Controlling asymmetric transmission phase in planar chiral metasurfaces

Metasurfaces with ultrathin artificial structures have attracted much attention because of their unprecedented capability in light manipulations. The recent development of metasurfaces with controllable responses opens up new opportunities in various applications. Moreover, metasurfaces composed of twisted chiral structures can generate asymmetric responses for opposite incidence, leading to more degrees of freedom in wave detections and controls. However, most past studies had focused on the amplitude responses, not to mention using bi-directional phase responses, in the characterization and light manipulation of chiral metasurfaces. Here, we report a birefringent interference approach to achieve a controllable asymmetric bi-directional transmission phase from planar chiral metasurface by tuning the orientation of the metasurface with respect to the optical axis of an add-on birefringent substrate. To demonstrate our approach, we fabricate planar Au sawtooth nanoarray metasurface and measure the asymmetric transmission phase of the metasurface placed on a birefringent sapphire crystal slab. The Au sawtooth metasurface-sapphire system exhibits large oscillatory behavior for the asymmetric transmission phase with the tuning parameter. We confirm our experimental results by Jones matrix calculations using data obtained from full-wave simulations for the metasurface. Our approach in the characterization and light manipulation of metasurfaces with controllable responses is simple and nondestructive, enabling new functionalities and potential applications in optical communication, imaging, and remote sensing.

Terahertz Metamaterial Modulator Based on Phase Change Material VO2

In this paper, a new type of terahertz (THz) metamaterial (MM) modulator has been presented with bifunctional properties based on vanadium dioxide (VO2). The design consists of a VO2 resonator, polyimide substrate, frequency selective surface (FSS) layer, and VO2 film. Based on the metal-insulator transition (MIT) of VO2, this structure integrated with VO2 material can achieve the dynamic modulation on both transmission and reflection waves at 2.5 THz by varying the electrical conductivity value of VO2. Meanwhile, it also exhibits adjustable absorption performance across the whole band from 0.5–7 THz. At the lower conductivity (σ = 25 S/m), this structure can act as a bandpass FSS, and, at the high conductivity (σ = 2 × 105 S/m), it behaves like a wideband absorber covering 2.52–6.06 THz with absorption A > 0.9, which realizes asymmetric transmission. The surface electric field distributions are illustrated to provide some insight into the physical mechanism of dynamic modulation. From the simulated results, it can be observed that this design has the capability of controlling tunable manipulation on both transmission/reflection responses at a wide frequency band. This proposed design may pave a novel pathway towards thermal imaging, terahertz detection, active modulators, etc.

Construction of Space Quantum Information System Based on Satellite Recognition

Satellite identification is a form of space quantum information, which refers to the use of artificial earth satellites as the transmitting station between earth communication stations to perform satellite identification to construct a space quantum information system. However, at this stage, a single form of identification cannot meet the needs of various aspects such as the development of the information society. And mobile broadband services. Based on this, this paper has carried out research on the construction of space quantum information system based on satellite recognition. This paper firstly introduces the research significance of space quantum information transmission based on satellite identification, and then analyzes the research status of space information system based on satellite identification and the research status of space quantum information system based on satellite identification at home and abroad. Aiming at the problem of asymmetrical transmission of space information, this paper proposes, a spatial asymmetric transmission scheme based on layered modulation and network coding, and in view of the low communication quality caused by the influence of weather and surrounding environment on the space-based communication channel, this paper proposes an adaptive transmission scheme of spatial information based on satellite cooperation. The survey results show that under the MNC strategy and the traditional zero-padded strategy, the end-to-end bit error rate performance of S2 is not much different. As the signal-to-noise ratio continues to increase to 30dB, the two are basically the same. In the whole range of k value, the access probability of the MNC strategy is equal to a constant 0.67 and remains unchanged. When k=1, under the OUS scheme, it shows that the two source nodes have the same probability of accessing the channel, and the access probability is 50%, which is 16.7% lower than that of the MNC scheme.