Optical and microwave bidirectional signal conversion metasurface and communication system based on the same

Abstract

The application discloses a kind of light and microwave bidirectional signal conversion metasurface and the communication system based on the metasurface, metasurface includes metasurface unit array, first feed network and second feed network, metasurface unit includes dielectric substrate, and front resonant structure and back resonant structure respectively located in the front and back of dielectric substrate;Array along x direction in the same row of front resonant structure in series, and different rows of front resonant structure along y direction are connected in parallel by first feed network;Array along x direction in the same row of back resonant structure in series, and different rows of back resonant structure along y direction are connected in parallel by second feed network;When microwave polarized along x direction is irradiated to the front of metasurface, realize the forward conversion of microwave signal to optical signal;When microwave polarized along y direction is irradiated to the front of metasurface, realize the reverse conversion of optical signal to microwave signal.The application realizes light and microwave bidirectional signal conversion.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical microwave technology, in particular to an optical and microwave bidirectional signal conversion metasurface and a communication system based on the metasurface. BACKGROUND

[0002] The energy and information conversion between light and microwave has important application prospects in modern electronic communication and quantum physics. The exchange platform of light and microwave not only can connect the microwave domain and the light domain, but also can make full use of the advantages of microwave and light wave in different propagation media to realize seamless cross-media transmission, which is a promising solution for the future realization of space-air-ground-sea integrated information network. Due to the huge frequency span of light and microwave, efficient light and microwave interaction is facing severe challenges. In recent years, methods such as optical fiber technology, plasma cavity, nonlinear material, nanomechanical coupling can realize microwave to light conversion. However, many verified schemes are realized based on optical fiber and circuit technology, and need external power supply to perform multiple intermediate processes, which undoubtedly increases the cost, power consumption and system complexity, greatly limits its wireless application in free space. In addition, these conversion devices are difficult to further develop to realize the reverse process of light to microwave, so there are many limitations.

[0003] The metasurface is a two-dimensional structure composed of artificially designed subwavelength units, which can control the wave properties in free space with high resolution. By designing the unit structure, many different functions have been realized on the metasurface, which can collect radio frequency energy with microwave and manipulate the propagation characteristics of microwave with light wave, which lays a new research direction for designing energy and information conversion platform between light and microwave. In recent years, many metasurface structures based on the interaction of light and microwave have been proposed for information transmission, but the metasurfaces studied at present are difficult to realize the bidirectional conversion of light and microwave at the same time and do not depend on external power supply. Therefore, how to use metasurfaces to construct a bidirectional conversion platform of light and microwave that does not depend on external power supply for energy and signal conversion is still a difficult problem. SUMMARY

[0004] The present application relates to the field of optical microwave technology, in particular to an optical and microwave bidirectional signal conversion metasurface and a communication system based on the metasurface.

[0005] Another object of the present application is to provide a communication system based on the above-mentioned metasurface.

[0006] Technical solution: The light and microwave bidirectional signal conversion metasurface provided by the application comprises m*n array-arranged double-sided metasurface units, a first feed line network and a second feed line network, the double-sided metasurface unit comprises a dielectric substrate, and a front resonant structure and a back resonant structure located on the front and back of the dielectric substrate respectively; the front resonant structures in the same row arranged along the x direction in the array are connected in series, and the front resonant structures in different rows arranged along the y direction are connected in parallel through the first feed line network and then connected to both ends of a laser diode; the back resonant structures in the same row arranged along the x direction in the array are connected in series, and the back resonant structures in different rows arranged along the y direction are connected in parallel through the second feed line network;

[0007] When the microwave polarized along the x direction is irradiated to the front of the metasurface, the microwave is effectively absorbed by the front resonant structure and rectified into direct current energy to drive the laser diode to emit light, realizing the forward conversion of the microwave signal to the optical signal; when the microwave polarized along the y direction is irradiated to the front of the metasurface, the microwave transmits through the front resonant structure and the dielectric substrate and reaches the back resonant structure, and by adjusting the light irradiation intensity of the photodiode loaded on the back resonant structure, the reflection amplitude of the incident microwave can be flexibly regulated, and the reverse conversion of the optical signal to the microwave signal is realized.

[0008] Preferably, the front resonant structure comprises three metal strips arranged along the x axis direction, the first and second metal strips are connected through a Schottky diode, and the second and third metal strips are connected through an inductor; after the metal strips of the adjacent double-sided metasurface units in the array along the x direction are connected in series, both ends are connected to the first metal strip and the second metal strip of the first feed line network.

