Thermodynamic mechanism in colored glass substrates of interference filters under continuous-wave laser irradiation.

The ablation perforation damage of double-sided coated narrow-band filters based on RG-850 colored glass under out-of-band laser irradiation is investigated. A temperature-triggered nonlinear absorption mechanism is identified where substrate absorption sharply increases beyond a critical temperature. To quantify the resulting energy deposition dynamics, the multiple reflection model is employed, revealing the absorption enhancement by partial-transmission/high-reflection coatings. Building on this foundation, a parameter inversion method derives the equivalent average absorption coefficient from dual-transmittance laser-induced damage threshold (LIDT) ratios, thereby establishing a LIDT predictive framework for arbitrary transmittance. Finally, finite element analyses (FEA) provide validation for the multiple reflection model and inversion method, demonstrating the coating structure's role in absorption enhancement and successfully predicting damage thresholds across three transmittance configurations.