A system and method for detecting ultra-high laser power based on vortex light interferometry measured by a torsion balance

Abstract

The present invention relates to a super-large laser power detection system and method based on vortex light interferometry measured by a torsion balance, belonging to the field of optical precision testing technology. The system comprises a laser to be measured, a reflector A, a fast-reflecting mirror A, a reflector B, a reflector C, a torsion balance, and a micro-displacement measurement system based on vortex light self-conjugate interferometry, wherein the reflector C and the reflector B are symmetrically distributed relative to the torsion balance; the micro-displacement measurement system based on vortex light self-conjugate interferometry is located below the torsion balance and is used to reversely obtain the power of the laser to be measured by rotating the angle of the vortex light petal-shaped interference pattern; the present invention converts the measurement of the super-large laser power into a displacement, and then transmits the micro-displacement through the torsion balance through the self-conjugate interferometry of the vortex light. The micro-displacement can be obtained by the rotation angle of the petal-shaped interference pattern, thereby obtaining the laser power value. The present invention has the advantages of high feasibility, novel structure, real-time monitoring of the output light beam, and high measurement accuracy.

Description

Technical Field

[0001] The present invention provides an ultra-large laser power detection system and method based on vortex light interference measured by a torsion balance, belonging to the technical field of optical precision testing. Background Art

[0002] With the development of laser technology, high-energy lasers are increasingly being used in scientific research, industry, and the military. Their application in the military, in particular, has not only significantly impacted the entire laser industry but also placed higher demands and challenges on laser metrology and testing. Laser power energy is a quantitative indicator of lasers and their most important and fundamental technical parameters. Accurately measuring laser radiation power and energy is crucial for evaluating laser performance and assessing the operational effectiveness of chemical or solid-state laser weapon systems.

[0003] High-power laser measurement methods in my country are primarily divided into integrating sphere and calorimetry. The integrating sphere method increases dramatically with laser power, making traceability complex and difficult to operate. Laser power energy meters developed using the calorimetry method are bulky and heavy, require item-by-item traceability, and have complex uncertainty assessments. Therefore, high-power laser development, production, and equipment companies urgently need simple and easy-to-use laser power measurement equipment.

[0004] The optical pressure method is an ideal method for measuring high-power lasers, with advantages such as high precision, light weight, and fast response time. Furthermore, it is directly traceable to mechanical standards, expanding the traceability of laser power and significantly improving the measurement uncertainty of high-energy laser power. However, in the International System of Units, mechanical quantities are derived and cannot be directly observed. They can usually be converted into visible macroscopic motion or deformation, or special physical effects can be used to convert pressure into other types of physical signals for measurement. For tiny forces such as optical pressure, regardless of the object chosen as the measurement medium, a more reasonable amplification device is required to improve the sensitivity and observability of the measurement results. The torsion balance method is a representative early method for optical pressure measurement. Light is directly irradiated onto a torsion balance, which rotates due to the force. The optical pressure is calculated based on the angle of rotation of the torsion balance. Summary of the Invention

[0005] In the field of ultra-high laser power measurement, the higher the laser power, the greater the heat generated, and the greater the impact on the accuracy of the measurement results. To address the current demand for ultra-high laser power detection and the shortcomings of current methods, the present invention provides an ultra-high laser power detection system and method based on vortex light interferometry measured by a torsion balance. This system and method offer advantages such as real-time monitoring of the output beam quality, high power detection accuracy, a large measurement range, and high efficiency. This system provides a new research approach and technical approach for the online detection and adjustment testing of large-aperture optical antennas.

[0006] The technical solution of the present invention is:

[0007] A super-large laser power detection system based on vortex light interferometry measured by a torsion balance includes a laser to be measured, a reflector A, a fast reflector A, a reflector B, a reflector C, a torsion balance, and a micro-displacement measurement system based on vortex light self-conjugate interferometry, wherein the reflector B is mounted on one side of the torsion balance and the reflector C is mounted on the other side of the torsion balance, and the reflector C and the reflector B are symmetrically distributed relative to the torsion balance.

[0008] The micro-displacement measurement system based on vortex light self-conjugate interference is located below the torsion balance and includes a fast mirror B, a measuring laser, a beam expansion and collimation system, a quarter wave plate, a vortex wave plate, a beam splitter A, a beam splitter B, a Dove prism, a reflector D, a beam splitter C, and a photodetector;

[0009] After the laser to be measured emits a light beam, it is incident on the reflector B through the reflector A. After the optical path is calibrated by the fast reflector A, it is emitted for subsequent laser processing. The reflector B and reflector C located on both sides of the torsion balance are displaced in opposite directions and at equal distances. The light beam emitted by the measuring laser passes through the beam expansion and collimation system, 1 / 4 wave plate, and vortex wave plate in sequence to form vortex light, which is split by the beam splitter A to form test light and reference light. The reference light reaches the photodetector through the beam splitter C. The test light reaches the fast reflector B through the beam splitter B, and is then reflected back to the beam splitter B by the reflector C and the fast reflector B. It passes through the Dove prism, reflector D, and beam splitter C in sequence to reach the photodetector. The reference light and the test light carrying the displacement information of the reflector C at one end of the torsion balance form interference at the photodetector, obtaining a petal-shaped interference pattern.

