We report on a conceptually new type of waveguide in glass by femtosecond laser direct writing, namely, photonic lattice-like waveguide (PLLW). The PLLW’s core consists of well-distributed and densified tracks with a sub-micron size of 0.62 µm in width. Specifically, a PLLW inscribed as hexagonal-shape input with a ring-shape output side was implemented to converse Gaussian mode to doughnut-like mode, and high conversion efficiency was obtained with a low insertion loss of 1.65 dB at 976 nm. This work provides a new freedom for design and fabrication of the refractive index profile of waveguides with sub-micron resolution and broadens the functionalities and application scenarios of femtosecond laser direct-writing waveguides in future 3D integrated photonic systems.

多年来，硅和锗一直被认为是合适制造探测器和集成光电器件的半导体材料。然而，与金刚石基器件相比，这种四价半导体的抗辐射损伤能力较差，而且在恶劣条件或高强光辐照下，器件的稳定性较差。近年来，金刚石因其优异的光学与力学性能，在集成光子学、传感和量子光学等领域展现了巨大的应用前景。利用激光诱导金刚石微纳结构为开发金刚石上的三维光互联器件、全碳探测器、石墨电阻以及单光子源的实现提供了一种有潜力的制备方法。阐述了飞秒激光诱导金刚石色心形成、石墨化和折射率变化的物理机制，在此基础上，进一步探究了飞秒激光诱导金刚石微纳结构在单光子源、传感器和光波导等方面的应用，并对未来发展趋势进行了展望。

We report on the elemental redistribution behavior in oxyfluoride glasses with a high repetition rate near-infrared femtosecond laser. Elemental analysis by an electro-probe microanalyzer demonstrates that the redistributions of Ca²⁺ and Yb³⁺ ions change dramatically with pulse energy, which are quite different compared with previous reported results. Confocal fluorescence spectra of Yb³⁺ ions demonstrate that the luminescence intensity changes obviously with the elemental redistribution. The mechanism of the observed phenomenon is discussed. This observation may have potential applications in the fabrication of micro-optical devices.