Lithium Triborate (LiB3O5 or LBO) is an excellent nonlinear optical crystal and it has the following features:
We can provide LBO crystals:
Table 1. Chemical and Structural properties
|Crystal Structure||Orthorhombic, Space group Pna21, Point group mm2|
|Lattice Parameter||a=8.4473Å, b=7.3788Å , c=5.1395Å , Z=2|
|Melting Point||About 834℃|
|Thermal Expansion Coefficient||ax=10.8x10-5/K, ay= -8.8x10-5/K, az=3.4x10-5/K|
Table 2. Optical and Nonlinear Optical Properties
|SHG Phase Matchable Range||551 ~ 2600nm (Type I) 790-2150nm (Type II)|
|Therm-optic Coefficient (°C, l in μm)||dnx/dT=-9.3X10-6 dny/dT=-13.6X10-6 dnz/dT=(-6.3-2.1l)X10-6|
|Absorption Coefficient||<0.1%/cm at 1064nm <0.3%/cm at 532nm|
|Angle Acceptance||6.54mrad-cm (φ, Type I,1064 SHG) 15.27mrad-cm (q, Type II,1064 SHG)|
|Temperature Acceptance||4.7°C-cm (Type I, 1064 SHG) 7.5°C-cm (Type II,1064 SHG)|
|Spectral Acceptance||1.0nm-cm (Type I, 1064 SHG) 1.3nm-cm (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)||nx2=2.454140+0.011249/(λ2-0.011350)-0.014591λ2-6.60x10-5λ4 ny2=2.539070+0.012711/(λ2-0.012523)-0.018540λ2+2.0x10-4λ4 nz2=2.586179+0.013099/(λ2-0.011893)-0.017968λ2-2.26x10-4λ4|
Figure 1. Transparency curve of LBO
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 (see Fig. 2) in a wide wavelength range from 551nm to about 2600nm. The optimum type II phase matching falls in principal YZ and XZ planes(see Fig 2).
Figure 2. Optimum matching
SHG conversion efficiencies of more than 70% for pulse and 30% for cw Nd:YAG lasers, and THG conversion efficiency over 60% for pulse Nd:YAG laser have been observed.
Table 3. Properties of type I NCPM SHG at 1064nm
Effective SHG Coefficient
AS shown in table 3, 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. 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.
As shown in Fig.3, type I and type II non-critical phase-matching can be reached along x-axis and z-axis at room temperature, respectively.
Figure 3.NCPM temperature tuning curves of LBO
LBO is an excellent NLO crystal for OPOs and OPAs with a widely tunable wavelength range and high powers. These OPO and OPA that are pumped by the SHG and THG of Nd:YAG laser and XeCl excimer laser at 308nm have been reported. 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. Fig.4 shows the calculated type I OPO tuning curves of LBO pumped by the SHG, THG and 4HG of Nd:YAG laser in XY plane at the room temperature. And Fig. 5 illustrates type II OPO tuning curves of LBO pumped by the SHG and THG of Nd:YAG laser in XZ plane.
Not only the ordinary non-critical phase matching (NCPM) for angular variation but also the noncritical phase matching for spectral variation (SNCPM) can be achieved in the LBO crystal. As shown in Fig.2, the phase matching retracing positions are λ1=1.31μm with θ =86.4°, φ=0° for Type I and λ2=1.30μm with θ=4.8°, φ=0° for Type II. The phase matching at these positions possess very large spectral acceptances Δλ. The calculated Δλ at λ1 and λ2are 57nm-cm-1/2 and 74nm-cm-1/2 respectively, which are much larger than the other NLO crystals. These spectral characteristics are very suitable for doubling broadband coherent radiations near 1.3μm, such as those from some diode lasers, and some OPA/OPO output without linewidth-narrowing components.
The crystal holder (free) and oven & Temperature Controller (for NCPM,OPO,OPA applications) are available for BBO & LBO.
1. LBO has a very low susceptibility to moisture. Users are advised to provide dry conditions for both the use and preservation of LBO.
2. Polished surfaces of LBO requires precautions to prevent any damage.
3. We can select and design the best crystal for you, if the main parameters of your laser are provided, such as energy per pulse, pulse width and repetition rate for a pulsed laser, power for a cw laser, laser beam diameter, mode condition, pergence, wavelength tuning range, etc.