[0010] Preferably, the reflector A, reflector B, reflector C and reflector D are all coated with a high-reflection film.

[0011] Preferably, the measuring laser is a HeNe laser with a wavelength of 633 nm.

[0012] A method for measuring an ultra-high laser power detection system based on vortex light interferometry using a torsion balance measurement, comprising:

[0013] After the laser to be measured emits a light beam, it passes through reflector A and is incident on reflector B. After the light path is calibrated by fast reflector A, the light beam is emitted. The light beam is incident on reflector B and generates pressure, which converts the power of the laser to be measured into a light pressure value. The pressure causes a displacement of reflector B. The reflectors B and C on both sides of the torsion balance make equidistant displacements in opposite directions. The torsion balance converts the tiny displacement into an angle change. By connecting it to reflectors B and C, the displacement caused by the pressure can be converted into a change in the optical path of the light beam.

[0014] The light beam emitted by the measurement laser passes through the beam expansion and collimation system, 1 / 4 wave plate, and vortex wave plate in sequence to form vortex light with a topological charge of l. It is then split into test light and reference light by beam splitter A. The reference light reaches the photodetector through beam splitter C. The test light passes through beam splitter B to fast mirror B, and is then reflected back to beam splitter B by reflector C and fast mirror B. It passes through the Dove prism, reflector D, and beam splitter C in sequence to reach the photodetector. The reference light and the test light, which has a change in the optical path of the reflector C at one end of the torsion beam, interfere at the photodetector, obtaining a petal-shaped interference pattern of the vortex light.

[0015] The test beam carries the displacement information of the torsion balance mirror C, which is then tilt-corrected by the fast-reflection mirror B. When the laser under test is operating, the light pressure causes the mirror C to shift, which is reflected as a rotation in the angular petal-shaped interference pattern of the vortex light. By extracting the rotation angle of this petal-shaped interference pattern, the power and energy of ultra-high-power lasers can be measured.

[0016] After the laser beam to be measured is emitted, it passes through a power-light pressure conversion module and then exits for subsequent applications. Simultaneously, the light pressure-displacement conversion module and the displacement-angle conversion module convert the laser power measurement into a rotation angle measurement. The angle measurement is achieved through a vortex light interferometer module. The reference beam and the detection beam interfere at the photodetector.

[0017] The power-light-pressure conversion module means that the light emitted by the laser to be tested will generate pressure on the surface of the object, the magnitude of which can be derived from Maxwell's electromagnetic theory or the light quantum model;

[0018] The optical pressure-displacement conversion module consists of reflector A, reflector B, and quick reflector A. After the laser beam to be measured is emitted, it passes through reflector A coated with a high reflectivity film, and then enters reflector B at a certain incident angle. The direction of the optical path is then calibrated by quick reflector A.

[0019] The displacement-angle conversion module is implemented by a torsion balance. Due to its nature, a torsion balance can convert tiny displacements into angle changes. By connecting it to two reflectors, the displacement caused by pressure can be converted into a change in the optical path of the light beam.

[0020] The vortex light interferometer module is composed of a detection laser beam that passes through a Mach-Zehnder interferometer structure. The test beam carries the optical path change information brought about by the rotation of the torsion balance and interferes with the reference beam at the photodetector.

[0021] This invention uses the principle of measuring tiny displacements using vortex light self-conjugate interferometry to obtain power information for the laser being measured. The power of the laser being measured is converted into a light pressure value, which in turn translates into a tiny displacement of reflector B. This displacement of reflector B causes the torsion balance to rotate, which in turn drives the displacement of reflector C. This angular rotation then appears in the petal-shaped interference pattern of the vortex light, which can be reversed to determine the power of the laser being measured.

[0022] Preferably, the optical pressure measurement principle is as follows:

[0023] Although photons have no rest mass, they do have momentum. When a laser beam hits the surface of an object, it generates pressure. By using the light pressure effect, the laser power can be traced back to the applied force.

[0024] Photons not only have energy, but also momentum, which can be expressed as:

[0025] E=hν (1)

[0026]

[0027] Where c is the speed of light, ν is the frequency, h is Planck's constant, and E is the energy. is momentum;

[0028] When photons interact with matter, the momentum of the photons is transferred to the object, exerting a force on the object. The relationship between the light pressure value F and the laser output power P is:

[0029]

[0030] Where t is time, P is the output power of the laser to be measured;

[0031] When the light beam is incident on the reflector B at an angle β, the force acting perpendicularly on the reflector B is:

[0032] F=(2P / c)ρcosβ (4)

[0033] Wherein, ρ = R + (1-R) ​​α / 2, R is the reflectivity of the reflector B, α is the mirror absorptivity of the reflector B;

[0034] Therefore, there is a relationship between the output power and optical pressure value of the laser to be measured:

[0035] P = cF / 2ρcosβ (5).

