Device, method for measuring vibration modes of a nanoresonator at extremely low temperatures, and flexible waveguide

Abstract

The present invention belongs to the fields of microwaves and optics. To solve the problem that it is difficult to measure the vibration modes of a nanoresonator at extremely low temperatures, a device method for measuring the vibration modes of a nanoresonator at extremely low temperatures and a flexible waveguide are disclosed. The nanoresonator is mounted on a PCB circuit board, fixed on a five-axis displacement stage inside a cryostat, and communicates with an excitation power source and a frequency test device through a flexible waveguide and a coaxial cable. The excitation power source generates an excitation signal to cause the nanoresonator to vibrate. The laser generated by the laser is adjusted and incident into the cryostat. The five-axis displacement stage is moved so that the laser irradiates several points evenly distributed on different parts of the nanoresonator. By the change in the intensity of the reflected light at each point, the distance between the nanoresonator film and the substrate at that point is obtained, and the vibration mode of the nanoresonator is plotted.

Description

Technical Field

[0001] The present invention belongs to the fields of microwaves and optics, and relates to an apparatus and a method for measuring the vibration mode of a nanoresonator at extremely low temperatures. Background Art

[0002] Currently, the research on nanoresonators mainly focuses on room temperature. The power of nanoresonators is very small, and thermal noise will have a great impact on the measurement of the properties of the resonators. Therefore, some people have tried to measure the properties of nanoresonators at low temperatures. However, this idea has encountered many problems.

[0003] First, at room temperature, coaxial cables are generally used to transmit excitation signals and vibration signals. To meet impedance matching, the diameter of the coaxial cable is several millimeters, and the density is large, so that a relatively large power is required to move the nanoresonator, such as using a stepper motor. At low temperatures, if a nanoresonator connected to a coaxial cable is moved, the energy used will cause the cryostat to heat up rapidly, destroying the low-temperature environment.

[0004] Second, at room temperature, there is a large margin for optical path adjustment. The laser optical path and the position of the nanoresonator can be changed simultaneously so that the laser irradiates the nanoresonator at a required angle. In a cryostat, in order to minimize the entry of interfering light into the constant-temperature cavity and destroy the low-temperature environment, there is only a very small aperture in the optical window of the constant-temperature cavity. The adjustment range of the laser optical path is very limited, and mainly by moving the nanoresonator can the incident light conditions be met.

[0005] Third, after the measurement system is assembled at room temperature and then cooled to the experimental temperature, the deformation caused by the temperature change may cause the nanoresonator to deviate from its original position. If the position of the nanoresonator in the cryostat cannot be changed, the measurement accuracy will be affected.

[0006] Therefore, it is difficult for the prior art to measure the vibration mode of a nanoresonator at extremely low temperatures. Summary of the Invention

[0007] The purpose of the present invention is to solve the problem that it is difficult to measure the vibration mode of a nanoresonator at extremely low temperatures. The technical solution is as follows:

[0008] An apparatus for measuring the vibration mode of a nanoresonator at extremely low temperatures, comprising: a laser, an optical path adjuster, a semi-transparent and semi-reflective mirror, a light intensity measuring device, a cryostat, a five-axis displacement stage, a controller, a nanoresonator, a PCB circuit board, a plurality of flexible waveguides, a coaxial cable, an excitation power supply, a frequency measuring device, a controller, and a plurality of wires: wherein: the cryostat includes a constant temperature chamber, and a plurality of microwave transmission interfaces are provided both inside and outside the constant temperature chamber; the five-axis displacement stage, the PCB circuit board, and the nanoresonator are all placed in the constant temperature chamber; the PCB circuit board is arranged on the five-axis displacement stage; the nanoresonator is placed on the PCB circuit board and is connected to the PCB circuit board through wires for transmitting excitation signals and vibration signals; the PCB circuit board is connected to the microwave transmission interface inside the constant temperature chamber through a flexible waveguide; the microwave transmission interfaces outside the constant temperature chamber are connected to the excitation power supply and the frequency measuring device through coaxial cables respectively; the five-axis displacement stage is connected to the controller outside the constant temperature chamber through wires for transmitting control signals; the laser light emitted by the laser passes through the optical path adjuster and the semi-transparent and semi-reflective mirror and is incident into the constant temperature chamber, and the light reflected from the nanoresonator passes through the semi-transparent and semi-reflective mirror and is incident into the light intensity measuring device; the excitation power supply, the coaxial cable, the microwave transmission interface outside the constant temperature chamber, the microwave transmission interface inside the constant temperature chamber, the flexible waveguide, the PCB circuit board, and the nanoresonator are connected in sequence to form a closed loop; the nanoresonator, the flexible waveguide, the microwave transmission interface inside the constant temperature chamber, the microwave transmission interface outside the constant temperature chamber, the coaxial cable, and the frequency measuring device are connected in sequence to form a closed loop.

