Spinning Lightwaves on a One-Way Street

Illustration of an interface of mirror symmetric gyrotropic media. (Source: de Gruyter)

Researchers at Purdue University have created a quantum spin wave for light. This can be a carrier of information for future nano­technologies but with a unique twist: they only flow in one direc­tion. Information tech­nologies at the nanoscale rely on mani­pulating particles such as electrons and photons. The electron, which is the carrier of charge, is a fermion while the photon, which is the long-distance transmitter of information, is a boson. The most important difference between a fermion and a boson is literally how they spin.

Even though electron spin is widely utilized in commercial nano­technologies such as magnetic memories, optical spin has only recently become a fundamental degree of freedom in nano­photonics with possible appli­cations in fiber optics, plasmonics, resonators and even quantum metrology. This explosion of research into optical spin is due to the remarkable features of strongly confined electro­magnetic waves. At the nanoscale, spin and direction of motion of light are intrinsically locked to one another.

The researchers used many designs to achieve this behavior, in particular, an interface of mirror symmetric gyrotropic media. Gyrotropy is a form of material response to light waves that transfer spinning behavior of electrons to photons. “Our research opens up the possi­bility of new appli­cations where devices communi­cate information in one direction but block it completely in the reverse. This is important for the safe functioning of high power devices as well as for reducing inter­ference between transmitted/received electro­magnetic signals from cellphone antennas,” said Zubin Jacob. (Source: de Gruyter)

Reference: T. van Mechelen et al.: Unidirectional Maxwellian spin waves, Nanophot. 8, 1399 (2019); DOI: 10.1515/nanoph-2019-0092

Link: Birck Nanotechnology Center, School of Electrical and Computer Engineering, Purdue University, West Lafayette, USA

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