We report on the fabrication of waveguides and beam splitter in pure YAG crystal by femtosecond laser directly writing (FLDW). During the femtosecond laser writing process, positive refractive index is induced through the nonlinear-focusing above the focus position, resulting in unusual guiding cross-sectional configuration. The supported guiding modes at 632.8 nm are measured and analyzed by the end-face coupling system. The propagation loss can be as low as 1.9 dB/cm for the single-line waveguide. Different from the geometry of traditional fs-laser modified area, this novel structure might offer a new approach in the quest to the integrated photonics.

中文翻译：

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通过飞秒激光写入 YAG 晶体的非线性聚焦制造的分束器

我们报告了通过飞秒激光直写 (FLDW) 在纯 YAG 晶体中制造波导和分束器。在飞秒激光写入过程中，正折射率通过焦点位置上方的非线性聚焦引起，导致不寻常的引导横截面配置。通过端面耦合系统测量和分析 632.8 nm 处支持的引导模式。对于单线波导，传播损耗可低至 1.9 dB/cm。与传统 fs-laser 修改区域的几何形状不同，这种新颖的结构可能为寻求集成光子学提供一种新方法。