1：Experimental Design and Method Selection:

The study compares three substrate cleaning methods (ultrasonic, chemical etching, and ion beam etching) for AR coatings deposited by dual ion beam sputtering (DIBS). The rationale is to evaluate how different cleaning methods affect laser-induced damage threshold (LIDT) and defect properties. Theoretical models include the defect distribution model for damage probability analysis and thermal stress calculations for damage mechanisms.

2：Sample Selection and Data Sources:

UV grade fused silica substrates (Corning Incorporated) with 50 mm diameter and 5 mm thickness are used. AR coatings consist of 11 layers of SiO2 and Al2O3, approximately 1.3 μm thick, designed for multi-wavelength anti-reflection at 355 nm, 532 nm, and 1064 nm.

3：3 μm thick, designed for multi-wavelength anti-reflection at 355 nm, 532 nm, and 1064 nm. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Dual ion beam sputtering equipment (VEECO Corp.), stylus surface profiling system (Bruker DektakXT), Nd:YAG laser at 355 nm, focused ion beam-field emission scanning electron microscopy (FIB-FESEM; Zeiss), X-ray photoelectron spectroscopy (XPS; Thermo Scientific), atomic force microscopy (AFM; Bruker Nano Inc.), and optical microscope for damage detection.

4：Experimental Procedures and Operational Workflow:

Substrates are cleaned using ultrasonic (deionized water, 8 min), acid etching (BOE solution: 1% HF and 15% NH4F, 8 min), or ion beam etching (4900s and 9800s etching times). Etching depth is measured using a barrier method. AR coatings are deposited immediately after cleaning in the DIBS device. Laser damage tests are performed using 1-on-1 method per ISO 21254, with 355 nm laser, 8 ns pulse width, 400 μm spot size, and 20 sites per fluence. Damage is detected online with CCD and offline with microscope.

5：Data Analysis Methods:

Damage probability curves are fitted linearly to extract LIDT and defect density using the defect distribution model. Surface roughness is analyzed via AFM, elemental composition via XPS, and damage morphologies via FIB-FESEM. Thermal stress in layers is calculated using material parameters.