A device and method for detecting the rotation speed of an object using terahertz waves

Abstract

The invention provides a device and method for detecting the rotation speed of an object by using terahertz waves. The device and method include: a terahertz source, a terahertz vortex beam generator and a signal receiving end. The terahertz source includes a vector network analyzer, a frequency doubling module and a metal waveguide. The vector network analyzer transmits a microwave signal and then modulates the frequency of the signal through the frequency doubling module. The metal waveguide outputs the frequency-modulated terahertz wave. The terahertz vortex beam generator is used to generate a vortex beam in the terahertz band and includes a conical waveguide and a micro-ring waveguide. The micro-ring waveguide includes a micro-ring resonant cavity and a grating array structure. The terahertz wave in the conical waveguide enters the micro-ring resonant cavity through near-field coupling. The micro-ring waveguide excites a vortex beam in the terahertz band. The grating array structure is etched on the side wall of the micro-ring resonant cavity so that the vortex beam is vertically scattered on the toroidal surface of the rotating object to be detected. After the rotating object receives the beam, the scattered echo signal is fed back to the vector network analyzer through the signal receiving end to analyze the echo signal and calculate the rotation speed of the rotating object.

Description

Technical Field

[0001] The present invention belongs to the field of terahertz wave detection, relates to a vortex light phase detection technology, and specifically provides a device and a method for detecting the rotation speed of an object by using terahertz waves. Background Art

[0002] In recent years, with the deepening of understanding of terahertz waves, it has been found that terahertz waves have good penetration into many dielectric materials and non-polar liquids, and have no strong ionization and are safe for the human body. Therefore, terahertz has a very good prospect in the field of detection. It is currently widely used in non-destructive testing, terahertz CT, radar detection, spectroscopy and imaging technology, and information science. However, there is no device or method for using its vortex phase to detect the rotation speed of rotating objects, especially in the terahertz high-frequency band, which is difficult to achieve.

[0003] According to the Doppler effect, when light shines on a moving object, the frequency of the light reflected back from the object will change. If the object moves away from the light source, the frequency of the reflected light will decrease, which we call redshift; if the object moves closer to the light source, the frequency of the reflected light will increase, which we call blueshift. However, this method is difficult to directly detect rotating objects. At this time, we can introduce a vortex beam with orbital angular momentum. Because the Poynting vector of the vortex beam has a component perpendicular to the propagation direction, the Doppler effect still exists in the beam cross section. When the rotational Doppler frequency shift occurs, according to the formula:

[0004]

[0005] Where Δf is the Doppler frequency shift, l is the topological charge of the vortex beam, and Ω is the rotation speed of the rotor.

[0006] Normally, the value of Δf is too small to be measured directly. We construct the relationship between frequency and phase, and we have

[0007]

[0008] Where f0 is the frequency of the incident light, is the phase difference. As the measurement time t increases, the phase difference will increase with the increase of the sampling period n, and there is

[0009] n=tf0

[0010]

[0011] Among them, ΔΦ is the signal phase difference measured after experimental amplification, and t is the measurement time.

[0012] It can be deduced

[0013] ΔΦ=tl2 Ω

[0014] According to the above formula, we can indirectly measure the rotation speed of the object by measuring the phase difference of the signal.

[0015] Currently, conventional devices for detecting the rotation speed of rotating objects have disadvantages such as large and complex measurement structure, low accuracy and high cost. There is no related device or method for directly detecting the rotation speed of an object using the vortex phase of terahertz waves. Summary of the invention

[0016] The present invention is made to solve the above problems, and its purpose is to provide a device and method for detecting the rotation speed of an object using terahertz waves. To this end, the present invention provides the following technical solutions:

[0017] The present invention provides a device for detecting the rotation speed of an object using terahertz waves, which is characterized by comprising: a terahertz source, a terahertz vortex beam generator and a signal receiving end, wherein the terahertz source comprises a vector network analyzer, a first frequency doubling module and a metal waveguide, the vector network analyzer is at least used to transmit microwave signals, the first frequency doubling module is used to adjust the frequency of microwaves to the terahertz operating frequency required by users, the metal waveguide is connected to the first frequency doubling module, and serves as a signal output end, and is used to output frequency-modulated terahertz waves, the terahertz vortex beam generator is used to generate a vortex beam in the terahertz band, and comprises a conical waveguide, a micro-ring waveguide and a substrate, one end of the conical waveguide is plugged with the metal waveguide, and is used to allow the terahertz wave to enter the conical waveguide, the micro-ring waveguide is connected to the conical waveguide, and comprises a micro-ring resonant cavity and The grating array structure is used for the terahertz wave in the conical waveguide to enter the micro-ring resonant cavity through near-field coupling. The terahertz wave in the micro-ring resonant cavity produces a resonance enhancement effect with the terahertz wave in the conical waveguide under the resonance condition. The terahertz wave that meets the resonance condition is confined to the micro-ring waveguide for transmission. The micro-ring waveguide excites a vortex light beam with orbital angular momentum in the terahertz band. The grating array structure is etched on the side wall or the top of the micro-ring resonant cavity to scatter the vortex light beam in a direction perpendicular to the ring surface, so that the vortex light beam is vertically irradiated on the rotating object to be detected. The rotating object to be detected receives the vortex light beam and then scatters the echo signal. The signal receiving end is used to receive the echo signal and feed it back to the vector network analyzer. The vector network analyzer is also used to analyze the echo signal to calculate the rotation speed of the rotating object to be detected.

[0018] In the device for detecting the rotation speed of an object using terahertz waves provided by the present invention, it can also have the following characteristics: wherein, the signal receiving end has a horn antenna and a second frequency doubling module, the horn antenna is used to receive and feed back the echo signal, the second frequency doubling module is used to multiply the echo signal to a frequency that can be received by a vector network analyzer, and the vector network analyzer calculates the rotation speed of the rotating object to be detected by analyzing the phase difference of the echo signal.

[0019] The device for detecting the rotation speed of an object using terahertz waves provided by the present invention may also have the following characteristics: wherein, in the terahertz vortex beam generator, the resonance condition is n eff L = m λ m , n eff is the effective refractive index of the light mode in the resonant ring, L is the circumference of the resonant ring, m is the resonance order, λ m is the resonant wavelength.

[0020] In the device for detecting the rotation speed of an object using terahertz waves provided by the present invention, the device may also have the following features: wherein the microring resonant cavity is in a circular shape, and its size and thickness are determined by the operating frequency; the grating array structure includes a plurality of gratings, and the plurality of gratings are evenly distributed on the inner side surface of the microring resonant cavity, and the plurality of gratings are distributed in a ring shape with the central axis of the microring resonant cavity as the axis; the length, width and number of the gratings are related to the operating frequency; when the operating frequency is 180 GHz, the radius of the microring resonant cavity is 6900 microns and the thickness is 500 microns; the length and width of a single grating are 300 microns and 60 microns, and the number of gratings is 72.

[0021] The device for detecting the rotation speed of an object using terahertz waves provided by the present invention may also have the following characteristics: wherein the spacing between the tapered waveguide and the micro-ring waveguide should enable the two waveguides to have a coupling effect, which is usually ≤200 microns.

[0022] In the device for detecting the rotation speed of an object using terahertz waves provided by the present invention, it can also have the following characteristics: wherein, the substrate is used to connect the conical waveguide and the microring waveguide and play a supporting role, so that the length direction of the conical waveguide is parallel to the longitudinal section of the microring resonant cavity, the thickness of the substrate is 130 microns, and the thickness of the conical waveguide is 500 microns.

[0023] The device for detecting the rotation speed of an object using terahertz waves provided by the present invention may also have the following feature: wherein the conical waveguide, the micro-ring waveguide and the substrate are all made of high-resistance silicon material.

