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Newlight's LBO features
 Very
broad transparency range from 160nm to 2600nm
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High optical homogeneity (δn ~ 10-6/cm)
and free of defects |
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Moderate effective SHG coefficient (about three times that of KDP) |
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High damage threshold (18.9 GW/cm2
for a 1.3ns Nd laser ) |
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Wide acceptance angle and small angular walkoff |
Both Type I and Type II non-critical phase matching (NCPM) in a wide
wavelength
range is possible. |
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Spectral NCPM near 1300nm |
LBO is a negative biaxial
crystal, with the dielectric axes X, Y, and Z (nz>ny>nx)
parallel to the crystallographic axes a, c, and b, respectively.
Structural and Physical Properties
|
Crystal Structure |
Orthorhombic, Space group Pna21, Point group mm2 |
|
Cell Parameters |
a=8.4473Å, b=7.3788Å, c=5.1395Å, Z=2 |
|
Melting Point |
~834°C |
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Mohs Hardness |
6 |
|
Density |
2.47 g/cm3
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Hygroscopic Susceptibility |
Low |
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Thermal Expansion Coefficients
|
αx=10.8x10-5/K,αy=
-8.8x10-5/K,αz=3.4x10-5/K |
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Thermal Conductivity |
3.5W/M/K |
Linear Optical Properties
| Transparency Range |
160 - 2600nm |
Thermo-optic Coefficient
(1/°C,
λ in µm) |
dnx/dT =
(-3.76λ+2.30)
x 10-6
dny/dT = (6.01λ-19.40)
x 10-6
dnz/dT = (1.50λ-9.70)
x 10-6 |
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Optical Homogeneity |
δn ~10-6/cm
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Bulk Absorption Coefficient |
<
100ppm/cm at 1064nm, < 150ppm/cm at 532 nm |
Sellmeier Equations
(λ in µm) |
nx2=2.454140+0.011249/(λ2-0.011350)-0.014591λ2-6.60x10-5λ4
ny2=2.539070+0.012711/(λ2-0.012523)-0.018540λ2+2.00x10-4λ4
nz2=2.586179+0.013099/(λ2-0.011893)-0.017968λ2-2.26x10-4λ4 |
Refractive
Indices:
@ 1064 nm
@ 532 nm
@ 266 nm |
nx = 1.5656, ny = 1.5905, nz=1.6055
nx = 1.5785, ny = 1.6065, nz=1.6212
nx = 1.5973, ny = 1.6286, nz=1.6444 |
Nonlinear Optical Properties
|
SHG Phase Matchable Range |
551 ~ 2600nm (Type I); 790-2150nm (Type II) |
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NLO Coefficients |
d31=1.05 ± 0.09 pm/V
d32= -0.98 ± 0.09 pm/V
d33=0.05 ± 0.006 pm/V |
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Effective Nonlinearity Coefficients |
dooe=d32cosφ(in XY plane)
deeo=d31cos2θ+d32sin2θ
(in XZ plane)
doeo=d31cosθ(in
YZ plane)
deoe=d31cos2θ+d32sin2θ
(in XZ plane) |
Damage Threshold (Bulk)
@ 1064nm
@ 532nm |
9GW/cm2 (9 ns); 19 GW/cm2
(1.3 ns)
2.2 GW/cm2 (10 ns); 45 GW/cm2
(100ps) |
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NCPM Temperature |
148oC for SHG@1064nm,
162oC for SHG@1053nm
172oC for SHG@1047nm |
Damage Threshold
LBO has the highest bulk damage threshold
among all known nonlinear optical crystals and is the crystal of choice
for high power second and third harmonic generations of Nd:YAG,
Nd:YLF, and Nd:YVO4 lasers.
