A method and apparatus for generating an optical element of a circular polarization detector, and an optical element

Abstract

The application relates to a method and device for generating an optical element of a circular polarization detector and the optical element, and the method comprises the following steps: adjusting reference light into first circular polarization light, adjusting signal light into first polarization state light, and constructing a first exposure polarization holographic interference field; generating a first intensity signal pattern in a polarization holographic recording sheet through the first exposure polarization holographic interference field; adjusting the reference light into second circular polarization light, adjusting the signal light into second polarization state light, and constructing a second exposure polarization holographic interference field; generating a second intensity signal pattern in the polarization holographic recording sheet through the second exposure interference field, generating a polarization multiplexing interference field at a preset position of the polarization holographic recording sheet, and preparing a holographic element. The optical element required by the circular polarization detector is prepared within several seconds, the polarization holographic recording sheet can adopt common holographic materials with polarization sensitivity, and the manufacturing cost is greatly reduced.

Description

Technical Field

[0001] This application relates to the field of optical technology, specifically to a method, apparatus, and optical element for generating optical elements of a circular polarization detector. Background Technology

[0002] Polarization, as an inherent and important property of light, plays a crucial role in scientific research. Polarized light has demonstrated remarkable capabilities in a wide range of applications, including optical communication, imaging, microscopy, and remote sensing. In particular, right-handed and left-handed circularly polarized light (CPL) exhibit completely different properties in absorption or certain reactions. CPL has been widely used in biosensing, optical imaging, and chiral component analysis. Therefore, an effective method to distinguish between left-handed and right-handed CPL in practical applications is important and urgent. For example, in polarization imaging, the first three Stokes parameters (S0, S1, S2) are related to the linear polarization component, while the fourth parameter S3 characterizes the circular polarization component of the object. Currently, many methods exist for distinguishing the directionality of circularly polarized beams. Traditional polarization measurement methods rely on the use of optical elements, such as the rotating polarizer and delay plate in HGBerry, G. Gabrielse, and A. Livingston's "Measurement of the Stokes parameters of Light" and RMAzzam, NMBashara, and SSBallard's "Ellipsometry and polarized light". The most common method used in optical laboratories is to use a combination of quarter-wave plate optical elements and polarizers, but this method is bulky and difficult to integrate.

[0003] Currently, various types of optical elements based on metasurfaces and metamaterials are widely studied to achieve circular polarization manipulation and detection, offering advantages such as flexible design, excellent performance, compact structure, and ease of miniaturization. Examples include pixelated metasurfaces in "High efficiency all-dielectric pixelated metasurface for near-infrared full-Stokes polarization detection" by C. Zhang, J. Hu, Y. Dong, A. Zeng, H. Huang, and C. Wang; and dielectric-based chiral metamaterials and dielectric-metal hybrid structures, as well as chiral metamaterials based on single or stacked planar plasmonic metasurfaces, in "Nature-inspired chiral metasurfaces for circular polarization detection and full-Stokes polarimetric measurements" by A. Basiri, X. Chen, J. Bai, P. Amrollahi, J. Carpenter, Z. Holman, C. Wang, and Y. Yao. Examples include nanorods with spatial orientation variations in "Circular polarization analyzer based on an Archimedean nano-pinholes array" by J. Zhang, Z. Guo, K. Zhou, L. Ran, L. Zhu, W. Wang, Y. Sun, F. Shen, J. Gao, and S. Liu; a metallic nanoantenna array in "Graphene circular polarization analyzer based on unidirectional excitation of plasmons" by B. Zhu, G. Ren, Y. Gao, B. Wu, C. Wan, and S. Jian; and metasurface holograms in "Helicity multiplexed broadband metasurface holograms" by D. Wen, F. Yue, G. Li, G. Zheng, K. Chan, S. Chen, M. Chen, KFLi, PWHWong, and KWCheah. However, the fabrication process is typically time-consuming and costly. Furthermore, fabricating large-area nanostructures leads to increased complexity and more stringent requirements in nanofabrication. Summary of the Invention

[0004] In view of the above problems, this application provides a method, apparatus and optical element for generating optical elements of a circular polarization detector, which solves the problems of long time and high cost in the manufacturing process of optical elements of existing circular polarization detectors.

[0005] To achieve the above objectives, the inventors provide a method for generating optical elements of a circular polarization detector, comprising the following steps:

[0006] The reference light is adjusted to the first rotation circularly polarized light, and the signal light is adjusted to the first polarization state light according to the interference angle between the reference light and the signal light to construct the first exposure polarization holographic interference field.

