Channeling light into nanobelts

CNPEM/MCTI researchers and collaborators investigate the confinement of long infrared waves in tin oxide nanobelts.

Infrared light is a band of the electromagnetic spectrum whose waves have lengths ranging from 750 nanometers to 100 microns. Three sub-bands can be defined within this spectral range, called near, medium and far infrared. Near infrared is routinely applied to remote controls, presence sensors and other metrology tools while medium infrared is explored in sensors and heat cameras. Finally, far infrared, commonly referred to as terahertz radiation because it is close to these frequencies, is used in non-destructive probes and gas spectrometers.

Far infrared is a low-energy and non-destructive radiation, suitable for applications in biological materials. It also has a high penetration in materials allowing its use in the non-invasive inspection of goods and people. In addition, this band has the ability to excite vibrational and rotational modes of countless molecules in gases and liquids, which enables the identification and study of new materials. Despite these numerous unique properties, the far infrared band has long been a little explored field of science due to the limited availability of sources and detectors in this energy range. However, in recent years, advances in electronics and optics have made numerous advances in this area possible.

In phase with technological advances in the detection and emission of infrared radiation and driven by the arrival of two-dimensional materials, infrared nanophotonics has been dedicated to studying new materials, such as graphene, in order to explore their properties and their use in this energy range. In this context, nano-structured semiconductor oxides have gained relevance given the abundance of elements with chemical affinity with oxygen combined with the variety of ways in which they can be synthesized: nanoparticles (0D), nanowires (1D), nanofilms (2D), nanocubes (3D), among others. However, the confinement and manipulation of long waves in the infrared region in these materials remain poorly developed subjects.

As such, researchers from the Brazilian Center for Research in Energy and Materials (CNPEM), a private non-profit organization under supervision of the Brazilian Ministry of Science, Technology, and Innovations (MCTI), and collaborators from Brazil and abroad studied the confinement of long infrared waves in tin oxide (SnO2) nanobelts. To this end, the group combined Infrared Nanospectroscopy experiments performed on synchrotron light sources, UVX from the Brazilian Synchrotron Light Laboratory (LNLS) and ALS from the Lawrence Berkeley National Laboratory (USA), and on the free electron laser from Helmholtz-Zentrum Dresden-Rossendorf (Germany).

Read more on the LNLS website

Image: Experimental scheme showing the far infrared beam illuminating a metallic atomic force microscopy tip (nano-antenna) for the nanospectroscopy experiment. Infrared radiation is confined to the apex of the tip in a region of 25 nm