Near-infrared thermally modulated varifocal metalens based on the phase change material Sb<sub>2</sub>S<sub>3</sub>
Shuai Qin, Ning Xu, Hui Huang, Kaiqian Jie, Hongzhan Liu, Jianping Guo, Hongyun Meng, Faqiang Wang, Xiangbo Yang, Zhongchao Wei
Abstract
Focus-tunable metalenses play an indispensable role in the development of integrated optical systems. In this paper, the phase change material Sb 2 S 3 is used in a thermally modulated varifocal metalens based on PB-phase for the first time. Sb 2 S 3 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 Sb 2 S 3 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.