Plasmonic sensors, leveraging the profound exposure of propagating Surface-Plasmon-Polariton (SPP) modes over metal stripes to test analytes, became so far the “gold-standard” in plasmonic biosensing resulting in commercial available devices. However, a series of challenges associated with their bulky prism-based coupling configuration as well as their high optical losses need to be overcome in order to allow for miniaturized and multiplexed sensor layouts. In this context, selective co-integration of plasmonics with low-loss silicon-nitride photonics emerges as a promising solution towards addressing these challenges yet reaping the benefits from both technologies. In this work, we present an interferometric sensor based on a Mach-Zehnder device, where a “plasmo-photonic” waveguide branch is utilized to interrogate changes in the refractive index of a test analyte exploiting the accumulated phase change of the SPP mode being exposed in an aqueous solution. More specifically, the “plasmo-photonic” Mach-Zehnder sensor incorporates a gold plasmonic stripe with a length of 70 μm and a width of 7 μm that has been interfaced with Si₃N₄ waveguides by means of a butt-coupled interface. By conducting numerical simulations and considering the dispersion properties of the involved materials, we optimized the structural parameters of the sensor aiming at ultra-high bulk sensitivity in the order of micrometres per Refractive Index Unit (RIU).

Date Published: 4 March 2019
PDF: 6 pages
Proc. SPIE 10921, Integrated Optics: Devices, Materials, and Technologies XXIII, 1092126 (4 March 2019); doi: 10.1117/12.2510041

Published in SPIE Proceedings Vol. 10921:
Integrated Optics: Devices, Materials, and Technologies XXIII
Sonia M. García-Blanco; Pavel Cheben, Editor(s)