HIT News(School of Electronics and Information Engineering / text)Recently, HIT’s research team spearheaded by associate professor Zhang Kuang and professor Wu Qun, working hand in hand with foreign scholars, made important breakthroughs in the basic research field of multifunctional modulationof electromagnetic waves on metasurfaces. A general phase control method based on chirality-assisted geometric-phase metasurfacesis proposed, which can independently modulatequadruplex polarization channels, thus realizing full-field utilization of output energy.These research findings were published in Nature Communications, entitling Independent phase modulation for quadruplex polarization channels enabled by chirality-assisted geometric-phase metasurfaces. Here is the link: https://doi.org/10.1038/s41467-020-17773-6.
Metasurface is a two-dimensional planar structure composed of subwavelength quasi-periodic elements, which can realize manual control of electromagnetic wave amplitude, phase, polarization and frequency characteristics. With the maturity of processing technology, metasurface have been widely used in many fields such as optical lenses, imaging systems, radar cross section reduction, wireless communication systems, biomedical treatment and diagnosis, etc.
Geometric phase is one of the most direct methods to control circularly polarized waves. However, in practical applications, the metasurfacebased on geometric phase cannot utilize the co-polarized component in the exit field, which means that 50% of the electromagnetic energy is not utilized and half of the polarized channels are idle, greatly limiting the development of transmission channels in wireless systems.
Aiming at this defect, the research group figured out a general method of multi-dimensional decoupling of internal coherence between circularly polarized transmission channels by introducing chirality-assisted phase into metasurface design, thus realizing independent phase control of all circularly polarized channels. Based on this general method, vortex metasurfaces carrying four different orbital angular momentum numbers are designed. The multiple design of the polarization state of the incident wave further verifies the high utilization rate of the metasurface to the output energy and the stability of the orthogonal polarization function in the output field. The design scheme can be propagated to other frequency bands and reproduced by changing structures or materials. At the same time, it provides a brand-new idea for many fields such as multifunctional wavefront integrated devices, multiplexed channel transmission systems, reconfigurable antenna design, spin selective optics research, etc.