Radially polarized, partially coherent, cosh beam generation system and method

Abstract

The application discloses a radial polarization twisted partially coherent hyperbolic cosine beam generating system and method, wherein the semiconductor laser is used for emitting a light beam, the light beam is expanded through a beam expander, reflected to a spatial light modulator through a mirror, and the phase and amplitude of the light beam are adjusted through the spatial light modulator and a 4f filter unit; the light beam obtains linear polarization property through a polarizer, so that twisted partially coherent polarized light is obtained; the twisted partially coherent polarized light generates twisted partially coherent radial polarization light beams through a vortex wave plate, is focused through a focusing lens, and finally realizes filtering through a polarizing detector; finally, the focused light beam is collected and observed by a charge coupled device. The application provides a radial polarization twisted partially coherent hyperbolic cosine light source generating system, the optical path structure is relatively simple, the construction and debugging are difficult and the repeatability is high, the phase distribution and correlation structure of the light field can be flexibly adjusted through the spatial light modulator.

Description

Technical Field

[0001] This invention belongs to the field of optical field manipulation, specifically relating to a system and method for generating radially polarized distorted partially coherent hyperbolic cosine beams. Background Technology

[0002] Radially polarized beams, with their unique polarization distribution and focusing field enhancement characteristics, have significant application value in laser micromachining, particle manipulation, optical tweezers, and vector light field polarization control. Meanwhile, partially coherent beams and twisted beams, due to their special transmission evolution, self-splitting, and rotation characteristics, have become a research focus in the field of light field manipulation. Currently, traditional methods for generating and experimentally controlling radially polarized partially coherent beams still have significant shortcomings. Existing optical path systems have complex device layouts, are difficult to build and debug, have poor overall structural stability, are easily affected by environmental vibrations and temperature, and have poor experimental repeatability. Furthermore, existing technologies limit the adjustable range of beam spot morphology and polarization state distribution. In addition, the lack of dedicated filtering and polarization isolation designs makes it difficult to suppress stray light and higher-order diffraction light, easily generating coherent crosstalk, resulting in low beam generation purity. The spectral intensity and polarization state evolution of the beam during lens focusing and transmission are also difficult to control precisely. Moreover, traditional theoretical models have a simple structure and cannot adapt to modeling complex characteristic light fields, leading to large discrepancies between theoretical simulations and experimental results, making it difficult to meet the needs of high-precision beam control in multiple scenarios.

[0003] Therefore, developing a beam generation system with a simplified optical path layout, easy debugging and operation, strong anti-interference ability, and high degree of freedom in optical field control, and realizing integrated and coordinated control of beam coherence structure and torsion characteristics, has become a key issue that needs to be addressed in the fields of optical field vector control, laser micromachining, particle manipulation, and optical communication. It is also an important prerequisite for promoting the practical application and scenario-based application of such novel composite coherent beams. Summary of the Invention

[0004] The purpose of this invention is to provide a radially polarized distorted partially coherent hyperbolic cosine beam generation system and method, which simplifies the optical path structure, ensures the safety of core components, and controls the beam field at the source plane and at different transmission distances.

[0005] The specific technical solution for achieving the objective of this invention is as follows:

[0006] A radially polarized distorted partially coherent hyperbolic cosine beam generation system includes a semiconductor laser, a beam expander, a mirror, a spatial light modulator, a 4f filter unit, a polarizer, a vortex waveplate, a focusing lens, an analyzer, and a charge-coupled device arranged sequentially along the optical path.

[0007] The semiconductor laser is used to emit a beam, which is expanded by a beam expander and reflected by a mirror to a spatial light modulator. The phase and amplitude of the beam are adjusted by the spatial light modulator and a 4f filter unit.

[0008] Subsequently, the beam passes through a polarizer to obtain a linearly polarized beam, thereby acquiring the distorted coherent polarized light;

[0009] Subsequently, the twisted coherent polarized light is passed through a vortex waveplate to generate a twisted coherent radially polarized beam, which is then focused by a focusing lens, filtered by an analyzer, and finally the optical field characteristics of the focused beam are collected and observed by a charge-coupled device.

[0010] Furthermore, the 4f filter unit includes a first thin lens, a pinhole aperture, and a second thin lens;

[0011] The pinhole aperture is located on the output side of the spatial light modulator. The first thin lens and the second thin lens are respectively located on both sides of the pinhole aperture. The pinhole aperture is located at the confocal plane of the first thin lens and the second thin lens, and the position of the pinhole aperture covers the range of the first-order diffraction light output by the spatial light modulator.

[0012] Furthermore, the polarization direction of the polarizer is orthogonal to the polarization direction of the analyzer.