[0009] Preferably, the back resonant structure comprises two spaced metal sheets and a photodiode loaded between the two spaced metal sheets, the upper row of metal sheets of the adjacent double-sided metasurface units in the array along the x direction are connected in series and then connected to the third metal strip of the second feed line network, and the lower row of metal sheets are connected in series and then connected to the fourth metal strip of the second feed line network, so that all the photodiodes are connected in parallel.

[0010] Preferably, the back resonant structure further comprises a resistor, the resistor is loaded in parallel with the photodiode between the two spaced metal sheets, and is used for constructing a charging and discharging circuit.

[0011] Preferably, the two spaced metal sheets are two identical metal copper sheets.

[0012] Preferably, the first feeding network comprises a first metal strip, a second metal strip, a first feeding line and a second feeding line, the first metal strip and the second metal strip are arranged on the front surface of the dielectric substrate, the first feeding line and the second feeding line are arranged on the back surface of the dielectric substrate, the first metal strip and the second metal strip are connected with the first feeding line and the second feeding line through two metal vias respectively, and the first feeding line and the second feeding line are connected with the positive and negative electrodes of the laser diode respectively.

[0013] Preferably, the second feeding network comprises a third metal strip and a fourth metal strip, and the third metal strip and the fourth metal strip are arranged on the back surface of the dielectric substrate.

[0014] Preferably, the material of the dielectric substrate has a relative dielectric constant of 2.65, a loss tangent of 0.001, and a thickness of 2.0 mm.

[0015] The communication system based on the light-microwave bidirectional signal conversion metasurface comprises a light-microwave bidirectional signal conversion metasurface, a microwave end transmitter and a microwave end transceiver located on the front surface side of the metasurface, and a laser end receiver and a laser end transmitter located on the back surface side of the metasurface.

[0016] In the forward conversion transmission link from the microwave signal to the light signal, the to-be-transmitted signal is encoded onto the BASK microwave signal by the microwave end transmitter to drive and modulate the metasurface, so as to rectify and generate a green OOK laser signal, and the generated OOK laser signal is further demodulated into a digital baseband signal by the laser end receiver, and finally the to-be-transmitted signal is recovered.

[0017] In the reverse conversion transmission link from the light signal to the microwave signal, the to-be-transmitted signal is first converted into a data bit stream, encoded onto the underwater green OOK laser signal by the laser end transmitter, and irradiates the photodiode on the back surface of the metasurface; then, the reflection amplitude response of the metasurface is quickly changed; at this time, when the microwave end transceiver emits y-polarized microwave to the front surface of the metasurface, the BASK microwave signal obtained by reflection is received by the microwave end transceiver, and is demodulated into a digital baseband signal by a software defined radio platform, so as to recover the video content.

[0018] Further, the light-microwave bidirectional signal conversion metasurface, the microwave end transmitter and the microwave end transceiver are located in the air, and the laser end receiver and the laser end transmitter are located in the water, so as to realize the bidirectional full-duplex capability across the air and the water.

[0019] Beneficial effects: Compared with the prior art, the significant technical effects of the present application are: integrating the Schottky diode and the photodiode on the double-sided metasurface unit, realizing the bidirectional conversion of optical signals and microwave signals, and being able to inversely regulate the reflection amplitude of the incident microwave through the intensity of the optical signal. In addition, the metasurface composed of the metasurface unit can be used to construct a bidirectional communication system based on laser OOK and microwave BASK modulation. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Front view of the metasurface of the present application;

[0021] Figure 2 Back view of the metasurface of the present application;

[0022] Figure 3 Overall structure of the metasurface of the present application;

[0023] Figure 4 Metasurface unit structure of the present application;

[0024] Figure 5 Back resonant structure of the metasurface unit structure in an embodiment of the present application;

[0025] Figure 6 Reflection amplitude diagram of the metasurface unit structure of the present application under different working modes;

[0026] Figure 7 Green laser power output measured under different incident microwave powers;

[0027] Figure 8 Microwave reflection amplitude measured under different power green laser irradiations;

[0028] Figure 9 Principle diagram of the bidirectional hybrid communication system of the present application;

[0029] In the figure: 1, dielectric substrate; 2, front resonant structure; 3, back resonant structure; 21, metal strip; 22, Schottky diode; 23, inductor; 31, metal sheet; 32, photodiode; 33, resistor; 41, first metal strip; 42, second metal strip; 43, first feed line; 44, second feed line; 51, third metal strip; 52, fourth metal strip; 6, laser diode. DETAILED DESCRIPTION

[0030] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0031] Previous platforms for converting light to microwaves were mostly based on optical fiber and circuit technology, requiring external power supplies to perform multiple intermediate steps. This increased cost, power consumption, and system complexity, significantly limiting their applications in free-space wireless applications. Furthermore, these conversion devices were difficult to further develop to achieve the reverse process from light to microwaves, resulting in numerous limitations.