[0036] Preferably, the present invention uses two reflectors and a fast-reflecting mirror to achieve undisturbed deflection of the optical path, so that subsequent applications of the laser after emission are not disturbed. The light pressure value is converted into micro-displacement through a torsion balance and a fast-reflecting mirror, completing the conversion from power to displacement physical quantity.

[0037] The system uses a torsion balance as a displacement transmission device. When mirror B moves, not only is there displacement, but mirror B itself also tilts at a small angle. This tilt angle can be adaptively compensated in real time through the fast-reflecting mirror A, thereby achieving the purpose of adjusting the direction of the light beam.

[0038] After turning on the laser to be tested, the incident light beam is reflected by reflector A to the center of reflector B, with an incident angle of θ1 and an exit angle of θ1. Mirror B is installed on one side of the torsion beam balance. When the light pressure changes, it shifts. Mirror A is adjusted so that the light is incident on the center of reflector B. The incident and exit angles become θ2. Fast reflector A adaptively corrects the deflection so that the light beam maintains its original exit direction.

[0039] The torsional stiffness of the torsion wire is used to measure the light pressure. According to the generalized Hooke's law, the torsional elastic coefficient of the torsion wire is

[0040]

[0041] Where M is the torque of the twisted wire, is the torsion angle of the torsion wire. Since the torsion wire is fixedly connected to the beam, the deflection angle of the beam is The scale beam divides the torsion wire into two parts, the torques at the upper and lower ends of the torsion wire during the torsion of the scale beam are

[0042] M1=Mb / (a+b) (7)

[0043] M2=Ma / (a+b) (8)

[0044] The deflection angle γ of the beam is

[0045] γ=Mab / GI ρ (a+b) (9)

[0046] Where G is the shear modulus of the torsion wire, I ρ is the polar moment of inertia of the torsion wire, a and b are the lengths of the two parts of the torsion wire cut by the balance beam, |M|=|M1|+|M2|, and the torsional elastic coefficient K of the torsion wire is

[0047]

[0048] Where, d is the diameter of the twisted wire;

[0049] The total length H of the upper and lower ends of the torsion wire is fixed. When a=b=H / 2, the torsional elastic coefficient K of the torsion wire is

[0050]

[0051] Torque M and the deflection angle of the torsion balance The relationship is

[0052]

[0053] The calculation formula of light pressure value F is:

[0054]

[0055] Wherein, L represents the magnitude of the optical pressure moment;

[0056] The calculation formula of micro displacement δ is:

[0057]

[0058] Therefore, when the laser source to be measured is incident on the reflector B at an angle of β, the small displacement of the reflector C is:

[0059]

[0060] Preferably, the micro-displacement measurement system based on vortex light self-conjugate interference uses the self-conjugate interference of vortex light to measure the tiny displacement of the reflector C. One path of light carries the displacement of the torsion balance reflector C, and the optical path difference between the two paths of light is reflected in the angle of the petal-shaped interference pattern. Before and after the laser power measurement, the interference fringes have different angles, which are used as input for data processing to obtain displacement information.

[0061] In vortex light self-conjugate interferometry, the most notable feature of the vortex beam is its spiral azimuthal phase structure. To facilitate the analysis of subsequent displacement measurement methods, the electric field distribution of the reference light in polar coordinates (r, θ) is expressed as:

[0062] E ref (r,θ)=A·exp[i(lθ+kz1)] (16)

[0063] Where A is the amplitude, l is the topological charge number, θ is the azimuth angle, k = 2π / λ is the wave number, λ is the wavelength, z1 is the initial arm length of the reference arm, the test light is conjugated with the reference light, and the electric field distribution of the conjugate vortex beam can be expressed as:

[0064] E conjugate (r,θ)=A·exp[-i(lθ-kz2)] (17)

[0065] Where z2 is the initial arm length of the test arm;

[0066] The intensity distribution of the vortex light self-conjugate interference light field can be expressed as:

[0067] I=|E ref +E conjugate | 2 =C0+C0·cos[2lθ+k(z1-z2)] (18)

[0068] Where: C0 = 2A 2 is a constant, the self-conjugate interference of the vortex light will form a symmetrical petal-shaped interference light intensity distribution, and the number of petals is twice the absolute value of the topological charge;

[0069] The object to be tested (i.e., reflector C) is placed in the test light path. When the object to be tested produces a displacement d, the optical path of the test arm in the interference light path changes by 2d. At this time, the electric field intensity E of the test light end The changes that follow can be expressed as:

[0070] E end (r,θ)=A·exp[-i(lθ-kz2)]·exp(ik·2d) (19)

[0071] At this time, the vortex light conjugate interference intensity distribution can be expressed as:

[0072] I end =|E ref +E end | 2 =C0+C0·cos[2lθ+k(z1-z2)-2kd] (20)

[0073] From formula (10), we can see that when the object to be measured produces a displacement change, the interference pattern formed will rotate accordingly. If the rotation angle radian is set to Δθ, then there is an equivalent relationship in the displacement process:

[0074] 2lΔθ=2kd (21)

[0075] The displacement d can be expressed as:

[0076] d=lΔθ / k=λlΔθ / 2π (22)

[0077] Where λ and l are both known quantities, so the measurement of displacement d is converted into the accurate extraction of Δθ.