[0007] A first intensity signal image is recorded at a preset position on the polarization holographic recording film using the first exposure polarization holographic interference field;

[0008] The reference light is adjusted to a second-rotation circularly polarized light, and the signal light is adjusted to a second polarized state light according to the interference angle between the reference light and the signal light, thus constructing a second exposure polarization holographic interference field.

[0009] A second intensity signal image is recorded at a preset position on the polarization holographic recording film using a second exposure polarization holographic interference field;

[0010] Based on the zero reproduction effect in polarized holography, the first exposure polarized holographic interference field and the second exposure polarized holographic interference field are recorded at preset positions on the polarized holographic recorder to generate polarization multiplexing interference fields, thereby producing holographic elements.

[0011] Further optimization is achieved by making the first circularly polarized light right-handed, and the polarization state of the first polarized light is... The second axially polarized light is left-handed circularly polarized light, and the polarization state of the second polarized light is... , The interference angle between the reference light and the signal light;

[0012] Alternatively, the first circularly polarized light is left-handed circularly polarized light, and the polarization state of the first polarized light is... The second directionally polarized light is right-handed circularly polarized light, and the polarization state of the second polarized light is... , The angle between the reference light and the signal light is the interference angle.

[0013] Further optimization involves using a phenanthrenequinone-doped polymethyl methacrylate photopolymer.

[0014] Another technical solution is also provided: an optical element generation device for a circular polarization detector, comprising:

[0015] Laser, used to generate laser light;

[0016] A polarization beam splitter is used to split the laser beam generated by a laser into a signal beam and a reference beam.

[0017] The signal optical path is used to illuminate the polarized holographic recording film with signal light.

[0018] Reference optical path, used to illuminate the polarized holographic recording film with reference light;

[0019] A first quarter-wave plate is disposed in the signal light path and is used to adjust the polarization state of the signal light according to the interference angle between the reference light and the signal light.

[0020] A spatial light modulator, wherein the spatial light modulator is disposed in the signal optical path and is used to load an intensity signal map;

[0021] A first imaging lens is disposed in the signal optical path and is used to image the intensity signal image in the signal optical path onto a polarization holographic recording sheet.

[0022] The first half-wave plate is disposed in the reference optical path and is used to adjust the s-polarization of the reference light to p-polarization.

[0023] The second quarter-wave plate is placed in the reference optical path and is used to adjust the reference light into right-hand circularly polarized light or left-hand circularly polarized light.

[0024] Further optimization includes a beam expander, which is positioned between the laser and the polarizing beam splitter, and is used to expand the laser beam generated by the laser.

[0025] Further optimization includes a second half-wave plate, which is positioned between the laser and the polarization beam splitter. The second half-wave plate is used to adjust the intensity ratio of the signal light and the reference light.

[0026] Further optimization involves using a phenanthrenequinone-doped polymethyl methacrylate photopolymer.

[0027] Further optimizations also include a second imaging lens and a photosensitive element;

[0028] The second imaging lens is used to read the reproduced light on the polarized holographic record and to image it on the photosensitive element.

[0029] Further optimization involves using a complementary metal-oxide-semiconductor (CMOS) photosensitive element.

[0030] Further optimization includes a first reflector, which is used to perpendicularly project the signal light into the polarization holographic recording film;

[0031] The reference optical path includes a second mirror and a third mirror. The second mirror and the third mirror are used to direct the reference light into the polarization holographic recording film at a preset interference angle. The preset interference angle is the interference angle between the reference light and the signal light.

[0032] Another technical solution is provided: an optical element for a circular polarization detector, wherein the optical element is prepared by the optical element generation method of the circular polarization detector described above or by the optical element generation device of the circular polarization detector described above.

[0033] Unlike existing technologies, the above technical solution constructs a first exposure polarization holographic interference field by adjusting the reference light to a first-direction circularly polarized light and adjusting the signal light to a first polarization state based on the interference angle between the reference light and the signal light. A first intensity signal image is recorded at a preset position on the polarization holographic recording film using this first exposure polarization holographic interference field. The reference light is then adjusted to a second-direction circularly polarized light, and the signal light is adjusted to a second polarization state based on the interference angle between the reference light and the signal light, constructing a second exposure polarization holographic interference field. A second intensity signal image is recorded in the polarization holographic recording film using this second exposure polarization holographic interference field. Both exposure interference fields are recorded at the same position on the holographic recording material, generating a polarization-multiplexed interference field, i.e., a polarization-multiplexed hologram, ultimately yielding the holographic element. Based on the characteristics of the zero reproduction effect (NRE) and the functions to be achieved by the circular polarization detector, two sets of exposure interference fields are constructed. These two sets of interference fields can generate the required polarization interference pattern in the multiplexed polarization hologram and realize the detection of polarization direction / chirality. The optical components required for a circular polarization detector can be fabricated in seconds, and the polarization holographic recorder can use commonly used holographic materials with polarization sensitivity, greatly reducing manufacturing costs.

