Oversized laser power detection system and method for vortex light interference based on torsion balance measurement

Abstract

The invention relates to an ultra-large laser power detection system and method based on vortex light interference of torsion balance measurement, and belongs to the technical field of optical precision testing, and the system comprises a laser to be tested, 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-conjugation interference, the reflecting mirror C and the reflecting mirror B are symmetrically distributed relative to the torsional balance; the micro-displacement measurement system based on vortex light self-conjugation interference is positioned below the torsion balance and is used for reversely deducing the power of the laser to be measured through angle rotation of a petal-shaped interference pattern of vortex light; measurement of ultra-large laser power is converted into displacement, then micro displacement is transmitted through the torsion balance and then is subjected to self-conjugation interference of vortex light, the micro displacement can be obtained through the rotation angle of a petal-shaped interference pattern, and therefore the laser power value is obtained. The device has the advantages of high feasibility, novel structure, real-time emergent beam monitoring, high measurement precision and the like.

Description

Technical Field

[0001] The 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 used in scientific research, industry, and military fields. In particular, its application in the military field has not only had a great impact on the entire laser industry, but also put forward higher requirements and challenges for the level of laser metrology and testing. Laser power energy is a quantitative indicator of lasers and the most important and basic key technical parameters of lasers. The accurate measurement of laser radiation power and energy is crucial to the evaluation of laser performance and the evaluation of the combat effectiveness of chemical or solid laser weapon systems.

[0003] The main high-power laser measurement methods in my country are the integrating sphere method and the calorimetric method. Integrating sphere method: As the laser power increases, the volume of the integrating sphere increases dramatically and the traceability is complicated, making it difficult to operate; the laser power energy meter developed by the calorimetric method is large in size and weight, with item-by-item traceability and complex uncertainty assessment. Therefore, the research, production, and equipment units of high-power lasers have an urgent need for laser power measurement equipment that is simple to operate and easy to use.

[0004] The light pressure method is an ideal method for measuring high-power lasers, with the advantages of high precision, light weight, and fast response time. Moreover, it can be directly traced back to mechanical standards, which expands the traceability of laser power and greatly improves the measurement uncertainty of high-energy laser power. However, in the International System of Units, mechanical quantities are derived quantities and cannot be directly observed. They can usually be converted into visible macroscopic object motion or deformation, or special physical effects can be used to convert pressure into other types of physical signals for measurement. For a tiny force like light pressure, no matter what object is chosen as the measurement medium, a more reasonable amplification device needs to be set up to improve the sensitivity and observability of the measurement results. The torsion balance method is a representative method of early light pressure measurement. Light is directly irradiated on the torsion balance. Due to the action of the force, the torsion balance will rotate, and the light pressure is calculated based on the angle of rotation of the torsion balance. Summary of the invention

[0005] In the field of ultra-large 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. In response to the current demand for ultra-large laser power detection and the shortcomings of current methods, the present invention provides an ultra-large laser power detection system and method based on vortex light interferometry measured by a torsion balance, which has the advantages of real-time monitoring of the quality of the output beam, high power detection accuracy, large range, and high efficiency, and provides a new research idea and technical approach for the online detection and adjustment test 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 interference measured by a torsion balance comprises a laser to be measured, a reflector A, a fast reflection mirror A, a reflector B, a reflector C, a torsion balance and a micro-displacement measurement system based on vortex light self-conjugate interference, wherein the reflector B is mounted on one side of the torsion balance, 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 reflection mirror B, a measuring laser, a beam expansion and collimation system, a 1 / 4 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 tested emits a light beam, it is incident on the reflector B through the reflector A, and then is emitted after the optical path is calibrated by the fast reflector A for subsequent laser processing. The reflector B and the reflector C located on both sides of the torsion balance make reverse 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 turn to form vortex light, which is split by the beam splitter A to form test light and reference light, and 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, and passes through the Dove prism, reflector D, and beam splitter C in turn 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 to obtain 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 measured by a torsion balance comprises:

[0013] After the laser to be tested emits a light beam, it is incident on the reflector B through the reflector A. After the light path is calibrated by the fast reflector A, the light beam is incident on the reflector B to generate pressure, which converts the power of the laser to be tested into a light pressure value. The pressure causes displacement of the reflector B. The reflectors B and C on both sides of the torsion scale make equidistant displacements in opposite directions. The torsion scale converts the tiny displacement into an angle change. By connecting it with the 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 measuring laser is sequentially passed through the beam expansion and collimation system, the quarter wave plate, and the vortex wave plate to form a vortex light with a topological charge of l, which is then split by beam splitter A to form a test light and a reference light. The reference light reaches the photodetector via beam splitter C; the test light reaches the fast mirror B via beam splitter B, and is then reflected back to beam splitter B by reflector C and fast mirror B, and sequentially passes through the Dove prism, reflector D, and beam splitter C 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 beam form interference at the photodetector to obtain a petal-shaped interference pattern of the vortex light;

[0015] The test beam carries the displacement information of the torsion balance reflector C, which is tilt-corrected by the fast mirror B. When the laser to be tested is running, the reflector C is displaced by the light pressure, which is reflected as the rotation of the angle of the petal-shaped interference pattern of the vortex light. By extracting the rotation angle of the petal-shaped interference pattern, the power energy of the ultra-high-power laser can be measured.

[0016] After the laser beam to be measured is emitted, it is emitted after passing through a power-light pressure conversion module for subsequent application; at the same time, the measurement of the laser power is converted into the measurement of the angle of rotation through a light pressure-displacement conversion module and a displacement-angle conversion module; the measurement of the angle size is realized through a vortex light interference module; the reference beam and the detection beam interfere at the photoelectric detector;

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

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

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

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

[0021] The present invention obtains the power information of the laser to be measured based on the principle of measuring micro-displacement by vortex light self-conjugate interference. The power of the laser to be measured is converted into a light pressure value, and the magnitude of the light pressure value is converted into a micro-displacement of the reflector B. The displacement of the reflector B causes the rotation of the torsion balance, thereby driving the displacement of the reflector C. Then, an angle rotation appears in the petal-shaped interference pattern of the vortex light, and the power of the laser to be measured is obtained by reverse deduction.

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

[0023] Although photons have no rest mass, they 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 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 force on the object. The relationship between the light pressure value F and the laser output power P is:

[0029]

[0030] Where, t is the 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 tested:

[0035] P = cF / 2ρcosβ (5).

[0036] Preferably, the present invention uses two reflectors and one fast-reflecting mirror to realize the non-disturbance reversal of the optical path, and the subsequent application of the laser after emission is not disturbed. The light pressure value is converted into micro-displacement by 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 the reflector B moves, not only is there displacement, but the reflector B itself also tilts at a small angle. This inclination angle can be adaptively compensated in real time through the fast reflection 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. Reflector B is installed on one side of the torsion beam balance and is displaced after the load-bearing light pressure changes. Reflector A is adjusted so that the light is incident on the center of reflector B, and the incident angle and exit angle become θ2. The fast reflector A adaptively corrects the deflection so that the light beam remains in the original direction to be emitted;

[0039] The torsion scale 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

[0040]

[0041] Where M is the torque of the torsion wire, is the torsion angle of the torsion wire. Since the torsion wire is fixedly connected to the scale bar, the deflection angle of the scale bar is The scale bar 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 bar are

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

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

[0044] The deflection angle γ of the scale 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] Among them, 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, a micro-displacement measurement system based on vortex light self-conjugate interference uses vortex light self-conjugate interference to measure the tiny displacement of the reflector C, where one light path carries the displacement of the torsion balance reflector C, and 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 are used as input for data processing to obtain displacement information.

[0061] In the vortex light self-conjugate interference, the most notable feature of the vortex beam is its spiral azimuthal phase structure. In order to facilitate the analysis of the subsequent displacement measurement method, 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 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 light intensity distribution can be expressed as:

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

[0073] It can be seen from formula (10) 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 interference, which 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 mirror B, a Dove prism and a photodetector. The light source selects a HeNe laser with a wavelength of 633nm. The stable linearly polarized plane wave output by the measuring laser is converted into circularly polarized light after being expanded and collimated by the quarter wave plate. The light beam can obtain stable vortex light after passing through the vortex wave plate. After passing through the beam splitter A, the light beam is divided into two paths: the test light beam passes through the beam splitter A, the beam splitter B, and the fast mirror B, hits the reflector C to be measured, reflects, and then returns along the original direction, and passes through the beam splitter B, passes through the Dove prism, the reflector D and the beam splitter C to enter the photodetector; after passing through the beam splitter A and the beam splitter C, the reference light beam is irradiated into the photodetector together with the test light beam to generate interference. Since the reflection times are different, the two beams are conjugated, and the changes in the vortex light conjugate interference pattern 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] For any details not provided in the present invention, please refer to the prior art.