[0078] The present invention designs a micro-displacement measurement system based on vortex light self-conjugate interferometry. The system consists of a measuring laser, a beam expansion and collimation system, a quarter-wave plate (QWP), a vortex wave plate (VR), a beam splitter A, a beam splitter B, a beam splitter C, a reflector D, a fast-reflecting mirror B, a dove prism, and a photodetector. The light source is a HeNe laser with a wavelength of 633 nm. The stable linearly polarized plane wave output by the measuring laser is expanded and collimated, then modulated by the quarter-wave plate to become circularly polarized light. This beam passes through the vortex wave plate to produce stable vortex light. After passing through beam splitter A, the beam is split into two paths: a test beam passes through beam splitter A, beam splitter B, and fast-reflecting mirror B, hits the reflector C to be measured, is reflected, and then returns in the original direction. It then passes through beam splitter B, passes through the dove prism, reflector D, and beam splitter C to enter the photodetector. A reference beam passes through beam splitter A and beam splitter C, and together with the test beam, is irradiated into the photodetector to produce interference. Because the number of reflections is odd or even, the two beams are conjugated, and the changes in the conjugate interference pattern of the vortex light are recorded. The collected data is processed using data processing software to obtain the rotation angle radian Δθ, and then the precise displacement data is obtained.

[0079] Where the present invention is not exhaustive, please refer to the prior art.

[0080] The beneficial effects of the present invention are:

[0081] 1. The invention has a novel concept, combining laser power measurement with vortex optical interferometry to measure tiny displacements, providing a new approach for measuring ultra-large laser power energy at the 10,000-watt level with milliwatt-level resolution, with the advantages of real-time monitoring of the output beam quality, high power detection accuracy, large range, and high efficiency.

[0082] 2. The present invention uses a fast-reflecting mirror to adaptively correct the deflection, thereby realizing real-time measurement of the outgoing light beam.

[0083] 3. The present invention adopts the idea of ​​adaptive compensation of fast reflection mirror to solve the distortion problem of interference pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The drawings in the specification, which constitute a part of this application, are used to provide further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute improper limitations on this application.

[0085] Figure 1 Schematic diagram of the ultra-high laser power detection system based on vortex light interferometry measured by torsion balance;

[0086] Figure 2 Schematic diagram of light pressure measurement;

[0087] Figure 3 Schematic diagram of micro-displacement measurement;

[0088] Among them, 1-laser to be measured, 2-mirror A, 3-fast mirror A, 4-mirror B, 5-mirror C, 6-torsion balance, 7-fast mirror B, 8-measuring laser, 9-beam expansion and collimation system, 10-1 / 4 wave plate, 11-vortex wave plate, 12-beam splitter A, 13-beam splitter B, 14-Dove prism, 15-mirror D, 16-beam splitter C, 17-photodetector. DETAILED DESCRIPTION

[0089] In order to enable people in this technical field to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings in the implementation of this specification, but are not limited to this. Anything not fully described in the present invention shall be based on the conventional technology in this field.

[0090] Example 1

[0091] A super-large laser power detection system based on vortex light interferometry measured by torsion balance, such as Figure 1-3 As shown, it includes a laser to be measured 1, a reflector A2, a fast reflector A3, a reflector B4, a reflector C5, a torsion scale 6, and a micro-displacement measurement system based on vortex light self-conjugate interference, wherein the reflector B4 is installed on one side of the torsion scale 6, and the reflector C5 is installed on the other side of the torsion scale 6, and the reflector C5 and the reflector B4 are symmetrically distributed relative to the torsion scale 6;

[0092] The micro-displacement measurement system based on vortex light self-conjugate interferometry is located below the torsion balance and includes a fast mirror B 7, a measuring laser 8, a beam expansion and collimation system 9, a quarter-wave plate 10, a vortex wave plate 11, a beam splitter A 12, a beam splitter B 13, a Dove prism 14, a reflector D 15, a beam splitter C 16, and a photodetector 17.

[0093] After the laser 1 to be measured emits a light beam, it passes through the reflector A2 and is incident on the reflector B4. After the optical path is calibrated by the fast reflector A3, it is emitted for subsequent laser processing. The reflector B4 and the reflector C5 located on both sides of the torsion balance are displaced in opposite directions and at equal distances. The light beam emitted by the measuring laser 8 passes through the beam expansion and collimation system 9, the 1 / 4 wave plate 10, and the vortex wave plate 11 in sequence to form vortex light. The beam is split by the beam splitter A12 to form test light and reference light. The reference light reaches the photodetector 17 through the beam splitter C16. The test light reaches the fast reflector B7 through the beam splitter B13, and is then reflected back to the beam splitter B13 by the reflector C5 and the fast reflector B7. It passes through the Dove prism 14, the reflector D15, and the beam splitter C16 in sequence to reach the photodetector 17. The reference light and the test light carrying the displacement information of the reflector C at one end of the torsion balance form interference at the photodetector 17, forming a petal-shaped interference pattern.

[0094] Reflector A, reflector B, reflector C and reflector D are all coated with high reflective film.

[0095] The measuring laser 8 is a HeNe laser with a wavelength of 633 nm.

[0096] Example 2

[0097] A method for measuring an ultra-high laser power detection system based on vortex light interferometry measured by a torsion balance, comprising:

[0098] After the laser 1 to be tested emits a light beam, it passes through reflector A2 and is incident on reflector B4. After the light path is calibrated by fast reflector A3, the light beam is emitted. The light beam incident on reflector B4 generates pressure, which converts the power of the laser to be tested into a light pressure value. The pressure causes a displacement of reflector B. Reflectors B and C, located on both sides of the torsion balance, move in opposite directions and at equal distances. The torsion balance converts the tiny displacement into an angular change. By connecting it to reflectors B and C, the displacement caused by the pressure can be converted into a change in the optical path of the light beam.

[0099] The light beam emitted by the measuring laser 8 passes through the beam expansion and collimation system 9, the quarter-wave plate 10, and the vortex wave plate 11 in sequence to form a vortex light with a topological charge of 1. The light beam is then split by the beam splitter A12 to form a test light and a reference light. The reference light reaches the photodetector 17 via the beam splitter C16. The test light reaches the fast mirror B7 via the beam splitter B13, and is then reflected back to the beam splitter B13 by the reflector C5 and the fast mirror B7. The light beam passes through the Dove prism 14, the reflector D15, and the beam splitter C16 in sequence to reach the photodetector 17. The reference light and the test light whose optical path length is changed by the reflector C at one end of the torsion beam interfere at the photodetector 17, obtaining a petal-shaped interference pattern of the vortex light.

[0100] The test beam carries the displacement information of the torsion balance mirror C, which is then tilt-corrected by the fast-reflection mirror B. When the laser under test is operating, the light pressure causes the mirror C to shift, which is reflected as a rotation in the angular petal-shaped interference pattern of the vortex light. By extracting the rotation angle of this petal-shaped interference pattern, the power and energy of ultra-high-power lasers can be measured.

[0101] After the laser beam to be measured is emitted, it passes through a power-light pressure conversion module and then exits for subsequent applications. Simultaneously, the light pressure-displacement conversion module and the displacement-angle conversion module convert the laser power measurement into a rotation angle measurement. The angle measurement is achieved through a vortex light interferometer module. The reference beam and the detection beam interfere at the photodetector.

[0102] The power-light-pressure conversion module means that the light emitted by the laser to be tested will generate pressure on the surface of the object, the magnitude of which can be derived from Maxwell's electromagnetic theory or the light quantum model;

[0103] The optical pressure-displacement conversion module consists of reflector A, reflector B, and quick reflector A. After the laser beam to be measured is emitted, it passes through reflector A coated with a high reflectivity film, and then enters reflector B at a certain incident angle. The direction of the optical path is then calibrated by quick reflector A.

[0104] The displacement-angle conversion module is implemented by a torsion balance. Due to its nature, a torsion balance can convert tiny displacements into angle changes. By connecting it to two reflectors, the displacement caused by pressure can be converted into a change in the optical path of the light beam.

[0105] The vortex light interferometer module is composed of a detection laser beam that passes through a Mach-Zehnder interferometer structure. The test beam carries the optical path change information brought about by the rotation of the torsion balance and interferes with the reference beam at the photodetector.

[0106] This invention uses the principle of measuring tiny displacements using vortex light self-conjugate interferometry to obtain power information for the laser being measured. The power of the laser being measured is converted into a light pressure value, which in turn translates into a tiny displacement of reflector B. This displacement of reflector B causes the torsion balance to rotate, which in turn drives the displacement of reflector C. This angular rotation then appears in the petal-shaped interference pattern of the vortex light, which can be reversed to determine the power of the laser being measured.

[0107] The principle of light pressure measurement is as follows:

[0108] Although photons have no rest mass, they do have momentum. When a laser beam hits the surface of an object, it generates pressure. By using the light pressure effect, the laser power can be traced back to the applied force.

