Hybrid Metamaterial Absorber Platform for Sensing of CO₂ Gas at Mid‐IR

Abstract

Application of two major classes of CO2 gas sensors, i.e., electrochemical and nondispersive infrared is predominantly impeded by the poor selectivity and large optical interaction length, respectively. Here, a novel “hybrid metamaterial” absorber platform is presented by integrating the state‐of‐the‐art complementary metal–oxide–semiconductor compatible metamaterial with a smart, gas‐selective‐trapping polymer for highly selective and miniaturized optical sensing of CO2 gas in the 5–8 µm mid‐IR spectral window. The sensor offers a minimum of 40 ppm detection limit at ambient temperature on a small footprint (20 µm by 20 µm), fast response time (≈2 min), and low hysteresis. As a proof‐of‐concept, net absorption enhancement of 0.0282%/ppm and wavelength shift of 0.5319 nm ppm−1 are reported. Furthermore, the gas‐ selective smart polymer is found to enable dual‐mode multiplexed sensing for crosschecking and validation of gas concentration on a single platform. Additionally, unique sensing characteristics as determined by the operating wavelength and bandwidth are demonstrated. Also, large differential response of the metamaterial absorber platform for all‐optical monitoring is explored. The results will pave the way for a physical understanding of metamaterial‐based sensing when integrated with the mid‐IR detector for readout and extending the mid‐IR functionalities of selective polymers for the detection of technologically relevant gases.

Progress of infrared guided-wave nanophotonic sensors and devices

“…In a device footprint of only 20 µm by 20 µm, the CO 2 detection with a detection limit down to 40 ppm was achieved by leveraging the high electric field enhancement by crosswire nanoplasmonic structures together with a thin-film membrane for selective gas sensing and local gas enrichment (Fig. 9a) [173,174]. Similar nanoplasmonic-enhanced MIR absorption sensing applications have also been demonstrated using bow-tie [175][176][177][178] and crooked [179] nanoplasmonic structures.…”

Leveraging of MEMS Technologies for Optical Metamaterials Applications

“…In addition to metamaterials, nanophotonics is another branch of research direction for mid‐IR chemical sensing and functional applications, which is beyond the scope of this review. Many works related to SEIRA have been done to detect analytes in the gas phase, the solid phase (thin films), and the liquid phase (solutions) …”

“…Leveraging resonant SEIRA in metamaterials, optical interaction length for the same detection resolution can be reduced by 1000 times compared to spiral waveguide and free space nondispersive infrared (NDIR) gas sensor . To further improve the detection limit of metamaterial gas sensors, different enrichment layers, such as graphene, metal‐organic framework (MOF), polyethylenimine (PEI) are used to trap gas molecules into metamaterial hotspots in order to locally enhance near‐field interaction. Combining PEI and metamaterial absorber, Hasan et al presented a hybrid metamaterial absorber for CO 2 sensing and achieved sub‐ppm level resolution .…”

“…To further improve the detection limit of metamaterial gas sensors, different enrichment layers, such as graphene, metal‐organic framework (MOF), polyethylenimine (PEI) are used to trap gas molecules into metamaterial hotspots in order to locally enhance near‐field interaction. Combining PEI and metamaterial absorber, Hasan et al presented a hybrid metamaterial absorber for CO 2 sensing and achieved sub‐ppm level resolution . As shown in Figure a, the cross‐shape hybrid metamaterial absorber made from Mo‐AlN‐Mo was spin‐coated with PEI thin film and characterized in a heater‐integrated gas chamber.…”

“…IR gas sensor using plasmonic metamaterial with gas enrichment layer of a) PEI and b) graphene; IR molecular imaging using multipixel metamaterial sensors by absorption fingerprints in c) mid‐IR and d) wavelength shift in near‐IR; e) Angle‐multiplexed all‐dielectric metasurfaces for broadband molecular fingerprint retrieval; liquid sensing in mid‐IR using f) nanofluidic and g) microfluidic; h,i) microfluidic sensing in GHz region. (a) Reproduced with permission . Copyright 2018, Wiley‐VCH.…”