[0009] The working principle of the above apparatus for measuring the vibration mode of a nanoresonator at extremely low temperatures is as follows:

[0010] The nanoresonator in the constant temperature chamber is connected to the excitation power supply and the frequency measuring device to realize the excitation of the nanoresonator vibration and the measurement of its resonance frequency at extremely low temperatures. The laser passes through the optical path adjuster and is incident into the constant temperature chamber in a suitable state. The five-axis displacement stage with three translation axes and two rotation axes enables the laser to accurately irradiate the nanoresonator in the required manner. The displacement driving power of the nanoresonator is effectively reduced through the cryostat and the flexible waveguide, effectively ensuring the low-temperature environment. The laser is irradiated onto a number of points evenly distributed on different parts of the nanoresonator, and the reflected light intensity of each point is measured using the light intensity measuring device, and then the vibration mode of the nanoresonator can be plotted.

[0011] Preferred solution: The optical path adjuster includes: an adjustable attenuator, a single-mode optical fiber, and a double-convex lens focusing system; the laser light emitted by the laser is attenuated by the attenuator, then mode-selected by the single-mode optical fiber, and finally focused by the double-convex lens focusing system, and the beam waist of the laser is located near the nanoresonator in the constant temperature chamber.

[0012] Preferably, screw holes are reserved on the five-axis displacer, and screw holes are also provided at corresponding positions on the PCB circuit board. The PCB circuit board is fixed on the five-axis displacer with screws; the five-axis displacer drives the PCB circuit board and the nano-resonator to achieve pitching, deflection, and translation. The selected five-axis displacer includes three translational motion axes and two rotational axes.

[0013] The flexible waveguide of the above technical solution includes a flexible microstrip line and connectors respectively arranged at both ends of the flexible microstrip line;

[0014] The flexible microstrip line is a three-layer composite structure, successively composed of a metal conductor strip layer, a flexible dielectric layer, and a metal ground layer; the flexible dielectric layer is located between the metal conductor strip layer and the metal ground layer; the width of the metal ground layer is greater than the width of the metal conductor strip layer;

[0015] The metal conductor strip layer is connected to the anode of the connector, and the metal ground layer is connected to the cathode of the connector;

[0016] The width of the metal conductor strip layer and the characteristic impedance of the flexible microstrip line satisfy:

[0017]

[0018] where h is the thickness of the flexible dielectric layer, ε eff and w’ are defined as follows:

[0019]

[0020]

[0021] where w is the width of the metal conductor strip layer, t is the thickness of the metal conductor strip layer, and ε r is the relative dielectric constant of the flexible dielectric layer.

[0022] The width of the metal ground layer is 5 to 10 times or more the width of the metal conductor strip layer.

[0023] Another flexible waveguide can also be used. The flexible waveguide includes a coplanar waveguide and connectors respectively arranged at both ends of the coplanar waveguide;

[0024] The coplanar waveguide is composed of a flexible dielectric layer, a metal conductor strip layer, a first metal ground layer, and a second metal ground layer;

[0025] where the first metal ground layer, the metal conductor strip layer, and the second metal ground layer are laid on the flexible dielectric layer in a coplanar manner; the first metal ground layer and the second metal ground layer are symmetrically distributed on both sides of the metal conductor strip layer; the metal conductor strip layer is connected to the anode of the connector, and both the first metal ground layer and the second metal ground layer are connected to the cathode of the connector;

[0026] The width of the metal conductor strip layer, the width of the gap between the metal conductor strip layer and the first metal ground layer, and the characteristic impedance of the coplanar waveguide satisfy the following:

[0027]

[0028] where K is the complete elliptic integral of the first kind, ε eff , k, k’, kl, and kl’ are defined as follows:

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] where s is the width of the metal conductor strip layer, w is the width of the gap between the metal conductor strip layer and the first metal ground layer, h is the thickness of the flexible dielectric layer, and ε r is the relative dielectric constant of the flexible dielectric layer.