[0034] The above description of the invention is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the description and drawings, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is provided in conjunction with the specific embodiments and drawings of this application. Attached Figure Description

[0035] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of this application and other related content, and should not be considered as limitations on this application.

[0036] In the accompanying drawings of the instruction manual:

[0037] Figure 1 This is a schematic diagram of a method for generating optical elements of a circular polarization detector according to a specific embodiment.

[0038] Figure 2 This is a schematic diagram of a structure for generating optical elements of a circular polarization detector according to a specific embodiment.

[0039] Figure 3 This is a schematic diagram of an image obtained from an experiment where beams of different polarization states read diffraction light from a holographic element during the reconstruction stage, as described in a specific embodiment.

[0040] Figure 4 This is a schematic diagram illustrating the dependence of the diffraction normalized intensity on the fast axis rotation angle of the first quarter-wave plate in a specific implementation.

[0041] Figure 5 This is a schematic diagram illustrating the dependence of the diffraction intensity difference on the fast axis rotation angle of the first quarter-wave plate in a specific embodiment.

[0042] The reference numerals used in the above figures are explained as follows:

[0043] 1. Laser; 2. Beam expander; 3. Second half-wave plate; 4. Polarizing beam splitter; 5. Second mirror; 6. First half-wave plate; 7. Third mirror; 8. Second quarter-wave plate; 9. First mirror; 10. Spatial light modulator; 11. First imaging lens; 12. First quarter-wave plate; 13. Polarizing holographic recorder; 14. Second imaging lens; 15. Photosensitive element. Detailed Implementation

[0044] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0045] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0046] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0047] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0048] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0049] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0050] As understood in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0051] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0052] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0053] The zero reproduction effect (NRE) is a unique phenomenon in polarization holography, first observed and proposed by Todorov et al. At that time, NRE already took into account that the diffraction efficiency would drop to zero when the hologram was read using orthogonally polarized readout waves.

[0054] In the recording and reproduction process, the beams are distinguished by G and F, with the subscripts "+" and "-" representing the signal light and reference light, respectively. p-polarization is defined as a beam polarized in the xz plane perpendicular to wave propagation, while s-polarization is parallel to the y-axis. For orthogonal linear polarization, the unit vector can be expressed as: , , These represent the unit vectors of the signal light and the reference light, respectively.

[0055] During the recording phase, the volume polarization grating is formed by an incident angle of... Vector signal light and the angle of incidence is Vector reference light Writing material. Two beams of light... = The resultant electric field of the interference pattern in the symmetrical angular interference can be expressed as: u is a position vector. and These correspond to the signal light vector and the reference light vector, respectively. , .

[0056] Here, any polarization state can be written as: ,in, and Represents any real or imaginary number, with subscripts j=1,2,3, corresponding to the signal light, reference light, and readout light, respectively.

[0057] In the holographic reconstruction stage, light waves that satisfy the Bragg condition are used. The hologram is reconstructed by reading the wave. By combining new tensor theory and coupled-wave theory, the reconstructed light F+ can generally be calculated and described as:

[0058] ,

[0059] To detect and distinguish orthogonally circularly polarized (CPL) light, a polarization-multiplexed hologram was designed to record two sets of letters, such that the reconstructed image in the field of view of the optical system depends on the chirality of the incident circularly polarized light. In this polarization-multiplexed hologram, each hologram contains polarization information: right-handed circularly polarized light and left-handed circularly polarized light; and corresponding amplitude information, namely the abbreviations "R" and "L". When the hologram is reconstructed by different circularly polarized light, right-handed circular polarization (RCP) will diffract and reconstruct the letter "R", while left-handed circular polarization (LCP) will diffract and reconstruct the letter "L". Therefore, changing the polarization direction / chirality of the incident light will reconstruct different reconstructed signal images.

