Sub-wavelength Bragg grating-based all-silicon terahertz arbitrary ratio adjustable power divider and regulation and control method thereof

Abstract

The invention discloses an all-silicon terahertz arbitrary ratio adjustable power divider based on a sub-wavelength Bragg grating and a regulation and control method of the all-silicon terahertz arbitrary ratio adjustable power divider, and belongs to the technical field of terahertz on-chip circuit regulation and control. The three coplanar silicon waveguides which are arranged in parallel are an upper waveguide, a middle waveguide and a lower waveguide in sequence from top to bottom; the upper part of the upper waveguide and the lower part of the lower waveguide are respectively connected with a mechanical regulation and control device or an actuator; the coupling spacing between waveguides is regulated and controlled through a mechanical regulation and control device or an actuator, so that the power divider with any ratio and continuous adjustability is realized; according to the invention, nonlinear change of coupling strength among different waveguides is caused by change of coupling spacing among the sub-wavelength adiabatic grating waveguides, so that the ratio of output power of different waveguides is changed, good performance is achieved in a terahertz wave band, a sub-wavelength grating structure and a three-waveguide coupling structure are introduced, and the coupling strength of the three waveguides is improved. The coupling spacing between waveguides is regulated and controlled, so that the power divider with any ratio and continuous adjustability is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz on-chip circuit control, and in particular relates to an all-silicon terahertz arbitrary ratio adjustable power divider based on a sub-wavelength Bragg grating and a control method thereof. Background Art

[0002] With the development of terahertz on-chip integrated circuits, terahertz on-chip integrated circuits have excellent performance in realizing 6G wireless communication, high-speed on-chip interconnection, low-loss transmission, and highly compact devices. On-chip power dividers (referred to as power dividers) are one of the key devices in large-scale photonic integrated circuits and are essential components in many scenarios, including optical switches, modulators, wavelength division multiplexers, optical phase arrays, optical neural networks, etc. Continuously adjustable arbitrary ratio power dividers can freely adjust the power distribution ratio of different branches in some way, and can provide a variety of power distribution solutions for different application requirements, with a wider range of application scenarios.

[0003] At present, a variety of structures have been proven to be able to achieve the function of power distribution, including directional couplers, multimode interference couplers, pseudosurface plasmon subwavelength waveguides, Y junctions, photonic crystal waveguides and other structures. For existing adjustable power dividers, there are mainly two methods, namely electrical control and optical control. Electrical control refers to adding electronic components (varactors, PIN diodes, etc.) to electronic integrated circuits in low-frequency ranges such as microwaves, and achieving small-range power division ratio adjustment by changing the on and off of electronic components; optical control refers to applying optical pumping to on-chip silicon waveguide devices, and adjusting the power division ratio by changing the properties of light-responsive materials. In addition, the power division ratio can also be adjusted by changing the device structure design. These methods can only achieve the regulation of the power division ratio to a certain extent, but there are still some inevitable defects to achieve the ability to continuously adjust the arbitrary ratio power division within the terahertz frequency range (or even higher frequencies). These defects include: 1. In the terahertz frequency band, the intrinsic cutoff frequency of semiconductor materials causes semiconductor devices to fail and cannot reproduce the regulation of electronic devices by microwave frequencies; 2. Applying optical pumping to the silicon waveguide system introduces additional energy loss, and the optical pumping system is difficult to integrate; 3. Changing the structure of the device itself in design cannot achieve continuous adjustability in actual use.

[0004] At present, existing work has made some progress in this field, but arbitrary ratio, continuously adjustable, and low-loss power dividers are still key devices for further development in this field, so a simple and ingenious design idea is needed to integrate these three advantages. Based on the above analysis, the research and design of a new adjustable arbitrary ratio power divider that meets the above requirements is related to the development and potential application of terahertz integrated circuits. Summary of the invention

[0005] In view of the above-mentioned defects existing in the prior art, the present invention provides an all-silicon terahertz power divider with arbitrary ratio adjustable based on subwavelength Bragg grating and its control method. The present invention causes nonlinear changes in the coupling strength between different waveguides by changing the coupling spacing between subwavelength adiabatic grating waveguides, thereby changing the output power ratio of different waveguides, and has good performance in the terahertz band. The present invention introduces a subwavelength grating structure and a three-waveguide coupling structure, and realizes a power divider with arbitrary ratio and continuous adjustable by adjusting the coupling spacing between waveguides.

