玻璃波导有效折射率的原位测量（特邀）

飞秒激光直写玻璃波导是快速制备三维集成光子芯片的一种重要手段，波导有效折射率的准确测量对于设计光子器件意义重大。设计并制备了一种断臂马赫-曾德尔干涉仪（MZI）结构对玻璃波导有效折射率进行原位精密测量。激光在断线区域和波导内的有效折射率不同，在传输相同长度下产生一定的相位差，最终导致不同的干涉结果。对断臂MZI结构的相位干涉结果进行处理，得到激光直写玻璃波导的有效折射率为1.504+7.7×10?4。利用RSOFT软件光束传播算法对器件进行模拟仿真，仿真结果与实验吻合良好。该精确测量玻璃波导有效折射率的方法对于提升光子芯片设计与制造能力具有重要意义。

In-situ measurement of effective refractive index of glass waveguides (invited)

Femtosecond laser direct writing of glass waveguides is an important means to rapidly prepare three-dimensional integrated photonic chips, and the accurate measurement of the effective refractive index of waveguides is significant for designing photonic devices. A breaking-arm Mach-Zendel interferometer (MZI) structure is designed and fabricated for in-situ precise measurement of the effective refractive index of glass waveguides. The different effective refractive index of the laser in the breaking region and within the waveguide produces a certain phase difference at the same length of transmission, which eventually leads to different interference results. The phase interference results of the MZI of the breaking arm are processed to obtain the effective refractive index of the laser direct-written glass waveguide as 1.504+7.7×10?4. The device is simulated by using the beam propagation algorithm of RSOFT, and the simulation results are in good agreement with the experimental results. This accurate measurement of the effective refractive index of the glass waveguide is of great significance for the enhancement of photonic chip design and fabrication.