[0109] Photons not only have energy, but also momentum, which can be expressed as:

[0110] E=hν (1)

[0111]

[0112] Where c is the speed of light, ν is the frequency, h is Planck's constant, and E is the energy. is momentum;

[0113] When photons interact with matter, the momentum of the photons is transferred to the object, exerting a force on the object. The relationship between the light pressure value F and the laser output power P is:

[0114]

[0115] Where t is time, P is the output power of the laser to be measured;

[0116] When the light beam is incident on the reflector B at an angle β, the force acting perpendicularly on the reflector B is:

[0117] F=(2P / c)ρcosβ (4)

[0118] Wherein, ρ = R + (1-R) ​​α / 2, R is the reflectivity of the reflector B, α is the mirror absorptivity of the reflector B;

[0119] Therefore, there is a relationship between the output power and optical pressure value of the laser to be measured:

[0120] P = cF / 2ρcosβ (5).

[0121] The invention uses two reflectors and a quick-reflection mirror to achieve undisturbed deflection of the optical path, ensuring that subsequent applications of the laser after emission are not disturbed. The light pressure value is converted into micro-displacement through a torsion balance and a quick-reflection mirror, completing the conversion from power to displacement.

[0122] The system uses a torsion balance as a displacement transmission device. When mirror B moves, not only is there displacement, but mirror B itself also tilts at a small angle. This tilt angle can be adaptively compensated in real time through the fast-reflecting mirror A, thereby achieving the purpose of adjusting the direction of the light beam.

[0123] After turning on the laser to be tested, the incident light beam is reflected by reflector A to the center of reflector B, with an incident angle of θ1 and an exit angle of θ1. Mirror B is installed on one side of the torsion beam balance. When the light pressure changes, it shifts. Mirror A is adjusted so that the light is incident on the center of reflector B. The incident and exit angles become θ2. Fast reflector A adaptively corrects the deflection so that the light beam maintains its original exit direction.

[0124] The torsional stiffness of the torsion wire is used to measure the light pressure. According to the generalized Hooke's law, the torsional elastic coefficient of the torsion wire is

[0125]

[0126] Where M is the torque of the twisted wire, is the torsion angle of the torsion wire. Since the torsion wire is fixedly connected to the beam, the deflection angle of the beam is The scale beam divides the torsion wire into two parts, the torques at the upper and lower ends of the torsion wire during the torsion of the scale beam are

[0127] M1=Mb / (a+b) (7)

[0128] M2=Ma / (a+b) (8)

[0129] The deflection angle γ of the beam is

[0130] γ=Mab / GI ρ (a+b) (9)

[0131] Where G is the shear modulus of the torsion wire, I ρis the polar moment of inertia of the torsion wire, a and b are the lengths of the two parts of the torsion wire cut by the balance beam, |M|=|M1|+|M2|, and the torsional elastic coefficient K of the torsion wire is

[0132]

[0133] Where, d is the diameter of the twisted wire;

[0134] The total length H of the upper and lower ends of the torsion wire is fixed. When a=b=H / 2, the torsional elastic coefficient K of the torsion wire is

[0135]

[0136] Torque M and the deflection angle of the torsion balance The relationship is

[0137]

[0138] The calculation formula of light pressure value F is:

[0139]

[0140] Wherein, L represents the magnitude of the optical pressure moment;

[0141] The calculation formula of micro displacement δ is:

[0142]

[0143] Therefore, when the laser source to be measured is incident on the reflector B at an angle of β, the small displacement of the reflector C is:

[0144]

[0145] The micro-displacement measurement system based on vortex light self-conjugate interferometry uses the self-conjugate interferometry of vortex light to measure the tiny displacement of the reflector C. One of the light paths carries the displacement of the torsion balance reflector C. The optical path difference between the two light paths is reflected in the rotation angle of the petal-shaped interference pattern. Before and after the laser power measurement, the interference fringes have different angles, which serve as the input for data processing to obtain the displacement information.

[0146] In vortex light self-conjugate interferometry, the most notable feature of the vortex beam is its spiral azimuthal phase structure. To facilitate the analysis of subsequent displacement measurement methods, the electric field distribution of the reference light in polar coordinates (r, θ) is expressed as:

[0147] E ref (r,θ)=A·exp[i(lθ+kz1)] (16)

[0148] Where A is the amplitude, l is the topological charge number, θ is the azimuth angle, k = 2π / λ is the wave number, λ is the wavelength, z1 is the initial arm length of the reference arm, the test light is conjugated with the reference light, and the electric field distribution of the conjugate vortex beam can be expressed as:

[0149]

[0150] Where z2 is the initial arm length of the test arm;

[0151] The intensity distribution of the vortex light self-conjugate interference light field can be expressed as:

[0152] I=|E ref +E conjugate | 2 =C0+C0·cos[2lθ+k(z1-z2)] (18)

[0153] Where: C0 = 2A 2 is a constant, the self-conjugate interference of the vortex light will form a symmetrical petal-shaped interference light intensity distribution, and the number of petals is twice the absolute value of the topological charge;