[0006] The present invention is achieved through the following technical solutions:

[0007] An all-silicon terahertz power divider with arbitrary ratio adjustable based on subwavelength Bragg grating, the power divider is composed of three coplanar silicon waveguides placed in parallel, the three coplanar silicon waveguides placed in parallel 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 an actuator 17; the coupling spacing between the waveguides is controlled by the control device or the actuator, so as to realize a power divider with arbitrary ratio and continuous adjustable;

[0008] Among them, 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; wherein the input signal unit 4 is composed of a signal feeding pin 7, a tapered waveguide 8 and a sub-wavelength grating 9 connected in sequence; the coupling unit 5 is composed of three strip waveguides 10 and three adiabatic sub-wavelength gratings with a gradual sawtooth height; the output signal unit 6 is composed of a sub-wavelength grating waveguide 14, a curved waveguide 15 and a signal output pin 16 connected in sequence; the structural shape of the curved waveguide 15 follows a cosine curve.

[0009] Furthermore, the upper waveguide 1, the intermediate waveguide 2 and the lower waveguide 3 are all located in a packaging structure, wherein the packaging structure includes a base 18 and a top cover 19, the intermediate waveguide 2 is fixed on the base 18 through an equivalent dielectric structure, and there is air between the coupling parts of the intermediate waveguide 2 and the upper waveguide 1 and the lower waveguide 3, so that the spacing between the intermediate waveguide 2 and the upper waveguide 1 and the lower waveguide 3 can be continuously adjusted.

[0010] Furthermore, the base 18 and the top cover 19 are both made of brass material, and 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; two small holes are set 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 distance between the lower waveguide 3 and the middle waveguide 2 respectively; there is a square small hole 22 in the center of the top cover 19 to facilitate observation of the spacing between the waveguides inside the package; the package base 18 and the middle waveguide 2 are fixed 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 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-resistance silicon wafer using a deep silicon etching process.

[0012] Furthermore, the period of the equivalent dielectric air holes of the equivalent dielectric structure is 1 / 24-1 / 23 of the wavelength of the working center frequency of the power divider, and the diameter of the air holes is 1 / 26-1 / 25 of the wavelength of the working center frequency of the power divider, which can not only provide a self-supporting structure of the chip, but also effectively suppress the diffusion of energy flow in 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 an ellipse or a circle with a radius length deviation of less than 5%, thereby reducing the requirements of the device on the 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 are linearly increasing with increasing horizontal distance, and the sawtooth height of the second adiabatic subwavelength grating 12 is linearly decreasing with increasing horizontal distance.

[0015] Further, the sub-wavelength grating 9, the first adiabatic sub-wavelength grating 11, the second adiabatic sub-wavelength grating 12, the third adiabatic sub-wavelength grating 13 and the sub-wavelength grating 14 are all composed of a periodic rectangular parallelepiped structure, and the period length of the periodic rectangular parallelepiped structure of the above grating is 1 / 7-1 / 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 working center frequency of the power divider.

