Trypanophobics rejoice. Researchers from the University of Technology Sydney (UTS) and TMOS, an Australian Research Council Centre of Excellence, have made new progress towards the development of mid-infrared nanophotonics, which could potentially be used in future biomolecular detectors to allow for breath testing for coming illnesses, replacing blood testing and providing immediate results to doctors without the need for lab analysis.

Mid-Infrared detectors can identify the optical ‘fingerprints’ of different types of molecules such as cancer variations, viruses and bacteria. However, the devices have been too heavy, bulky, and expensive to produce for practical use, often requiring cryogenic cooling.

TMOS researchers are exploring metasurfaces—a new technology that replaces traditional optics—to find solutions to these barriers. In research published in Nanomaterials MDPI, the team from UTS and TMOS, in collaboration with the team from Vanderbilt University, has realized extreme sub-wavelength confinement of mid-infrared photons (a vital feature required for high-resolution detectors), with an extended operational wavelength range in nanowires featuring layers of graphene and silicon carbide.

Given the nanoscopic size of these nanowires, the detector could one day be no thicker than cling wrap, enabling the production of lightweight, handheld devices cheap enough to be found in every doctor’s office. The analysis could occur immediately within the device and the results delivered within seconds, saving time and hassle as well as saving lives.

Lead author Patrick Rufangura from UTS says, “The most exciting about this research is the breadth of future practical applications. This technology could be implemented on a larger scale to monitor greenhouse gas emissions from space or in different mediums. You could use it to monitor the quality of drinking water in developing countries, potentially preventing outbreaks of disease.”

The hybrid nanostructure combining graphene and silicon carbide extends the spectral phonon response of silicon carbide and enables absorption and field enhancement of the mid-infrared photon via the excitation and hybridization of surface plasmon polaritons and surface phonon polaritons.

The team demonstrated enhanced absorption of mid-infrared photons and broadening the spectral resonance of graphene-coated silicon carbide nanowires. They also indicated subwavelength confinement of the mid-infrared photons within a thin oxide layer a few nanometres thick, sandwiched between the graphene and silicon carbide.

This research was supported by the Commonwealth of Australia, represented by the Defence Science and Technology Group, for the project-based funding agreement n.8673.

Enhanced Absorption with Graphene-Coated Silicon Carbide Nanowires for Mid-Infrared Nanophotonics

Patrick Rufangura, Iryna Khodasevych, Arti Agrawal, Matteo Bosi,Thomas G. Folland, Joshua D. Caldwell and Francesca Iacopi
Nanomaterials, 8th September 2021

The mid-infrared (MIR) is an exciting spectral range that also hosts useful molecular vibrational fingerprints. There is a growing interest in nanophotonics operating in this spectral range, and recent advances in plasmonic research are aimed at enhancing MIR infrared nanophotonics. In particular, the design of hybrid plasmonic metasurfaces has emerged as a promising route to realize novel MIR applications. Here we demonstrate a hybrid nanostructure combining graphene and silicon carbide to extend the spectral phonon response of silicon carbide and enable absorption and field enhancement of the MIR photon via the excitation and hybridization of surface plasmon polaritons and surface phonon polaritons. We combine experimental methods and finite element simulations to demonstrate enhanced absorption of MIR photons and the broadening of the spectral resonance of graphene-coated silicon carbide nanowires. We also indicate subwavelength confinement of the MIR photons within a thin oxide layer a few nanometers thick, sandwiched between the graphene and silicon carbide. This intermediate shell layer is characteristically obtained using our graphitization approach and acts as a coupling medium between the core and outer shell of the nanowires.