[0060] Please see Figure 1 This embodiment provides a method for generating optical elements of a circularly polarized detector, including the following steps:

[0061] Step S110: Adjust the reference light to first-rotation circularly polarized light, and adjust the signal light to first polarization state light according to the interference angle between the reference light and the signal light to construct the first exposure polarization holographic interference field;

[0062] Step S120: Record the first intensity signal image and its corresponding polarization state at a preset position on the polarization holographic recording film using the first exposure polarization holographic interference field;

[0063] Step S130: Adjust the reference light to the second-axis circularly polarized light, and adjust the signal light to the second polarization state light according to the interference angle between the reference light and the signal light to construct the second exposure polarization holographic interference field;

[0064] Step S140: Record the second intensity signal image and its corresponding polarization state at a preset position on the polarization holographic recording film using the second exposure polarization holographic interference field;

[0065] Step S150: Based on the zero reproduction effect in polarized holography, the first exposure polarized holographic interference field and the second exposure polarized holographic interference field are recorded at preset positions on the polarized holographic recorder to generate polarization multiplexing interference fields, thereby producing a holographic element.

[0066] Two exposure interference fields are recorded at the same location on the holographic recording material, generating a polarization-multiplexed interference field, i.e., a polarization-multiplexed hologram, ultimately yielding the holographic element. Based on the zero reproduction effect (NRE) in polarized holography and the functions required by the circular polarization detector, two sets of exposure interference fields are constructed. These two sets of interference fields can generate the desired polarization interference pattern in the multiplexed polarization hologram and achieve the detection of polarization rotation / chirality. The optical elements required for the circular polarization detector can be fabricated within seconds. The polarization holographic recording sheet can utilize commonly used holographic materials with polarization sensitivity, significantly reducing manufacturing costs.

[0067] In some embodiments, the first circularly polarized light is right-handed circularly polarized light, and the polarization state of the first polarized light is... The second axially polarized light is left-handed circularly polarized light, and the polarization state of the second polarized light is... , Let RCP be the interference angle between the reference light and the signal light. LCP is .

[0068] As shown in the table below:

[0069]

[0070] The table above summarizes the construction of the polarization holographic interference field used to prepare the circular polarization detector. Rows 1 and 2 correspond to sequential double exposure processes at the same recording position, with the reference light being an orthogonally circularly polarized beam and the readout light being either right-hand circularly polarized (RCP) or left-hand circularly polarized (LCP).

[0071] The interference angle θ is coupled with the polarization state of the signal light. In the last two columns of the reconstruction process, diffraction terms appear when the hologram is reconstructed using the same RCP or LCP beam as the reference light. However, when the hologram is reconstructed using polarized light orthogonal to the recording reference, the diffraction efficiency drops to zero; this is the zero reconstruction effect (NRE). Therefore, when a multiplexed polarization hologram is reconstructed by RCP or LCP light, light carrying a circularly polarized state is diffracted, while light carrying a circularly polarized state with the opposite rotation is effectively blocked by the NRE effect. This is the principle for distinguishing the rotational direction of circularly polarized beams. As shown in the table above, the NRE characteristics of the multiplexed polarization hologram are highly dependent on the rotational direction of the circularly polarized state of the reconstructed light, enabling this optical element to be used as a circular polarization detector to determine the rotational direction of circularly or elliptically polarized light.

[0072] In other embodiments, the first axially polarized light is left-handed circularly polarized light, and the polarization state of the first polarized light is... The second circularly polarized light is right-handed circularly polarized light, and the polarization state of the second polarized light is... , The angle between the reference light and the signal light is the interference angle.

[0073] In some embodiments, the polarization holographic recorder is a phenanthrenequinone-doped polymethyl methacrylate (PMMA) photopolymer. Polarization characteristics are universal in polarization holograms, and the polarization holographic recorder is not limited to a specific polarization-sensitive material. Commonly used holographic materials with polarization sensitivity can also be used in the fabrication of optical elements for circular polarization detectors. In this embodiment, the polarization holographic recorder uses a phenanthrenequinone-doped PMMA photopolymer as the recording polarization-sensitive material. The phenanthrenequinone-doped PMMA photopolymer (PQ / PMMA) material possesses photoinduced birefringence and polarization sensitivity, low fabrication cost, and robustness against photoinduced shrinkage.

