【摘要】 飞秒激光脉冲具有极高的峰值功率和极短的脉冲宽度,与物质相互作用时呈现出强烈的非线性效应,使其可以深入透明介质内部,以超越光学衍射极限的精度对材料进行三维微加工.除此之外,飞秒激光三维直写技术具有高度的灵活性,即可以在单一芯片上制备并集成多种不同功能的微纳结构.这些特性使该技术迅速发展成为微制造领域的研究热点,在微流体、微光学、光电子学以及光量子芯片制备与集成等领域表现出广阔的前景.但还有一些问题限制飞秒激光直写技术的进一步发展,比如加工通道的尺寸和长度限制、较高的加工表面粗糙度等.针对这些问题,本文重点介绍了在玻璃中制备三维微纳流体通道以及高品质光学微腔的最新进展.更多还原

【Abstract】 Femtosecond lasers have opened up new avenues in materials processing due to their unique characteristics of ultrashort pulse widths and extremely high peak intensities. The short pulse width suppresses the formation of a heat-affected zone, which is vital for ultrahigh precision fabrication, whereas the high peak intensity allows multiphoton absorption to be induced in materials that are transparent to the laser wavelength. More interestingly, irradiation with tightly focused femtosecond laser pulses inside transparent materials provides a facile route to modify the interior of transparent materials in a spatially selective manner, enabling three-dimensional（3D） fabrication and integration of multifunctional micro-/nano-structures and components in a monolithic substrate. For instance, femtosecond laser pulses have been used to write optical waveguides in both passive and active materials by locally modifying their refractive indices. In combination with wet chemical etching, femtosecond laser direct writing has also been used to fabricate microfluidic structures, including microchannels and chambers, microvalves, and micropumps. The same technique has been extended to fabricate free-space optics such as micromirrors and micro-optical lenses in glass materials. By virtue of its unique ability to build different types of functional components into a monolithic substrate, femtosecond laser direct writing offers a flexible approach to fabricate a wide variety of integrated devices and microsystems. Although femtosecond laser micromachining have indeed shown extreme flexibility for fabrication and integration of 3D multifunctional micro- components in bulk transparent materials, several major issues still exist, such as the limited size of the microfluidic structures, the limited fabrication resolution, high surface roughness, and so on. This review focuses primarily on the recent efforts to tackle the two issues as mentioned above. By use of femtosecond laser direct writing in porous glass immersed in water followed by post-annealing, we demonstrated microfluidic channels with nearly unlimited lengths and arbitrary 3D geometries. By controlling the laser peak intensity and polarization, a single nanoplane with sub-50-nm feature size could be achieved inside porous glass based on these strategies, several functional devices and their applications have been demonstrated, including 3D passive microfluidic mixer and an integrated micro-nanofluidic system for single DNA analysis. Furthermore, we demonstrate fabrication of 3D whispering gallery microcavities with quality（Q）-factors on the level of ¹×10⁶ in glass chips by femtosecond laser direct writing followed by CO₂ laser reflow.更多还原