A laser wavelength measurement optical path, measurement method and system

Abstract

This application discloses a laser wavelength measurement optical path, measurement method, and system. The measurement optical path includes an optical fiber, a parabolic mirror, a 45° beam splitter, a wedge, a cylindrical lens, and a linear array detector. Incident light becomes parallel light after passing through the optical fiber and parabolic mirror; after passing through the 45° beam splitter, interference fringes are formed on the wedge; the interference fringes converge to the linear array detector after passing through the 45° beam splitter and cylindrical lens. The wedge is first calibrated using a laser of known wavelength; during measurement, the calibration data is used to process the interference fringes of the laser to be measured to obtain the wavelength. Using multiple wedges of different heights for coordinated measurement can improve measurement accuracy. Thermal expansion and changes in air refractive index affect measurement accuracy; in high-precision wavelength measurement scenarios, wedges made of low-expansion materials must be used with temperature control, and the air refractive index must be calibrated in real time. The laser wavelength measurement optical path, measurement method, and system in this application can achieve wavelength measurement with MHz accuracy.

Description

Technical Field

[0001] This application relates to the field of laser wavelength measurement, and more specifically, to a laser wavelength measurement optical path, measurement method, and system. Background Technology

[0002] High-precision laser wavelength measurement technology is a key technology in modern precision measurement science, playing a vital role in multiple fields such as optics, physics, materials science, biomedicine, and precision manufacturing. High-precision laser measurement not only provides accurate data on laser wavelengths but is also crucial for understanding and controlling laser characteristics, significantly impacting the design of more precise optical systems, improving the performance of communication systems, and ensuring product quality in precision manufacturing and microelectronics. In recent years, laser application technologies have developed rapidly, particularly in precision measurement fields such as quantum communication, quantum control, quantum computing, cold atom physics, optical frequency standards, and atomic interferometers, leading to higher demands on the accuracy of laser wavelength measurement. Therefore, research on high-precision laser wavelength measurement methods and devices is essential. Summary of the Invention

[0003] To address the aforementioned technical problems, this application provides a laser wavelength measurement optical path, measurement method, and system, which achieves high-precision wavelength measurement through a combination of several wedges of different heights.

[0004] Specifically, the technical solution of this application is as follows:

[0005] In a first aspect, this application discloses a laser wavelength measurement optical path, comprising:

[0006] A parallel beam shaper, consisting of optical fibers and parabolic mirrors, is used to convert laser light into parallel light.

[0007] A 45° beam splitter is located on the path of the parallel beam exiting the beam and is used for beam splitting.

[0008] The wedge, located behind the 45° beam splitter, is used to receive the parallel laser and form interference fringes. The upper surface of the wedge is coated with a partially transmissive and partially reflective film, and the bottom surface is coated with a highly reflective film.

[0009] A cylindrical lens, located between the linear array detector and the 45° beam splitter, is used to focus light along the fringe direction;

[0010] The interference fringes pass sequentially through a 45° beam splitter and a cylindrical lens before converging onto a linear array detector for detection.

[0011] The wedge includes a first-stage wedge, a second-stage wedge, a third-stage wedge, etc. Wavelength measurement is performed by analyzing the interference fringe data generated by the wedge. The wedge is fixed on a low-expansion material substrate, and the substrate temperature is controllable to suppress the influence of thermal expansion on wavelength measurement.

[0012] The first-stage wedge tip must satisfy:

[0013] βk≤N; or βμ×λ / Δλ≤N×μ;

[0014] The second-order and third-order wedges should meet the following conditions:

[0015] β×2D 一级 / λ<N;

[0016] │2D 二级 / λ-2D 二级 / (λ±δλ 一级 )│<1;

[0017] │2D 三级 / λ-2D 三级 / (λ±δλ 二级 )│<1;

[0018] The fringe spacing generated by the wedges at each level in the corresponding optical path satisfies:

[0019] L=λ / (2sinθ)≤N×μ;

[0020] Where, k: fringe order; β: detector resolution coefficient; μ: detector pixel size; βμ: detector resolution limit, β ranges from 0 < β ≤ 1, β = 1 indicates the detector resolution limit is one pixel, system optimization can improve the resolution limit, in which case β < 1; N: number of detector pixels; Δλ: wavelength variation; λ: wavelength; δλ 一级 First-order wedge measurement uncertainty, δλ 二级 Second-order wedge measurement uncertainty, D 一级 First-stage wedge height; D 二级 Second-stage wedge height; D 三级 : Third-order wedge height; θ: wedge inclination angle, sinθ≈tanθ≈θ; L: fringe spacing.

[0021] The wavelength measurement uncertainty of each of the wedges is evaluated by the following formula:

[0022] δλ=βμ×2sinθ / k;

[0023] Where δλ: wavelength measurement uncertainty; k: fringe order.

[0024] Secondly, this application also discloses a laser wavelength measurement method, based on the wavelength measurement optical path described in any of the above embodiments, comprising the following steps:

[0025] The wedges were calibrated using lasers of known wavelengths to obtain data on the height of each wedge as a function of position, and these data were archived for future use.

[0026] When the laser to be tested is incident, interference fringes can be obtained by each wedge and its corresponding detector; by calling the calibration data, the interference fringes of the laser to be tested are processed to obtain the wavelength of the laser to be tested;

[0027] The wedge is fixed on a low-expansion material substrate, and the substrate is temperature-controlled. Environmental parameters are monitored in real time during calibration and measurement, and calibration and measurement data are corrected to improve the accuracy of wavelength measurement.

[0028] This application discloses a laser wavelength measurement method, wherein the method uses a laser of known wavelength to calibrate each level of wedge tip, and includes the following steps:

[0029] Establish a coordinate axis associated with the wedge position on the linear array detector, measure the interference fringes under laser light with wavelength λ0, and select a position x where the fringe is located. k Assuming the position to be calibrated corresponds to a fringe order of k; changing the laser wavelength to λ1 will cause the fringe to shift, and when x... k When the position coincides with a new fringe, the order of the new fringe is recorded as m; although k and m are unknown, the change in the fringe order is definite, that is, km is definite; by the interference condition, the position x can be obtained. k Corresponding wedge height D k ,as follows:

[0030] Dark Pattern: 2D k / λ0=k;

[0031] Glossy texture: 2D k / λ0=k-1 / 2;

[0032] Dark Pattern: 2D k / λ1=m;

[0033] Glossy texture: 2D k / λ1=m-1 / 2;

[0034] Δk = km;

[0035] λ0, λ1, and Δk are all definite quantities, from which the position x can be determined. k Corresponding wedge height D k ;

[0036] By changing the laser wavelength and selecting a new location, the above steps can be repeated to obtain data on different locations and their corresponding wedge heights. By fitting these data, the relationship curve between location and wedge height can be obtained.

[0037] In some implementations, when the laser wavelength used for calibration is limited in tuning and insufficient to cause the old and new interference fringes to coincide, or when the determination of fringe coincidence is limited, a second method can be used for calibration, with the following steps:

[0038] A coordinate axis associated with the wedge position is established on the linear array detector. Interference fringes are measured under laser light at wavelength λ0, and the positions x of each order of fringes are recorded. k x k+1 ...; Assume the wedge height corresponding to the fringe position is D. k D k+1 ...; Change the wavelength to λ1 and record the new positions x′ of each fringe level. k , x′ k+1 ...; Assume its corresponding wedge height is D′ k , D′ k+1 , ...;

[0039] sinθ=λ0 / 2(x k+1 -x k )=λ0 / 2(x k+2 -x k+1 )=……=λ1 / 2(x′ k+1 -x′ k )=λ1 / 2(x′ k+2 -x′ k+1 )=……=(D′ k -D k ) / (x′ k -x k )=(D′ k+1 -D k+1 ) / (x′ k+1 -x k+1 = ...;

[0040] Due to the dark pattern condition: 2D k / λ0=2D′ k / λ1=k;

[0041] We get: k = [2(x′)] k -x k [sinθ / (λ1-λ0)];

[0042] Or based on the luminous texture condition: 2D k / λ0=2D′ k / λ1=k-1 / 2;

[0043] We get: k = [2(x′)]k -x k [sinθ / (λ1-λ0)+1 / 2];

[0044] Where sinθ is an intermediate quantity that does not need to be actually solved; [...] indicates rounding (the same applies below);

[0045] Once the fringe order k is determined, the wedge height corresponding to each fringe position can be obtained, as follows:

[0046] Dark pattern: D k =kλ0 / 2,D k+1 = (k+1)λ0 / 2, ..., D′ k =kλ1 / 2,D′ k+1 = (k+1)λ1 / 2, ...;

[0047] Glossy texture: D k =(k-1 / 2)λ0 / 2, D k+1 =(k+1-1 / 2)λ0 / 2,…,D′ k =(k-1 / 2)λ1 / 2,D′ k+1 = (k+1-1 / 2)λ1 / 2, ...;

[0048] By repeating the above steps under different wavelength conditions, we can obtain wedge height data corresponding to different position coordinates. By fitting these data, we can obtain the relationship curve between position coordinates and corresponding wedge heights.

