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THATSHIGH's LBO (Lithium triborate or LiB3O5) is grown with an improved flux method. LBO is an orthorhombic cyrstal and belongs to the point group mm2. It is built up of a continuous network of B3O7 groups with lithium cations locating in the interstices. The compact network of B3O7 groups makes the LBO crystal almost free of inclusion. Now, THATSHIGH provides high quality LBO crystals for many applications.
LBO Features:
1.Broad transparency range from 160nm to 2600nm (SHG range from 550nm to 2600nm).
2.Type I and type II non-critical phase-matching (NCPM) over a wide wavelength range.
3.Relatively large effective SHG coefficient (about three times larger than that of KDP).
4.High damage threshold (18.9 GW/cm2 for a 1.3ns laser at 1054nm).
5.Wide acceptance angle and small walk-off.
6.High optical quality (homogeneity Dn≈ 10-6/cm) and free of inclusion.
LBO Applications:
1.High power Nd:YAG and Nd:YLF lasers for R&D and military applications.
2.Ti:Sapphire, Alexandrite and Cr:LiSAF lasers.
3.Medical and industrial Nd:YAG lasers.
4.Diode laser pumped Nd:YVO4, Nd:YAG and Nd:YLF lasers.
5.Frequency-tripling (THG) of Nd:YAG and Nd:YLF lasers.
6.Optical parametric amplifiers (OPA) and oscillators (OPO) pumped by Excimer lasers and harmonics of Nd:YAG lasers.
7.Frequency doubling (SHG) and tripling (THG) of high power Nd:YAP laser at 1340nm.
1. Strict quality control.
2. Large crystal with size up to 10x10x30 mm3 and maximum length of 35 mm.
3. AR-coatings, mounts and repolishing services.
4. Fast delivery, in-stock crystals in a large quantity.
Chemical and Structural Properties of LBO Crystal

Crystal Structure

Orthorhombic, Space group Pna21, Point group mm2

Lattice Parameter

a=8.4473Å, b=7.3788Å, c=5.1395Å

Melting Point

About 834℃

Mohs Hardness




Thermal Conductivity


Thermal Expansion Coefficient

αx=10.8×10-5/K, αy= -8.8×10-5/K, αz=3.4×10-5/K

Optical and Nonlinear Optical Properties of LBO Crystal

Transparency Range


SHG Phase Matchable Range

551nm-2600nm (Type I) 790nm-2150nm (Type II)

Therm-optic Coefficient
[°C, λ in μm]

dnx/dT=-9.3×10-6; dny/dT=-13.6×10-6; dnz/dT=(-6.3-2.1l) ×10-6

Absorption Coefficient

< 0.1%/cm @ 1064nm <0.3%/cm @ 532nm

Angle Acceptance

6.54 mrad·cm-1 (φ, Type I,1064 SHG)
15.27 mrad·cm-1 (q, Type II,1064 SHG)

Temperature Acceptance

4.7℃·cm-1 (Type I, 1064 SHG)
7.5℃·cm-1 (Type II,1064 SHG)

Spectral Acceptance

1.0nm·cm-1 (Type I, 1064 SHG)
1.3nm·cm-1 (Type II,1064 SHG)

Walk-off Angle

0.60° (Type I 1064 SHG)
0.12° (Type II 1064 SHG)

NLO Coefficient

deff(I)=d32cosφ (Type I in XY plane)
deff(I)=d31cos2θ+d32sin2θ (Type I in XZ plane)
deff(II)=d31cosθ (Type II in YZ plane)
deff(II)=d31cos2θ+d32sin2θ (Type II in XZ plane)

Non-vanished NLO Susceptibilities

d31=1.05 ± 0.09 pm/V d32= -0.98 ± 0.09 pm/V
d33=0.05 ± 0.006 pm/V

Sellmeier Equations [λ in μm]


Harmonic Generation
LBO is phase-matchable for SHG and THG of Nd:YAG and Nd:YLF lasers by using either type I or type II interaction. For SHG at room temperature, type I phase-matching can be reached and has maximum effective SHG coefficient in the principal XY and XZ planes in a wide wavelength range from 551 nm to about 3 μm. The optimum type II phase-matching falls in the principal YZ and XZ planes.


