Image source: Advanced Science News
Writer: you and your colleagues
01 reading guidance
Recently, academician Cui Tiejun of Southeast University, together with Professor Qiu Chengwei of National University of Singapore and Professor Luo Yu of Nanyang University of technology of Singapore, designed and implemented a kind of digital programmable electromagnetic super surface driven by light. The phase distribution of microwave reflection can be adjusted in real time by using visible light.
This technology can effectively realize microwave stealth, electromagnetic illusion and dynamic vortex wave generation. 02 background
Hypersurface is a two-dimensional artificial structure composed of periodic or quasi periodic subwavelength elements, which can manipulate electromagnetic waves flexibly.
Dynamic hypersurface is a kind of hypersurface with tunable characteristics, which can be used to construct electromagnetic devices with reconfigurable or programmable functions and realize advanced multi-functional systems. At present, the main methods of designing dynamic hypersurfaces include electrical control, temperature control and optical control. A typical way to create a dynamic hypersurface in the microwave band is to use a positive intrinsic negative (PIN) diode or a varactor diode. This method usually uses a large number of wires, bulky power supply and complex control circuit to drive the hypersurface, and the external equipment must be connected with the hypersurface through the wires, which will increase the volume of the system, and also introduce the crosstalk between DC and microwave signals. The team not only abandoned the traditional electrical control methods, but also integrated multiple PIN photodiode based optical sensor networks behind the well-designed varactor based optical drive array, overcoming the shortcomings of the existing optical control methods (narrow working band, single control direction), and successfully designed and implemented a digital optical driven programmable electromagnetic super surface.
Figure 1: schematic diagram of digital programmable hypersurface platform driven by light
Compared with the traditional electronic control device, the new programmable super surface device has the advantages of light weight, compact structure and wireless control. In addition, the device can use the intensity of visible light to control the microwave phase, which provides a new technical scheme for the development of advanced photoelectric hybrid devices.
Table 1 Comparison between traditional and new adjustable super surface devices
03 innovation research
Figure 2 implementation of subarray and performance simulation of hypersurface element
3.1 the structure shows that the optical driven programmable super surface device consists of both sides.
The front optical drive array is shown in Fig. 3a, which is composed of 6x6 optical drive sub arrays as shown in Fig. 2H. Each such optical drive sub array is composed of 4x4 sub wavelength broadband super surface units (as shown in Fig. 2b).
The optical sensor network on the back is shown in Fig. 3b, which is composed of 6x6 optical sensor subnetworks as shown in Fig. 2G. Each such optical sensor subnetwork is composed of 22 PIN photodiodes in series.
The front side of the optical drive sub array corresponds to the back side of the optical sensor sub network one by one, and is connected through a metal through hole. The top bias line of the optical drive sub array is connected with the negative electrode of the optical sensor sub network, and the bottom bias line of the optical drive sub array is connected with the positive electrode of the optical sensor sub network.
The output voltage of PIN photodiode is controlled by the intensity of incident light, so the bias voltage of optical drive sub array is also controlled by the intensity of incident light.
Fig. 3 front view and
Photo and performance test system of back optical sensor network
Fig. 4 structure description
The top of the Supersurface unit shown in Fig. 2b is composed of two symmetrical hollow patches, which are respectively connected with the offset lines at the top and bottom. The hollow patches are connected by varactor diodes.
So the equivalent capacitance of the super surface element can be realized by adjusting the capacitance of the embedded varactor, and the capacitance of the varactor can be adjusted by the bias voltage loaded on the bias line.
Based on the principle of RLC equivalent circuit, the resonance characteristic of the super surface element is analyzed. As shown in Figure 2c, the resonance characteristic (microwave reflection phase) of the super surface element is controlled by the capacitance of the varactor diode, and can be adjusted by changing the bias voltage on the bias line.
Therefore, the microwave response of each optical drive sub array can be independently controlled by the corresponding light source intensity.
3.2 work flow when visible light irradiates a certain optical sensor sub network behind the super surface device, the PIN photodiode in the optical sensor sub network can convert the different illumination intensity of the incident light into different voltage, and load it on the bias line of the corresponding optical drive sub array directly facing the device through the electrical through hole, so as to change the varactor diode in the optical drive sub array The capacitance.
Thus, the resonance state of the super surface element in the optical drive sub array can be adjusted remotely.
When the incident is the visible light pattern with different intensity, the voltage generated by the optical sensor sub network with different intensity is also different, and then the complex microwave reflection phase distribution is generated by controlling the whole optical drive array to realize the functions of microwave external stealth, electromagnetic illusion and dynamic vortex beam generation. 04 application example
Figure 5 application example of optical driven programmable super surface device
In application, the optical driven programmable hypersurface device can realize the functions of microwave external stealth, electromagnetic illusion and dynamic vortex beam generation.
As shown in Fig. 5A and Fig. B, after the reflection phase of the super surface is compensated, the above object can be hidden.
At the same time, by properly designing the phase distribution, the electromagnetic illusion effect as shown in Fig. 5 C and D can be realized, and the low-order OAM mode as shown in Fig. 5 e, F, G and h can be generated.
This article was published in nature electronics, a sub Journal of nature, entitled "an optically driven digital measurement for programming electronic functions". Zhang Xinge, a doctoral student of Southeast University, is the first author of the paper. The corresponding authors are Professor Jiang Weixiang, Professor Cui Tiejun of Southeast University and Professor Qiu Chengwei of National University of Singapore.
To apply for reprint, please add wechat: 447882024
Coming soon
New issue: Light: advanced manufacturing
New issue: elight
Coming soon!
Editor: Zhao Yang. Source: light academic publishing center, Changchun Institute of Optics and mechanics, Chinese Academy of Sciences. Statement: if the video, picture and text used in this article involve copyright issues, please inform us at the first time. We will confirm the copyright according to the supporting materials you provide and pay the remuneration according to the national standards or delete it immediately. Email: guosq@ciomp.ac.cn