CN113467117B - Temperature-controlled vector vortex light beam detector, preparation method thereof and detection device - Google Patents
Temperature-controlled vector vortex light beam detector, preparation method thereof and detection device Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title abstract description 5
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/132—Thermal activation of liquid crystals exhibiting a thermo-optic effect
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J11/00—Measuring the characteristics of individual optical pulses or of optical pulse trains
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
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- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1347—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
- G02F1/13718—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on a change of the texture state of a cholesteric liquid crystal
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Abstract
The embodiment of the invention discloses a temperature-controlled vector vortex beam detector, a preparation method thereof and a detection device. The vector vortex beam detector comprises a first liquid crystal box and a second liquid crystal box which are cascaded; the first liquid crystal box comprises a first substrate, a second substrate and a temperature-controlled first spin cholesteric liquid crystal layer, wherein the first substrate, the second substrate and the temperature-controlled first spin cholesteric liquid crystal layer are arranged oppositely; the second liquid crystal box comprises a third substrate, a fourth substrate and a temperature-controlled second spin cholesteric liquid crystal layer, wherein the third substrate, the fourth substrate and the temperature-controlled second spin cholesteric liquid crystal layer are arranged oppositely; the technical scheme of the embodiment of the invention can improve the device integration level, the detection efficiency and the detection waveband adjustability of vector vortex beam detection and realize the selective detection of circular polarization components.
Description
Technical Field
The embodiment of the invention relates to the technical field of microstructure liquid crystal and vector vortex light beams, in particular to a temperature-controlled vector vortex light beam detector, a preparation method thereof and a detection device.
Background
Vector vortex rotation has a helical phase and spatially non-uniform polarization distribution, exhibiting non-trivial coupling of spin angular momentum and orbital angular momentum. Vector vortex rotation has wide application in super-resolution microscopy, very large bandwidth communication and quantum information processing. The detection of vector vortex rotation is an indispensable key technology for the above applications. The vector vortex rotation is detected, and an effective scheme is to measure vortex topological charge carried by a right-handed circular polarization component and a left-handed circular polarization component of the vector vortex rotation respectively.
An interferometer-based interferometric method or a lens-based astigmatic transformation measurement method is suitable for measuring the topological charge of a vortex beam, but generally does not have circular polarization selectivity and is not beneficial to detecting two components of vector vortex rotation. The detection system based on the cascade spatial light modulator has the defects of complex light path and low efficiency. The metamaterial device has polarization dependence and is suitable for detecting vector vortex rotation, but the processing difficulty is high, and certain limitation exists in the adjustability of a detection waveband.
Disclosure of Invention
The embodiment of the invention provides a temperature-controlled vector vortex light beam detector, a preparation method thereof and a detection device, which are used for improving the device integration level, the detection efficiency and the detection waveband adjustability of vector vortex light beam detection and realizing selective detection of circular polarization components.
In a first aspect, an embodiment of the present invention provides a temperature-controlled vector vortex beam detector, including a first liquid crystal cell and a second liquid crystal cell, which are connected in cascade;
the first liquid crystal box comprises a first substrate, a second substrate and a temperature-controlled first spin cholesteric liquid crystal layer, wherein the first substrate and the second substrate are arranged oppositely, the temperature-controlled first spin cholesteric liquid crystal layer is positioned between the first substrate and the second substrate, a first alignment layer is arranged on one side, facing the second substrate, of the first substrate, and a second alignment layer is arranged on one side, facing the first substrate, of the second substrate;
the second liquid crystal box comprises a third substrate, a fourth substrate and a temperature-controlled second spin cholesteric liquid crystal layer, wherein the third substrate and the fourth substrate are arranged oppositely, the temperature-controlled second spin cholesteric liquid crystal layer is positioned between the third substrate and the fourth substrate, a third alignment layer is arranged on one side, facing the fourth substrate, of the third substrate, and a fourth alignment layer is arranged on one side, facing the third substrate, of the fourth substrate;
the first alignment layer, the second alignment layer, the third alignment layer and the fourth alignment layer have the same alignment direction, the first alignment layer, the second alignment layer, the third alignment layer and the fourth alignment layer are provided with control patterns with molecular directors in periodic gradient distribution, the control patterns form partial areas of a plurality of concentric circles, and the liquid crystal molecular directors are in periodic gradient distribution of 0-180 degrees along the radius direction of the concentric circles so as to form a curved gradient grating based on cholesteric liquid crystal.
Optionally, the distribution of the director of the liquid crystal molecules satisfies:
alpha represents the azimuth angle of the director of the liquid crystal molecules, lambda represents the grating period, y0Representing the relative displacement of the center of the control pattern to the center of the concentric rings.
Optionally, the first handedness cholesteric liquid crystal layer is a left-handed cholesteric liquid crystal layer, the second handedness cholesteric liquid crystal layer is a right-handed cholesteric liquid crystal layer, or the first handedness cholesteric liquid crystal layer is a right-handed cholesteric liquid crystal layer, and the second handedness cholesteric liquid crystal layer is a left-handed cholesteric liquid crystal layer.
Optionally, the first handedness cholesteric liquid crystal layer includes a temperature-controlled left-handed cholesteric liquid crystal material, and the second handedness cholesteric liquid crystal layer includes a temperature-controlled right-handed cholesteric liquid crystal material, or the first handedness cholesteric liquid crystal layer includes a temperature-controlled right-handed cholesteric liquid crystal material, and the second handedness cholesteric liquid crystal layer includes a temperature-controlled left-handed cholesteric liquid crystal material.
Optionally, the first liquid crystal cell further includes a first spacer located between the first substrate and the second substrate, where the first spacer is used to support the first substrate and the second substrate, and form a filling space of the first chiral cholesteric liquid crystal layer;
the second liquid crystal cell further comprises second spacer particles positioned between the third substrate and the fourth substrate, and the second spacer particles are used for supporting the third substrate and the fourth substrate and forming a filling space of the second spin-direction cholesteric liquid crystal layer;
the extending length of the first spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the first spin direction cholesteric liquid crystal layer along the direction vertical to the first substrate and the second substrate, and the extending length of the second spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the second spin direction cholesteric liquid crystal layer along the direction vertical to the third substrate and the fourth substrate.
Optionally, the first spacer particles include at least one of quartz microspheres and quartz columns, and the second spacer particles include at least one of quartz microspheres and quartz columns.
In a second aspect, an embodiment of the present invention further provides a temperature-controlled vector vortex light beam detection apparatus, including a vector vortex light beam generation unit, a first beam splitting unit, a second beam splitting unit, a first temperature control unit, a second temperature control unit, a first receiving screen, a second receiving screen, and any one of the above vector vortex light beam detectors;
the vector vortex light beam generating unit is used for outputting a vector vortex light beam to be measured;
the first beam splitting unit is arranged at the output end of the vector vortex beam generating unit, a first liquid crystal box of the vector vortex beam detector is positioned at the first output end of the first beam splitting unit, the first receiving screen is positioned at the second output end of the first beam splitting unit, and the light beam reflected by the first liquid crystal box is received by the first receiving screen after passing through the first beam splitting unit;
the second beam splitting unit is arranged between the first liquid crystal box and a second liquid crystal box of the vector vortex beam detector, the second liquid crystal box is positioned at a first output end of the second beam splitting unit, the second receiving screen is positioned at a second output end of the second beam splitting unit, and light beams reflected by the second liquid crystal box are received by the second receiving screen after passing through the second beam splitting unit;
the first temperature control unit is used for controlling the temperature of the first liquid crystal box so as to modulate the Bragg reflection band of the first liquid crystal box, and the second temperature control unit is used for controlling the temperature of the second liquid crystal box so as to modulate the Bragg reflection band of the second liquid crystal box.
In a third aspect, an embodiment of the present invention further provides a method for manufacturing a temperature-controlled vector vortex beam detector, where the method is used for any one of the vector vortex beam detectors, and includes:
providing a first substrate, a second substrate, a third substrate and a fourth substrate, wherein the first substrate and the second substrate are oppositely arranged, and the third substrate and the fourth substrate are oppositely arranged;
forming a first alignment layer on a side of the first substrate facing the second substrate, a second alignment layer on a side of the second substrate facing the first substrate, a third alignment layer on a side of the third substrate facing the fourth substrate, and a fourth alignment layer on a side of the fourth substrate facing the third substrate;
preparing a first spin-direction cholesteric liquid crystal layer controlled by temperature between the first substrate and the second substrate to form a first liquid crystal box, and preparing a second spin-direction cholesteric liquid crystal layer controlled by temperature between the third substrate and the fourth substrate to form a second liquid crystal box;
cascading the first liquid crystal box and the second liquid crystal box to form a vector vortex beam detector;
the first alignment layer, the second alignment layer, the third alignment layer and the fourth alignment layer have the same alignment direction, the first alignment layer, the second alignment layer, the third alignment layer and the fourth alignment layer have a control pattern with a periodically graded distribution of molecular directors, the control pattern forms partial areas of a plurality of concentric circles, and the liquid crystal molecular directors are periodically graded distribution from 0 to 180 degrees along the radius direction of the concentric circles so as to form a curved graded grating based on cholesteric liquid crystal.
Optionally, forming a first alignment layer on a side of the first substrate facing the second substrate, forming a second alignment layer on a side of the second substrate facing the first substrate, forming a third alignment layer on a side of the third substrate facing the fourth substrate, and forming a fourth alignment layer on a side of the fourth substrate facing the third substrate includes:
spin coating an alignment material on a side of the first substrate facing the second substrate, a side of the second substrate facing the first substrate, a side of the third substrate facing the fourth substrate, and a side of the fourth substrate facing the third substrate;
and annealing the first substrate, the second substrate, the third substrate and the fourth substrate which are coated with the orientation materials in a rotating mode to form a first orientation layer, a second orientation layer, a third orientation layer and a fourth orientation layer which have the same orientation direction.
Optionally, before preparing a first spin-cholesteric liquid crystal layer with temperature control between the first substrate and the second substrate to form a first liquid crystal cell, and preparing a second spin-cholesteric liquid crystal layer with temperature control between the third substrate and the fourth substrate to form a second liquid crystal cell, the method further includes:
forming first spacer particles between the first substrate and the second substrate, and forming second spacer particles between the third substrate and the fourth substrate;
the extending length of the first spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the first spin-direction cholesteric liquid crystal layer along the direction vertical to the first substrate and the second substrate, and the extending length of the second spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the second spin-direction cholesteric liquid crystal layer along the direction vertical to the third substrate and the fourth substrate.
The vector vortex beam detector with temperature control provided by the embodiment of the invention comprises a first liquid crystal box and a second liquid crystal box which are cascaded, wherein a first spin-to-cholesteric liquid crystal layer with temperature control in the first liquid crystal box is controlled through orientation layers of a first substrate and a second substrate, a second spin-to-cholesteric liquid crystal layer with temperature control in the second liquid crystal box is controlled through orientation layers of a third substrate and a fourth substrate, and a curved gradient grating based on first spin-to-cholesteric liquid crystal and a curved gradient grating based on second spin-to-cholesteric liquid crystal are formed. Cholesteric liquid crystals have bragg reflection bands: for the light beam with the wavelength in the reflection band, the cholesteric liquid crystal layer reflects the circular polarization component with the same rotation direction as the liquid crystal layer, and transmits the circular polarization component with the opposite rotation direction; light beams with wavelengths outside the reflection band are transmitted through the cholesteric liquid crystal layer. The reflected part is diffracted by the curved gradient grating to form light spots with a plurality of dark stripes, wherein the number and the direction of the dark stripes indicate the topological charge of vortex, and therefore the corresponding circular polarization component of the vector vortex light is detected; the transmitted portion passes through the liquid crystal layer without changing the nature of the vector vortex. By controlling the temperature of the first and second liquid crystal cells, the reflection bands of the first and second gyrotropic cholesteric liquid crystal layers can be controlled. When the wavelength of the incident vector vortex light beam is positioned in the reflection band, the corresponding component is detected; when the vector vortex beam wavelength is outside the reflection band, the corresponding component is transmitted without loss. Thereby achieving adjustability of the detection band and selective detection of the circularly polarized component.
Drawings
FIG. 1 is a schematic diagram of a Y-Z side structure of a temperature-controlled vector vortex beam detector according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a liquid crystal molecular director direction of a curved graded grating according to an embodiment of the present invention;
FIG. 3 is a graph showing the relationship between the temperature and the central wavelength of the reflection band of a left-handed cholesteric liquid crystal according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a reflection spectrum of a levorotatory cholesteric liquid crystal at 35.5 ℃ according to an embodiment of the present invention;
FIG. 5 is a schematic structural diagram of a temperature-controlled vector vortex beam detection apparatus according to an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating a detection result of a tunable waveband of a vector vortex beam according to an embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating the detection result of the circular polarization component selection of a vector vortex beam according to an embodiment of the present invention;
fig. 8 is a schematic flowchart of a method for manufacturing a temperature-controlled vector vortex beam detector according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. It should be noted that the terms "upper", "lower", "left", "right", and the like used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element. The terms "first," "second," and the like, are used for descriptive purposes only and not for purposes of limitation, and do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Fig. 1 is a schematic structural diagram of a Y-Z side surface of a temperature-controlled vector vortex beam detector according to an embodiment of the present invention, and referring to fig. 1, the vector vortex beam detector according to the embodiment includes a first liquid crystal cell 10 and a second liquid crystal cell 20 which are cascaded; the first liquid crystal box 10 comprises a first substrate 101, a second substrate 102 and a temperature-controlled first spin-direction cholesteric liquid crystal layer 103, wherein the first substrate 101 and the second substrate 102 are arranged oppositely, the temperature-controlled first spin-direction cholesteric liquid crystal layer 103 is positioned between the first substrate 101 and the second substrate 102, a first alignment layer 104 is arranged on one side, facing the second substrate 102, of the first substrate 101, and a second alignment layer 105 is arranged on one side, facing the first substrate 101, of the second substrate 102; the second liquid crystal cell 20 comprises a third substrate 201, a fourth substrate 202 and a temperature-controlled second spin-direction cholesteric liquid crystal layer 203, wherein the third substrate 201 and the fourth substrate 202 are arranged oppositely, the temperature-controlled second spin-direction cholesteric liquid crystal layer 203 is positioned between the third substrate 201 and the fourth substrate 202, a third alignment layer 204 is arranged on one side, facing the fourth substrate 202, of the third substrate 201, and a fourth alignment layer 205 is arranged on one side, facing the fourth substrate 202, of the fourth substrate 202; the first alignment layer 104, the second alignment layer 105, the third alignment layer 204 and the fourth alignment layer 205 have the same alignment direction, the first alignment layer 104, the second alignment layer 105, the third alignment layer 204 and the fourth alignment layer 205 have a control pattern with a periodically graded distribution of molecular directors, the control pattern forms a partial region of a plurality of concentric rings, and the liquid crystal molecular directors are periodically graded distribution from 0 to 180 degrees along the radial direction of the concentric rings to form a curved graded grating based on cholesteric liquid crystal.
The first spin-direction cholesteric liquid crystal layer 103 forms a spiral structure under the control of the first alignment layer 104 and the second alignment layer 105, the second spin-direction cholesteric liquid crystal layer 203 forms a spiral structure under the control of the third alignment layer 204 and the fourth alignment layer 205, the first spin-direction can be left-handed or right-handed, the second spin-direction can be right-handed or left-handed, optionally, the first spin-direction cholesteric liquid crystal layer 103 can be a left-handed cholesteric liquid crystal layer, the second spin-direction cholesteric liquid crystal layer 203 can be a right-handed cholesteric liquid crystal layer, or the first spin-direction cholesteric liquid crystal layer 103 can be a right-handed cholesteric liquid crystal layer, and the second spin-direction cholesteric liquid crystal layer 203 can be a left-handed cholesteric liquid crystal layer, which can be selected according to practical situations. The first alignment layer 104, the second alignment layer 105, the third alignment layer 204, and the fourth alignment layer 205 may include at least one of a photo-crosslinking material, a photo-degradable material, and a photo-cis-trans isomeric material. The materials are photo-alignment materials, and can generate physical or chemical reaction under the irradiation of ultraviolet polarized light to generate anisotropic surface acting force so as to induce the oriented arrangement of liquid crystal molecules. Fig. 2 is a schematic view of a director direction of liquid crystal molecules of a curved graded grating according to an embodiment of the present invention, referring to fig. 2, a control pattern forms a partial region of a plurality of concentric rings, and the directors of the liquid crystal molecules are distributed in a periodic gradient manner from 0 ° to 180 ° along a radial direction of the concentric rings, optionally, the distribution of the directors of the liquid crystal molecules satisfies:
alpha represents the azimuth angle of the director of the liquid crystal molecules, lambda represents the grating period, y0Showing the relative displacement of the center of the control pattern (the center of the pattern shown in figure 2) to the center of the concentric circles.
With continued reference to fig. 1, optionally, the first liquid crystal cell 10 further includes a first spacer 106 between the first substrate 101 and the second substrate 102, the first spacer 106 being configured to support the first substrate 101 and the second substrate 102 to form a filling space of the first spin-direction cholesteric liquid crystal layer 103; the second liquid crystal cell 20 further includes second spacer particles 206 between the third substrate 201 and the fourth substrate 202, the second spacer particles 206 are used for supporting the third substrate 201 and the fourth substrate 202 to form a filling space of the second chiral cholesteric liquid crystal layer 203; wherein the first spacer 106 has an extension length greater than or equal to 10 times the pitch of the liquid crystal molecules in the first gyrotropic cholesteric liquid crystal layer 103 in the direction perpendicular to the first substrate 101 and the second substrate 102, and the second spacer 206 has an extension length greater than or equal to 10 times the pitch of the liquid crystal molecules in the second gyrotropic cholesteric liquid crystal layer 203 in the direction perpendicular to the third substrate 201 and the fourth substrate 202, to form a curved graded grating having a sufficient reflectivity.
It is to be understood that fig. 1 only illustrates the position relationship of the first spacer particles 106 for supporting the first substrate 101 and the second substrate 102, and the second spacer particles 206 for supporting the third substrate 201 and the fourth substrate 202, but not the actual size and scale. Optionally, the first spacer particles 106 include at least one of quartz microspheres and quartz columns, and the second spacer particles 206 include at least one of quartz microspheres and quartz columns, which can be designed according to practical situations.
Exemplarily, fig. 3 is a relationship diagram of a reflection band center wavelength of a laevorotatory cholesteric liquid crystal controlled by temperature according to an embodiment of the present invention, and fig. 4 is a schematic reflection spectrum of the laevorotatory cholesteric liquid crystal at 35.5 ℃. Referring to fig. 3, the abscissa represents the temperature of the cholesteric liquid crystal layer in degrees celsius (° c); the ordinate represents the center wavelength of the bragg reflection band in nanometers (nm). As can be seen from FIG. 3, the liquid crystal layer was heated up from 26.7 ℃ to 35.5 ℃ with a blue shift of the center wavelength from 663nm to 546 nm; the corresponding relation can be repeated in the cooling process. Referring to fig. 4, the abscissa represents the wavelength in nanometers; the ordinate represents the reflectivity curve of the cholesteric liquid crystal layer. As can be seen from FIG. 4, the liquid crystal layer reflectance is close to 50% in the 528nm-568nm range. The temperature control performance of the vector vortex light beam detector provided by the embodiment of the invention is based on the property that the Bragg reflection band of the cholesteric liquid crystal is controlled by temperature and the circular polarization selective reflection of the light beam with the wavelength in the Bragg reflection band.
Fig. 3 is a diagram illustrating a relationship that the center wavelength of the reflection band of a cholesteric liquid crystal is controlled by temperature, and fig. 4 is a diagram illustrating a reflection spectrum of a cholesteric liquid crystal at a certain temperature, but not limiting the cholesteric liquid crystal material used in the present invention. In other embodiments, cholesteric liquid crystal materials having other optical properties may be selected according to actual needs.
According to the technical scheme of the embodiment, a first handedness cholesteric liquid crystal layer for controlling the temperature in a first liquid crystal box through the orientation layers of the first substrate and the second substrate, and a second handedness cholesteric liquid crystal layer for controlling the temperature in a second liquid crystal box through the orientation layers of the third substrate and the fourth substrate form a curved gradient grating based on first handedness cholesteric liquid crystal and a curved gradient grating based on second handedness cholesteric liquid crystal. Cholesteric liquid crystals have bragg reflection bands: for the light beam with the wavelength in the reflection band, the cholesteric liquid crystal layer reflects the circular polarization component with the same rotation direction as the liquid crystal layer, and transmits the circular polarization component with the opposite rotation direction; light beams with wavelengths outside the reflection band are transmitted through the cholesteric liquid crystal layer. The reflected part is diffracted by the curved gradient grating to form light spots with a plurality of dark stripes, wherein the number and the direction of the dark stripes indicate the topological charge of vortex, and therefore the corresponding circular polarization component of the vector vortex light is detected; the transmitted portion passes through the liquid crystal layer without changing the nature of the vector vortex. By controlling the temperature of the first and second liquid crystal cells, the reflection bands of the first and second gyrotropic cholesteric liquid crystal layers can be controlled. When the wavelength of the incident vector vortex light beam is positioned in the reflection band, the corresponding component is detected; when the vector vortex beam wavelength is outside the reflection band, the corresponding component is transmitted without loss. Thereby achieving adjustability of the detection band and selective detection of the circularly polarized component.
Based on the above technical solution, optionally, when the first rotation direction is left rotation and the second rotation direction is right rotation, the first rotation direction cholesteric liquid crystal layer 103 includes a temperature-controlled left-rotation cholesteric liquid crystal material, and the second rotation direction cholesteric liquid crystal layer 203 includes a temperature-controlled right-rotation cholesteric liquid crystal material, for example, the first rotation direction cholesteric liquid crystal layer 103 may include a nematic liquid crystal E7 mixed with a left-rotation chiral agent S811, the second rotation direction cholesteric liquid crystal layer 203 may include a nematic liquid crystal E7 mixed with a right-rotation chiral agent R811, or when the first rotation direction is right rotation and the second rotation direction is left rotation, the first rotation direction cholesteric liquid crystal layer 103 includes a temperature-controlled right-rotation cholesteric liquid crystal material, and the second rotation direction cholesteric liquid crystal layer 203 includes a temperature-controlled left-rotation cholesteric liquid crystal material, for example, the first rotation direction cholesteric liquid crystal layer 103 may include a nematic liquid crystal E7 mixed chiral agent R811, the second chiral cholesteric liquid crystal layer 203 may include nematic liquid crystal E7 compounded with a left-handed chiral agent S811.
Fig. 5 is a schematic structural diagram of a temperature-controlled vector vortex beam detection apparatus according to an embodiment of the present invention, and referring to fig. 5, the present embodiment includes a vector vortex beam generation unit 1, a first beam splitting unit 2, a second beam splitting unit 3, a first temperature control unit 4, a second temperature control unit 5, a first receiving screen 6, a second receiving screen 7, and any one of the vector vortex beam detectors 8 according to the above embodiments; the vector vortex light beam generating unit 1 is used for outputting a vector vortex light beam to be measured; the first beam splitting unit 2 is arranged at the output end of the vector vortex beam generating unit 1, the first liquid crystal box 10 of the vector vortex beam detector 8 is positioned at the first output end of the first beam splitting unit 2, the first receiving screen 6 is positioned at the second output end of the first beam splitting unit 2, and the light beam reflected by the first liquid crystal box 10 is received by the first receiving screen 6 after passing through the first beam splitting unit 2; the second beam splitting unit 3 is arranged between the first liquid crystal box 10 and a second liquid crystal box 20 of the vector vortex beam detector 8, the second liquid crystal box 20 is positioned at a first output end of the second beam splitting unit 3, the second receiving screen 7 is positioned at a second output end of the second beam splitting unit 3, and the light beam reflected by the second liquid crystal box 20 is received by the second receiving screen 7 after passing through the second beam splitting unit 3; the first temperature control unit 4 is used to control the temperature of the first liquid crystal cell 10 to modulate the bragg reflection band of the first liquid crystal cell 10, and the second temperature control unit 5 is used to control the temperature of the second liquid crystal cell 20 to modulate the bragg reflection band of the second liquid crystal cell 20.
Exemplarily, referring to fig. 5, the vector vortex beam generation unit 1 includes a laser light source 11, a polarizer 12, a first quarter wave plate 13, a first q-wave plate 14, a second quarter wave plate 15, and a second q-wave plate 16, which are sequentially arranged along a negative direction of a Z-axis (the Z-axis is the same as the Z-axis in fig. 1, and is perpendicular to a plane where the first substrate is located), and the first beam splitting unit 2 and the second beam splitting unit 3 are beam splitting prisms; and a first receiving screen 6 located in a direction perpendicular to the Z direction (X direction in fig. 5, the same as X direction in fig. 1) and parallel to the first beam splitting unit 2, and a second receiving screen 7 parallel to the second beam splitting unit 3. The arrangement of the optical devices is merely illustrative and is not a limitation on the embodiments of the present invention. In order to reduce stray light, a first diaphragm 91 and a second diaphragm 92 may also be provided in the optical path.
Wherein the laser light source 11 is used for generating a laser light beam, the propagation direction of which is exemplarily represented by an arrow in fig. 5. The polarizing plate 12 is used for converting the laser beam into linearly polarized light, the first quarter-wave plate 13 is used for converting the linearly polarized light into left-handed circularly polarized light, circularly polarized vortex light is generated through the first q-wave plate 14, linearly polarized vortex light is converted through the second quarter-wave plate 15, and vector vortex light is converted through the second q-wave plate 16. The topological charge values of the two circular polarization components of the vector vortex beam are determined by the topological parameters of the first q-wave plate 15 and the second q-wave plate 16. Half of the vector vortex beam is transmitted through the first beam splitting unit 2 and irradiated to the first liquid crystal cell 10. When the wavelength of the incident light irradiated on the first liquid crystal box 10 is in the bragg reflection band of the first handedness cholesteric liquid crystal layer (taking the right hand as an example in the embodiment), due to the bragg reflection function of the circular polarization selectivity of the cholesteric liquid crystal, the right hand circular polarization component is reflected and diffracted, and the first diffraction light spot is formed by irradiating the first beam splitting unit 2 on the first receiving screen 6; the vector vortex beam transmitted through the first liquid crystal cell 10 is half transmitted through the second beam splitting unit 3 to be irradiated to the second liquid crystal cell 20. Similarly, when the wavelength is in the reflection band of the second handedness cholesteric liquid crystal layer (the left-handed rotation is taken as an example in the embodiment), the left-handed circular polarization component is reflected and diffracted, and the reflected light is irradiated onto the second receiving screen 7 through the second beam splitting unit 3 to form a second diffraction spot. The part of the light beam that is not reflected by the second liquid crystal cell 20 is transmitted through the detector.
Fig. 6 is a schematic diagram illustrating a detection result of the adjustable wavelength band of a vector vortex beam according to an embodiment of the present invention. The temperature of the first liquid crystal box 10 and the temperature of the second liquid crystal box 20 are synchronously controlled, so that the right-handed cholesteric liquid crystal layer and the left-handed cholesteric liquid crystal layer have Bragg reflection bands in the same range, and the reflection bands contain the wavelength of a light beam to be detected, thereby realizing the adjustable detection of the wave band of the vector vortex light beam. Referring to fig. 5 and 6 together, abcd in fig. 6 represents a diffraction spot on the first receiving screen of fig. 5, and efgh in fig. 6 represents a diffraction spot on the second receiving screen of fig. 5. Changing the wavelength of the incident vector vortex light beam to 633nm (red), 600nm (orange), 580nm (yellow) and 550nm (green), synchronously controlling the temperature of the first liquid crystal box 10 and the second liquid crystal box 20, enabling the Bragg reflection bands of the left-handed cholesteric liquid crystal layer and the right-handed cholesteric liquid crystal layer to contain corresponding wavelengths, and completely detecting the topological charge information of the vector vortex light beam with the corresponding wavelengths. According to the direction and the number of the dark fringes of the diffraction spots, the topological charge of the right-handed circular polarization component of the vector vortex light beam is +2, and the topological charge of the left-handed circular polarization component is-2.
It should be noted that, the embodiment of the present invention only exemplarily shows wavelength tunable detection in a visible wavelength range, but is not limited to the vector vortex beam detector provided by the present invention, and in other embodiments, a suitable cholesteric material is prepared according to actual requirements, so that the vector vortex beam detector provided by the present invention is suitable for different wavelength ranges and has different temperature tunability.
For example, fig. 7 is a schematic diagram illustrating the selective detection result of the circular polarization component of the vector vortex beam according to the embodiment of the present invention. