Ga₂O₃ thin films were fabricated by the electron-beam evaporation technique at a varying oxygen partial pressure from 0 to 2.0 × 10⁻² Pa. The effect of oxygen partial pressure on the crystalline structure and optical properties of the Ga₂O₃ films was analyzed using sophisticated techniques including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, spectroscopic ellipsometry, ultraviolet-visible spectroscopy and a laser-induced damage test system. The correlation between the oxygen partial pressure and the film’s properties in optics and materials were investigated. XRD and Raman revealed that all films were amorphous in spite of applying a varying oxygen partial pressure. With the change of oxygen partial pressure, XPS data indicated that the content of oxygen in the Ga₂O₃ films could be broadly modulable. As a result, a changeable refractive index of the Ga₂O₃ film is realizable and a variable blue-shift of absorption edges in transmittance spectra of the films is achievable. Moreover, the damage threshold value varied from 0.41 to 7.51 J/cm² according to the rise of oxygen partial pressure. These results demonstrated that the optical properties of Ga₂O₃ film can be broadly tunable by controlling the oxygen content in the film.

A micro-pyramid structured thin film with a broad-band infrared antireflection property is designed and fabricated by using the single-point diamond turning (SPDT) technique and combined with nano-imprint lithography (NIL). A structure with dimensions of 10 μm pitch and 5 μm height is transferred from the copper mold to the silicon nitride optical film by using NIL and proportional inductively-coupled plasma (ICP) etching. Reflectance of the micro-optical surface is reduced below 1.0% over the infrared spectral range (800–2500 nm). A finite-difference-time-domain (FDTD) analysis indicates that this micro-structure can localize photons and enhance the absorption inside the micro-pyramid at long wavelengths. As described above, the micro-pyramid array has been integrated in an optical film successfully. Distinguishing from the traditional micro-optical components, considering the effect of refraction and diffraction, it is a valuable and flexible method to take account of the interference effect of optical film.

In this paper, the Fe³⁺ doped rutile phase TiO₂ nanotubes arrays (NTAs) were prepared in a low temperature water-assistant crystallization method. It is noteworthy that the Fe³⁺ doping hardly hinders either the crystallization of rutile TiO₂ NTAs or the highly-ordered nanotubular morphologies. Moreover, Fe³⁺ did not form other compound impurities, which indicated that Fe³⁺ substitute Ti⁴⁺ into the lattice of TiO₂. With the introduction of Fe³⁺, the light absorption range of TiO₂ NTAs extends from the ultraviolet band to the visible light range. Photocatalytic testing results indicate that Fe³⁺ doped TiO₂ NTAs can effectively improve the degradation rate of methyl orange aqueous solution in visible light, and the TiO₂ NTAs with 0.2 mol/L Fe³⁺ doping exhibits the highest photocatalytic degradation efficiency.

In this paper, synthetically using refraction, diffraction, and interference effects to achieve free manipulation of the focused optical field, we firstly present a photonic nanojet (PNJ) generated by a micropyramid, which is combined with multilayer thin films. The theory of total internal reflection (TIR) was creatively used to design the base angle of the micropyramid, and the size parameters and material properties of the microstructure were deduced via the expected optical field distribution. The as-designed bilayer micropyramid array was fabricated by using the single-point diamond turning (SPDT) technique, nanoimprint lithography (NIL), and proportional inductively coupled plasma (ICP) etching. After the investigation, the results of optical field measurement were highly consistent with those of the numerical simulation, and they were both within the theoretical calculation range. The bilayer micropyramid array PNJ enhanced the interference effect of incident and scattered fields; thus, the intensity of the focused light field reached 33.8-times that of the initial light, and the range of the focused light field was extended to 10.08$\lambda$. Moreover, the full width at half maximum (FWHM) of the focal spot achieved was 0.6$\lambda$, which was close to the diffraction limit.

To measure the profile of an off-axis aspheric surface with large asphericity or lateral displacement, a hybrid compensation method is employed to realize a null test. First, the hybrid compensation method is simulated in MATLAB by using a fold sphere mirror and a computer-generated hologram (CGH) to compensate for the primary aberration and residual high-order aberration, respectively. For contrast, the hybrid compensation method is also simulated in Zemax by using dummy glass. Through comparing the simulation results from MATLAB and Zemax, the test CGH fringe positions from the two results are well matched. Then, the fold sphere mirror and CGH optical elements are designed and fabricated for an actual hybrid compensation measurement system, and the auto-collimation method is also used to detect the same off-axis aspheric surface. To ensure the correctness of the experiment, the result of actual hybrid compensation testing is contrasted with that of the auto-collimation method. Experiments show that the results obtained by the two methods are consistent, which indicates that this kind of hybrid compensation is an effective and accurate method for measurement of off-axis aspheric surfaces.

Double perovskite Cs₂SnI₆ and its doping products (with SnI₂, SnF₂ or organic lithium salts added) have been utilized as p-type hole transport materials for perovskite and dye-sensitized solar cells in many pieces of research, where the mechanism for producing p-type Cs₂SnI₆ is rarely reported. In this paper, the mechanism of forming p-type Li⁺ doped Cs₂SnI₆ was revealed by first-principles simulation. The simulation results show that Li⁺ entered the Cs₂SnI₆ lattice by interstitial doping to form strong interaction between Li⁺ and I⁻, resulting in the splitting of the α spin-orbital of I–p at the top of the valence band, with the intermediate energy levels created and the absorption edge redshifted. The experimental results confirmed that Li⁺ doping neither changed the crystal phase of Cs₂SnI₆, nor introduced impurities. The Hall effect test results of Li⁺ doped Cs₂SnI₆ thin film samples showed that Li⁺ doping transformed Cs₂SnI₆ into a p-type semiconductor, and substantially promoted its carrier mobility (356.6 cm²/Vs), making it an ideal hole transport material.