Index-tunable anti-reflection SiO₂ coatings prepared on the surface of VO₂ films by sol–gel dip-coating technique to enhance the visible and infrared transmittance of SiO₂/VO₂ films.

To investigate the pyramid–prism (PY–PR) boundary of a rapidly grown KDP crystal, the exact position of the PY–PR boundary of an X-cut rapidly grown KDP sample is determined by measuring the refractive-index non-uniformity. The peak-valley value of Δ(n_e–n_o) near the PY–PR boundary is approximately 3 × 10⁻⁶, and the width of the distortion area near the PY–PR boundary is approximately 0.6 mm. The FWHM values of the high-resolution X-ray diffraction peaks in the pyramidal sector, the prismatic sector, and the region containing the PY–PR boundary are all 0.008°, indicating the fine crystalline quality of the crystal. Moreover, the existence of the PY–PR boundary does not affect the fine crystalline quality. From the pyramidal sector to the prismatic sector, the transmittance in the ultraviolet region decreases gradually when crossing the PY–PR boundary. The fluences corresponding to 50% laser-induced damage (LID) probability are 11.9, 12.8, and 17.0 J cm⁻² (3 ns, 355 nm) for the PY–PR boundary, the pyramidal sector, and the prismatic sector, respectively. By identifying different types of defects in each sector, it is found that the PY–PR boundary exhibited the worst LID performance. This is because there are more bulk microdefects in the PY–PR boundary. These defects are more likely to be inclusions induced by the instability of the steps near the PY–PR boundary.

We report the periodic concentric surface structures on SiO₂ layer induced by a single shot nanosecond laser pulse at 1.06 μm. The fringe period of the structures ranges from 7.0 μm to 26.8 μm, depending on the laser fluence and the distance from central defect precursor. The size and depth of the damage sites increase almost linearly with the laser fluence from 19.6 J/cm² to 61 J/cm². Plasma flash was clearly observed during the damage process. We attribute the formation mechanism of the structures to the interference between the reflected laser radiations at the air/shock-front and the shock-front/film interfaces.

In this paper, the effects of oxygen vacancy and gallium vacancy on the optical and scintillation properties of undoped β-Ga₂O₃ crystal and 2.5 mol % Al doped gallium oxide were investigated. For the undoped β-Ga₂O₃, the transmittance is improved after annealing in oxygen or nitrogen atmosphere. After the introduction of Al element, the absorption cutoff appears slightly blue shift, and the band gap increases. For the undoped as-grown β-Ga₂O₃ single crystals, the decay time consists of a fast component (τ₁) of the order of nanoseconds, and two slow components (τ₂, τ₃) of tens to hundreds of nanoseconds. The contribution of the fast decay time component in the decay times is 2.78%. While for Al-doped β-Ga₂O₃, the faster (τ₁) time is 2.33 ns for the as-grown one, and the contribution is 68.02%. However, the pulse height spectrum shows that the introduction of 2.5 mol % Al will reduce the light yield of the β-Ga₂O₃ crystal.

Amorphous TiO₂ nanostructured thin films (TNFs) were deposited by the glancing angle deposition technique (GLAD) with an electron gun. All of the prepared TNFs were composed of discrete nanoscale columns, characterized by scanning electron microscope. With the annealing treatment, the pure anatase phase was transformed from amorphous TNFs. The morphological, structural and optical properties of TNFs under the annealing treatment were measured, and the evolvement mechanism was further analyzed. The optimum annealing temperature for the pure anatase precipitation of TNFs is about 400°C. The variation of morphology, chemical state and crystallization of TNFs also resulted in the shift of the transmittance spectra. The results show that appropriate post-annealing treatment can build fine nanostructures and pure anatase precipitation, which can support the applications and researches about the anatase phase TNFs powerfully.

To reduce the seed length while maintaining the advantages of the cuboid KDP-type crystal, a long-seed KDP crystal with size $471~\text{mm}\times 480~\text{mm}\times 400~\text{mm}$ is rapidly grown. With almost the same high cutting efficiency to obtain third harmonic generation oriented samples, this long-seed KDP-type crystal can be grown with a shorter seed than that of the cuboid KDP-type crystal. The full width at half maximum of the high-resolution X-ray diffraction of the (200) crystalline face is 28.8 arc seconds, indicating that the long-seed KDP crystal has good crystalline quality. In the wavelength range of 377–1022 nm, the transmittance of the long-seed KDP crystal is higher than 90%. The fluence for the 50% probability of laser-induced damage (LID) is $18.5~\text{J}/\text{cm}^{2}$ (3 ns, 355 nm). Several test points survive when the laser fluence exceeds $30~\text{J}/\text{cm}^{2}$ (3 ns, 355 nm), indicating the good LID performance of the long-seed KDP crystal. At present, the growth of a long-seed DKDP crystal is under way.