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

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.

Efficient Optical Sensing Based on Phase Shift of Waves Supported by a One-Dimensional Photonic Crystal

“…Therefore, sensors based on the phase detection of waves supported by a 1DPhC are feasible [ 22 , 23 , 24 , 25 , 26 , 27 ]. In addition, they represent an alternative to relative humidity sensors based on resonances of surface plasmons [ 16 ], BSWs [ 16 ], whispering gallery modes [ 28 ], guided modes [ 4 , 7 , 29 ], photonic crystal modes [ 30 ], and lossy modes [ 31 , 32 ].…”

High‐Sensitivity Thin‐Film Grating Absorbers for Sensing Applications

“…[ 23 ] GMR is a diffraction phenomenon with intense coupling resonance in grating diffraction due to the matching of waveguide mode and grating parameters. [ 24,25 ] The interaction can cause very sharp resonance peaks in the reflection or transmission spectrum. The phase‐matching condition was fulfilled by the following formula [ 26 ] where the wave vector k = ω 0 / c of free space vacuum, θ is the incident angle, and m is the diffraction order of the grating.…”

“…[23] GMR is a diffraction phenomenon with intense coupling resonance in grating diffraction due to the matching of waveguide mode and grating parameters. [24,25] The interaction can cause very sharp resonance peaks in the reflection or transmission spectrum. The phase-matching condition was fulfilled by the following formula [26]…”

Polymer-Based Guided-Mode Resonance Sensors: From Optical Theories to Sensing Applications

“…and lower index layer (such as silicon dioxide, fused silica, etc.) 35 are deposited using plasma-enhanced chemical vapor deposition (PECVD) 36 on a glass substrate and the grating pattern is transferred to a photoresist 37 or electron-beam resist 38 using a lithography process. 16 A dry 39 or wet 40 etching process is followed to transfer the pattern into the film beneath it.…”