[0074] A novel scheme for detecting the chirality of circularly polarized light based on the zero reproducibility effect (NRE) in polarization holography is presented. A circular polarization detector is a polarization-selective holographic recorder that can reproduce different images based on the chirality of the incident light. Using the optical element generation method of the circular polarization detector based on holographic exposure described in this application, a polarization holographic recorder can be fabricated within seconds. Theoretically, an analytical solution for the interference field that simultaneously satisfies the NRE effect in the multiplexed polarization hologram is obtained; experimentally, by constructing the interference field, the chirality of circularly polarized light (CPL) can be distinguished based on the different polarization properties of the reproduced light. By controlling the chirality of the incident light polarization, i.e., right-hand circularly polarized (RCP) or left-hand circularly polarized (LCP) light, two symmetrically distributed signal images can be alternately read from the same hologram. This scheme is based on the zero reproducibility effect (NRE) of orthogonal circularly polarized holography and is not limited by paraxial approximation or 90-degree interference angles and strict exposure conditions, making it more practical in applications and providing a feasible and convenient method for fabricating circular polarization detectors.

[0075] Furthermore, compared to nanostructures, polarization holography-based methods offer advantages in fabrication efficiency and convenience, providing a novel complementary solution to existing metamaterials technologies. Therefore, this approach holds immense potential for directly fabricating large-area circularly polarized detectors for integrated optics.

[0076] Please see Figure 2 In another embodiment, an optical element generation apparatus for a circularly polarized detector includes:

[0077] Laser 1, used to generate laser light;

[0078] Polarization beam splitter 4 is used to split the laser light generated by laser 1 into signal light and reference light;

[0079] The signal optical path is used to illuminate the polarized holographic recording film 13 with signal light;

[0080] Reference optical path, used to illuminate the polarized holographic recording film 13 with reference light;

[0081] A first quarter-wave plate 12 is disposed in the signal light path and is used to adjust the polarization state of the signal light according to the interference angle between the reference light and the signal light.

[0082] Spatial light modulator 10, shown, is disposed on the signal optical path and is used to load an intensity signal map;

[0083] The first imaging lens 11 is disposed in the signal light path and is used to image the intensity signal pattern in the signal light path onto the polarization holographic recording sheet 13.

[0084] The first half-wave plate 6 is disposed in the reference optical path and is used to adjust the s-polarization of the reference light to p-polarization.

[0085] The second quarter-wave plate 8 is disposed in the reference optical path and is used to adjust the reference light into right-hand circularly polarized light or left-hand circularly polarized light.

[0086] Laser 1 generates a collimated laser beam with a wavelength of 532 nm, which is split into a signal beam and a reference beam by a polarization beam splitter 4. In the signal beam path, a first quarter-wave plate 12 is used to adjust the linear polarization state of the signal light to elliptical or circular polarization. In the reference beam path, a first half-wave plate 6 is used to adjust the s-polarization state of the reference light to p-polarization, and a second quarter-wave plate 8 adjusts the reference light to elliptical or circular polarization. Different directions of circular polarization can be easily obtained by adjusting the angle between the horizontally linearly polarized beam and the fast axis of the quarter-wave plate. The diameter of the incident beam on the polarization holographic recording plate 13 is approximately 5 mm, and the intensity of the written beam is approximately 1. Each image is exposed for approximately 10 seconds. During the holographic reconstruction stage, the first quarter-wave plate 12 is used to adjust the polarization state of the reconstructed light wave.

[0087] The interference angle between the signal light and the reference light is randomly selected. In this embodiment, the outer angle of the recording material is 48°, and the refractive index of the polarization holographic recording sheet 13 is 1.5. According to Snell's law, the interference angle between the two recorded waves inside the material is 30°. As shown in the table above, the polarization state of the signal light is coupled to the interference angle θ. The elliptically polarized waves of the two recorded signals should be adjusted to... .

[0088] In the polarization multiplexing recording stage, the recording image window is divided into two parts, one half coupled to one type of chirality and the other half coupled to another type of chirality. Two sets of polarization holograms—a first intensity signal image and a second intensity signal image—are recorded sequentially at the same position on the recording material. During the first recording process, the reference light and signal light are adjusted to left-handed elliptically polarized and right-handed circularly polarized states, respectively. The intensity signal letter "R" (first intensity signal image) is loaded using a transmissive amplitude spatial light modulator 10, and the letter "R" is imaged onto the polarization holographic recording plate 13 through a first lens. During the second recording process, the polarization directions of the signal and reference beams are reversed by rotating the first quarter-wave plate 12 and the second quarter-wave plate 8, respectively, to record the other letter "L" (second intensity signal image). The interference fields from the two exposures are recorded at the same position on the holographic recording material, generating a polarization multiplexed interference field, i.e., a polarization multiplexed hologram, ultimately producing the holographic element.

