Regulation and super-resolution shaping system and method based on radial polarization annular correlated light beams

Abstract

The invention discloses a regulation and control and super-resolution shaping system and method based on a radial polarization annular correlated light beam, and the system comprises a laser beam expanding collimator which is used for expanding the diameter of a laser beam and improving the accuracy of the laser beam, and a polarizer carries out the linear polarization of the laser beam, the radial polarization converter converts an obtained linearly polarized laser beam into radial polarized light, the spatial light modulator and the 4f filter carry out beam phase and amplitude adjustment on the radial polarized light, the high numerical aperture microscope carries out super-resolution focusing on the beam, and a radial polarized annular correlation beam is generated. According to the scheme, low-coherence, small-size and high-resolution light spot generation is realized through accurate optical elements and phase regulation and control, and the limitation of mutual restriction of resolution and coherence in a traditional focusing system is overcome.

Description

Technical Field

[0001] The present invention belongs to the field of optics, and in particular relates to a control and super-resolution shaping system and method based on radially polarized annular correlated light beams. Background Art

[0002] With the rapid development of laser technology, the focusing characteristics of light beams have become increasingly important in many fields, especially in applications such as laser processing, optical imaging, beam manipulation, and biomedicine. Although traditional beam models, such as Gauss-Schermer beams, perform well in many applications, they still have some limitations under the requirements of high precision and high resolution. In laser processing, the size of the spot directly affects the processing accuracy and efficiency. When focusing, traditional beams often cannot achieve a small enough spot, resulting in low processing quality, especially in the field of micro-nano processing. In optical imaging, the diffraction effect of the beam will cause image blur and affect the resolution of the imaging system. Therefore, how to reduce the spot size while maintaining high resolution has become an important topic in optical research.

[0003] The study of partially coherent light provides new ideas for beam shaping. By adjusting the coherence of the light source, the focusing characteristics of the light beam can be improved to a certain extent. However, the existing partially coherent light model still faces complex implementation conditions and low flexibility in practical applications. Pseudo-Shermo beams have received widespread attention in recent years due to their unique coherence and polarization characteristics. Studies have shown that pseudo-Shermo beams can produce smaller spots when focused and exhibit superior focusing performance at high numerical apertures. However, the existing pseudo-Shermo beam models still have certain limitations when dealing with complex light fields. In order to overcome the above problems, it is urgent to develop new beam models to achieve smaller spot sizes and higher focusing performance. The introduction of the radially polarized annular correlated beam model is precisely to solve the shortcomings of traditional beam models in high-precision applications and provide a new solution. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a control and super-resolution shaping system and method based on radially polarized annular correlated light beams, so as to improve the focusing performance and imaging quality of the light beams and meet the requirements of modern optical technology for high-performance light beams.

[0005] The specific technical solution for achieving the purpose of the present invention is:

[0006] A control and super-resolution shaping system based on radially polarized annular correlated light beams, comprising a laser beam expansion collimator, a polarizer, a radial polarization converter, a spatial light modulator, a 4f filter and a high numerical aperture microscope;

[0007] The laser beam expansion collimator, polarizer, radial polarization converter, spatial light modulator, 4f filter and high numerical aperture microscope are sequentially arranged along the laser light path;

[0008] Among them, the laser beam expander collimator is used to expand the diameter of the laser beam and improve the accuracy of the beam. The polarizer obtains linear polarization of the laser beam. The radial polarization converter converts the linearly polarized laser beam into radially polarized light. The spatial light modulator and 4f filter adjust the phase and amplitude of the radially polarized light beam. The high numerical aperture microscope performs super-resolution focusing on the beam to generate a radially polarized annular correlated beam.

[0009] Furthermore, the light transmission axis of the polarizer is set to the x-axis to ensure that the laser beam forms radially polarized light after passing through the radial polarization converter.

[0010] Furthermore, the radial polarization converter converts the light beam into radial polarization:

[0011]

[0012] in, is the Gaussian amplitude of the incident light, r1 and r2 represent the position vectors of any two points on the plane of the incident light, w0 is the waist width of the incident light beam, and α and β represent parameters related to the spatial position.

