US NRL demonstrates ways to improve optical efficiency of nanophotonic devices


Physicists at the US Naval Research Laboratory (NRL) have demonstrated ways to improve optical efficiency in nanophotonic devices.

Made up of hexagonal boron nitride (hBN), nanophotonic devices are used in ultra-high resolution microscopes, solar energy harvesting, optical computing, and targeted medical therapies.

NRL Electronics Science and Technology Division research physicist Dr Alexander J. Giles said: “The applications for this research are considerably broad.”

“By confining light to very small dimensions, nanophotonic devices have direct applications for use in ultra-high resolution microscopes, solar energy harvesting, optical computing and targeted medical therapies.”

Hexagonal boron nitride (hBN) forms an atomically thin lattice consisting of boron and nitrogen atoms, the US Navy stated.

The hBN was found to have the ability to support deeply sub-diffractional hyperbolic phonon polaritons that can be used for applications such as sub-diffractional optical imaging (so-called ‘hyperlensing’), energy conversion, chemical sensing, and quantum nanophotonics, however, limited transmission efficiencies continue to persist.

Giles added: “We have demonstrated that the inherent efficiency limitations of nanophotonics can be overcome through the careful engineering of isotopes in polar semiconductors and dielectric materials.”

According to the Navy, naturally occurring boron has two isotopes, boron-10 and boron-11, lending to a 10% difference in atomic masses.

The difference results in substantial losses due to phonon scattering, limiting the potential applications of this material.

A team of researchers at NRL has engineered greater than 99% isotopically pure samples of hBN which consist almost entirely of either boron-10 or boron-11 isotopes.

Scientists from the University of California San Diego, Kansas State University, Oak Ridge National Laboratory, Columbia University, and Vanderbilt University supported the research.

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