[0013] Furthermore, the transmission axis of the polarizer is set to the optical axis direction to ensure that radially polarized light is formed after passing through the vortex waveplate.

[0014] Furthermore, the theoretical beam model for beam modulation using the spatial light modulator is a partially coherent optical field cross-spectral density matrix with special transmission characteristics constructed on the source plane, and its functional expression is:

[0015]

[0016]

[0017] in, and Represents the position vector on the source plane. It is the beam waist half-width. Represents the beam coherence parameters. Indicates the distortion factor. Let be the order of the beam. Represented as topological load, azimuth angle = , It is a constant real number and satisfies .

[0018] Furthermore, the weighting function and kernel function required to construct the cross spectral density matrix of the radially polarized distorted partially coherent hyperbolic cosine beam are respectively expressed as:

[0019]

[0020]

[0021] Where the amplitude function for

[0022]

[0023] in Represents the position vector on the source plane. and It is a unitless vector that is not limited by dimensions. For the beam width, It is the Cartesian component of the wave electric field vector and the constant phase difference. The correlation coefficient between them.

[0024] This solution also provides a method for generating a radially polarized distorted partially coherent hyperbolic cosine beam in the above system, including the following steps:

[0025] Step 1: The semiconductor laser emits a laser beam, which passes through a beam expander to achieve the desired beam waist width;

[0026] Step 2: The expanded beam is irradiated by the reflector to the spatial light modulator to generate a partially coherent modulated beam. The beam passes through the first thin lens, the pinhole aperture, and the second thin lens of the 4f filter unit to obtain a collimated and filtered first-order diffracted beam. This beam is the partially coherent beam that can image the target.

[0027] Step 3: The formed beam is obtained by a polarizer to obtain a linearly polarized beam, and then converted into a twisted partially coherent radially polarized beam by a vortex plate.

[0028] Step 4: The twisted coherent radially polarized beam is focused by a focusing lens and filtered by an analyzer orthogonal to the initial polarization direction. The light field distribution at different transmission distances is acquired using a charge-coupled device (CCD) to observe and control the beam.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) This invention provides a radially polarized twisted partial coherent hyperbolic cosine light source generation system with a simple optical path structure, low difficulty in building and debugging and strong repeatability. It solves the problem of insufficient stability of traditional optical path devices and can simultaneously realize the control of rotation characteristics and self-splitting characteristics, providing a brand-new beam control tool for particle capture, optical tweezers technology, laser micromachining and other fields.

[0031] (2) The present invention can flexibly adjust the phase distribution and correlation structure of the light field by means of a spatial light modulator, and adjust the parameters. , , , It can adjust the spectral density and rotation characteristics of the beam, with a high degree of freedom in control, and can output target beams with different characteristics as needed to adapt to different application scenarios;

[0032] (3) This invention relies on the polarization modulation mechanism to achieve effective separation of signal light and stray light at the focal plane. The polarization device optimizes the quality and stability of optical signal transmission, making it suitable for optical communication and optical detection requirements in complex scenarios. At the same time, the use of a low-coherence light source can effectively avoid coherence crosstalk problems, and has broad application prospects in the field of optical communication.

[0033] The present invention will be further described below with reference to specific embodiments. Attached Figure Description

[0034] Figure 1 This is a structural block diagram of the radially polarized distorted partial coherent hyperbolic cosine light source generation system in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the experimental setup for the radially polarized distorted partial coherent hyperbolic cosine light source generation system in an embodiment of the present invention.

[0036] Figure 3 This is a schematic diagram showing the change of beam intensity with transmission distance for different values ​​of l in the theoretical simulation of this invention.

[0037] Figure 4 This is a schematic diagram showing the change in beam intensity with transmission distance for different values ​​of l generated in the experiment of this invention. Detailed Implementation

[0038] Example

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0041] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0042] Combination Figure 1 A radially polarized distorted partially coherent hyperbolic cosine beam generation system includes a semiconductor laser, a beam expander, a mirror, a spatial light modulator, a 4f filter unit, a polarizer, a vortex waveplate, a focusing lens, an analyzer, and a charge-coupled device arranged sequentially along the optical path.

[0043] The semiconductor laser is used to emit a beam, which is expanded by a beam expander and reflected by a mirror to a spatial light modulator. The phase and amplitude of the beam are adjusted by the spatial light modulator and a 4f filter unit.

[0044] Subsequently, the beam passes through a polarizer to obtain a linearly polarized beam, thereby acquiring the distorted coherent polarized light;

[0045] Subsequently, the twisted coherent polarized light is passed through a vortex waveplate to generate a twisted coherent radially polarized beam, which is then focused by a focusing lens, filtered by an analyzer, and finally the optical field characteristics of the focused beam are collected and observed by a charge-coupled device.

