An all-silicon terahertz power divider with arbitrary ratio tunable based on a subwavelength Bragg grating and its control method.

Abstract

This invention discloses an all-silicon terahertz power divider with arbitrary ratio adjustable based on a subwavelength Bragg grating and its control method, belonging to the field of terahertz on-chip circuit control technology. The power divider consists of three coplanar silicon waveguides placed side by side, which are arranged from top to bottom as an upper waveguide, a middle waveguide, and a lower waveguide. The upper part of the upper waveguide and the lower part of the lower waveguide are respectively connected to a mechanical control device or actuator. By adjusting the coupling spacing between the waveguides through the mechanical control device or actuator, a power divider with arbitrary ratio and continuous adjustability is realized. This invention causes a nonlinear change in the coupling strength between different waveguides by changing the coupling spacing between the subwavelength adiabatic grating waveguides, thereby changing the output power ratio of different waveguides. It has good performance in the terahertz band. By introducing a subwavelength grating structure and a three-waveguide coupling structure, and by adjusting the coupling spacing between the waveguides, a power divider with arbitrary ratio and continuous adjustability is realized.

Description

Technical Field

[0001] This invention belongs to the field of terahertz on-chip circuit control technology, specifically relating to an all-silicon terahertz arbitrary ratio adjustable power divider based on a subwavelength Bragg grating and its control method. Background Technology

[0002] With the development of terahertz on-chip integrated circuits (ICBs), these ICs have demonstrated excellent performance in areas such as 6G wireless communication, high-speed on-chip interconnection, low-loss transmission, and highly compact devices. On-chip power dividers (or simply power dividers) are key components in large-scale photonic integrated circuits and are indispensable in many scenarios, including optical switches, modulators, wavelength division multiplexers, optical phase arrays, and optical neural networks. Continuously adjustable arbitrary-ratio power dividers can freely adjust the power distribution ratio of different channels in a certain way, providing multiple power distribution schemes to meet different application needs and thus having a wider range of applications.

[0003] Currently, various structures have been proven capable of power division, including directional couplers, multimode interference couplers, pseudosurface plasmon subwavelength waveguides, Y-junctions, and photonic crystal waveguides. For existing tunable power dividers, there are two main approaches: electrical control and optical control. Electrical control involves adding electronic components (varactor diodes, PIN diodes, etc.) to integrated circuits in the low-frequency range, such as microwaves, and adjusting the power division ratio within a small range by changing the on / off state of these components. Optical control involves applying optical pumping to on-chip silicon waveguide devices, thereby controlling the power division ratio by altering the properties of the photoresponse material. In addition, adjusting the device structure design can also achieve power division ratio adjustment. These methods can only achieve power division ratio control to a certain extent; however, achieving continuously tunable arbitrary power division ratios within the terahertz frequency range (or even higher frequencies) still presents some unavoidable limitations. These drawbacks include: 1. In the terahertz band, the presence of intrinsic cutoff frequencies of semiconductor materials causes semiconductor devices to fail, making it impossible to reproduce the control of electronic devices by microwave frequencies; 2. Applying optical pumping to silicon waveguide systems introduces additional energy loss, and optical pumping systems are difficult to integrate; 3. Changing the structure of the device itself in the design cannot achieve continuous tunability in actual use.

[0004] While existing work has made some progress in this field, power dividers with arbitrary ratios, continuous adjustability, and low loss remain key components for further development. Therefore, a simple yet ingenious design approach is needed to integrate these three advantages. Based on the above analysis, researching and designing novel adjustable power dividers with arbitrary ratios that meet these requirements is crucial to the development and potential applications of terahertz integrated circuits. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, this invention provides an all-silicon terahertz power divider with arbitrary ratio tunable based on a subwavelength Bragg grating and its control method. This invention utilizes the variation in the coupling spacing between subwavelength adiabatic grating waveguides to induce a nonlinear change in the coupling strength between different waveguides, thereby altering the output power ratio of different waveguides and exhibiting excellent performance within the terahertz band. This invention introduces a subwavelength grating structure and a three-waveguide coupling structure, and by adjusting the coupling spacing between the waveguides, achieves a power divider with arbitrary ratio and continuous tunability.

[0006] This invention is achieved through the following technical solution:

[0007] A power divider with arbitrary ratio adjustable in all-silicon terahertz circuit based on a subwavelength Bragg grating is described. The power divider consists of three coplanar silicon waveguides placed side by side. The three coplanar silicon waveguides are arranged from top to bottom as upper waveguide 1, middle waveguide 2, and lower waveguide 3. The upper part of the upper waveguide 1 and the lower part of the lower waveguide 3 are respectively connected to a control device or actuator 17. The coupling spacing between the waveguides is adjusted by the control device or actuator, thereby realizing a power divider with arbitrary ratio and continuous adjustability.

