Dynamic phase assembled terahertz metalens for reversible conversion between linear polarization and arbitrary circular polarization

Abstract

If a metalens integrates the circular polarization (CP) conversion function, the focusing lens together with circular-polarizing lens (CPL) in traditional cameras may be replaced by a metalens. However, in terahertz (THz) band, the reported metalenses still do not obtain the perfect and strict single-handed CP, because they were constructed via Pancharatnam-Berry phase so that CP conversion contained both left-handed CP (LCP) and right-handed CP (RCP) components. In this paper, a silicon based THz metalens is constructed using dynamic phase to obtain single-handed CP conversion. Also, we can rotate the whole metalens at a certain angle to control the conversion of multi-polarization states, which can simply manipulate the focusing for incident linear polarization (LP) THz wave in three polarization conversion states, including LP without conversion, LCP and RCP. Moreover, the polarization conversion behavior is reversible, that is, the THz metalens can convert not only the LP into arbitrary single-handed CP, but also the LCP and RCP into two perpendicular LP, respectively. The metalens is expected to be used in advanced THz camera, as a great candidate for traditional CPL and focusing lens group, and also shows potential application in polarization imaging with discriminating LCP and RCP.

All-dielectric terahertz metasurfaces with dual-functional polarization manipulation for orthogonal polarization states

“…Excitingly, metasurfaces constructed from artificially engineered subwavelength-scale elements exhibit unprecedented capabilities for the regulation of electromagnetic waves, leading to surging interest in such field from more and more researchers. 11–20 Compared with conventional waveplates, metasurfaces can directly change the amplitude, phase, and polarization of the outgoing waves by adjusting the size of the elements within the subwavelength thickness, confirming the flexibility and practicality of the metasurface design. Therefore, many terahertz polarization devices based on metasurfaces have been proposed and exhibit novel physical phenomena, including focusing, 21–25 holography, 26–29 spin-to-orbit angular momentum conversion, 30,31 waveplates 32–36 and beam steering.…”

Creating Longitudinally Varying Vector Vortex Beams with an All‐Dielectric Metasurface

“…Metasurfaces have developed rapidly in recent years, and can manipulate electromagnetic wave parameters including frequency, amplitude and phase by designing subwavelength structures. [18][19][20][21][22] These capabilities offer great potential in metalens, [23][24][25] sensing, [26,27] holography, [28] and vortex generators [15,17] applications. Based on the ability of these subwavelength arrays to control the light field, polarization conversion [29,30] and versatile polarization generation [31] have been proposed.…”

Metasurface‐Assisted Wireless Communication with Physical Level Information Encryption

“…Metasurfaces, 2D artificial structures composed of judiciously engineered subwavelength inclusions, have showcased exotic abilities to arbitrarily manipulate the amplitude, phase and polarization of electromagnetic (EM) waves in both transmission and reflection geometries. [ 1 , 2 , 3 , 4 ] Many intriguing physical phenomena and devices have emerged based on metasurface techniques, such as invisibility cloaks, [ 5 , 6 ] wave plates, [ 7 ] imaging systems, [ 8 , 9 ] and other functional devices. [ 10 , 11 , 12 , 13 ] Moreover, by introducing active materials or components such as graphene, phase‐change material, and electrically driven diode/varactor into metasurfaces, [ 14 , 15 , 16 , 17 , 18 ] it becomes possible to dynamically realize versatile EM responses via external control, thus eliciting an inevitable transition from static to dynamic wavefront tailoring for advancing the field forward.…”