[0024] The present invention provides a method for detecting the rotation speed of an object using terahertz waves, which is performed using any of the above-mentioned devices for detecting the rotation speed of an object using terahertz waves, and is characterized in that the method comprises the following steps: step 1, using a vector network analyzer to emit a microwave signal, the output microwave passes through a first frequency doubling module, and the first frequency doubling module adjusts the microwave frequency to the terahertz operating frequency required by the user, and then the terahertz wave enters the tapered waveguide through a metal waveguide; step 2, according to a resonance condition n eff L = m λ m, when L is an integer multiple of m, the terahertz wave in the conical waveguide and the terahertz wave in the microring waveguide produce a resonance enhancement effect, the terahertz wave of a specific frequency is coupled into the microring waveguide and is confined to the microring waveguide for transmission, and the microring waveguide excites a vortex beam with orbital angular momentum; step 3, placing the rotating object to be detected right in front of the terahertz vortex beam generator, receiving the vortex beam, the echo signal scattered from the rotating object to be detected is received by the horn antenna at the signal receiving end, the horn antenna receives the echo signal through the second frequency doubling module and feeds it back to the vector network analyzer, the vector network analyzer analyzes the phase difference of the echo signal, and thus calculates the rotation speed of the rotating object to be detected.

[0025] The method for detecting the rotation speed of an object using terahertz waves provided by the present invention may also have the following characteristics: wherein, in step 1, the operating frequency is calculated according to the formula n eff L = m λ m , by adjusting the radius of the micro-ring waveguide and the number of gratings, when the circumference L of the resonant ring increases, the resonant wavelength λ m As it increases, the operating wavelength increases, so the operating frequency decreases.

[0026] The method for detecting the rotation speed of an object using terahertz waves provided by the present invention may also have the following features: wherein, in step 2, adjusting the size of the micro-ring waveguide can regulate the distribution of the evanescent field outside the waveguide, adjusting the aspect ratio of the micro-ring waveguide can selectively excite a mode of a specific frequency for regulating the orbital angular momentum, and adjusting the size of the grating can cause the micro-ring waveguide to excite a vortex beam with a specific orbital angular momentum, so that the vortex beam is detected directly in front of the micro-ring waveguide.

[0027] Functions and Effects of the Invention

[0028] The present invention provides a device for detecting the rotation speed of an object using terahertz waves, including: a terahertz source, a terahertz vortex beam generator and a signal receiving end. The terahertz source includes a vector network analyzer, a first frequency doubling module and a metal waveguide. The vector network analyzer is at least used to transmit microwave signals. The first frequency doubling module is used to adjust the frequency of microwaves to the terahertz operating frequency required by the user. The metal waveguide is connected to the first frequency doubling module as a signal output end, and is used to output the frequency-modulated terahertz wave. The terahertz vortex beam generator is used to generate a vortex beam in the terahertz band, and includes a conical waveguide, a microring waveguide and a substrate. One end of the conical waveguide is plugged into the metal waveguide to allow the terahertz wave to enter the conical waveguide. The micro-ring waveguide is connected to the conical waveguide, including a micro-ring resonant cavity and a grating array structure. The terahertz wave in the conical waveguide enters the micro-ring resonant cavity through near-field coupling. The terahertz wave in the micro-ring resonant cavity can produce a resonant enhancement effect with the terahertz wave in the conical waveguide under the resonant condition, and the terahertz wave that meets the resonant condition is confined to the micro-ring waveguide for transmission. The micro-ring waveguide can excite a vortex beam with orbital angular momentum in the terahertz band. The grating array structure is etched on the side wall or top of the micro-ring resonant cavity, which can scatter the vortex beam in a direction perpendicular to the ring surface, so that the vortex beam is vertically irradiated on the rotating object to be detected. The rotating object to be detected receives the vortex beam and scatters the echo signal. The signal receiving end is used to receive the echo signal and feed it back to the vector network analyzer. Therefore, the vector network analyzer can calculate the rotation speed of the rotating object to be detected by analyzing the phase difference of the echo signal, and the measurement result is accurate and reliable.