[0017] Furthermore, the sawtooth height in the sub-wavelength grating 9 is 1 / 3-1 / 2 of the wavelength of the working center frequency of the power divider;

[0018] 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;

[0019] The sawtooth height in the sub-wavelength grating waveguide 14 is 1 / 4-1 / 3 of the wavelength of the working center frequency of the power divider;

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

[0021] In a second aspect, the present invention further provides a method for mechanically controlling the coupling spacing of an all-silicon terahertz power divider with an adjustable arbitrary ratio based on a sub-wavelength Bragg grating, which specifically comprises the following steps:

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

[0023] Step 2: fix the middle waveguide 2 on the base 18; the outer sides of the upper waveguide 1 and the lower waveguide 3 are connected to the precision electric control horizontal displacement stage, which are used to adjust the distance between the upper waveguide 1 and the middle waveguide 2 and the distance between the lower waveguide 3 and the middle waveguide 2 respectively, and the mechanical control module is connected to the precision electric control horizontal displacement stage;

[0024] Step 3: Control the horizontal movement of the precision electric-controlled horizontal displacement stage through the mechanical control module to achieve continuous control of the waveguide spacing;

[0025] Wherein, the mechanical control module is electrically driven, knob driven or slide rail driven.

[0026] In a third aspect, the present invention further provides a method for electrically controlling the coupling spacing of a terahertz arbitrary ratio adjustable power divider containing an actuator based on a sub-wavelength Bragg grating, which specifically comprises the following steps:

[0027] Step 1: Bond one end of the actuator 17 to the packaging base 18, and bond 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: Control the temperature of the flexible electric heating sheet through electrical regulation, and then regulate the expansion degree of the actuator 17, so as to achieve continuous regulation of the waveguide spacing.

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

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

[0032] (1) The present invention realizes a three-waveguide power divider with an arbitrary ratio by adjusting the coupling spacing between waveguides; the waveguide spacing is adjusted by introducing a fixing device and a mechanical control module, thereby realizing continuous control of the power distribution ratio;

[0033] (2) Compared with the traditional power divider, the present invention greatly reduces the coupling length of the waveguide by using a sub-wavelength grating waveguide as the coupling part structure; in addition, by changing the period and duty cycle of the sub-wavelength grating structure, the refractive index of the waveguide is 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, reduces the power component that diffuses outward, and thus reduces the loss of the power divider; in addition, the components of the entire power divider are all passive materials, without additional energy consumption and standby energy consumption, which conforms to the concept of green environmental protection;

[0035] (4) The present invention takes mechanical control as a starting point and proposes an electrical control method based on a micro-electromechanical drive actuator. Based on the electrical control method, the integration of the device is further improved.

[0036] (5) The packaging method proposed in the present invention can also be used for other terahertz on-chip devices, and has certain implications for the packaging of terahertz on-chip devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. 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 according to the actual scale.

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

[0039] Among them, from top to bottom, they 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 structure is realized by silicon material; the dark blue shaded part is the equivalent dielectric structure; the black shaded part 17 is a micro-electromechanical actuator, which is made of a mixture of polydimethylsiloxane (PDMS) and carbon nanotubes (CNTs), and the two ends of the actuator 17 are respectively connected to the equivalent dielectric structure and the base 18;

[0040] Figure 2 It is a schematic diagram of the sub-wavelength grating structure of the coupling part of the present invention;

[0041] 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 is 1 / 13-1 / 11 of the wavelength of the working center frequency of the power divider; the sawtooth height of the first adiabatic sub-wavelength grating 11 and the third adiabatic sub-wavelength grating 13 increases linearly with the increase of the horizontal distance, and the sawtooth height of the second adiabatic sub-wavelength grating 12 decreases linearly with the increase of the horizontal distance. The grating duty cycle is 1 / 2, and the period is 1 / 7-1 / 6 of the wavelength of the working center frequency of the power divider;

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

[0043] Among them, the period a of the effective medium hole is 0.1 mm, and the diameter d is 0.09 mm;

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

[0045] From bottom to top, there are base 18, power divider, and top cover 19; the small hole 20 on the side of the base is used to connect the upper waveguide 1 so as to change the distance between it and the middle waveguide 2; similarly, the corresponding part has a small hole 21 for connecting the lower waveguide 3 so as to change the distance between it and the middle waveguide 2; the small hole 21 in the center of the top cover is used to observe the distance between the waveguides inside the package; the small hole 23 is the screw hole required for fixing the middle waveguide 2 and the base 18;

[0046] Figure 5 It is a simulated 3D diagram of power distribution ratio corresponding to different waveguide spacings of the present invention;

[0047] Among them, 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 129.5-131.5Ghz, the waveguide spacing varies in the range of 0.1-1.1mm, and as the spacing increases, the output power proportion of the middle waveguide 2 first decreases and then increases, with a variation range of 8%-100%, and the output power proportion of the upper waveguide 1 and the lower waveguide 3 varies in the range of 0-90%. 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, power distribution of any ratio can be achieved.

