A vector beam rotator, a preparation method and a vector beam rotating device

Abstract

The embodiment of the present application discloses a kind of vector light beam rotator, preparation method and vector light beam rotating device.Vector light beam rotator includes oppositely arranged first substrate, second substrate and cholesteric liquid crystal layer being arranged between first substrate and second substrate;Wherein, the side of first substrate towards second substrate is provided with first orientation layer, and the side of second substrate towards first substrate is provided with second orientation layer;First orientation layer, second orientation layer have the same uniform orientation direction, control and first orientation layer and second orientation layer adjacent liquid crystal molecule director are uniformly parallel arrangement, cholesteric liquid crystal layer is spirally arranged, and the short wave band edge neighborhood of Bragg reflection band formed by cholesteric liquid crystal layer includes the operating wavelength of vector light beam rotator.The technical scheme of the embodiment of the present application can improve the device integration of vector light beam rotation conversion, conversion range and operation simplicity, and realize dynamic controllable function.

Description

Technical Field

[0001] This invention relates to the fields of cholesteric liquid crystal and vector beam technology, and particularly to a vector beam rotator, its preparation method, and a vector beam rotating device. Background Technology

[0002] Vector beams, with their spatially non-uniform linear polarization distribution, have wide applications in super-resolution microscopy, optical communication, and optical information processing. The rotational transformation of a vector beam refers to the synchronous rotation of the linear polarization direction of its cross-section, resulting in a vector beam with a different polarization distribution, such as changing from radial polarization to angular polarization. This transformation is highly significant for the aforementioned applications.

[0003] In existing technologies, the rotational transformation of vector beams is mainly based on Faraday rotators, nonlinear optical devices, or metamaterial devices. These methods face problems such as complex equipment, narrow rotational transformation range, and high fabrication difficulty. Summary of the Invention

[0004] This invention provides a vector beam rotator, a fabrication method, and a vector beam rotation device to improve the device integration, transformation range, and ease of operation of vector beam rotation transformation, and to achieve dynamic controllability.

[0005] According to one aspect of the present invention, a vector beam rotator is provided, comprising a first substrate, a second substrate disposed opposite to each other, and a cholesteric liquid crystal layer disposed between the first substrate and the second substrate;

[0006] The first substrate has a first alignment layer on the side facing the second substrate, and the second substrate has a second alignment layer on the side facing the first substrate. The first alignment layer and the second alignment layer have the same uniform alignment direction. The first alignment layer and the second alignment layer respectively control the liquid crystal molecules adjacent to the first alignment layer and the second alignment layer to be uniformly parallel. The cholesteric liquid crystal layer is arranged in a spiral. The short-wavelength band edge neighborhood of the Bragg reflection band formed by the cholesteric liquid crystal layer includes the operating wavelength of the vector beam rotator.

[0007] Optionally, both the first alignment layer and the second alignment layer are light-controlled alignment layers.

[0008] Optionally, the photo-alignment layer includes at least one of a photocrosslinking material, a photodegradable material, and a photoinduced cis-trans isomer.

[0009] Optionally, the cholesteric liquid crystal layer includes a achiral nematic liquid crystal substrate and a chiral dopant, wherein the chiral dopant causes the achiral nematic liquid crystal substrate to be helically arranged.

[0010] Optionally, the chiral dopant includes a left-handed or right-handed dopant, which causes the non-chiral nematic liquid crystal bulk to be arranged in a left-handed or right-handed configuration.

[0011] Optionally, it also includes a spacer material located between the first substrate and the second substrate, the spacer material being used to support the first substrate and the second substrate to form a filling space for the cholesteric liquid crystal layer;

[0012] Wherein, along the direction perpendicular to the first substrate and the second substrate, the extension length of the spacer material is greater than or equal to 150 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

[0013] Optionally, the spacer material includes a polyester film.

[0014] According to another aspect of the present invention, a method for fabricating a vector beam rotator is provided, for fabricating the above-mentioned vector beam rotator, the method comprising:

[0015] A first substrate and a second substrate are provided, wherein the first substrate and the second substrate are disposed opposite to each other;

[0016] A first alignment layer is formed on the side of the first substrate facing the second substrate, and a second alignment layer is formed on the side of the second substrate facing the first substrate;

[0017] A cholesteric liquid crystal layer is prepared between the first substrate and the second substrate to form a vector beam rotator;

[0018] The first orientation layer and the second orientation layer have the same uniform orientation direction. The first orientation layer and the second orientation layer respectively control the liquid crystal molecules adjacent to the first orientation layer and the second orientation layer to be uniformly parallel. The cholesteric liquid crystal layer is arranged in a spiral. The short-wavelength band edge neighborhood of the Bragg reflection band formed by the cholesteric liquid crystal layer includes the operating wavelength of the vector beam rotator.

