LBO Nonlinear Crystals
Lithium triborate (LiB3O5) LBO is an excellent non-linear optics crystal, which has a wide transparency range, high damage threshold, moderately high nonlinear coupling and desirable chemical and mechanical properties. LBO crystals have been widely used in second harmonic generation (SHG), for example of Nd:YAG lasers (1064 nm ~ 532 nm). LBO can be both critically and non-critically phase-matched.
Thanks to its large spectral transmission range as well as noncritical phase matching (NCPM) in the near IR region, LBO crystals have been applied in non-linear optical applications like OPO, OPA,OPCPA and other. Since its broad gain bandwidth overlaps with Ti:Sapphire in 800 nm range, ultra-high power and high contrast laser systems have been built based on the mixed CPA/OPCPA plan.
Wide transmission region from 160 nm to 2600nm
Large effective second-harmonic-generation (SHG) coefficient (about three times that of KDP)
Good mechanical and physical properties
High damage threshold of 18.9 GW/cm2 for a 1.3 ns laser at 1053 nm
Both Type I and II NCPM in a wide wavelength range is possible
Wide acceptance angle and small walk-off
High optical homogeneity with δn≈10-6/cm
Spectral NCPM near 1300 nm
Frequency doubling and tripling of Nd:YAG and Nd:YLF lasers.
SHG and THG for middle and high power Nd: lasers at 1064 nm for medical, industrial and military applications.
SHG and THG of high power Nd: lasers at 1342 nm & 1319 nm for red and blue laser.
Optical parametric amplifiers (OPA) and oscillators (OPO) pumped by Excimer lasers and harmonics of Nd:YAG lasers.
Optical parametric chirped pulse amplification (OPCPA) in ultrafast pulse system.
Chemical and Physical Properties
Orthorhombic, Space group Pna21, Point group mm2
a=8.4473Å ,b=7.3788Å, c=5.1395Å, Z=2
Thermal expansion coefficient
ax=10.8x10-5/K, ay= -8.8x10-5/K, az=3.4x10-5/K
Negative biaxial crystal: 2Vz = 109.2◦ at λ = 0.5321μm
Linear Optical Properties
169 - 2600 nm
<0.1%/cm at 1064nm <0.3%/cm at 532nm
at 1.0642 mm
at 0.5321 mm
at 0.2660 mm
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
Sellmeier Equations(λ in μm)
Nonlinear Optical Properties
SHG Phase Matchable Range
551 ~ 2600nm (Type I) 790-2150nm (Type II)
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
(°C,λ in μm)
6.54mrad-cm (Φ, Type I,1064 SHG)
15.27mrad-cm (q, Type II,1064 SHG)
at 1.064 mm
at 0.532 mm
9 GW/cm2 (9 ns); 19 GW/cm2 (1.3 ns)
2.2 GW/cm2 (10 ns); 45 GW/cm2 (100 ps)
Figure 2. SHG tuning curves of LBO
Figure 3. OPO tuning curves of LBO (TypeI (ooe) in ‘XY’ plane) with different pump light, namely 530 nm, 355 nm and 266 nm
AR Coatings S1/S2,nm/nm
Q: What is phase mismatching?
A: A group of techniques for achieving efficient nonlinear interactions in a medium. Many phase-sensitive nonlinear processes, in particular parametric processes such as frequency doubling, sum and difference frequency generation, parametric amplification and oscillation, and also four-wave mixing, require phase matching to be efficient. Essentially, this means ensuring that a proper phase relationship between the interacting waves (for optimum nonlinear frequency conversion) is maintained along the propagation direction. Only if that condition is fulfilled, amplitude contributions from different locations to the product wave are all in phase at the end of the nonlinear crystal.
Q: What is Second harmonic generation (SHG)?
A: SHG is a nonlinear optical process, in which photons with the same frequency interacting with a nonlinear material are effectively "combined" to generate new photons with twice the energy, and therefore twice the frequency and half the wavelength of the initial photons.