A device and method for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature

Abstract

This invention discloses an apparatus and method for measuring the vibration of a nanoresonator using optical and radio frequency coupling at low temperatures. Optical and radio frequency coupling refers to exciting the nanoresonator with a radio frequency signal source and then detecting its vibration using optical methods. The nanoresonator is placed on a triaxial piezoelectric displacement stage within a cryostat. The cryostat generates an extremely low temperature experimental environment below 1K, and the triaxial piezoelectric displacement stage is fixed on its cold plate. The detection is achieved using both cryogenic fiber optic and free-space optical methods. The advantages of this invention are: electrical actuation can apply greater driving power than optical actuation to study the dynamic characteristics of the nanoresonator under different operating conditions, avoiding the influence of measurement results; and the use of electrical actuation saves internal space in the cryostat and provides a more stable connection.

Description

Technical Field

[0001] The present invention relates to the cross-technical field of optics and radio frequency, and in particular to a device and method for measuring the vibration of a nano-resonator by optical and radio frequency coupling at low temperature. Background Art

[0002] The structure of the nanoresonator mainly includes a cavity etched on a silicon substrate with a silicon dioxide layer thermally grown on the surface, and a two-dimensional material covered on the cavity by dry transfer. The diameter of the cavity generally ranges from a few microns to tens of microns, and the depth is about a few hundred nanometers. The size of the two-dimensional material must be larger than the diameter of the cavity, and the thickness can be at least a few nanometers. When the external excitation frequency is the same as its natural frequency, resonance will occur, and its vibration is different at different orders of natural frequency. At present, the actuation technology of thin films mainly includes electrical actuation and optical actuation. The principle of electrical actuation is to periodically change the voltage between the film and the substrate to change the electrostatic force on the film. The optical actuation method uses the thermal effect based on laser. In a low-temperature environment, due to the internal space limitation of the equipment and the fact that the microscope objective and the sample displacement stage are in a low-temperature thermostat, the electrical method has the advantages of compact structure and no need for additional optical path adjustment, making it more suitable for application in a low-temperature environment. Summary of the invention

[0003] The object of the present invention is to provide a device and method for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature, so as to solve the problems raised in the above background technology.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a device for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature, comprising a laser and a polarization-maintaining single-mode optical fiber connected to one end thereof, a low-temperature thermostat connected through the polarization-maintaining single-mode optical fiber is provided on one side of the laser, and a neutral density filter, an optical fiber collimator, a half-wave plate, a reflector, a polarization beam splitter cube, a quarter-wave plate, a CCD camera, an LED light source, a photodetector and a spectrum analyzer connected to the polarization-maintaining single-mode optical fiber are provided in sequence between the polarization-maintaining single-mode optical fiber and the low-temperature thermostat The upper end of the cryostat is respectively provided with a piezoelectric displacement stage controller, a DC voltage source and a radio frequency signal generator connected thereto, a cold plate is provided inside the cryostat, a flexible radio frequency waveguide, a three-axis piezoelectric displacement stage and a device to be tested are stacked in sequence at the lower end of the cold plate, the device to be tested is connected to a cryogenic objective lens arranged at its lower end, a window is provided on one side of the lower end of the cryostat, the other end of the cryogenic objective lens away from the device to be tested passes through the window and is connected to the polarization-maintaining single-mode optical fiber, and a folding reflector is provided on one side of the lower end where the cryogenic objective lens is connected to the polarization-maintaining single-mode optical fiber.

[0005] Preferably, the piezoelectric displacement stage controller is connected to the upper end of the cryostat via a 14-pin circular connector vacuum KF63 flange, and the DC voltage source and the RF signal generator are connected to the upper end of the cryostat via a RF SMA connector vacuum ISO100 flange.

[0006] Preferably, a low-temperature coaxial line is provided between the RF SMA connector vacuum ISO100 flange and the cold plate.