[0032] Based on the above problems, the present invention provides a metasurface for bidirectional signal conversion between light and microwaves. First, a double-sided metasurface unit is designed. The unit integrates components such as Schottky diodes and photodiodes and has two front and back sides. Through careful design, it produces different responses when facing microwave irradiation with different polarization directions. When an x-polarized incident wave is irradiated, it will be absorbed by the metasurface unit structure and rectified into DC energy to generate an optical signal. When a y-polarized incident wave is irradiated, its reflection amplitude will change with the intensity of light on the photodiode. Multiple identical metasurface units are used to form an array to form a metasurface for bidirectional signal conversion between light and microwaves. By utilizing the above-mentioned metasurface for bidirectional signal conversion between light and microwaves, bidirectional conversion of optical signals to microwave signals can be realized in free space without battery power, and the reflection phase of the incident microwave can be regulated by light, thereby constructing a metasurface platform for bidirectional signal conversion between light and microwaves.

[0033] Figure 1 and Figure 2 The front and back sides of the optical and microwave bidirectional signal conversion metasurface are shown respectively. Figure 3 The overall structure of the metasurface is shown. Figure 4 The metasurface unit structure is shown. Figures 1 to 3 As shown, the metasurface for forward conversion and reverse regulation of microwaves and light includes m×n identical metasurface units, where m and n are the number of rows and columns of the metasurface units, respectively; and also includes a first feeder network and a second feeder network.

[0034] like Figure 4 As shown, the double-sided metasurface unit includes a dielectric substrate 1, and a front resonant structure 2 and a back resonant structure 3 located on the front and back of the dielectric substrate 1 respectively; the front resonant structure 2 includes: three sections of metal strips 21 arranged along the x-axis direction, the first and second sections of the metal strips are connected by a Schottky diode 22, and the second and third sections of the metal strips are connected by an inductor 23. Figure 1As shown, the metal strips of the adjacent double-sided metasurface units in the array are connected in series in the x direction, and the two ends are connected to the first metal strip 41 and the second metal strip 42 of the first feed network, respectively. Among them, the metal strip 21 is used to absorb the incident microwave energy and provide a current transmission path, the Schottky diode 22 is used to rectify the incident microwave energy into direct current energy, and the inductor 23 is used to connect adjacent metal strips, reduce electromagnetic coupling, and filter out alternating current signals.

[0035] As shown in Figure 4 , the back resonant structure 3 includes two spaced metal sheets 31 and a photodiode 32 loaded between the two spaced metal sheets, which is used to receive different incident light intensities and generate capacitance changes to adjust the microwave reflection amplitude. As shown in Figure 2 , the upper row of metal sheets 31 of the adjacent double-sided metasurface units in the array are connected in series and connected to the third metal strip 51 of the second feed network, and the lower row of metal sheets 31 are connected in series and connected to the fourth metal strip 52 of the second feed network, so that all photodiodes 32 are connected in parallel, which can enable all photodiodes of the entire metasurface to share voltage simultaneously when only the light intensity of one photodiode is regulated.

[0036] The loading of the Schottky diode and the photodiode in the metasurface unit can directly serve as a platform for forward conversion and reverse regulation of microwave and light information energy, and does not depend on external power supply. On the one hand, it can convert incident microwave signals into direct current and generate light signals, realizing the conversion from microwave signals to light signals. On the other hand, it can also change the reflection amplitude of the microwave by the incident light signal, simultaneously realizing the conversion from light signals to microwave signals.

[0037] As shown in Figure 5 , as an optional solution, a resistor 33 can also be loaded between the two spaced metal sheets 31, which is connected in parallel with the photodiode 32, used to build a charging and discharging circuit to obtain a higher response rate.