[0035] The width of the ground strip is at least 1 mm.

[0036] This application also provides a method for measuring the vibration mode of a nano-resonator in a cryostat, and the measurement steps are as follows:

[0037] 1) Connect the above-mentioned nano-resonator vibration measurement device as a whole;

[0038] 2) Turn on the laser and adjust the laser to make its intensity and beam waist position;

[0039] 3) Place the nano-resonator near the laser beam waist at room temperature;

[0040] 4) Turn off the laser;

[0041] 5) Place the constant temperature chamber in a light-shielded environment and lower the temperature of the constant temperature chamber to the experimental temperature;

[0042] 6) Use the excitation power supply to make the nano-resonator vibrate and use the frequency measurement device to measure its resonance frequency;

[0043] 7) Turn on the laser and use the five-axis displacer to move the nano-resonator so that the laser irradiates several points evenly distributed on different parts of the nano-resonator, and use the measurement optical path to measure the reflected light intensity of each point to draw the vibration mode of the nano-resonator.

[0044] The advantages of the above device and method for measuring the vibration mode of a nanoresonator at extremely low temperatures compared with the prior art are as follows:

[0045] 1. It can measure the vibration frequency and mode of a nanoresonator at extremely low temperatures simultaneously;

[0046] 2. It can accurately adjust the position of the nanoresonator in the constant temperature chamber, eliminate the situation that the nanoresonator deviates from the predetermined position due to deformation caused by temperature change, and reduce the measurement error;

[0047] 3. During the whole measurement process, there is no need to adjust the laser optical path, which improves the stability of the light source and the measurement accuracy;

[0048] 4. During the whole measurement process, there is no need to adjust the laser optical path, which can minimize the aperture on the optical window of the constant temperature chamber to the greatest extent, reduce the interfering light, and improve the measurement accuracy. Description of the Drawings

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art.

[0050] Figure 1 It is a schematic diagram of a device for measuring the vibration mode of a nanoresonator at extremely low temperatures;

[0051] Figure 2 It is a schematic diagram of a laser adjustment optical path;

[0052] Figure 3 It is a schematic diagram of a flexible waveguide used in a cryostat;

[0053] Figure 4 It is a partial cross-sectional view of the flexible waveguide transmission line;

[0054] Figure 5 It is a schematic diagram of another flexible waveguide used in a cryostat;

[0055] Figure 6 It is a partial cross-sectional view of the flexible waveguide transmission line;

[0056] Figure 7 It is an S11-frequency curve graph of a 20-cm flexible coplanar waveguide, flexible microstrip line, and coaxial cable at a temperature of 860 mK;

[0057] Figure 8 It is an S12-frequency curve graph of a 20-cm flexible coplanar waveguide, flexible microstrip line, and coaxial cable at a temperature of 860 mK;

[0058] Figure 9S21 - frequency curve graphs of a 20 - cm flexible coplanar waveguide, flexible microstrip line, and coaxial cable at a temperature of 860 mK;

[0059] Figure 10 S22 - frequency curve graphs of a 20 - cm flexible coplanar waveguide, flexible microstrip line, and coaxial cable at a temperature of 860 mK;

[0060] Figure 11 S11 - frequency curve graphs of a 20 - cm flexible coplanar waveguide at a temperature of 860 mK when the five - axis displacement stage is at different positions;

[0061] Figure 12 S12 - frequency curve graphs of a 20 - cm flexible coplanar waveguide at a temperature of 860 mK when the five - axis displacement stage is at different positions;

[0062] Figure 13 S21 - frequency curve graphs of a 20 - cm flexible coplanar waveguide at a temperature of 860 mK when the five - axis displacement stage is at different positions;

[0063] Figure 14 S22 - frequency curve graphs of a 20 - cm flexible coplanar waveguide at a temperature of 860 mK when the five - axis displacement stage is at different positions.