[0008] The power divider is divided into an input signal unit 4, a coupling unit 5, and an output signal unit 6 from left to right. The input signal unit 4 is composed of a signal feed pin 7, a tapered waveguide 8, and a subwavelength grating 9 connected in sequence. The coupling unit 5 is composed of three strip waveguides 10 and three adiabatic subwavelength gratings with gradually varying sawtooth heights. The output signal unit 6 is composed of a subwavelength grating waveguide 14, a curved waveguide 15, and a signal output pin 16 connected in sequence. The curved waveguide 15 has a shape that follows a cosine curve.

[0009] Furthermore, the upper waveguide 1, the middle waveguide 2, and the lower waveguide 3 are all located within the encapsulation structure, wherein the encapsulation structure includes a base 18 and a top cover 19. The middle waveguide 2 is fixed to the base 18 through an equivalent dielectric structure. The coupling portion between the middle waveguide 2 and the upper waveguide 1 and the lower waveguide 3 is air, and the spacing between the middle waveguide 2 and the upper waveguide 1 and the lower waveguide 3 can be continuously adjusted.

[0010] Furthermore, both the base 18 and the top cover 19 are made of brass. The horizontal and vertical spacing between the base 18 and the top cover 19 and the waveguide should be appropriate, and the electromagnetic interference to the waveguide transmission performance can be ignored. The base 18 has two small holes on its side, which are used to control the distance between the upper waveguide 1 and the middle waveguide 2, and between the lower waveguide 3 and the middle waveguide 2, respectively. The top cover 19 has a small square hole 22 in the center to facilitate observation of the spacing between the waveguides inside the package. The base 18 and the middle waveguide 2 are fixed together using screw holes 23.

[0011] Furthermore, the intermediate waveguide 2 adopts an equivalent dielectric structure to achieve self-support; the upper side of the upper waveguide 1 and the lower side of the lower waveguide 3 adopt an equivalent dielectric structure to achieve self-support; the upper waveguide 1, the intermediate waveguide 2, the lower waveguide 3, and the equivalent dielectric structure are all manufactured on a high-resistivity silicon wafer using a deep silicon etching process.

[0012] Furthermore, the period of the equivalent dielectric air hole in the equivalent dielectric structure is 1 / 24-1 / 23 of the wavelength of the power divider's operating center frequency, and the diameter of the air hole is 1 / 26-1 / 25 of the wavelength of the power divider's operating center frequency. This can provide a self-supporting structure for the chip and effectively suppress the diffusion of energy flow within the waveguide.

[0013] The waveguide structure has strong robustness and can achieve the same function when the shape of the equivalent dielectric air hole is elliptical or circular with a radius length deviation of less than 5%, which can reduce the requirements of the device for processing technology.

[0014] Furthermore, the three adiabatic subwavelength gratings with gradually varying sawtooth heights include a first adiabatic subwavelength grating 11, a second adiabatic subwavelength grating 12, and a third adiabatic subwavelength grating 13; wherein the sawtooth heights of the first adiabatic subwavelength grating 11 and the third adiabatic subwavelength grating 13 increase linearly with increasing horizontal distance, and the sawtooth heights of the second adiabatic subwavelength grating 12 decrease linearly with increasing horizontal distance.

[0015] Furthermore, the subwavelength grating 9, the first adiabatic subwavelength grating 11, the second adiabatic subwavelength grating 12, the third adiabatic subwavelength grating 13, and the subwavelength grating waveguide 14 are all composed of periodic cuboid structures. The periodic length of the periodic cuboid structure of the above gratings is 1 / 7 to 1 / 6 of the wavelength of the working center frequency of the power divider, and the duty cycle is 1 / 2.

[0016] The lengths of the signal feed pin 7 and the signal output pin 16 are both 3-4 times the wavelength of the power divider's operating center frequency.

[0017] Furthermore, the sawtooth height in the subwavelength grating 9 is 1 / 3 to 1 / 2 of the wavelength of the power divider's operating center frequency;

[0018] The length of the strip waveguide 10 is 4-6 times the wavelength of the power divider's operating center frequency, and the width of the strip waveguide 10 is 1 / 13-1 / 11 of the wavelength of the power divider's operating center frequency.

[0019] The sawtooth height in the subwavelength grating waveguide 14 is 1 / 4 to 1 / 3 of the wavelength of the power divider's operating center frequency.

[0020] The length of the actuator 17 is 11-14 times the wavelength of the power divider's operating center frequency.

[0021] Secondly, the present invention also provides a method for mechanically controlling the coupling spacing of an all-silicon terahertz power divider with arbitrarily adjustable ratio based on a subwavelength Bragg grating, specifically including the following steps:

[0022] Step 1: Construct a mechanical control device, which includes a fixed device, a precision electrically controlled horizontal displacement stage, and a mechanical control module; the precision electrically controlled horizontal displacement stage is located on one side of the fixed device, and the mechanical control module is connected to the precision electrically controlled horizontal displacement stage;

[0023] Step 2: Fix the middle waveguide 2 on the base 18; connect the outer sides of the upper waveguide 1 and the lower waveguide 3 to the precision electronically controlled horizontal displacement stage, which are used to adjust the distance between the upper waveguide 1 and the middle waveguide 2 and the lower waveguide 3 and the middle waveguide 2, respectively. The mechanical adjustment module is connected to the precision electronically controlled horizontal displacement stage.