[0038] As shown in Figure 1 and Figure 2 , the first feed network includes a first metal strip 41, a second metal strip 42, a first feed line 43 and a second feed line 44, the first metal strip 41 and the second metal strip 42 are arranged on the front surface of the dielectric substrate 1, the first feed line 43 and the second feed line 44 are arranged on the back surface of the dielectric substrate 1, the first metal strip 41 and the second metal strip 42 are connected to the first feed line 43 and the second feed line 44 through two metal vias, respectively, to provide positive and negative poles of direct current energy, and the first feed line 43 and the second feed line 44 are connected to the positive and negative poles of the laser diode 6, respectively. The second feed network includes a third metal strip 51 and a fourth metal strip 52, and the third metal strip 51 and the fourth metal strip 52 are arranged on the back surface of the dielectric substrate 1.

[0039] The Schottky diode 22 and the photodiode 32 integrated in the metasurface unit are key elements. Unlike other diodes, the Schottky diode contains a metal semiconductor MS junction, has the advantages of low forward voltage drop and fast switching speed, and is very suitable for rectification. The Schottky diode 22 in the embodiment serves as a tuning element to complete the rectification process. When laser irradiation is applied to the photodiode, the photodiode will absorb energy and generate a capacitance change according to the photoelectric capacitance effect, thereby affecting the microwave resonance characteristics of the metasurface unit. In this case, the reflected microwave amplitude is related to the intensity of the incident laser.

[0040] In the embodiment of the application, the metal strip 21 is a copper strip, the two spaced metal sheets 31 are two identical copper sheets, and the photodiode 32 is loaded at the gap between the two copper sheets along the x direction.

[0041] The relative dielectric constant of the dielectric substrate 1 is 2.65, the loss tangent is 0.001, and the thickness is 2.0 mm.

[0042] The side length of the metasurface unit is 15.0 mm.

[0043] The forward conversion process of the microwave signal to the optical signal and the reverse conversion process of the optical signal to the microwave signal use cross-polarization modes of x polarization and y polarization, respectively, to minimize coupling and interference.

[0044] In the embodiment, m = 10 and n = 20, and 200 identical metasurface units are arranged to form a light and microwave bidirectional signal conversion metasurface. For microwave incidence polarized along the x direction, the front resonant structure 2 serves as a resonant element, the metal strip 21 fully absorbs the incident microwave energy, and the Schottky diode 22 converts the incident microwave energy into direct current energy to generate an optical signal. For microwave incidence polarized along the y direction, the microwave energy passes through the front resonant structure 2 and the dielectric substrate 1 and reaches the back resonant structure 3, which serves as a resonant element. By adjusting the illumination intensity of the photodiode loaded on the back resonant structure 3, the reflection amplitude of the incident microwave can be flexibly controlled, and the reverse conversion of the optical signal to the microwave signal can be realized.

[0045] In the embodiment, the HSMS-2860 Schottky diode and the Panasonic "S13773" PIN photodiode are used to form the metasurface unit.

[0046] Figure 6The reflection amplitude maps of the metasurface unit structure in two working modes are shown. It can be clearly observed that when the incident x-polarized microwave drives the Schottky diode to be in the "on" state, the metasurface unit produces a sharp resonance at about 4.00 GHz, indicating that the incident microwave energy is well absorbed. The absorbed microwave energy can be further rectified by the Schottky diode to drive the laser diode to emit light to generate an optical signal, thereby realizing the forward conversion from microwave to laser. Under y-polarized microwave incidence, the metasurface unit produces a resonant response, and as the incident laser power increases from 0 to 21.6 mW, the resonant frequency moves from 4.45 GHz to 3.92 GHz. At these two resonant frequencies, an amplitude difference of about 10 dB and 14 dB in the two reflection states can be achieved, thereby achieving good reverse regulation of laser to microwave.

[0047] Figure 7 The measured green laser power output under different incident microwave powers is shown. The input microwave power refers to the microwave power fed into the transmitting horn antenna at 4.06 GHz. When the input x-polarized microwave power reaches 14 dBm (25 mW), the laser diode has been lit, and the output laser power is 2.7 mW. The microwave-to-laser conversion efficiency is calculated to be 10.8%. When the input microwave power increases to 24 dBm (250 mW), the output laser power reaches 16.2 mW, and the conversion efficiency is 6.48%.

[0048] Figure 8 The measured y-polarized microwave reflection amplitude under different power green laser irradiation is shown. When the irradiated laser power varies between 0 and 21.6 mW, the metasurface exhibits significantly different reflection amplitudes under y-polarized microwave incidence, with a difference of 14 and 9 dB at 3.92 and 4.45 GHz, respectively. The measurement results are in good agreement with the simulation results, verifying the effective regulation of laser to microwave.

