Silicon-based terahertz switch

Abstract

The application discloses a silicon-based terahertz switch, which comprises a silicon structure, a first electrode, a metamaterial structure, an insulating layer, a substrate and a second electrode; the silicon structure comprises a clamped structure, a supporting beam and a silicon plate which are sequentially connected from outside to inside; the first electrode is arranged on the upper surface of the clamped structure; the metamaterial structure is arranged on the lower surface of the silicon plate; the insulating layer covers the metamaterial structure; the upper surface of the substrate is provided with a groove, the clamped structure is arranged on the upper surface of the substrate, and the supporting beam, the silicon plate, the metamaterial structure and the insulating layer are suspended at the recess of the groove; the second electrode is arranged on the recess bottom surface of the groove, and the second electrode has an air gap with the insulating layer. The device absorption rate and the modulation contrast of the silicon-based terahertz switch are high, the full width at half maximum value is small, the driving power consumption is low, the switching speed is fast, and the control is simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of terahertz, in particular to a silicon-based terahertz switch. BACKGROUND

[0002] With the development of terahertz technology, it has great application potential to realize high-performance terahertz switch devices in signal filtering, modulation and imaging technologies. As a typical terahertz switch device, the reflective terahertz switch, also known as the adjustable terahertz absorber, is crucial for promoting terahertz communication, single-pixel imaging and spectrum applications. The traditional terahertz switch has problems such as low device absorption rate, low modulation contrast, and large full width at half maximum, and therefore is not suitable for use in high-performance terahertz systems, thereby affecting the practicability of the switch. SUMMARY

[0003] The present application aims to at least solve one of the problems in the prior art. To this end, one object of the present application is to provide a silicon-based terahertz switch, which has high device absorption rate and modulation contrast, small full width at half maximum, low driving power consumption, fast switching speed and simple control.

[0004] The silicon-based terahertz switch according to the embodiment of the present application comprises:

[0005] a silicon structure comprising a clamped structure, a support beam and a silicon plate connected in sequence from outside to inside;

[0006] a first electrode disposed on the upper surface of the clamped structure;

[0007] a metamaterial structure disposed on the lower surface of the silicon plate;

[0008] an insulating layer covering the metamaterial structure;

[0009] a substrate having a recess on the upper surface thereof, the clamped structure being disposed on the upper surface of the substrate, the support beam, the silicon plate, the metamaterial structure and the insulating layer being suspended at the recess of the recess;

[0010] a second electrode disposed on the recess bottom surface of the recess, the second electrode having an air gap with the insulating layer;

[0011] In operation, the terahertz beam is incident on the silicon-based terahertz switch perpendicularly to the silicon plate, under the condition that no driving voltage is applied between the first electrode and the second electrode, i.e. no power is supplied, the metamaterial structure and the insulating layer are suspended above the second electrode, and there is an air gap between the insulating layer and the second electrode, thereby realizing the signal "off" effect, and the silicon-based terahertz switch completely absorbs the terahertz beam at the working frequency; when a driving voltage is applied between the first electrode and the second electrode, the silicon plate is pulled down under the action of electrostatic force, so that the insulating layer is in contact with the second electrode, and there is no air gap between the insulating layer and the second electrode, and the silicon-based terahertz switch is in the signal "on" state, and completely reflects the terahertz beam at all frequencies. That is, the terahertz beam absorption and reflection are realized by the interaction between the metamaterial structure and the second electrode under different air gap conditions.

[0012] Compared with the prior art, the silicon-based terahertz switch of the embodiment of the present application can directly adjust the terahertz spectral characteristics of the switch by applying a driving voltage between the first electrode and the second electrode and changing the air gap between the insulating material and the second electrode. By using the optimized metamaterial structure, the device absorption, modulation contrast and full width at half maximum value are effectively improved under the condition that the displacement stroke is extremely small compared with the working wavelength; in addition, the electrostatic driving is adopted, which not only has a simple structure and is easy to implement, but also greatly reduces the driving voltage and operating power consumption, and has a fast switching speed and simple control, thereby realizing voltage-adjustable device performance.

[0013] In some embodiments, the metamaterial structure comprises a plurality of metamaterial units, and the metamaterial units are dielectric structures or metal structures.

[0014] In some embodiments, the metamaterial unit comprises two I-shaped structures, the abdomens of the two I-shaped structures are vertically intersected with each other in the center, and the size parameters of the metamaterial unit structure are selected by intelligent algorithm optimization according to the requirements of the terahertz spectral characteristics.