[0024] Step 3: The mechanical control module controls the horizontal movement of the precision electronically controlled horizontal displacement stage to achieve continuous adjustment of the waveguide spacing;

[0025] The mechanical control module is electrically driven, knob-driven, or slide rail-driven.

[0026] Thirdly, the present invention also provides an electrical control method for the coupling spacing of a terahertz arbitrary ratio adjustable power divider with actuator based on a subwavelength Bragg grating, specifically including the following steps:

[0027] Step 1: Attach one end of the actuator 17 to the base 18, and attach the other end to the silicon plates above the upper waveguide 1 and below the lower waveguide 3 respectively.

[0028] Step 2: Lay a flexible electric heating sheet under the actuator 17, and apply voltages V1 and V2 to the heating sheet to heat and expand the actuator 17;

[0029] Step 3: The temperature of the flexible electric heating element is controlled by electrical regulation, thereby regulating the expansion degree of actuator 17, thus realizing continuous control of waveguide spacing.

[0030] Furthermore, the actuator 17 is a composite material actuator formed by polydimethylsiloxane (PDMS) coating carbon nanotubes (CNTs), which has the property of expanding when heated.

[0031] Compared with the prior art, the advantages of the present invention are as follows:

[0032] (1) This invention realizes a three-waveguide power divider with arbitrary ratio by adjusting the coupling spacing between waveguides; by introducing a fixing device and a mechanical adjustment module to adjust the waveguide spacing, the power distribution ratio can be continuously adjusted.

[0033] (2) Compared with traditional power dividers, this invention greatly reduces the coupling length of the waveguide by using a subwavelength grating waveguide as the coupling part structure; in addition, by changing the period and duty cycle of the subwavelength grating structure, the refractive index of the waveguide can be changed, which has more flexible control freedom and continuous switching function of arbitrary power division ratio.

[0034] (3) Compared with the more compact terahertz topological waveguide, the present invention introduces a subwavelength grating waveguide, which has a stronger ability to constrain the input power and reduces the power components that diffuse outward, thereby reducing the loss of the power divider; in addition, the entire power divider is composed of passive materials, with no additional energy consumption and no standby power consumption, which is in line with the concept of green environmental protection.

[0035] (4) Based on mechanical control, this invention proposes an electrical control method based on microelectromechanical actuators, which further improves the integration of devices.

[0036] (5) The packaging method proposed in this invention can also be used for other terahertz on-chip devices, and has certain inspirational significance for the packaging of terahertz on-chip devices. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0038] Figure 1 This is a schematic diagram of a terahertz arbitrary ratio adjustable power divider based on a subwavelength grating waveguide according to the present invention:

[0039] From top to bottom, the waveguides are: upper waveguide 1, middle waveguide 2, and lower waveguide 3; from left to right, they are divided into input signal unit 4, coupling unit 5, and output signal unit 6. The waveguide structures are all made of silicon material. The dark blue shaded area is the equivalent dielectric structure. The black shaded area 17 is a microelectromechanical actuator, which is made of a mixture of polydimethylsiloxane (PDMS) and carbon nanotubes (CNTs). The two ends of the actuator 17 are connected to the equivalent dielectric structure and the base 18, respectively.

[0040] Figure 2 This is a schematic diagram of the subwavelength grating structure of the coupling part of the present invention;

[0041] The strip waveguide 10 has a length 4-6 times the wavelength of the power divider's operating center frequency, and a width 1 / 13-1 / 11 of the wavelength of the power divider's operating center frequency. The sawtooth height of the first adiabatic subwavelength grating 11 and the third adiabatic subwavelength grating 13 increases linearly with the increase of horizontal distance, while the sawtooth height of the second adiabatic subwavelength grating 12 decreases linearly with the increase of horizontal distance. The grating duty cycle is 1 / 2, and the period is 1 / 7-1 / 6 of the wavelength of the power divider's operating center frequency.

[0042] Figure 3 This is a schematic diagram of the effective dielectric waveguide structure of the present invention;

[0043] The effective medium hole has a period a of 0.1 mm and a diameter d of 0.09 mm.

[0044] Figure 4 This is a schematic diagram of the packaging structure of the present invention;

[0045] The components, from bottom to top, are: base 18, power divider, and top cover 19. A small hole 20 on the side of the base is used to connect the upper waveguide 1 to change its spacing with the middle waveguide 2. Similarly, a small hole 21 on the corresponding part is used to connect the lower waveguide 3 to change its spacing with the middle waveguide 2. A small hole 21 in the center of the top cover is used to observe the spacing between the waveguides inside the package. A small hole 23 is the screw hole required to fix the middle waveguide 2 to the base 18.

[0046] Figure 5 The simulation 3D diagram shows the power distribution ratio corresponding to different waveguide spacings in this invention.