[0029] The present invention provides a method for detecting the rotation speed of an object using terahertz waves, comprising the following steps: step 1, using a vector network analyzer to emit microwaves, the output microwaves pass through a first frequency doubling module, the first frequency doubling module adjusts the frequency of the electromagnetic wave to the terahertz operating frequency required by the user, and then the terahertz wave enters the tapered waveguide through a metal waveguide; step 2, according to the resonance condition n eff L = m λ m, when L is an integer multiple of m, the terahertz wave in the conical waveguide and the terahertz wave in the microring waveguide produce a resonance enhancement effect, the terahertz wave of a specific frequency is coupled into the microring waveguide and is confined to the microring waveguide for transmission, and the microring waveguide excites a vortex beam with orbital angular momentum; step 3, placing the rotating object to be detected right in front of the terahertz vortex beam generator, receiving the vortex beam, the echo signal scattered from the rotating object to be detected is received by the horn antenna at the signal receiving end, the horn antenna receives the echo signal through the second frequency doubling module and feeds it back to the vector network analyzer, the vector network analyzer analyzes the phase difference of the echo signal, and thus calculates the rotation speed of the rotating object to be detected. The method for detecting the rotation speed of an object using terahertz waves provided by the present invention can realize direct detection of the rotation speed of an object by using the phase of light. By using high-resistance silicon material to make a conical waveguide, a microring waveguide and a substrate and debugging the device structure, the speed measuring device is successfully used in the terahertz band. The method is creative, the detection process is simple to operate, the measurement result is accurate and reliable, and the problems of large and complex measurement structure, low precision and high cost of conventional devices for detecting the rotation speed of rotating objects are avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of a module of a device for detecting the rotation speed of an object using terahertz waves in an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of the structure and optical path of a device for detecting the rotation speed of an object using terahertz waves in an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the structure of the terahertz vortex beam generator in an embodiment of the present invention Figure 1 ;

[0033] Figure 4 Schematic diagram of the structure of the terahertz vortex beam generator in an embodiment of the present invention Figure 2 . DETAILED DESCRIPTION

[0034] In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments and the accompanying drawings specifically illustrate the device and method for detecting the rotation speed of an object using terahertz waves.

[0035] <Example>

[0036] Figure 1 Schematic diagram of a module of a device for detecting the rotation speed of an object using terahertz waves in an embodiment of the present invention.

[0037] like Figure 1As shown, this embodiment provides a device 100 for detecting the rotation speed of an object using terahertz waves, comprising: a terahertz source 10, a terahertz vortex beam generator 20, and a signal receiving end 40. The rotating object to be detected is a disk rotor 30 placed directly in front of the terahertz vortex beam generator 20.

[0038] Figure 2 It is a schematic diagram of the structure and optical path of a device for detecting the rotation speed of an object using terahertz waves in an embodiment of the present invention.

[0039] like Figure 2 As shown, the terahertz source 10 includes a vector network analyzer 11, a first frequency doubling module 12 and a metal waveguide 13. The vector network analyzer 11 is at least used to transmit microwaves. The first frequency doubling module 12 is used to adjust the frequency of the microwaves to the terahertz operating frequency required by the user. The metal waveguide 13 is connected to the first frequency doubling module 12 as a signal output terminal, and is used to output the frequency-modulated terahertz wave.

[0040] Figure 3 Schematic diagram of the structure of the terahertz vortex beam generator in an embodiment of the present invention Figure 1 , Figure 4 Schematic diagram of the structure of the terahertz vortex beam generator in an embodiment of the present invention Figure 2 .

[0041] like Figures 3-4 As shown, the terahertz vortex beam generator 20 includes a tapered waveguide 21, a micro-ring waveguide 22 and a substrate 23, all of which are made of high-resistance silicon material. The terahertz vortex beam generator 20 is used to generate a vortex beam in the terahertz band.

