INRAD Lithium Niobate
page 1 of 5
Lithium Niobate (LiNbO
3
)
PHYSICAL PROPERTIES
Chemical Formula
LiNbO
3
congruently melting
1
Crystal Symmetry and Class
trigonal, R3c
Point
Group
3m
Lattice Constants
2
a = 5.15052(6) Å
c = 13.86496(3) Å
Density
2
4.648(5)
g/cm
3
Moh's Hardness
5
Fracture Toughness
3
c-face
0.67 MPam
1/2
x-face
1.07 MPam
1/2
y-face
1.17 MPam
1/2
Elastic Compliance
4
at Constant Polarization (S
P
) and at Constant Field (S
E
) and Temperature
Dependence
5
( TPa)
-1
( TPa)-1
(10
-4
/
°
K)
S
P11
= 4.76
S
E11
= 5.78
(1/S
E11
)dS
E11
/dT=1.66
S
P12
= -0.50
S
E12
= - 1.01
(1/S
E12
)dS
E12
/dT=0.28
S
P13
= -1.20
S
E13
= -1.47
(1/S
E13
)dS
E13
/dT=1.94
S
P14
= 1.02
S
E14
= -1.02
(1/S
E14
)dS
E14
/dT=1.33
S
P33
= 4.19
S
E33
= 5.02
(1/S
E22
)dS
E22
/dT=1.60
S
P44
= 9.3
S
E44
= 17.0
(1/S
E44
)dS
E44
/dT=2.05
S
P66
= 10.5
S
E66
= 13.6
(1/S
E66
)dS
E66
/dT=1.43
Stiffness
4
at Constant Polarization (C
P
) and at Constant Field (C
E
) and Temperature Dependence
5
(GPa)
(GPa)
(10
-4
/
°
K)
C
P11
= 219
C
E11
= 203
(1/C
E11
)dC
E11
/dT=-1.74
C
P12
= 37
C
E12
= 53
(1/C
E12
)dC
E12
/dT=-2.52
C
P13
= 76
C
E13
= 75
(1/C
E13
)dC
E13
/dT=-1.59
C
P14
= -15
C
E14
= 9
(1/C
E14
)dC
E14
/dT=-2.14
C
P22
= 252
C
E22
= 245
(1/C
E22
)dC
E22
/dT=-1.53
C
P44
= 95
C
E44
= 60
(1/C
E44
)dC
E44
/dT=-2.04
C
P66
= 91
C
E66
= 75
(1/C
E66
)dC
E66
/dT=-1.43
INRAD Lithium Niobate
page 2 of 5
OPTICAL AND ELECTRO-OPTICAL PROPERTIES
Optical Symmetry
uniaxial negative
Optical Transmission
0.400
µ
m - 5.0
µ
m
Sellmeier Equation Constants
13
n =( A +B/(
λ
2
+C)+D
λ
2
)
1/2
;
λ
in microns
n
o
A=4.9048 B=0.11768 C= -0.0475
D= -0.027169
n
e
A=4.582 B=0.099169 C=-0.044432 D= -0.02195
Calculated Refractive Index Values
13
n
o
( 1.064
µ
m) = 2.2322 ; n
e
( 1.064
µ
m) = 2.1560
n
o
( 2.060
µ
m) = 2.1949 ; n
e
( 2.060
µ
m) = 2.1243
n
o
( 3.500
µ
m) = 2.1405 ; n
e
( 3.500
µ
m) = 2.0788
Photoelastic Strain Coefficients at Constant Field
11
ρ
11
= -0.026
ρ
31
= 0.17
ρ
12
= 0.08
ρ
33
= 0.07
ρ
13
= 0.13
ρ
41
= -0.151
ρ
14
= -0.08
ρ
44
= 0.146
Temperature Variation of Refractive Index
13
for
λ
= 1.0 µm – 4.0 µm
dn
o
/dT = 3.3 x 10
-6
/
°
C
dn
e
/dT = 37 x 10
-6
/
°
C
Nonlinear d Coefficients
12,20
d
22
= 2.4 pm/V
d
31
= -4.52 pm/V
d
33
= 31.5 pm/V
Effective Nonlinear Optical Coefficient
d
eff
= d
31
sin
θ
- d
22
cos
θ
sin 3
Φ
Electro Optic Coefficients @ 0.633
µ
m
23
r
13
T
= 10 pm/V
r
13
S
= 8.6 pm/V
r
22
T
= 6.8 pm/V
r
22
S
= 3.4 pm/V
r
33
T
= 32.2 pm/V
r
33
S
= 30.8 pm/V
r
51
T
= 32 pm/V
r
51
S
= 28 pm/V
Variation of Electro Optic Coefficient r
22
with Wavelength
22
And Calculated Half-wave Voltage For 9mmx9mmx25mm Q-Switch
V
1/4
=
λ
d / ( 4 n
3
l r
22
)
r
22
T
V
1/4
