The effect of thermal annealing on the optical properties, microstructure, and laser-induced damage threshold (LIDT) of HfO₂/Ta₂O₅/SiO₂ HR films has been investigated. The transmission spectra shift to a short wavelength and the X-ray diffraction peaks of monoclinic structure HfO₂ are enhanced after thermal annealing. The calculated results of the m( 111) diffraction peak show that the HfO₂ grain size is increased, which is conducive to increasing the thermal conductivity. Thermal annealing also reduces the laser absorption of high-reflection films. The improvement of thermal conductivity and the decrease of laser absorption both contribute to the improvement of LIDT. The experimental results show that the highest LIDT of 22.4 J/cm² is obtained at 300°C annealing temperature. With the further increase of annealing temperature, the damage changes from thermal stress damage to thermal explosion damage, resulting in the decrease of LIDT.

A Te-free binary phase change material SbBi is proposed as a new inorganic photoresist for heat-mode lithography. It shows good film-forming ability (surface roughness <1 nm), low threshold power for crystallization (2 mW), and high etching selectivity (15:1). Line-type, dot-type, and complex pattern structures with the smallest feature size of 275 nm are fabricated on SbBi thin films using a 405 nm diode laser direct writing system. In addition, the excellent grating structures with a period of 0.8 μm demonstrate that thermal interference does not affect the adjacent microstructures obviously. These results indicate that SbBi is a promising laser heat-mode resist material for micro/nanostructure fabrication.

We propose and experimentally demonstrate a wideband linear polarization converter in a reflection mode operating from 2.4 to 4.2 THz with conversion efficiency of more than 80%. Our device can expand the applications to a higher frequency band. A numerical simulation is performed for this metamaterial converter, which shows a good agreement with experimental results. Importantly, a concise and intuitive calculating model is proposed for the Fabry–Pérot cavity. The theoretical results indicate that the underlying reason for the enhanced polarization conversion is the additional phase difference induced by the resonance of the meta-structure and multiple reflections within the Fabry–Pérot cavity.

A λ/4–λ/4 broadband antireflective (AR) coating is developed with a sol-gel dip-coating method. By adding SAR-5 organosilicon resin into a base-catalyzed silica sol top layer and treating at 300°C, a broadband AR coating used for blast shields with a high average transmission of 99.34% (450–950 nm) and good hydrophobicity (with a water-contact angle of 119°) was obtained. After being subjected to rubbing 50 times and being maintained at a relative humidity of around 95% for 50 days, the average transmission of the coating decreased by 0.29% and 0.04%, respectively. This indicates that the organically modified silica (ORMOSIL) broadband AR coating has good abrasion resistance and humidity stability.

We prepare SiO2 coatings on different substrates by either electron-beam evaporation or dual ion-beam sputtering. The relative transmittances of the SiO2 coatings are measured during the heating process. The SiO2 coating microstructures are studied. Results indicate that the intensity and peak position of moisture absorption are closely related to the microstructures of the coatings. The formation of microstructures depends not only on the preparation process of the coatings but also on the substrate characteristics.

A Closed Cavity measuring platform is built on the basis of a 1000 W-class direct current (DC)-discharge drived continuous-wave (CW) HF/DF chemical laser. On this platform, the absorption coefficients of optical thin films coated on the surfaces of monocrystalline silicon substrates, at the wavelength of 3.6–4.1 μm, is measured, when the power density on the surfaces of optical thin films reaches about 3.16 kW/cm2. The measuring principle and structure of the Closed Cavity is introduced. The temperature curves and balanced temperature rises of the film-substrate systems under test measured through the experiment is presented in this Letter. The experiments show high reliability, good repeatability and strong practicality. The Closed Cavity measuring platform is applicable for not only absorption measurement but other performance measurement of optical thin films under high power density.

Light-induced transverse thermoelectric effect is investigated in incline-oriented Bi2Sr2Co2Oy thin films covered with a graphite light absorption layer. Upon the illumination of a 980 nm cw laser, an enhanced voltage signal is detected and the improvement degree is found to be dependent on the thickness of the graphite layer. A two-dimensional (2D) heat transport model using the finite-difference method provides a reasonable explanation to the experimental data. Present results give some valuable instructions for the design of light absorption layers in this type of detector.

A number of zinc oxide (ZnO) films are deposited on silicon substrates using the magnetron sputtering method. After undergoing thermal treatment under different conditions, those films exhibit hexagonal wurtzite structures and different photoluminescent characteristics. Besides the notable ultraviolet emission, which is related to the free exciton effect, a distinct blue fluorescence around 475 nm is found in some special samples. The blue photoluminescence emission of the ZnO film is believed to be caused by oxygen vacancies.

In our investigation, lead germanium telluride, which is a pseudo-binary alloy of IV-VI narrow-gap semiconductor compounds of PbTe and GeTe, can be used in the fabrication of mid-wavelength infrared narrow bandpass filters as a high-index coating material, due to its high refractive index, lower absorption, and tunability of fundamental absorption edges. It is demonstrated that a half-width of 160 nm and a better rejection ratio can be obtained for a simple 8-layer double cavity filter with a central wavelength at 4 μm, compared with a half-width of 390 nm for those conveniently fabricated using Ge as high-index material.

The defect evolution is investigated for high-reflective coatings under multiple irradiations with an improved statistical model. The fatigue effect is observed with an increase in the shot numbers, but the fatigue process will not endure and it tends to be saturated when the number of shots reaches a certain level. With the addition of a bilayer unit, the defect density distribution of the high-reflective coatings is obtained. Two defect types are identified, and the differentiation of the high-damage precursors can well explain the decrease of the laser-induced damage threshold, as well as the saturation effect.