[0015] In some embodiments, the period size of the metamaterial unit ranges from 20 μm to 500 μm.

[0016] In some embodiments, the air gap is 1 μm to 20 μm.

[0017] In some embodiments, the support beams are a plurality of, and the plurality of support beams are all folded and curved structures and are spaced around the silicon plate.

[0018] In some embodiments, the connection points of the plurality of support beams and the silicon plate are distributed at equal intervals around the silicon plate.

[0019] In some embodiments, the characteristic size of the silicon plate is 2 mm to 20 mm.

[0020] In some embodiments, the lower surface of the clamped structure and the upper surface of the substrate are tightly fitted and fixed using a wafer bonding process.

[0021] In some embodiments, the first electrode is obtained by first installing a mask to cover the silicon plate and the support beam and then using a metal sputtering process on the fixture structure.

[0022] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0024] Figure 1 This is a schematic structural diagram of a silicon-based terahertz switch in one embodiment of the present invention;

[0025] Figure 2 This is a schematic structural diagram of a support beam and a silicon plate according to an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of a metamaterial structure according to an embodiment of the present invention;

[0027] Figure 4 These are the simulation results of the terahertz spectrum characteristics of a silicon-based terahertz switch in the “on” and “off” states according to an embodiment of the present invention.

[0028] Reference numerals

[0029] First electrode 101 ; support beam 102 ; silicon plate 103 ; metamaterial structure 104 ; insulating layer 105 ; clamped structure 106 ; second electrode 201 ; substrate 202 ; groove 203 . DETAILED DESCRIPTION

[0030] The following describes embodiments of the present invention in detail. Examples of the embodiments 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 only to explain the present invention and are not to be construed as limiting the present invention.

[0031] The following combination Figures 1 to 4 The silicon-based terahertz switch according to an embodiment of the present invention is described below.

[0032] like Figures 1 to 3As shown, the silicon-based terahertz switch according to the embodiment of the present application comprises a silicon structure, a first electrode 101, a metamaterial structure 104, an insulating layer 105, a substrate 202 and a second electrode 201. The silicon structure comprises a clamped structure 106, a support beam 102 and a silicon plate 103 connected in sequence from outside to inside; the first electrode 101 is arranged on the upper surface of the clamped structure 106; the metamaterial structure 104 is arranged on the lower surface of the silicon plate 103; the insulating layer 105 covers the metamaterial structure 104; the upper surface of the substrate 202 is provided with a groove 203, the substrate 202 can be a glass substrate, the clamped structure 106 is arranged on the upper surface of the substrate 202, and the support beam 102, the silicon plate 103, the metamaterial structure 104 and the insulating layer 105 are suspended in the recess of the groove 203; the second electrode 201 is arranged on the bottom surface of the groove 203, and there is an air gap between the second electrode 201 and the insulating layer 105.

[0033] Specifically, the silicon structure comprises a clamped structure 106, a support beam 102 and a silicon plate 103 connected in sequence from outside to inside, that is, the clamped structure 106 is a ring structure, the silicon plate 103 is located in the center of the inner side of the clamped structure 106, and the silicon plate 103 can be square, circular or the like. The support beam 102 is located between the clamped structure 106 and the silicon plate 103, and mainly functions to support the silicon plate 103 in a suspended state and can drive the silicon plate 103 to move, so that the silicon plate 103 can be pulled down under the action of electrostatic force when the silicon-based terahertz switch works, and the silicon structure can be an integrally formed structure. The resistivity of the silicon structure can be greater than 10000 Ω·cm, that is, the resistivity of the silicon structure is large, which can be used to reduce the energy loss of the terahertz beam in the material, and reduce the full width at half maximum value of the silicon-based terahertz switch; and the thickness of the clamped structure 106, the support beam 102 and the silicon plate 103 of the silicon structure can be the same, and the thickness value of the clamped structure 106, the support beam 102 and the silicon plate 103 can be selected to be 30 μm-300 μm according to actual needs, which can suppress the Etalon effect of multiple reflections and gradual transmission of incident terahertz waves in the thicker silicon plate 103, and is beneficial to the design of a narrow-band terahertz switch. The area size of the silicon plate 103 can be selected to be large enough, which is beneficial to reducing the driving voltage of the electrostatic driving mechanism.

[0034] The first electrode 101 is arranged on the upper surface of the clamped structure 106, that is, the first electrode 101 is fixed with the upper surface of the clamped structure 106, and is used to apply a driving voltage signal.

