Broadband multilayer dielectric gratings (MDGs) with rectangular HfO₂ grating profile were realized for the first time using a novel fabrication process that combines laser interference lithography, nanoimprint, atomic layer deposition and reactive ion-beam etching. The laser-induced damage initiating at the grating ridge was mitigated for two reasons. First, the rectangular grating profile exhibits the minimum electric-field intensity (EFI) enhancement inside the grating pillar compared to other trapezoidal profiles. Second, our etching process did not create nano-absorbing defects at the edge of the HfO₂ grating where the peak EFI locates, which is unavoidable in traditional fabrication process. The fabricated MDGs showed a high laser induced damage threshold of 0.59J/cm² for a Ti-sapphire laser with pulse width of 40 fs and an excellent broadband diffraction spectrum with 95% efficiency over 150 nm in TE polarization.

In this study, ZnS/YbF₃-10.6 µm antireflection (AR) coatings were fabricated on CVD single-crystal diamond and ZnSe substrates. The spectral characteristics of the coatings and their performance under continuous wave laser radiation at 10.6 µm were systematically investigated. The fabricated AR coatings exhibited excellent spectral properties in the target wavelength range. Both theoretical calculations and experimental results indicated that, at the same power density, the 10.6 µm AR coatings on diamond substrates exhibited a lower temperature rise compared to those deposited on ZnSe substrates. Due to its high thermal conductivity, the diamond substrate is expected to exhibit reduced thermally induced surface distortion. The laser-induced damage threshold (LIDT) test results indicate that the AR coating deposited on the ZnSe substrate exhibits a damage threshold of 11,890 W/cm², whereas the AR coating on the diamond substrate achieves a threshold of 15,287 W/cm², representing a 28.5% improvement over the ZnSe substrate. Additionally, graphite formation occurs on the diamond substrate under high power density. These findings provide both theoretical and experimental support for the potential application of diamond materials in high-power laser systems.

The feasibility of using direct broad band optical monitoring control in the fabrication of the ultra-steep dichroic filters based on resonant structures is investigated. Using computational manufacturing and deposition experiments, the role of the errors self-compensation effect is clarified by comparing the results of direct broad band optical monitoring and time monitoring. The errors correlation strength of ultra-steep dichroic filter is analyzed and it shows that the correlation calculated by the current model is not strong. The relationship between errors correlation and errors self-compensation effect for the ultra-steep dichroic filter is discussed.

The design and fabrication approach of a dichroic beamsplitter to meet the protection requirements of infrared detectors for blinding laser weapons is presented. The dichroic beamsplitter must protect against 1064 and 532 nm lasers and have high transmittance in the detection beam band of 3.6–4.7 µm. In order to realize the protection and antireflection (AR) functions of the dichroic beamsplitter, Ta₂O₅, which has a wide band gap and high thermodynamic stability, was selected as the high-refractive-index material. A multilayer stack was deposited on a silicon substrate by ion-assisted electron beam evaporation. The manufactured dichroic beamsplitter features a high laser-induced damage threshold (LIDT), excellent spectral characteristics in the requested spectral region, and good environmental stability.

Hf_1−xSi_xO₂ nanocomposites with different SiO₂ doping ratios were synthesized using an ion-assisted co-evaporation process to achieve dense amorphous Hf_1−xSi_xO₂ coatings with low loss and a high laser-induced damage threshold (LIDT). The results showed that the Hf_1−xSi_xO₂ nanocomposites (x ≥ 0.20) exhibited excellent comprehensive performance with a wide band gap and a dense amorphous microstructure. High-temperature annealing was carried out to ensure better stoichiometry and lower absorption. Precipitation and regrowth of HfO₂ grains were observed from 400 °C to 600 °C during annealing of the Hf_0.80Si_0.20O₂ nanocomposites, resulting in excessive surface roughness. A phenomenological model was proposed to explain the phenomenon. The Hf_1−xSi_xO₂ nanocomposites (x = 0.3 and 0.4) maintained a dense amorphous structure with low absorption after annealing. Finally, a 1064-nm Hf_0.70Si_0.30O₂/SiO₂ high-performance reflector was prepared and achieved low optical loss (15.1 ppm) and a high LIDT (67 J/cm²).

Amorphous silicon (a-Si) is a promising material with a high refractive index that shows great potential in the development of low-thermal-noise, highly reflective coatings for gravitational-wave detectors due to its low mechanical loss. However, its high optical absorption has hindered its practical use. The primary objective of this paper is to investigate the effects of hydrogen incorporation into a-Si on its optical properties and mechanical loss with ion-beam sputtering (IBS) technology, which is widely used to produce coatings with low absorption and scattering loss. It is demonstrated that hydrogenation can effectively reduce the optical absorption of a-Si, with the concentration of hydrogen proving to be a crucial factor. Optimal annealing temperature can further enhance the coating quality, in which silicon atom rearrangement also contributes to the improvement. Overall, using the process combination can reduce the extinction coefficient of a-Si coatings by 16-fold at 1064 nm and 85-fold at 1550 nm, while simultaneously reducing mechanical loss by a factor of 12. The degree of mechanical loss reduction is closely related to the order present in the atomic structure of the silicon network. To our knowledge, this study represents the first comprehensive analysis of coating mechanical loss in hydrogenated a-Si deposited via IBS.