[0049] The present application also provides a light and microwave bidirectional hybrid communication system based on the metasurface. The switching of laser intensity corresponds to two different microwave intensities, indicating that on-off keying (OOK) laser signals and binary amplitude shift keying (BASK) microwave signals can be used to modulate and transmit digital symbols "1" and "0". The system can transmit information through microwave and recover the information through the generated laser demodulation; at the same time, it can also transmit information through laser to regulate microwave and recover the information through demodulation. Thus, two data (for example, two different videos) can be converted and transmitted independently and simultaneously through the same metasurface to realize bidirectional communication.

[0050] The super surface can be used to construct a light and microwave bidirectional communication system under a battery-free condition, and provide an effective solution for cross-medium information transmission under a future space-air-ground-sea integrated information network.

[0051] Figure 9 The principle of a bidirectional hybrid communication system constructed by the light and microwave bidirectional signal conversion super surface provided by the embodiment of the present application is shown. The full-duplex microwave laser hybrid wireless communication system spans two media of air and water, and mainly includes a microwave end transmitter, a microwave end transceiver, a super surface, a laser end receiver and a laser end transmitter. The microwave end transmitter and the microwave end transceiver are located on the front side of the super surface, and the laser end receiver and the laser end transmitter are located on the back side of the super surface; the microwave end transmitter is composed of a software-defined radio platform (NI USRP-2954), a power amplifier and an x-polarized horn antenna, and is used for transmitting an amplified BASK signal. In the microwave end transceiver, a feed antenna (i.e. a y-polarized horn antenna) is connected with a microwave generator to transmit a y-polarized microwave signal, and the reflected BASK microwave signal is received by the y-polarized horn antenna and transmitted to the software-defined radio platform connected with a computer for post-processing. The laser end transmitter includes a field programmable gate array (FPGA) and a green laser diode, and is used for generating an OOK laser signal with modulation information. The laser end receiver includes a high-speed and high-sensitivity photoelectric detection and demodulation circuit, and the signal is post-processed by a computer.

[0052] In order to show the bidirectional full-duplex capability of the constructed microwave laser hybrid wireless communication system in cross-medium communication, a video image transmission is taken as an example for demonstration, as shown in Figure 9 In the forward conversion transmission link from the microwave signal to the laser signal, a video (stars twinkling) is first converted into a data bit stream, encoded onto the BASK microwave signal by the microwave end transmitter, used to drive and modulate the super surface, so as to generate a green OOK laser signal; the generated OOK laser signal passes through the underwater, is received by the photoelectric detection and demodulation circuit, and is further demodulated into a digital baseband signal by the laser end receiver, so that the video content is finally recovered. In the reverse conversion transmission link from the laser signal to the microwave signal, a video (lotus blooming) is first converted into a data bit stream, encoded onto the underwater green OOK laser signal by the laser end transmitter, and irradiates the photodiode on the back side of the super surface; then, the reflection amplitude response of the super surface is quickly changed; at this time, when the microwave end transceiver transmits the y-polarized microwave to the front side of the super surface, the obtained BASK microwave signal is received by the y-polarized horn antenna, and is demodulated into a digital baseband signal by the software-defined radio platform, so that the video content is recovered.

[0053] The light and microwave bidirectional signal conversion metasurface provided by the embodiment of the present application can directly complete the bidirectional conversion of the light signal and the microwave signal without relying on an external power supply, can realize the energy conversion from the microwave to the light, and can realize the regulation of the reflected signal of the light to the microwave, thereby providing an effective solution for the cross-medium information transmission under the future space-air-ground-sea integrated information network.

[0054] The specific features, structures, materials or characteristics described in the embodiments or examples of the present application are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above-mentioned terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

Claims

1. A metasurface for bidirectional signal conversion between light and microwaves, characterized in that: The invention comprises m×n double-sided metasurface units arranged in an array, a first feeder network, and a second feeder network. The double-sided metasurface units comprise a dielectric substrate (1), and a front resonant structure (2) and a back resonant structure (3) respectively located on the front and back sides of the dielectric substrate (1); the front resonant structures (2) arranged in the same row along the x direction in the array are connected in series, and the front resonant structures (2) arranged in different rows along the y direction are connected in parallel via the first feeder network and then connected to both ends of the laser diode; the back resonant structures (3) arranged in the same row along the x direction in the array are connected in series, and the back resonant structures (3) arranged in different rows along the y direction are connected in parallel via the second feeder network. When microwaves polarized along the x-direction irradiate the front side of the metasurface, the microwaves will be effectively absorbed by the front resonant structure (2) and rectified into DC energy to drive the laser diode (6) to emit light, thereby realizing the forward conversion of microwave signals to optical signals; when microwaves polarized along the y-direction irradiate the front side of the metasurface, the microwaves will pass through the front resonant structure (2) and the dielectric substrate (1) and reach the back resonant structure (3). By adjusting the light intensity of the photodiode loaded on the back resonant structure, the reflection amplitude of the incident microwave can be flexibly controlled, and the reverse conversion of the optical signal to the microwave signal can be realized.

