Micro-nano grating diffraction angle measurement system and measurement method

Abstract

The application discloses a kind of micro-nano grating diffraction angle measurement system and measurement method, comprising: multi-frequency laser module, grating fixture module, light beam shrinkage module, light spot detection module, light spot imaging analysis module, electric control translation stage module.This method is by the wavelength control of laser emission light, excites the diffraction spot under different light beams;Through light beam shrinkage module shrinkage, again the light beam after shrinkage is transmitted to light spot detector module and is measured to the diffraction angle, solves the problem that the diffraction angle is too large, and the detection area of detector cannot cover all diffraction spots.In general, by the device and method, the direct measurement reading of the diffraction angle of micro-nano grating under different incident wavelengths can be realized, compared with traditional measurement method, with the advantages of simple operation, high measurement accuracy, large measurement angle range, etc., and the relative energy distribution of diffraction spot, light spot shape, relative position between light spots and other information can be imaged and recorded.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of micro-nano grating, in particular to a micro-nano grating diffraction angle measurement system and method. BACKGROUND

[0002] Micro-nano grating is a kind of micro-nano optical element based on the theory of light wave diffraction, using computer aided design, using super large scale integrated circuit manufacturing process to etch steps or continuous relief structure on the substrate or the surface of traditional optical devices. Its basic principle is to use the diffraction principle to prepare steps (gratings) of a certain depth on the surface of the element, and different optical path differences are generated when the light beam passes through, which meets the Bragg diffraction condition. By different design, the divergence angle of the light beam and the morphology of the light spot are controlled to realize the function of forming a specific pattern of light beam. Since the diffraction grating was invented, it has shown great application potential in high-power laser, laser processing, laser medical treatment, microscopic imaging, laser radar, structured light illumination, laser display and other fields.

[0003] According to different purposes of the grating, different diffraction angles need to be designed. The traditional method for measuring the diffraction angle is to use a spectrophotometer, that is, the grating is placed on a rotating platform, and the diffraction angle is measured by rotating the detector. This method cannot accurately position the center of the diffraction spot, has large measurement error, and has low measurement efficiency when measuring the included angle between multiple diffraction spots and the zero-order main spot.

[0004] Therefore, it is necessary to design a system that can quickly and accurately measure the diffraction angle of micro-nano grating. SUMMARY

[0005] In order to solve the above problems of the prior art, the present application provides a micro-nano grating diffraction angle measurement system and method, which can detect the diffraction angle of the grating under different wavelengths, can simultaneously detect the energy distribution of multiple light spots, can mark the center position of the light spot according to the energy distribution, can quickly and accurately measure the included angle between the light spots, and can solve the problems of large measurement error and low measurement efficiency of the current measurement method, and solve the problem of direct reading of the diffraction angle of micro-nano grating.

[0006] The technical scheme of the present application is as follows:

[0007] A micro-nano grating diffraction angle measurement system, comprising a multi-frequency laser module, a clamp for setting a micro-nano grating to be measured, a beam shrinking module for shrinking the diffraction beam, a light spot detection module for detecting the diffraction spot, and a data processing module for light spot imaging, data analysis and diffraction angle calculation, and an electrically controlled translation stage module for controlling the distance between the modules.

[0008] A grating clamp module, a beam shrinking module and a light spot detection module are sequentially arranged along the output light direction of the multi-frequency laser module, the multi-frequency laser module, the grating clamp module, the beam shrinking module and the light spot detection module share an optical axis and are placed on an electrically controlled translation stage, the beam shrinking module is arranged behind the micro / nano grating to be measured and is configured to ensure that the diffracted light beam can completely fall on the photosensitive surface of the beam shrinking module, and the light spot detection module is arranged behind the beam shrinking module, and the light spot shrunk by the beam shrinking module can completely fall on the photosensitive surface of the light spot detection module.

[0009] The multi-frequency laser module is composed of a plurality of single-frequency lasers with single-frequency characteristics and different wavelengths.

[0010] The micro / nano grating to be measured is fixed and clamped in the center of the grating clamp, and the grating can move with the clamp on the electrically controlled translation stage.

[0011] The micro / nano grating to be measured has a large diffraction angle, and the included angle between the diffracted light beams is a constant value.

[0012] The micro / nano grating to be measured is kept perpendicular to the incident laser, and the distance is always fixed.

[0013] The light spot imaging analysis module can record the diffracted light spots under different incident light wavelengths, can simultaneously record the energy distribution of each diffracted light spot, can mark the center of the light spot, and can calculate the diffraction angle and the included angle between each light spot.

