Research on the zoom metalenses related to wavelength and refractive index in terahertz band

A transmission-type and polarization-insensitive metalenses are designed in the terahertz band based on the theory of phase propagation and the wavefront of electromagnetic wave is controlled by optimizing the cross-shaped elliptical pillar meta-unit, The metalenses use Silicon as the atom unit material and Polymer as the substrate material. The radius of the metalenses is 11 mm, the incident frequency is 0.4 THz, the numerical aperture is 0.69, and the efficiency of focus is 51.4%. Furthermore, metalenses exhibit the proportional relation between the focal length and the surrounding refractive index of 1–1.6, and inversely proportional relation between the focal length and the incident band of 0.7∼0.8 mm, these results validate the designed metalenses have a zoom function.