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To address the issue of the lack of red light in traditional Ce3+: YAG-encapsulated blue LED white light systems, we utilized spark plasma sintering (SPS) to prepare spinel-based Cr3+-doped red phosphor ceramics. Through phase and spectral analysis, the SPS-sintered ZnAl2O4: 0.5%Cr3+ phosphor ceramic exhibits good density, and Cr3+ is incorporated into [AlO6] octahedra as a red emitting center. We analyzed the reasons behind the narrow-band emission and millisecond-level lifetime of ZAO: 0.5%Cr3+, attributing it to the four-quadrupole interaction mechanism as determined through concentration quenching modeling. Additionally, we evaluated the thermal conductivity and thermal quenching performance of the ceramic. The weak electron-phonon coupling (EPC) effects and emission from antisite defects at 699 nm provide positive assistance in thermal quenching. At a high temperature of 150 °C, the thermal conductivity reaches up to 14 W·m−1·K−1, and the 687 nm PL intensity is maintained at around 70% of room temperature. Furthermore, the internal quantum efficiency (IQE) of ZAO: 0.5%Cr3+ phosphor ceramic can reach 78%. When encapsulated with Ce3+: YAG for a 450 nm blue LED, it compensates for the lack of red light, adjusts the color temperature, and improves the color rendering index (R9). This provides valuable insights for the study of white light emitting diodes (WLEDs). [ABSTRACT FROM AUTHOR]

It is well-known that the surface quality of laser gain crystal elements is very high in order to ensure the stability of laser system and laser output quality. In the ultra-precision machining process of a new sesquioxide laser crystal Tm: GdScO3, it is required to achieve very high surface shape and very low surface defects. In this paper, the molecular dynamics simulation model of single particle grinding was established. It was found that the normal load and tangential friction imposed by abrasive particles on the surface of components cause the spalling of atoms on the substrate surface, which constitutes the removal of materials at the macro-level. At the same time, it causes the displacement of the sub surface atoms, which constitutes the microscopic defects in the structure. Through the structural characterization of macro defects, it was confirmed that the essence of micro defects is the amorphous and distortion of surface structure, and the depth can reach 100 nm. The results of lapping and polishing experiments show that the adjustment of pressure has a limited effect on the improvement of surface defects in the process of machining crystal elements with granular abrasive. [ABSTRACT FROM AUTHOR]

In this paper, Yb:LuScO3 crystal was processed by chemical mechanical polishing (CMP), and the surface roughness of 0.18 nm was obtained. The atomic step structures of these sesquioxide crystals are successfully characterized by AFM scanning probe technology. Through several CMP experiments, the basic material removal mechanism of a ytterbium-doped LuScO3 crystal during CMP is studied. Based on the findings, a material removal model is established. The results of this study provide ideas for the study of CMP, crystal growth and epitaxy. [ABSTRACT FROM AUTHOR]

X-ray mirrors are an important part of the beam line in advanced light sources and have a stringent surface roughness, and monocrystalline silicon is the preferred substrate material for X-ray mirror. A method of improving the surface roughness of X-ray mirror, based on optimized density and dynamic viscosity of the polishing fluid, is analyzed and tested experimentally. The experimental results show that the surface roughness of monocrystalline silicon substrates was reduced significantly, with the root mean square of surface roughness decreasing from 0.420 nm to 0.272 nm, corresponding to an improvement of approximately 32%. [ABSTRACT FROM AUTHOR]

X-ray free-electron lasers are large modern scientific devices that play an important role in fields such as frontier physics and biomedicine. In this study, a light source is connected to an experimental station through beam lines, which requires numerous ultra-smooth and high-precision X-ray mirrors. Monocrystalline silicon is an ideal substrate material where ion-beam figuring is required. However, the ultra-smooth surface is damaged after the ion-beam figuring. Through an analysis of the machined surface, it is found that in the process of vacuum pumping, the impurities in the cavity adhere to the machined surface and increase the roughness after processing. Therefore, an optimized vacuum-pumping scheme is proposed. The experiment demonstrates that the original value of the processed surface roughness remains unchanged. [ABSTRACT FROM AUTHOR]

Abstract: Grayscale patterns have been widely studied and applied in many fields. In this paper, grayscale patterns with precise grayscale changes are fabricated on TeO x thin film by laser pulse with respective wavelengths of 635 and 405nm. Two obvious changes according to the different grayscale level emerge as laser energy increases. The first change is from invisible to white-grayscale with low laser pulse width between 2ns and 50ns. After a transient period with laser pulse width between 48ns and 55ns, the grayscale in the second change becomes darker and darker following the laser pulse width increases from 56ns to 250ns. The mechanism of the grayscale change is partly explained and verified by TEM, which involves the agglomeration and segregation of Te, crystallization and recrystallization after melting of Te and TeO2, and ablation of TeO x , wherein different mechanism is dominant in each stage. We can obtain grayscale patterns with precise grayscale changes to meet specific requirements by controlling the parameters precisely. [Copyright &y& Elsevier]

In this work, we used the multilayered ZnS–SiO2/AgO x/ZnS–SiO2 films as the laser direct writing materials, and pattern structures with different shapes and sizes were directly written with green laser ( λ=488 nm). Compared with traditional photoresist materials, the pattern structures can be directly formed in this film structures without developing and etching procedures and also can be directly written by very low laser power. By tuning the laser parameters precisely, pattern structures with different sizes and shapes could be obtained as well. The analysis indicates that the formation mechanism of the pattern structure is mainly due to the volume expansion caused by AgO x decomposition into silver particles and oxygen. The oxygen applies pressure to the ZnS–SiO2 layer and makes a hollow shell under the film. The aspect ratios of the patterns rapidly increase from the minimum of 0.012 in laser power of 3.0 mW to the maximum of 0.201 in laser power of 5.0 mW. The thermal stability of the patterns was also qualitatively studied. [ABSTRACT FROM AUTHOR]

In this paper, Yb:LuScO3 crystal was processed by chemical mechanical polishing (CMP), and the surface roughness of 0.18 nm was obtained. The atomic step structures of these sesquioxide crystals are successfully characterized by AFM scanning probe technology. Through several CMP experiments, the basic material removal mechanism of a ytterbium-doped LuScO3 crystal during CMP is studied. Based on the findings, a material removal model is established. The results of this study provide ideas for the study of CMP, crystal growth and epitaxy. [ABSTRACT FROM AUTHOR]

Nano-optical information storage is very important in meeting information technology requirements. However, obtaining nanometric optical information recording marks by the traditional optical method is difficult due to diffraction limit restrictions. In the current work, the nonlinear saturable absorption effect is used to generate a subwavelength optical spot and to induce nano-optical information recording and readout. Experimental results indicate that information marks below 100 nm are successfully recorded and read out by a high-density digital versatile disk dynamic testing system with a laser wavelength of 405 nm and a numerical aperture of 0.65. The minimum marks of 60 nm are realized, which is only about 1/12 of the diffraction-limited theoretical focusing spot. This physical scheme is very useful in promoting the development of optical information storage in the nanoscale field., (This journal is © The Royal Society of Chemistry 2011)