Guided-Mode Resonance-Based Relative Humidity Sensing Employing a Planar Waveguide Structure

Petra Urbancova; Jakub Chylek; Petr Hlubina; Dusan Pudis

doi:10.3390/s20236788

Guided-Mode Resonance-Based Relative Humidity Sensing Employing a Planar Waveguide Structure

Sensors (Basel). 2020 Nov 27;20(23):6788. doi: 10.3390/s20236788.

Authors

Petra Urbancova¹, Jakub Chylek², Petr Hlubina², Dusan Pudis¹

Affiliations

¹ Department of Physics, Faculty of Electrical Engineering and Information Technology, University of Zilina, Univerzitna 1, 01026 Zilina, Slovakia.
² Department of Physics, Technical University Ostrava, 17. listopadu 2172/15, 708 00 Ostrava-Poruba, Czech Republic.

Abstract

In this paper, we present a new type of guided-mode resonance (GMR)-based sensor that utilizes a planar waveguide structure (PWS). We employed a PWS with an asymmetric three-layer waveguide structure consisting of substrate/Au/photoresist. The ellipsometric characterization of the structure layers, the simulated reflectance spectra, and optical field distributions under GMR conditions showed that multiple waveguide modes can be excited in the PWS. These modes can be used for refractive index sensing, and the theoretical analysis of the designed PWS showed a sensitivity to the refractive index up to 6600 nm per refractive index unit (RIU) and a figure of merit (FOM) up to 224 RIU^-1. In response to these promising theoretical results, the PWS was used to measure the relative humidity (RH) of moist air with a sensitivity up to 0.141 nm/%RH and a FOM reaching 3.7 × 10^-3%RH^-1. The results demonstrate that this highly-sensitive and hysteresis-free sensor based on GMR has the potential to be used in a wide range of applications.

Keywords: figure of merit; guided-mode resonance; humidity sensor; planar waveguide structure; resonance wavelength; sensitivity.

Publication types

Letter