Broad phase-matching range from 410 nm to 2100 nm
Useful optical transmission from 190 nm to 3500 nm
Large effective second-harmonic-generation (SHG) coefficient
about 6 times greater than that of KDP crystal;
High damage threshold of 10 GW/cm2 for 100ps pulse-width
at 1064nm;
High optical homogeneity with dn » 10^-6/cm;
Wide temperature-bandwidth of about 55°C.
Low thermo-optic coefficient
BBO
is grown with the flux method. It is a negative uniaxial
crystal, with ordinary refractive-index (no)
larger than extraordinary refractive-index (ne).
Structural and
Physical Properties:
| Crystal
Structure: |
Trigonal,
space group R3c |
| Cell
Parameters: |
a =
b = 12.532
Å, c
= 12.717Å, Z
= 6 |
| Melting
point: |
1095+
5°C
|
| Transition
temperature: |
925+
5°C
|
| Optical
homogeneity: |
dn
»
10-6/cm |
| Mohs
hardness: |
4
|
| Density:
|
3.85
g/cm3 |
| Absorption
coefficient: |
<
0.1%/cm (at 1064nm) |
| Specific
heat: |
1.91J/cm3xK
|
| Hygroscopic
susceptibility: |
Low
|
| Thermal
expansion coefficients: |
a,
4 x 10-6/K; c, 36 x 10-6/K
|
| Thermal
conductivity: |
^c,
1.2 W/m/K;
//c, 1.6 W/m/K |
Linear Optical
Properties:
| Transparency
range: |
189-3500
nm |
|
Sellmeier
equations: (l in
mm)
|
no2=2.7359+0.01878/(l2-0.01822)-0.01354l2
ne2=2.3753+0.01224/(l2-0.01667)-0.01516l2
|
| Refractive
indices:
at
1064 nm
at
532 nm
at
266 nm
|
ne
= 1.5425, no = 1.6551
ne
= 1.5555, no = 1.6749
ne
= 1.6146, no = 1.7571 |
| Therm-optic
coefficients: |
dno/dT
= -9.3 x 10-6/¡ãC
dne/dT = -16.6 x 10-6/¡ãC
|
Nonlinear Optical
Properties:
| Phase-matchable
output wavelengths: |
189
- 1750 nm |
|
NLO
coefficients: |
d11
= 5.8 x d36(KDP)
d31 = 0.05 x d11
d22 < 0.05 x d11
|
| Effective
nonlinearity expressions |
dooe=
d31 sinq +(d11
cos3f -
d22 sin3f) cosq
deoe= (d11 sin3f +
d22 cos3f) cos2q
|
| Electro-optic
coefficients: |
g11 =
2.7 pm/V, g22, g31 <
0.1g11
|
| Half-wave
voltage: |
48
KV (at 1064 nm) |
| Damage
threshold:
at
1064nm
at
532nm |
5 GW/cm2 (10 ns); 10 GW/cm2
(1.3 ns)
1 GW/cm2 (10 ns); 7 GW/cm2
(250 ps)
|
Application
BBO is of particular importance in the visible
and far UV. A wide variety of phase-matching applications
are possible, including the following:
Second, third, fourth and fifth harmonic generation
of Nd doping lasers;
Second harmonic generation to generate wavelengths
as short as 204.8 nm
Shorter wavelengths (193nm) can be generated by sum
frequency mixing
Frequency-doubling, -tripling and -mixing of Dye lasers;
Second, third and fourth harmonic generation of Ti:Sapphire
lasers;
Optical parametric amplifier (OPA) and optical
parametric oscillators (OPO);
Frequency-doubling of Argon ion, Cu-vapor and Ruby
lasers.
Transverse field Pockel cells made from BBO useful
when high average powers or short wavelengths used.
SHG and SFG
Because of a small acceptance angle and large
walk-off, good laser beam quality (small divergence, good
mode condition, etc.) is the key for BBO to obtain high
conversion efficiency. Tight focus of laser beam is not
recommended. BBO is the only NLO material which can be used
to produce the fifth harmonic generation (5HG) of Nd:YAG
lasers at 213 nm.
| Relevant
NLO properties for type I BBO crystal |
| |
SHG |
SHG |
SHG |
SHG |
| Effective
NLO Coefficient
(d36(KDP)) |
5.3 |
4.9 |
3.8 |
3.4 |
| Acceptance Angle (mrad-cm) |
1.0 |
0.5 |
0.3 |
0.2 |
| Walk-off Angle (°) |
3.2 |
4.1 |
4.9 |
5.5 |
Ultrafast Pulse
(Ti:sapphire) Laser
Frequency-doubling and -tripling of ultrashort-pulse
lasers are the applications in which
BBO shows superior properties to KDP and ADP crystals. As
thin as 0.02mm BBO for this purpose is available.. A laser
pulse as short as 10 fs can be efficiently frequency-doubled
with a thin BBO, in terms of both phase-velocity and group-velocity
matching.
BBO's OPO and
OPA
The OPO and OPA of BBO are powerful tools
for generating a widely tunable coherent radiation from
the UV to IR. The tuning angles of type I and type II BBO
OPO and OPA have been calculated, with the results shown
in folowing, respectively.
BBO’s Specifications
| Wavefront
distortion |
less
than l/8
@ 633nm |
| Dimension
tolerance |
(W
±
0.1mm) x (H ±
0.1mm) x (L + 0.2mm/-0.1mm) |
| Clear
aperture: |
>
90% central area |
| Flatness: |
l/8
@ 633nm |
| Scratch/Dig
code: |
10/5
to MIL-O-13830A |
| Parallelism: |
better
than 20 arc seconds |
| Perpendicularity: |
5
arc minutes |
| Angle tolerance: |
Dq < ± 0.3°, Df < ±0.3°
|
| Quality
Warranty Period: |
one
year under proper use |
Coatings :
1.P-Coating: The protective dielectric coating
protects the BBO polished surfaces from fogging due to ambient
moisture. The protective coating also reduces reflection
from the polished surface and improves transmission for
all wavelengths that are used.
2. Anti-reflective coatings (AR-coating):
Single-band, dual-band AR-coating and broad-band AR Coating
on BBO surface are available from CRYSTECH.
Note:
1. BBO has a low susceptibility to the moisture.
The user is advised to provide dry conditions for both the
use and preservation of BBO.
2. BBO is relatively soft and therefore requires
precautions to protect its polished surfaces.
3. When angle adjusting is necessary, keep
in mind that the acceptance angle of BBO is small.
Standard Product:
| Part
No. |
Dimension
|
Application
|
Coating
|
Type
|
| BBO1407
|
4x4x7mm
|
S(T)HG@1064nm
|
AR
coating |
I
or II |
| BBO1410 |
4x4x10mm
|
S(T)HG@1064nm
|
AR
coating |
I
or II |
| BBO1847 |
8x4x7mm
|
SHG
for Dye laser |
P-coating
|
I
|
| BBO1551 |
5x5x1mm
|
S(T)HG
@800nm |
P-Coating
|
I
|
| BBO1550 |
5x5x0.1mm
|
S(T)HG
@800nm |
P-coating
|
I
|
| BBO1865 |
8x6x15mm
|
OPO
|
AR/AR
Coating |
I
or II |