[0048] Figure 6 Schematic diagram of the test environment of the sample of the present invention;

[0049] Among them, arrow 24 and arrow 25 respectively indicate the directions of horizontal movement of the upper waveguide 1 and the lower waveguide 3; mechanical control is achieved by using a precision electrically controlled horizontal displacement stage to control the waveguide spacing; electrical control is achieved by applying voltages V1 and V2 to the micro-electromechanical actuators to control the waveguide spacing. DETAILED DESCRIPTION

[0050] In order to clearly and completely describe the technical solution and its specific working process of the present invention, the specific implementation methods of the present invention are as follows in conjunction with the accompanying drawings of the specification:

[0051] Example 1

[0052] like Figure 1 As shown, this embodiment provides a terahertz power divider with arbitrary ratio adjustable based on sub-wavelength Bragg grating, the power divider is composed of three coplanar silicon waveguides placed in parallel, the three coplanar silicon waveguides placed in parallel are, from top to bottom, an upper waveguide 1, an intermediate 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 an actuator 17; the coupling spacing between the waveguides is controlled by the control device or the actuator, so as to realize a power divider with arbitrary ratio and continuous adjustable;

[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 is composed of a signal feed pin 7, a tapered waveguide 8 and a sub-wavelength grating 9 connected in sequence; the coupling unit 5 is composed of three strip waveguides 10 and three adiabatic sub-wavelength gratings with a gradual sawtooth height; the output signal unit 6 is composed of a sub-wavelength grating waveguide 14, a curved waveguide 15 and a signal output pin 16 connected in sequence; the structural shape of the curved waveguide 15 follows a cosine curve;

[0054] The upper waveguide 1, the middle waveguide 2 and the lower waveguide 3 are all located in a packaging structure, wherein the packaging structure includes a base 18 and a top cover 19, the middle waveguide 2 is fixed on the base 18 through an equivalent dielectric structure, and there is air between the coupling parts of the middle waveguide 2 and the upper waveguide 1 and the lower waveguide 3, so that the spacing between the middle waveguide 2 and the upper waveguide 1 and the lower waveguide 3 can be continuously adjusted.

[0055] The base 18 and the top cover 19 are both 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. Two small holes are set 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 distance between the lower waveguide 3 and the middle waveguide 2 respectively. There is a square hole 22 in the center of the top cover 19 to facilitate observation of the spacing between the waveguides inside the package. The package base 18 and the middle waveguide 2 are fixed using screw holes 23.

[0056] In this embodiment, the operating frequency range of the terahertz arbitrary ratio adjustable power divider is 129.5-131.5 GHz. The material used for the terahertz arbitrary ratio adjustable power divider is high-resistance silicon (resistivity>10 kΩ).

[0057] The intermediate waveguide 2 uses 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 use 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-resistance silicon wafer using a deep silicon etching process.

[0058] The period of the equivalent medium air holes is 0.1 mm, and the diameter of the air holes is 0.09 mm, which can not only provide a self-supporting structure for the chip, but also effectively suppress the diffusion of energy flow in 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 an ellipse or a circle with a radius length deviation of less than 5%, thereby reducing the requirements of the device on the processing technology.

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

[0061] The three adiabatic sub-wavelength gratings with gradually varying sawtooth heights include a first adiabatic sub-wavelength grating 11, a second adiabatic sub-wavelength grating 12 and a third adiabatic sub-wavelength grating 13; wherein the sawtooth heights of the first adiabatic sub-wavelength grating 11 and the third adiabatic sub-wavelength grating 13 are linearly increasing with increasing horizontal distance, and the sawtooth height of the second adiabatic sub-wavelength grating 12 is linearly decreasing with increasing horizontal distance.