[0035] The metamaterial structure 104 is arranged on the lower surface of the silicon plate 103; it can be understood that the metamaterial structure 104 is an array structure formed by periodically arranging metamaterial units of sub-wavelength size, which opens up unprecedented possibilities for manipulating electromagnetic waves in the sub-wavelength scale and realizes electromagnetic properties that natural materials cannot realize. By changing the structural size of the metamaterial unit, the near-field coupling response of the unit can be adjusted, thereby substantially affecting the amplitude response, resonance frequency and other characteristics. Therefore, the introduction of the metamaterial structure 104 provides a new and efficient way for designing a high-performance terahertz switch. The metamaterial structure 104 is fixed on the lower surface of the silicon plate 103 and interacts with the second electrode 201 to produce a strong resonance response, which is conducive to improving the absorption rate of the device (i.e., the absorption rate of the terahertz switch).

[0036] The insulating layer 105 is covered on the metamaterial structure 104, so that when the silicon-based terahertz switch is working, the driving voltage is applied to the first electrode 101 and the second electrode 201, and the silicon plate 103 is pulled down under the action of electrostatic force, which can effectively avoid the short circuit caused by the contact between the metamaterial structure 104 and the second electrode 201, thereby avoiding the burning of the silicon-based terahertz switch.

[0037] The upper surface of the substrate 202 is provided with a groove 203 in the central position, and the size of the air gap between the insulating layer 105 and the second electrode 201 is determined by the depth of the groove 203, and the thickness of the substrate 202 can be 300 μm-1000 μm; the fixed support structure 106 is arranged on the upper surface of the substrate 202, and the support beam 102, the silicon plate 103, the metamaterial structure 104 and the insulating layer 105 are suspended in the recess of the groove 203.

[0038] The second electrode 201 is arranged on the concave bottom surface of the groove 203 and is used for applying a ground signal; the second electrode 201 and the insulating layer 105 have an air gap, which can be close enough, so that on the one hand, the distance between the metamaterial structure 104 and the second electrode 201 is close enough, and the resonance response generated by the interaction between the two is strong, which is conducive to improving the absorption rate of the terahertz switch; on the other hand, the small air gap size is also conducive to reducing the driving voltage of the silicon-based terahertz switch.

[0039] According to the silicon-based terahertz switch of the embodiment of the present application, when working, the terahertz beam is incident to the silicon-based terahertz switch vertically to the silicon plate 103, under the condition that no driving voltage is applied between the first electrode 101 and the second electrode 201, the metamaterial structure 104 and the insulating layer 105 are suspended above the second electrode 201, as shown in FIG. 1, and the silicon plate 103 is pulled down under the action of electrostatic force, as shown in FIG. 2. Figure 1As shown in the middle, the surfaces of the support beam 102, the silicon plate 103 and the fixed support structure 106 are all high, and there is an air gap between them, thereby realizing the effect of signal "off", and the silicon-based terahertz switch completely absorbs the terahertz beam at the working frequency; the driving voltage is applied between the first electrode 101 and the second electrode 201, under the action of electrostatic force, the silicon plate 103 is pulled down, so that the insulating layer 105 is in contact with the second electrode 201, and there is no air gap between the insulating layer 105 and the second electrode 201, and the silicon-based terahertz switch is in the signal "on" state, and completely reflects the terahertz wave at all frequencies. That is, the silicon-based terahertz beam absorption and reflection are realized by the interaction of the metamaterial structure 104 and the second electrode 201 under different air gap conditions.

[0040] Figure 4 The simulation results of the terahertz spectrum characteristics of the silicon-based terahertz switch in the "on" and "off" states according to the embodiment of the application are as shown in the following figure. Figure 4 As shown in the figure, when not powered, the metamaterial structure 104 is suspended above the second electrode 201, and there is an air gap between them, the terahertz switch is in the "off state, the resonant frequency is 0.7THz, the absorption rate is close to 100%, and the full width at half maximum value is about 12GHz; when the driving voltage is applied, the metamaterial structure 104 is in contact with the second electrode 201, and there is no air gap between them, the terahertz switch is in the "on" state, the absorption rate is 0 in the full frequency range, and the modulation contrast is about 100%.