[0064] Among them:

[0065] 1 is a laser, 2 is an optical path adjuster, 3 is a semi - transparent and semi - reflecting mirror, 4 is a light intensity measuring device, 5 is a cryostat, 6 is a five - axis displacement device, 7 is a controller of the five - axis displacement device, 8 is a nano - resonator, 9 is a PCB circuit board, 10 is a flexible waveguide, 11 is a coaxial cable, 12 is an excitation power supply, 13 is a frequency measuring device; 14 is an adjustable attenuator, 15 is a single - mode optical fiber, 16 is a double - convex lens focusing system; 17 is a connector, 18 is a flexible microstrip line, 19 is a metal conductor strip layer, 20 is a flexible dielectric layer, 21 is a metal grounding layer; 22 is a flexible coplanar waveguide, 23 is a first metal grounding layer, 24 is a second metal grounding layer. Specific embodiments

[0066] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0067] Embodiment 1:

[0068] A device for measuring the vibration mode of a nano - resonator at extremely low temperatures, as shown in the attached Figure 1 figure, and the specific technical solutions are as follows:

[0069] An apparatus for measuring the vibration modes of a nanoresonator at extremely low temperatures, comprising: a laser 1, an optical path adjuster 2, a beam splitter 3, a light intensity measuring device 4, a cryostat 5, a five-axis displacement stage 6, a controller 7, a nanoresonator 8, a PCB circuit board 9, a flexible waveguide 10, a coaxial cable 11, an excitation power supply 12, a frequency measuring device 13, and several wires: The laser emits laser light that is incident into the cryostat through the optical path adjuster and the beam splitter, and the light reflected from the nanoresonator passes through the beam splitter and is incident on the light intensity measuring device; The nanoresonator is placed on the PCB circuit board and connected to the PCB circuit board using wires for transmitting excitation signals and vibration signals; The PCB circuit board is placed on the five-axis displacement stage; The flexible waveguide connects the PCB circuit board to the microwave transmission interface inside the cryostat; The coaxial cable connects the microwave transmission interface outside the cryostat to the excitation power supply or the frequency measuring device.

[0070] During use, molybdenum disulfide or other nanoresonators are adhered to the PCB circuit board, and the pins of the nanoresonator are bonded to the transmission lines on the PCB circuit board. The PCB circuit board is fixed to the five-axis displacement stage using screws. The five-axis displacement stage is connected to the controller outside the cryostat through wires. Turn on the laser, adjust the laser optical path to make the laser beam waist size and intensity appropriate and located at an appropriate position inside the cryostat. Place the five-axis displacement stage in the cryostat and make the laser beam waist located on the nanoresonator. Turn off the laser. Connect the PCB circuit board to the reserved microwave transmission interface on the inner wall of the cryostat using a flexible waveguide. Connect the corresponding microwave transmission interface on the outer wall of the cryostat to the excitation power supply or the frequency measuring device using a coaxial cable. Seal the cryostat, evacuate and cool it. After the internal temperature of the cryostat is lower than 1 K, use the excitation power supply to excite the vibration of the nanoresonator and use the frequency measuring device to measure it. After confirming that the system is operating well, turn on the laser, adjust the five-axis displacement stage to make the laser irradiate several points evenly distributed on different parts of the nanoresonator, and use the measuring optical path to measure the reflected light intensity at each point to plot the vibration mode of the nanoresonator. After the experiment is completed, turn off the laser and heat up the cryostat.