[0013] Furthermore, the radially polarized light converted by the radial polarization converter is phase-controlled by the spatial light modulator, and a partially coherent light field cross-spectral density matrix with special transmission characteristics is constructed during the control process. The output light after control is:

[0014]

[0015] Among them, δ1 and δ2 represent the coherence parameters of the correlation structure in the partial coherence function.

[0016] Furthermore, the partially coherent light field cross spectral density matrix must have an integral representation:

[0017]

[0018]

[0019] Among them, p αβ (v) is a non-negative weight function, v represents a random variable that measures the weight, K α and K β are two arbitrary kernel functions.

[0020] Further, the radially polarized light is shaped in a spatial light modulator;

[0021] The shaping is to separate each independent cross-spectral density function after propagating a certain distance by using the tilted phase:

[0022]

[0023] Where d1 and d2 represent the spacing constants between arrays, and M and N are the parameters of the number of pixels related to the far-field light intensity.

[0024] The present invention also provides a method for regulating and super-resolution shaping of radially polarized annular correlated light beams, comprising the following steps:

[0025] Step 1: The laser emits a laser beam for writing, which passes through a laser beam expander and collimator to reach the required beam waist width;

[0026] Step 2: The laser beam passes through a polarizer to form a linearly polarized laser beam, and then passes through a radial polarization converter to convert the linearly polarized laser beam into radially polarized light by controlling the arrangement of liquid crystal units through a computer;

[0027] Step 3, the radially polarized light is irradiated to the spatial light modulator, and the spatial light modulator regulates and shapes the radially polarized light to generate a partially coherent modulated light beam, which passes through a 4f filter to obtain a first-order diffracted light beam after collimation and filtering. This light beam is a partially coherent light beam that can image the target;

[0028] Step 4: The generated partially coherent light beam is subjected to super-resolution focusing through a high numerical aperture microscope to generate a radially polarized annular correlated light beam.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The scheme of the present invention realizes a low-coherence, small-size, high-resolution focused light spot by combining precise optical elements with phase control, partial coherent light control, 4f filtering system and spatial light modulator (SLM) dynamic light field control, effectively overcoming the limitation of the mutual restriction of resolution and coherence in the traditional focusing system. The polarization state is optimized by the radial polarization converter, so that the light beam forms a smaller light spot under the high numerical aperture system, and the micro-nano processing accuracy is improved; the coherence parameters and spacing parameters in the cross-spectral density function are dynamically controlled by SLM to optimize the spatial coherence of the light beam, reduce the blur caused by the diffraction effect, and improve the quality of microscopic imaging; combined with 4f system filtering, the light field distribution is adjusted on the Fourier spectrum surface, the side lobes are suppressed to enhance the high-frequency components, and super-resolution beam shaping is realized, which further improves the contrast and resolution of microscopic imaging, and at the same time enhances the fineness of micro-nano processing. The scheme of the present invention breaks through the limitations of traditional light beams in super-resolution microscopic imaging and micro-nano processing, and provides an efficient, accurate and stable light field control tool, which provides a new technical means for micro-nano structure processing and low-coherence microscopic imaging quality improvement.

[0031] The present invention is further described below in conjunction with specific implementation modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the architecture of the control and super-resolution shaping system based on radially polarized annular correlated light beams of the present invention.

[0033] Figure 2 Schematic diagram of a control and super-resolution shaping system based on radially polarized annular correlated light beams in an embodiment of the present invention.

[0034] Figure 3 Schematic diagram of the theory of regulating the coherence length on radially polarized circular correlated light beams.

[0035] Figure 4 Theoretical schematic diagram of linear array obtained by simulating different beam models. DETAILED DESCRIPTION

[0036] Example

[0037] In order to clearly describe the technical solution and the effects achieved by the present invention, the technical solution of the present invention is clearly explained below in combination with the accompanying drawings and specific embodiments of the present invention, so that technical personnel in the field can implement the invention without performing creative work. The structure shown in the accompanying drawings is not the entire actual structure but only a part of the actual structure. It should be noted that all other embodiments made by ordinary technical personnel in the field on the basis of the embodiments of the present invention without performing creative work should fall within the protection scope of the present invention.