[0049] The laser wavelength measurement method disclosed in this application further includes: obtaining the wavelength value to be measured through a first-stage wedge, specifically including the following steps:

[0050] When a laser of the desired wavelength is incident, interference fringes will be measured at the first-order wedge. The position of the fringes is x. k x k+1 ...; and the corresponding wedge height D is obtained from the coordinate curve of the first wedge. k D k+1 , ...;

[0051] λ 测0 =2(D k+1 -D k )=2(D k+2 -D k+1 ), λ 测0 This is a rough measurement of the wavelength being measured;

[0052] Dark patterns: k = [2D k / λ 测0 ],k+1=[2D k+1 / λ 测0 ], ...;

[0053] Bright ripples: k = [2D k / λ 测0 +1 / 2],k+1=[2D k+1 / λ 测0 +1 / 2],……;

[0054] Dark pattern: λ 测1 =2D k / k=2D k+1 / (k+1)=……;

[0055] Glossy texture: λ 测1 =2D k / (k-1 / 2)=2D k+1 / (k+1-1 / 2)=……;

[0056] The above equation outputs λ. 测0 and λ 测1 Before obtaining the results, an average value can be taken to reduce the error; λ 测0 The relative uncertainty limit is 1 / N, where N is the number of pixels in the detector; λ 测1 The relative uncertainty limit is μ1×2sinθ1 / k, where θ1 and μ1 are the apex angle of the first-stage wedge and the detector pixel size corresponding to the wedge, respectively.

[0057] In some embodiments, the laser wavelength measurement method further includes: obtaining the wavelength value to be measured through a second-stage wedge, specifically including the following steps:

[0058] When a laser of the wavelength to be measured is incident, interference fringes are measured by the first-order and second-order wedges. The measurement data obtained by the first-order wedge is processed according to the steps described in the above embodiment to obtain the wavelength measurement value λ. 测1 ;

[0059] The interference fringes of the second-order wedge are located at x. K x K+1 ...; and the corresponding wedge height D is obtained from the calibration curve of the second-order wedge. K D K+1 , ...;

[0060] Dark pattern: K = [2D] K / λ 测1 ], K+1=[2D K+1 / λ 测1 ], ...;

[0061] Highlight: K = [2D] K / λ 测1 +1 / 2],K+1=[2D K+1 / λ 测1 +1 / 2],……;

[0062] Dark pattern: λ 测2 =2D K / K=2D K+1 / (K+1)=……;

[0063] Glossy texture: λ 测2 =2D K / (K-1 / 2)=2D K+1 / (K+1-1 / 2)=……;

[0064] The above equation outputs λ. 测2 Before obtaining the results, an average value can be taken to reduce the error; λ 测2 The relative uncertainty limit is μ2×2sinθ2 / K, where θ2 and μ2 are the second-order wedge apex angle and the corresponding detector pixel size, respectively.

[0065] In some embodiments, the laser wavelength measurement method further includes: obtaining the wavelength value to be measured through a third-order wedge, specifically including the following steps:

[0066] When the laser to be tested is incident, interference fringes will be measured at the first, second, and third order wedges. The fringes of the first and second order wedges are processed according to the steps described in the above embodiment to obtain the measured value λ. 测2 ;

[0067] The interference fringes of the third-order wedge are located at x. M x M+1 ...; and the corresponding wedge height D is obtained from the calibration curve of the third-order wedge. M D M+1 , ...;

[0068] Dark pattern: M = [2D M / λ 测2 ], M+1=[2D M+1 / λ 测2 ], ...;

[0069] Highlight: M = [2D] M / λ 测2 +1 / 2],M+1=[2D M+1 / λ 测2 +1 / 2],……;

[0070] Dark pattern: λ 测3 =2D M / M=2D M+1 / (M+1)=……;

[0071] Glossy texture: λ 测3 =2D M / (M-1 / 2)=2D M+1 / (M+1-1 / 2)=……;

[0072] The above equation outputs λ. 测3 Before obtaining the results, an average value can be taken to reduce the error; λ 测3 The relative uncertainty limit is μ3×2sinθ3 / K, where θ3 and μ3 are the third-order wedge apex angle and the corresponding detector pixel size, respectively.

[0073] Thirdly, this application also discloses a laser wavelength measurement system, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the laser wavelength measurement method described in any of the above embodiments.

[0074] Compared with the prior art, this application has at least one of the following beneficial effects:

[0075] First, a wavelength measurement optical path with a wavelength measurement accuracy of 0.0001 nm or better using a single wedge and detector is proposed, and a wavelength measurement optical path with a measurement accuracy of 0.001 pm using a multi-stage wedge and detector is also proposed, providing a technical solution for higher precision wavelength measurement.

[0076] Second, a wedge calibration scheme and a high-precision wavelength measurement method are proposed. During the calibration and measurement process, the wedge height (optical path is proportional to the wedge height) and fringe order are always anchored, and the fringe order is measured to be completely accurate without error. This allows the wedge height to be calibrated to a very high precision, eliminating measurement errors caused by other possible factors. This makes the wavelength measurement accuracy limited only by the resolution of the measuring device to the changes in interference fringes, thereby improving the accuracy of wavelength measurement.

[0077] Third, a detailed analysis of the uncertainty of the wavelength measurement results was conducted, the constraints that need to be met for high-precision wavelength measurement were determined, and the technical route of how to use the method described in this application to gradually improve the measurement accuracy using multiple wedges was explained, which has guiding significance for the design and development of high-precision wavelength measurement devices. Attached Figure Description

[0078] The preferred embodiments will now be described in a clear and easy-to-understand manner, in conjunction with the accompanying drawings, to further explain the above-mentioned characteristics, technical features, advantages, and implementation methods of this application.

[0079] Figure 1 This is a schematic diagram illustrating the principle of the laser wavelength measurement method of this application;

[0080] Figure 2 This is a schematic diagram of an embodiment of a laser wavelength measurement optical path disclosed in this application;

[0081] Figure 3This is a schematic diagram showing the displacement of the interference fringes;

[0082] Figure 4 This is a schematic diagram showing the displacement of interference fringes and their coincidence with the next order of fringes;

[0083] Figure 5 This is a schematic diagram of another embodiment of a laser wavelength measurement optical path disclosed in this application;

[0084] Figure 6 This is a schematic diagram of another embodiment of a laser wavelength measurement optical path disclosed in this application;

[0085] Figure 7 This is a flowchart illustrating the steps of an embodiment of a laser wavelength measurement method disclosed in this application;

[0086] Figure 8 In this embodiment of the application, the position x of the k-th level stripe is selected. k A schematic diagram;

[0087] Figure 9 This is a schematic diagram illustrating the left-right movement of the stripes in an embodiment of this application;

[0088] Figure 10 This is a fitted image of the detector pixel position and the wedge height at the corresponding position in one embodiment of a laser wavelength measurement method of this application;

[0089] Figure 11 This is a fitted image of the detector pixel position and the wedge height at the corresponding position in another embodiment of the laser wavelength measurement method of this application.

[0090] Figure label:

[0091] 10, wedge; 20, linear array detector; 30, interference fringe; 40, optical fiber; 50, parabolic mirror; 60, 45° beam splitter; 70, cylindrical lens; 11, first-order wedge; 12, second-order wedge; 13, third-order wedge; D, wedge height; H, wedge length; θ, wedge tilt angle. Detailed Implementation

[0092] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0093] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or sets.

