Polarization-independent silicon-based electrically-controlled terahertz metasurface modulator based on Anapile resonance

Abstract

The invention discloses a polarization independent silicon-based electric control terahertz metasurface modulator based on Anapile resonance. The device comprises a high-resistance silicon substrate, and a doping layer is formed on the front surface of the high-resistance silicon substrate in an ion implantation mode; a metal pattern structure composed of a first metal electrode, a metal metasurface, a metal connecting line and a second metal electrode is processed on the surface of the doping layer in a Schottky contact mode; the metal metasurface is characterized in that metasurface units are densely laid and arranged on a plane according to crystal lattices, and each metasurface unit is composed of an outer contour defined by four boundary metal lines, two internal diagonal metal lines connected with vertexes and a semi-capacitor formed by breaking at the midpoint of each boundary metal line. Every two adjacent metasurface units are attached and spliced through a boundary metal wire to form a complete metal wire and a capacitor gap. According to the terahertz metasurface modulator, modulation of terahertz waves is achieved through the Anapile metasurface, and compared with an existing electronic control terahertz metasurface modulator, the terahertz metasurface modulator has the advantages of being low in insertion loss, wide in modulation dynamic range and irrelevant to polarization.

Description

Technical Field

[0001] The invention belongs to the field of terahertz communication, and in particular relates to a polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance. Background Art

[0002] Terahertz wave communication has the characteristics of large bandwidth and high carrier frequency. Compared with microwave and millimeter wave wireless communication, it can provide faster communication rate and larger communication capacity. At the same time, the wavelength of terahertz wave is shorter than that of microwave wave, and its transceiver antenna is smaller in size, has better directivity and less channel interference. At present, terahertz communication technology has demonstrated excellent data transmission rate in the frequency band of 0.1-10THz, providing a cutting-edge solution for the construction and upgrading of future communication networks.

[0003] In terahertz communication systems, in order to achieve efficient signal transmission, we usually need to modulate low-frequency signals to the terahertz frequency band. To this end, the development of high-performance terahertz modulators has become one of the key technologies. Terahertz modulators can be implemented in the form of photonic crystals, phase change material films, metasurfaces, etc. Among them, metasurface technology uses fine micro-nanostructure design to accurately control the response characteristics of the metasurface to terahertz waves. Furthermore, different control methods can effectively change the physical properties of the metasurface such as dielectric constant and conductivity, thereby dynamically changing its modulation effect on terahertz waves. Compared with other modulation schemes, metasurface modulators have shown significant advantages. It not only allows the carrier frequency to be flexibly adjusted according to specific application scenarios, but also greatly promotes the miniaturization and lightweight of the system due to its small size and highly integrated characteristics.

[0004] At present, terahertz metasurface modulators are mainly realized by temperature control and light control. Terahertz temperature-controlled metasurface modulators can achieve a large modulation dynamic range, but their performance is limited by the low modulation speed. Terahertz light-controlled metasurface modulators can also achieve a large modulation dynamic range, and have a relatively higher modulation speed compared to temperature-controlled modulation schemes, but usually require high-power ultrashort pulse lasers as excitation light sources. They have high power consumption and low integration, which makes it difficult to meet the needs of practical applications. Electrically controlled terahertz metasurface modulators usually change the carrier concentration in semiconductor materials by applying an external electric field, thereby affecting the response of the metasurface to terahertz waves. Compared with light control and temperature control schemes, electrically controlled terahertz metasurface modulators usually have the advantages of high modulation speed, low power consumption, and high integration. However, the existing electrically controlled terahertz metasurface modulators have large insertion losses, and the materials and processes usually used are incompatible with conventional CMOS standard processes, resulting in high manufacturing costs. At the same time, the metal feed lines used in the existing structures greatly limit the degree of freedom of the metasurface shape, which not only hinders the further application of some relatively novel metasurface design ideas in electrically controlled metasurface modulators, but also makes most electrically controlled metasurface modulators polarization-dependent, which is not conducive to their application in the field of communications. In addition, the ubiquitous static current also hinders the further reduction of power consumption. These unfavorable factors have made it difficult to further improve the performance of electrically controlled terahertz metasurface modulators.

