Arbitrarily Directional Polarization Rotation with Metals

Significance 

Technological advances in the optical field have led to the development of polarization resonators with numerous applications in different fields such as fiber communications and electronics. Currently, optical integration has never been achieved fully by the polarization of optical devices due to their bulky nature. Alternatively, research has shown that two-dimensional arrays based ultrathin metasurfaces are promising candidates for developing new applications. Consequently, this has attracted significant attention of researchers due to its capability of enabling efficient design of waveplates with the ability to initiate the conversion between circular and linear polarization. In line with the aforementioned advances, an efficient technique for manipulating and controlling light is highly desirable. In another published literature, additional degrees of freedom for controlling light have been achieved through dynamic tuning. Among the available tuning methods, a polarization rotator comprising of two rotating polarizers have been widely preferred. Unfortunately, the increasing complexity in the operation of the systems has hindered the realization of the desired functions.

Recently, a team of Nanjing Tech University researchers from Department of Physics: Dr. Cheng-Ping Huang, Dr. Yong Zhang and Dr. Yu-lin Wang in collaboration with Dr. Ling-bao Kong at Beijing Technology and Business University designed and developed a tunable plasmonic polarization rotating system. In particular, the system was designed by two perforated metal screens separated by a subwavelength distance to initiate free rotation of the polarization direction of the polarized electromagnetic waves. Their research work is currently published in the research journal, Physical Review Applied.

Briefly, the research work entailed a cross-examination of the tunable polarization rotation mechanism, which results from the near-field coupling between the rectangular holes and hole dimers perforated, respectively, in the two metal screens. Next, the modulation of the far-field radiations produced by the two orthogonal electric components was achieved by translating one of the metal screens laterally. Eventually, the polarization rotation effects were demonstrated in a microwave band to find out whether it is applicable for high frequencies.

The authors observed that by polarizing the incident wave along the x-axis, it was easy to realize the arbitrary rotation of the transmitted polarization with a nearly linear polarization state. The theoretical and experimental results exhibited a continuous polarization rotation of the outgoing wave from -900 to 900. This was attributed by displacing the metal screen a few millimeters and thus, also leading to high efficiency in the entire polarization rotation range. On the other hand, it was worth noting that the effects of the tunable polarization rotation could be extended to an application requiring high frequencies. Furthermore, the response time with respect to the mechanical displacement significantly influenced the modulation speed of the system.

In summary, the study proved useful for numerous applications with the desired efficiencies and also at comparatively high frequencies ranges especially through the wavelength and structural sizes scaling. This is due to the dependence of the electromagnetic properties of most materials on the polarization effects. The study may even be extended to the optical range with the development of advanced nano control methods.

Reference

Huang, C., Zhang, Y., Wang, Y., & Kong, L. (2018). Arbitrarily Directional and Tunable Polarization Rotating Effect with Coupled Metal Screens. Physical Review Applied, 10(6).

Go To Physical Review Applied

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