[0019] Optionally, before fabricating the cholesteric liquid crystal layer between the first substrate and the second substrate, the method further includes:

[0020] A spacer material is formed between the first substrate and the second substrate;

[0021] Wherein, along the direction perpendicular to the first substrate and the second substrate, the extension length of the spacer material is greater than or equal to 150 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

[0022] According to another aspect of the present invention, a vector beam rotating device is provided, comprising a laser source, a polarizer, a half-wave plate, a q-wave plate, a vector beam rotator as described above, an analyzer, and a receiving screen arranged sequentially along the optical axis;

[0023] The laser source is used to generate a laser beam, the polarizer is used to convert the laser beam into linearly polarized light, the half-wave plate is used to convert the linearly polarized light into linearly polarized light with any specified polarization direction, and the q-wave plate is used to generate a vector beam.

[0024] The vector beam irradiates the vector beam rotator at a preset incident angle, and the polarization direction of the incident vector beam undergoes synchronous rotation controlled by the incident angle, transforming it into a vector beam with a different polarization distribution.

[0025] The output vector beam is transmitted through the analyzer and received by the receiving screen to form a polarized beam pattern.

[0026] The vector beam rotation device further includes a rotation displacement stage, which is used to drive the vector beam rotator to rotate in order to change the incident angle.

[0027] The vector beam rotator provided in this embodiment of the invention includes a first substrate, a second substrate, and a cholesteric liquid crystal layer disposed between the first substrate and the second substrate. A first alignment layer is disposed on the side of the first substrate facing the second substrate, and a second alignment layer is disposed on the side of the second substrate facing the first substrate. The first and second alignment layers have the same uniform alignment direction. The first and second alignment layers respectively control the uniform parallel alignment of the liquid crystal molecules adjacent to the first and second alignment layers. The cholesteric liquid crystal layer is helically arranged, and the short-wavelength band edge neighborhood of the Bragg reflection band formed by the cholesteric liquid crystal layer contains the operating wavelength of the vector beam rotator. A vector beam with a wavelength located within the short-wavelength band edge neighborhood of the cholesteric liquid crystal's Bragg reflection band propagates through the cholesteric liquid crystal layer. The non-uniform linear polarization on its cross-section will undergo synchronous, same-angle increment rotation, the degree of which is controlled by the incident angle of the beam. By mechanically rotating the vector beam rotator, different incident angles are formed, and the emitted vector beam will undergo different degrees of rotation transformation. Its adjustable range covers at least one cycle, that is, the rotation angle of the local linear polarization direction is continuously adjustable from 0° to 180°. The vector beam rotator based on cholesteric liquid crystal provided in this invention can significantly improve the device integration, transformation range and ease of operation of vector beam rotation transformation, and achieve dynamic controllability.

[0028] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A schematic diagram of the xz side structure of a vector beam rotator provided in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram illustrating the working mode and transformation function of a vector beam rotator provided in an embodiment of the present invention;

[0032] Figure 3 A theoretical relationship diagram between optical rotation, polarization quality factor and wavelength of a vector beam rotator provided for an embodiment of the present invention;

[0033] Figure 4 A theoretical relationship diagram between the optical rotation degree and the incident angle of a vector beam rotator provided for an embodiment of the present invention;

[0034] Figure 5 Physical appearance and microscopic images of a vector beam rotator provided for embodiments of the present invention;

[0035] Figure 6 This is a schematic diagram of a vector beam rotation device provided in an embodiment of the present invention;

[0036] Figure 7 A schematic diagram illustrating the rotation transformation effect of a vector beam with a polarization order of +1 provided in an embodiment of the present invention;

[0037] Figure 8 A schematic diagram illustrating the rotational transformation effect of a vector beam with a polarization order of -1 provided in an embodiment of the present invention;

[0038] Figure 9 A schematic diagram illustrating the quantitative relationship between vector beam rotation transformation and incident angle control, provided in an embodiment of the present invention;

[0039] Figure 10 This is a schematic flowchart illustrating a method for fabricating a vector beam rotator according to an embodiment of the present invention. Detailed Implementation

[0040] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, 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 should fall within the scope of protection of the present invention.

