Optimized design for grating-coupled waveguide-enhanced Raman spectroscopy

Ettabib, Mohamed A., Liu, Zhen, Zervas, Michalis N. and Wilkinson, James S. (2020) Optimized design for grating-coupled waveguide-enhanced Raman spectroscopy. Optics Express, 28 (25), 37226-37235. (doi:10.1364/OE.410602).

Abstract

We report a new design optimization process for planar photonic waveguides applied to waveguide-enhanced Raman spectroscopy (WERS) that combines the optimization of both the surface intensity performance and the grating coupling efficiency. We consider the impact of film thickness on the grating coupling efficiency of two materials with different refractive indices, namely tantalum pentoxide (Ta2O5) and silicon (Si). We propose a new figure-of-merit (FOM) that takes into account both the coupling efficiency and surface intensity dependence for Raman excitation on the film thickness. Our study shows that the optimum surface-sensitive waveguide thickness is thinner than the optimum coupling efficiency thickness for both material systems. As an example, for a tantalum pentoxide waveguide operating at 785 nm, our optimization strategy proposes a 20% increase in waveguide core thickness relative to the optimum surface-sensitive thickness to achieve the best performance in WERS applications. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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Contributors

Author: Michalis N. Zervas

Author: James S. Wilkinson

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