Near-infrared thermally modulated varifocal metalens based on the phase change material Sb2S3

Focus-tunable metalenses play an indispensable role in the development of integrated optical systems. In this paper, the phase change material Sb2S3 is used in a thermally modulated varifocal metalens based on PB-phase for the first time. Sb2S3 not only has a real part of refractive index shift between the amorphous and crystalline state but also has low losses in both amorphous and crystalline states in the near-infrared region. By switching Sb2S3 between the two states, a metalens doublet with a variable focal length is proposed. Moreover, the full width at half maximum of each focal point is close to the diffraction limit. And the focusing efficiency can be over 50% for the two focal points. Together with the advantage of precise thermal control, the proposed metalens has great potential in the application of multi-functional devices, biomedical science, communication and imaging. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

This paper introduces a focus-tunable metalens based on the phase change material Sb2S3, which has low losses and refractive index shift characteristics between the amorphous and crystalline states, enabling variable focal length with excellent focusing efficiency and focal point width performance.