[0041] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0042] Figure 1 This is a schematic diagram of the xz side structure of a vector beam rotator provided in an embodiment of the present invention, with reference to... Figure 1 The vector beam rotator includes a first substrate 10 and a second substrate 20 disposed opposite to each other, and a cholesteric liquid crystal layer 30 disposed between the first substrate 10 and the second substrate 20. A first alignment layer 11 is disposed on the side of the first substrate 10 facing the second substrate 20, and a second alignment layer 21 is disposed on the side of the second substrate 20 facing the first substrate 10. The first alignment layer 11 and the second alignment layer 21 have the same uniform alignment direction. The first alignment layer 11 and the second alignment layer 21 respectively control the liquid crystal molecules adjacent to the first alignment layer 11 and the second alignment layer 21 to be uniformly parallel aligned. The cholesteric liquid crystal layer 30 is helically arranged, and the short-wavelength band edge neighborhood of the Bragg reflection band formed by the cholesteric liquid crystal layer 30 contains the operating wavelength of the vector beam rotator.

[0043] In this embodiment, the first substrate 10 and the second substrate 20 can be selected as rigid or flexible substrates according to actual needs, and this embodiment of the invention does not limit this. The cholesteric liquid crystal layer 30 forms a helical structure under the control of the first alignment layer 11 and the second alignment layer 21. Specifically, the cholesteric liquid crystal layer 30 may optionally include a achiral nematic liquid crystal substrate and a chiral dopant, with the chiral dopant causing the achiral nematic liquid crystal substrate to be helically arranged. Optionally, the chiral dopant may include a left-handed or right-handed dopant to cause the achiral nematic liquid crystal substrate to be arranged left-handed or right-handed. That is, the cholesteric liquid crystal layer 30 can be a left-handed cholesteric liquid crystal layer or a right-handed cholesteric liquid crystal layer, and the choice can be made according to the actual situation. A reasonable ratio is used to control the wavelength range of the short-wavelength band edge neighborhood of the formed Bragg reflection band. For example, in one embodiment, a achiral nematic liquid crystal E7 is mixed with a left-handed chiral agent S5011 at a mixing ratio of 2.25 wt%, corresponding to a working wavelength of 632.8 nm. Optionally, both the first alignment layer 11 and the second alignment layer 21 are photo-controlled alignment layers. In specific implementations, the photo-controlled alignment layer may optionally include at least one of a photocrosslinking material, a photodegradable material, and a photoinduced cis-trans isomer. These materials are photo-controlled alignment materials that can undergo physical or chemical reactions under ultraviolet polarized light irradiation to generate anisotropic surface forces, thereby inducing the directional alignment of liquid crystal molecules.

[0044] Continue to refer to Figure 1 Optionally, the vector beam rotator further includes a spacer material 40 located between the first substrate 10 and the second substrate 20. The spacer material 40 is used to support the first substrate 10 and the second substrate 20 to form a filling space in the cholesteric liquid crystal layer 30. The extension length of the spacer material 40 along the direction perpendicular to the first substrate 10 and the second substrate 20 is greater than or equal to 150 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer 30, so as to form a sufficiently long beam propagation distance in the liquid crystal layer and provide sufficient transformation amount for the rotation transformation of the vector beam.

[0045] Understandable, Figure 1 This illustration is merely illustrative of the positional relationship of the spacer material 40 in supporting the first substrate 10 and the second substrate 20, and does not represent their actual dimensions or proportions. Optionally, the spacer material 40 may include, but is not limited to, a polyester film, and can be designed according to actual conditions in specific implementations. In one embodiment, the spacer material is a polyester film with a thickness of 70 μm.