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

[0063] In this embodiment, the sub-wavelength grating 9, the first adiabatic sub-wavelength grating 11, the second adiabatic sub-wavelength grating 12, the third adiabatic sub-wavelength grating 13 and the sub-wavelength grating 14 are all composed of a periodic rectangular structure, and the period length of the periodic rectangular structure 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 sub-wavelength grating 9 is 0.85 mm; the sawtooth height in the sub-wavelength grating 14 is 0.646 mm.

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

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

[0067] The principle of the all-silicon terahertz arbitrary ratio adjustable power divider based on sub-wavelength 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. According to the coupled mode theory, it can be obtained that:

[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, κ c is the coupling coefficient, L c is the coupling length. The coupling coefficient decreases exponentially with the increase of the distance between the two waveguides. The coupling length is inversely proportional to the coupling coefficient, and 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 adjusted.

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

[0072]

[0073] Among them, n 2 and n 0are the effective refractive indices of the two lowest symmetric modes supported by the three-waveguide coupler. Subwavelength gratings can effectively improve the coupling strength of the TE mode and thus reduce the coupling length. Due to its special structure, the refractive index of the subwavelength grating waveguide is different from that of the traditional silicon waveguide, and its effective refractive index can be written as:

[0074]

[0075] Among them, n H and n L They represent the refractive indices 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 rectangular silicon column within one period.

[0076] It can be seen that subwavelength grating silicon waveguides have more degrees of freedom than traditional silicon waveguides, and have added parameter variables such as period and duty cycle. By adjusting these parameters, the coupling strength between different silicon waveguides can be changed more flexibly. The distance between waveguides is controlled by mechanical regulation, so as to achieve the regulation of arbitrary power distribution ratio; due to the advantages of fast response and static locking of mechanical regulation itself, any power distribution ratio can be maintained for a long time and continuously regulated; in addition, compared with the more compact terahertz topological waveguide, the introduction of subwavelength grating waveguide has a stronger constraint on the input power, reduces the power component that diffuses outward, and thus reduces the loss of the power divider. Combining the above principles and methods, an arbitrary ratio, continuously adjustable, and low-loss three-waveguide power divider can be realized.

[0077] Example 2

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

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

[0080] Step 2: fix the middle waveguide 2 on the base 18; the outer sides of the upper waveguide 1 and the lower waveguide 3 are connected to the precision electric control horizontal displacement stage, which are used to adjust the distance between the upper waveguide 1 and the middle waveguide 2 and the distance between the lower waveguide 3 and the middle waveguide 2 respectively, and the mechanical control module is connected to the precision electric control horizontal displacement stage;

[0081] Step 3: Control the horizontal movement of the precision electric-controlled horizontal displacement stage through the mechanical control module to achieve continuous control of the waveguide spacing;

[0082] Wherein, the mechanical control module is electrically driven, knob driven or slide rail driven.

[0083] The minimum control unit of the mechanical control module is 1 μm, and the control range is 0-3 mm, with high control accuracy and 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 129.5-131.5Ghz. 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 is 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 G1 and G2 are both 0.4 mm, the output power ratio of the intermediate waveguide 2 is the smallest, which is 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, which is 100%. The three-waveguide power division ratio with a control range of 0:1:0-0.46:0.08:0.46 can be achieved;

[0087] The spacing G1 between the upper waveguide 1 and the middle waveguide 2 is fixed, and the spacing G2 between the lower waveguide 3 and the middle waveguide 2 is changed. As G2 increases, the output power ratios of the upper waveguide 1 and the middle waveguide 2 both increase; 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, and is maintained below 18%. In the prior art, the power divider based on terahertz topological waveguide usually produces a loss of more than 40%. In contrast, the present invention can achieve lower losses.

