Lifetime prediction model for third-harmonic antireflection under high-repetition-rate multipulse laser irradiation

The advancement of high-power, long-lifetime lasers has driven the need for enhanced laser-induced damage resistance and reliable lifetime assessments of optical coatings. This study employs accelerated testing to investigate the lifetimes of Al₂O₃/SiO₂-based third-harmonic antireflection coatings at repetition rates ranging from 500 Hz to 3300 Hz. By analyzing the damage behavior across different frequencies and pulse counts, the study reveals the evolution and statistical characteristics of the damage threshold and establishes a lifetime prediction model. A frequency factor derived from the coupling repetition frequency (F) and asymptotic limit threshold (T) allows for the calculation of the safe fluence range at various frequencies. At 3300 Hz, the predicted T deviates from the experimental data by only 0.88%. The model accurately captures the threshold variation with frequency and pulse count, showing strong agreement with the measurements. This approach bridges the gap between "laboratory threshold" and "service lifetime," providing a basis for reliability assessment in high-power space laser systems.