[0042] One end of the conical waveguide 21 is plugged into the metal waveguide 13. The terahertz wave is transmitted into the conical waveguide 21 via the metal waveguide 13. The microring waveguide 22 is connected to the conical waveguide 21, and the spacing between the conical waveguide 21 and the microring waveguide 22 should allow the conical waveguide 21 and the microring waveguide 22 to have a coupling effect, which is usually ≤200 microns. The substrate 23 is used to connect the conical waveguide 21 and the microring waveguide 22, and plays a supporting role, so that the length direction of the conical waveguide 21 is parallel to the longitudinal section of the microring resonant cavity 22, and the thickness of the substrate 23 is sufficient to play a supporting role. In this embodiment, the thickness of the substrate 23 is 130 microns, and the thickness of the conical waveguide 21 is 500 microns.

[0043] The micro-ring waveguide 22 includes a micro-ring resonant cavity 221 and a grating array structure 222. The micro-ring resonant cavity 221 is annular, and its size and thickness are determined by the operating frequency. The micro-ring resonant cavity 221 is used to generate near-field coupling with the terahertz wave in the conical waveguide 21. The terahertz wave entering the micro-ring resonant cavity 221 through the near-field coupling satisfies the resonance condition n. eff L = m λ m (neff is the effective refractive index of the light mode in the resonant ring, L is the circumference of the resonant ring, m is the resonance order, λ m When the wavelength is the resonant wavelength, a resonance enhancement effect is generated with the terahertz wave in the conical waveguide 21, and the terahertz wave that meets the resonance condition is confined to be transmitted in the micro-ring waveguide 22. The micro-ring waveguide 22 can excite a vortex beam with orbital angular momentum in the terahertz band.

[0044] The grating array structure 222 is etched on the side wall of the micro-ring resonant cavity 22, and is used to scatter the vortex light beam in a direction perpendicular to the ring surface, so that the vortex light beam is vertically irradiated on the rotating object 30 to be detected, and the rotating object 30 to be detected receives the vortex light beam and scatters the echo signal. The grating array structure 222 includes a plurality of gratings 2221, and the plurality of gratings 2221 are evenly distributed on the inner side of the micro-ring resonant cavity 22, and the plurality of gratings 2221 are distributed in a ring shape with the central axis of the micro-ring resonant cavity 22 as the axis. The length, width and number of the gratings 2221 are related to the operating frequency. In this embodiment, the operating frequency is 180GHz, at which time the radius of the micro-ring resonant cavity is 6900 microns and the thickness is 500 microns, the length of a single grating is 300 microns, the width is 60 microns, and the number of gratings is 72.

[0045] The signal receiving end 40 has a horn antenna 41 and a second frequency doubling module 42. The horn antenna 41 is used to receive the echo signal through the second frequency doubling module 42 and feed it back to the vector network analyzer 11. The vector network analyzer 11 is also used to analyze the phase difference of the echo signal to calculate the rotation speed of the rotating object 30 to be detected.

[0046] like Figures 1 to 4 As shown, the present invention provides a method for detecting the rotation speed of an object using terahertz waves, comprising the following steps:

[0047] Step 1: Use the vector network analyzer 11 to emit microwaves. The output microwaves pass through the first frequency doubling module 12. The first frequency doubling module 12 adjusts the frequency of the electromagnetic wave to the terahertz operating frequency required by the user (the frequency adjustment method is, according to the formula n eff L = m λ m The frequency is adjusted by adjusting the radius of the micro-ring waveguide 22 and the number of gratings 2221. When the circumference L of the resonant ring, that is, the radius of the micro-ring waveguide 22, increases, the resonant wavelength λ m The terahertz wave enters the tapered waveguide 21 through the metal waveguide 13;