[0005] The paper "A Broadband Terahertz Metamaterial Electrical Modulator" proposes a scheme to control the junction depth of the Schottky junction formed between the split ring resonator (SRRs) array and doped GaAs on a GaAs substrate through a voltage signal, thereby controlling the split ring resonator array's response to terahertz waves. This scheme achieves a modulation of the transmittance in the range of 6.3% to 31.4% at a frequency of 0.81THz, with a modulation dynamic range (the modulation dynamic range is the difference between the highest and lowest values ​​of the transmittance) of about 25% and an insertion loss of about 70%. However, the design adopted by this scheme has polarization dependence and a large insertion loss.

[0006] Patent CN112987345A proposes a polarization-insensitive terahertz modulator and its preparation method. This solution uses a high electron mobility transistor, a pair of open bow-shaped metamaterial structures and corresponding power feeders to realize an electrically controlled terahertz metasurface modulator that is insensitive to terahertz waves in polarization directions x and y, and achieves modulation of transmittance in the range of 60% to 4.2% at 0.22THz. Its modulation dynamic range is about 56% and its insertion loss is about 40%. However, this solution is not a completely symmetrical design, and there is a lack of verification of polarization independence in polarization directions other than x and y. At the same time, this solution also has a large insertion loss.

[0007] In summary, the main disadvantages of existing electrically controlled transmission terahertz metasurface modulators are:

[0008] First, the materials and processes used are not compatible with conventional CMOS standard processes, and the manufacturing cost is high.

[0009] Second, the modulation performance is relatively limited, the modulation dynamic range is relatively small, and the insertion loss is relatively high.

[0010] Third, the designs of most devices are polarization-dependent, which limits their applications in the communications field.

[0011] Fourth, there is a large static current and the power consumption is large. Summary of the invention

[0012] The purpose of the present invention is to solve the above technical problems existing in the electrically controlled transmission terahertz metasurface modulator in the prior art, and to provide a polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance. The present invention aims to propose a metasurface structure design scheme based on a silicon-based substrate, which modulates terahertz waves by voltage signals, has a high modulation dynamic range, low insertion loss, low power consumption, and has polarization-independent properties.

[0013] The specific technical solutions adopted by the present invention are as follows:

[0014] A polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance, comprising a high-resistance silicon substrate, and a doping layer is formed on the front side of the high-resistance silicon substrate by ion implantation;

[0015] The surface of the doped layer is processed with a metal pattern structure consisting of a first metal electrode, a metal supersurface, a metal connecting wire, and a second metal electrode, and Schottky contact is formed between the metal pattern structure and the doped layer; the first metal electrode is a square ring with a single-side opening, and is arranged on the periphery of the square outline of the metal supersurface in a three-sided surrounding manner, and the second metal electrode is located on the side of the metal supersurface that is not surrounded by the first metal electrode; the first metal electrode and the metal supersurface are kept at a distance and are not in contact, and the second metal electrode and the metal supersurface are connected by a series of metal connecting wires;

[0016] The metal metasurface is formed by densely paving metasurface units on a plane according to a square lattice, the outer contour of the square lattice of each metasurface unit is surrounded by four boundary metal wires, and two internal metal wires connecting the diagonal vertices of the square are arranged along two diagonals of the outer contour respectively; each boundary metal wire is disconnected at the midpoint to form a semi-capacitive gap, and the semi-capacitive gap is composed of two plate metal sheets that are separately arranged at the midpoint disconnection and maintain a gap with each other; two adjacent metasurface units are bonded and spliced ​​together through their respective boundary metal wires to form a complete metal wire, and the semi-capacitive gaps on the two bonded and spliced ​​boundary metal wires are also spliced ​​together to form a complete capacitive gap, so that two adjacent metasurface units in the metal metasurface are electrically connected and have the same electric potential.

[0017] The working frequency range of the present invention is 0.1THz-5THz.

[0018] Preferably, the high-resistance silicon substrate is an n-type silicon substrate, and its resistivity is greater than 10 kΩ·cm.

[0019] Preferably, the front side of the high-resistance silicon substrate is n-doped by injecting phosphorus element to form a doped layer.

[0020] Preferably, the doping concentration of the doping layer is 10 15 ~10 16 cm -3 .

[0021] Preferably, the metal pattern structure is a composite metal layer, with a lower layer of titanium and an upper layer of gold.

[0022] Preferably, the metal pattern structure on the doping layer is formed by photolithography development-magnetron sputtering-stripping steps.

