The authors characterize femtosecond laser single-pulse machining of deep, micrometer-diameter holes and long, micrometer-width channels in fused silica by the use of spherical, cylindrical, and aspheric singlet lenses. Repositionable spherical lenses form an adjustable beam expander that also provides a means of minimizing—or deliberately introducing—spherical aberration (SA) in the focal region by controlling the beam divergence at the asphere. Inserting cylindrical lenses creates a line focus for machining channel patterns parallel to the sample surface and at any depth within the bulk of the sample. The effects of controlled SA and pulse energy on the depth of round-focus holes and line-focus channels are studied. Holes less than 1 μm in diameter but with depths exceeding 30 μm are observed in the case of strong positive SA. Channel patterns from ∼1 to 3 μm wide, up to 2000 μm long, and with depths of 6–40 μm can also be machined with a single pulse, depending on the lens configuration and pulse energy. For the highest pulse energies studied, channel features exhibit phenomena such as bifurcations and multiple, separated focal regions along the beam path, indicating a possible complex interplay between SA, self-focusing, and filamentation. The authors also present experiments on attempting to form arrays of closely spaced, parallel microfluidic channels in fused silica by KOH etching of line-focus features for highly parallelized microfluidic applications.

中文翻译：

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用单个飞秒激光脉冲加工微米级高纵横比特征

作者通过使用球面、柱面和非球面单透镜对熔融石英中深微米直径孔和长微米宽度通道的飞秒激光单脉冲加工进行了表征。可重新定位的球面透镜形成一个可调节的光束扩展器，它还提供了一种通过控制非球面光束发散来最小化或有意引入焦点区域中的球面像差 (SA) 的方法。插入柱面透镜会创建一个线焦点，用于加工平行于样品表面和样品主体内任何深度的通道图案。研究了受控SA和脉冲能量对圆聚焦孔和线聚焦通道深度的影响。在强正 SA 的情况下，观察到直径小于 1 μm 但深度超过 30 μm 的孔。根据透镜配置和脉冲能量，也可以使用单个脉冲加工从 1 到 3 μm 宽、2000 μm 长和 6-40 μm 深度的通道图案。对于研究的最高脉冲能量，通道特征表现出诸如分叉和沿光束路径的多个分离的焦点区域等现象，表明 SA、自聚焦和丝状结构之间可能存在复杂的相互作用。作者还展示了尝试通过 KOH 蚀刻线聚焦特征在熔融石英中形成紧密间隔的平行微流体通道阵列的实验，以用于高度并行化的微流体应用。通道特征表现出沿光束路径分叉和多个分离的焦点区域等现象，表明 SA、自聚焦和丝状结构之间可能存在复杂的相互作用。作者还展示了尝试通过 KOH 蚀刻线聚焦特征在熔融石英中形成紧密间隔的平行微流体通道阵列的实验，以用于高度并行化的微流体应用。通道特征表现出沿光束路径分叉和多个分离的焦点区域等现象，表明 SA、自聚焦和丝状结构之间可能存在复杂的相互作用。作者还展示了尝试通过 KOH 蚀刻线聚焦特征在熔融石英中形成紧密间隔的平行微流体通道阵列的实验，以用于高度并行化的微流体应用。