[0048] Step 2, according to the resonance condition n eff L = m λ m, when L is an integer multiple of m, the terahertz wave in the tapered waveguide 21 and the terahertz wave in the microring waveguide 22 produce a resonance enhancement effect, the terahertz wave of a specific frequency is coupled into the microring waveguide 22 and is confined to be transmitted in the microring waveguide 22, the microring waveguide 22 excites a vortex beam with orbital angular momentum, adjusting the size of the microring waveguide 22 can regulate the evanescent field distribution outside the waveguide, adjusting the aspect ratio of the microring waveguide 22 can selectively excite a mode of a specific frequency for regulating the orbital angular momentum, and adjusting the size of the grating can enable the microring waveguide 22 to excite a vortex beam with a specific orbital angular momentum, so that the vortex beam is detected right in front of the microring waveguide 22;

[0049] Step 3, place the rotating object 30 to be detected directly in front of the terahertz vortex beam generator, receive the vortex beam, and the echo signal scattered from the rotating object 30 to be detected is received by the horn antenna 41 at the signal receiving end. The horn antenna 41 receives the echo signal through the second frequency doubling module 42 and feeds it back to the vector network analyzer 11. The vector network analyzer 11 analyzes the phase difference of the echo signal, thereby calculating the rotational speed of the rotating object 30 to be detected.

[0050] Functions and Effects of the Embodiments

[0051] According to the device and method for detecting the rotation speed of an object using terahertz waves involved in this embodiment, the device for detecting the rotation speed of an object using terahertz waves includes: a terahertz source, a terahertz vortex beam generator, and a signal receiving end. The rotating object to be detected is placed directly in front of the terahertz vortex beam generator.

[0052] The terahertz source includes a vector network analyzer, a first frequency doubling module and a metal waveguide. The vector network analyzer is used to transmit microwaves at least. The first frequency doubling module is used to adjust the frequency of the microwaves to the terahertz operating frequency required by the user. The metal waveguide is connected to the first frequency doubling module as a signal output terminal for outputting frequency-modulated terahertz waves.

[0053] The terahertz vortex beam generator includes a conical waveguide, a microring waveguide and a substrate, all of which are made of high-resistance silicon material. The terahertz vortex beam generator is used to generate a vortex beam in the terahertz band. One end of the conical waveguide is plugged into a metal waveguide. The terahertz wave is transmitted into the conical waveguide via the metal waveguide. The microring waveguide is connected to the conical waveguide. In this embodiment, the spacing between the conical waveguide and the microring waveguide is ≤200 microns. The substrate is used to connect the conical waveguide and the microring waveguide, and plays a supporting role so that the length direction of the conical waveguide is parallel to the longitudinal section of the microring resonant cavity. The thickness of the substrate is sufficient to play a supporting role. In this embodiment, the thickness of the substrate is 130 microns, and the thickness of the conical waveguide is 500 microns.

[0054] The micro-ring waveguide includes a micro-ring resonant cavity and a grating array structure. The micro-ring resonant cavity is annular, and its size and thickness are determined by the operating frequency. The micro-ring resonant cavity is used to generate near-field coupling with the terahertz wave in the conical waveguide. The terahertz wave entering the micro-ring resonant cavity through near-field coupling meets the resonance condition n eff L = m λ m (n eff is the effective refractive index of the light mode in the resonant ring, L is the circumference of the resonant ring, m is the resonance order, λ m When the wavelength is the resonant wavelength, a resonance enhancement effect is generated with the terahertz wave in the conical waveguide, and the terahertz wave that meets the resonance condition is confined to be transmitted in the microring waveguide. The microring waveguide can excite a vortex beam with orbital angular momentum in the terahertz band.

[0055] The grating array structure is etched on the side wall of the micro-ring resonant cavity, and is used to scatter the vortex light beam in a direction perpendicular to the ring surface, so that the vortex light beam is vertically irradiated on the rotating object to be detected, and the rotating object to be detected receives the vortex light beam and scatters the echo signal. The grating array structure includes a plurality of gratings, and the plurality of gratings are evenly distributed on the inner side of the micro-ring resonant cavity, and the plurality of gratings are distributed in a ring shape with the central axis of the micro-ring resonant cavity as the axis, and the length, width and number of the gratings are related to the operating frequency. In this embodiment, the operating frequency is 180GHz, at which time the radius of the micro-ring resonant cavity is 6900 microns and the thickness is 500 microns, the length of a single grating is 300 microns, the width is 60 microns, and the number of gratings is 72.

