Dhakal Ashim, Raza Ali, Peyskens Frédéric, Subramanian Ananth Z, Clemmen Stéphane, Le Thomas Nicolas, Baets Roel
Opt Express. 2015 Oct 19;23(21):27391-404. doi: 10.1364/OE.23.027391.
We develop and experimentally verify a theoretical model for the total efficiency η0 of evanescent excitation and subsequent collection of spontaneous Raman signals by the fundamental quasi-TE and quasi-TM modes of a generic photonic channel waveguide. Single-mode silicon nitride (Si3N4) slot and strip waveguides of different dimensions are used in the experimental study. Our theoretical model is validated by the correspondence between the experimental and theoretical absolute values within the experimental errors. We extend our theoretical model to silicon-on-insulator (SOI) and titanium dioxide (TiO2) channel waveguides and study η0 as a function of index contrast, polarization of the mode and the geometry of the waveguides. We report nearly 2.5 (4 and 5) times larger η0 for the fundamental quasi-TM mode when compared to η0 for the fundamental quasi-TE mode of a typical Si3N4 (TiO2 and SOI) strip waveguide. η0 for the fundamental quasi-TE mode of a typical Si3N4, (TiO2 and SOI) slot waveguide is about 7 (22 and 90) times larger when compared to η0 for the fundamental quasi-TE mode of a strip waveguide of the similar dimensions. We attribute the observed enhancement to the higher electric field discontinuity present in high index contrast waveguides.
我们开发并通过实验验证了一个理论模型，该模型用于描述由通用光子通道波导的基本准TE和准TM模式对倏逝激发以及随后自发拉曼信号收集的总效率η0。实验研究中使用了不同尺寸的单模氮化硅（Si3N4）狭缝和条形波导。我们的理论模型通过实验值与理论绝对值在实验误差范围内的一致性得到验证。我们将理论模型扩展到绝缘体上硅（SOI）和二氧化钛（TiO2）通道波导，并研究η0作为折射率对比度、模式偏振和波导几何形状的函数。我们报告称，与典型Si3N4（TiO2和SOI）条形波导的基本准TE模式的η0相比，基本准TM模式的η0大近2.5（4和5）倍。与类似尺寸条形波导的基本准TE模式的η0相比，典型Si3N4（TiO2和SOI）狭缝波导的基本准TE模式的η0大约大7（22和90）倍。我们将观察到的增强归因于高折射率对比度波导中存在的更高电场不连续性。