[0046] For example, Figure 2This is a schematic diagram illustrating the operation and transformation function of a vector beam rotator according to an embodiment of the present invention. The vector beam rotator in this embodiment comprises a left-handed cholesteric liquid crystal layer, with its operating wavelength located in the short-wavelength band neighborhood of its Bragg reflection band, and the thickness of the liquid crystal layer being greater than or equal to 150 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer. A vector beam propagates along the positive z-axis through the vector beam rotator; the vector beam rotator rotates around the y-axis, causing the center normal of the substrate of the vector beam rotator to form a certain incident angle with the propagation direction of the vector beam; the director of the surface liquid crystal molecules is parallel to the x-axis. The incident vector beam has a gradually distributed linear polarization direction on its cross-section. The vector beam rotator causes the local linear polarization direction at each point on the cross-section to rotate synchronously and with the same angular increment, thereby transforming the emitted beam into a vector beam with a different polarization distribution. The rotation angle of the local linear polarization direction depends only on the absolute value of the incident angle and is independent of its sign. By adjusting the incident angle, the polarization rotation angle can be continuously varied from 0° to 180°, covering an entire transformation cycle.

[0047] For example, Figure 3 This diagram illustrates the theoretical relationship between optical rotation, polarization quality factor, and wavelength of a vector beam rotator, as provided in an embodiment of the present invention. Figure 4 This diagram illustrates the theoretical relationship between the optical rotation of a vector beam rotator and the incident angle, provided as an embodiment of the present invention, to explain the concept of the short-wavelength band edge neighborhood of the Bragg reflection zone. (Reference) Figure 3 The horizontal axis represents the wavelength of the incident light, in nanometers (nm); the left vertical axis represents the relative value of optical rotation; and the right vertical axis represents the polarization quality factor. Figure 3 The conclusion is based on the following preconditions: the cholesteric liquid crystal layer of the vector beam rotator is a levorotatory cholesteric liquid crystal layer with a pitch of 450 nm, an extension length of 155 times the pitch, and a Bragg reflection band of 680 nm to 770 nm at normal incidence; the incident beam direction is normal incidence; and the incident beam is uniformly linearly polarized. The magnitude of the optical rotation represents the relative magnitude of the rotation angle of the beam polarization direction; positive / negative optical rotation represents the beam polarization direction rotating in the positive / negative direction, respectively. The polarization quality factor is defined as (T... max -T min ) / (T max +T min ), where T max With T min These represent the transmittance when the analyzer is parallel or perpendicular to the principal polarization axis, respectively. A polarization quality factor of 1 represents ideal linear polarization; a polarization quality factor of 0 represents ideal circular polarization.

[0048] Continue to refer to Figure 3It should also be noted that for cholesteric liquid crystals, the optical effect of an obliquely incident beam with wavelength λ and incident angle θ is approximately equivalent to that of a normally incident beam with wavelength λ / cosθ. Therefore, increasing the incident angle while keeping the operating wavelength constant is equivalent to increasing the wavelength. Figure 3 As shown, in the short-wavelength region near the Bragg band, the optical rotation is highly dependent on wavelength; that is, changes in the incident angle effectively control the magnitude of the optical rotation, thereby controlling the rotational transformation of the vector beam's polarization state. Furthermore, the closer the operating wavelength is to the Bragg band, the steeper the optical rotation-wavelength curve, indicating higher sensitivity of the control. On the other hand, as the operating wavelength gets closer to the Bragg band, the polarization quality factor decreases from 1 to 0, meaning that the polarization state of the outgoing beam will gradually degenerate from an ideal linear polarization state to a circular polarization state. The vector beam should have a spatially non-uniformly distributed linear polarization state; if the outgoing beam cannot maintain its linear polarization state well and degenerates into circular polarization, then the function of the vector beam rotator is lost. In summary, as the operating wavelength gradually moves from the short-wavelength region outside the Bragg band closer to the Bragg band, the sensitivity and range of the rotational transformation controlled by the incident angle increase, but the polarization quality factor decreases. For example, Figure 3 The short-wavelength band edge neighborhood is defined as 593nm~648nm. When the working wavelength is in the short-wavelength band edge neighborhood, the incident angle θ can be adjusted from 0° to 30° to control the rotation transformation to cover at least one cycle, while the polarization quality factor is greater than or equal to 0.85.

[0049] refer to Figure 4 The horizontal axis represents the angle of incidence, and the vertical axis represents the relative value of optical rotation. For example, the operating wavelength is 633 nm (0.93 × the short-wavelength edge of the Bragg zonation band). Figure 3 Within the short-wavelength band edge neighborhood shown, the optical rotation is significantly controlled by the incident angle; the working wavelength of 544nm (0.80 × the short-wavelength band edge of the Bragg reflection band) is far from the Bragg reflection band, and the change in optical rotation with the incident angle is very limited.

