Here, single-mode waveguides are written in silica glass by femtosecond (fs) laser. The waveguides exhibit a low propagation loss of 0.15 dB/cm and a symmetrical mode field. The loss performance and the mode field symmetry are demonstrated to strongly depend on the pulse repetition and polarization of fs laser, respectively. Raman and photoluminescence properties indicate that an increase of refractive index originates from an increment in the total density of glass networks consisting of small and large rings, but only increasing the number of small rings does not necessarily lead to an increase in refractive index. The long working distance of the objective lens promises to fabricate low-loss waveguides in a large depth of glass, which would inspire manufacturing integrated photonic devices by fs laser writing. Clarifying the mechanism of refractive index change offers a new perspective to understand the fs laser-matter interaction.

中文翻译：

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飞秒激光写入石英玻璃中的低损耗波导：高对称模场和折射率变化机理

在这里，单模波导通过飞秒（fs）激光写入石英玻璃。波导表现出0.15 dB / cm的低传播损耗和对称模式场。损耗性能和模场对称性分别强烈依赖于fs激光器的脉冲重复和偏振。拉曼和光致发光性质表明，折射率的增加源自由小环和大环组成的玻璃网络的总密度的增加，但是仅增加小环的数目并不一定导致折射率的增加。物镜的长工作距离有望在大玻璃深度中制造低损耗波导，这将激发通过fs激光写入制造集成光子器件的灵感。