[0014] A diffraction angle measurement method of a micro / nano grating using the above measurement system, comprising the following steps:

[0015] Step 1) fix the micro / nano grating to be measured in the center of the grating clamp, make the surface of the micro / nano grating to be measured perpendicular to the optical axis of the measurement system, turn on the laser switch, and set the wavelength of the laser output light; adjust the distance between the grating clamp, the beam shrinking module and the light spot detection module, so that the light spot to be measured can completely fall within the photosensitive area of the beam shrinking module and the light spot detection module;

[0016] Step 2) mark the coordinates of the positions with the strongest energy of the first-order diffracted light spot and the zero-order main light spot (x1, y1) (x0, y0) in sequence through the light spot imaging analysis module, then input the distance value between the beam shrinking module and the light spot detection module, and the diffraction angle can be calculated. The diffraction angle calculation formula is Wherein the distance l between the first-order diffracted light spot and the zero-order main light spot is calculated through the light spot imaging analysis module after selecting two light spots, and the distance formula between two points is used. The distance d between the beam shrinking module and the light spot detection module can be directly read out through the light spot imaging analysis module because the electrically controlled translation stage is controlled by the light spot imaging analysis module.

[0017] The beneficial effects of the present application are as follows:

[0018] 1) The present method can realize grating diffraction angle measurement under different wavelengths;

[0019] 2) The present method can realize large diffraction angle micro-nano grating diffraction angle measurement through beam shrinking;

[0020] 3) The present method can realize simultaneous imaging of multiple diffraction spots, and can accurately mark the positions of the spots according to the energy distribution of the spots. It has the characteristics of high measurement efficiency and small measurement error.

[0021] 4) The present method can image and record the relative energy distribution of the diffraction spots, the spot shape, and the relative positions between the spots. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structural schematic diagram of an embodiment of a micro-nano grating diffraction angle measurement system of the present application.

[0023] Figure 2 is a principle diagram of diffraction angle measurement of the present application.

[0024] Figure 3 is a typical grating light path diffraction schematic diagram of an embodiment of the present application.

[0025] Figure 4 is a diffraction spot imaging effect schematic diagram of a spot imaging analysis module of a grating of an embodiment of the present application.

[0026] In the figure: 1 - multi-frequency laser module, 2 - grating clamp module, 3 - beam shrinking module, 4 - spot detection module, 5 - spot imaging analysis module, 6 - micro-nano grating to be measured, 7 - electrically controlled translation stage module. DETAILED DESCRIPTION

[0027] The present application will be further described in detail below in combination with the drawings and embodiments, and the embodiments are only used to explain the present application and should not limit the protection scope of the present application.

[0028] Embodiment 1

[0029] First see Figure 1The micro-nano grating diffraction angle measurement system of the application comprises a multi-frequency laser module 1, a grating clamp 2, a light beam shrinking module 3, a light spot detection module 4, a light spot imaging analysis module 5, a micro-nano grating to be measured 6 and an electrically controlled translation stage module 7, the multi-frequency laser module 1 is composed of a plurality of single-frequency lasers, the light beam shrinking module can reduce the light beam incident on the photosensitive surface in proportion, keeps the relative angle between the light spots unchanged, the light spot detection module 4 can realize photoelectric conversion, input the energy and position information of the light spots into the light spot imaging analysis module, the light spot imaging analysis module 5 can simultaneously display the energy distribution and mark the position of the light spots, and can calculate the included angle between the light spots, the micro-nano grating to be measured 6 is a kind of diffractive optical element, the multi-frequency laser module 1, the grating clamp module 2, the light beam shrinking module 3, the light spot detection module 4 and the micro-nano grating to be measured 6 are coaxially arranged and placed on the electrically controlled translation stage 7, and the electrically controlled translation stage 7 can adjust the distance between the multi-frequency laser module 1, the grating clamp module 2, the light beam shrinking module 3 and the light spot detection module 4 through the light spot imaging analysis module 5.

[0030] In the embodiment, the multi-frequency laser module 1 emits a collimated single-wavelength light beam, the grating clamp module 2 is arranged at any position behind the multi-frequency laser module 1, the micro-nano grating to be measured 6 is fixed at the center position of the grating clamp 2, the surface of the micro-nano grating to be measured 6 is perpendicular to the collimated light beam, the collimated light beam is diffracted to form a plurality of diffracted sub-beams at a specific diffraction angle after passing through the micro-nano grating to be measured, the diffracted sub-beams are transmitted to the light beam shrinking module 3, the distance between the light beam shrinking module 3 and the grating clamp module 2 is adjusted so that the diffracted light beam can completely fall within the photosensitive area of the light beam shrinking module, the diffracted light beam after shrinking is converged on the photosensitive surface of the light spot detection module 4, the distance between the light spot detection module 3 and the light beam shrinking module 2 is adjusted so that the diffracted light spot completely falls on the photosensitive surface of the light spot detector 4, the light spot imaging analysis module 5 images the light spot detected by the light spot detection module 4 according to the energy distribution, the position of the light spot is marked through the light spot imaging analysis module 5, and the distance values between the grating clamp module, the light beam shrinking module and the light spot detection module are inputted to automatically calculate the included angle of the micro-nano grating.