[0047] Wherein, G1 and G2 represent the spacing between the upper waveguide 1 and the middle waveguide 2, and the spacing between the lower waveguide 3 and the middle waveguide 2, respectively; the measured frequency domain is 129.5-131.5 GHz, the waveguide spacing varies from 0.1 to 1.1 mm, as the spacing increases, the output power ratio of the middle waveguide 2 first decreases and then increases, with a variation range of 8%-100%, and the output power ratio of the upper waveguide 1 and the lower waveguide 3 varies from 0% to 90%. By adjusting the spacing between the upper waveguide 1 and the middle waveguide 2, and the spacing between the lower waveguide 3 and the middle waveguide 2, any power distribution ratio can be achieved.

[0048] Figure 6 This is a schematic diagram of the testing environment for the sample of the present invention;

[0049] Arrows 24 and 25 indicate the directions of horizontal movement of the upper waveguide 1 and the lower waveguide 3, respectively. Mechanical control is achieved by using a precision electronically controlled horizontal displacement stage to adjust the waveguide spacing. Electronic control is achieved by applying voltages V1 and V2 to the microelectromechanical actuators to adjust the waveguide spacing. Detailed Implementation

[0050] To clearly and completely describe the technical solution and its specific working process of the present invention, the specific embodiments of the present invention are as follows, in conjunction with the accompanying drawings:

[0051] Example 1

[0052] like Figure 1 As shown, this embodiment provides a terahertz power divider with arbitrary ratio adjustable based on a subwavelength Bragg grating. The power divider consists of three coplanar silicon waveguides placed side by side. The three coplanar silicon waveguides are, from top to bottom, an upper waveguide 1, a middle waveguide 2, and a lower waveguide 3. The upper part of the upper waveguide 1 and the lower part of the lower waveguide 3 are respectively connected to a control device or actuator 17. The coupling spacing between the waveguides is adjusted by the control device or actuator, thereby realizing a power divider with arbitrary ratio and continuous adjustability.

[0053] The power divider is divided into an input signal unit 4, a coupling unit 5, and an output signal unit 6 from left to right. The input signal unit 4 consists of a signal feed pin 7, a tapered waveguide 8, and a subwavelength grating 9 connected in sequence. The coupling unit 5 consists of three strip waveguides 10 and three adiabatic subwavelength gratings with gradually varying sawtooth heights. The output signal unit 6 consists of a subwavelength grating waveguide 14, a curved waveguide 15, and a signal output pin 16 connected in sequence. The curved waveguide 15 has a shape that follows a cosine curve.

[0054] The upper waveguide 1, the middle waveguide 2, and the lower waveguide 3 are all located within the encapsulation structure, which includes a base 18 and a top cover 19. The middle waveguide 2 is fixed to the base 18 through an equivalent dielectric structure. The coupling portion between the middle waveguide 2 and the upper waveguide 1 and the lower waveguide 3 is air, and the spacing between the middle waveguide 2 and the upper waveguide 1 and the lower waveguide 3 can be continuously adjusted.

[0055] Both the base 18 and the top cover 19 are made of brass. The horizontal and vertical spacing between the base 18 and the top cover 19 and the waveguide should be appropriate, and the electromagnetic interference to the waveguide transmission performance can be ignored. The base 18 has two small holes on its side, which are used to control the distance between the upper waveguide 1 and the middle waveguide 2, and between the lower waveguide 3 and the middle waveguide 2, respectively. The top cover 19 has a small square hole 22 in the center to facilitate observation of the spacing between the waveguides inside the package. The base 18 and the middle waveguide 2 are fixed together using screw holes 23.

[0056] In this embodiment, the terahertz arbitrary ratio adjustable power divider operates in the frequency range of 129.5-131.5 GHz. The terahertz arbitrary ratio adjustable power divider uses high-resistivity silicon (resistivity > 10 kΩ) as its material.

[0057] The intermediate waveguide 2 is self-supported using an equivalent dielectric structure; the upper side of the upper waveguide 1 and the lower side of the lower waveguide 3 are self-supported using an equivalent dielectric structure; the upper waveguide 1, the intermediate waveguide 2, the lower waveguide 3, and the equivalent dielectric structure are all manufactured on a high-resistivity silicon wafer using a deep silicon etching process.

[0058] The equivalent dielectric air hole has a period of 0.1 mm and a diameter of 0.09 mm, which can provide a self-supporting structure for the chip and effectively suppress the diffusion of energy flow within the waveguide.

[0059] The waveguide structure has strong robustness and can achieve the same function when the shape of the equivalent dielectric air hole is elliptical or circular with a radius length deviation of less than 5%, which can reduce the requirements of the device for processing technology.

[0060] The lengths of both the signal feed pin 7 and the signal output pin 16 are 6 mm.

[0061] The three adiabatic subwavelength gratings with gradually varying sawtooth heights include a first adiabatic subwavelength grating 11, a second adiabatic subwavelength grating 12, and a third adiabatic subwavelength grating 13; wherein the sawtooth heights of the first adiabatic subwavelength grating 11 and the third adiabatic subwavelength grating 13 increase linearly with increasing horizontal distance, and the sawtooth heights of the second adiabatic subwavelength grating 12 decrease linearly with increasing horizontal distance.