[0094] To keep the drawings concise, each figure only schematically shows the parts relevant to the invention, and these do not represent the actual structure of the product. Furthermore, to facilitate understanding, in some figures, only one of components with the same structure or function is schematically depicted, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one."

[0095] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0096] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0097] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0098] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the specific implementation methods of this application will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without creative effort.

[0099] The laser wavelength measurement principle used in this application is as follows: Figure 1 As shown, the incident laser light enters from the upper surface of the wedge 10, and upon reflection from both the upper and lower surfaces of the wedge 10, interference fringes 30 are generated. These interference fringes 30 are received by the linear array detector 20. (Reference) Figure 1 Where D is the wedge height; H is the wedge length; and θ is the wedge inclination angle.

[0100] Optionally, in this application, λ is set as the wavelength of the incident laser; L is the spacing of the generated interference fringes; μ is the pixel size of the linear array detector; N is the number of pixels in the linear array detector; k is the fringe order of a certain interference fringe; x k This represents the position of the k-th order fringe. When the laser wavelength changes, the fringe spacing and fringe order will change, thus providing information about the laser wavelength and enabling accurate wavelength measurement.

[0101] This application discloses an embodiment of a laser wavelength measurement optical path, such as... Figure 2 As shown, it includes:

[0102] The parallel beam shaper consists of an optical fiber 40 and a parabolic mirror 50. The light outlet of the optical fiber 40 is located at the focal point of the parabolic mirror 50, which is used to convert the laser into parallel light.

[0103] A 45° beam splitter 60 is located on the path of the parallel beam output and is used to receive the laser and split it.

[0104] The first-stage wedge 11 is located behind the 45° beam splitter 60 and is used to receive the parallel laser. The upper surface of the wedge is coated with a partially transmissive and partially reflective film, and the bottom surface is coated with a highly reflective film. Interference fringes will be formed on the upper surface of the wedge.

[0105] After passing through a 45° beam splitter 60 and a cylindrical lens 70 in sequence, the interference fringes converge to a linear array detector 20, where the interference fringes 30 are detected by the linear array detector 20.

[0106] Wavelength measurements were performed by analyzing the interference fringe data generated by wedge 11.

[0107] To improve measurement accuracy, multiple sets of wedges of different heights are used to form an optical path. The wedge heights are named sequentially from low to high as first-level wedge, second-level wedge, third-level wedge, and so on. Each wedge constitutes an independent measurement optical path. The laser beam to be measured is split and passed through these measurement optical paths respectively, thereby progressively improving the wavelength measurement resolution and measurement accuracy.

[0108] The parameters of the wedge and linear array detectors should meet the following conditions:

[0109] (1) L=λ / (2sinθ)≤N×μ;

[0110] (2) D / sinθ≥βμ×λ / Δλ;

[0111] (3) βk≤N or βμ×λ / Δλ≤N×μ;

[0112] Where L is the spacing of the generated interference fringes; λ is the wavelength of the incident laser; θ is the wedge tilt angle; D is the wedge height; β is the resolution coefficient of the linear array detector; μ is the pixel size of the linear array detector; Δλ is the change in wavelength of the incident laser; N is the number of pixels in the linear array detector; and k is the fringe order of a certain interference fringe.

[0113] Formula (1) indicates that the linear array detector can detect at least one interference fringe.

[0114] Equation (2) indicates that for a change in wavelength Δλ, the movement of the interference fringes on the wedge must be at least greater than the minimum value that the detector can resolve, which is βμ.

[0115] Formula (3) means that the wavelength change Δλ causes the k±1 order stripe to overlap with the original k order stripe, and the detector can distinguish the difference between the old and new stripes.

[0116] The resolution coefficient β of the linear array detector described in formulas (2) and (3) can be a decimal, where βμ represents the minimum value of the interference fringe variation that the hardware and software involved in the detector can read and resolve.

[0117] Since θ is very small, sinθ≈tanθ≈θ. Choosing sinθ, tanθ or θ to express the formula does not affect the physical meaning of the formula or the meaning of the formula described in this application.

[0118] The physical meaning of formula (2) is that when the wavelength changes by a tiny amount Δλ, the interference fringes will shift slightly. The detector must be able to resolve this slight shift within the detection area to achieve high-precision wavelength measurement. Figure 3 As shown. Taking the slight rightward movement of the bright fringe as an example, using bright / dark fringe or rightward / leftward movement as an example does not affect the understanding of the physical meaning of formula (2).

[0119] The physical meaning of formula (3) is that when the wavelength changes by a small amount, causing the k+1 order / or k-1 order fringes of the new interference fringes to coincide with the k order fringes of the original interference fringes, and the adjacent two fringes of the two interference fringes coincide, the detector must be able to distinguish the difference between the new and old fringes within the detection area; otherwise, high-precision measurement cannot be achieved. Figure 4 As shown. Here, we take the example of the k-1 level bright fringe moving to the right and coinciding with the original k level bright fringe. The selection of bright or dark fringe and the selection of fringe level k±1 do not affect the understanding of the physical meaning of formula (3).

[0120] If the wavelength measurement accuracy requirement is not very high, a single wedge and detector combination may simultaneously satisfy the constraints described in formulas (2) and (3), that is, a single wedge and detector combination can complete the required wavelength measurement; however, when the wavelength measurement accuracy requirement is higher, a single wedge and detector combination cannot simultaneously satisfy the constraints described in formulas (2) and (3). In this case, multiple wedge and detector combinations are needed to satisfy one of the conditions described in formulas (2) or (3), that is, multiple wedge and detector combinations can jointly complete a higher precision wavelength measurement.

[0121] If two or more wedges are used together to perform high-precision wavelength measurements, the relationship between the wedges needs to meet additional conditions. We will denote the heights of the first-order wedge, the second-order wedge, ..., etc., as D. 一级 D 二级 D 三级 ..., etc.; Let the wavelength measurement uncertainty be denoted as δλ, then the conditions that each wedge must satisfy are:

[0122] (4)β×2D 一级 / λ<N;

[0123] │2D 二级 / λ-2D 二级 / (λ±δλ 一级 )│<1;

[0124] │2D 三级 / λ-2D 三级 / (λ±δλ 二级 )│<1;……; etc.

[0125] The physical meaning of equation (4) is as follows: the height of the first-order wedge must satisfy the constraint of equation (3); the wavelength measurement uncertainty of the first-order wedge cannot cause an error of ≥1 in the fringe order of the second-order wedge, that is, the wavelength accuracy measured by the first-order wedge is sufficient to determine the interference fringe order of the second-order wedge; the wavelength measurement uncertainty of the second-order wedge cannot cause an error of ≥1 in the fringe order of the third-order wedge, that is, the wavelength accuracy measured by the second-order wedge is sufficient to determine the interference fringe order of the third-order wedge; the conditions to be satisfied for higher-order wedges are deduced by analogy.

[0126] The wavelength measurement uncertainty of each order of wedge is evaluated by the following formula:

[0127] (5) δλ=βμ×2sinθ / k;

[0128] Where k is the fringe series corresponding to the wedge tip; sinθ is the sine corresponding to the inclination angle of the wedge tip. Since the inclination angle is very small, it can be approximated as sinθ≈tanθ≈θ, etc.

[0129] As shown in equation (5), as the wedge height increases, the fringe order also increases accordingly, and the measurement uncertainty decreases accordingly. By combining multiple wedge optical paths, high-precision wavelength measurement can be achieved.

[0130] Example 1 of a wavelength measurement optical path: This application discloses an embodiment of a laser wavelength measurement optical path, the optical structure of which is designed as follows. Figure 2 As shown, the laser wavelength measurement optical path only includes the first set of measurement optical paths.

[0131] It includes an optical fiber 40; a parabolic mirror 50; a 45° beam splitter 60; a first-order wedge 11; a cylindrical lens 70; and a linear array detector 20.

[0132] For example, the linear array detector has a spectral response range of 350nm-1100nm and a pixel size of 3.5um×16384, which means the pixel size μ=3.5um and the number of pixels N=16384.

[0133] This example uses only one first-stage wedge, designed with a height of 350 micrometers and an inclination angle of 0.0001 radians. The first-stage wedge is fabricated through the following steps: two circular glass plates are brought close together, and two quartz wires with a diameter of 350 micrometers are inserted into the gap between the two ends of the glass plates, forming a small included angle. Then, they are fixed by mechanical compression or chemical bonding.