[0050] It should be noted that, Figure 3 The theoretical relationship between the optical rotation, polarization quality factor, and wavelength of a vector beam rotator is shown only as an example. Figure 4 An exemplary diagram illustrating the theoretical relationship between optical rotation and incident angle is provided, along with an example of the range of the short-wavelength band edge neighborhood. However, this is not intended to limit the cholesteric liquid crystal material and structural parameters used in this invention. In other embodiments, cholesteric liquid crystal materials and structural parameters with other optical properties can be selected according to actual needs. When defining the short-wavelength band edge neighborhood, an appropriate trade-off should be struck between the contradictory factors of optical rotation and polarization quality factor, based on actual requirements.

[0051] For example, Figure 5The images provided in the left image show the physical appearance and microscopic images of a vector beam rotator according to an embodiment of the present invention. In the macroscopic image, the vector beam rotator is placed on a white light backlight. The thin strip-shaped area in the middle is the defect area, and the remaining highly transparent areas are the functional areas for vector beam rotation and transformation. The microscopic image of a local functional area is shown in the right image, using a reflective orthogonal polarization mode with a scale bar of 100 μm, revealing a uniform cholesteric liquid crystal planar texture.

[0052] The technical solution of this invention controls the cholesteric liquid crystal layer through the alignment layer of the first and second substrates, and controls the extension length of the cholesteric liquid crystal layer through the spacer material between the first and second substrates, forming a uniformly aligned cholesteric liquid crystal layer with an extension length greater than or equal to 150 times the pitch of the cholesteric liquid crystal, thus forming a vector beam rotator. When the wavelength of the incident beam is located in the vicinity of the short-wavelength band edge of the Bragg reflection band of the cholesteric liquid crystal, the beam will propagate through the cholesteric liquid crystal layer, and the polarization direction will rotate synchronously and with the same angular increment; the aforementioned rotation angle is controlled by the incident angle of the beam. By mechanically rotating the vector beam rotator, different incident angles are formed, and the outgoing vector beam will undergo different degrees of rotation transformation. Its adjustable range covers at least one cycle, that is, the rotation angle of the local linear polarization direction is continuously adjusted from 0° to 180°. With the polarization direction of the incident vector beam rotated in a controlled manner, the outgoing beam will be transformed into a vector beam with another polarization distribution, that is, the rotation transformation of the vector beam is realized. For example, a radially polarized vector beam is transformed into an angularly polarized vector beam. The vector beam rotator based on cholesteric liquid crystal provided in this invention can significantly improve the device integration, transformation range and ease of operation of vector beam rotation transformation, and achieve dynamic controllability.

[0053] Figure 6 This is a schematic diagram of a vector beam rotation device provided in an embodiment of the present invention, with reference to... Figure 6 The vector beam rotating device includes a laser source 1, a polarizer 2, a half-wave plate 3, a q-wave plate 4, a vector beam rotator 5, an analyzer 6, and a receiving screen 7 arranged sequentially along the optical axis. The laser source 1 generates a laser beam, the polarizer 2 converts the laser beam into linearly polarized light, the half-wave plate 3 converts the linearly polarized light into linearly polarized light with an arbitrary specified polarization direction, and the q-wave plate 4 generates a vector beam. The vector beam illuminates the vector beam rotator 5 at a preset incident angle, and the polarization direction of the incident vector beam undergoes synchronous rotation controlled by the incident angle, transforming it into a vector beam with a different polarization distribution. The output vector beam is transmitted through the analyzer 6 and received by the receiving screen 7, forming an analyzed light spot pattern. The vector beam rotating device also includes a rotational displacement stage 8, which drives the vector beam rotator 5 to rotate, thereby changing the incident angle.