2. The optical and microwave bidirectional signal conversion metasurface according to claim 1, characterized in that: The front resonant structure (2) includes three metal strips (21) arranged along the x-axis direction, the first and second metal strips are connected via a Schottky diode (22), and the second and third metal strips are connected via an inductor (23); after the metal strips of adjacent double-sided metasurface units in the x-direction in the array are connected in series, the two ends are respectively connected to the first metal strip (41) and the second metal strip (42) of the first feeder network.

3. The optical and microwave bidirectional signal conversion metasurface according to claim 1, characterized in that: The back resonant structure (3) includes two spaced metal sheets (31) and a photodiode (32) loaded between the two spaced metal sheets. The upper row of metal sheets of adjacent double-sided metasurface units in the x-direction of the array are connected in series and are all connected to the third metal strip (51) of the second feeder network. The lower row of metal sheets are connected in series and are all connected to the fourth metal strip (52) of the second feeder network, so that all photodiodes (32) are connected in parallel.

4. The optical and microwave bidirectional signal conversion metasurface according to claim 3, characterized in that: The back-surface resonant structure (3) further includes a resistor (33), which is connected in parallel with the photodiode (32) and loaded between two spaced metal sheets (31) to construct a charge-discharge circuit.

5. The optical and microwave bidirectional signal conversion metasurface according to claim 3, characterized in that: The two spaced-apart metal sheets (31) are two identical metal copper sheets.

6. The optical and microwave bidirectional signal conversion metasurface according to claim 1, characterized in that: The first feeder network comprises a first metal strip (41), a second metal strip (42), a first feeder (43) and a second feeder (44); the first metal strip (41) and the second metal strip (42) are arranged on the front side of the dielectric substrate (1); the first feeder (43) and the second feeder (44) are arranged on the back side of the dielectric substrate (1); the first metal strip (41) and the second metal strip (42) are respectively connected to the first feeder (43) and the second feeder (44) through two metal through holes; the first feeder (43) and the second feeder (44) are respectively connected to the positive and negative electrodes of the laser diode (6).

7. The optical and microwave bidirectional signal conversion metasurface according to claim 1, characterized in that: The second feeder network comprises a third metal strip (51) and a fourth metal strip (52), and the third metal strip (51) and the fourth metal strip (52) are arranged on the back side of the dielectric substrate (1).

8. The optical and microwave bidirectional signal conversion metasurface according to claim 1, characterized in that: The dielectric substrate (1) has a relative dielectric constant of 2.65, a loss tangent of 0.001, and a thickness of 2.0 mm.

9. A communication system based on the optical and microwave bidirectional signal conversion metasurface according to any one of claims 1 to 8, characterized in that: include: A metasurface for bidirectional optical and microwave signal conversion, a microwave transmitter and a microwave transceiver located on the front side of the metasurface, and a laser receiver and a laser transmitter located on the back side of the metasurface; In the forward conversion transmission link from microwave signals to optical signals, the signal to be transmitted is encoded onto a BASK microwave signal through the microwave transmitter to drive and modulate the metasurface, thereby rectifying and generating a green OOK laser signal. The generated OOK laser signal is further demodulated into a digital baseband signal by the laser receiver, and finally the signal to be transmitted is recovered. In the reverse conversion transmission link from optical signals to microwave signals, the signal to be transmitted is first converted into a data bit stream, encoded onto an underwater green OOK laser signal by the laser-end transmitter, and illuminates the photodiode on the back of the metasurface; then, the reflection amplitude response of the metasurface is rapidly changed; at this time, when the microwave-end transceiver transmits y-polarized microwaves to the front of the metasurface, the reflected BASK microwave signal is received by the microwave-end transceiver and demodulated into a digital baseband signal through the software-defined radio platform, thereby restoring the video content.

10. The communication system according to claim 9, wherein: The optical and microwave bidirectional signal conversion metasurface, microwave transmitter and microwave transceiver are located in the air, and the laser receiver and laser transmitter are located in the water, achieving bidirectional full-duplex capability across the two media of air and water.

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