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

[0081] 1. The invention has a novel concept, which combines laser power measurement with vortex optical interferometry measurement of tiny displacements, and provides a new idea for measuring ultra-large laser power energy at the 10,000-watt level with milliwatt-level resolution. It has the advantages of real-time monitoring of the quality of the output beam, 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 ​​fast mirror adaptive compensation to solve the distortion problem of the interference pattern. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0085] Figure 1 The schematic diagram of the ultra-large laser power detection system based on vortex light interferometry measured by a torsion balance.

[0086] Figure 2 This is a 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 those skilled in the art 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 the art.

[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 1 to be measured, 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, the reflector B4 is installed on one side of the torsion scale 6, 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 interference 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 is incident on the reflector B4 through the reflector A2, and then is emitted for subsequent laser processing after the optical path is calibrated by the fast mirror A3. The reflector B4 and the reflector C5 located on both sides of the torsion balance are displaced in opposite directions and equidistantly. The light beam emitted by the measuring laser 8 is sequentially passed through the beam expansion and collimation system 9, the 1 / 4 wave plate 10, and the vortex wave plate 11 to form a vortex light, which is then split by the beam splitter A12 to form a test light and a reference light. The reference light reaches the photodetector 17 through the beam splitter C16. The test light reaches the fast mirror B7 through the beam splitter B13, and is then reflected back to the beam splitter B13 by the reflector C5 and the fast mirror B7, and sequentially passes through the Dove prism 14, the reflector D15, and the beam splitter C16 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 to obtain a petal-shaped interference pattern.

[0094] Reflector A, reflector B, reflector C and reflector D are all coated with high-reflection films.

[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-large 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 is incident on the reflector B4 through the reflector A2, and then is emitted after the light path is calibrated by the fast reflector A3. The light beam is incident on the reflector B4 to generate pressure, which converts the power of the laser to be tested into a light pressure value. The pressure causes displacement of the reflector B. The reflectors B and C located 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 with the 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, which 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, and reaches the photodetector 17 via the Dove prism 14, the reflector D15, and the beam splitter C16 in sequence. The reference light and the test light with the change in the optical path of the light beam of the reflector C at one end of the torsion beam interfere at the photodetector 17 to obtain a petal-shaped interference pattern of the vortex light;

[0100] The test beam carries the displacement information of the torsion balance reflector C, which is tilt-corrected by the fast mirror B. When the laser to be tested is running, the reflector C is displaced by the light pressure, which is reflected as the rotation of the angle of the petal-shaped interference pattern of the vortex light. By extracting the rotation angle of the petal-shaped interference pattern, the power energy of the ultra-high-power laser can be measured.

[0101] After the laser beam to be measured is emitted, it is emitted after passing through a power-light pressure conversion module for subsequent application; at the same time, the measurement of the laser power is converted into the measurement of the angle of rotation through a light pressure-displacement conversion module and a displacement-angle conversion module; the measurement of the angle size is realized through a vortex light interference module; the reference beam and the detection beam interfere at the photoelectric detector;

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

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

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

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

[0106] The present invention obtains the power information of the laser to be measured based on the principle of measuring micro-displacement by vortex light self-conjugate interference. The power of the laser to be measured is converted into a light pressure value, and the magnitude of the light pressure value is converted into a micro-displacement of the reflector B. The displacement of the reflector B causes the rotation of the torsion balance, thereby driving the displacement of the reflector C. Then, an angle rotation appears in the petal-shaped interference pattern of the vortex light, and the power of the laser to be measured is obtained by reverse deduction.

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

[0108] Although photons have no rest mass, they 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 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 force on the object. The relationship between the light pressure value F and the laser output power P is:

[0114]

[0115] Where, t is the 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 tested:

[0120] P = cF / 2ρcosβ (5).

[0121] The present invention uses two reflectors and a fast-reflecting mirror to realize the non-disturbance reversal of the optical path, and the subsequent application of the laser after emission is 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.