[0054] Among them, reference Figure 6 The vector beam rotation device includes a direction along the positive z-axis (the z-axis is perpendicular to the z-axis). Figure 1 A vector beam generating unit 100 is formed by a laser source 1, a polarizer 2, a half-wave plate 3, and a q-wave plate 4 arranged sequentially along the z-axis (perpendicular to the plane of the first substrate); an output beam testing unit 200 is formed by an analyzer 6 and a receiving screen arranged sequentially along the positive z-axis; and a vector beam rotator 5 and a rotary displacement stage 8 are located between the output end of the vector beam generating unit 100 and the input end of the output beam testing unit 200. The rotary displacement stage 8 controls the vector beam rotator 5 to rotate around the y-axis (the y-axis is perpendicular to the plane of the first substrate). Figure 1 The optical components are aligned with the y-axis and perpendicular to the orientation direction of the first orientation layer to control the degree of rotation and transformation of the vector beam. The arrangement of the optical components is merely illustrative and not intended to limit the scope of this invention.

[0055] Laser source 1 is used to generate a laser beam. Figure 6 In the example, arrows represent the propagation direction of the laser beam. Polarizer 2 is used to convert the laser beam into linearly polarized light, and half-wave plate 3 is used to convert the linearly polarized light into linearly polarized light with an arbitrary specified polarization direction. The beam then passes through q-wave plate 4 to generate a vector beam. The polarization order of this vector beam is determined by the topological parameters of q-wave plate 4. The vector beam illuminates the vector beam rotator 5 at a certain incident angle, and almost all of it is transmitted, except for a small amount reflected by the glass substrate. When the wavelength of the incident light is in the vicinity of the short-wavelength band edge of the cholesteric liquid crystal Bragg reflection band, the polarization direction of the incident vector beam undergoes synchronous rotation controlled by the incident angle, transforming it into a vector beam with a different polarization distribution. The output vector beam passes through analyzer 6, whose transmission axis is parallel to the x-axis, and is received by receiving screen 7, forming an analyzed beam pattern.

[0056] For example, Figure 7 This is a schematic diagram illustrating the rotational transformation effect of a vector beam with a polarization order of +1, provided in an embodiment of the present invention. Figure 8 This is a schematic diagram illustrating the rotational transformation effect of a vector beam with a polarization order of -1, provided in an embodiment of the present invention. Figure 7 This corresponds to a vector beam with an initial wavelength of 632.8 nm and a polarization order of +1. Combined with... Figure 6 and Figure 7 , Figure 7 The diagram shows the analyzed spot patterns of vector beams that have undergone varying degrees of rotational transformation under different incident angles. Figure 6 The light spot pattern on the receiving screen of the output beam inspection unit. Figure 7The top row shows the experimentally measured beam spot after polarization analysis, while the bottom row shows the numerically simulated vector beam polarization distribution. The initial state of the vector beam has a radially distributed linear polarization direction. After polarization analysis, the beam spot is divided into two lobes by a vertical dark fringe. With incident angles set sequentially to 14.0°, 15.5°, 17.0°, and 19.1°, based on the changes in the orientation of the dark fringe after polarization analysis and the simulated polarization distribution, it can be seen that the vector beam undergoes different degrees of rotation transformation, with rotation angles of 0°, 22.5°, 45°, and 90° respectively. The non-uniform polarization on the cross-section of the vector beam undergoes essentially synchronous rotation with the same angular increment, thus achieving the desired controllable vector beam rotation transformation.

[0057] Similarly, see reference Figure 8 For example, the initial state is a vector beam with a wavelength of 632.8 nm and a polarization order of -1. Figure 8 The top-middle row shows the experimentally measured beam spot after polarization analysis, while the bottom row shows the numerically simulated vector beam polarization distribution. With the incident angles set sequentially to 14.0°, 15.5°, 17.0°, and 19.1°, based on the changes in the orientation of the dark fringes after polarization analysis, combined with the simulated polarization distribution, it can be seen that the vector beam underwent different degrees of rotational transformation, with rotation angles of 0°, 22.5°, 45°, and 90° in the polarization direction, respectively. Because... Figure 7 and Figure 8 The vector beams in the polarization array have opposite polarization orders, so under the same rotational transformation, the directions of change in the orientation of the dark fringes of the analyzed spot are exactly opposite. Combined with... Figure 7 and Figure 8 It can be seen that the vector beam rotator provided in the embodiments of the present invention can perform almost the same rotation transformation on different types of vector beams, and has universality.

