Drouin Antoine, Lorre Pierre, Boisvert Jean-Sébastien, Loranger Sébastien, Iezzi Victor Lambin, Kashyap Raman
Opt Express. 2019 Feb 4;27(3):2488-2498. doi: 10.1364/OE.27.002488.
Laser-written waveguides in glass have many potential applications as photonic devices. However, there is little knowledge of the actual profile of the usually asymmetric refractive index (RI) change across the femtosecond (fs) laser-written waveguides. We show, here, a new nondestructive method to measure any symmetric or asymmetric two-dimensional RI profile of fs laser-written waveguides in transparent materials. The method is also suitable for the measurement of the RI profile of any other type of waveguide. A Mach-Zehnder interferometer is used to obtain the phase shift of light propagating transversely through the RI-modified region. A genetic algorithm is then used to determine the matching cross-sectional RI profile based on the known waveguide shape and dimensions. A validation of the method with the comparison to a RNF measurement of the industry-standard SMF-28 is presented, as well as a demonstration of its versatility with measurements on fs laser-written waveguides.
玻璃中的激光写入波导作为光子器件有许多潜在应用。然而，对于飞秒（fs）激光写入波导中通常不对称的折射率（RI）变化的实际分布情况，人们了解甚少。在此，我们展示了一种新的无损方法，用于测量透明材料中飞秒激光写入波导的任何对称或不对称二维RI分布。该方法也适用于测量任何其他类型波导的RI分布。马赫-曾德尔干涉仪用于获取横向穿过RI改性区域的光的相移。然后使用遗传算法根据已知的波导形状和尺寸确定匹配的横截面RI分布。本文给出了该方法与行业标准单模光纤（SMF-28）的折射近场（RNF）测量结果对比的验证，以及在飞秒激光写入波导测量中展示其通用性的示例。