[0041] Compared with the prior art, the silicon-based terahertz switch according to the embodiment of the application can directly adjust the terahertz spectrum characteristics of the switch by applying a driving voltage between the first electrode 101 and the second electrode 201 and changing the air gap between the insulating material and the second electrode 201. By using the optimized metamaterial structure 104, the absorption rate, the modulation contrast and the full width at half maximum value are effectively improved under the condition that the displacement stroke is much smaller than the working wavelength; in addition, the electrostatic driving is adopted in the embodiment of the application, which not only has a simple structure and is easy to realize, but also greatly reduces the driving voltage and working power consumption, has a fast switching speed and simple control, and realizes the voltage-adjustable performance of the device.

[0042] In some embodiments, the metamaterial structure 104 includes a plurality of metamaterial units, and the metamaterial units are dielectric structures or metal structures. The dielectric structure can be prepared by a PECVD process, and the metal structure can be processed by metal evaporation and stripping process. The dielectric structure and the metal structure can ensure the resonant response under a specific terahertz frequency condition.

[0043] In some embodiments, the metamaterial unit comprises two I-shaped structures, the web portions of the two I-shaped structures are vertically intersected with each other in the middle, and the size parameters of the metamaterial unit structure are selected by intelligent algorithm according to the requirements of terahertz spectrum characteristics. The number of the metamaterial units is not limited to Figure 3 5x5 shown in the figure, and should be more than this number. By using the optimized metamaterial structure 104, the device absorption, modulation contrast and full width at half maximum value are effectively improved under the condition that the displacement stroke is extremely small compared with the working wavelength.

[0044] In some embodiments, the period size of the metamaterial unit ranges from 20 μm to 500 μm. Here, the period size can be understood as Figure 3 the distance between the centers of two metamaterial units, and the period size is related to the working frequency / wavelength of the terahertz switch. By selecting the period size of the metamaterial unit to range from 20 μm to 500 μm, a resonant response at a specific terahertz frequency can be achieved.

[0045] In some embodiments, the air gap is 1 μm to 20 μm. Thus, the air gap is small enough, on the one hand, to make the distance between the metamaterial structure 104 and the second electrode 201 close enough, and the resonant response generated by the interaction between the two is strong, which is conducive to improving the absorption of the terahertz switch; on the other hand, the small air gap size is also conducive to reducing the driving voltage of the silicon-based terahertz switch.

[0046] In some embodiments, the support beam 102 has a plurality of support beams 102, and the plurality of support beams 102 are all folded and curved structures and are spaced apart around the silicon plate 103. It can be understood that the support beam 102 adopts a folded and curved structure, which can reduce its elastic coefficient, thereby reducing the driving voltage of the silicon-based terahertz switch. By connecting the plurality of support beams 102 between the fixed support structure 106 and the silicon plate 103 at intervals, the silicon plate 103 can be supported in a suspended state and can be driven to move. Optionally, the support beam 102 can be an even number.

[0047] In some embodiments, the connection points of the plurality of support beams 102 and the silicon plate 103 are distributed at equal intervals around the silicon plate 103; in this way, the stress conditions of each connection point on the silicon plate 103 are the same, and the displacements of each position on the silicon plate 103 are basically equal when the silicon plate 103 is pulled by electrostatic attraction. For example, in Figure 2 the figure, the four corner points of the square silicon plate 103 are respectively connected to one support beam 102.

[0048] In some embodiments, the characteristic size of the silicon plate 103 is 2 mm to 20 mm. Thus, the receiving area of the terahertz switch for the incident terahertz wave is increased, fully reacts with the incident terahertz wave, and the driving voltage of the switch can be reduced.

[0049] In some embodiments, the lower surface of the fixed structure 106 and the upper surface of the substrate 202 are fixedly attached by a wafer bonding process, so that the lower surface of the fixed structure 106 and the upper surface of the substrate 202 are fixedly attached, which is conducive to controlling the initial value of the air gap between the insulating layer 105 and the second electrode 201. Optionally, the wafer bonding process can use an anodic bonding process, a low-temperature bonding process, or the like.

[0050] In some embodiments, the first electrode 101 is a metal electrode, which is obtained by first installing a mask to shield the silicon plate 103 and the support beam 102, and then using a metal sputtering process on the fixed structure 106, so that the first electrode is fixed on the upper surface of the fixed structure 106.

[0051] In some embodiments, the second electrode 201 is a metal electrode, which is obtained by using a metal evaporation and stripping process on the concave bottom surface of the groove 203.