[0071] Example Two:

[0072] Based on the technical solution of Example One, the optical path adjuster is as shown in the attached Figure 2As shown in the figure, it includes: an adjustable attenuator 14, a single-mode optical fiber 15, and a bi-convex lens focusing system 16. During use, the laser emits light horizontally. Only the single-mode optical fiber is placed. An optical power meter is placed at the position of the system's output light. The single-mode optical fiber is adjusted to maximize the output power and make the output light horizontal. Remove the optical power meter. Place the bi-convex lens focusing system at the output position of the single-mode optical fiber. A mirror can be used for assistance to adjust the beam waist to a suitable position inside the cryostat. Finally, place the adjustable attenuator in front of the single-mode optical fiber and an optical power meter at the position of the beam waist. Adjust the attenuator to make the output light power meet the experimental requirements. This adjustment of the optical path needs to be carried out in a darkroom.

[0073] Example 3:

[0074] A method for measuring the vibration mode of a nano-resonator at extremely low temperatures. The steps for measuring the vibration mode of the nano-resonator using the above-mentioned device for measuring the vibration mode of the nano-resonator at extremely low temperatures are as follows:

[0075] 1) Connect the entire device in Example 1 well;

[0076] 2) Turn on the laser and adjust the laser using the optical path in Example 2 to make its intensity and beam waist position appropriate. This step needs to be carried out in a darkroom;

[0077] 3) Place the nano-resonator near the laser beam waist at room temperature;

[0078] 4) Turn off the laser;

[0079] 5) Place the thermostatic chamber in a light-shielded environment and lower the temperature of the thermostatic chamber to the experimental temperature;

[0080] 6) Use the excitation power supply to make the nano-resonator vibrate and use the frequency measurement device to measure its resonance frequency;

[0081] 7) Turn on the laser and use the five-axis displacement stage to move the nano-resonator so that the laser irradiates several points evenly distributed on different parts of the nano-resonator, and use the measurement optical path to measure the reflected light intensity of each point, and draw the vibration mode of the nano-resonator. This step needs to be carried out in a darkroom.

[0082] Example 4:

[0083] A method for measuring the vibration mode of a nano-resonator in a cryostat. The steps for measuring the interaction between the nano-resonator and the laser using the above-mentioned device for measuring the vibration mode of the nano-resonator at extremely low temperatures are as follows:

[0084] 1) Connect the entire device in Example 1 well;

[0085] 2) Turn on the laser and adjust the laser using the optical path in Example 2 to make its intensity and beam waist position appropriate. This step needs to be carried out in a darkroom;

[0086] 3) Place the nano-resonator near the laser beam waist at room temperature;

[0087] 4) Turn off the laser;

[0088] 5) Place the constant-temperature chamber in a light-shielded environment and lower the temperature of the constant-temperature chamber to the experimental temperature;

[0089] 6) Use an excitation power supply to vibrate the nano-resonator and use a frequency measurement device to measure its resonance frequency;

[0090] 7) Turn on the laser and use a five-axis displacer to move the nano-resonator so that it is irradiated by the laser at different angles and intensities, and use a frequency measurement device to measure its resonance frequency. This step needs to be carried out in a dark room.

[0091] Example Five:

[0092] After completing the measurements in Example Four, analyze the frequency data to obtain the relationship between the nano-resonator and the laser at extremely low temperatures. Keeping the laser state and the nano-resonator in Example Four unchanged, the relationship between the nano-resonator and the laser at extremely low temperatures that is known can be used to locate the position of the nano-resonator in the middle of the constant-temperature chamber. The steps are as follows:

[0093] 1) Connect the entire device in Example One, and the position of the nano-resonator is at the relationship between the nano-resonator and the laser at known extremely low temperatures;

[0094] 2) Turn on the laser and adjust the laser using the optical path in Example Two so that its intensity and beam waist position are the same as the known state.

[0095] 4) Turn off the laser;

[0096] 5) Place the constant-temperature chamber in a light-shielded environment and lower the temperature of the constant-temperature chamber to the experimental temperature;

[0097] 6) Use an excitation power supply to vibrate the nano-resonator and use a frequency measurement device to measure its resonance frequency, and confirm that it is the same as the known state;

[0098] 7) Turn on the laser so that the nano-resonator is irradiated by the laser at different angles and intensities, and use a frequency measurement device to measure its resonance frequency. This step needs to be carried out in a dark room.

[0099] 8) Locate the position of the nano-resonator through the known relationship between the nano-resonator and the laser at extremely low temperatures.