[0023] Preferably, after the metal pattern structure is processed, the thickness of the high-resistance silicon substrate needs to be adjusted to a target design value by chemical mechanical polishing so that the Anapole resonance frequency coincides with the substrate FP transmission peak frequency.

[0024] Preferably, the second metal electrode is arranged parallel to one side of the metal super surface, and the metal connecting wires connecting the two are arranged at equal intervals.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention realizes the modulation of terahertz waves through the Anapole metasurface unit, and has the characteristics of low insertion loss and wide modulation dynamic range compared with the existing electrically controlled terahertz metasurface modulator.

[0027] The present invention uses a fully connected symmetrical metasurface without using a feed line, which has the characteristic of being polarization-independent compared to the existing electrically controlled terahertz metasurface modulator.

[0028] The present invention reduces the generation of static current by forming Schottky contacts at two metal electrodes, thereby reducing power consumption compared to existing electrically controlled terahertz metasurface modulators.

[0029] The present invention can flexibly apply the solution to a wider frequency band by scaling the metasurface unit and adjusting the capacitor gap size and substrate thickness, and has good scalability.

[0030] The materials and manufacturing processes used in the present invention have better CMOS process compatibility than the existing electrically controlled terahertz metasurface modulators. In addition to terahertz metasurface modulators, the metasurface supporting Anapole resonance used in the present invention has application potential in absorbers, material detection, and nonlinear effect generation due to its characteristics of near-field enhancement and far-field radiation disappearance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of a polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance; (a) is a schematic diagram of the overall structure; (b) is a planar schematic diagram of the metal pattern;

[0032] Figure 2 Schematic diagram of the structure of the metasurface unit in the modulator; (a) is a single metasurface unit; (b) is the splicing method between adjacent units, the current mode under the incidence of y-polarized electromagnetic waves, and a complete capacitor gap diagram;

[0033] Figure 3 This is a device manufacturing process flow chart of the electrically controlled terahertz metasurface modulator of the present invention. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0035] In the description of the present invention, it is to be understood that when an element is considered to be "connected" to another element, it may be directly connected to the other element or indirectly connected, that is, there are intermediate elements. On the contrary, when an element is said to be "directly" connected to another element, there are no intermediate elements.

[0036] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinguishing descriptions, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0037] In a preferred embodiment of the present invention, a polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance is provided, which includes a high-resistance silicon substrate 1, and a doping layer 2 is formed on the front side of the high-resistance silicon substrate 1 by ion implantation.

[0038] See also Figure 1 As shown in (a) and (b) in the figure, the surface of the doped layer 2 is processed with a metal pattern structure composed of a first metal electrode 3, a metal super surface 4, a metal connecting line 5 and a second metal electrode 6, and Schottky contact is formed between the metal pattern structure and the doped layer 2. The first metal electrode 3 is a square ring with a single opening, and the so-called square ring with a single opening means that one side of the square ring originally formed by four sides is missing, forming a single-sided opening. The first metal electrode 3 with a single opening is arranged on the periphery of the square outline of the metal super surface 4 in a three-sided surrounding manner, and the three sides of the first metal electrode 3 are respectively parallel to the three sides of the square outline of the metal super surface 4. The three sides of the metal super surface 4 are surrounded by the first metal electrode 3, but there is one side that is not surrounded by the first metal electrode 3, and the second metal electrode 6 is located on the side of the metal super surface 4 that is not surrounded by the first metal electrode 3, and a certain distance is maintained between the second metal electrode 6 and the metal super surface 4. The first metal electrode 3 and the second metal electrode 6 are spaced apart from each other and are not in contact with each other. The first metal electrode 3 and the metal supersurface 4 are spaced apart from each other and are connected to the second metal electrode 6 and the metal supersurface 4 through a series of metal connecting wires 5. The second metal electrode 6 is arranged parallel to one side of the metal supersurface 4, and the metal connecting wires 5 connecting the second metal electrode 6 and the metal supersurface 4 are arranged at equal intervals.

[0039] Also, see Figure 2As shown in (a), the metal supersurface 4 is composed of supersurface units arranged in a plane according to a square lattice, and each supersurface unit completely occupies a square lattice. The square lattice outer contour of each supersurface unit is surrounded by four boundary metal wires, specifically the first boundary metal wire 4.1, the second boundary metal wire 4.2, the third boundary metal wire 4.3, and the fourth boundary metal wire 4.4 in the figure. The four boundary metal wires are connected end to end to form an outer contour, and two internal metal wires connecting the diagonal vertices of the square are arranged along two diagonal lines in the outer contour, namely the first internal metal wire 4.9 and the second internal metal wire 4.10 in the figure. Each boundary metal wire is disconnected at the midpoint to form a half-capacitance gap, and the first boundary metal wire 4.1, the second boundary metal wire 4.2, the third boundary metal wire 4.3, and the fourth boundary metal wire 4.4 are respectively provided with a first half-capacitance gap 4.5, a second half-capacitance gap 4.6, a third half-capacitance gap 4.7, and a fourth half-capacitance gap 4.8. Among them, each half-capacitor gap is composed of two plate metal sheets that are separated at the midpoint and maintain a gap between each other. The plate metal sheets have been processed at both ends of the gap at the midpoint of the boundary metal line in a way that faces the inside of the outer contour. The plate metal sheets are rectangular and their long sides are perpendicular to the boundary metal line.

[0040] Since all metasurface units are densely arranged in a square lattice on a plane, the unit structure of the metasurface has good symmetry, ensuring that the response of the metasurface to terahertz waves is polarization-independent. Figure 2 As shown in (b), two adjacent supersurface units are joined and spliced ​​through their respective boundary metal lines to form a complete metal line; at the same time, the half-capacitor gaps on the two joined and spliced ​​boundary metal lines are also spliced ​​to form a complete capacitor gap; thus, a complete capacitor gap includes a first complete plate metal sheet 11 and a second complete plate metal sheet 12 as capacitor gap plates, and the gap 13 between the two is composed of the original two gaps. After all supersurface units are arranged continuously, electrical connections can be formed between adjacent supersurface units in the metal supersurface 4, and the electrical connection between adjacent units in this way can ensure that all supersurface units have the same electric potential.

[0041] When the capacitor gap is disconnected, the metal metasurface will support Anapole resonance at a certain frequency. Anapole resonance is a resonance caused by destructive interference between electric dipoles and circular dipoles excited in the scatterer. This resonance has a suppressed far-field radiation and a relatively enhanced near-field. Since the far-field radiation is suppressed, under the Anapole resonance, the metal metasurface will exhibit approximately transparent properties to the incident wave, which is beneficial to reducing the insertion loss; at the same time, since the near field is greatly enhanced, the interaction between the electric field and the working material will also be enhanced, which is beneficial to improving the modulation dynamic range. In the metasurface unit of this scheme, the capacitor gap can be regarded as a pair of electric dipoles, and as Figure 2 As shown in (b), its current distribution forms a circular dipole, which produces destructive interference and forms an Anapole resonance. By scaling the metasurface unit and adjusting the width and length of the capacitor gap, we can move the Anapole resonance to any position in the spectrum. Since the metal metasurface exhibits transparent characteristics under the Anapole resonance, the reflectivity and transmittance of the entire device will be determined only by the substrate. If the Anapole resonance frequency coincides with the substrate FP transmission peak frequency (which can be achieved by controlling the substrate thickness), a transmissive terahertz metasurface modulator with a small insertion loss will be obtained.

[0042] When the above device is working, a differential modulation voltage is applied to the two metal electrodes, namely the first metal electrode 3 and the second metal electrode 6. When the potential of the second metal electrode 6 is low, a depletion region will be formed near the metal metasurface, which has a low conductivity, which will cause the capacitor gap in the metal metasurface unit structure to be disconnected, forming an anapole resonance. When the potential of the second metal electrode 6 is high, an accumulation region will be formed near the metal metasurface, which has a high conductivity, which will cause the capacitor gap in the metal metasurface unit structure to be turned on, destroying the anapole resonance. Since all metal semiconductor contacts in the present invention are Schottky contacts, the device of the present invention has a very small static current, which greatly reduces the static power consumption of the terahertz modulator.

[0043] It should be noted that the above Figure 1 and Figure 2Only the overall structure of the device is shown, and the size parameters of each component can be reasonably optimized according to the actual performance requirements. The Anapole resonance can be moved to different terahertz frequency points by changing the device size. For example, if the size of the entire device (including the size of the metasurface pattern and the thickness of the substrate) is reduced to half of the original, an Anapole resonance can be formed near a frequency point twice the original resonance frequency. The Anapole resonance is robust to changes in geometric parameters. Small changes in geometric parameters will not lead to the direct disappearance of the Anapole resonance, but will cause the frequency point where the Anapole resonance is located to shift. Under the existing micro-nano processing technology, by adjusting the geometric parameters of the device, the device can achieve terahertz wave modulation in the range of 0.1THz-5THz.

[0044] The material selection in the above device can be designed and selected with reference to the prior art. Among them, the high-resistance silicon substrate 1 is preferably an n-type silicon substrate with a resistivity greater than 10 kΩ·cm. The front side of the high-resistance silicon substrate 1 is preferably n-type doped by injecting phosphorus to form a doping layer 2. The doping concentration of the doping layer 2 is preferably 10 15 ~10 16 cm -3 The metal pattern structure is preferably a composite metal layer, with a lower layer of titanium and an upper layer of gold. The metal pattern structure on the doping layer 2 can be formed by photolithography development-magnetron sputtering-stripping steps. After the high-resistance silicon substrate 1 is processed with the metal pattern structure, if the thickness of the high-resistance silicon substrate 1 does not meet the requirements, the thickness can be adjusted to the target design value by chemical mechanical polishing.

[0045] The performance of the polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance under different size parameters is demonstrated below through different embodiments.

[0046] Example 1

[0047] In this embodiment, the specific structure of the polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance is as follows: Figure 1 and Figure 2 As shown, no further details will be given. The following only describes its specific dimensions and processing technology. Figure 3 As shown, the processing of the device is as follows:

[0048] The high-resistance silicon substrate 1 is of n-type, and its resistivity is greater than 10 kΩ·cm. First, an n-type doping layer 2 is formed on the high-resistance silicon substrate 1 by ion implantation, and the doping element is phosphorus, and the doping concentration is 5×10 15 cm -3. Then, a metal pattern structure is formed on the doped layer 2 through the steps of photolithography development-magnetron sputtering-stripping, including a first metal electrode 3, a metal super surface 4, a metal connecting line 5, and a second metal electrode 6. Among them, the magnetron sputtering step first deposits 20nm thick titanium, and then deposits 150nm thick gold. Finally, the back of the high-resistance silicon substrate 1 is ground and polished by chemical mechanical polishing to be thinned to 225um.

[0049] In this embodiment, the lattice constant of the supersurface, that is, the outer contour side length of the supersurface unit, is 100um. Among them, the width of all metal lines in the spliced ​​metal supersurface 4 is 8um (for the 4 boundary metal lines at the boundary of each unit, the width is 4um, and the adjacent units are spliced ​​to obtain a metal line with a width of 8um, and the two internal metal lines that cross inside the unit have a width of 8um). At the same time, in the complete capacitor gap formed by splicing two half-capacitor gaps, the long sides of the first complete electrode metal sheet 11 and the second complete electrode metal sheet 12 are both 16um, and the short sides are both 4um. The complete capacitor gap 13 formed in this way is 16um long and 2um wide. In the entire metal supersurface 4, the supersurface array size is 30×30, containing 900 supersurface units.

[0050] In addition, the first metal electrode 1 has a width of 250um, a distance of 250um from the metal metasurface 4, and surrounds the metasurface structure on three sides. The second metal electrode 2 has a width of 250um, a distance of 250um from the metal metasurface 4, and a length of 2900um. It is connected to the metal metasurface through 29 8um wide metal connecting wires 5, and the 29 metal connecting wires are arranged at equal intervals.

[0051] Based on the polarization-independent silicon-based electrically controlled terahertz metasurface modulator designed in this embodiment, when the modulation voltage is -8V, for the y-polarized normal incident wave with a frequency of 0.4THz, the simulation results show that its transmittance is as high as 80%. When the modulation voltage is +8V, for the y-polarized normal incident wave with a frequency of 0.4THz, the simulation results show that its transmittance is less than 35%. Its modulation dynamic range exceeds 45%, and the insertion loss is as low as 20%. At the same time, for incident waves of other polarizations (30°, 60° to the y direction, x-polarization, left-hand circular polarization, right-hand elliptical polarization), the simulation results show that the frequency domain characteristic curve of its transmittance is not significantly different from that of the y-polarized wave, and it can be considered that this device is polarization-independent.