[0056] The signal receiving end has a horn antenna and a second frequency doubling module. The horn antenna is used to receive the echo signal through the second frequency doubling module and feed it back to the vector network analyzer. The vector network analyzer is also used to analyze the phase difference of the echo signal to calculate the rotation speed of the rotating object to be detected. The present invention creatively uses the terahertz band, which is a hot research topic internationally, to generate a vortex beam, and uses the phase of light to directly detect the rotation speed of the object. The detection process is simple to operate, and the measurement results are accurate and reliable, avoiding the problems of large and complex measurement structure, low precision, high cost, etc. of conventional devices for detecting the rotation speed of rotating objects.

[0057] The method for detecting the rotation speed of an object using terahertz waves provided by the present invention can generate terahertz-band vortex beams of various modes. Adjusting the aspect ratio of the micro-ring waveguide can selectively excite a mode of a specific frequency, and adjusting the size of the grating can cause the micro-ring waveguide to excite a vortex beam with a specific orbital angular momentum. Although there are many ways to generate vortex beams internationally, they mainly use spiral phase plates and metasurface arrays, and these two methods can only generate vortex beams of one mode. In comparison, the device and method for detecting the rotation speed of an object using terahertz waves provided by the present invention creatively use the terahertz band to generate terahertz-band vortex beams of various modes, and use the phase of the terahertz-band vortex beam to directly detect the rotation speed of the object. The technical solution is novel, the detection process is convenient to operate, and the detection results are accurate and reliable, which solves the problems of large and complex measurement structure, low precision, and high cost of conventional rotating object rotation speed detection devices.

Claims

1. A device for detecting the rotation speed of an object using terahertz waves, used to measure the rotation speed of a rotating object to be detected, characterized in that: include: Terahertz source, terahertz vortex beam generator and signal receiving end, The terahertz source includes a vector network analyzer, a first frequency doubling module and a metal waveguide. The vector network analyzer is at least used to emit terahertz waves. The first frequency doubling module is used to adjust the frequency of microwaves to the terahertz operating frequency required by the user. The metal waveguide is connected to the first frequency doubling module as a signal output end, and is used to output the frequency-modulated terahertz waves. The terahertz vortex beam generator is used to generate a vortex beam in the terahertz band, and comprises a tapered waveguide, a micro-ring waveguide and a substrate. One end of the tapered waveguide is plugged into the metal waveguide to allow the terahertz wave to enter the tapered waveguide. The micro-ring waveguide is connected to the tapered waveguide and includes a micro-ring resonant cavity and a grating array structure. The terahertz wave in the tapered waveguide enters the micro-ring resonant cavity through near-field coupling, and the terahertz wave in the micro-ring resonant cavity generates a resonance enhancement effect with the terahertz wave in the tapered waveguide under a resonance condition. The terahertz wave that meets the resonance condition is confined to the micro-ring waveguide for transmission, and the micro-ring waveguide excites a vortex beam with orbital angular momentum in the terahertz band. The grating array structure is etched on the side wall or the top of the micro-ring resonant cavity, and is used to scatter the vortex light beam in a direction perpendicular to the ring surface, so that the vortex light beam is vertically irradiated on the rotating object to be detected, and the rotating object to be detected receives the vortex light beam and scatters the echo signal. The signal receiving end is used to receive the echo signal and feed it back to the vector network analyzer. The vector network analyzer is also used to analyze the echo signal to calculate the rotation speed of the rotating object to be detected.

2. The device for detecting the rotation speed of an object using terahertz waves according to claim 1, characterized in that: in, The signal receiving end also has a horn antenna and a second frequency multiplication module, the horn antenna is used to receive and feed back the echo signal, and the second frequency multiplication module is used to multiply the echo signal to a frequency that can be received by the vector network analyzer. The vector network analyzer calculates the rotation speed of the rotating object to be detected by analyzing the phase difference of the echo signal.