[0062] Specifically, the sawtooth height y1 of the first adiabatic subwavelength grating 11 and the third adiabatic subwavelength grating 13 varies with the horizontal distance x as follows: y1 = 0.01625x + 0.425; the sawtooth height y2 of the second adiabatic subwavelength grating 12 varies with the horizontal distance x as follows: y2 = -0.015x + 0.85.

[0063] In this embodiment, the subwavelength grating 9, the first adiabatic subwavelength grating 11, the second adiabatic subwavelength grating 12, the third adiabatic subwavelength grating 13, and the subwavelength grating waveguide 14 are all composed of periodic cuboid structures. The periodic length of the periodic cuboid structures in the gratings 9, 11, 12, and 13 is 0.34 mm, and the duty cycle is 1 / 2.

[0064] In this embodiment, the sawtooth height in the subwavelength grating 9 is 0.85 mm; the sawtooth height in the subwavelength grating waveguide 14 is 0.646 mm.

[0065] The tapered waveguide 8 has a length of 20.4 mm; the strip waveguide 10 has a length of 13.6 mm and a width of 0.17 mm.

[0066] The packaging structure is designed according to electromagnetic compatibility principles, and the packaging structure does not affect the function of the power divider device.

[0067] The principle of the all-silicon terahertz power divider with arbitrary ratio adjustable based on a subwavelength Bragg grating in this embodiment is as follows:

[0068] For silicon waveguides without subwavelength grating structures, there is a fixed relationship between the coupling coefficient and the coupling length, which can be obtained from coupled-mode theory:

[0069]

[0070] Where W is the waveguide width, h is the waveguide height, d is the distance between the two waveguides, β is the mode phase, and κ is the waveguide width. c L is the coupling coefficient. c The coupling length is the coupling coefficient. The coupling coefficient decreases exponentially with the increase of the distance between the two waveguides, while the coupling length is inversely proportional to the coupling coefficient. The coupling length is related to the power distribution ratio of the device. Therefore, by adjusting the coupling distance, the power distribution ratio of the device can be significantly controlled.

[0071] In addition, the coupling length can also be expressed as:

[0072]

[0073] Where n2 and n0 are the effective refractive indices of the two lowest symmetric modes supported by the three-waveguide coupler, respectively. The subwavelength grating can effectively improve the coupling strength of the TE mode, thereby reducing the coupling length. Due to its special structure, the subwavelength grating waveguide has a different refractive index than the traditional silicon waveguide; its effective refractive index can be written as:

[0074]

[0075] Where, n H and n L Λ represents the refractive index of the high-refractive-index region and the low-refractive-index region of the subwavelength grating, respectively, Λ is the length of one period, and a is the length of the cuboid silicon pillar within one period.

[0076] Therefore, subwavelength grating silicon waveguides offer richer degrees of freedom than traditional silicon waveguides, adding parameters such as period and duty cycle. Adjusting these parameters allows for more flexible changes in the coupling strength between different silicon waveguides. Mechanical control of the distance between waveguides enables arbitrary power distribution ratios. Due to the inherent advantages of rapid response and static locking in mechanical control, any power distribution ratio can be maintained for extended periods and continuously adjusted. Furthermore, compared to the more compact terahertz topology waveguides, the introduction of subwavelength grating waveguides provides stronger constraint on input power, reducing outward power diffusion and thus lowering power divider losses. Combining these principles and methods enables the realization of an arbitrary-ratio, continuously adjustable, low-loss three-waveguide power divider.

[0077] Example 2

[0078] This embodiment provides a method for mechanically controlling the coupling spacing of an all-silicon terahertz power divider with arbitrarily adjustable ratio based on a subwavelength Bragg grating, specifically including the following steps:

[0079] Step 1: Construct the control device, which includes a fixed device, a precision electrically controlled horizontal displacement stage, and a mechanical control module; the precision electrically controlled horizontal displacement stage is located on one side of the fixed device, and the mechanical control module is connected to the precision electrically controlled horizontal displacement stage;

[0080] Step 2: Fix the middle waveguide 2 on the base 18; connect the outer sides of the upper waveguide 1 and the lower waveguide 3 to the precision electronically controlled horizontal displacement stage, which are used to adjust the distance between the upper waveguide 1 and the middle waveguide 2 and the lower waveguide 3 and the middle waveguide 2, respectively. The mechanical adjustment module is connected to the precision electronically controlled horizontal displacement stage.

[0081] Step 3: The mechanical control module controls the horizontal movement of the precision electronically controlled horizontal displacement stage to achieve continuous adjustment of the waveguide spacing;

[0082] The mechanical control module is electrically driven, knob-driven, or slide rail-driven.

[0083] The mechanical control module has a minimum control unit of 1μm and a control range of 0-3mm, exhibiting high control accuracy and a large control range.

[0084] like Figure 5 As shown, this embodiment simulates a power divider based on a mechanical control method. The simulation frequency range of this embodiment is 129.5-131.5 GHz. By changing the spacing G1 between the upper waveguide 1 and the middle waveguide 2, and the spacing G2 between the lower waveguide 3 and the middle waveguide 2, the output power ratio of the three waveguides changes accordingly.

