# Barium borate, BaB2O4 (BBO)

BaB2O4, commonly known as beta-barium borate (BBO), is a nonlinear optical crystal with a wide transparency range, extending from the ultraviolet to the near-infrared. Known for its high damage threshold and phase-matching capabilities, BBO is frequently employed in frequency doubling, tripling, and other nonlinear processes in laser systems. Its crystal structure allows for phase-matching over a wide range of wavelengths, making it highly versatile for different optical applications. BBO crystals also offer the advantages of a high refractive index and strong birefringence, which contribute to their effectiveness in nonlinear processes. However, the material is hygroscopic and requires careful handling to prevent surface degradation over time. Despite this, its broad phase-matching capabilities and high damage threshold make BaB2O4 one of the most popular choices for nonlinear optics, particularly in applications requiring high peak intensities or broad tunability across various wavelengths. Overall, BBO continues to be a material of significant interest in the field of nonlinear optics, both for its well-established applications and for its potential in emerging technologies.

## Most common allotrope

- Beta barium borate (ß-BaB2O4)

## External links

- Barium borate - Wikipedia
- BBO Crystal (Beta Barium Borate) - Optical Components