Metamaterials are artificial materials that use subwavelength micron/nano structural units to control the polarization, amplitude and phase of electromagnetic waves. Polarization control is an important research direction of metamaterials. Most of the metamaterials that realize broadband polarization control are based on decoupled resonance mechanism, which has succeeded in wideband reflective devices. However, the limitations of the resonance mechanism make it difficult to generalize to wideband transmission devices. A small amount of minority of metamaterials that can realize the function of wideband transmission wave plate have different cross sections, which is difficult to be realized by common micro-nano processing technology.
In the latest study, Prof. Lin Chen’s group, from Optoelectronic Devices and Integration Division of Wuhan National Lab for Optoelectronics, proposes to use the additional phase imparted by multiple beam interference to manipulate the overall transmission phase so as to achieve a nearly flat phase difference over a wide spectral range. Broadband metamaterial devices, such as quarter-wave plates, which require the constant maintenance of the phase difference of the transmitted waves over a wide spectral range, can be constructed. As an example, a general strategy is established to build high-performance broadband WPs by introducing MBI to manipulate the transmission-phase dispersion for anisotropic MTMs. The cross-polarization phase difference dispersion can be cancelled out by specifically designing the geometrical parameters of the anisotropic MTMs to generate an additional positive or negative phase shift for the two orthogonal polarization directions, thanks to the contribution of constructive or destructive interference. As a proof-of-concept demonstration, anisotropic MTMs made by metal and dielectric multilayers with large birefringent indexes are designed to enable a flat cross-polarization phase difference in the microwave/terahertz/infrared bands. The circular polarization to the transformation of linear polarization is almost entirely (DoLP>0.95) within the relative operation bandwidth of 12.0%, 13.6%, and 35.8%. The study provides a new method for constructing broadband and efficient optical devices with different wavebands and different types of metamaterials.
This work titled as "Multiple-beam interference-enabled Broadband Metamaterial Wave Plates" has been recently published in Physical Review Applied. The research was supported by the National Natural Science Foundation of China (11674118, 11474116, 11574226, 11674068, and 11734007), Natural Science Foundation of Jiangsu Province (BK20170058), National Basic Research Program of China (2017YFA0303504), Shanghai Science and Technology Committee (16JC1403100), and State Key Laboratory of Advanced Technology for Materials Synthesis and Processing (Wuhan University of Technology).
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https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.044042