1.064
µ
m = 5.6 pm/V
1.55 kVolts
1.318
µ
m = 5.4 pm/V
2.02 kVolts
1.55
µ
m = 5.3 pm/V
2.44 kVolts
2.10
µ
m = 5.2 pm/V
3.45 kVolts
2.79
µ
m = 5.1 pm/V
4.78 kVolts
2.94
µ
m = 5.1 pm/V
5.08 kVolts
Damage Threshold
2
3 J/cm
2
@ 10 nsec
INRAD Lithium Niobate
page 3 of 5
THERMAL AND ELECTRICAL PROPERTIES
Melting Point
7
1240
°
C
Curie Temperature
8
1145
°
C
Thermal Conductivity
9
4. W/m
°
K
Thermal diffusivity
6
9 x 10
-7
m
2
/sec
Specific Heat
9
0.633 J/g
°
K
Thermal Expansion
10
α
a
= 14.1 x 10
-6
/
°
K
α
c
= 4.1 x 10
-6
/
°
K
Resistivity
14
2 x 10
10
Ω
- cm @ 200
°
C
Dielectric Constants
16
K
11
S
= 43
K
11
T
= 78
K
33
S
= 28
K
33
T
= 32
Loss tangent
15
@400
°
C
x-axis Tan
δ
=0.0006
y-axis Tan
δ
=0.001
Typical Polish Specifications
Wavefront Distortion:
λ
/ 8 @ 633 nm
Flatness:
λ
/ 10 @ 633 nm
Parallelism:
1 arcseconds
Scratch - Dig:
10 - 5
INRAD Lithium Niobate
page 4 of 5
Description
Lithium niobate is a ferroelectric material suitable for a variety of applications. Its versatility
is made possible by the excellent electro-optic, nonlinear, and piezoelectric properties of the
intrinsic material. It is one of the most thoroughly characterized electro-optic materials, and
crystal growing techniques consistently produce large crystals of high perfection.
Applications that utilize the large electro-optic coefficients of lithium niobate are optical
modulation and Q-switching of infrared wavelengths. Because the crystal is
nonhygroscopic and has a low half-wave voltage, it is often the material of choice for Q-
switches in military applications. The crystal can be operated in a Q-switch configuration
with zero residual birefringence and with an electric field that is transverse to the direction of
light propagation. Because piezoelectric ringing can be severe, piezoelectrically damped
designs can be very useful. The damage threshold of the intrinsic material at 1.06 microns
with a 10 nsec pulse is approximately 3 J/cm
2
. With appropriate AR coatings, a surface
damage threshold of 300-500 MW/cm
2
can be achieved for the same conditions.
Applications that use the large nonlinear d coefficient of LiNbO
3
include optical parametric
oscillaton, difference frequency mixing to generate tunable infrared wavelengths, and
second harmonic generation. With a broad spectral transmission, which ranges from 0.4
µ
m to 5.0
µ
m with an OH
-
absorption at 2.87
µ
m, a large negative birefringence, and a large
nonlinear coefficient, phasematching is an effective way to generate tunable wavelengths
over a broad wavelength range.
Lithium niobate is particularly effective for second harmonic generation of low power laser
diodes in the 1.3 to 1.55
µ
m range.
