The phenomenon of totally eliminated backscattering in a hypothetical magnetic sphere is called Kerker effect. 

One of the most generalizations is the lattice Kerker effect in periodic structures. By varying one of the array periods, the electric dipole surface lattice resonance (ED-SLR) of the array and the magnetic dipole resonance (MDR) of single nanoparticles can be spectrally overlapped, leading to strong suppression of reflection or backward scattering from the array as a whole. 

A research group led by Dr. LI Guangyuan from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences realized active tuning of the lattice Kerker effect by introducing a metasurface composed of germanium-antimony-tellurium (GeSbTe or GST) nanorods. 

The study was published in Journal of Physics D: Applied Physics on Jan. 25. 

GST is a typical phase-change material that can be switched between amorphous and crystalline phases with many unique merits, especially the nonvolatile, rapid and reversible switching characteristics. 

In this study, the researchers realized transition from the ED-SLR to the lattice Kerker effect by changing the GST crystalline fraction. Since the ED-SLR and the lattice Kerker effect correspond to near-unity and suppressed reflection, respectively, this transition leads to multilevel tuning of reflection, transmission and absorption with modulation depths above 86%. 

In addition, the team also made use of MDR redshifts and achieved broadband and multilevel tuning of transmission with modulation depth of 87% over a broadband range of 588 nm. 

"The proposed GST metasurface featuring nonvolatile, rapid and reversible transition from ED-SLR to the lattice Kerker effect will find intriguing applications in reconfigurable directional scattering, all-optical modulation and switching," said Dr. LI. 

When GST changes from amorphous to crystalline phase, a transition from the ED-SLR to the lattice Kerker effect occurs, resulting in the switching from high reflection to high transmission. (Image by SIAT)