3. The device for detecting the rotation speed of an object using terahertz waves according to claim 1, characterized in that: in, In the terahertz vortex beam generator, the resonance condition is n eff L = m λ m , n eff is the effective refractive index of the light mode in the resonant ring, L is the circumference of the resonant ring, m is the resonance order, λ m is the resonant wavelength.

4. The device for detecting the rotation speed of an object using terahertz waves according to claim 1, characterized in that: in, The micro-ring resonant cavity is in the shape of a circular ring, and its size and thickness are determined by the operating frequency. The grating array structure includes a plurality of gratings, the plurality of gratings are evenly distributed on the inner side of the micro-ring resonant cavity, and the plurality of gratings are distributed in a ring shape with the central axis of the micro-ring resonant cavity as the axis, and the length, width and number of the gratings are related to the operating frequency. When the operating frequency is 180 GHz, the radius of the microring resonant cavity is 6900 microns and the thickness is 500 microns. The length of a single grating is 300 microns and the width is 60 microns. The number of gratings is 72.

5. The device for detecting the rotation speed of an object using terahertz waves according to claim 1, characterized in that: in, The distance between the tapered waveguide and the micro-ring waveguide should be such that the two waveguides have a coupling effect, and is usually not more than 200 microns.

6. The device for detecting the rotation speed of an object using terahertz waves according to claim 1, characterized in that: in, The substrate is used to connect the tapered waveguide and the microring waveguide and plays a supporting role, so that the length direction of the tapered waveguide is parallel to the longitudinal section of the microring resonant cavity. The thickness of the substrate is 130 microns, and the thickness of the tapered waveguide is 500 microns.

7. The device for detecting the rotation speed of an object using terahertz waves according to claim 1, characterized in that: in, The tapered waveguide, the micro-ring waveguide and the substrate are all made of high-resistance silicon material.

8. A method for detecting the rotation speed of an object using terahertz waves, performed using the device for detecting the rotation speed of an object using terahertz waves as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, using the vector network analyzer to transmit a microwave signal, the output microwave passes through the first frequency doubling module, the first frequency doubling module adjusts the frequency of the microwave to the terahertz operating frequency required by the user, and then the terahertz wave enters the tapered waveguide through the metal waveguide; Step 2, according to the resonance condition n eff L = m λ m , when L is an integer multiple of m, the terahertz wave in the tapered waveguide and the terahertz wave in the microring waveguide produce a resonance enhancement effect, the terahertz wave of a specific frequency is coupled into the microring waveguide and is confined to be transmitted in the microring waveguide, and the microring waveguide excites a vortex beam with orbital angular momentum; Step 3, placing the rotating object to be detected directly in front of the terahertz vortex beam generator, receiving the vortex beam, the echo signal scattered from the rotating object to be detected is received by the horn antenna of the signal receiving end, the horn antenna receives the echo signal and feeds it back to the vector network analyzer through the second frequency doubling module, the vector network analyzer analyzes the phase difference of the echo signal, thereby calculating the rotation speed of the rotating object to be detected.

9. The method for detecting the rotation speed of an object using terahertz waves according to claim 8, characterized in that: in, In step 1, the operating frequency is calculated according to the formula n eff L = m λ m , by adjusting the radius of the micro-ring waveguide and the number of the gratings, when the circumference L of the resonant ring increases, the resonant wavelength λ m As it increases, the operating wavelength increases, so the operating frequency decreases.

10. The method for detecting the rotation speed of an object using terahertz waves according to claim 8, characterized in that: in, In step 2, the size of the micro-ring waveguide is adjusted to control the distribution of the evanescent field of the waveguide. Adjusting the aspect ratio of the microring waveguide can selectively excite a mode of a specific frequency for regulating orbital angular momentum. By adjusting the size of the grating, the micro-ring waveguide can excite a vortex light beam with a specific orbital angular momentum, so that the vortex light beam can be detected right in front of the micro-ring waveguide.

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