[0089] 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, a power divider with arbitrary ratio, continuous adjustment and low loss can be realized. The prior art has not yet realized a terahertz power divider with arbitrary ratio adjustable function.

[0090] Example 3

[0091] This embodiment provides a micro-electromechanical control method for the coupling spacing of a terahertz arbitrary ratio adjustable power divider based on a sub-wavelength Bragg grating and an actuator implemented using an actuator 17. It is intended to achieve an adjustable power divider with an arbitrary power division ratio by micro-electromechanically controlling 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.

[0092] The structure of the silicon waveguide 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 micro-electromechanical control method based on the actuator are as follows:

[0094] Step 1: Prepare a carbon nanotube-PDMS composite actuator with electrothermal expansion properties: mix carbon nanotube powder with a volatile organic solvent (preferably toluene) and use a cell crusher to ultrasonically disperse the mixture under ice bath conditions; mix PDMS monomer with a volatile solvent (preferably toluene) and use an ultrasonic cleaner to ultrasonically treat the mixture; mix the prepared carbon nanotube dispersion and PDMS monomer dispersion, and treat them with an ultrasonic cleaner; use a constant temperature magnetic stirring water bath pot, and magnetically stir the mixture obtained in the above steps for 1 hour under the condition of a constant temperature of 70°C to evaporate the toluene solvent; after adding the curing agent, stir it on a magnetic stirrer for 10 minutes; the mass ratio of the curing agent to the PDMS monomer is 1:10; put the mixture into an oven, and after curing, a homogeneous carbon nanotube-PDMS composite actuator with the property of thermal expansion can be obtained.

[0095] Step 2: One end of the actuator 17 is bonded to the packaging base 18, and the other end is bonded to the silicon plates above the upper waveguide 1 and below the lower waveguide 3 respectively; a flexible electric heating sheet is laid under the actuator 17, and voltages V1 and V2 are applied to the heating sheet to heat and expand the actuator 17;

[0096] Step 3: Control the temperature of the flexible electric heating sheet through electrical regulation, and then regulate the expansion degree of the actuator 17, so as to achieve continuous regulation of the waveguide spacing.

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

[0098] like Figure 5 As shown, this embodiment simulates a power divider based on a micro-electromechanical drive control method, and 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 micro-electromechanical control.

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

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

[0101] By driving the carbon nanotube-PDMS composite actuator with micro-electromechanical system, 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 can be adjusted, thereby realizing a power divider with arbitrary ratio, continuous adjustment and low loss.

[0102] Example 4

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

[0104] like Figure 4 As shown, this embodiment provides a packaging method, and the base 18 and the top cover 19 are both made of brass. The intermediate waveguide 2 is fixed to the base 18 through the screw hole 23, and the outer sides of the upper waveguide 1 and the lower waveguide 3 are connected to the precision electric control horizontal displacement stage, which can adjust the spacing between the upper waveguide 1 and the intermediate waveguide 2 and the spacing between the lower waveguide 3 and the intermediate waveguide 2 respectively. The vertical distance between the base 18 and the waveguide is 2mm, the thickness is 2mm, and the bottom area size is 87×53mm;

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

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

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

[0108] In the test of mechanical control and electrical control, the horizontal movement of the upper waveguide 1 and the lower waveguide 3 is continuous, which also leads to the continuous change of the power division ratio of the power divider, realizing the switching of the waveguide spacing, and then showing the large-scale continuous control of the power division ratio of the three waveguides. 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, first, adjust the spacing between the upper waveguide 1 and the lower waveguide 3 and the middle waveguide 2 to 0, and align the three waveguides horizontally; increase the distance between the waveguides from 0, and then Figure 5It can be observed that the output power ratio of the middle waveguide 2 first decreases and then increases, with a range of 8%-100%; the output power of the upper waveguide 1 and the lower waveguide 3 first increases and then decreases, with a range of 0-90%. Afterwards, the distance between the upper waveguide 1 and the middle waveguide 2 is controlled to remain unchanged. As the distance between the lower waveguide 3 and the middle waveguide 2 gradually increases, the output power ratios of the upper waveguide 1 and the middle waveguide 2 both increase, while the output power ratio of the lower waveguide 3 decreases until it reaches 0. Therefore, a power divider with a large power split 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, and the experimental environment is composed of a control part and a test part; the mechanical control part is realized by a stepper motor control chassis and a precision electric control horizontal displacement stage; the micro-electromechanical control part is realized by applying a stable power supply; the test part is realized by a control computer, a vector network instrument, and a rectangular metal waveguide.