[0052] In some embodiments, the groove 203 on the substrate 202 can be formed by using a buffered oxide etching solution to etch the original substrate 202. During the process of etching the original substrate 202 using the buffered oxide etching solution, a chromium-gold thin film is used as a glass etching mask, and the thickness needs to be greater than 100 nm to ensure that the mask film has high film quality and sufficient density, so as to avoid small holes in the mask film and prevent the buffered oxide etching solution from etching the glass structure below the mask film through these small holes, thereby affecting the quality of the subsequent wafer bonding. After the etching of the original substrate 202 is completed, the mask layer can be removed by using a chromium-gold etching solution to obtain the substrate 202 with the groove 203 according to the embodiments of the present application.

[0053] In some embodiments, the silicon structure can be obtained by the following method: a potassium hydroxide wet etching process or a chemical-mechanical polishing (CMP) process is used to thin the silicon wafer to form a silicon thin film, and the thickness of the silicon thin film ranges from 30 μm to 300 μm; then, a deep reactive ion etching (DRIE) process or a laser cutting process is used to form the support beam 102, the silicon plate 103, and the fixed structure 106, so as to obtain the silicon structure according to the embodiments of the present application.

[0054] In some embodiments, the insulating layer 105 can be a dielectric material such as silicon oxide, silicon nitride, etc., which can be formed by a plasma enhanced chemical vapor deposition (PECVD) process. The insulating layer 105 covers the metamaterial structure 104, and the thickness of the insulating layer 105 is greater than that of the metamaterial structure 104, so as to prevent the metamaterial structure 104 from being short-circuited by being attracted to the second electrode 201.

[0055] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" etc. means that the specific features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, or characteristics described can be combined in any appropriate manner in one or more embodiments or examples.

[0056] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and alterations can be made hereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A silicon-based terahertz switch, characterized by, The application relates to a silicon-based terahertz switch. The silicon structure comprises a fixed support structure, a support beam and a silicon plate which are sequentially connected from outside to inside; A first electrode is arranged on the upper surface of the fixed support structure; A metamaterial structure is arranged on the lower surface of the silicon plate; An insulating layer is arranged on the metamaterial structure; A substrate has a recess on the upper surface, the fixed support structure is arranged on the upper surface of the substrate, and the support beam, the silicon plate, the metamaterial structure and the insulating layer are suspended at the recess of the recess; A second electrode is arranged on the recess bottom surface of the recess, and an air gap exists between the second electrode and the insulating layer; During operation, a terahertz beam is vertically incident on the silicon-based terahertz switch, the metamaterial structure and the insulating layer are suspended above the second electrode under the condition of no power supply, the air gap exists between the insulating layer and the second electrode, thereby realizing the effect of signal "off", and the silicon-based terahertz switch completely absorbs the terahertz beam at the working frequency; a driving voltage is applied between the first electrode and the second electrode, the silicon plate is pulled down under the action of electrostatic force, the insulating layer is in contact with the second electrode, and the silicon-based terahertz switch is in the signal "on" state and completely reflects the terahertz wave at all frequencies.

2. The silicon-based terahertz switch of claim 1, wherein, The metamaterial structure comprises a plurality of metamaterial units, and the metamaterial units are dielectric structures or metal structures.

3. The silicon-based terahertz switch of claim 2, wherein, The metamaterial unit comprises two I-shaped structures, the abdomens of the two I-shaped structures are vertically crossed in the middle of each other, and the size parameters of the metamaterial unit structure are selected by intelligent algorithm optimization according to the requirements of terahertz spectrum characteristics.

4. The silicon-based terahertz switch of claim 2, wherein, The period size of the metamaterial unit ranges from 20 mu m to 500 mu m.

5. The silicon-based terahertz switch of claim 1, wherein, The air gap is 1 mu m to 20 mu m.

6. The silicon-based terahertz switch according to any one of claims 1-5, wherein, The support beam has a plurality of folding and bending structures and is spaced around the silicon plate.

7. The silicon-based terahertz switch of claim 6, wherein, The connecting points of the plurality of support beams and the silicon plate are equally spaced around the silicon plate.

8. The silicon-based terahertz switch according to any one of claims 1-5, wherein, The characteristic size of the silicon plate is 2 mm to 20 mm.

9. The silicon-based terahertz switch according to any one of claims 1-5, wherein, The lower surface of the fixed support structure and the upper surface of the substrate are tightly fixed by wafer bonding process.

10. The silicon-based terahertz switch according to any one of claims 1-5, wherein, The first electrode is obtained on the fixed support structure by first installing a mask to shield the silicon plate and the support beam and then using a metal sputtering process.

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