[0089] In some embodiments, a beam expander 2 is also included, disposed between the laser 1 and the polarizing beam splitter 4. The beam expander 2 is used to expand the laser beam generated by the laser 1. The beam expander 2 is designed to increase the diameter of the parallel input beam to a larger parallel output beam.

[0090] In some embodiments, a second half-wave plate 3 is also included, which is disposed between the laser 1 and the polarization beam splitter 4. The second half-wave plate 3 is used to adjust the intensity ratio of the signal light and the reference light.

[0091] In some embodiments, the polarization holographic recorder 13 is a phenanthrenequinone-doped polymethyl methacrylate (PMMA) photopolymer. Polarization characteristics are universal in polarization holograms, and the polarization holographic recorder 13 is not limited to a specific polarization-sensitive material. Commonly used polarization-sensitive holographic materials can also be used in the fabrication of optical elements for circular polarization detectors. In this embodiment, the polarization holographic recorder 13 uses a phenanthrenequinone-doped PMMA photopolymer as the recording polarization-sensitive material. The phenanthrenequinone-doped PMMA photopolymer (PQ / PMMA) material possesses the characteristics of photoinduced birefringence and polarization sensitivity, low-cost manufacturing, and robustness against photoinduced shrinkage.

[0092] In some embodiments, a second imaging lens 14 and a photosensitive element 15 are also included;

[0093] The second imaging lens 14 is used to read the reproduced light on the polarized holographic recorder 13 and to image it on the photosensitive element 15.

[0094] The reproduced light on the polarized holographic recording film 13 is read through the second imaging lens 14 and the photosensitive element 15. The effect of the reproduced pattern in the prepared holographic element can be detected through the photosensitive element 15. The photosensitive element 15 is a complementary metal-oxide-semiconductor (CMOS). Like CCDs, CMOS is a semiconductor that can record changes in light in scanners. Currently, CMOS photosensitive devices are mainly used in a few business card scanners and document scanners. The manufacturing technology of CMOS is not much different from that of general computer chips. It mainly utilizes semiconductors made of silicon and germanium, allowing N-type (negative) and P-type (positive) semiconductors to coexist on the CMOS. The current generated by these two complementary effects can be recorded and interpreted as an image by the processing chip. In other embodiments, the photosensitive element 15 can also be a charge-coupled device (CCD).

[0095] In some embodiments, the signal optical path includes a first reflector 9, which is used to perpendicularly direct the signal light into the polarization holographic recording film 13;

[0096] The reference optical path includes a second reflector 5 and a third reflector 7. The second and third reflectors 5 and 7 are used to direct reference light into the polarization holographic recorder 13 at a preset interference angle, where the preset interference angle is the interference angle between the reference light and the signal light. By directing the signal light perpendicularly into the polarization holographic recorder 13 through the first reflector 9, the signal light can be diffracted perpendicularly, allowing the photosensitive element 15 to be placed perpendicularly behind the polarization holographic recorder 13, perpendicular to the signal light, facilitating the reading of the reproduced light. Based on the perpendicular insertion of the signal light into the polarization holographic recorder 13, the second and third reflectors 5 and 7 direct the reference light into the polarization holographic recorder 13 at a corresponding interference angle. In other embodiments, the signal light can also be directed into the polarization holographic recorder 13 at other angles, with corresponding reflector groups for the signal light and reference light configured according to the angle of the signal light's insertion. In other embodiments, the signal optical path and reference optical path can also be constructed using other types of mirror groups. As long as the polarization states of the signal light and reference light and the interference angle between the signal light and reference light are satisfied, and the recording material (polarization holographic recorder) used is polarization sensitive, the optical element of the circular polarization detector can be prepared.

[0097] In another embodiment, an optical element of a circular polarization detector is provided, wherein the optical element is prepared by the optical element generation method of the circular polarization detector in the above embodiments or by the optical element generation apparatus of the circular polarization detector in the above embodiments.

