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Neodymium Doped Yttrium Orthvanadate (Nd:YVO4)

Neodymium doped yttrium vanadate (Nd:YVO4) is a very efficient laser host crystal which is available for diode laser pumped solid state lasers. It is an excellent crystal for a high power, stable and cost effective solid state laser sources due to a high laser induced damage threshold, good mechanical and optical properties, a large stimulated emission cross-section at lasing wavelength, a high absorption coefficient and a wide absorption bandwidth at pumping wavelength. Recent developments have shown that Nd:YVO4 can produce powerful and stable IR, green, blue lasers with the design of Nd:YVO4 and frequency doubling crystals.

Features:  

  • Low lasing threshold and high slope efficiency
  • Large stimulated emission cross-section at lasing wavelength
  • High absorption over a wide pumping wavelength bandwidth
  • Polarized laser source generation due to optical birefringence

Absorption Curves of Different Doping Concentrations:  

Due to a high absorption coefficient at the pumping wavelength 808nm, a short crystal around 1mm is preferred and a compact laser can be constructed. Nd:YVO4 has a wide absorption bandwidth, which does not require a stringent wavelength control and diode laser selection. Figure 1 & 2 show absorption curves at two different doping concentrations.

 

 

Figure 1: Absorption curve of 1 mm Nd:YVO4 with a doping concentration 0.5%

 

 

Figure 2: Absorption curve of 1 mm Nd:YVO4 with a doping concentration 3%

Fluorescence Spectra Curves:  

Figure 3 & 4 show fluorescence spectra curves of a-cut Nd:YVO4 with a doping concentration 1.1%. Figure 3 & 4 are for polarization state parallel and perpendicular to z axis respectively.

 

 

Figure 3: Normalized fluorescence spectra curve of polarization parallel to z axis

 

 

Figure 4: Normalized fluorescence spectra curve of polarization perpendicular to z axis

Laser Properties:  

The Nd:YVO4 crystal has large stimulated emission cross-sections at both 1064nm and 1342nm. The stimulated emission cross-section of an a-axis cut Nd:YVO4 crystal at 1064nm is about 4 times higher than that of the Nd:YAG crystal. Although the lifetime of Nd:YVO4 is about 2.7 times shorter than that of Nd:YAG, the slope efficiency of a Nd:YVO4 laser can be very high if the laser cavity is properly designed due to its high pump quantum efficiency . Table 1 lists the major laser properties of Nd:YVO4 in comparison with those of Nd:YAG. Table 2 lists the Nd:YVO4 crystal properties.

  Laser Crystals  Doping
(atm%)
σ
(×10-19cm2)
α
(cm-1)
τ
(us)
Pth
(mw)
η
(%)
 
  Nd:YVO4 (a-cut)
1.1
2.0
25
27
48
90
50
35
78
48.6
 
  Nd:YVO4 (c-cut) 1.1
7
9.2
90
231
45.5
 
  Nd:YAG 0.85 
6
7.1 
230 
115
38.6
 
  Table 1: Laser properties of Nd:YVO4 and Nd:YAG
     
 
  Crystal Structure Tetragonal, D4h  
  lattice constant (Å) a = b = 7.12, c = 6.29
 
  Melting Point (°C) 1825
 
  Mohs Hardness ≈ 5
 
  Density (g/cm^3) 4.22
 
  Absorption Coefficient (/cm at 808nm) ||C: 27
  C: 13
  Intrinsic Absorption Coefficient
  (/cm at 1064nm)
<0.001
 
  Lasing Wavelength (nm)
914, 1064, 1342
  Stimulated Emission Cross-section (cm2)
25.0×10-19
 
  Fluorescent Lifetime (us)
90 at 808nm
 
  Gain Bandwidth (nm)
0.96
 
  Polarized Laser Emission
Parallel to c-axis
 
  Diode Pumped Optical to Optical Efficiency (%)
> 60
 
  Coefficient of Thermal Expansion (25°C)  ( /K)
||C: 4.43X10-6
C: 11.37X10-6
 
  Thermal Conductivity (25°C)
(W/mK)
||C: 5.23
C: 5.10
 
  Constant of Dispersion (dn/dT)  (/K) dno/dT = 8.5X10-6
dne/dT = 3.0X10-6
 
  Refractive Indices ne = 2.1652, no =1.9573 at 1064nm
  ne = 2.1858, no = 1.9721 at 808nm
  ne = 2.2560, no = 2.0210 at 532nm
 
  Sellmeier Equations (λ in um)
no2 = 3.77834+0.069736/(λ2-0.04724)-0.0108133×λ2
  ne2 = 4.59905+0.110534/(λ2-0.04813)-0.0122676×λ2
 
  Table 2:  Nd:YVO4 Properties (Doping atom 1.1%)
 

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