[0038] The following examples are only for better explanation of the present invention, but the content of the present invention is not limited to the application in the examples. Therefore, those skilled in the art can make non-essential modifications to the implementation scheme based on the above invention content and apply it to other embodiments, which is still within the protection scope of the present invention. In addition, the experimental methods without specific conditions in the following examples should be carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the expressions in the text are not specially explained, they are only used for distinction and have no other meanings.

[0039] Combination Figure 1 , a control and super-resolution shaping system based on radially polarized annular correlated light beams, comprising a laser beam expansion collimator 1, a polarizer 2, a radial polarization converter 3, a spatial light modulator 4, a 4f filter 5 and a high numerical aperture microscope 6;

[0040] The laser beam expansion collimator 1, polarizer 2, radial polarization converter 3, spatial light modulator 4, 4f filter 5 and high numerical aperture microscope 6 are sequentially arranged along the laser light path;

[0041] Among them, the laser beam expander collimator 1 is used to expand the diameter of the laser beam and improve the beam accuracy, the polarizer 2 obtains linear polarization of the laser beam, the radial polarization converter 3 converts the linearly polarized laser beam into radially polarized light, the spatial light modulator 4 and 4f filter 5 adjust the phase and amplitude of the radially polarized light beam, and the high numerical aperture microscope 6 performs super-resolution focusing on the light beam to generate a radially polarized annular correlated light beam.

[0042] The light transmission axis of the polarizer 2 is set as the x-axis to ensure that the laser beam forms radially polarized light after passing through the radial polarization converter.

[0043] The radial polarization converter 3 converts the light beam into radial polarization:

[0044]

[0045] in, is the Gaussian amplitude of the incident light, that is, the initial light intensity, r1 and r2 represent the position vectors of any two points on the incident light plane, w0 is the waist width of the incident light beam, and α and β represent parameters related to the spatial position.

[0046] The spatial light modulator 4 is used to control the shape of the light beam. The principle is mode expansion, which divides the light beam into discrete modes, and adds random phases to each mode to form a hologram. To ensure that the modes are independent, enough random phase holograms are required, and the number of loaded holograms can also be reduced according to actual conditions. The coherence of light is used to offset part of the diffraction expansion effect, change the light intensity distribution, and achieve incoherent superposition of modes. By loading the hologram into the spatial light modulator in the form of time projection, the time is statistically averaged, and the cross-spectral density function structure is approximated to achieve beam shaping.

[0047] Specifically in this solution, the radially polarized light converted by the radial polarization converter 3 is phase-controlled by the spatial light modulator 4. During the control process, a partially coherent light field cross-spectral density matrix with special transmission characteristics is constructed. The output light after control is:

[0048]

[0049]

[0050] Among them, r = (x, y) represents the position vector of two points on the source plane, and δ1 and δ2 represent the coherence parameters of the correlation structure in the partial coherence function.

[0051] In order to be physically feasible, the partially coherent light field cross-spectral density matrix must have an integral representation:

[0052]

[0053] Among them, p αβ (v) is a non-negative weight function, v represents a random variable that measures the weight, K α and K β are two arbitrary kernel functions.

[0054] The radially polarized light is shaped in the spatial light modulator 4;

[0055] The shaping is to separate each independent cross-spectral density function after propagating a certain distance by using the tilted phase:

[0056]

[0057] Where d1 and d2 represent the spacing constants between arrays, and M and N are the parameters of the number of pixels related to the far-field light intensity.

[0058] The present invention also provides a method for regulating and super-resolution shaping of radially polarized annular correlated light beams, comprising the following steps:

[0059] Step 1: The laser emits a laser beam for writing, which passes through a laser beam expander collimator 1 to reach the required beam waist width;

[0060] Step 2: The laser beam passes through the polarizer 2 to form a linearly polarized laser beam, and then passes through the radial polarization converter 3. The arrangement of the liquid crystal unit is controlled by a computer to convert the linearly polarized laser beam into radially polarized light:

[0061]

[0062] in, is the Gaussian amplitude of the incident light, r1 and r2 represent the position vectors of any two points on the incident light plane, w0 is the waist width of the incident light beam, and α and β represent parameters related to the spatial position;

