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Double- and Multi-Femtosecond Pulses Produced by Birefringent Crystals for the Generation of 2D Laser-Induced Structures on a Stainless Steel Surface
摘要： Laser-induced textures have been proven to be excellent solutions for modifying wetting, friction, biocompatibility, and optical properties of solids. The possibility to generate 2D-submicron morphologies by laser processing has been demonstrated recently. Employing double-pulse irradiation, it is possible to control the induced structures and to fabricate novel and more complex 2D-textures. Nevertheless, double-pulse irradiation often implies the use of sophisticated setups for modifying the pulse polarization and temporal profile. Here, we show the generation of homogeneous 2D-LIPSS (laser-induced periodic surface structures) over large areas utilizing a simple array of birefringent crystals. Linearly and circularly polarized pulses were applied, and the optimum process window was defined for both. The results are compared to previous studies, which include a delay line, and the reproducibility between the two techniques is validated. As a result of a systematic study of the process parameters, the obtained morphology was found to depend both on the interplay between fluence and inter-pulse delay, as well as on the number of incident pulses. The obtained structures were characterized via SEM (scanning electron microscopy) and atomic force microscopy. We believe that our results represent a novel approach to surface structuring, primed for introduction in an industrial environment.
关键词： metal surface texturing,2D-LIPSS,femtosecond,micro/nanostructuring,birefringent crystals,double pulses
更新于2025-11-14 14:32:36
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Exploration of new birefringent crystals in bismuth d0 transition metal selenites
摘要： The first examples of bismuth fluoride selenites with d0-TM/Te(VI) polyhedrons, namely, Bi4TiO2F4(SeO3)4 (1), Bi4NbO3F3(SeO3)4 (2), Bi4TeO4F2(TeO3)2(SeO3)2 (3), Bi2F2(MoO4)(SeO3) (4) and Bi2ZrO2F2(SeO3)2 (5) have been successfully synthesized under hydrothermal reactions by aliovalent substitution. The five new compounds feature three different types of structures. Compounds 1-3, containing Ti(IV), Nb(V) and Te(VI) respectively, are isostructural, exhibiting a new 3D framework composed of 3D bismuth oxyfluoride architecture with intersecting tunnels occupied by d0-TM/Te(VI) octahedrons and selenite/tellurite groups. Compound Bi4TeO4F2(TeO3)2(SeO3)2 (3) is the first structure containing Se(IV) and mixed-valent Te(IV)/Te(VI) cations simultaneously. Compound 4 features a new 3D structure formed by 3D bismuth oxyfluoride network with MoO4 tetrahedrons and selenites groups embeded in the 1D tunnels. Compound 5 displays a novel pillar-layered 3D open framework consisted of 2D bismuth oxide layers bridged by the [ZrO2F2(SeO3)2]6- polyanions. Theoretical calculations revealed that the five compounds displayed very strong birefringence. The birefringence values of compounds 1-3, especially, are above 0.19 at 1064 nm, which are bigger than the mineral calcite. Based on the structure and property analysis, we found that the asymmetric SeO3 groups (and TeO3 in compound 3) displayed the largest anisotropy compared with the bismuth cations and the d0 TM/Te polyhedrons, which is beneficial to the birefringence.
关键词： metal selenites,d0 transition metals,aliovalent substitution,hydrothermal reactions,birefringent crystals
更新于2025-09-23 15:23:52
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Orthogonal Phase Demodulation of Optical Fiber Fabry-Perot Interferometer Based on Birefringent Crystals and Polarization Technology
摘要： In this paper, we propose and demonstrate the optical fiber Fabry-Perot (F-P) interferometer based on birefringent crystals and polarization technology. For recovering the variation signals, the orthogonal signals are obtained based on the birefringent crystal characteristics and the proposal thickness difference between the two crystals. The differential cross multiplication (DCM) algorithm is utilized to demodulate the orthogonal signals to obtain the phase variation of the optical fiber F-P sensor. The proposed interferometer has a minimum detection phase of 0.014 rad/Hz at the frequency of 25 kHz. In the experiment, two kinds of vibration signals with frequencies of 25 kHz and 15 kHz are used and the proposed interferometer SNR is 70 dB and 75 dB under the corresponding reference environment respectively. The experiment results show that the proposed interferometer can realize the measurement of large dynamic signals and has high stability. The proposed interferometer has the advantages of fast demodulation and good environmental adaptability.
关键词： phase variation,orthogonal signals,birefringent crystals,Optical fiber Fabry-Perot interferometer
更新于2025-09-19 17:13:59