[0111] The control computer is the master control device, which is connected to the vector network instrument through a network cable and transmits signals; the vector network instrument is a device that generates and receives signals, and inputs and outputs signals through a rectangular metal waveguide; the stepper motor control chassis is used to control the precision electric control horizontal displacement stage;

[0112] Mechanical control can be achieved by adjusting the horizontal movement position of the upper and lower waveguides through a precision electrically controlled horizontal displacement stage; electrical control can be achieved by applying voltages V1 and V2 to the micro-electromechanical actuator 17 to adjust the horizontal movement position of the upper and lower waveguides.

[0113] Arrow 24 and arrow 25 indicate the moving directions of 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 fixture.

[0115] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical scheme of the present invention can be subjected to a variety of simple deformations, and these simple deformations all belong to the protection scope of the present invention. The present invention has made a universal description under the structural design of the sub-wavelength grating waveguide, the signal input part and the application principle of signal coupling.

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

[0117] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. An all-silicon terahertz power divider with adjustable arbitrarily ratio based on sub-wavelength Bragg grating, characterized in that: The power divider is composed of three coplanar silicon waveguides placed in parallel, wherein the three coplanar silicon waveguides are, from top to bottom, an upper waveguide (1), a middle waveguide (2) and a lower waveguide (3), and 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 an actuator (17); the coupling spacing between the waveguides is controlled by a mechanical control device or an actuator, thereby realizing a power divider with an arbitrary ratio and continuous adjustability; 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 sub-wavelength grating (9) connected in sequence; the coupling unit (5) is composed of three strip waveguides (10) and three adiabatic sub-wavelength gratings with a gradual sawtooth height change; the output signal unit (6) is composed of a sub-wavelength grating waveguide (14), a curved waveguide (15) and a signal output pin (16) connected in sequence; the structural shape of the curved waveguide (15) follows a cosine curve.

2. The all-silicon terahertz arbitrary ratio adjustable power divider based on sub-wavelength Bragg grating according to claim 1, characterized in that: The upper waveguide (1), the middle waveguide (2) and the lower waveguide (3) are all located in a packaging structure, wherein the packaging structure comprises a base (18) and a top cover (19), the middle waveguide (2) is fixed on the base (18) through an equivalent dielectric structure, and air is provided between the coupling parts of the middle waveguide (2) and the upper waveguide (1) and the lower waveguide (3), so that the spacing 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 adjustable power divider based on sub-wavelength Bragg grating according to claim 1, characterized in that: The base (18) and the top cover (19) are both 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. Two small holes are arranged on the side of the base (18), which are respectively used to control the distance between the upper waveguide (1) and the middle waveguide (2) and the distance between the lower waveguide (3) and the middle waveguide (2). There is a square small hole (22) in the center of the top cover (19) to facilitate observation of the spacing between the waveguides inside the package. The package base (18) and the middle waveguide (2) are fixed using screw holes (23).

4. The all-silicon terahertz arbitrary ratio adjustable power divider based on sub-wavelength Bragg grating according to claim 1, characterized in that: 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 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-resistance silicon wafer using a deep silicon etching process.