[0058] For example, Figure 9 This is a schematic diagram illustrating the quantitative relationship between the vector beam rotation transformation and the incident angle, provided in an embodiment of the present invention. Figure 9 This corresponds to a vector beam with an initial wavelength of 632.8 nm and a polarization order of +1. Combined with... Figure 6 and Figure 9 , Figure 9 The horizontal axis represents the incident angle of the vector beam with respect to the vector beam rotator, and the vertical axis represents the azimuth angle of the dark fringe of the analyzed spot. Figure 9 The illustrations selectively show polarized spot images of partial states, with the images inverted for better observation, thus making dark fringes appear as bright fringes. For example, the incident angle is continuously adjusted from 0° to 28°, resulting in a range of over 360° for the azimuth angle of the dark fringes, covering at least two cycles. Figure 9 It is noted that the vector beam rotator provided in this embodiment of the invention exhibits a wide range of rotational transformations and has a simple control method.

[0059] It should be noted that the embodiments of the present invention only exemplify the rotation transformation of a 632.8nm vector beam controlled by the incident angle, but are not a limitation on the vector beam rotator provided in the embodiments of the present invention. In other embodiments, suitable cholesteric liquid crystal materials are prepared according to actual needs, so that the vector beam rotator provided in the embodiments of the present invention is applicable to vector beams of different wavelengths and has different incident angle controllability.

[0060] Figure 10 This is a schematic flowchart illustrating a method for fabricating a vector beam rotator according to an embodiment of the present invention, used to fabricate the vector beam rotator provided in the above embodiment. (Refer to...) Figure 10 The preparation method includes:

[0061] S110, A first substrate and a second substrate are provided, and the first substrate and the second substrate are disposed opposite to each other.

[0062] The first substrate and the second substrate can be flexible substrates or rigid substrates with high light transmittance (greater than or equal to 85%). For example, the materials of the first substrate and the second substrate may include quartz glass, ITO glass or ordinary glass, and the thickness of the substrate may be 1mm to 2mm.

[0063] S120, A first alignment layer is formed on the side of the first substrate facing the second substrate, and a second alignment layer is formed on the side of the second substrate facing the first substrate.

[0064] Optionally, a first alignment layer is formed on the side of the first substrate facing the second substrate, and a second alignment layer is formed on the side of the second substrate facing the first substrate, including:

[0065] The alignment material is spin-coated on the side of the first substrate facing the second substrate and on the side of the second substrate facing the first substrate;

[0066] Annealing is performed on a first substrate and a second substrate with spin-coated orientation material to form a first orientation layer and a second orientation layer with the same orientation direction.

[0067] For example, the spin coating process may include: first adjusting the rotation speed to 600~900 rpm and controlling the first spin coating time to 5~10 seconds to make the alignment material evenly distributed on the surface of the substrate to be spin coated; then adjusting the rotation speed to 2500~3500 rpm and controlling the second spin coating time to 30~50 seconds to make the alignment material spread.

[0068] The annealing process may include: annealing in air, annealing temperature of 80℃~120℃, and annealing time of 8~12 minutes.

[0069] It should be noted that the above-mentioned rotation speed and spin coating time are only illustrative examples. In other embodiments, the rotation speed and spin coating time can be adjusted according to actual needs so that the orientation film can control the orientation of cholesteric liquid crystal molecules.

[0070] S130. A cholesteric liquid crystal layer is prepared between the first substrate and the second substrate to form a vector beam rotator.

[0071] The first orientation layer and the second orientation layer have the same uniform orientation direction. The first orientation layer and the second orientation layer respectively control the liquid crystal molecules adjacent to the first orientation layer and the second orientation layer to be uniformly parallel. The cholesteric liquid crystal layer is arranged in a spiral. The short-wavelength band edge neighborhood of the Bragg reflection band formed by the cholesteric liquid crystal layer contains the working wavelength of the vector beam rotator.

[0072] The cholesteric liquid crystal layer to be prepared should have a short-wavelength band edge neighborhood of the Bragg reflection band that includes the operating wavelength of the vector beam rotator. Optionally, a chiral nematic liquid crystal substrate can be mixed with chiral dopants in a reasonable ratio to prepare a cholesteric liquid crystal, thereby controlling the short-wavelength band edge neighborhood of the formed Bragg reflection band to include the target operating wavelength.

[0073] Optionally, before fabricating the cholesteric liquid crystal layer between the first and second substrates, the method further includes:

[0074] A spacer material is formed between the first substrate and the second substrate;

[0075] In this embodiment, along the direction perpendicular to the first and second substrates, the extension length of the spacer material is greater than or equal to 150 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer. Optionally, the spacer material may include, but is not limited to, a polyester film, which can be designed according to the actual situation in specific implementations.