[0063] Step 3, the radially polarized light is irradiated to the spatial light modulator 4, and the spatial light modulator 4 regulates and shapes the radially polarized light to generate a partially coherent modulated light beam, which passes through the 4f filter 5 to obtain a first-order diffracted light beam after collimation and filtering. This light beam is a partially coherent light beam that can image the target;

[0064] The radial polarized light is regulated as follows:

[0065]

[0066] Among them, δ1 and δ2 represent the coherence parameters of the correlation structure in the partial coherence function, r1 and r2 represent the position vectors of any two points on the incident light plane, w0 is the waist width of the incident light beam, and α and β represent parameters related to the spatial position.

[0067] The shaping of the radially polarized light is to separate each independent cross-spectral density function after propagating a certain distance by using the tilted phase:

[0068]

[0069] Where d1 and d2 represent the spacing constants between arrays, and M and N are the parameters of the number of pixels related to the far-field light intensity.

[0070] Step 4: The generated partially coherent light beam is subjected to super-resolution focusing by a high numerical aperture microscope 6 to generate a radially polarized annular correlated light beam.

[0071] like Figure 2 FIG. 1 is a schematic diagram of an experimental device for the radially polarized annular correlated light beam proposed in the present invention. Figure 2This is a schematic diagram of the experimental device for spot correction of the light source module of the radially polarized annular correlated light beam of the present invention. First, the laser beam emitted by the laser 7 passes through a beam expander 8, and then passes through a linear polarizer 9 to form a linearly polarized laser beam, and then passes through a radial polarization converter 10 to control the arrangement of liquid crystal units through a computer to convert the linear polarization into radial polarization light, and then passes through a reflector 11 so that the light beam is irradiated on the spatial light modulator 12 to generate a partially coherent linearly polarized light beam with special statistical characteristics; then the generated partially coherent light beam passes through a 4f system composed of a thin lens 13, a pinhole aperture 14, and a thin lens 15 to obtain a collimated and filtered first-order diffracted light beam, which is a partially coherent light beam that can image the target, wherein the 4f filter system can also be replaced by an aperture; the generated partially coherent light beam is focused by a high numerical aperture microscope objective 16, so that a nanometer-level spot can be observed on the CCD 17 near the focus. The focal length of thin lens 12 is the same as that of thin lens 14, 150 mm, and the focal length of thin lens 15 is 100 mm.

[0072] Figure 3 This is a theoretical schematic diagram of the regulation of the coherence length on the radially polarized annular correlated light beam. By reducing the value of δ1 and at the same time minimizing the difference Δδ between δ1 and δ2, the spot size on the focal plane can be significantly reduced. Figure 4 The theoretical schematic diagram of the linear array was obtained by simulating different beam models, where a and b are radially polarized plane waves and radially polarized Laguerre beams, respectively. It was found that the linear array was still difficult to be clearly distinguished by adjusting the spot spacing. Then, a radially polarized pseudo-Scherm beam c was used for simulation, and it was found that the linear array could only be identified when the array spacing was large, but when the array spacing became smaller, the array was still blurred. Finally, when the radially polarized annular correlated beam d was used for control, it was found that the linear array could be effectively distinguished even when the array spacing was extremely small. The results show that the radially polarized annular correlated beam has an excellent control effect on the light field under tight focusing conditions and has the potential to significantly improve the spatial resolution. Parameter selection: λ = 632.8nm, f = 3mm, ω = 3mm.

[0073] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A control and super-resolution shaping system based on radially polarized annular correlated beams, characterized in that: It comprises a laser beam expansion collimator (1), a polarizer (2), a radial polarization converter (3), a spatial light modulator (4), a 4f filter (5) and a high numerical aperture microscope (6); The laser beam expansion collimator (1), the polarizer (2), the radial polarization converter (3), the spatial light modulator (4), the 4f filter (5) and the high numerical aperture microscope (6) are arranged in sequence along the laser light path; The laser beam expander and collimator (1) is used to expand the diameter of the laser beam and improve the beam accuracy; the polarizer (2) obtains linear polarization on the laser beam; the radial polarization converter (3) converts the linearly polarized laser beam into radially polarized light; the spatial light modulator (4) and the 4f filter (5) adjust the phase and amplitude of the radially polarized light beam; and the high numerical aperture microscope (6) performs super-resolution focusing on the beam to generate a radially polarized annular correlated beam.