[0031] In the embodiment, the positions of the multi-frequency laser module 1, the grating clamp module 2, the light spot imaging analysis module 5 and the micro-nano grating to be measured 6 remain unchanged during measurement.

[0032] In the embodiment, the distance between the light beam shrinking module and the light spot detection module and the relative distance between the light spots are inputted to realize the measurement of the diffraction angle of the light beam to be measured.

[0033] Embodiment 2

[0034] Reference Figures 2-4 The micro-nano grating diffraction angle measurement method of the application comprises:

[0035] 1. Measurement preparation process

[0036] In this embodiment, such as Figure 1 As shown, the micro / nano grating to be tested 6 is placed at the center of the grating fixture module 2, with the surface of the micro / nano grating to be tested perpendicular to the optical axis of the system. The distance between the grating fixture module 2, the beam contraction module 3, and the spot detection module 4 is adjusted by the electronically controlled translation module so that the spot to be tested can be completely displayed in the center of the field of view, and the position of the spot of the beam to be tested is marked on the spot imaging analysis module.

[0037] 2. Measurement process

[0038] Mark the spot to be measured on the spot imaging analysis module, input the distance between the beam shrinking module 3 and the spot detection module 4, and automatically calculate the diffraction angle of the micro-nano grating. Figure 3 A schematic diagram of the diffraction spot imaging effect when measuring a diffraction grating is shown.

[0039] 3. Measurement Principle

[0040] like Figure 2 As shown, according to the inverse trigonometric function, the diffraction angle L is the first-order diffraction spot (i.e., Figure 3 From the first-order diffraction to the zero-order principal spot (i.e., Figure 3 The distance of the 0th order diffraction in the beam is d, and d is the distance between the beam shrinking module 3 and the spot detection module 4.

[0041] Example 3

[0042] See Figures 2-4 To further verify the effectiveness of this invention, experimental measurements were conducted using a planar grating as the experimental subject. The actual parameters were: grating material SiO2, period 600nm, grating depth 300nm, and diffraction angle 50°. When light with a wavelength of 638nm is incident perpendicularly on the grating, diffraction and beam splitting occur. The beam whose propagation direction remains unchanged is the zero-order diffracted beam, while the two symmetrical beams whose propagation directions change are both first-order diffracted beams. The experiment used 638nm as the detection light source and the diffraction angle θ was measured using the measurement system proposed in this invention. The diffraction angle is defined as the angle between the zero-order diffracted beam and the first-order diffracted beam. The specific measurement steps are as follows:

[0043] Step 1: Turn on the laser spot imaging analyzer and set the laser wavelength to 638nm.

[0044] Step 2: Place the grating on the grating fixture, with the grating base surface being the laser incident surface.

[0045] Step 3, the distance between the grating clamp module, the light beam condensing module and the light spot detection module is adjusted so that the three diffracted light spots can completely fall on the photosensitive surface of the light spot detection module by adjusting the movement of the electrically controlled translation stage through the light spot imaging analyzer control.

[0046] Step 4, the light spot imaging analyzer selects the area where the light spot needs to be measured, and the light spot imaging analyzer automatically determines the center position coordinates of the light spot according to the energy distribution of the light spot, as shown in Figure 4 The A point (x0, y0) and the B point (x1, y1) are the centers of the zero-order diffracted light spot and the first-order diffracted light spot, respectively.

[0047] Step 5, after selecting the light spot to be measured, the light spot imaging analyzer automatically calculates the diffraction angle.

[0048] In this embodiment, the A point coordinates are (0.21, 0.32), the B point coordinates are (0.42, 11.57), the distance d between the light beam condensing module and the light spot detection module is 10.23 cm, and according to the formula L is calculated as 11.00 cm, and the formula The diffraction angle θ is calculated as 50.08°. The calculation process can be automatically completed through the light spot imaging analyzer.

[0049] As described above, the distance between the grating clamp module, the light beam condensing module and the light spot detection module is accurately adjusted through the electrically controlled translation stage, the grating diffraction angle can be quickly measured through the light spot analyzer, the center coordinates of the diffracted light spot can be accurately positioned, and the shape of the diffracted light spot can be displayed. Compared with the traditional measurement method, the method has the advantages of simple operation, high measurement accuracy and large measurement angle range.

