Tantalum pentoxide (Ta₂O₅) films deposited on fused silica substrates are critical components of high-power laser systems. Ion-assisted electron beam evaporation (IAD-EBE) is the mainstream technique for fabricating Ta₂O₅ films. However, it commonly requires extensive experimental efforts for deposition quality optimization, while each coating cycle is extremely time-consuming. To solve this issue, this work establishes a dataset targeting the surface roughness (Rq) and refractive index (n) of Ta₂O₅ films using atomic force microscopy, as well as ellipsometer and deposition experiments. Influence of assisting ion source beam voltage (V)/current (I) and Ar (Q₁)/O₂ (Q₂) flow rate on the n and Rq of Ta₂O₅ films are analyzed. Combining energy-field mechanism analysis with a Bayesian optimization approach (PI-BO), both deposition quality prediction and feature analysis of process parameters are achieved. The determination coefficient/mean absolute error for the prediction models of n and Rq reach 0.927/0.013 nm and 0.821/0.049 nm, respectively. Based on sensitivity analysis, the weight factors of V, I, Q₁, and Q₂ affecting n/Rq of Ta₂O₅ films are determined to be 0.616/0.274, 0.199/0.144, 0.113/0.582, and 0.072/0.000. V and Q₂ are identified as the core factors for regulating deposition quality. The optimal ranges for V and Q₂ are 600~700 V and 70~80 sccm, respectively. This study proposes a PI-BO method for predicting Rq and n of Ta₂O₅ films under small-data conditions, while determining the preferred parameter ranges and their sensitivity weight factors. These findings provide effective theoretical support and technical guidance for IAD-EBE strategy design and optimization of optical films in high-power laser systems.

For large-aperture dielectric film optics, the uniformity of film refractive index across the aperture is crucial to the uniformity of reflectance and transmittance. Herein, a comparative research has been performed on the refractive index uniformity of HfO₂ films across the Φ560 mm-aperture sample holder for inclined suspension and horizontal suspension. It’s revealed that the refractive index of HfO2 film at edge position of sample holder increased about 1.52% compared to that of HfO2 film at center position for inclined suspension, while the refractive index varied only about 0.25% for horizontal suspension. The further analysis performed on film crystallization, morphology and microstructure show that the large variation of refractive index between the films at center and edge positions of inclined suspension sample holder was attributed to the different growth properties. The film at the edge crystallized more slightly and was denser, thus being of higher refractive index. And the different growth properties of the two films at center and edge positions can be explained in the light of the co-effects of atomic shadowing, reemission and diffusion of ad-atoms during film growth.

A multi-aperture shower design is reported to improve the transverse uniformity of GdYBCO superconducting films on the template of sputtered-LaMnO₃/epitaxial-MgO/IBAD-MgO/solution deposition planarization (SDP)-Y₂O₃-buffered Hastelloy tapes. The GdYBCO films were prepared by the metal organic chemical vapor deposition (MOCVD) process. The transverse uniformities of structure, morphology, thickness, and performance were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), step profiler, and the standard four-probe method using the criteria of 1 μV/cm, respectively. Through adopting the multi-aperture shower instead of the slit shower, measurement by step profiler revealed that the thickness difference between the middle and the edges based on the slit shower design was well eliminated. Characterization by SEM showed that a GdYBCO film with a smooth surface was successfully prepared. Moreover, the transport critical current density (J_c) of its middle and edge positions at 77 K and self-field were found to be over 5 MA/cm² through adopting the micro-bridge four-probe method.

Electron-beam evaporation (EBE) is a multi-energy conversion process in which electrons are accelerated by an electric field, transfer kinetic energy to the evaporation source, and generate localized thermal energy for material evaporation and film growth. Post-deposition annealing provides an additional thermal field that promotes structural relaxation and defect evolution. In this study, 1064 nm HfO₂/SiO₂ highly reflective coatings deposited by EBE were annealed at 200 °C for 1–8 h to clarify how the duration of the post-deposition thermal field affects microstructure and optical-loss evolution. Atomic force microscopy combined with power spectral density analysis, spatial photoluminescence mapping, cavity ring-down measurements, and thermal absorption testing were employed. The coating response was distinctly non-monotonic: moderate annealing suppressed multiscale surface fluctuations and defect-related luminescence, whereas prolonged treatment partially reversed these changes. The total optical loss decreased from 1191.05 ppm to 837.88 ppm after 2 h, a reduction of 29.7%. Loss separation showed that absorption remained nearly stable after its initial decrease, while scattering recovered markedly at longer durations and dominated the subsequent increase in total loss. Scattering correlated strongly with surface roughness (r = 0.92), whereas absorption showed a positive correlation with photoluminescence intensity (r = 0.85). These results are consistent with distinct morphology-related and defect-related contributions to scattering and absorption, respectively, in EBE HfO₂/SiO₂ coatings.