[0085] In the simulation experiment, the adjustment range of G1 and G2 was set to 0.1-1.1 mm.

[0086] When G1 and G2 are equal, as the spacing increases, the output power ratio of the intermediate waveguide 2 first decreases and then increases. When both G1 and G2 are 0.4mm, the output power ratio of the intermediate waveguide 2 is the smallest, at 8%. When G1 and G2 are increased to the point where there is no coupling between the waveguides, the output power ratio of the intermediate waveguide 2 is the largest, at 100%. A three-waveguide power division ratio with a controllable range of 0:1:0 to 0.46:0.08:0.46 can be achieved.

[0087] With the spacing G1 between the upper waveguide 1 and the middle waveguide 2 fixed, the spacing G2 between the lower waveguide 3 and the middle waveguide 2 is changed. As G2 increases, the output power ratio of both the upper waveguide 1 and the middle waveguide 2 increases; the output power ratio of the upper waveguide 1 and the lower waveguide 3 ranges from 0% to 90%.

[0088] In this embodiment, the loss of the power divider increases with the increase of G1 and G2, but remains below 18%. In contrast, in the prior art, power dividers based on terahertz topological waveguides typically generate losses of more than 40%, while the present invention can achieve lower losses.

[0089] By adjusting the spacing between the upper waveguide 1 and the middle waveguide 2, as well as the spacing between the lower waveguide 3 and the middle waveguide 2, a power divider with arbitrary ratio, continuous adjustability, and low loss can be realized. Existing technology has not yet realized a terahertz power divider with arbitrary ratio adjustable function.

[0090] Example 3

[0091] This embodiment provides a microelectromechanical control method for the coupling spacing of a terahertz arbitrary ratio adjustable power divider based on a subwavelength Bragg grating and implemented using actuator 17. It is proposed to realize an arbitrary power ratio adjustable power divider by adjusting the spacing between the upper waveguide 1 and the middle waveguide 2 and the spacing between the lower waveguide 3 and the middle waveguide 2 through microelectromechanical control.

[0092] The silicon waveguide structure in this embodiment is consistent with that described in Embodiment 1. The actuator 17 has a length of 45 mm and a width of 20 mm.

[0093] The specific control steps of the actuator-based microelectromechanical control method are as follows:

[0094] Step 1: Preparation of a carbon nanotube-PDMS composite actuator with electrothermal expansion properties: Carbon nanotube powder is mixed with a volatile organic solvent (preferably toluene) and the mixture is ultrasonically dispersed under ice bath conditions using a cell disruptor; PDMS monomer is mixed with a volatile solvent (preferably toluene) and the mixture is ultrasonically treated using an ultrasonic cleaner; the prepared carbon nanotube dispersion and PDMS monomer dispersion are mixed and treated using an ultrasonic cleaner; the mixture obtained in the above steps is magnetically stirred for 1 hour in a constant-temperature magnetically stirred water bath at an optimal temperature of 70°C to evaporate the toluene solvent; after adding the curing agent, the mixture is stirred on a magnetic stirrer for 10 minutes; the mass ratio of curing agent to PDMS monomer is 1:10; the mixture is placed in an oven for curing to obtain a homogeneous carbon nanotube-PDMS composite actuator with thermal expansion properties.

[0095] Step 2: Attach one end of actuator 17 to base 18, and attach the other end to the silicon plates above upper waveguide 1 and below lower waveguide 3 respectively; lay flexible electric heating pads under actuator 17, and apply voltages V1 and V2 to the heating pads to heat and expand actuator 17.

[0096] Step 3: The temperature of the flexible electric heating element is controlled by electrical regulation, thereby regulating the expansion degree of actuator 17, thus realizing continuous control of waveguide spacing.

[0097] The essence of microelectromechanical control is to change the distance between the upper waveguide 1 and the middle waveguide 2, as well as the distance between the lower waveguide 3 and the middle waveguide 2, by adjusting the degree of expansion of the actuator 17.

[0098] like Figure 5 As shown, this embodiment simulates a power divider based on a microelectromechanical (MEMS) drive control method. The simulation frequency range of this embodiment is 129.5-131.5 GHz. In the simulation, by changing the spacing G1 between the upper waveguide 1 and the middle waveguide 2, and the spacing G2 between the lower waveguide 3 and the middle waveguide 2, the output power ratio of the three waveguides changes accordingly, thereby achieving the simulation effect of MEMS control.

[0099] In the simulation experiment, the adjustment range of G1 and G2 was set to 0.1-1.1 mm.

[0100] The structural parameter settings and simulation results of the simulation experiment based on the microelectromechanical control method are consistent with the simulation experiment of the adjustable power divider based on the mechanical method in Example 2.

[0101] By using a microelectromechanical system (MEMS) to drive a carbon nanotube-PDMS composite material actuator, and thereby adjusting the spacing between the upper waveguide 1 and the middle waveguide 2, as well as the spacing between the lower waveguide 3 and the middle waveguide 2, a power divider with arbitrary ratio, continuous adjustability, and low loss can be realized.

