Modeling and Characterization of Deep-Etched Multilayer Resonators Under Partial Coherent Excitation Using Multimode Optical Fibers

Recently, there has been a resurgence of interest in multimode optical fibers illuminated by a white light source. Largely, in the anticipation of many integrated applications in the biomedical domain and spectral sensing benefiting from the broad spectral range and high numerical aperture. Along these lines, the output light from these fibers can be captured by the physics of partially coherent sources. Yet, the sheer complexity arising from the interplay between partial coherence and microstructure transfer function has posed fundamental challenges in deciphering their response. In this work, we present a numerical model and experimental characterization for the performance of multilayer optical resonators, fabricated by high aspect ratio etching of silicon, under partial coherent optical source excitation. The model studies the effects of optical fiber numerical aperture, Bragg mirror order, cavity length, and surface roughness of the microstructures on the output of the resonator. The results show that the response under standard multimode fiber (partial coherent source) has lower insertion loss, more asymmetry versus wavelength, and larger full width at half maximum (FWHM) than the standard single mode fiber (full coherent source). A MEMS chip is fabricated using 125 µm deep etching of silicon for Bragg mirrors with 2.25, 3, and 3.25 µm silicon layer width and a different number of layers. The structures are characterized using a multimode fiber of 62.5 µm core diameter illuminated by an infrared white light source. The theoretical results have been compared with the experimental results and a good agreement has been obtained.

近期，对由白光光源激发的多模光纤的兴趣呈现出新的增长势头。这主要得益于在生物医学领域以及受惠于宽广光谱范围和高数值孔径的光谱传感中，众多集成应用的预期。在此基础上，这些光纤输出的光可以被部分相干光源的物理特性所捕获。然而，由部分相干性与微结构传递函数相互作用产生的纯粹复杂性，为解读其响应带来了根本性的挑战。在本研究中，我们提出了一种数值模型和实验表征，用于研究由高纵横比刻蚀硅制成的多层光学谐振腔在部分相干光学源激发下的性能。该模型探讨了光纤数值孔径、布拉格镜面阶数、腔长以及微结构表面粗糙度对谐振腔输出影响。结果表明，在标准多模光纤（部分相干光源）下的响应具有比标准单模光纤（全相干光源）更低的插入损耗、更显著的对波长的不对称性以及更大的半峰全宽（FWHM）。利用125微米深度的硅刻蚀技术，制造了具有2.25、3和3.25微米硅层宽度和不同层数的布拉格镜面MEMS芯片。这些结构使用62.5微米芯径的多模光纤，并通过红外白光光源进行表征。理论结果与实验结果进行了比较，并取得了良好的吻合。