With different interactions between material and femtosecond lasers, two-dimensional (2D) and three-dimensional (3D) waveguide couplers, whose separation distances are fabricated in z-cut lithium niobate crystal by femtosecond laser writing, are reported. Experimentally and numerically, it is shown from results that the guidance is only propagating along TM polarization due to the Type I modification and holds equal splitting ratios, which are the same as power splitters at 632.8 nm. The propagation losses of 2D and 3D waveguide couplers exhibit better transmission properties than those of the previously reported Type I Y-junction waveguide splitters.femtosecond laser writing beam splitters lithium niobate
Chinese Optics Letters
2023, 21(11): 112201
2023, 60(17): 1712007
Diagnosis of fluids is extremely significant at high temperatures and high pressures. As an advanced imaging technique, high-energy proton radiography has great potential for application to the diagnosis of high-density fluids. In high-energy proton radiography, an angular collimator can control the proton flux and thus enable material diagnosis and reconstruction of density. In this paper, we propose a multi-material diagnostic method using angular collimators. The method is verified by reconstructing the density distribution from the proton flux obtained via theoretical calculations and numerical simulations. We simulate a 20 GeV proton imaging system using the Geant4 software toolkit and obtain the characteristic parameters of single-material objects. We design several concentric spherical objects to verify the method. We discuss its application to detonation tests. The results show that this method can determine the material and boundary information about each component of a multi-material object. Thus, it can be used to diagnose a mixed material and reconstruct densities in a detonation.
Matter and Radiation at Extremes
2023, 8(4): 046902
2023, 43(16): 1623018
Wettability is one of a solid surface’s fundamental physical and chemical properties, which involves a wide range of applications. Femtosecond laser microfabrication has many advantages compared to traditional laser processing. This technology has been successfully applied to control the wettability of material surfaces. This review systematically summarizes the recent progress of femtosecond laser microfabrication in the preparation of various superwetting surfaces. Inspired by nature, the superwettabilities such as superhydrophilicity, superhydrophobicity, superamphiphobicity, underwater superoleophobicity, underwater superaerophobicity, underwater superaerophilicity, slippery liquid-infused porous surface, underwater superpolymphobicity, and supermetalphobicity are obtained on different substrates by the combination of the femtosecond laser-induced micro/nanostructures and appropriate chemical composition. From the perspective of biomimetic preparation, we mainly focus the methods for constructing various kinds of superwetting surfaces by femtosecond laser and the relationship between different laser-induced superwettabilities. The special wettability of solid materials makes the femtosecond laser-functionalized surfaces have many practical applications. Finally, the significant challenges and prospects of this field (femtosecond laser-induced superwettability) are discussed.
2022, 2(1): 9895418
通过理论仿真和实际制备测试, 分析比较了基于非对称量子阱结构(10nm厚和6nm厚的量子阱组合)的光放大芯片与对称量子阱结构(10nm厚量子阱)的光放大芯片的性能。两种结构的理论模式增益同最终实测值符合较好。最终光谱测试结果显示, 对称量子阱结构的光放大芯片存在基态增益饱和的现象, 在大电流注入情况下, 激态跃迁占据优势, 从而造成光谱宽度急剧下降。而非对称量子阱结构的光放大芯片的光谱宽度随着注入电流的增加不断拓宽, 在600mA下实现199.7nm光谱带宽, 覆盖S+C波段。由此可见, 非对称量子阱结构更有利于实现高功率、宽光谱的光放大芯片。宽光谱 S+C波段 对称和非对称多量子阱 wide spetrum S+C band InGaAlAs/InP InGaAlAs/InP symmetric and asymmetric multi-quantum-well
Underwater transportation of bubbles and gases has essential applications in manipulating and using gas, but achieving this function at the microscopic level remains a significant challenge. Here, we report a strategy to self-transport gas in water along a laser-induced open superhydrophobic microchannel with a width less than 100 μm. The femtosecond laser can directly write superhydrophobic and underwater superaerophilic microgrooves on the polytetrafluoroethylene (PTFE) surfaces. In water, the single laser-induced microgroove and water medium generate a hollow microchannel. When the microchannel connects two superhydrophobic regions in water, the gas spontaneously travels from the small region to the large area along this hollow microchannel. Gas self-transportation can be extended to laser-drilled microholes through a thin PTFE sheet, which can even achieve anti-buoyancy unidirectional penetration. The gas can overcome the bubble’s buoyance and spontaneously travel downward. The Laplace pressure difference drives the processes of spontaneous gas transportation and unidirectional bubble passage. We believe the property of gas self-transportation in the femtosecond laser-structured open superhydrophobic and underwater superaerophilic microgrooves/microholes has significant potential applications related to manipulating underwater gas.femtosecond laser gas transportation superhydrophobicity underwater superaerophilicity water/gas separation
International Journal of Extreme Manufacturing
2022, 4(1): 015002