[0007] Preferably, the laser emitted by the laser passes through the neutral density filter to attenuate the energy, and then passes through the fiber collimator and the polarization-maintaining single-mode optical fiber to shape and expand the beam. The expanded beam passes through the half-wave plate to change the energy ratio of the horizontal component p wave and the vertical component s wave. After passing through the polarization beam splitter cube, the horizontal component p wave passes through, while the energy of the vertical component s wave is reflected out of the optical path. The emitted p wave passes through the quarter-wave plate placed at 45 degrees between the fast axis direction and the horizontal direction to become circularly polarized light.

[0008] Preferably, the RF SMA connector vacuum ISO100 flange is used to transmit the DC voltage signal generated by the DC voltage source and the RF signal generated by the RF signal generator to the SMA connector on the cold plate through the internal low-temperature RF coaxial line. The device under test is connected to the SMA connector through the flexible RF waveguide to obtain the RF actuation signal required for vibration, and the 14-pin circular connector vacuum KF63 flange is used to connect the piezoelectric displacement stage controller.

[0009] Preferably, the window is a fused quartz window with a diameter of 35 mm and a thickness of 1 mm.

[0010] Preferably, the laser is a laser with a fixed polarization direction, and the three-axis piezoelectric displacement stage is a three-axis piezoelectric displacement stage compatible with high vacuum and low temperature.

[0011] A method for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature, comprising the following steps:

[0012] Step 1: Remove the housing of the cryostat, fix the three-axis translation stage with the sample to be tested upside down under the cold plate of the cryostat, and suspend the cryo objective lens with a low-temperature single-mode polarization-maintaining fiber at the tail above the sample, 4 mm away from the sample. The other end of the low-temperature single-mode polarization-maintaining fiber is connected to the vacuum KF40 flange with FC / APC fiber connector above the cryostat, install the cryostat housing in place, perform vacuum operation, and turn on the helium compressor for refrigeration;

[0013] Step 2: Connect the single-mode polarization-maintaining fiber at the end of the detection light path to the upper end of the vacuum KF40 flange with FC / APC fiber connector above the cryostat, adjust the fiber collimator so that the diameter of the laser output beam after beam expansion through the polarization-maintaining single-mode fiber is 3 mm, and finally couple it into the fiber at the end of the detection light path after passing through all optical components;

[0014] Step 3: After connecting the DC voltage source and the RF signal generator together through the microwave polarizer, connect it to the upper part of the RF SMA connector vacuum ISO100 flange above the cryostat, set the output voltage of the DC voltage source, and the output power, waveform, frequency and other parameters of the RF signal generator, then connect the spectrum analyzer to the photodetector in the detection optical path, and set the center frequency, resolution bandwidth and scanning point parameters;

[0015] Step 4: Based on the installation and debugging results of steps 1 to 3, turn on the laser. After the power is stable, adjust the translation stage so that the chamber covered by the two-dimensional material is in the center of the beam, and adjust the focal length so that the light spot is focused on the sample. Finally, use the Labview program to remotely control the instrument and read the data.

[0016] Beneficial Effects

[0017] The present invention provides an apparatus and method for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature. Compared with optical actuation, electrical actuation can apply a larger driving power to study the dynamic characteristics of the nanoresonator under different working conditions and avoid the influence of laser thermal effect on the measurement results. In addition, in a low-temperature environment, optical actuation requires the installation of an additional low-temperature optical fiber inside the cryostat, and optical elements such as lasers need to be added to the detection optical path, which increases the difficulty of adjustment. In comparison, the use of electrical actuation can save the internal space of the cryostat and the connection is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 This is a schematic structural diagram of Embodiment 2 of the present invention;

[0020] Figure 3 It is a schematic diagram of the nanoresonator structure and testing principle of the present invention.