[0100] Example Six:

[0101] After completing the measurement of Example 4, analyze the frequency data to obtain the relationship between the nanoscale resonator and the laser at extremely low temperatures. Keeping the laser state and the nanoscale resonator in Example 4 unchanged, the intensity of the laser can be measured using the known relationship between the nanoscale resonator and the laser at extremely low temperatures. The steps are as follows:

[0102] 1) Connect the entire device in Example 1, fix the position of the nanoscale resonator, and know the relationship between the nanoscale resonator and the laser at extremely low temperatures here;

[0103] 2) Turn on the laser, and use the optical path in Example 2 to adjust the laser so that its intensity and beam waist position are the same as the known state.

[0104] 4) Turn off the laser;

[0105] 5) Place the constant temperature chamber in a light-shielded environment and lower the temperature of the constant temperature chamber to the experimental temperature;

[0106] 6) Use the excitation power supply to vibrate the nanoscale resonator and use the frequency measurement device to measure its resonance frequency to confirm that it is the same as the known state;

[0107] 7) Turn on the laser so that the nanoscale resonator is irradiated by the laser, and use the frequency measurement device to measure its resonance frequency. This step needs to be carried out in a dark room.

[0108] 8) Through the known relationship between the nanoscale resonator and the laser at extremely low temperatures, the intensity of the laser can be obtained.

[0109] Example 7:

[0110] Use the devices such as the cryostat, five-axis displacement stage, PCB circuit board, flexible waveguide, coaxial cable, etc. in Example 1 and a vector network analyzer (VNA) to measure the microwave transmission parameters of the flexible waveguide at extremely low temperatures.

[0111] A flexible waveguide adopts a microstrip line structure, such as Figure 3 , with SMA connectors 17 with an impedance of 50 Ω at both ends. The middle microstrip line 18 is a three-layer structure, such as Figure 4 , welded to the connectors at both ends. The middle flexible dielectric layer 20 uses Kapton with a thickness of 0.1 mm, a dielectric constant of 3.4, and the upper and lower conductors use copper with a thickness of 0.035 mm. According to the formula

[0112]

[0113] It is calculated that the width of the conductor strip 19 is 0.21 mm, and the widths of the ground plane 21 and the dielectric layer 20 are designed to be 2.4 mm.

[0114] Another flexible waveguide adopts a coplanar waveguide structure, such asFigure 5 At both ends are SMP connectors 22 with an impedance of 50 Ω. The coplanar waveguide 23 in the middle is a two-layer structure, as Figure 6 , welded to the connectors at both ends. The flexible dielectric layer 24 uses Kapton with a thickness of 0.1 mm and a dielectric constant of 3.4. There are three axially symmetric metal structures on one side of it. The width of the gap between the middle conductor strip 25 and the ground planes 26 and 27 on both sides is set to 0.1 mm. According to the formula

[0115]

[0116] , the calculated width of the conductor strip is 1.9 mm. Tests at room temperature found that a conductor strip width of 1.6 mm had better results, so the width was changed to 1.6 mm.

[0117] Two 22-cm flexible coplanar waveguides are used to connect the PCB circuit board to the microwave port on the inner wall of the cryostat. Then, one 20-cm flexible microstrip line and one 20-cm coaxial cable are used as a control, with both ends connected to the microwave port on the inner wall of the cryostat. To reduce noise, there is a 36-dB attenuator between the microwave port on the inner wall and the microwave port on the outer wall of the cryostat. The cryostat is cooled down to 850 - 870 mK.