Type I SHG Tuning Curve of LBO          Type II SHG Tuning Curve of LBO

SHG conversion efficiencies of more than 70% for pulse and 30% for cw Nd:YAG lasers, and THG conversion effi-ciency of over 60% for pulse Nd:YAG laser have been observed respectively. The SHG conversion efficiency of LBO in an unstable resonator Nd:YAG laser vs the average power density in comparison with that of KTP is shown in right figure. 


1. More than 480 mW output at 395 nm is generated by frequency-doubling a 2W mode-locked Ti:Sapphire laser (<2ps, 82MHz). The wavelength range of 700 - 900 nm is covered by a 5x3x8 mm3 LBO crystal.
2. Over 60 W green output is obtained by SHG of a Q-switched Nd:YAG laser in a type II, 18 mm long LBO crystal.
3. The frequency-doubling of a Spectra-Physics TFR diode pumped Nd:YLF laser ( > 500 mJ @ 1047 nm, < 7 ns, 0-10 KHz) reaches over 40% conversion efficiency in a 9 mm LBO.
4. The VUV output at 187.7 nm is obtained by sum-frequency generation.
5. 2 mJ/pulse diffraction-limited beam at 355 nm is obtained by intracavity tripling a Q-switched Nd:YAG laser.
6. LBO is very promising for the generation of 266 nm from Nd:YAG, Nd:YVO4 laser because of its low absorption at 266 nm.
7. Due to its high damage threshold and small group velocity dispersion, LBO is an excellent crystal for SHG, THG and autocorrelators of ultrashort pulsed lasers including Ti:Sapphire, Cr:LiSrAlF and Cr:LiCaAlF lasers. THATSHIGH can provide LBO crystal as thin as 0.02 mm for 10 fs lasers. To select the best LBO crystal design for your ultrashort pulsed lasers, please consult THATSHIGH.
Non-Critical Phase-Matching
Non-Critical Phase-Matching (NCPM) of LBO is featured by no walk-off, very wide acceptance angle and maximum effective coefficient. It promotes LBO to work in its optimal condition. The SHG conversion efficiencies of more than 70% for pulse and 30% for cw Nd:YAG lasers have been obtained with good output stability and beam quality.


Type I and type II NCPM can be reached along x-axis (θ = 90o, φ= 0o) and z-axis ( θ= 0o,φ= 0o), respectively. As shown in the figure, NCPM SHG over a broad wavelength range from 900 nm to about 1700 nm was measured. The properties of NCPM SHG of Nd:YAG laser at 1.064μm are listed in following table.

Properties of type I NCPM SHG at1.064 mm

Properties of type I NCPM SHG at 1.064 mm

NCPM Temperature

148 oC

Acceptance Angle

52 mrad-cm1/2

Walk-off Angle


Temperature Bandwidth

4 oC -cm

Effective SHG Coefficient

2.69 d36(KDP)

THATSHIGH develops an assembly of stabilized oven and temperature controller for NCPM SHG of Nd:YAG, Nd:YLF and Nd:Glass lasers as well as NCPM OPO and OPA systems. The assembly can keep LBO crystal within ±0.1OC from room temperature to 200 OC. Please refer to page 64 for more information about oven and temperature controller. 


NCPM Temperature Tuning Curves of LBO         SHG of Nd:YLF Antares with BO

1. Over 10 W and highly stable green output @ 532 nm was obtained with NCPM LBO for frequency doubling of diode pumped Nd:YVO4 lasers. All solid state SLM, Q-switched green and UV lasers are available.
2. Over 100 W green output was achieved with type II LBO for frequency doubling of Q-switched Nd:YAG laser.
3. LBO can reach both temperature NCPM and spectral NCPM (very wide spectral bandwidth) at 1.3 mm.
LBO is an excellent NLO crystal for the widely tunable wavelength range and high power OPO and OPA. The type I and type II OPO and OPA pumped by SHG and THG of Nd:YAG laser and XeCl excimer laser at 308 nm have been reported. The figure shows the calculated OPO tuning curves of a type I LBO pumped by SHG, THG and 4HG of Nd:YAG laser in XY plane at room temperature, and also shows the calculated OPO tuning curves of a type II LBO pumped by SHG and THG of Nd:YAG laser in YZ and XZ planes.