5. The all-silicon terahertz arbitrary ratio adjustable power divider based on sub-wavelength Bragg grating according to claim 1, characterized in that: The period of the equivalent dielectric air hole of the equivalent dielectric structure is 1 / 24-1 / 23 of the wavelength of the working center frequency of the power divider, and the diameter of the air hole is 1 / 26-1 / 25 of the wavelength of the working center frequency of the power divider, which can not only provide a self-supporting structure of the chip, but also effectively suppress the diffusion of energy flow in the waveguide; The waveguide structure has strong robustness, and can achieve the same function when the shape of the equivalent dielectric air hole is an ellipse or a circle with a radius length deviation of less than 5%, thereby reducing the requirements of the device on the processing technology.

6. The all-silicon terahertz arbitrary ratio adjustable power divider based on sub-wavelength Bragg grating according to claim 1, characterized in that: The three adiabatic sub-wavelength gratings with gradually varying sawtooth heights comprise a first adiabatic sub-wavelength grating (11), a second adiabatic sub-wavelength grating (12), and a third adiabatic sub-wavelength grating (13); wherein the sawtooth heights of the first adiabatic sub-wavelength grating (11) and the third adiabatic sub-wavelength grating (13) are linearly increasing with increasing horizontal distance, and the sawtooth height of the second adiabatic sub-wavelength grating (12) is linearly decreasing with increasing horizontal distance.

7. The all-silicon terahertz arbitrary ratio adjustable power divider based on sub-wavelength Bragg grating according to claim 1, characterized in that: The sub-wavelength grating (9), the first adiabatic sub-wavelength grating (11), the second adiabatic sub-wavelength grating (12), the third adiabatic sub-wavelength grating (13) and the sub-wavelength grating (14) are all composed of a periodic rectangular parallelepiped structure, the period length of the periodic rectangular parallelepiped structure of the grating 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 lengths of the signal feed pin (7) and the signal output pin (16) are both 3-4 times the wavelength of the working center frequency of the power divider.

8. The all-silicon terahertz arbitrary ratio adjustable power divider based on sub-wavelength Bragg grating according to claim 1, characterized in that: The sawtooth height in the sub-wavelength 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 sub-wavelength 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.

9. A method for mechanically controlling the coupling spacing of an all-silicon terahertz power divider with an adjustable arbitrary ratio based on a sub-wavelength Bragg grating, which is implemented based on the power divider of claim 1, characterized in that: The specific steps include: Step 1: Build a mechanical control device, which includes a fixing device, a precision electric-controlled horizontal displacement stage and a mechanical control module; the precision electric-controlled horizontal displacement stage is located on one side of the fixing device, and the mechanical control module is connected to the precision electric-controlled horizontal displacement stage; Step 2: fix the middle waveguide (2) on the base (18); the outer sides of the upper waveguide (1) and the lower waveguide (3) are connected to a precision electrically controlled horizontal displacement stage, which is used to adjust the spacing between the upper waveguide (1) and the middle waveguide (2) and between the lower waveguide (3) and the middle waveguide (2), respectively; the mechanical control module is connected to the precision electrically controlled horizontal displacement stage; Step 3: Control the horizontal movement of the precision electric-controlled horizontal displacement stage through the mechanical control module to achieve continuous control of the waveguide spacing; Wherein, the mechanical control module is electrically driven, knob driven or slide rail driven.

10. A method for electrically controlling the coupling spacing of a terahertz arbitrary ratio adjustable power divider containing an actuator based on a sub-wavelength Bragg grating, which is implemented based on the power divider according to claim 1, characterized in that: The specific steps include: Step 1: Adhere one end of the actuator (17) to the packaging base (18), and adhere the other end to the silicon plates above the upper waveguide (1) and below the lower waveguide (3); Step 2: Laying a flexible electric heating sheet under the actuator (17), and applying voltages V1 and V2 to the heating sheet to heat and expand the actuator (17); Step 3: Control the temperature of the flexible electric heating sheet by electrical regulation, thereby regulating the expansion degree of the actuator (17), thereby achieving continuous regulation of the waveguide spacing; Wherein, the actuator (17) is a composite material actuator formed by polydimethylsiloxane-coated carbon nanotubes, and has the property of expanding when exposed to heat.

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