For infrared generation by difference frequency mixing, the peak power limit is considerably
lower than for 1.064
µ
m, being about 40 MW/cm
2
. Efficiencies for difference frequency
mixing generally are smaller than shg efficicncies with KDP or BBO, which is due to the
lower peak powers that can be tolerated by the crystal and the fact that the longer
wavelength photons that are generated in the process are less energetic. Typical powers
for 10 nanosecond long pulses with 5 mm diameter beams are 30 mJ/pulse of 0.640
µ
m
minus 40 mJ/pulse of 1.064
µ
m to produce 2.5 mJ/pulse at 1.54
µ
m, and 32 mJ/pulse of
0.532
µ
m minus 32 mJ/pulse of 0.640
µ
m to produce 0.25 mJ/pulse at 3.42
µ
m.
INRAD offers lithium niobate in a variety of configurations. Standard cuts are available as
OPO crystals, Q-switches, difference frequency mixing crystals, autocorrelation crystals,
and optical waveguide wafers.
Please consult an INRAD sales engineer for assistance in crystal selection and packaging.
At INRAD, all crystal growth, orientation, fabrication, polishing, and testing of LiNbO
3
is done
at one site so that you are assured of complete traceability and satisfaction with every
crystal that you purchase.
INRAD Lithium Niobate
page 5 of 5
References
1.
R.L.Byer, J.F.Young, and R.S.Feigelson, J.Appl.Phys.
41
(6), 2320 (1970).
2.
S.C.Abrahams and P.Marsh, Acta.Crystallog.Sec.B,
42
, 61 (1986).
3.
J.C.Lambropoulos and T.Fang, Dept. of Mech.Eng.& Center for Optics Manufacturing, Univ. of Rochester.
4.
A.W.Warner, M.Onoe, and G.A.Coquin, J.Acoust.Soc.Am.
42
(6), 1223 (1967).
5.
R.T.Smith and F.S.Welsh, J.Appl.Phys.
42
(6), 2219 (1971).
6.
T.H.Lin, D.Edwards, R.E.Reedy, K.Das, W.McGinnis, and S.H.Lee, Ferroelectrics
77
, 153 (1988).
7.
J.R.Carruthers, G.E.Peterson, M.Grasso, and P.M.Bridenbaugh, J.Appl.Phys.
42
, 1846, (1971).
8.
J.C.Brice, The Properties of Lithium Niobate, EMIS Datareviews Series No.5, The Institute of Electrical
Engineers (1989).
9.
V.V.Zhdanova, V.P.Klyuev, V.V.Lemanov, I.A.Smirnov, and V.V.Tikhonov, Sov.Phys.-Solid State (USA)
10
,(6)
1360 (1968).
10
D.Taylor, The Properties of Lithium Niobate, EMIS Datareviews Series No.5, The Institute of Electrical
Engineers (1989).
11.
L.P.Avakyants, D.F.Kiselev, and N.N.Shchitov, Sov.Phys.-Solid State
18
, 899 (1976).
12.
R.C.Eckardt, H.Masuda, Y.X.Fan, and R.L.Byer IEEE J.Quant.Electron.
26
(5), 922 (1990).
13.
S.D.Smith, H.D.Riccius, and R.P.Edwin, Opt.Comm.,
17
, 332 (1976) and
20
, 188 (1977).
14.
A.V.Blistanov, Sov. Phys.-Cryst.,
6
, 688 (1983).
15. K.Nassau,
et.al,
J.Phys.Chem.Solids,
27
, 989 (1966).
16.
I.P.Kaminow and E.H.Turner, Appl. Opt., 5, 1612 (1966).
17. E.H.Turner,
Appl.Phys.Lett.,
8
, 303 (1966).
18.
J.D.Zook, D.Chen, and G.N.Otto, Appl.Phys.Lett.,
11
, 159 (1967).
19.
P.V.Lenzo, E.G.Specer, and K.Nassau, Opt.Soc.Am.,
56
, 633 (1966).
20.
R.C.Miller and A.Savage, Appl.Phys.Lett.,
9
, 167 (1966).
21.
Miller, Norland, and Bridenbaugh, J.Appl.Phys.,
42
, 4145 (1971).
22. INRAD
data.
23.
I.P.Kaminow and E.H.Turner, “Handbook of Lasers” (R.J.Pressley, ed.), 447-459. Chemical Rubber Co.,
Cleveland, Ohio, 1971.