Comparison of bulk damage threshold (@1064nm,
1.3ns)
| Crystal |
Energy Fluence (J/cm2) |
Power Density (GW/cm2) |
| KTP |
6.0 |
4.6 |
| KDP |
10.9 |
8.4 |
| BBO |
12.9 |
9.9 |
| LBO |
24.6 |
18.9 |
Application Examples
SHG, SFG for a broad range of wavelength: phase matching cutoff
wavelength: SHG-
554 nm, THG-794 nm, SFM-down to 160 nm |
SHG and THG for middle and high power Nd: lasers at 1064nm for
medical, industrial
and military applications |
| SHG for Ti:Sapphire, Alexandrite and Cr:LiSAF lasers |
| SHG and THG of high power Nd: lasers at 1342nm & 1319nm for red and
blue laser |
| SHG for the Nd: Lasers at 914nm & 946nm for blue laser. |
| The VUV output at 187.7 nm is obtained by sum-frequency generation. |
| NCPM SHG over a broad wavelength range from 900nm -1700nm was
measured. |
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Optical Parametric Amplifiers (OPA) and Oscillators (OPO)
application. |
SHG and THG at Room Temperature
LBO
is phase matchable for the SHG and THG of Nd:YAG and Nd:YLF lasers, using
either type I or type II interaction. For the SHG at room temperature,
type I phase matching can be reached and has the maximum effective SHG
coefficient in the principal XY and XZ planes in a wide wavelength range
from 551nm to about 3000nm. LBO is the first choice for making doubler or
tripler for lasers such as Nd:YAG where high power density, high
stability, and long time operation are required.
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SHG tuning curves of LBO |
NCPM temperature tuning curves of LBO |
More than 480mW output at 395nm is
generated by frequency doubling a 2W mode
-locked Ti:Sapphire laser (<2ps, 82MHz). The wavelength range of
700-900nm is
covered by a 5x3x8mm3 LBO crystal. |
Over 80W green output is obtained by SHG of a Q-switched Nd:YAG laser
in a Type
II phase matching 18mm long LBO crystal.
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The frequency doubling of a diode pumped Nd:YLF laser (>500mJ @
1047nm, <7ns,
1-10KHz) reaches a conversion efficiency over 40% in a 9mm long LBO crystal.
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The VUV output at 187.7 nm is obtained by sum-frequency generation in
LBO.
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2mJ/pulse diffraction-limited beam at 355nm is obtained by intracavity
frequency
tripling a Q-switched Nd:YAG laser. |
Non-Critical Phase-Matching at Raised Temperature
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Non-Critical Phase-Matching (NCPM) of LBO is featured by zero walk
-off, very wide
acceptance angle and maximized effective coefficient. Type I NCPM and Type II NCPM
are along x-axis
(θ=90°,
φ=0°) and z-axis (θ=0°,
φ=0°), respectively. |
|
Over 11W of average power at 532nm was obtained by extracavity SHG of
a 25W
Antares mode-locked Nd:YAG laser (76MHz, 80ps). |
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20W green output was generated by frequency doubling a multimode Q-switched
medical Nd:YAG laser.
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LBO can reach both temperature NCPM
and spectral NCPM (with a very wide spectral bandwidth) at 1300nm. This is
favorable to the SHG of very broadband or ultrafast pulses at ~ 1300nm.
Properties for type I NCPM SHG at 1064nm
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NCPM Temperature |
148°C |
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Acceptance Angle |
52 mrad-cm1/2 |
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Walk-off Angle |
0 |
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Temperature Bandwidth |
4°C-cm |
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Effective SHG Coefficient |
2.69 x d36(KDP) |
OPO and OPA with LBO
LBO is an excellent NLO crystal for
OPOs and OPAs with a widely tunable wavelength range and high powers. The
unique properties of type I and type II phase matching as well as the NCPM
leave a big room in the research and applications of LBO's OPO and OPA.
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A high overall conversion efficiency and 540-1030nm
tunable wavelength range
were obtained with OPO pumped at 355nm. |
Type I OPA pumped at 355nm with the pump-to-signal energy conversion
efficiency of 30% has been reported. |
Type II NCPM OPO pumped by a XeCl excimer laser at 308nm has achieved
16.5%
conversion efficiency, and moderate tunable wavelength ranges can be obtained
with different pumping sources and temperature tuning.
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By using the NCPM technique, type I OPA pumped by the SHG of a Nd:YAG
laser
at 532nm was also observed to cover a wide tunable range from 750nm to
1800nm
by temperature tuning from 106.5°C to 148.5°C.
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Using type II NCPM LBO as an optical parametric generator (OPG) and
type I
critical phase matched BBO as an OPA, a narrow linewidth (0.15nm) and
high
pump-to-signal energy conversion efficiency (32.7%) were obtained, when
pumped by a 4.8mJ,
30ps laser at 354.7nm. Wavelength tuning range from
482.6nm to 415.9nm was covered by increasing the temperature of LBO and
rotating BBO.
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