[0046] The 4f filter unit includes a first thin lens, a pinhole aperture, and a second thin lens. The pinhole aperture is located on the output side of the spatial light modulator. The first thin lens and the second thin lens are respectively located on both sides of the pinhole aperture. The pinhole aperture is located at the confocal plane of the first thin lens and the second thin lens, and the position of the pinhole aperture covers the range of the first-order diffraction light output by the spatial light modulator.

[0047] The polarization direction of the polarizer is orthogonal to the polarization direction of the analyzer.

[0048] The transmission axis of the polarizer is set to the direction of the optical axis to ensure that radially polarized light is formed after passing through the vortex waveplate.

[0049] Furthermore, the theoretical beam model for beam modulation using the spatial light modulator is a partially coherent optical field cross-spectral density matrix with special transmission characteristics constructed on the source plane, and its functional expression is:

[0050]

[0051]

[0052] in, and Represents the position vector on the source plane. It is the beam waist half-width. Represents the beam coherence parameters. Indicates the distortion factor. Let be the order of the beam. Represented as topological load, azimuth angle = , It is a constant real number and satisfies .

[0053] The weighting function and kernel function required to construct the cross spectral density matrix of the radially polarized distorted partially coherent hyperbolic cosine beam are expressed as follows:

[0054]

[0055]

[0056] Where the amplitude function for

[0057]

[0058] in Represents the position vector on the source plane. and It is a unitless vector that is not limited by dimensions. For the beam width, It is the Cartesian component of the wave electric field vector and the constant phase difference. The correlation coefficient between them.

[0059] Combination Figure 2 The radial polarization distorted partial coherent hyperbolic cosine light source generation system described in this embodiment includes a laser 9, a beam expander 10, a reflector 11, a spatial light modulator 12, a 4f filter unit, a polarizer 16, a vortex waveplate 17, a focusing lens 18, an analyzer 19, and a charge-coupled device 20.

[0060] The laser 9, beam expander 10, reflector 11, spatial light modulator 12, 4f filter unit, polarizer 16, vortex waveplate 17, focusing lens 18, analyzer 19 and charge-coupled device 20 are arranged sequentially along the optical path.

[0061] The 4f filter unit includes a first thin lens 13, a pinhole aperture 14, and a second thin lens 15; the focal length of the first thin lens 13 and the second thin lens 15 is 150mm, and the aperture of the pinhole aperture 14 is 0.5mm, which is located at the confocal surface of the two lenses.

[0062] The transmission axis of the polarizer 16 is set to the direction of the optical axis to ensure that radially polarized light is formed after passing through the vortex waveplate.

[0063] The spatial light modulator 12 shapes and controls the beam by discretely sampling according to the mode expansion to obtain a set of modes, and then adding different random phases to this set of modes to form a hologram. In order to ensure that all modes are independent of each other, a sufficient number of holograms with random phases are required. The number of loaded holograms can be appropriately reduced according to the actual situation.

[0064] After the laser 9 emits a beam, it is first expanded by the beam expander 10, then refracted by the reflector 11, and incident on the modulation surface of the spatial light modulator 12. The phase and amplitude of the beam are adjusted by the spatial light modulator 12 and the 4f filter unit, and then a linearly polarized beam is obtained by the polarizer 16, thereby acquiring the twisted coherent polarized light. The twisted coherent polarized light passes through the vortex waveplate 17 to generate a twisted coherent radially polarized beam. At this time, an analyzer can be used to check whether the emitted beam is radially polarized. Then, it is focused by the focusing lens 18, and finally filtered by the analyzer 19 orthogonal to the initial polarization direction. Finally, the light field distribution at transmission distances of 200mm, 300mm, and 400mm is collected by the charge-coupled device 20. By adjusting the parameters... , , , It enables precise control of beam characteristics. In this embodiment, the core beam model parameters are selected as follows: , laser wavelength .

[0065] like Figure 3 , Figure 4 As shown in the figures, the two figures represent the beam intensity as a function of topological charge at different propagation distances, as simulated in theory and generated in experiments. The diagram illustrates the changes, where (a)-(d) represent... The evolution of light intensity propagation over time, (e)-(h) is The evolution of light intensity propagation over time was studied. Through comparison of theory and experiments, the experimental results showed good agreement with the theoretical simulation results, verifying the reliability and accuracy of the system.

