is oriented with the rod axis along an a-axis of the crystal. Maximum absorption of pump light occurs for polarization along the c-axis.
Demonstrated Performance in Diode Pumped Laser Systems
Laser
Operation |
Output Wavelength (µm) |
Frequency Doubler |
Slope Efficiency (%) |
Max.Optical Conversion Efficiency (%) |
Ref |
|
cw |
1.06 |
none |
44.6 |
n/a |
3 |
|
cw |
1.06 |
none |
42.9 |
38.1 |
4 |
|
cw |
1.34 |
none |
40.2 |
n/a |
3 |
|
cw |
0.53 |
KTP |
n/a |
21.0 |
3 |
|
cw |
0.67 |
LBO |
n/a |
2.8 |
3 |
|
Q-switched |
1.06 |
none |
31.6 |
n/a |
1 |
|
Q-switched |
0.53 |
KTP |
n/a |
25.0 |
4 |
Information Regarding Neodymium
Laser Host Crystals
| |
Nd:YVO4 |
Nd:GdVO4 |
Nd:YAG |
Laser wavelengths
(Ref. 5) |
1064.3 nm
1342.0 nm |
1062.9 nm
~1340 nm |
1064.2 nm
1338.2 nm |
Emission bandwidth
(linewidth at 1064 nm) |
0.8 nm |
No data |
0.45 nm |
Effective laser cross section
(emission cross section at 1064 nm) |
15.6 x 10-19cm-2
(Ref. 5) |
7.6 x 10-19cm-2
(Ref. 5) |
6.5 x 10-19cm-2 |
| Polarization |
Parallel to c-axis |
Parallel to c-axis |
unpolarized |
Radiative lifetime(microseconds)
at 1% Nd doping |
~ 100 µs
(Ref. 5) |
~ 95 µs
(Ref. 5) |
230 µs |
| Pump wavelength (Ref. 5) |
808.5 nm |
808.4 nm |
807.5 nm |
Peak pump absorption
at 1% doping (Ref. 5) |
~ 41 cm-1 |
~ 57 cm-1 |
|
| Thermal conductivity, W/mK |
5.1 |
11.7(Ref. 7) |
14 |
| Doping concentration range |
0.1 - 3.0% |
0.1 - 3.0% |
0.1 - 2.0% |
| Other possible dopants |
Tm, Ho, Er |
Tm, Ho, Er |
Cr,Tm, Ho, Er,Yb |
Material Properties: Comparing Nd:GdVO4 and Nd:YVO4
| |
Nd:GdVO4 |
Nd:YVO4 |
| Crystal Structure, Space Group |
Tetragonal, I41/amd
(Ref. 4) |
Tetragonal, I41/amd
(Ref. 4) |
| Lattice constants, nm |
a
b |
0.721
0.635
(Ref. 4) |
0.721
0.629 |
| Melting temperature, °C |
|
1780
(Ref. 6) |
1825 |
| Thermal expansion @25°C, x1-6/°C |
a
c |
1.5
7.3
(Ref. 4) |
4.43
11.4 |
| Specific heat @25°C, cal/mol K |
|
32.6
(Ref. 4) |
24.6 |
| dn / dT, x10-6/°C |
|
4.7
(Ref. 4) |
2.7
(Ref. 4) |
References
- C. Li, J. Song, D. Shen, N.S. Kim, J. Lu, K. Ueda, Appl. Phys. B, 70, 471 (2000)
- A.I. Zagumennyi, V.G. Ostroumov, I.A. Shcherbakov, T. Jensen, J.P. Meyen, G. Huber, Sov. J. Quantum Electron., 22, 1071 (1992)
- C.Q. Wang, Y.T. Chow, L. Reekie, W.A. Gambling, H.J. Zhang, L. Zhu , X.L. Meng, Appl. Phys. B, 70, 769 (2000)
- H. Zhang, J. Liu, J. Wang, C. Wang, L. Zhu, Z. Shao, X. Meng, X. Hu, M. Jiang, Y.T. Chow, J. Opt. Soc. Am.
- L. DeShazer, Laser Focus World (Feb. 1994)
- V.V. Kochurikhin, K. Shimamura, T. Fukuda, J. Crystal Growth, 151, 393 (1995)
- L. Qin, X. Meng, J. Zhang, L. Zhu, H. Zhang, B. Xu, H. Jiang, J. Crystal Growth, 242, 183 (2002)
|
SYNOPTICS
