Laser-induced damage thresholds of ion beam sputtered and magnetron sputtered AR-coatings on lithium borate

Lithium triborate, LiB₃O₅ (LBO) is a popular nonlinear optical crystal typically used for frequency conversion. For power scaling of laser radiation in transparency range of LBO crystals with maintaining low reflection losses is very important to reach high optical resistance of anti-reflective dielectric coatings. The measurements of laser-induced damage thresholds (LIDT) of AR coated LBO used for second and third harmonic generation of Nd:YAG lasers were performed at 1064, 532, and 355 nm wavelengths for ~4 ns pulses. Two types of coatings where tested; a dual peak anti-reflection at 1064 nm and 532 nm, three peak anti-reflection at 1064 nm, 532 nm, and 355 nm. Ion beam sputtering and magnetron sputtering technologies were used for coatings deposition. Automated LIDT measurements were performed according to the requirements of current ISO 11254-2 standard. The obtained LIDT were in range of 5-21 J/cm².