[0052] Example 2

[0053] In this embodiment, the specific structure of the polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance is as follows: Figure 1 and Figure 2 As shown, no further details will be given. The following only describes its specific dimensions and processing technology. Figure 3 As shown, the processing of the device is as follows:

[0054] The high-resistance silicon substrate is n-type, and its resistivity is greater than 10 kΩ·cm. First, an n-type doping layer 2 is formed on the high-resistance silicon substrate by ion implantation, and the doping element is phosphorus, and the doping concentration is 5×10 15 cm -3 . Then, a metal pattern structure is formed on the doped layer 2 through the steps of photolithography development-magnetron sputtering-stripping, including a first metal electrode 3, a metal super surface 4, a metal connecting line 5, and a second metal electrode 6. Among them, the magnetron sputtering step first deposits 20nm thick titanium, and then deposits 150nm thick gold. Finally, the back of the high-resistance silicon substrate 1 is ground and polished by chemical mechanical polishing to be thinned to 112.5um.

[0055] In this embodiment, the lattice constant of the supersurface, that is, the outer contour side length of the supersurface unit, is 50um. Among them, the width of all metal lines in the spliced ​​metal supersurface 4 is 4um (for the 4 boundary metal lines at the boundary of each unit, the width is 2um, and the metal line with a width of 4um is obtained after splicing with the adjacent units. The two internal metal lines that cross inside the unit have a width of 4um). At the same time, in the complete capacitor gap formed by splicing two half-capacitor gaps, the long sides of the first complete pole plate metal sheet 11 and the second complete pole plate metal sheet 12 are both 8um, and the short sides are both 2um. The complete capacitor gap 13 formed in this way is 8um long and 1um wide. In the entire metal supersurface 4, the supersurface array size is 30×30, containing 900 supersurface units.

[0056] In addition, the first metal electrode 1 has a width of 250um, a distance of 250um from the metal super surface 4, and surrounds the metal super surface 4 structure on three sides. The second metal electrode 2 has a width of 250um, a distance of 250um from the metal super surface 4, and a length of 1450um. It is connected to the metal super surface 4 through 29 4um wide metal connecting wires 5, and the 29 metal connecting wires are arranged at equal intervals.

[0057] Based on the polarization-independent silicon-based electrically controlled terahertz metasurface modulator designed in this embodiment, when the modulation voltage is -8V, for the y-polarized normal incident wave with a frequency of 0.8THz, the simulation results show that its transmittance is as high as 70%. When the modulation voltage is +8V, for the y-polarized normal incident wave with a frequency of 0.8THz, the simulation results show that its transmittance is 40%. Its modulation dynamic range is 30%, and the insertion loss is as low as 30%. At the same time, under other polarized wave incident conditions, the simulation results show that the frequency domain characteristic curve of its transmittance is not significantly different from that of the y-polarized wave, and it can be considered that this device is polarization-independent.

[0058] Example 3

[0059] In this embodiment, the specific structure of the polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance is as follows: Figure 1 and Figure 2 As shown, no further details will be given. The following only describes its specific dimensions and processing technology. Figure 3 As shown, the processing of the device is as follows:

[0060] The high-resistance silicon substrate is n-type, and its resistivity is greater than 10 kΩ·cm. First, an n-type doping layer 2 is formed on the high-resistance silicon substrate by ion implantation, and the doping element is phosphorus, and the doping concentration is 5×10 15 cm -3 . Then, a metal pattern structure is formed on the doped layer 2 through the steps of photolithography development-magnetron sputtering-stripping, including a first metal electrode 3, a metal super surface 4, a metal connecting line 5, and a second metal electrode 6. Among them, the magnetron sputtering step first deposits 20nm thick titanium, and then deposits 150nm thick gold. Finally, the back of the high-resistance silicon substrate 1 is ground and polished by chemical mechanical polishing to be thinned to 27.5um.

[0061] In this embodiment, the lattice constant of the supersurface, that is, the outer contour side length of the supersurface unit, is 10um. Among them, the width of all metal lines in the spliced ​​metal supersurface 4 is 1um (for the 4 boundary metal lines at the boundary of each unit, the width is 0.5um, and the metal line with a width of 1um is obtained after splicing with the adjacent units. The two internal metal lines that cross inside the unit have a width of 1um). At the same time, in the complete capacitor gap formed by splicing two half-capacitor gaps, the long sides of the first complete pole plate metal sheet 11 and the second complete pole plate metal sheet 12 are both 2um, and the short sides are both 0.5um. The complete capacitor gap 13 formed in this way is 2um long and 0.5um wide. In the entire metal supersurface 4, the supersurface array size is 30×30, containing 900 supersurface units.