[0134] As can be seen from the specifications of this embodiment, within the detector's spectral response range of 350nm-1100nm, the conditions L=λ / (2sinθ)≤N×μ and βk=β×2D / λ≤N (taking β=1) are all satisfied; the relative uncertainty limit that this embodiment can achieve for the measurement wavelength is:

[0135] E=δλ / λ=βμ×2sinθ / (λk)=μ×sinθ / D=1×10 -6 (Take β = 1);

[0136] The coefficient of thermal expansion of quartz is approximately 5.5 × 10⁻⁶. -7 / ℃ means that for a 1℃ change in temperature, the height of the wedge will increase by approximately 5×10⁻⁶. -7 Relative changes; temperature control of the wedge tip can be considered for stable and reliable wavelength measurements; temperature control can be performed on the side or bottom of the wedge tip, with a temperature control accuracy of 0.1℃, thus reducing the influence of thermal expansion to 5×10. -8 Much smaller than 1×10 -6 This can be considered as eliminating the influence of thermal expansion factors.

[0137] In some implementations, the two glass plates that make up the first-order wedge may not be circular.

[0138] In some implementations, cylindrical mirrors can be used instead of cylindrical lenses, requiring only a change in the position of the linear array detector.

[0139] In some embodiments, the tilt angle, height, and detector pixel specifications of the first-order wedge may differ from those set in this embodiment, but must meet the constraints described in this application. The measurement accuracy limit is determined by E=δλ / λ=βμ×2sinθ / (λk)~μ×sinθ / D.

[0140] In some embodiments, the quartz wire used to make the wedge can be replaced by a quartz sheet or other materials with low thermal expansion, including but not limited to ultra-low thermal expansion glass / ULE glass.

[0141] In some implementations, temperature control of the wedge tip may not be necessary, but the accuracy of wavelength measurement will be reduced.

[0142] Example 2 of wavelength measurement optical path: Another embodiment of the laser wavelength measurement optical path of this application, wherein the laser wavelength measurement optical path includes a first set of measurement optical paths and a second set of measurement optical paths.

[0143] Specifically, in the above-mentioned wavelength measurement optical path embodiment one ( Figure 2 Based on the previous one, a set of similar and relatively independent measurement optical paths were added, and their optical structures are as follows: Figure 5 As shown. Among them, Figure 2 The first-level wedge 11 and its corresponding linear array detector 20 are the same as those described in the above embodiments; the linear array detector 20 is the first linear array detector. Figure 5 The secondary wedge 12 is designed with a height of 35 mm and a wedge inclination angle of 0.0001 radians; the linear array detector 20 corresponding to the secondary wedge 12 is the second linear array detector, and its specifications are the same as those of the aforementioned first linear array detector.

[0144] In this embodiment, the secondary wedge can be fabricated through the following steps: a hollow base frame with a length of 35 mm is made using ultra-low thermal expansion glass / ULE glass, and the two circular glass pieces that constitute the wedge are fixed at both ends of the base frame, forming a small included angle.

[0145] As can be seen from the specifications of the wedges and detectors in this embodiment, the design height of the secondary wedge is 35 mm, which satisfies the |2D| requirement. 二级 / λ-2D 二级 / (λ±δλ 一级 The conditions described in 1 are met within the detector's spectral response range of 350nm-1100nm.

[0146] The relative uncertainty achievable for measuring the wavelength in this embodiment is:

[0147] E=δλ / λ=βμ×2sinθ / (λk)=μ 二级 ×sinθ 二级 / D 二级 =1×10 -8 (Take β = 1);

[0148] The coefficient of thermal expansion of ultra-low thermal expansion glass / ULE glass is generally 10. -8 / ℃, to achieve a relative uncertainty of 1×10 -8 For accurate wavelength measurements, temperature control of the wedge substrate is necessary. Setting the temperature control accuracy to 0.01℃ reduces the effect of thermal expansion to 1×10⁻⁶. -10 The effect of thermal expansion is considered to be eliminated.

[0149] In addition, environmental factors such as temperature, humidity, and pressure affect the air refractive index, thus influencing the uncertainty of wavelength measurement by approximately 1 × 10⁻⁶. -8 The order of magnitude, therefore, for a relative uncertainty of 1×10 -8 Accurate wavelength measurement also requires real-time monitoring of environmental conditions and correction of measurement results based on environmental parameters to ultimately achieve high-precision wavelength measurement. This application does not elaborate on how temperature, humidity, and pressure affect the air refractive index or how to eliminate or correct these effects.

[0150] In some implementations, the two glass plates that make up the secondary wedge may not be circular.

[0151] In some implementations, cylindrical mirrors can be used instead of cylindrical lenses, requiring only a change in the position of the linear array detector.

[0152] In some implementations, the ultra-low thermal expansion glass / ULE glass material used to fabricate the secondary wedge can be replaced with other low thermal expansion materials.

[0153] In some implementations, the tilt angle, height, and detector pixel specifications of the secondary wedge may differ from those set in this embodiment, as long as they satisfy |2D 二级 / λ-2D 二级 / (λ±δλ 一级 The conditions described above ()│<1 are sufficient to constrain the measurement. The final measurement accuracy limit is determined by E=δλ / λ~μ 二级 ×sinθ 二级 / D 二级 Decide.

[0154] Embodiment 3 of a wavelength measurement optical path: Another embodiment of a laser wavelength measurement optical path according to this application, wherein the laser wavelength measurement optical path includes a first set of measurement optical paths, a second set of measurement optical paths and a third set of measurement optical paths.

[0155] Specifically, based on the wavelength measurement optical path in Embodiment 2 described above, this embodiment adds a set of similar and relatively independent measurement optical paths, the optical structure of which is as follows: Figure 6 As shown. The first and second level wedges and their corresponding two linear array detectors are the same as those described in the above embodiment; the third level wedge 13 is designed with a height of 35 cm and a wedge tilt angle of 0.0001 radians; the linear array detector 20 corresponding to the third level wedge is the third linear array detector, and its specifications are the same as those of the aforementioned first or second linear array detector.

[0156] Specifically, Figure 2 The first set of measurement optical paths Figure 5 The second group of measurement optical paths, and Figure 6 In the third group of measurement optical paths, devices with the same markings have the same device format, but devices with the same markings in different optical paths are not the same. Optional, Figure 2 , Figure 5 , Figure 6 The linear array detector 20, interference fringes 30, optical fiber 40, parabolic reflector 50, 45° beam splitter 60, cylindrical lens 70, and other devices are in the same format as described in one embodiment of a laser wavelength measurement optical path disclosed in this application.

[0157] In this embodiment, the fabrication process of the third-level wedge is similar to that of the second-level wedge: a hollow base frame with a length of 35 cm is made using ultra-low thermal expansion glass / ULE glass, and the two circular glass pieces that constitute the wedge are fixed at both ends of the base frame, forming a small included angle.

[0158] As can be seen from the specifications of the wedges and detectors in this embodiment, the design height of the third-stage wedge is 35 cm, which satisfies the |2D| requirement. 三级 / λ-2D 三级 / (λ±δλ 二级 The conditions described in 1 are met within the detector's spectral response range of 350nm-1100nm.

[0159] The relative uncertainty achievable for measuring the wavelength in this embodiment is:

[0160] E=δλ / λ=βμ×2sinθ / (λk)=μ 三级 ×sinθ 三级 / D 三级 =1×10 -9 (Take β = 1);

[0161] To achieve a relative uncertainty of 1×10 -9For accurate wavelength measurement, the wedge-shaped substrate skeleton made of ultra-low thermal expansion glass / ULE glass material needs to be temperature controlled at the zero expansion point. The temperature control accuracy can be set to 0.01℃ or 0.001℃, so that the influence of thermal expansion effect on the uncertainty of wavelength measurement can be ignored.

[0162] In addition, to achieve a relative uncertainty of 1×10 -9 Accurate wavelength measurement also requires real-time monitoring of environmental factors such as temperature, humidity, and pressure, and correction of the measurement results based on environmental parameters in order to ultimately achieve high-precision wavelength measurement.

[0163] In some implementations, the two glass plates that make up the third wedge may not be circular.

