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Future Challenges
Published in Tetsuzo Yoshimura, Self-Organized Lightwave Networks, 2018
When usual photosensitive materials such as photopolymers, photodefinable materials, and photosensitive glass are used for the PRI materials, SOLNETs provide permanent lightwave paths. In order to produce dynamic SOLNETs, which enable reorganization of optical wiring as schematically illustrated in Figure 8.3, rewritable PRI materials, for example, photorefractive materials and third-order nonlinear optical materials shown in Figure 3.7b and c are required. Fazio et al. have already developed the soliton waveguides in the photorefractive crystals of lithium niobate, opening the way to the dynamic optical interconnects as mentioned in Section 2.2. Development of high-speed rewritable PRI materials driven by low-power light beams might be the future challenge.
Solid-to-super-critical phase change and resulting stress wave during internal laser ablation
Published in Journal of Thermal Stresses, 2018
Yan Li, Chong Li, Wenlong Yao, Xinwei Wang
Nanostructure fabrication is a typical application of laser–material interactions. Nanostructures can be formed inside a photosensitive glass using a focused femtosecond laser [15, 16]. The discovery of long-range, self-organized, periodic planar nanocrack structures in fused silica is an important development in the field of laser dielectric modification [17]. Techniques for two-dimensional (2D) or three-dimensional (3D) image engraving inside a crystal have been developed on the basis of fused silica’s transparency and high refractive index [18, 19]. Ionization owing to multiphoton and avalanche processes increases the absorption in the localized area of the optical breakdown [20]. As a result of the laser energy absorption, the matter inside the breakdown area is heated and the process chain is triggered.
Enhancing the imaging quality and fabrication efficiency of bionic compound eyes using a sandwich structure
Published in Journal of Modern Optics, 2018
Jiasai Luo, Yongcai Guo, Xin Wang
Most of the current research on BCE has focused on improving the properties of the compound eye using different materials, novel fabrication methods and special structures. Furthermore, fabrication of a micro-lens array (MLA) is the basis for BCE, and numerous improvements have been made in fabrication methods. Conventional methods include photosensitive glass heat moulding (2,3), focused ion beam etching and deposition (4,5), the photoresist hot melt method (6–12), and the ion exchange method (13). Additionally, certain innovative methods have been introduced. Certain researchers prepared a moulding template for a concave MLA using femtosecond laser irradiation combined with HF acid etching (14). Subsequently, the MLA was formed after replication of a convex MLA on a PMMA film. A conductive membrane was deformed by an electrostatic force in a manner such that its shape could be controlled using the initial contour and underlying electrodes (15). Selected other methods, including micro-droplet jetting (16), Polystyrene (PS) microsphere self-assembly (17), and ultra-precision diamond machining (18), are actually 2D machining methods. To fabricate curved BCE, reverse moulding and substrate reshaping processes were employed, which might reduce the machining precision and increase the complexity of the process. Accordingly, a 3D fabrication method is necessary in order to directly fabricate a curved MLA. Several fabrication methods have been proposed, such as holographic interferometry (19), 3D MLA projection (20), and high-speed voxel-modulation laser scanning (21), but issues such as a long cycle time, a high cost and complex operation have limited extended application.