[0021] Reference numerals

[0022] 1-laser, 2-neutral density filter, 3-fiber collimator, 4-polarization-maintaining single-mode fiber, 5-half wave plate, 6-reflector, 7-polarization beam splitter cube, 8-quarter wave plate, 9-CCD camera, 10-LED light source, 11-photodetector, 12-spectrum analyzer, 13-piezoelectric translation stage controller, 14-DC voltage source, 15-RF signal generator, 16-vacuum KF40 flange with FC / APC fiber connector, 17-14-pin circular connector vacuum KF63 flange, 18-RF SMA connector vacuum ISO100 flange, 19-low-temperature single-mode polarization-maintaining fiber, 20-low-temperature coaxial line, 21-cold plate, 22-flexible RF waveguide, 23-three-axis piezoelectric translation stage, 24-device under test and PCB, 25-low-temperature objective lens, 26-folding reflector, 27-window, 28-low-temperature thermostat. DETAILED DESCRIPTION

[0023] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0024] Example 1

[0025] A device for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature, comprising a laser 1 and a polarization-maintaining single-mode optical fiber 4 connected to one end thereof, a low-temperature thermostat 28 connected via the polarization-maintaining single-mode optical fiber 4 is provided on one side of the laser 1, a neutral density filter 2, an optical fiber collimator 3, a half-wave plate 5, a reflector 6, a polarization beam splitter cube 7, a quarter-wave plate 8, a CCD camera 9, an LED light source 10, a photodetector 11 and a spectrum analyzer 12 are provided in sequence between the polarization-maintaining single-mode optical fiber 4 and the low-temperature thermostat 28, and a polarization beam splitter cube 7, a quarter-wave plate 8, a CCD camera 9, an LED light source 10, a photodetector 11 and a spectrum analyzer 12 are provided on the upper end of the low-temperature thermostat 28. A piezoelectric displacement stage controller 13, a DC voltage source 14 and a radio frequency signal generator 15 are connected thereto. A cold plate 21 is arranged in a low-temperature thermostat 28. A flexible radio frequency waveguide 22, a three-axis piezoelectric displacement stage 23 and a device to be tested 24 are stacked in sequence at the lower end of the cold plate 21. The device to be tested 24 is connected to a low-temperature objective lens 25 arranged at its lower end. A window 27 is arranged at one side of the lower end of the low-temperature thermostat 28. The other end of the low-temperature objective lens 25 away from the device to be tested 24 passes through the window 27 and is connected to a polarization-maintaining single-mode optical fiber 4. A folding reflector 26 is arranged at one side of the lower end where the low-temperature objective lens 25 is connected to the polarization-maintaining single-mode optical fiber 4.

[0026] Preferably, the piezoelectric displacement stage controller 13 is connected to the upper end of the cryostat 28 via a 14-pin circular connector vacuum KF63 flange 17 , and the DC voltage source 14 and the RF signal generator 15 are connected to the upper end of the cryostat 28 via a RF SMA connector vacuum ISO100 flange 18 .

[0027] Preferably, a low-temperature coaxial line 20 is provided between the RF SMA connector vacuum ISO100 flange 18 and the cold plate 21 .

[0028] Preferably, the laser 1 emits a laser which passes through a neutral density filter 2 for energy attenuation and then passes through a fiber collimator 3 and a polarization-maintaining single-mode fiber 4 for shaping and expanding. The expanded light beam passes through a half-wave plate 5 to change the energy ratio of the horizontal component p-wave and the vertical component s-wave. After passing through a polarization beam splitter cube 7, the horizontal component p-wave is allowed to pass through, while the energy of the vertical component s-wave is reflected out of the optical path. The emitted p-wave passes through a quarter-wave plate 8 which is placed at 45 degrees between the fast axis direction and the horizontal direction and becomes circularly polarized light.

[0029] Preferably, the RF SMA connector vacuum ISO100 flange 18 is used to transmit the DC voltage signal generated by the DC voltage source 14 and the RF signal generated by the RF signal generator 15 to the SMA connector on the cold plate 21 through the internal low-temperature RF coaxial line 20. The device under test 24 is connected to the SMA connector through the flexible RF waveguide 22 to obtain the RF actuation signal required for vibration. The 14-pin circular connector vacuum KF63 flange 17 is used to connect the piezoelectric displacement stage controller 13.