[0118] Use a VNA to measure the S-parameters of the three waveguides. The experimental results are as shown in the appendix Figures 7 to 10 . When the impedances of the two ports are matched, S11 represents the reflection coefficient of port 1; S21 represents the transmission coefficient from port 1 to port 2; S22 represents the reflection coefficient of port 2; S12 represents the transmission coefficient from port 2 to port 1. When the reflection coefficient is below -20 dB, that is, when the reflectivity is below 0.1, it is considered that the impedance of the transmission line is well matched. When the transmission coefficient reaches the level of the coaxial cable, it is considered that the transmission ability of the transmission line is good. It is easy to find that S11 and S22 of each waveguide are similar, and S21 and S12 are similar, indicating that the properties of the two ports of each waveguide are the same. The relationship between S11 and S22 of the coplanar waveguide and frequency is similar to that of the coaxial cable, indicating that its reflectivity is the same as that of the coaxial cable and is even slightly better than that of the coaxial cable above 4 GHz; its S21 and S12 are 5 dB smaller than those of the other two waveguides at 7 GHz, indicating that the capacitive effect of the waveguide is obvious at this frequency and needs to be improved. The S11 and S22 of the microstrip line are smaller than those of the coaxial cable below 2 GHz and larger than those of the coaxial cable above 2 GHz, indicating that it is suitable for use at lower frequencies; its S21 and S12 are similar to those of the coaxial cable, indicating that the transmittance is already quite excellent.

[0119] Change the position of the five-axis displacer multiple times and repeat the measurement of the S-parameters of the flexible coplanar waveguide. The experimental results are as shown in the appendix Figure 11 to the appendix Figure 14As shown in the figure. Taking position 1 as the origin, position 2 is 2.5 mm behind, 2.5 mm to the right, and 2 mm above it. Position 3 is 4 mm behind, 5 mm to the right, and 4 mm above it. It can be found that the S parameters of this flexible coplanar waveguide hardly change, indicating that the change in the shape of this flexible waveguide at extremely low temperatures has no impact on the microwave transmission ability.

[0120] To solve the problem of measuring the vibration mode of a nano-resonator at extremely low temperatures, the present invention discloses a device and method for measuring the vibration mode of a nano-resonator at extremely low temperatures. The nano-resonator is installed on a PCB circuit board, fixed on a five-axis displacer inside a cryostat, and communicates with an excitation power source and a frequency test device through a flexible waveguide and a coaxial cable. The excitation power source generates an excitation signal to make the nano-resonator vibrate. The laser generated by the laser is adjusted and incident into the cryostat. The five-axis displacer is moved to make the laser irradiate on the nano-resonator and on a number of points with uniform distribution on different parts of the nano-resonator. By the change in the intensity of the reflected light at each point, the distance between the nano-resonator film and the substrate at that point is obtained, and the vibration mode of the nano-resonator is plotted.

Claims

1. An apparatus for measuring the vibration modes of a nanoresonator at extremely low temperatures, characterized in that, Including: Laser, optical path adjuster, beam splitter, light intensity measuring device, cryostat, five-axis displacement stage, controller, nanoresonator, PCB circuit board, several flexible waveguides, coaxial cable, excitation power supply, frequency measuring device, several wires: Wherein: the cryostat includes a constant temperature cavity, and several microwave transmission interfaces are provided both inside and outside the constant temperature cavity; The five-axis displacement stage, PCB circuit board, and nanoresonator are all placed in the constant temperature cavity; The PCB circuit board is arranged on the five-axis displacement stage; The nanoresonator is placed on the PCB circuit board and is connected to the PCB circuit board through wires for transmitting excitation signals and vibration signals; The PCB circuit board is connected to the microwave transmission interface inside the constant temperature cavity through a flexible waveguide; The microwave transmission interfaces outside the constant temperature cavity are connected to the excitation power supply and the frequency measuring device through coaxial cables respectively; The five-axis displacement stage is connected to the controller outside the constant temperature cavity through wires for transmitting control signals; The laser emitted by the laser passes through the optical path adjuster and the beam splitter and is incident into the constant temperature cavity, and the light reflected from the nanoresonator passes through the beam splitter and is incident into the light intensity measuring device; the excitation power supply, coaxial cable, microwave transmission interface outside the constant temperature cavity, microwave transmission interface inside the constant temperature cavity, flexible waveguide, PCB circuit board, and nanoresonator are connected in sequence to form a closed loop; The nanoresonator, flexible waveguide, microwave transmission interface inside the constant temperature cavity, microwave transmission interface outside the constant temperature cavity, coaxial cable, and frequency measuring device are connected in sequence to form a closed loop; The optical path adjuster includes: adjustable attenuator, single-mode optical fiber, and biconvex lens focusing system; the laser emitted by the laser is attenuated by the attenuator, then mode-selected by the single-mode optical fiber, and finally passes through the biconvex lens focusing system, and the waist of the laser is located near the nanoresonator in the constant temperature cavity; Screw holes are reserved on the five-axis displacement stage, and screw holes are also provided at the corresponding positions on the PCB circuit board, and the PCB circuit board is fixed on the five-axis displacement stage with screws; the five-axis displacement stage drives the PCB circuit board and the nanoresonator to achieve pitching, deflection, and translation.