[0098] To demonstrate the performance of the fabricated circular polarization detector, the effect of the generated polarization holographic recorder was analyzed by measuring the change in diffraction signal intensity with different incident polarizations. When the incident polarization state was horizontal, the first quarter-wave plate 12 was rotated from 0° to 165° in 15° increments. Figure 3 The images shown are obtained from experiments where beams of light with different polarization states read the diffraction light of the holographic element during the reconstruction stage. The degree in the lower left corner of the figure represents the corresponding rotation angle of the first quarter-wave plate 12 relative to the horizontal, ranging from 0° to 165° in 15° steps. The polarization states of the incident light are: (a) and (g) are linearly polarized light, (d) is RCP, and (j) is LCP; (b), (c), (e), and (f) are right-handed elliptically polarized light, and (h), (i), (k), and (l) are left-handed elliptically polarized light. As the ellipticity of the incident polarized light changes, the intensity of the two signal images will increase and decrease. Generally, RCP and LCP constitute a set of orthogonal polarization basis vectors. The incident beam can be decomposed into a superposition of different orthogonal component ratios (such as linear and elliptically polarized light), so "R" and "L" will be reproduced simultaneously. Figure 3 In the diagram, (a) and (g) show the experimental results of horizontally linearly polarized incident light, where the fast axis of the first quarter-wave plate 12 is located in either a horizontal or vertical position. Since linearly polarized light contains equal proportions of RCP and LCP components, the letters "R" and "L" will be reproduced simultaneously.

[0099] Figure 3 Tables (d) and (j) show the diffraction results when the detector is illuminated with orthogonally rotated circularly polarized beams. When illuminated with the corresponding RCP or LCP beams, the recorded letters "R" and "L" are reproduced sequentially. Figure 3 As shown in (d), when the hologram is illuminated with RCP light, a clear signal image with very high fidelity and no distortion can be observed ("R" on the right). Similarly, when the incident light is LCP, the diffraction pattern is "L", as shown in (d). Figure 3 As shown in (j), experimental observations show that the reconstructed image is switchable, i.e., "R" or "L", depending on the polarization chirality of the incident light, thus enabling the detection of the polarization rotation direction of RCP and LCP beams.

[0100] When the readout light is converted to a left-handed elliptically polarized beam, the LCP component will dominate, with the letter "L" becoming more prominent. Figure 3 In (h), "R" is more prominent. Therefore, the intensities of "L" and "R" alternate, corresponding to the dominant trends of RCP and LCP. Thus, the directional polarization of the polarized beam can be intuitively determined directly by the relative intensities between the letters "R" and "L".

[0101] In addition, such as Figure 4The relationship between the normalized diffraction intensity and the rotation angle of the fast axis of the first quarter-wave plate 12 is shown. Figure 5 The relationship between the diffraction intensity difference and the rotation angle of the fast axis of the first quarter-wave plate 12 is shown. To characterize the performance of the circular polarization detector, the intensity evolution between the two reconstructed images under incident light illumination with different polarization states was also quantitatively analyzed. The intensity values ​​of the letters "R" and "L" can be obtained by summing the pixel intensities in the corresponding effective regions of the diffraction pattern captured by the CMOS (the intensity per unit pixel is lower than the maximum sensitivity threshold of the CMOS). Figure 4 The relationship between diffraction intensity and the rotation angle of the fast axis of the first quarter-wave plate 12 is shown, where the dots and solid lines represent experimental and simulated data, respectively.

[0102] The detection capability of the fabricated circularly polarized light detector can be evaluated by the polarization extinction difference, defined as the intensity difference between the readouts of orthogonally circularly polarized beams. To further characterize the performance of the circularly polarized detector, we calculated the intensity diffraction difference (DR - DL) of the reconstructed light obtained from readouts of different polarization states, where DR and DL represent the diffraction intensities of the letters "R" and "L" reconstructed by RCP and LCP light, respectively. Figure 5 As can be seen, the absolute difference between (DR and DL) is as high as 4000, which shows a very high polarization sensitivity. This further illustrates that the circular polarization detector prepared by this method can effectively distinguish between right-handed and left-handed circularly polarized light.

[0103] This scheme fabricates an optical element based on the zero reproduction effect (NRE) in polarization holography for detecting the rotation direction of circular polarization. The working principle of the circular polarization detector is theoretically presented, and the element is fabricated using exposures on the order of seconds. This scheme provides a simple fabrication method for circular polarization detectors.

[0104] Furthermore, the performance of the circular polarization detector was demonstrated through the readings of various reconstructed polarized beams. Experimental results show that changing the polarization direction of the incident polarization state leads to different reconstructed signal images. When RCP incident light diffracts into the letter "R" and LCP incident light diffracts into the letter "L", the rotation direction / chirality detection of circular polarization is intuitively achieved. Moreover, the rotation direction of the elliptically polarized beam can also be determined by the relative intensity of the reconstructed holographic letters "R" and "L".

