Lithium triborate

Lithium triborate (LiB₃O₅, or LBO) is a non-linear optics crystal. It has a wide transparency range, moderately high nonlinear coupling, high damage threshold and desirable chemical and mechanical properties. This crystal is often used for second harmonic generation (SHG aka frequency doubling) of Nd:YAG lasers (1064 nm → 532 nm). LBO can be both critically and non-critically phase-matched. In the latter case the crystal has to be heated or cooled depending on the wavelength.

• Crystal structure: Orthorhombic
• Point group: mm2
• Lattice parameters: a=8.4473 Å, b=7.3788 Å, c=5.1395 Å
• Mohs hardness: 6
• Transmission range: 0.16 – 2.6 μm
• Damage threshold: 25 J/cm² (1064 nm, 10 ns pulses)
• Thermal expansion coefficients: x: 10.8×10⁻⁵/K, y: −8.8×10⁻⁵/K, z: 3.4×10⁻⁵/K
• Specific heat: 1060 J/kg·K
• Melting point: 834 °C