[0164] In some implementations, cylindrical mirrors can be used instead of cylindrical lenses, requiring only a change in the position of the linear array detector.

[0165] In some implementations, the ultra-low thermal expansion glass / ULE glass material used to fabricate the third-order wedge tip can be replaced with other low thermal expansion materials.

[0166] In some implementations, the tilt angle, height, and detector pixel specifications of the third-order wedge may differ from those set in this embodiment, as long as they satisfy |2D 三级 / λ-2D 三级 / (λ±δλ 二级 The conditions described above ()│<1 are sufficient to constrain the measurement. The final measurement accuracy limit is determined by E=δλ / λ~μ 三级 ×sinθ 三级 / D 三级 Decide.

[0167] Although a preferred embodiment of the laser wavelength measurement optical path of this application has been described, those skilled in the art will understand the basic inventive concept of high-precision wavelength meter design from this application and may make other changes and modifications to these embodiments. These include, but are not limited to: continuing to increase the number of wedges; changing the height and angle parameters of each wedge; changing the specifications of each detector; and combining wedges and detectors with other different parameters for measurement, etc.

[0168] Based on the same concept, this application also discloses a method for measuring laser wavelength, wherein the method is applied to the laser wavelength measurement optical path described in any of the above embodiments, such as... Figure 7 As shown, the laser wavelength measurement method in this embodiment includes the following steps:

[0169] S100, wedge calibration: The wedge is calibrated using a laser of known wavelength to obtain data on the height of each wedge as a function of position, and the data are archived for future use.

[0170] S200, Wavelength Measurement: When a laser of the wavelength to be measured is incident, the linear array detectors of each wedge and its corresponding optical path can obtain the corresponding interference fringes; the archived calibration data is called up, and the obtained interference fringes of the laser to be measured are processed to obtain the wavelength of the laser to be measured.

[0171] Optionally, in this embodiment, the wedge is fixed on a low-expansion material substrate, and the wedge substrate is temperature-controlled. During the wedge calibration and wavelength measurement process, environmental parameters are monitored in real time, and the calibration data and measurement data are corrected to improve the accuracy of wavelength measurement.

[0172] This application discloses a method for measuring laser wavelength, in which two methods of wedge calibration can be selected according to the actual situation. Wavelength measurement also involves different steps, corresponding to wavelength measurement optical paths with varying numbers of wedges and different measurement accuracies.

[0173] One embodiment of the laser wavelength measurement method disclosed in this application includes the following "wedge calibration" step:

[0174] Establish a coordinate axis associated with the wedge position on the linear array detector, measure the interference fringes under a laser of known wavelength λ0, and select the position x of any fringe. k As a calibration position, and assuming the order of its corresponding fringe is k; by slowly changing the laser wavelength, the interference fringes will slowly shift. When the laser wavelength changes to λ1, the calibration position coincides with the position of a new fringe, and the order of the new fringe is recorded as m; although the orders k and m are unknown, the order of the fringe shift is determined, i.e., km can be determined by counting the fringe shifts; from the interference condition, the calibration position x can be obtained. k The corresponding wedge height D k Then, repeat the above steps at other locations for calibration. Fit the obtained wedge height data to obtain the curve showing the relationship between wedge height and location; this is the calibration result. Details are as follows:

[0175] Step 1: Establish a coordinate axis by using the linear array detector as part of the coordinate axis.

[0176] Step 2: Measure the interference fringes corresponding to the known wavelength λ0. Select the position x of one of the fringes. k Either light or dark stripes are acceptable, where k is the stripe level, and the value of k is unknown. Figure 8 As shown. Increasing or decreasing the wavelength of the laser will shift the stripes to the left or right, as... Figure 9 As shown.

[0177] When position x kThe point where the fringe overlaps with a certain fringe (either bright or dark) is recorded, along with the number of fringe movements Δk and the corresponding wavelength λ1. The position x at this point is then recorded. k The new fringe series at the location is denoted as m.

[0178] According to the interference condition, position x k The corresponding wedge height D k It should meet the following requirements:

[0179] (6)2D k / λ0=k(dark pattern) or 2D k / λ0=k-1 / 2(bright fringe);

[0180] (7)2D k / λ1=m(dark pattern) or 2D k / λ1=m-1 / 2(bright fringe);

[0181] (8) Δk = km;

[0182] In equations (6), (7), and (8) above, λ0, λ1, and Δk are known. The position x can be uniquely determined by solving the equations. k The corresponding wedge height D k .

[0183] Step 3: Change the laser wavelength and select a new location for calibration. This will yield a set of data on the wedge height at different locations. List this data as follows:

[0184] coordinate axis position x <![CDATA[x k ]]> <![CDATA[x i ]]> <![CDATA[x j ]]> <![CDATA[x l ]]> <![CDATA[x s ]]> <![CDATA[x p ]]> <![CDATA[x d ]]> <![CDATA[x f ]]> <![CDATA[x g ]]> <![CDATA[x h ]]> …… wedge height D <![CDATA[D k ]]> <![CDATA[D i ]]> <![CDATA[D j ]]> <![CDATA[D l ]]> <![CDATA[D s ]]> <![CDATA[D p ]]> <![CDATA[D d ]]> <![CDATA[D f ]]> <![CDATA[D g ]]> <![CDATA[D h ]]> ……

[0185] Step 4: Using x as the abscissa and D as the ordinate, fit the obtained position x and wedge height D data to obtain the wedge height corresponding to any abscissa on the linear array detector. For example... Figure 10 As shown.

[0186] The slope of the fitted image is related to the wedge angle θ, which represents the magnitude of sinθ, tanθ, or θ.

[0187] In some implementations, for position x k The corresponding wedge height D k The final D can be obtained by measuring multiple times using the above method, and then averaging or fitting the results. k value.

[0188] In some implementations, when selecting fringes, only bright fringes, only dark fringes, or both bright and dark fringes can be selected. However, it should be noted that the interference conditions corresponding to bright fringes and dark fringes are different.

[0189] More preferably, this embodiment involves determining the position of interference fringes. The fringe position information can be read from the detector or obtained through software fitting.

[0190] Another embodiment of the laser wavelength measurement method of this application specifically explains the second wedge calibration step. When the wavelength tuning of the laser used for wedge calibration is limited and insufficient to ensure that the new interference fringes coincide with the original interference fringes, or when the determination of interference fringe coincidence is limited, the second method can be used for wedge calibration. As follows:

[0191] A coordinate axis associated with the wedge position is established on the linear array detector. Interference fringes are measured under a laser of known wavelength λ0, and the positions x of each order of fringes are recorded. k x k+1 ...; and assume that the wedge height corresponding to the fringe position is D. k D k+1 ...; Change the wavelength to move the fringes. At this time, the wavelength is λ1, and record the new position x′ of each order of fringes. k , x′ k+1 ...; and assume that the corresponding wedge height is D′ k , D′ k+1 ...; the x values ​​at different positions can be obtained from the interference conditions. k x k+1 , ..., x′k, x′k +1 ...the corresponding wedge height D k D k+1 , ..., D′ k , D′ k+1 Then, change the laser wavelength, select other locations, and repeat the calibration steps. Fit the obtained wedge height data to obtain the curve showing the relationship between wedge height and location; this is the calibration result. The specific steps are as follows:

[0192] Step 1: Establish a coordinate axis by including the linear array detector as part of the coordinate axis;

[0193] Step 2: Inject a laser beam with a known wavelength λ0, measure the interference fringes, and record the positions x of each order of fringes. k x k+1 ...; and assume that the wedge height corresponding to the fringe position is D. k D k+1 , ...;

[0194] Step 3: Change the wavelength to move the fringes. Carefully observe the fringes from Step 2 as they move to their new positions, and record the new positions x′k for each fringe. +1 ...; and assume that the corresponding wedge height is D′ k , D′ k+1, ...; at the same time, record the wavelength λ1 at this time;

[0195] Step 4: Based on the wedge interference condition, the formula is as follows:

[0196] (9) sinθ=λ0 / 2(x k+1 -x k )=λ0 / 2(x k+2 -x k+1 )=……=λ1 / 2(x′ k+1 -x′ k )=λ1 / 2(x′ k+2 -x′ k+1 )=……=(D′ k -D k ) / (x′ k -x k )=(D′ k+1 -D k+1 ) / (x′ k+1 -x k+1 = ...;

[0197] (10)2D k / λ0=2D′ k / λ1=k(dark pattern);

[0198] 2D k / λ0=2D′ k / λ1=k-1 / 2(bright fringe);

[0199] (11)k=[2(x′ k -x k [sinθ / (λ1-λ0)](dark fringes);

[0200] k=[2(x′ k -x k )sinθ / (λ1-λ0)+1 / 2] (bright pattern);

[0201] Where [] indicates taking integers, sinθ is only used as an intermediate quantity and does not need to be actually solved. The stripe series k can be obtained from the above formula, and then the wedge height corresponding to different positions can be obtained:

[0202] (12)D k =kλ0 / 2,D k+1 = (k+1)λ0 / 2, ..., D′ k =kλ1 / 2,D′ k+1 = (k+1)λ1 / 2, ... (dark patterns);

[0203] D k =(k-1 / 2)λ0 / 2, D k+1=(k+1-1 / 2)λ0 / 2,…,D′ k =(k-1 / 2)λ1 / 2,D′ k+1 = (k+1-1 / 2)λ1 / 2, ... (bright fringes);

[0204] Step 5: Change the laser wavelength and select other locations for calibration. The resulting data is listed below:

[0205] coordinate axis position x <![CDATA[x k ]]> <![CDATA[x k+1 ]]> <![CDATA[x k+2 ]]> …… <![CDATA[x′ k ]]> <![CDATA[x′ k+1 ]]> <![CDATA[x′ k+2 ]]> …… wedge height D <![CDATA[D k ]]> <![CDATA[D k+1 ]]> <![CDATA[D k+2 ]]> …… <![CDATA[D′ k ]]> <![CDATA[D′ k+1 ]]> <![CDATA[D′ k+2 ]]> ……

[0206] Step 6: Fit the data obtained in Step 5 to obtain the wedge height corresponding to any position on the detector. For example... Figure 11 As shown. The slope of the fitted curve is related to the wedge angle θ, representing the magnitude of sinθ, tanθ, or θ.

[0207] In some implementations, when selecting fringes, only bright fringes, only dark fringes, or both bright and dark fringes can be selected. However, it should be noted that the interference conditions corresponding to bright fringes and dark fringes are different.

[0208] Specifically, the location of interference fringes can be determined by reading from the detector or by software fitting or processing.

[0209] In the two embodiments of wedge calibration described above, the resulting fitted curve should be a straight line in most cases, and the slope of the line is related to the wedge tilt angle θ. However, there are some situations where the fitted curve is not a strictly straight line. For example, the wedge tilt angle may change slightly at a certain point due to manufacturing precision. Since this application always anchors the wedge height corresponding to the fringe position (which has a strictly linear relationship with the optical path) during calibration and measurement, the wedge tilt angle is only used as an intermediate quantity in the calculation process. Even if there is a sudden change in the wedge tilt angle, it will not affect the calibration or measurement accuracy of this application.

[0210] Another embodiment of the laser wavelength measurement method disclosed in this application will explain the steps of "wavelength measurement" in detail. Wedge calibration must be completed before wavelength measurement; therefore, the following wavelength measurement steps assume that the wedge calibration data has been obtained and archived for future use. This embodiment corresponds to the case with only one wedge, or the use of only one first-order wedge for measurement and output of measurement results. The wavelength measurement steps are as follows:

[0211] When a laser with a wavelength of λ is input, the first-order wedge and its corresponding linear array detector 1 will measure a set of interference fringes. The position x of the fringes is recorded. k x k+1 ...; and the wedge height D corresponding to the fringe position is obtained from the calibration curve of the first-order wedge. k D k+1 , ...;

[0212] The coarse measurement value of the wavelength to be measured is denoted as λ. 测0 According to the interference condition, λ 测0 It can be determined by the following formula:

[0213] (13)λ 测0 =2(D k+1 -D k )=2(D k+2 -D k+1 = ...;

[0214] At the same time, λ 测0 The relative uncertainty of the measurement is determined by the following formula:

[0215] (14)δλ 测0 / λ 测0 ≈1 / N, where N is the number of pixels in the linear array detector;

[0216] The coarse measurement value λ 测0 Substitute the values ​​to determine the order of the interference fringes for the wavelength to be measured, as follows:

[0217] (15)k=[2D k / λ 测0 ],k+1=[2D k+1 / λ 测0 ], ... (dark pattern);

[0218] k = [2D k / λ 测0 +1 / 2],k+1=[2D k+1 / λ 测0 +1 / 2],……(bright lines);

[0219] [] indicates taking the integer part;

[0220] The wavelength measurement result corresponding to the first-order wedge is:

[0221] (16)λ 测1 =2D k / k=2D k+1 / (k+1)=……(dark pattern);

[0222] λ 测1 =2D k / (k-1 / 2)=2D k+1 / (k+1-1 / 2)=……(bright fringe);

[0223] (17)δλ 测1 / λ 测1 ≈μ1×2sinθ1 / (λ 测1 ×k);

[0224] Where θ1 and μ1 are the apex angle of the first-order wedge and the pixel size of the linear array detector corresponding to the wedge, respectively, and k is the fringe order corresponding to the first-order wedge.

[0225] For a first-order wedge with an inclination angle of 0.0001 radians and a height of 350 micrometers, and a linear array detector with a pixel size of 3.5 micrometers and a number of 16384 pixels, the relative uncertainty of wavelength measurement achievable with a first-order wedge is E-6.

[0226] In some embodiments, the stripes can be selected as bright stripes or dark stripes, or bright and dark stripes can be recorded simultaneously; for the sake of simplicity, this application will not go into detail, and those skilled in the art can deduce it themselves based on the relevant content of this application;

[0227] In some implementations, equations (13) and (16) output λ 测0 and λ 测1 Before obtaining the results, an average value can be taken to make full use of the measurement data and reduce errors.

[0228] Another embodiment of the laser wavelength measurement method disclosed in this application will explain in detail the wavelength measurement steps in the case of multiple wedges working together. This method is suitable for applications requiring high wavelength measurement accuracy. The wavelength measurement optical path needs to include multiple wedges and corresponding linear array detectors, and the prerequisite for measurement is still the completion of wedge calibration. Taking a wavelength measurement device containing three wedges as an example, the specific steps are as follows:

[0229] Step 1: Input a laser with a wavelength of λ to be measured. Each wedge and its corresponding detector will obtain the corresponding interference fringe data; record the position x of the interference fringes obtained by the first-order wedge and its corresponding linear array detector 1. k x k+1 ...; and the corresponding wedge height D is obtained from the calibration curve of the first-order wedge. k D k+1 ...; Record the position x' of the interference fringes obtained by the second-order wedge and its corresponding linear array detector 2. m , x' m+1 ...; and the corresponding wedge height D' is obtained from the calibration curve of the second-order wedge. m ,D' m+1 ...; Record the positions of the interference fringes x obtained by the third-order wedge and its corresponding linear array detector 3. n ,x” n+1 ...; and the corresponding wedge height D is obtained from the calibration curve of the third-order wedge. n D” n+1 , ...;

[0230] Step 2: Obtain λ using the data obtained from the first-stage wedge and its corresponding linear array detector 1. 测1The details of this step are as shown in the previous embodiment: First, the coarse measurement value λ of the wavelength to be measured is obtained from the interference fringes. 测0 ; Use wavelength to roughly measure λ 测0 Determine the order of the interference fringes corresponding to the first-order wedge; then use the wedge height and fringe order to obtain the wavelength measurement result λ corresponding to the first-order wedge. 测1 ;

[0231] Step 3: Measure the wavelength λ corresponding to the first-stage wedge. 测1 Based on the interference fringe data corresponding to the second-order wedge, the order of the interference fringes corresponding to the second-order wedge is determined as follows:

[0232] (18)m=[2D' m / λ 测1 ],m+1=[2D' m+1 / λ 测1 ], ... (dark pattern);

[0233] m = [2D' m / λ 测1 +1 / 2],m+1=[2D' m+1 / λ 测1 +1 / 2],……(bright lines);

[0234] [] indicates taking the integer part;

[0235] The wavelength measurement result corresponding to the second-order wedge is:

[0236] (19)λ 测2 =2D' m / m=2D' m+1 / (m+1)=……(dark pattern);

[0237] λ 测2 =2D' m / (m-1 / 2)=2D' m+1 / (m+1-1 / 2)=……(bright fringe);

[0238] (20)δλ 测2 / λ 测2 ≈μ2×2sinθ2 / (λ 测2 ×m);

[0239] Where θ2 and μ2 are the apex angle of the second-order wedge and the pixel size of the linear array detector 2 corresponding to the wedge, respectively, and m is the fringe order corresponding to the second-order wedge.