[0062] In addition, the first metal electrode 1 has a width of 250um, a distance of 250um from the metal super surface 4, and surrounds the metal super surface 4 structure on three sides. The second metal electrode 2 has a width of 250um, a distance of 250um from the metal super surface 4, and a length of 290um. It is connected to the metal super surface 4 through 29 4um wide metal connecting wires 5, and the 29 metal connecting wires are arranged at equal intervals.

[0063] Based on the simulation of the polarization-independent silicon-based electrically controlled terahertz metasurface modulator designed in this embodiment, when the modulation voltage is -8V, for the y-polarized normal incident wave with a frequency of 4.54THz, the simulation results show that its transmittance is as high as 95%. When the modulation voltage is +8V, for the y-polarized normal incident wave with a frequency of 4.54THz, the simulation results show that its transmittance is 65%. Its modulation dynamic range is 30%, and the insertion loss is as low as 5%. At the same time, under other polarized wave incident conditions, the simulation results show that the frequency domain characteristic curve of its transmittance is not significantly different from that of the y-polarized wave, and it can be considered that this device is polarization-independent.

[0064] The above-described embodiments are only some preferred implementations of the present invention, but are not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance, characterized in that: It comprises a high-resistance silicon substrate (1), and a doping layer (2) is formed on the front side of the high-resistance silicon substrate (1) by ion implantation; The surface of the doped layer (2) is processed with a metal pattern structure consisting of a first metal electrode (3), a metal supersurface (4), a metal connecting wire (5) and a second metal electrode (6), and Schottky contact is formed between the metal pattern structure and the doped layer (2); the first metal electrode (3) is a square ring with a single-side opening, and is arranged on the periphery of the square outline of the metal supersurface (4) in a manner of surrounding on three sides, and the second metal electrode (6) is located on the side of the periphery of the metal supersurface (4) that is not surrounded by the first metal electrode (3); the first metal electrode (3) and the metal supersurface (4) are kept at a distance and are not in contact, and the second metal electrode (6) and the metal supersurface (4) are connected via a series of metal connecting wires (5); The metal metasurface (4) is formed by supersurface units densely arranged in a square lattice on a plane, the square lattice outer contour of each supersurface unit is surrounded by four boundary metal wires, and two internal metal wires connecting the diagonal vertices of the square are arranged along two diagonal lines of the outer contour; each boundary metal wire is disconnected at the midpoint to form a semi-capacitive gap, and the semi-capacitive gap is composed of two plate metal sheets that are arranged at the midpoint disconnection and maintain a gap with each other; two adjacent supersurface units are joined and spliced ​​by their respective boundary metal wires to form a complete metal wire, and the semi-capacitive gaps on the two joined and spliced ​​boundary metal wires are also spliced ​​to form a complete capacitive gap, so that two adjacent supersurface units in the metal metasurface (4) are electrically connected and have the same electric potential.

2. The polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance according to claim 1, characterized in that: The high-resistance silicon substrate (1) is an n-type silicon substrate.

3. The polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance according to claim 1, characterized in that: The front surface of the high-resistance silicon substrate (1) is n-type doped by injecting phosphorus elements to form a doping layer (2).

4. The polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance according to claim 1, characterized in that: The metal pattern structure is a composite metal layer, wherein the lower layer is titanium and the upper layer is gold.

5. The polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance according to claim 4, characterized in that: The metal pattern structure on the doping layer (2) is formed through the steps of photolithography development-magnetron sputtering-stripping.

6. The polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance according to claim 5, characterized in that: After the metal pattern structure is processed, the high-resistance silicon substrate (1) needs to be adjusted to a target design value by chemical mechanical polishing so that the Anapole resonance frequency coincides with the substrate FP transmission peak frequency.

7. The polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance according to claim 1, characterized in that: The second metal electrode (6) is arranged parallel to one side of the metal super surface (4), and the metal connecting wires (5) connecting the two are arranged at equal intervals.

8. The polarization-independent silicon-based electrically controlled terahertz metasurface modulator based on Anapole resonance according to claim 1, characterized in that: The operating frequency range of the modulator is 0.1THz-5THz.

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