Lithium Tri-borate (LBO) is one of the most useful nonlinear optical material not just for its relatively large conversion coefficient - 3x that of KDP, but also for its excellent physical properties.
LBO crystal has broad optical transparency range from 160 to 2600nm. It excels in high power SHG with minimal thermal lensing as compared to KTP. Its large acceptance angle paired with small walk-off angle which reduces the beam quality requirement for source lasers.