Spectrometer-free optical hydrogen sensing based on Fano-like spatial distribution of transmission in a metal-insulator-metal plasmonic Doppler grating

TL;DR

This paper introduces a spectrometer-free, spatial intensity-based optical hydrogen sensor using a plasmonic Doppler grating that detects hydrogen through changes in Fano-like transmission profiles, enabling compact and remote sensing.

Contribution

It presents a novel MIM-PDG platform that utilizes Fano-like spatial transmission profiles for hydrogen sensing without the need for spectrometers, suitable for portable applications.

Findings

Hydrogen absorption alters the Fano-like transmission profiles.

The platform can distinguish between hydrogen-sensitive and insensitive gratings.

The sensor is compatible with cellphone-based optical detection.

Abstract

Optical nanosensors are promising for hydrogen sensing because they are small, free from spark generation, and feasible for remote optical readout. Conventional optical nanosensors require broadband excitation and spectrometers, rendering the devices bulky and complex. An alternative is spatial intensity-based optical sensing, which only requires an imaging system and a smartly designed platform to report the spatial distribution of analytical optical signals. Here, we present a spatial intensity-based hydrogen sensing platform based on Fano-like spatial distribution of the transmission in a Pd-Al2O3-Au metal-insulator-metal plasmonic Doppler grating (MIM-PDG). The MIM-PDG manifests the Fano resonance as an asymmetric spatial transmission intensity profile. The absorption of hydrogen changes the spatial Fano-like transmission profiles, which can be analyzed with a "spatial" Fano-resonance model and the extracted Fano resonance parameters can be used to establish analytical calibration lines. While gratings sensitive to hydrogen absorption are suitable for hydrogen sensing, we also found hydrogen insensitive gratings, which provide an unperturbed reference signal and may find applications in nanophotonic devices, that require a stable optical response under fluctuating hydrogen atmosphere. The MIM-PDG platform is a spectrometer-free and intensity-based optical sensor that requires only an imaging system, making it promising for cellphone-based optical sensing applications.