[0030] Preferably, the window 27 is a fused quartz window with a diameter of 35 mm and a thickness of 1 mm.

[0031] Preferably, the laser 1 is a laser with a fixed polarization direction, and the three-axis piezoelectric displacement stage 23 is a three-axis piezoelectric displacement stage compatible with high vacuum and low temperature.

[0032] A method for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature, using a window to introduce a laser beam, comprises the following steps:

[0033] Step 1: Remove the outer shell of the cryostat, fix the three-axis translation stage with the sample to be tested upside down under the cold plate of the cryostat, and suspend the cryo objective lens with a low-temperature single-mode polarization-maintaining fiber at the tail above the sample, 4mm away from the sample. Connect the other end of the low-temperature single-mode polarization-maintaining fiber to the vacuum KF40 flange with FC / APC fiber connector on the top of the cryostat, install the cryostat outer shell in place, perform vacuum operation, and turn on the helium compressor for cooling;

[0034] Step 2: Connect the single-mode polarization-maintaining fiber at the end of the detection light path to the upper end of the vacuum KF40 flange with FC / APC fiber connector above the cryostat, adjust the fiber collimator so that the diameter of the laser output beam after beam expansion through the polarization-maintaining single-mode fiber is 3 mm, and finally couple it into the fiber at the end of the detection light path after passing through all optical components;

[0035] Step 3: After connecting the DC voltage source and the RF signal generator together through the microwave polarizer, connect it to the upper part of the RF SMA connector vacuum ISO100 flange above the cryostat, set the output voltage of the DC voltage source, and the output power, waveform, frequency and other parameters of the RF signal generator, then connect the spectrum analyzer to the photodetector in the detection optical path, and set the center frequency, resolution bandwidth and scanning point parameters;

[0036] Step 4: Based on the installation and debugging results of steps 1 to 3, turn on the laser. After the power is stable, adjust the translation stage so that the chamber covered by the two-dimensional material is in the center of the beam, and adjust the focal length so that the light spot is focused on the sample. Finally, use the Labview program to remotely control the instrument and read the data.

[0037] The present invention provides a device for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature. The nanoresonator is actuated by radio frequency signals, based on the structure of the nanoresonator similar to that of a transistor. A DC voltage is applied between the two-dimensional film and the base. At this time, the electrostatic force between the film and the gate can be expressed as:

[0038]

[0039] Where C′ g =dC i Due to the electrostatic force, the film will be biased towards the base, and finally the film will be in a balanced position. At the same time, an AC voltage with a frequency in the RF band is applied to the base. At this time, the electrostatic force between the film base can be expressed as:

[0040]

[0041] At this time, the film will be driven by a periodic force and vibrate in the vertical direction. The vibration detection adopts an optical method, which is based on the principle of laser interference of Fabry-Perot cavity. Figure 3 The nanoresonator structure includes a two-dimensional material film layer, an air layer, a silicon dioxide layer, and a bottom silicon substrate layer. The complex amplitude of the upper surface electric field at each interface is , and the complex amplitude of the lower surface electric field is . For each interface, the total reflection coefficient is expressed as Γ i =E i- , using the transmission matrix, we can get the relationship between the incident electric field and the transmitted electric field of the entire device:

[0042]

[0043]

[0044]

[0045] where t i , r i is the Fresnel reflection and transmission coefficient of the surface, d i is the thickness of each layer, k i =2π / λ*n i , n i is the refractive index of each layer of the medium; the reflectivity of the entire device is R = [M(2, 1) / M(1, 1)] 2 ,When the distance between the film and the substrate changes periodically, the intensity of the reflected light will also be modulated periodically.