2. The control and super-resolution shaping system based on radially polarized annular correlated light beams according to claim 1 is characterized in that: The light transmission axis of the polarizer (2) is set as the x-axis to ensure that the laser beam forms radially polarized light after passing through the radial polarization converter.

3. The control and super-resolution shaping system based on radially polarized annular correlated light beams according to claim 1, characterized in that: The radial polarization converter (3) converts the light beam into radial polarization: in, is the Gaussian amplitude of the incident light, r1 and r2 represent the position vectors of any two points on the plane of the incident light, w0 is the waist width of the incident light beam, and α and β represent parameters related to the spatial position.

4. The control and super-resolution shaping system based on radially polarized annular correlated light beams according to claim 3 is characterized in that: The radially polarized light converted by the radial polarization converter (3) is phase-controlled by the spatial light modulator (4). During the control process, a partially coherent light field cross-spectral density matrix with special transmission characteristics is constructed. The output light after control is: Among them, δ1 and δ2 represent the coherence parameters of the correlation structure in the partial coherence function.

5. The control and super-resolution shaping system based on radially polarized annular correlated light beams according to claim 4, characterized in that: The partially coherent light field cross spectral density matrix must have an integral representation: Among them, p αβ (v) is a non-negative weight function, v represents a random variable that measures the weight, K α and K β are two arbitrary kernel functions.

6. The control and super-resolution shaping system based on radially polarized annular correlated light beams according to claim 4, characterized in that: The radially polarized light is shaped in a spatial light modulator (4); The shaping is to separate each independent cross-spectral density function after propagating a certain distance by using the tilted phase: Where d1 and d2 represent the spacing constants between arrays, and M and N are the parameters of the number of pixels related to the far-field light intensity.

7. A method for regulating and super-resolution shaping based on radially polarized annular correlated beams, characterized in that: The following steps are involved: Step 1: The laser emits a laser beam for writing, which passes through a laser beam expander and collimator (1) to reach the required beam waist width; Step 2: The laser beam passes through the polarizer (2) to form a linearly polarized laser beam, and then passes through the radial polarization converter (3), and the arrangement of the liquid crystal unit is controlled by a computer to convert the linearly polarized laser beam into radially polarized light; Step 3, the radially polarized light is irradiated to the spatial light modulator (4), and the spatial light modulator (4) regulates and shapes the radially polarized light to generate a partially coherent modulated light beam, which passes through a 4f filter (5) to obtain a beam of first-order diffracted light after collimation and filtering. This beam is a partially coherent light beam that can image the target; Step 4: The generated partially coherent light beam is subjected to super-resolution focusing through a high numerical aperture microscope (6) to generate a radially polarized annular correlated light beam.

8. The control and super-resolution shaping system based on radially polarized annular correlated light beams according to claim 7, characterized in that: The radial polarization conversion in step 2 is: in, is the Gaussian amplitude of the incident light, r1 and r2 represent the position vectors of any two points on the plane of the incident light, w0 is the waist width of the incident light beam, and α and β represent parameters related to the spatial position.

9. The control and super-resolution shaping system based on radially polarized annular correlated light beams according to claim 7, characterized in that: The regulation of the radial polarized light in step 3 is: Among them, δ1 and δ2 represent the coherence parameters of the correlation structure in the partial coherence function, r1 and r2 represent the position vectors of any two points on the incident light plane, w0 is the waist width of the incident light beam, and α and β represent parameters related to the spatial position.

10. The control and super-resolution shaping system based on radially polarized annular correlated light beams according to claim 7, characterized in that: The shaping of the radially polarized light in step 3 is to separate each independent cross-spectral density function after propagating a certain distance by using the tilted phase: Where d1 and d2 represent the spacing constants between arrays, and M and N are the parameters of the number of pixels related to the far-field light intensity.

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