[0122] The system uses a torsion balance as a displacement transmission device. When the reflector B moves, not only is there displacement, but the reflector B itself also tilts at a small angle. This inclination angle can be adaptively compensated in real time through the fast reflection 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. Reflector B is installed on one side of the torsion beam balance and is displaced after the load-bearing light pressure changes. Reflector A is adjusted so that the light is incident on the center of reflector B, and the incident angle and exit angle become θ2. The fast reflector A adaptively corrects the deflection so that the light beam remains in the original direction to be emitted;

[0124] The torsion scale 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

[0125]

[0126] Where M is the torque of the torsion wire, is the torsion angle of the torsion wire. Since the torsion wire is fixedly connected to the scale bar, the deflection angle of the scale bar is The scale bar 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 bar are

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

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

[0129] The deflection angle γ of the scale 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] Among them, 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 interference uses the self-conjugate interference 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 are used as the input for data processing to obtain the displacement information.

[0146] In the vortex light self-conjugate interference, the most notable feature of the vortex beam is its spiral azimuthal phase structure. In order to facilitate the analysis of the subsequent displacement measurement method, 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 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 light intensity distribution can be expressed as:

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

[0158] It can be seen from formula (10) 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 the scope of protection of the present invention.

Claims

1. A super-large 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 scale and a micro-displacement measurement system based on vortex light self-conjugate interference, wherein the reflector B is installed on one side of the torsion scale, the reflector C is installed on the other side of the torsion scale, and the reflector C and the reflector B are symmetrically distributed relative to the torsion scale; The micro-displacement measurement system based on vortex light self-conjugate interference is located below the torsion balance, and includes a fast reflection mirror B, a measuring laser, a beam expansion and collimation system, a 1 / 4 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 tested 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 the 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 turn to form vortex light, which is split by the beam splitter A to form test light and reference light, and the reference light reaches the photoelectric detector 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, and passes through the Dove prism, reflector D, and beam splitter C in turn to reach the photoelectric detector. 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 photoelectric detector to obtain 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 HeNe laser with a wavelength of 633 nm was selected as the measurement laser.

4. A method for measuring a super-large laser power detection system based on vortex light interferometry of torsion balance measurement according to claim 1, characterized in that: include: After the laser to be tested emits a light beam, it is incident on the reflector B through the reflector A. After the light path is calibrated by the fast reflector A, the light beam is incident on the reflector B to generate pressure, which converts the power of the laser to be tested into a light pressure value. The pressure causes displacement of the reflector B. The reflectors B and C on both sides of the torsion scale make equidistant displacements in opposite directions. The torsion scale converts the tiny displacement into an angle change. By connecting it with the 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 is sequentially passed through the beam expansion and collimation system, 1 / 4 wave plate, and vortex wave plate 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 fast mirror B through beam splitter B, and is then reflected back to beam splitter B by reflector C and fast mirror B, and sequentially passes through Dove prism, reflector D, and beam splitter C 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 bar form interference at the photodetector to obtain a petal-shaped interference pattern of the vortex light. The power of the laser to be measured is obtained by reverse calculation through the angular rotation appearing in the petal-shaped interference pattern of the vortex light.

5. The method for measuring a super-large laser power detection system based on vortex light interferometry of torsion balance measurement according to claim 4 is 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=hv (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 matter, the momentum of the photons is transferred to the object, exerting force on the object. The relationship between the light pressure value F and the laser output power P is: Where, t is the 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 force 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 tested: P = cF / 2ρcosβ (5).

6. The method for measuring a super-large laser power detection system based on vortex light interferometry of torsion balance measurement according to claim 5 is 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. Reflector B is installed on one side of the torsion beam balance and is displaced after the load-bearing light pressure changes. Reflector A is adjusted so that the light is incident on the center of reflector B, and the incident angle and exit angle become θ2. The fast reflector A adaptively corrects the deflection so that the light beam remains in the original direction to be emitted; The torsion scale 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 torsion wire, is the torsion angle of the torsion wire. Since the torsion wire is fixedly connected to the scale bar, the deflection angle of the scale bar is The scale bar 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 bar are M1=Mb / (a+b) (7) M2=Ma / (a+b) (8) The deflection angle γ of the scale 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 the deflection angle of the torsion balance The relationship is The calculation formula of light pressure value F is: Among them, L represents the magnitude of the optical pressure moment; The calculation formula of micro displacement δ is: 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:

7. The method for measuring a super-large laser power detection system based on vortex light interferometry of torsion balance measurement according to claim 6 is characterized in that: The micro-displacement measurement system based on vortex light self-conjugate interference uses the self-conjugate interference of vortex light to measure the micro-displacement of the reflector C. In the self-conjugate interference of vortex light, the most significant feature of the vortex beam 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, 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 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; 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 light 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 displacement changes, 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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