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Reimagining the optical diode effect

22.03.2024 - New material shows a large nonreciprocal absorption of light depending on the direction of light propagation.

At the heart of global internet connectivity, form an indispensable foundation. Key to this foundation are optical isolators, created by combining multiple components. The result is a complex structure that transmits light in only one direction, to prevent damage to lasers and minimize noise by avoiding the reversal of light. However, some magnetic materials have an optical diode effect – an unconventional nonreciprocal absorption of light manifested by the material itself. This effect leads to a change in transmittance depending on the direction in which the light travels. If this phenomenon can be enhanced, it is expected that optical isolators can be made more compact and efficient.

 

A team of researchers led by Kenta Kimura of the Graduate School of Engineering at Osaka Metro­politan University investigated the phenomenon of non­reciprocal optical absorption in the magneto­electric antiferromagnet LiNiPO4 at shortwave infrared wavelengths. Their results showed that the absorption coefficient differs by a factor of two or more when the direction of light propa­gation is reversed. This large non­reciprocal absorption is attributed to the magnetic properties of the divalent nickel ions. Furthermore, the researchers have shown that it is possible to switch the optical diode effect with an applied magnetic field in a non-volatile manner.

“The optical diode effect is an interesting subject of study because it is such an uncon­ventional phenomenon that is far removed from common sense and has the potential to realize unexpected appli­cations. However, there are still many problems at present, such as the low operating temperatures,” explained Kenta Kimura. “Never­theless, this research has demonstrated the usefulness of compounds containing nickel, which has greatly expanded the scope of material selection. Based on this knowledge, we will continue the development of materials exhibiting a higher performance optical diode effect.” (Source: Osaka Met. U.)

Reference: K. Kimura & T. Kimura: Nonvolatile Switching of Large Nonreciprocal Optical Absorption at Shortwave Infrared Wavelengths, Phys. Rev. Lett. 132, 036901 (2024); DOI: 10.1103/PhysRevLett.132.036901

Link: Dept. of Materials Science, Osaka Metropolitan University, Osaka, Japan

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