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AUSTRALIAN physicists have found a way to confine electromagnetic energy and stop it from leaking away, which could lead to new laser technology and be used in quantum computers.
A fundamental tenet of electrodynamics is that accelerated charges create electromagnetic radiation.
But the team led by Dr Andrey Miroschnichenko from the Australian National University Research School of Physics and Engineering, sought to understand why atoms are stable: why do the orbiting electrons not radiate away?
According to the new theory, the absence of radiation is the result of the current being divided between two different components, a conventional electric dipole and a toroidal dipole (associated with poloidal current configuration), which produce identical fields at a distance.
If these two configurations are out of phase then the radiation will be cancelled out.
Dr Miroshnichenko, in collaboration with colleagues from Germany and Singapore, successfully tested his new theory with a single silicon nanodisc between 160 and 310 nanometres in diameter and 50 nanometres high. He successfully cancelled the disc’s scatter of visible light, effectively rendering it invisible.
According to Dr Miroschnichenko, radiation is described in two different ways, mathematically speaking: one is based on Cartesian multipoles and the other on vector spherical harmonics used in a Mie basis set.
The researchers were trying to figure out why these two models gave different answers, then realised the Cartesian description was missing the toroidal components, which could be a very significant factor.
The ability to confine electromagnetic radiation could be important in the development of tiny lasers on the surface of materials, called spasers, and also in the creation of efficient X-ray lasers by high-order harmonic generation.