[0076] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A vector beam rotator, characterized in that, It includes a first substrate, a second substrate disposed opposite to each other, and a cholesteric liquid crystal layer disposed between the first substrate and the second substrate; The first substrate has a first alignment layer on the side facing the second substrate, and the second substrate has a second alignment layer on the side facing the first substrate. The first alignment layer and the second alignment layer have the same uniform alignment direction. The first alignment layer and the second alignment layer control the uniform parallel alignment of the liquid crystal molecules adjacent to the first alignment layer and the second alignment layer, respectively. The cholesteric liquid crystal layer is helically arranged. The short-wavelength band edge neighborhood of the Bragg reflection band formed by the cholesteric liquid crystal layer includes the working wavelength of the vector beam rotator. The thickness of the cholesteric liquid crystal layer is greater than or equal to 150 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

2. The vector beam rotator according to claim 1, characterized in that, Both the first alignment layer and the second alignment layer are light-controlled alignment layers.

3. The vector beam rotator according to claim 2, characterized in that, The photo-oriented layer includes at least one of photocrosslinking materials, photodegradable materials, and photoinduced cis-trans isomers.

4. The vector beam rotator according to claim 1, characterized in that, The cholesteric liquid crystal layer comprises a achiral nematic liquid crystal substrate and a chiral dopant, wherein the chiral dopant causes the achiral nematic liquid crystal substrate to be arranged in a helical pattern.

5. The vector beam rotator according to claim 4, characterized in that, The chiral dopant includes a left-handed or right-handed dopant, which causes the non-chiral nematic liquid crystal bulk to be arranged in a left-handed or right-handed manner.

6. The vector beam rotator according to claim 1, characterized in that, It also includes a spacer material located between the first substrate and the second substrate, the spacer material being used to support the first substrate and the second substrate, forming a filling space for the cholesteric liquid crystal layer; Wherein, along the direction perpendicular to the first substrate and the second substrate, the extension length of the spacer material is greater than or equal to 150 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

7. The vector beam rotator according to claim 6, characterized in that, The spacer material includes polyester film.

8. A method for fabricating a vector beam rotator, used to fabricate the vector beam rotator according to any one of claims 1 to 7, characterized in that, The preparation method includes: A first substrate and a second substrate are provided, wherein the first substrate and the second substrate are disposed opposite to each other; A first alignment layer is formed on the side of the first substrate facing the second substrate, and a second alignment layer is formed on the side of the second substrate facing the first substrate; A cholesteric liquid crystal layer is prepared between the first substrate and the second substrate to form a vector beam rotator; The first orientation layer and the second orientation layer have the same uniform orientation direction. The first orientation layer and the second orientation layer respectively control the liquid crystal molecules adjacent to the first orientation layer and the second orientation layer to be uniformly parallel. The cholesteric liquid crystal layer is arranged in a spiral. The short-wavelength band edge neighborhood of the Bragg reflection band formed by the cholesteric liquid crystal layer includes the operating wavelength of the vector beam rotator.

9. The preparation method according to claim 8, characterized in that, Before fabricating the cholesteric liquid crystal layer between the first substrate and the second substrate, the method further includes: A spacer material is formed between the first substrate and the second substrate; Wherein, along the direction perpendicular to the first substrate and the second substrate, the extension length of the spacer material is greater than or equal to 150 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

10. A vector beam rotation device, characterized in that, It includes a laser source, a polarizer, a half-wave plate, a q-wave plate, a vector beam rotator as described in any one of claims 1 to 7, a polarizer, and a receiving screen arranged sequentially along the optical axis; The laser source is used to generate a laser beam, the polarizer is used to convert the laser beam into linearly polarized light, the half-wave plate is used to convert the linearly polarized light into linearly polarized light with any specified polarization direction, and the q-wave plate is used to generate a vector beam. The vector beam irradiates the vector beam rotator at a preset incident angle, and the polarization direction of the incident vector beam undergoes synchronous rotation controlled by the incident angle, transforming it into a vector beam with a different polarization distribution. The output vector beam is transmitted through the analyzer and received by the receiving screen to form a polarized beam pattern. The vector beam rotation device further includes a rotation displacement stage, which is used to drive the vector beam rotator to rotate in order to change the incident angle.

Images