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Good optical and
electrical properties, large size and relative low price make Lithium
Niobate (LiNbO3) be one of the most important crystals in
the field of optics and electronics. It is widely used in the laser
and electronic industry for the following applications:
laser components,
wafers for surface acoustic wave devices,
wafers for integrated optics applications
and doped LiNbO3 crystals for
nonlinear optics (MgO:LiNbO3,
ZnO: LiNbO3),
photo-refractive effects
devices devices ( (Fe:LiNbO3),
etc. Please refer to the following background data and technical
information for versatile applications.
I. Pure Lithium Niobate
(LiNbO3)
· Applications for frequency
doubler, OPO and quasi-phase-matched doubler
Due to its specific properties shown as following,
LiNbO3 is commonly used as not only frequency doubler
(wavelength > 1 m m) but optical parameter oscillator (OPO) pumped at
1.064 m m, as well quasi-phase-matched (QPM) doubler. Beijing
Gospel OptoTech Co. (GOT) supplies laser-grade LiNbO3
devices of (2-18) x (2-18) mm2 aperture and up to 50 mm
length for frequency doubler and optical parameter oscillator, with
high quality, large quantity and cheap price.
Basic, Optical and NLO Properties
Density : 4.64g/cm3
Crystal Structure : Trigonal, 3m-point group
Lattice Parameters
: a=b=0.515A, c=13.863A, Z=6
Mohs Hardness : » 5
Melting Point :
1250 ± 5° C
Curie Temperature :
1160 ± 5° C
Transmission Range
: 0.4 m m ~ 4.5 m m
Optical Homogeneity : D n
< 5x10-5/cm
Absorption
Coefficient : a 〜 0.1%/cm @1.064 m m
Thermal
Conductivity : 38W/m/° C at 25° C
Thermal Expansion
Coefficient :
a 1=a 2=2x10-6/°
C, a 3=2.2x10-6/° C at 25° C
Relative Dielectric
Constant : e 11T/e 0=85, e 33T/e
0=29.5
Refractive Indexes
:
no=2.220, ne=2.146
(@ 1.3 m m)
no=2.322, ne=2.156
(@ 1.064 m m)
no=2.286, ne=2.203
(@ 0.633 m m)
Sellmeier Equations
:
no2=4.9048+0.11768/(l
2-0.0475)-0.027169l 2(l
in m m)
ne2=4.582+0.099169/(l
2-0.04443)-0.02195l 2
NLO Coefficients :
deff=13.6d36(KDP)
- OPO at1.064 m m
deff=14.6d36(KDP)
- SHG at1.3 m m
deff=45.0d36(KDP)
- QPM
Damage Threshold
: > 250 KW/cm2 @1.064 m m (10 ns)
· Applications for Surface Acoustic Wave (SAW)
Devices
LiNbO3 single crystal is also commonly used
as an excellent material for surface acoustic wave (SAW) devices (such
as filters, oscillators and resonators) and ultrasonic transducer due
to its considerably high electro-mechanical coupling factor, low
acoustic transmission loss, stable physical and chemical properties.
GOT can supply large quantities of LiNbO3
boules, as-cut or finished f 3" wafers available up to 5,000〜8,000
pieces per month with good quality and very low price. Please find the
following basic specifications for LiNbO3 SAW wafer.
Specifications for LiNbO3 SAW Wafers
Standard Size : (f 3" ± 0.01") x (0.51 ± 0.05)mm
Orientation :
(1) 127.86° Y-cut; (2) YZ-cut; (3)
41° or 64° Y-cut
Surface Finish :one
surface mirror polished to Ra less than 10 A, reverse surface fine
ground
SAW Velocity : 3485
m/c (Y-cut), 3970 m/s (127.86° Y-cut)
Electromechanical
Coupling Factor : K31=0.023, Z00Kt=0.17
Temperature
Coefficient of Delay (TCD) :
78X10-6/° C (127.86° Y-cut)
Temperature
Coefficient of Velocity (TCV):-60X10-6/° C (127.86° Y-cut)
· Applications for Q-switch Elements
LiNbO3 is also extensively used as
electro-optic modulator and Q-switch for Nd:YAG, Nd:YLF and
Ti:Sapphire lasers as well as modulator for fiber optics, etc. The
transverse modulation is mostly employed for LiNbO3. If a
LiNbO3 crystal is used as Q-switch crystal with
specifications listed as the following, the light propagates in Z-axis
and electric field applies to X-axis, the refractive retardation will
be G =p Lno3g 22V/l d. MgO:LiNbO3
and ZnO:LiNbO3 crystals have similar electro-optic
properties to LiNbO3 but with higher damage threshold.
Specifications for LiNbO3 Q-Switch
Elements
Standard Dimension :
9x9x25 or 10x10x20mm3
(other sizes also available)
Dimension Tolerance
:
± 0.1mm (X & Y-axis); ±
0.3mm (Z-axis)
Orientation Accuracy
: < 10' (X & Y-axis); < 5' (Z-axis)
Wavefront Distortion
: < l /4 @633nm
Scratch/Dig Code :
10/5 to MIL-O-13830A
Parallelism : < 10"
Flatness : l /8
@632.8nm
Chamfer : < 0.5 mm
at 45° ± 5°
AR-Coating : R <
0.2% @1064nm
Electrodes : Gold or
Cr electrode on X-faces
Extinction Ratio : >
400:1 @633nm, (f 6mm beam)
Electro-Optic
Coefficients :
g 33=32pm/V, g 31=10pm/V,
g 22=6.8pm/V (low frequency)
g 33 =31pm/V, g 31=8.6pm/V,g
22=3.4pm/V (high frequency)
· Applications for Waveguide Substrates
For electro-optic waveguide applications, the mostly
used inorganic substrate is LiNbO3 crystal.
Specifications for LiNbO3 Waveguide
Substrates
Standard Dimension :
(1) 50x50x1 mm3 for
X-cut, Y-cut, or Z-cut
(2) f 3"x1 mm3 for
Y-cut or Z-cut
Tolerance of
Orientation : < 10'
Surface Finish : one
surface polished to better than l /2 (with mount) and free from
surface defects while observed by a 50X microscope, the other face
fine ground
II. Magnesium Oxide Doped Lithium Niobate
(MgO:LiNbO3)
MgO:LiNbO3
crystal has the advantages such as high damage threshold (over
5 GW/cm2 @1064nm, 12ns), noncritical phase matching (NCPM)
at room temperature, broad transparent range, excellent E-O and
NLO properties, good mechanical and chemical properties compared
with pure LiNbO3. So it is widely used for high power
frequency doubling(SHG), mixing(SFG) and optical parameter
oscillator(OPO).
MgO:LiNbO3
has similar effective nonlinear coefficients as pure LiNbO3.
Its Sellmeier equations(7 mol% MgO doping) are:
no2
= 4.8762+0.115540/(l 2-0.04674)-0.033119l 2
ne2 =
4.5469+0.094779/(l 2-0.04439)-0.026721l 2
Angle tuned phase matchable SHG of Nd:YAG laser (1.064
m m) and NCPM SHG of laser lasers (1.053 m m) of MgO:LiNbO3
(high MgO doping) can be achieved at room temperature. Over 45% and
60% of SHG efficient are obtained in pulsed and cw Nd:YAG lasers
respectively. MgO:LiNbO3 is also a good crystal for high
power quasi-phase-matched waveguide structure for doubler, optical
parametric amplifier (OPA) and oscillator (OPO).
The typical sizes of MgO:LiNbO3 crystals
provided by GOT are 5x5x(20-30) mm3 for OPO
and frequency doubler, (20-25)x(20-25)x1 mm3 or f 40x1 mm3
for waveguide substrates. Other sizes and AR or HR-coatings are
available according to customers' requirements.
III. Zinc Oxide Doped Lithium
Niobate (ZnO:LiNbO3)
ZnO:LiNbO3 crystal has the advantages as
MgO:LiNbO3, high damage threshold, noncritical phase
matching (NCPM) at room temperature, good mechanical and chemical
properties. Moreover it has better optical homogeneity than MgO:LiNbO3.
So it is another excellent candidate for high power frequency doubler,
OPO and quasi-phase-matched waveguide structure for doubler.
IV.Neodymium and Magnesium
Oxide Doped Lithium Niobate
(Nd:MgO:LiNbO3)
Nd:MgO:LiNbO3 is a self-frequency doubling
laser crystal, which combines the excellent laser properties of the Nd3+
ion with the electro-optical and NLO properties of LiNbO3.
Furthermore, it also remains the advantage of high damage threshold of
MgO:LiNbO3. These permit Nd:MgO:LiNbO3 crystal
to be designed of miniature green lasers and other miniature muti-functional
devices, including self-frequency-doubled lasers, self-modulated and
self-Q-switch lasers, and waveguide devices.
Nd:MgO:LiNbO3 crystals with different Nd3+
and MgO doped concentrations based on customers' specific requirements
could be supplied by GOT.
V. Iron Doped Lithium Niobate
(Fe:LiNbO3)
Fe:LiNbO3 is one kind of excellent
photorefractive crystal with high electro-optic coefficients, high
photorefractive sensitivity and diffraction efficiency without applied
electric field. Therefore, Fe:LiNbO3 crystal will find the
niche applications in phase conjugation and holographic recording.
High quality Fe:LiNbO3 crystal, with size as large as 3"
(Diameter) and iron doped concentrations from 0.01 to 0.1 atm%, can be
supplied by GOT. Special fabrications are also available
upon request. |