[0154] The object to be tested (i.e., reflector C) is placed in the test light path. When the object to be tested produces a displacement d, the optical path of the test arm in the interference light path changes by 2d. At this time, the electric field intensity E of the test light end The changes that follow can be expressed as:

[0155] E end (r,θ)=A·exp[-i(lθ-kz2)]·exp(ik·2d) (19)

[0156] At this time, the vortex light conjugate interference intensity distribution can be expressed as:

[0157] I end =|E ref +E end | 2 =C0+C0·cos[2lθ+k(z1-z2)-2kd] (20)

[0158] From formula (10), we can see that when the object to be measured produces a displacement change, the interference pattern formed will rotate accordingly. If the rotation angle radian is set to Δθ, then there is an equivalent relationship in the displacement process:

[0159] 2lΔθ=2kd (21)

[0160] The displacement d can be expressed as:

[0161] d=lΔθ / k=λlΔθ / 2π (22)

[0162] Where λ and l are both known quantities, so the measurement of displacement d is converted into the accurate extraction of Δθ.

[0163] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An ultra-high laser power detection system based on vortex light interferometry measured by a torsion balance, characterized in that: The invention comprises a laser to be measured, a reflector A, a fast reflector A, a reflector B, a reflector C, a torsion balance and a micro-displacement measurement system based on vortex light self-conjugate interferometry, wherein the reflector B is installed on one side of the torsion balance and the reflector C is installed on the other side of the torsion balance, and the reflector C and the reflector B are symmetrically distributed relative to the torsion balance; The micro-displacement measurement system based on vortex light self-conjugate interferometry is located below the torsion balance and includes a fast reflector B, a measuring laser, a beam expansion and collimation system, a quarter wave plate, a vortex wave plate, a beam splitter A, a beam splitter B, a Dove prism, a reflector D, a beam splitter C, and a photodetector. After the laser to be measured emits a light beam, it is incident on the reflector B through the reflector A, and then emitted after the optical path is calibrated by the fast reflector A. The reflector B and reflector C located on both sides of the torsion balance make opposite equidistant displacements; the light beam emitted by the measuring laser passes through the beam expansion and collimation system, 1 / 4 wave plate, and vortex wave plate in sequence to form vortex light, which is then split by the beam splitter A to form test light and reference light. The reference light reaches the photodetector through the beam splitter C; the test light reaches the reflector C through the beam splitter B and the fast reflector B, and is then reflected back to the beam splitter B by the reflector C and the fast reflector B, and passes through the Dove prism, reflector D, and beam splitter C in sequence to reach the photodetector. The reference light and the test light carrying the displacement information of the reflector C at one end of the torsion balance form interference at the photodetector, obtaining a petal-shaped interference pattern.

2. The ultra-high laser power detection system based on vortex light interferometry measured by a torsion balance according to claim 1, characterized in that: The reflector A, reflector B, reflector C and reflector D are all coated with a high-reflection film.

3. The ultra-high laser power detection system based on vortex light interferometry measured by a torsion balance according to claim 1, characterized in that: The measurement laser is a HeNe laser with a wavelength of 633 nm.

4. A method for measuring an ultra-high laser power detection system based on vortex light interferometry using a torsion balance as claimed in claim 1, characterized in that: include: After the laser to be measured emits a light beam, it passes through reflector A and is incident on reflector B. After the light path is calibrated by fast reflector A, the light beam is emitted. The light beam incident on reflector B generates pressure, which converts the power of the laser to be measured into a light pressure value. The pressure causes a displacement of reflector B. Mirrors B and C, located on both sides of the torsion balance, move in opposite directions and at equal distances. The torsion balance converts the tiny displacement into an angular change. By connecting it to reflectors B and C, the displacement caused by the pressure can be converted into a change in the optical path of the light beam. The light beam emitted by the measuring laser passes through the beam expansion and collimation system, 1 / 4 wave plate, and vortex wave plate in sequence to form vortex light, which is then split by beam splitter A to form test light and reference light. The reference light reaches the photodetector through beam splitter C; the test light reaches the reflector C through beam splitter B and fast mirror B, and is then reflected back to beam splitter B by reflector C and fast mirror B. It passes through the Dove prism, reflector D, and beam splitter C in sequence to reach the photodetector. The reference light and the test light with the change in the optical path of the reflector C at one end of the torsion balance form interference at the photodetector, obtaining a petal-shaped interference pattern of the vortex light. The power of the laser to be measured is obtained by reverse deduction through the angular rotation appearing in the petal-shaped interference pattern of the vortex light.

