New Artificial Nanostructures for Infrared Absorption Technologies

Recently, researchers in Bengaluru’s Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), an autonomous institute of the Department of Science and Technology, have demonstrated for the first time infrared light emission and absorption with Gallium nitride (GaN) nanostructures. The development could lend itself to multiple useful applications.

Context: GaN, a widely used material for blue light emission, is one of the most advanced semiconductors. Though visible and ultraviolet light applications of GaN have already been realized, with LEDs and laser diodes commercially available, utilization of GaN for IR light harvesting or development of GaN-based IR optical elements is lacking.

Key Highlights: Though blue light emission from GaN has been known for some time (it is used in LEDs), this is the first time that infrared light-matter interactions are demonstrated in GaN.

• For this demonstration, the scientists utilized a scientific phenomenon called surface polariton excitations in GaN nanostructures that lead to light-matter interactions at IR spectral range.
• Surface polaritons are special modes of electromagnetic waves traveling at the interface of a conductor and an insulator such as air.
• By altering the morphology and shape of the nanostructures, they are also able to excite plasmon polaritons in GaN, which results in extending the light-matter coupling to further reaches of the electromagnetic spectrum. These polaritons are quasi-particles which have both light and matter characteristics.
• To grow these GaN nanostructures, the researchers utilized a specialized material deposition instrument called molecular beam epitaxy. This instrument uses ultra-high vacuum, similar to the conditions of outer space, to grow high-quality material nanostructures with dimensions about 100000 times smaller than the width of a human hair.

Significance: The recent development demonstrates a novel pathway for utilizing GaN in infrared nanophotonic applications. The infrared surface polariton excitations can be translated to many other semiconductors as well.

• This work will help in addressing the demand for IR sources and detectors for energy, defence technologies, security, imaging, and other applications.