[0050] The above description is only a preferred embodiment of the present application, which is described in detail and specifically, but cannot be used to limit the scope of the present application. For those skilled in the art, without departing from the spirit and scope of the present application, some modifications and decorations can be made, which are all within the protection scope of the present application, therefore the protection scope of the present application is defined by the claims and their equivalents.

Claims

1. A system for measuring diffraction angle of a micro-nano grating, characterized in that, It comprises a multi-frequency laser module (1), a grating clamp module (2), a beam shrinking module (3), a light spot detection module (4), a light spot imaging analysis module (5), and an electrically controlled translation stage (7). The grating clamp module (2), the beam shrinking module (3), and the light spot detection module (4) are sequentially arranged along the light emission direction of the multi-frequency laser module (1) and share the same optical axis; the multi-frequency laser module (1), the grating clamp module (2), the beam shrinking module (3), and the light spot detection module (4) are placed on the electrically controlled translation stage (7); the electrically controlled translation stage (7) can control the distance between the multi-frequency laser module (1), the grating clamp module (2), the beam shrinking module (3), and the light spot detection module (4) through the light spot imaging analysis module (5); the distance between the beam shrinking module (3) and the grating clamp module (2) is adjusted according to the diffraction angle of the micro-nano grating, and all the diffraction light spots can be imaged on the photosensitive surface of the beam shrinking module (3) at the same time; the light spot detection module (4) is placed behind the beam shrinking module (3), and the distance between the light spot detection module (4) and the beam shrinking module (3) is adjusted according to the area of the shrunk light spot, and all the shrunk diffraction light spots can be imaged on the photosensitive surface of the light spot detection module (4) at the same time. The light spot imaging analysis module (5) can obtain the relative energy distribution, light spot shape, distance from the first-order diffraction light spot to the zero-order main light spot, and distance between the beam condensing module and the grating of the light spot detected by the light spot detection module (4); and the diffraction angle can be calculated by the light spot imaging analysis module (5) , wherein L is the distance from the first-order diffraction light spot to the zero-order main light spot, and d is the distance between the light spot detection module (4) and the beam condensing module (3). 2.The micro-nano grating diffraction angle measurement system according to claim 1, wherein, The multi-frequency laser module (1) can emit laser beams of multiple wavelengths, and the emitted laser beams are collimated. 3.The micro-nano grating diffraction angle measurement system according to claim 1, wherein, The micro-nano grating is placed at the center of the grating clamp module (2). 4.The micro-nano grating diffraction angle measurement system of claim 1, wherein, The beam shrinking module (3) is used for shrinking the light beams incident on the photosensitive surface in proportion and keeping the relative angles between the light spots unchanged. 5.The micro-nano grating diffraction angle measurement system according to claim 1, wherein, The light spot detection module (4) is used for detecting the light spots shrunk by the beam shrinking module (3) and transmitting the information contained in the light spots to the light spot imaging analysis module (5). 6.The micro-nano grating diffraction angle measurement system according to any one of claims 1-5, wherein, The electrically controlled translation stage (7) is connected with the light spot imaging analysis module (5), and the distance between the multi-frequency laser module (1), the grating clamp module (2), the beam shrinking module (3), and the light spot detection module (4) can be controlled through the light spot imaging analysis module (5).

7. A method for measuring the diffraction angle of a micro / nano grating according to any one of claims 1 to 6, characterized in that, It comprises the following steps: Step 1: place the grating to be measured at the center of the grating clamp module (2), turn on the multi-frequency laser module (1), set the wavelength of the emitted light, adjust the grating so that the incident laser is perpendicular to the grating surface, and adjust the distance between the grating clamp module (2), the beam shrinking module (3), and the light spot detection module (4) so that the diffraction light spots fall completely on the detection surfaces of the beam shrinking module (3) and the light spot detection module (4); Step 2, the position coordinates (x1, y1) and (x0, y0) of the strongest energy of the first-order diffraction spot and the main spot are marked in turn by the light spot imaging analysis module (5), and then the distance value between the light beam condensing module (3) and the light spot detection module (4) is input, so that the diffraction angle is calculated according to the following formula : ； Wherein the distance L from the first diffraction spot to the main spot, after the two spots are selected by the spot imaging analysis module (5), the distance between the two points is calculated by the formula calculated; The movement of the electrically controlled translation stage (7) is controlled through the light spot imaging analysis module (5), and thus the distance d between the beam shrinking module (3) and the light spot detection module (4) can be directly read out through the light spot imaging analysis module (5).

8. The method according to claim 7, wherein the wavelength of the laser is 638 nm. ​

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