[0240] Step 4: Measure the wavelength λ corresponding to the second-order wedge. 测2 Based on the interference fringe data corresponding to the third-order wedge, the order of the interference fringes corresponding to the third-order wedge is determined as follows:

[0241] (21)n=[2D” n / λ 测2 ],n+1=[2D” n+1 / λ 测2 ], ... (dark pattern);

[0242] n = [2D” n / λ 测2 +1 / 2],n+1=[2D” n+1 / λ 测2 +1 / 2],……(bright lines);

[0243] [] indicates taking the integer part;

[0244] The wavelength measurement result corresponding to the third-order wedge is:

[0245] (22)λ 测3 =2D” n / n=2D” n+1 / (n+1)=……(dark pattern);

[0246] λ 测3 =2D” n / (n-1 / 2)=2D” n+1 / (n+1-1 / 2)=……(bright fringe);

[0247] (23)δλ 测3 / λ 测3 ≈μ3×2sinθ3 / (λ 测3 ×n);

[0248] Where θ3 and μ3 are the apex angle of the third-order wedge and the pixel size of the linear array detector 3 corresponding to the wedge, respectively, and n is the fringe order corresponding to the third-order wedge.

[0249] In some embodiments, the stripes can be selected as bright stripes or dark stripes, or bright and dark stripes can be recorded simultaneously; for the sake of simplicity, this application will not go into detail, and those skilled in the art can deduce it themselves based on the relevant content of this application;

[0250] In some implementations, equations (19) and (22) output λ. 测2 and λ 测3 Before obtaining the results, an average value can be taken to make full use of the measurement data and reduce errors.

[0251] For a second-order wedge with an inclination angle of 0.0001 radians and a height of 35 millimeters, and with the linear array detector 2 having dimensions of 3.5 micrometers × 16384, the relative uncertainty of wavelength measurement achievable by combining the second-order wedge with the aforementioned first-order wedge is E-8. For a third-order wedge with an inclination angle of 0.0001 radians and a height of 35 centimeters, and with the linear array detector 3 having dimensions of 3.5 micrometers × 16384, the relative uncertainty of wavelength measurement achievable by combining the third-order wedge with the aforementioned first-order and second-order wedges is E-9. Thus, for a single-frequency laser with a wavelength of 780 nm, the achievable measurement accuracy is 0.0008 pm.

[0252] In some implementations, the wavelength measurement device includes more than three wedges and corresponding detectors, in which case the measurement result λ from the third wedge needs to be used. 测3 The order of the fourth-order wedge fringe is determined, and the wavelength measurement result λ of the fourth-order wedge is obtained according to the aforementioned steps and interference conditions. 测4 For cases with more wedges and detectors, the process can be repeated sequentially until the wavelength measurement value is finally obtained.

[0253] Based on the same concept, this application also discloses a laser wavelength measurement system, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the software program to implement the steps of the laser wavelength measurement method described in any of the above embodiments.

[0254] Specifically, one embodiment of a laser wavelength measurement system includes: a data acquisition module, a wedge calibration module, a storage module, a wavelength measurement module, and a display module.

[0255] The data acquisition module is used to collect interference fringe data from each linear array detector and transmit it to a computer for data archiving and processing.

[0256] The wedge calibration module is used to calibrate each wedge using a laser of known wavelength, and obtain calibration data for each level of the wedge.

[0257] The storage module is used to sequentially save the calibration data of each wedge for later retrieval; it is also used to save historical wavelength measurement data for monitoring and analyzing changes in the measured wavelength over a period of time.

[0258] The wavelength measurement module is used to analyze the measured interference fringes under the incident condition of the wavelength to be measured, call up the archived wedge calibration data, obtain the wavelength value to be measured, and output the uncertainty of the wavelength measurement.

[0259] The display module is used for human-computer interaction and display of wavelength measurement results. There are a series of scenarios that require human-computer interaction during calibration and measurement. When the measurement is completed, the measurement results also need to be displayed.

[0260] In some implementations, the display module's functionality is provided by the wavelength measurement software interface, and the computer communicates with the linear array detector in real time. All data acquisition, processing, feedback, and display are completed on the computer.

[0261] In some implementations, hardware and software related to data acquisition and processing are integrated within a mobile display module, and the related data acquisition, processing, feedback, and display are all completed on this mobile display module; this mobile display module is equivalent to a dedicated display screen and a dedicated processor.

[0262] The laser wavelength measurement optical path, measurement method and system of this application have the same technical concept, and the technical details of the embodiments of the three are applicable to each other. In order to reduce repetition, they will not be described again here.

[0263] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of program modules is merely an example. In practical applications, the above functions can be assigned to different program modules as needed, that is, the internal structure of the device can be divided into different program units or modules to complete all or part of the functions described above. The program modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one processing unit. The integrated unit can be implemented in hardware or as a software program unit. Furthermore, the specific names of the program modules are only for easy differentiation and are not intended to limit the scope of protection of this application.

[0264] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0265] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A laser wavelength measurement optical path, characterized by, Comprise: Parallel light beam shaper, composed of optical fiber and parabolic mirror, for changing laser into parallel light; 45° beam splitter, located in the parallel light beam exit light path, for splitting light; Cleaved tip, located behind the 45° beam splitter, for receiving the parallel light and forming interference fringes, the upper surface of the cleaved tip is coated with partially transmissive and partially reflective film and the bottom surface is coated with high reflective film; Cylindrical lens, located between the linear array detector and the 45° beam splitter, for focusing light along the direction of the fringes; After the interference fringes pass through the 45° beam splitter and the cylindrical lens in turn, they are converged to the linear array detector for detection; The cleaved tip comprises: a first-stage cleaved tip, a second-stage cleaved tip, and a third-stage cleaved tip; each cleaved tip independently constitutes a set of measurement light paths; wavelength measurement is performed by analyzing the interference fringe data generated by the cleaved tip; the cleaved tip is fixed on a low-expansion material base, and the temperature of the base is controllable to suppress the influence of thermal expansion on wavelength measurement; The first-stage cleaved tip needs to satisfy: βk≤N; or βμ×λ / Δλ≤N×μ; The second-stage cleaved tip and the third-stage cleaved tip should satisfy the condition: β x 2D 一级 / λ < N; | 2D 二级 / λ - 2D 二级 / (λ ± δλ 一级 ) | < 1; | 2D 三级 / λ - 2D 三级 / (λ ± δλ 二级 ) | < 1; The fringe spacing generated by each stage of the cleaved tip in the corresponding light path satisfies: L = λ / (2sinθ) ≤ N × μ; wherein k: fringe order; β: detector resolution coefficient; μ: detector pixel size; βμ: detector resolution limit, β value range 0 < β ≤ 1, β = 1 represents that the detector resolution limit is one pixel, system optimization can improve the resolution limit, at this time the corresponding β < 1; N: number of detector pixels; Δλ: wavelength variation; λ: wavelength; δλ 一级 : first-order wedge tip measurement uncertainty, δλ 二级 : second-order wedge tip measurement uncertainty, D 一级 : first-order wedge tip height; D 二级 : second-order wedge tip height; D 三级 : third-order wedge tip height; θ: wedge tip inclination angle, sinθ ≈ tanθ ≈ θ; L: fringe spacing; The corresponding wavelength measurement uncertainty of each stage of the cleaved tip is evaluated by the following formula: δλ = βμ×2sinθ / k; Wherein, δλ: wavelength measurement uncertainty; k: fringe order.