[0046] Example 2

[0047] A method for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature, using an optical fiber to introduce a laser beam, comprises the following steps:

[0048] Step 1: Remove the outer shell of the cryostat, stack the piezoelectric displacement stages, from bottom to top, for the Z axis, Y axis, and X axis, and fix them with titanium alloy M2.5 hexagon socket bolts, and fix the PCB with the sample to be tested in the center to the upper surface of the piezoelectric displacement stage with M1.6 slotted bolts. After the piezoelectric displacement stage is assembled, fix it upside down on the cold plate of the cryostat, and connect the twisted pair wire used for the side control of the piezoelectric displacement stage to the D-Sub connector on the cold plate. Then connect one end of the RF flexible waveguide to the SMA RF connector on the PCB, and cold-connect the other end to the pre-installed SMA connector on the cold plate. These connectors have been connected to the vacuum ISO100 flange with RF SMA connector on the top when the equipment is installed;

[0049] Step 2: Suspend the low-temperature objective lens with a low-temperature single-mode polarization-maintaining fiber at the tail end above the sample, about 4 mm away from the surface of the sample to be tested. Fix the other end of the low-temperature single-mode polarization-maintaining fiber to the vacuum KF40 flange with FC / APC fiber connector above the cryostat. Finally, install the cryostat shell in place, perform vacuum operation, and turn on the helium compressor for cooling.

[0050] Step 3: Connect the single-mode polarization-maintaining fiber at the end of the detection optical path to the outside of the vacuum KF40 flange with FC / APC fiber connector above the cryostat, turn on the laser, and after the power is stable, adjust the fiber collimator so that the diameter of the laser output beam after beam expansion through the polarization-maintaining single-mode fiber is 3 mm. After passing through all optical components, adjust the fiber collimator at the end of the optical path so that the beam is coupled into the single-mode fiber, and use the photodetector in the optical path to connect to the spectrum analyzer to maximize the coupling efficiency;

[0051] Step 4: After connecting the DC voltage source and the RF signal generator together through the microwave paranoid, connect it to the RF SMA connector vacuum ISO100 flange above the cryostat, set the output voltage of the DC voltage source, and the output power, waveform, and frequency parameters of the RF signal generator, and then connect the spectrum analyzer to the photodetector in the detection optical path, and set the center frequency, resolution bandwidth, scanning point and other parameters;

[0052] Step 5: Based on the installation and debugging results of steps 1 to 4, use the Labview program to remotely control the instrument and read the data.

[0053] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the invention content within the protection scope of the present invention.

