Lithium Niobate Crystal (LiNbO3)
LiNbO3
Crystal is
widely used as frequency doublers for wavelength > 1mm and optical parametric oscillators (OPOs)
pumped at 1064 nm as well as quasi-phase-matched (QPM) devices.
Due to its large Electro-Optic (E-O) and Acousto-Optic (A-O)
coefficients, LiNbO3 crystal is the
most commonly used material for Pockel Cells, Q-switches
and phase modulators, waveguide substrate, and surface acoustic
wave (SAW) wafers, etc.
AZURE provides high quality and large size LiNbO3 crystals for laser frequency doublers, OPOs
and quasi-phase-matched doublers, as well as waveguide substrate
and SAW wafers. High quality LiNbO3 components with aperture of (2 - 15) x (2 -
15) mm2 and length up to 50 mm for frequency doublers and
optical parametric oscillators (OPOs), 50x50x1 mm3 or Dia.
3" x 1 mm LiNbO3 substrate for waveguide
optics, and Dia. 3" SAW wafers are available with high volume
and at low price.
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1. Basic Properties
Crystal
Structure |
Trigonal,
space group R3c |
Cell
Parameters |
a
= 0.515, c = 13.863, Z = 6 |
Melting
Point |
1255±5oC |
Curie
Point |
1140±5oC |
Mohs
Hardness |
5
|
Density |
4.64
g/cm3 |
Absorption
Coefficient |
~
0.1%/cm @ 1064 nm |
Solubility: |
insoluble
in H2O |
Relative
Dielectric Constant |
eT11/e0: 85
eT33/e0: 29.5 |
Thermal Expansion Coefficients( @ 25oC) |
||a, 2.0 x 10-6/K ||c, 2.2 x 10-6/K |
Thermal
Conductivity |
38
W /m /K @ 25oC |
2. Linear Optical Properties
Transparency Range
420-5200nm |
LiNbO3 Transparency Curve |
Refractive
Indices
ne=2.146, no = 2.220 @ 1300 nm
ne= 2.156, no = 2.232 @ 1064 nm
ne= 2.203, no = 2.286 @ 632.8nm
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Optical
Homogeneity ~ 5 x 10-5 /cm |
Sellmeier Equations (l in mm):
n2o (l) = 4.9048+0.11768/(l2 - 0.04750) - 0.027169l2
n2e (l) = 4.5820+0.099169/(l2 - 0.04443) - 0.021950l2
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3. Nonlinear Optical Properties
NLO
Coefficients |
d33 = 34.4 pm/V
d31 = d15 = 5.95 pm/V
d22 = 3.07 pm/V |
Efficiency
NLO Coefficients |
deff =5.7 pm/V or ~14.6 x d36
(KDP) for frequency doubling 1300 nm;
deff =5.3 pm/V or ~13.6 x d36 (KDP)
for OPO pumped at 1064 nm;
deff =17.6 pm/V or ~45 x d36 (KDP) for quasi-phase-matched structure. |
Electro-Optic Coefficients |
gT33 = 32 pm/V, gS33 = 31 pm/V,
gT31 =10 pm/V, gS31=8.6
pm/V,
gT22 =
6.8 pm/V, gS22= 3.4 pm/V, |
Half-Wave
Voltage, DC
Electrical field||z, light ^z:
Electrical field||x
or y, light||z: |
3.03
KV
4.02 KV |
Damage
Threshold |
100
MW/cm2 (10 ns, 1064nm) |
4. Standard Specifications of laser grade
LiNbO3 crystals:
Transmitted wavefront distortion |
better
than l/4 @ 633nm
|
Dimension
tolerance |
(W±0.1mm) x (H±0.1mm) x (L±0.2mm) |
Clear
aperture |
over
90% central diameter |
Flatness |
l/8 @ 633nm
|
Surface
quality |
20
/10 Scratch/Dig |
Parallelism |
better
than 20 arc sec |
Perpendicularity |
5
arc min |
Angle
tolerance |
Dq < 0.5o, Df < 0.5o |
AR-coating |
dual
wave band AR coating at 1064/532 nm on both surfaces, with
R < 0.2% at 1064 nm and R < 0.5% at 0.532 nm per surface
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Compared with LiNbO3
crystal, MgO:LiNbO3 crystal exhibits its
particular advantages for NCPM frequency doubling (SHG) of
Nd:Lasers, mixing (SFG) and optical parametric oscillators
(OPOs). The SHG efficiencies
of over 65% for pulsed Nd:YAG lasers and 45% for cw Nd:YAG
lasers have been achieved in MgO:LiNbO3 crystals, respectively. MgO:LiNbO3 is also a good crystal for optical parametric
oscillators (OPOs) and amplifiers (OPAs), quasi-phase-matched
doublers and integrated waveguide.
MgO:LiNbO3 has similar effective nonlinear coefficients
to pure LiNbO3. Its Sellmeier equations
(for MgO dopant 7 mol%) are:
n2o (l) = 4.8762+0.11554/(l2 - 0.04674) - 0.033119 x l2 (l in um)
n2o (l) =
4.5469+0.094779/(l2 - 0.04439) - 0.026721 x l2
AZURE provides
high quality MgO:LiNbO3 crystals for various
nonlinear optics (NLO) and E-O applications. The typical size
of MgO:LiNbO3 crystals is (3 - 10) x (3
- 10) x (10 - 30) mm3 for OPOs & OPAs and frequency doubling
& mixing, and 20x20x1 mm3 for waveguide substrates. Other specs. and AR-coatings
for MgO:LiNbO3 are available upon request. |
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