2. A method of measuring a wavelength of a laser, characterized by, Based on the wavelength measurement light path of claim 1, comprising the following steps: Use a laser with a known wavelength to calibrate the cleaved tip, respectively obtain the data of the height of each stage of the cleaved tip varying with position, and archive them for later use; Incident on the laser to be measured, each stage of the cleaved tip and its corresponding detector can respectively obtain interference fringes; call the calibration data to process the interference fringes of the laser to be measured, and obtain the wavelength of the laser to be measured; The cleaved tip is fixed on a low-expansion material base, and the base is temperature-controlled to monitor the environmental parameters in real time during calibration and measurement, and correct the calibration and measurement data to improve the accuracy of wavelength measurement.

3. A method of measuring the wavelength of a laser as claimed in claim 2, wherein, The use of a laser with a known wavelength to calibrate each stage of the cleaved tip comprises the following steps: A coordinate axis associated with the position of the wedge tip is established on the array detector, and the interference fringes are measured under laser light of wavelength λ0, and a position x where a fringe is located is selected k As the position to be calibrated, it is assumed that the number of fringes corresponding to the position is k; the wavelength of the laser light is changed to λ1, and the fringes are moved, and when x k When the position coincides with that of a new fringe, the number of the new fringe is recorded as m; although k and m are unknown, the change Δk in the number of fringes is determined, that is, k-m is determined; from the interference condition, the position x k The corresponding wedge tip height D k As follows: Dark lines: 2D k / λ0= k; Lei: 2D k / λ0= k-1 / 2; Dark lines: 2D k / λ1 = m; Lei: 2D k / λ1 = m - 1 / 2; Δk = k - m; λ0, λ1 and Δk are all determined quantities, from which the position x can be determined k corresponding cleft tip height D k ; Change the wavelength of the laser, select a new position and repeat the above steps to obtain the data of the height of the cleaved tip at different positions, and fit these data to obtain the relationship curve between position and height of the cleaved tip.

4. A method of measuring the wavelength of a laser as claimed in claim 3, wherein, When the laser wavelength used for calibration is limited and insufficient to cause the old and new interference fringes to coincide, or the determination of the coincidence of the fringes is limited, the second method can be used to calibrate the cleaved tip, and the steps are as follows: A coordinate axis associated with the wedge position is established on the array detector, the interference fringes are measured under the laser of wavelength λ0, and the positions x of the levels of fringes are recorded k , x k+1 , …; it is assumed that the corresponding wedge height at the fringe position is D k , D k+1 , …; the wavelength is changed to λ1, and the new positions x' of the levels of fringes are recorded k , x' k+1 , …; it is assumed that the corresponding wedge height is D' k , D' k+1 , … sin θ = λ0 / 2(x k+1 -x k ) = λ0 / 2(x k+2 -x k+1 ) =... = λ1 / 2(x' k+1 -x' k ) = λ1 / 2(x' k+2 -x' k+1 ) =... = (D' k -D k ) / (x' k -x k ) = (D' k+1 -D k+1 ) / (x' k+1 -x k+1 ) =... From the dark condition: 2D k / λ0= 2D' k / λ1= k; get: k=[2(x′ k -x k )sinθ / (λ1-λ0)]; or by the bright fringe condition: 2D k / λ0= 2D' k / λ1= k - 1 / 2; Result: k = [2(x' - x0) sin θ / (λ1- λ0) + 1 / 2]; where x0= 0.5λ0, and x' = 0.5λ1. k - x k ) sin θ / (λ1- λ0) Wherein, sinθ is an intermediate quantity that does not need to be actually solved; [...] represents rounding; After determining the fringe order k, the height of the cleaved tip corresponding to each fringe position can be obtained as follows: Dark lines: D k = kλ0 / 2, D k+1 = (k + 1)λ0 / 2,..., D' k = kλ1 / 2, D' k+1 = (k + 1)λ1 / 2,...; Bright fringe: D k = (k - 1 / 2) λ0 / 2, D k+1 = (k + 1 - 1 / 2) λ0 / 2, D' k = (k - 1 / 2) λ1 / 2, D' k+1 = (k + 1 - 1 / 2) λ1 / 2,...; Repeat the above steps under different wavelength conditions to obtain the height data of the cleaved tip corresponding to different position coordinates, and fit these data to obtain the relationship curve between the position coordinates and the corresponding height of the cleaved tip.

5. A method of measuring the wavelength of a laser as claimed in claim 4, wherein, Further comprising: The wavelength value λ to be measured is obtained by the first wedge 测1 and specifically comprises the following steps: The laser of the wavelength to be measured is incident, and the first split tip measures the interference fringes, and the fringe position x k , x k+1 , …; and the corresponding split tip height D k , D k+1 , …; is obtained from the coordinate curve of the first split tip. λ 测0 = 2(D k+1 − D k ) = 2(D k+2 − D k+1 ), λ 测0 is a coarse measurement of the measured wavelength; Dark lines: k = [2D k / λ 测0 ], k + 1 = [2D k+1 / λ 测0 ],...; Bright fringe: k = [2D k / λ 测0 + 1 / 2], k + 1 = [2D k+1 / λ 测0 + 1 / 2],...; Dark lines: λ 测1 = 2D k / k = 2D k+1 / (k + 1) =...; Bright fringe: λ 测1 = 2D k = 2D k+1 = 2D The results of λ 测0 and λ 测1 are averaged before outputted, to reduce error; the relative uncertainty limit of λ 测0 is 1 / N, N is the number of pixels of the detector; the relative uncertainty limit of λ 测1 is μ1×2sinθ1 / k, θ1 and μ1 are the top angle of the first split tip and the pixel size corresponding to the split tip, respectively.

6. A method of measuring the wavelength of a laser as claimed in claim 5, wherein, Further comprising: The second order wedge gives the value of the wavelength λ to be measured 测2 and comprises the following steps: The laser of the wavelength to be measured is incident, and the first and second split tips measure interference fringes, wherein the measurement data obtained by the first split tip are processed according to claim 5 to obtain the wavelength measurement value λ 测1 ; The interference fringe position of the second-order wedge tip is x K , x K+1 , …; and the corresponding wedge tip height D K , D K+1 , … is obtained from the calibration curve of the second-order wedge tip Dark lines: K = [2D K / λ 测1 ], K + 1 = [2D K+1 / λ 测1 ],...; Bright fringe: K = [2D K / λ 测1 + 1 / 2], K + 1 = [2D K+1 / λ 测1 + 1 / 2],...; Dark lines: λ 测2 = 2D K = 2D K+1 = 2D Levogyre: λ 测2 = 2D K = 2D K+1 = 2D Wherein, K, K+1 are the interference fringe orders of the second-stage cleaved tip; The above equation outputs λ. 测2 Before obtaining the results, an average value can be taken to reduce the error; λ 测2 The relative uncertainty limit is μ2×2sinθ2 / K, where θ2 and μ2 are the second-order wedge apex angle and the corresponding detector pixel size, respectively.

7. A method of measuring the wavelength of a laser as claimed in claim 6, wherein, Further comprising: The wavelength value λ to be measured is obtained by the third-order wedge 测3 and specifically includes the following steps: The first-order, second-order and third-order split tips will measure interference fringes when the laser to be measured is incident, wherein the fringes of the first-order and second-order split tips are processed according to claims 5-6 to obtain the wavelength measurement value λ 测2 ; The interference fringe position of the third-order wedge tip is x M , x M+1 , …; and the corresponding wedge tip height obtained from the calibration curve of the third-order wedge tip is D M , D M+1 , …; Dark lines: M = [2D M / λ 测2 ], M+1 = [2D M+1 / λ 测2 ],...; Bright fringe: M = [2D M / λ 测2 + 1 / 2], M + 1 = [2D M+1 / λ 测2 + 1 / 2],...; Dark lines: λ 测3 = 2D M / M = 2D M+1 / (M+1) =...; Levitation: λ 测3 = 2D M = 2D M+1 = 2D Wherein, M, M+1 are the interference fringe orders of the third-stage cleaved tip; The above equation outputs λ. 测3 Before obtaining the results, an average value can be taken to reduce the error; λ 测3 The relative uncertainty limit is μ3×2sinθ3 / M, where θ3 and μ3 are the third-order wedge apex angle and the corresponding detector pixel size, respectively.

8. A laser wavelength measurement system comprising a memory, a processor and a computer program stored on the memory, characterized in that, The processor executes the computer program to implement the steps of the laser wavelength measurement method according to any one of claims 2-7.

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