Claims

1. A device for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature, comprising a laser (1) and a polarization-maintaining single-mode optical fiber (4) connected to one end thereof, characterized in that: A low temperature thermostat (28) connected to the polarization-maintaining single-mode optical fiber (4) is provided on one side of the laser (1); a neutral density filter (2), an optical fiber collimator (3), a half wave plate (5), a reflector (6), a polarization beam splitter cube (7), a quarter wave plate (8), a CCD camera (9), an LED light source (10), a photodetector (11) and a spectrum analyzer (12) connected to the polarization-maintaining single-mode optical fiber (4) are provided in sequence between the polarization-maintaining single-mode optical fiber (4) and the low temperature thermostat (28); a piezoelectric displacement stage controller (13), a DC voltage source (14) and a radiation source (12) connected to the low temperature thermostat (28) are provided at the upper end thereof. A frequency signal generator (15), a cold plate (21) is provided in the low temperature thermostat (28), a flexible radio frequency waveguide (22), a three-axis piezoelectric displacement stage (23) and a device to be tested (24) are stacked in sequence at the lower end of the cold plate (21), the device to be tested (24) is connected to a low temperature objective lens (25) arranged at the lower end thereof, a window (27) is provided at one side of the lower end of the low temperature thermostat (28), the other end of the low temperature objective lens (25) away from the device to be tested (24) passes through the window (27) and is connected to the polarization-maintaining single-mode optical fiber (4), and a folding reflector (26) is provided at one side of the lower end where the low temperature objective lens (25) is connected to the polarization-maintaining single-mode optical fiber (4); The piezoelectric displacement stage controller (13) is connected to the upper end of the cryostat (28) via a 14-pin circular connector vacuum KF63 flange (17), and the DC voltage source (14) and the radio frequency signal generator (15) are connected to the upper end of the cryostat (28) via a radio frequency SMA connector vacuum ISO100 flange (18); A low-temperature coaxial line (20) is provided between the radio frequency SMA connector vacuum ISO100 flange (18) and the cold plate (21); The laser (1) passes the energy of the emitted laser light through the neutral density filter (2) to attenuate the energy, and then passes through the optical fiber collimator (3) and the polarization-maintaining single-mode optical fiber (4) to shape and expand the beam. The expanded beam passes through the half-wave plate (5) to change the energy ratio of the horizontal component p wave and the vertical component s wave. After passing through the polarization beam splitter cube (7), the horizontal component p wave passes through, while the energy of the vertical component s wave is reflected out of the optical path. The emitted p wave passes through the quarter-wave plate (8) whose fast axis direction is placed at 45 degrees to the horizontal direction to become circularly polarized light. The radio frequency SMA connector vacuum ISO100 flange (18) is used to transmit the DC voltage signal generated by the DC voltage source (14) and the radio frequency signal generated by the radio frequency signal generator (15) to the SMA connector on the cold plate (21) through the internal low-temperature coaxial line (20); the device under test (24) is connected to the SMA connector through the flexible radio frequency waveguide (22) to obtain the radio frequency actuation signal required for vibration; and the 14-pin circular connector vacuum KF63 flange (17) is used to connect the piezoelectric displacement stage controller (13).

2. The device for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature according to claim 1, characterized in that: The window (27) is a fused quartz window with a diameter of 35 mm and a thickness of 1 mm.

3. The device for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature according to claim 1, characterized in that: The laser (1) is a laser with a fixed polarization direction, and the three-axis piezoelectric displacement stage (23) is a three-axis piezoelectric displacement stage compatible with high vacuum and low temperature.

4. A method for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature, characterized in that: The measurement is performed using the apparatus for measuring the vibration of a nanoresonator by optical and radio frequency coupling at low temperature as claimed in claim 1, the steps being as follows: Step 1: Remove the housing of the cryostat, fix the three-axis translation stage with the sample to be tested upside down under the cold plate of the cryostat, and suspend the cryo objective lens with a low-temperature single-mode polarization-maintaining fiber at the tail above the sample, 4 mm away from the sample. The other end of the low-temperature single-mode polarization-maintaining fiber is connected to the vacuum KF40 flange with FC / APC fiber connector above the cryostat, install the cryostat housing in place, perform vacuum operation, and turn on the helium compressor for refrigeration; Step 2: Connect the single-mode polarization-maintaining fiber at the end of the detection light path to the upper end of the vacuum KF40 flange with FC / APC fiber connector above the cryostat, adjust the fiber collimator so that the diameter of the laser output beam after beam expansion through the polarization-maintaining single-mode fiber is 3 mm, and finally couple it into the fiber at the end of the detection light path after passing through all optical components; Step 3: After connecting the DC voltage source and the RF signal generator together through the microwave polarizer, connect it to the upper part of the RF SMA connector vacuum ISO100 flange above the cryostat, set the output voltage of the DC voltage source, and the output power, waveform, frequency and other parameters of the RF signal generator, then connect the spectrum analyzer to the photodetector in the detection optical path, and set the center frequency, resolution bandwidth and scanning point parameters; Step 4: Based on the installation and debugging results of steps 1 to 3, turn on the laser. After the power is stable, adjust the translation stage so that the chamber covered by the two-dimensional material is in the center of the beam, and adjust the focal length so that the light spot is focused on the sample. Finally, use the Labview program to remotely control the instrument and read the data.

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