2. The device for measuring the vibration mode of a nanoresonator at extremely low temperatures according to claim 1, wherein: The flexible waveguide includes a flexible microstrip line and connectors respectively arranged at both ends of the flexible microstrip line; The flexible microstrip line is a three-layer composite structure, which is composed of a metal conductor strip layer, a flexible dielectric layer, and a metal ground layer in sequence; the flexible dielectric layer is located between the metal conductor strip layer and the metal ground layer; the width of the metal ground layer is greater than the width of the metal conductor strip layer; The metal conductor strip layer is connected to the anode of the connector, and the metal ground layer is connected to the cathode of the connector; The width of the metal conductor strip layer and the characteristic impedance of the flexible microstrip line satisfy: where h is the thickness of the flexible dielectric layer, ε eff and w’ are defined as follows: where w is the width of the metal conductor strip layer, t is the thickness of the metal conductor strip layer, and ε r is the relative permittivity of the flexible dielectric layer.

3. The device for measuring the vibration mode of a nanoresonator at extremely low temperatures according to claim 2, characterized in that: The width of the metal ground layer is 5 to 10 times or more of the width of the metal conductor strip layer.

4. The device for measuring the vibration mode of a nano-resonator at extremely low temperatures according to claim 1, wherein: The flexible waveguide includes a coplanar waveguide and connectors respectively arranged at both ends of the coplanar waveguide; The coplanar waveguide is composed of a flexible dielectric layer, a metal conductor strip layer, a first metal ground layer, and a second metal ground layer; The first metal ground layer, the metal conductor strip layer, and the second metal ground layer are laid on the flexible dielectric layer in a coplanar manner; the first metal ground layer and the second metal ground layer are symmetrically distributed on both sides of the metal conductor strip layer; the metal conductor strip layer is connected to the anode of the joint, and both the first metal ground layer and the second metal ground layer are connected to the cathode of the joint; The width of the metal conductor strip layer, the width of the gap between the metal conductor strip layer and the first metal ground layer, and the characteristic impedance of the coplanar waveguide satisfy: where K is the complete elliptic integral of the first kind, ε eff , k, k’, kl and kl’ are defined as follows: where s is the width of the metal conductor strip layer, w is the width of the gap between the metal conductor strip layer and the first metal ground layer, h is the thickness of the flexible dielectric layer, and ε r is the relative permittivity of the flexible dielectric layer.

5. The device for measuring the vibration mode of a nanoresonator at extremely low temperatures according to claim 4, wherein: The widths of the first metal ground layer and the second metal ground layer are greater than or equal to 1 mm.

6. A method for measuring the vibration modes of a nanoresonator in a cryostat, characterized in that, The steps are as follows: 1) Connect the device for measuring the vibration mode of the nano-resonator at extremely low temperatures according to any one of claims 1 to 5; 2) Turn on the laser and adjust the laser intensity and the beam waist position; 3) Place the nano-resonator near the laser beam waist at room temperature; 4) Turn off the laser; 5) Place the constant temperature chamber in a light-shielded environment and lower the temperature of the constant temperature chamber to the experimental temperature; 6) Use the excitation power supply to drive the nano-resonator to vibrate and use the frequency measuring device to measure the resonance frequency of the nano-resonator; 7) Turn on the laser and use the five-axis displacer to move the nano-resonator so that the laser irradiates several points with uniform distribution on different parts of the nano-resonator, and use the light intensity measuring device to measure the reflected light intensity of each point, and draw the vibration mode of the nano-resonator.

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