Type I OPO Tuning Curves of LBO


Type II OPO Tuning Curves of LBO Pumped at 532 nm


Type II OPO Tuning Curves of LBO Pumped at 355 nm

1.By using 90O NCPM LBO, Spectra-Physics SPPO OPO synchronously pumped by femtosecond Ti:Sapphire laser generates < 130 fs pulse from 1.1 to 2600nm.
2.Type I OPA pumped at 355 nm with pump-to-signal energy conversion efficiency of 30% has been reported.
3.By using the NCPM technique, type I OPA pumped by SHG of Nd:YAG laser at 532 nm was also observed to cover a widely tunable range from 750 nm to 1800nm by temperature-tuning from 106.5C to 148.5C.
4.By using type II NCPM LBO as an optical parametric generator (OPG) and type I critical phase-matched BBO as an OPA, narrow linewidth (0.15 nm) and high pump-to-signal energy conversion efficiency (32.7%) were obtained when it is pumped by a 4.8 mJ, 30ps laser at 355nm. Wavelength tuning range from 482.6 to 415.9 nm is covered by increasing the temperature of LBO.

THATSHIGH provides the following AR-coatings:

1. Dual-band AR-coating of LBO for SHG of Nd:YAG lasers.
Low reflectance
( < 0.1% at 1064nm and < 0.25% at 532nm);
High damage threshold
( > 500 MW/cm2 at both wavelengths);
Long durability.
2. Broad Band AR-coating for frequency doubling Ti:Sapphire laser.
3. Other coatings are available upon request.


THATSHIGH Specifications for LBO Crystal

Dimension Tolerance

(W±0.1mm) × (H±0.1mm) × (L+0.2mm/-0.1mm)

Wavefront Distortion

<λ/8 @ 633nm

Clear Aperture

90% of central area


λ/8 @ 633nm

Surface Quality [S/D]



< 10"


≤ 10'

Angle Tolerance

Dq < ±0.5°; Df < ±0.5°

Damage Threshold

3GW/cm2 for a TEM00 mode, 10 ns, 1 Hz laser @1064nm
1GW/cm2 for a CW, mode-locked laser @1064nm

Interior Quality

No visible scattering paths or centers [inspected by 50mW green laser]

THATSHIGH'S Warranty on LBO Specifications

Transmitting wavefront distortion

less than l/8 @ 633nm

Dimension tolerance

(W± 0.1 mm) x (H± 0.1 mm) x (L + 0.2 mm/-0.1 mm)

Clear aperture

central 80% diameter

No visible scattering paths or centers when inspected by a 30 mW green laser


l/8 @ 633nm

Surface Quality

10/5 Scratch/Dig to MIL-O-13830A


better than 20 arc seconds


15 arc minutes

Angle tolerance

Dq < ±0.5o, Df <± 0.5o

Damage threshokd:
15 GW/cm2 for a TEMoo mode, 1.3 ns, 1 Hz laser at 1.064 mm
1 GW/cm2 for a cw, mode-locked laser at 1064nm

Quality warranty period

one year under proper use

1. LBO has a very low susceptibility to moisture. Users are advised to provide dry conditions for both use and preservation of LBO.
2. Users are advised to cautiously protect polished surfaces of LBO.
3. THATSHIGH engineers can select and design the best crystal for you if parameters of your laser are provided, for example, energy per pulse, pulse width and repetition rate for a pulsed laser, power for a cw laser, laser beam diameter, mode condition, divergence, wavelength tuning range, etc.

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