5. The method for measuring ultra-high laser power detection system based on vortex light interferometry of torsion balance measurement according to claim 4, characterized in that: The principle of light pressure measurement is as follows: When a laser beam hits the surface of an object, it generates pressure. By using the light pressure effect, the laser power can be traced back to the applied force. Photons not only have energy, but also momentum, which can be expressed as: E=hν (1) Where c is the speed of light, ν is the frequency, h is Planck's constant, and E is the energy. is momentum; When photons interact with objects, the momentum of the photons is transferred to the objects, exerting force on the objects. The relationship between the light pressure value F and the laser output power P is: Where t is time, P is the output power of the laser to be measured; When the light beam is incident on the reflector B at an angle β, the light pressure acting perpendicularly on the reflector B is: F=(2P / c)ρcosβ (4) Wherein, ρ = R + (1-R) ​​α / 2, R is the reflectivity of the reflector B, α is the mirror absorptivity of the reflector B; Therefore, there is a relationship between the output power and optical pressure value of the laser to be measured: P = cF / 2ρcosβ (5).

6. The method for measuring ultra-high laser power detection system based on vortex light interferometry of torsion balance measurement according to claim 5, characterized in that: After turning on the laser to be tested, the incident light beam is reflected by reflector A to the center of reflector B, with an incident angle of θ1 and an exit angle of θ1. Mirror B is mounted on one side of the torsion balance and shifts when the light pressure changes. Mirror A is adjusted so that the light is incident on the center of reflector B, and the incident and exit angles become θ2. Fast reflector A adaptively corrects the deflection, so that the beam maintains its original exit direction. The torsion balance uses the torsional stiffness of the torsion wire to measure the light pressure. According to the generalized Hooke's law, the torsional elastic coefficient of the torsion wire is Where M is the torque of the twisted wire, is the torsion angle of the torsion wire. Since the torsion wire is fixedly connected to the beam, the deflection angle of the beam is The scale beam divides the torsion wire into two parts, the torques at the upper and lower ends of the torsion wire during the torsion of the scale beam are M1=Mb / (a+b) (7) M2=Ma / (a+b) (8) The deflection angle γ of the beam is γ=Mab / GI ρ (a+b) (9) Where G is the shear modulus of the torsion wire, I ρ is the polar moment of inertia of the torsion wire, a and b are the lengths of the two parts of the torsion wire cut by the balance beam, |M|=|M1|+|M2|, and the torsional elastic coefficient K of the torsion wire is Where, d is the diameter of the twisted wire; The total length H of the upper and lower ends of the torsion wire is fixed. When a=b=H / 2, the torsional elastic coefficient K of the torsion wire is Torque M and torsion angle of torsion wire The relationship is The calculation formula of light pressure value F is: Wherein, L represents the magnitude of the optical pressure moment; The calculation formula of micro displacement δ is: Therefore, when the laser to be measured is incident on the reflector B at an angle of β, the small displacement of the reflector C is:

7. The method for measuring ultra-high laser power detection system based on vortex light interferometry of torsion balance measurement according to claim 6, characterized in that: The micro-displacement measurement system based on vortex light self-conjugate interferometry uses vortex light self-conjugate interferometry to measure the micro-displacement of the reflector C. In vortex light self-conjugate interferometry, the most significant feature of vortex light is its spiral azimuthal phase structure. The electric field distribution of the reference light in polar coordinates (r, θ) is expressed as: E ref (r,θ)=A·exp[i(lθ+kz1)] (16) Where A is the amplitude, l is the topological charge number, θ is the azimuth angle, k = 2π / λ is the wave number, i represents the imaginary unit in the complex number, λ is the wavelength, z1 is the initial arm length of the reference arm, the test light is conjugated with the reference light, and the electric field distribution of the conjugate vortex light is expressed as: E conjugate (r,θ)=A·exp[-i(lθ-kz2)] (17) Where z2 is the initial arm length of the test arm; The intensity distribution of the vortex light self-conjugate interference light field is expressed as: I=|E ref +E conjugate | 2 =C0+C0·cos[2lθ+k(z1-z2)] (18) Where: C0 = 2A 2 is a constant, the self-conjugate interference of the vortex light will form a symmetrical petal-shaped interference light intensity distribution, and the number of petals is twice the absolute value of the topological charge number; The object to be tested is placed in the test light path. When the object to be tested produces a displacement d, the optical path of the test arm in the interference light path changes by 2d. At this time, the electric field intensity E of the test light end It changes accordingly, expressed as: E end (r,θ)=A·exp[-i(lθ-kz2)]·exp(ik·2d) (19) At this time, the vortex light conjugate interference intensity distribution is expressed as: I end =|E ref +E end | 2 =C0+C0·cos[2lθ+k(z1-z2)-2kd] (20) From formula (10), we know that when the object to be measured produces a displacement change, the interference pattern formed will rotate accordingly. If the rotation angle radian is set to Δθ, then there is an equivalent relationship in the displacement process: 2lΔθ=2kd (21) The displacement d is expressed as: d=lΔθ / k=λlΔθ / 2π (22) Where λ and l are both known quantities, so the measurement of displacement d is converted into the accurate extraction of Δθ.

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