[0066] In addition, this solution also provides a method for generating radially polarized distorted partially coherent hyperbolic cosine beams based on the above system, characterized by comprising the following steps:

[0067] Step 1: The semiconductor laser emits a laser beam, which passes through a beam expander to achieve the desired beam waist width;

[0068] Step 2: The expanded beam is irradiated by the reflector to the spatial light modulator to generate a partially coherent modulated beam. The beam passes through the first thin lens, the pinhole aperture, and the second thin lens of the 4f filter unit to obtain a collimated and filtered first-order diffracted beam. This beam is the partially coherent beam that can image the target.

[0069] Step 3: The formed beam is obtained by a polarizer to obtain a linearly polarized beam, and then converted into a twisted partially coherent radially polarized beam by a vortex plate.

[0070] Step 4: The twisted coherent radially polarized beam is focused by a focusing lens and filtered by an analyzer orthogonal to the initial polarization direction. The light field distribution at different transmission distances is acquired using a charge-coupled device (CCD) to observe and control the beam.

[0071] The embodiments described above are merely one implementation method of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A radially polarized distorted partially coherent hyperbolic cosine beam generation system, characterized in that, It includes a semiconductor laser, a beam expander, a mirror, a spatial light modulator, a 4f filter unit, a polarizer, a vortex plate, a focusing lens, an analyzer, and a charge-coupled device arranged sequentially along the optical path; The semiconductor laser is used to emit a beam, which is expanded by a beam expander and reflected by a mirror to a spatial light modulator. The phase and amplitude of the beam are adjusted by the spatial light modulator and a 4f filter unit. Subsequently, the beam passes through a polarizer to obtain a linearly polarized beam, thereby acquiring the distorted coherent polarized light; Subsequently, the twisted coherent polarized light is passed through a vortex waveplate to generate a twisted coherent radially polarized beam, which is then focused by a focusing lens, filtered by an analyzer, and finally the optical field characteristics of the focused beam are collected and observed by a charge-coupled device.

2. The radially polarized distorted partially coherent hyperbolic cosine beam generation system according to claim 1, characterized in that, The 4f filter unit includes a first thin lens, a pinhole aperture, and a second thin lens; The pinhole aperture is located on the output side of the spatial light modulator. The first thin lens and the second thin lens are respectively located on both sides of the pinhole aperture. The pinhole aperture is located at the confocal plane of the first thin lens and the second thin lens, and the position of the pinhole aperture covers the range of the first-order diffraction light output by the spatial light modulator.

3. The radially polarized distorted partially coherent hyperbolic cosine beam generation system according to claim 1, characterized in that, The polarization direction of the polarizer is orthogonal to the polarization direction of the analyzer.

4. The radially polarized distorted partially coherent hyperbolic cosine beam generation system according to claim 1, characterized in that, The transmission axis of the polarizer is set to the direction of the optical axis to ensure that radially polarized light is formed after passing through the vortex waveplate.

5. The radially polarized distorted partially coherent hyperbolic cosine beam generation system according to claim 1, characterized in that, The theoretical beam model for beam modulation using the spatial light modulator is a partially coherent optical field cross-spectral density matrix with special transmission characteristics constructed on the source plane, and its functional expression is: ； ； in, and Represents the position vector on the source plane. It is the beam waist half-width. Represents the beam coherence parameters. Indicates the distortion factor. Let be the order of the beam. Represented as topological load, azimuth angle = , It is a constant real number and satisfies .

6. The radially polarized distorted partially coherent hyperbolic cosine beam generation system according to claim 5, characterized in that, The weighting function and kernel function required to construct the cross spectral density matrix of the radially polarized distorted partially coherent hyperbolic cosine beam are expressed as follows: ； ； Where the amplitude function for ； in Represents the position vector on the source plane. and It is a unitless vector that is not limited by dimensions. For the beam width, It is the Cartesian component of the wave electric field vector and the constant phase difference. The correlation coefficient between them.

7. The method for generating a radially polarized distorted partially coherent hyperbolic cosine beam according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: The semiconductor laser emits a laser beam, which passes through a beam expander to achieve the desired beam waist width; Step 2: The expanded beam is irradiated by the reflector to the spatial light modulator to generate a partially coherent modulated beam. The beam passes through the first thin lens, the pinhole aperture, and the second thin lens of the 4f filter unit to obtain a collimated and filtered first-order diffracted beam. This beam is the partially coherent beam that can image the target. Step 3: The formed beam is obtained by a polarizer to obtain a linearly polarized beam, and then converted into a twisted partially coherent radially polarized beam by a vortex plate. Step 4: The twisted coherent radially polarized beam is focused by a focusing lens and filtered by an analyzer orthogonal to the initial polarization direction. The light field distribution at different transmission distances is acquired using a charge-coupled device (CCD) to observe and control the beam.

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