[0105] Meanwhile, a polarization rotation direction detection method based on polarization multiplexing holography is also provided, which will show great potential in full Stokes parameter detection, material characterization, medical diagnosis and biomedical imaging.

[0106] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A method for generating optical elements of a circular polarization detector, characterized in that, Includes the following steps: The reference light is adjusted to the first rotation circularly polarized light, and the signal light is adjusted to the first polarization state light according to the interference angle between the reference light and the signal light to construct the first exposure polarization holographic interference field. A first intensity signal image is recorded at a preset position on the polarization holographic recording film using the first exposure polarization holographic interference field; The reference light is adjusted to a second-rotation circularly polarized light, and the signal light is adjusted to a second polarized state light according to the interference angle between the reference light and the signal light, thus constructing a second exposure polarization holographic interference field. A second intensity signal image is recorded at a preset position on the polarization holographic recording film using a second exposure polarization holographic interference field; Based on the zero reproduction effect in polarized holography, the first exposure polarized holographic interference field and the second exposure polarized holographic interference field are recorded at preset positions on the polarized holographic recorder to generate polarization multiplexing interference fields, thereby producing holographic elements.

2. The method for generating optical elements of a circularly polarized detector according to claim 1, characterized in that, The first circularly polarized light is right-handed circularly polarized light, and the polarization state of the first polarized light is... ; The second type of circularly polarized light is left-handed circularly polarized light, and the polarization state of the second polarized light is... , The interference angle between the reference light and the signal light; Alternatively, the first circularly polarized light is left-handed circularly polarized light, and the polarization state of the first polarized light is... ; The second type of axially polarized light is right-handed circularly polarized light, and the polarization state of the second polarized light is: , The angle between the reference light and the signal light is the interference angle.

3. An optical element generation device for a circular polarization detector, characterized in that, The apparatus is applied to the optical element generation method of the circular polarization detector as described in any one of claims 1-2, and the apparatus comprises: Laser, used to generate laser light; A polarization beam splitter is used to split the laser beam generated by a laser into a signal beam and a reference beam. The signal optical path is used to illuminate the polarized holographic recording film with signal light; The reference optical path is used to illuminate the polarized holographic recording film with reference light; A first quarter-wave plate is disposed in the signal light path and is used to adjust the polarization state of the signal light according to the interference angle between the reference light and the signal light. A spatial light modulator, wherein the spatial light modulator is disposed in the signal optical path and is used to load an intensity signal map; A first imaging lens is disposed in the signal light path and is used to image the intensity signal pattern in the signal light path onto the polarization holographic recording sheet. The first half-wave plate is disposed in the reference optical path and is used to adjust the s-polarization of the reference light to p-polarization. The second quarter-wave plate is placed in the reference optical path and is used to adjust the reference light into right-hand circularly polarized light or left-hand circularly polarized light; It also includes a beam expander, which is disposed between the laser and the polarizing beam splitter, and is used to expand the laser beam generated by the laser. It also includes a second half-wave plate, which is disposed between the laser and the polarization beam splitter. The second half-wave plate is used to adjust the intensity ratio of the signal light and the reference light.

4. The optical element generation apparatus for the circular polarization detector according to claim 3, characterized in that, The polarization holographic recording film is a phenanthrenequinone-doped polymethyl methacrylate photopolymer.

5. The optical element generation apparatus for the circular polarization detector according to claim 3, characterized in that, It also includes a second imaging lens and a photosensitive element; The second imaging lens is used to read the reproduced light on the polarized holographic record and to image it on the photosensitive element.

6. The optical element generation apparatus for a circular polarization detector according to claim 5, characterized in that, The photosensitive element is a complementary metal-oxide-semiconductor.

7. The optical element generation apparatus for the circular polarization detector according to claim 3, characterized in that, The signal optical path includes a first reflector, which is used to perpendicularly project the signal light into the polarized holographic recording film. The reference optical path includes a second mirror and a third mirror. The second mirror and the third mirror are used to direct the reference light into the polarization holographic recording film at a preset interference angle. The preset interference angle is the interference angle between the reference light and the signal light.

8. An optical element for a circular polarization detector, characterized in that, The optical element is prepared by the optical element generation method of the circular polarization detector according to any one of claims 1-2 or by the optical element generation apparatus of the circular polarization detector according to any one of claims 3-7.

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