[0102] Example 4

[0103] This embodiment provides a metal packaging method for a terahertz arbitrary ratio adjustable power divider based on a subwavelength grating waveguide.

[0104] like Figure 4 As shown, this embodiment provides a packaging method, where both the base 18 and the top cover 19 are made of brass. The intermediate waveguide 2 is fixed to the base 18 via screw holes 23. The outer sides of the upper waveguide 1 and the lower waveguide 3 are connected to a precision electrically controlled horizontal displacement stage, allowing adjustment of the spacing between the upper waveguide 1 and the intermediate waveguide 2, and between the lower waveguide 3 and the intermediate waveguide 2, respectively. The vertical distance between the base 18 and the waveguides is 2mm, the thickness is 2mm, and the bottom area is 87×53mm.

[0105] In this embodiment, the total length of the power divider sample is 87 mm;

[0106] In this embodiment, the dimensions of the top cover 19 are 87mm × 53mm × 1mm;

[0107] In this embodiment, the waveguide spacing is adjustable from 0 mm to 1.1 mm;

[0108] In the tests of mechanical and electrical control, the horizontal movement of the upper waveguide 1 and the lower waveguide 3 is continuous, which also leads to a continuous change in the power division ratio exhibited by the power divider. This allows for switching of the waveguide spacing and, consequently, the ability to continuously control the power division ratio of the three waveguides over a wide range. When the spacing between the upper waveguide 1 and the lower waveguide 3 is the same as that between the middle waveguide 2 and the lower waveguide 3, firstly, the spacing between the upper waveguide 1 and the lower waveguide 3 and the middle waveguide 2 is adjusted to 0, and the three waveguides are horizontally aligned; then the waveguide spacing is increased from 0... Figure 5It can be observed that the output power percentage of the middle waveguide 2 first decreases and then increases, ranging from 8% to 100%; while the output power of the upper waveguide 1 and the lower waveguide 3 first increases and then decreases, ranging from 0% to 90%. Subsequently, keeping the distance between the upper waveguide 1 and the middle waveguide 2 constant, as the distance between the lower waveguide 3 and the middle waveguide 2 gradually increases, the output power percentages of both the upper waveguide 1 and the middle waveguide 2 increase, while the output power percentage of the lower waveguide 3 decreases until it reaches 0. Therefore, a power divider with a large power ratio control range and good continuous control effect is achieved.

[0109] Example 5

[0110] like Figure 6 As shown, this embodiment provides an experimental environment for performance testing of the above-mentioned samples. The experimental environment consists of a control section and a testing section. The mechanical control section is implemented through a stepper motor control chassis and a precision electronically controlled horizontal displacement stage. The microelectromechanical control section is implemented by applying a stable power supply. The testing section is implemented by a control computer, a vector network analyzer, and a rectangular metal waveguide.

[0111] The control computer is the central control unit, connected to the vector network instrument via a network cable for signal transmission; the vector network instrument is a device for generating and receiving signals, using a rectangular metal waveguide for signal input and output; the stepper motor control chassis is used to control the precision electronically controlled horizontal displacement stage;

[0112] Mechanical control can adjust the horizontal movement of the upper and lower waveguides by using a precision electronically controlled horizontal displacement stage; electronic control can adjust the horizontal movement of the upper and lower waveguides by applying voltages V1 and V2 to the microelectromechanical actuator 17.

[0113] Arrows 24 and 25 indicate the directions of movement for the upper waveguide 1 and the lower waveguide 3, respectively.

[0114] The sample simulation platform is used to place the sample to be tested and the sample fixing device.

[0115] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. The present invention has been universally explained in terms of the structural design of the subwavelength grating waveguide, the signal input part, and the application principle of signal coupling.

[0116] It should also be noted that the specific size ranges described in the above-mentioned specific power divider parameter size design can be combined with suitable values ​​within any size range without increasing the design and manufacturing difficulty. In order to avoid unnecessary repetition, the application of power dividers with arbitrary adjustable power ratios in other terahertz frequency bands will not be described separately.

[0117] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A fully-silicon terahertz arbitrary-ratio tunable power divider based on subwavelength Bragg gratings, characterized in that, The power divider is composed of three parallelly placed coplanar silicon waveguides, which are upper waveguide (1), middle waveguide (2) and lower waveguide (3) from top to bottom, and the upper side of the upper waveguide (1) and the lower side of the lower waveguide (3) are connected with the control device or actuator (17) respectively; the coupling distance between the waveguides is controlled by the mechanical control device or actuator, so as to realize the power divider with arbitrary ratio and continuous adjustment; Wherein, the power divider is divided into input signal unit (4), coupling unit (5) and output signal unit (6) from left to right; wherein, the input signal unit (4) is composed of signal feeding pin (7), tapered waveguide (8) and subwavelength grating (9) connected in turn; the coupling unit (5) is composed of three strip waveguides (10) and three adiabatic subwavelength gratings with gradually changing sawtooth height; the output signal unit (6) is composed of subwavelength grating waveguide (14), curved waveguide (15) and signal output pin (16) connected in turn; the structure shape of the curved waveguide (15) follows the cosine curve; The electric control method based on the coupling distance of the power divider, specifically includes the following steps: Step one: one end of the actuator (17) is adhered to the base (18), and the other end is adhered to the silicon plate above the upper waveguide (1) and below the lower waveguide (3) respectively; Step two: lay a flexible electric heating sheet under the actuator (17), and apply voltage V1 and V2 to the heating sheet to heat and expand the actuator (17); Step three: control the temperature of the flexible electric heating sheet by electric control, and then control the expansion degree of the actuator (17), so as to realize the continuous control of the waveguide distance; Wherein, the actuator (17) is a composite material actuator formed by polydimethylsiloxane coated carbon nanotubes, which has the property of expanding when heated.

2. The all-silicon terahertz arbitrary-ratio tunable power divider based on a subwavelength Bragg grating of claim 1, wherein, The upper waveguide (1), the middle waveguide (2) and the lower waveguide (3) are all located in the packaging structure, wherein the packaging structure includes base (18) and top cover (19), the middle waveguide (2) is fixed on the base (18) through the equivalent medium structure, and the coupling part between the middle waveguide (2) and the upper waveguide (1) and the lower waveguide (3) is air, so the distance between the middle waveguide (2) and the upper waveguide (1) and the lower waveguide (3) can be continuously adjusted.

3. The all-silicon terahertz arbitrary-ratio tunable power divider based on a subwavelength Bragg grating of claim 1, wherein, The base (18) and the top cover (19) are both brass materials, and the horizontal and vertical distance between the base (18) and the top cover (19) and the waveguide should be appropriate, and the electromagnetic interference to the waveguide transmission performance can be ignored; two small holes are arranged on the side of the base (18), which are used to control the distance between the upper waveguide (1) and the middle waveguide (2) and the lower waveguide (3) and the middle waveguide (2); there is a square hole (22) in the center of the top cover (19), so as to observe the distance between the waveguides in the packaging; the base (18) and the middle waveguide (2) are fixed by using screw hole (23).

4. The all-silicon terahertz arbitrary-ratio tunable power splitter based on a subwavelength Bragg grating of claim 1, wherein, The intermediate waveguide (2) is self-supported by an equivalent medium structure; the upper side of the upper waveguide (1) and the lower side of the lower waveguide (3) are self-supported by equivalent medium structures; the upper waveguide (1), the intermediate waveguide (2), the lower waveguide (3) and the equivalent medium structures are all manufactured on a high-resistance silicon wafer by using a deep silicon etching process.

5. The all-silicon terahertz arbitrary-ratio tunable power splitter based on a subwavelength Bragg grating of claim 2, wherein, The period of the equivalent medium air hole of the equivalent medium structure is 1 / 24-1 / 23 of the wavelength of the working center frequency of the power divider, and the air hole diameter is 1 / 26-1 / 25 of the wavelength of the working center frequency of the power divider, which can provide a self-supporting structure of the chip and effectively suppress the diffusion of the energy flow in the waveguide. The waveguide has strong robustness, and the same function is realized when the shape of the equivalent medium air hole is an ellipse or the radius length deviates within 5%, thereby reducing the requirement of the device on the processing technology.

6. The all-silicon terahertz arbitrary-ratio tunable power divider based on a subwavelength Bragg grating of claim 1, wherein, The three sawtooth height-gradually-changing adiabatic subwavelength gratings include a first adiabatic subwavelength grating (11), a second adiabatic subwavelength grating (12) and a third adiabatic subwavelength grating (13); the sawtooth height of the first adiabatic subwavelength grating (11) and the third adiabatic subwavelength grating (13) increases linearly with the increase of the horizontal distance, and the sawtooth height of the second adiabatic subwavelength grating (12) decreases linearly with the increase of the horizontal distance.

7. The all-silicon terahertz arbitrary-ratio tunable power splitter based on a subwavelength Bragg grating of claim 1, wherein, The subwavelength grating (9), the first adiabatic subwavelength grating (11), the second adiabatic subwavelength grating (12), the third adiabatic subwavelength grating (13) and the subwavelength grating waveguide (14) are all composed of periodic cuboid structures, and the period length of the periodic cuboid structure of the above gratings is 1 / 7-1 / 6 of the wavelength of the working center frequency of the power divider, and the duty cycle is 1 / 2; The length of the signal feeding pin (7) and the signal output pin (16) is 3-4 times the wavelength of the working center frequency of the power divider.

8. The all-silicon terahertz arbitrary-ratio tunable power splitter based on a subwavelength Bragg grating of claim 1, wherein, The sawtooth height in the subwavelength grating (9) is 1 / 3-1 / 2 of the wavelength of the working center frequency of the power divider; The length of the strip waveguide (10) is 4-6 times the wavelength of the working center frequency of the power divider, and the width of the strip waveguide (10) is 1 / 13-1 / 11 of the wavelength of the working center frequency of the power divider; The sawtooth height in the subwavelength grating waveguide (14) is 1 / 4-1 / 3 of the wavelength of the working center frequency of the power divider; The length of the actuator (17) is 11-14 times the wavelength of the working center frequency of the power divider.

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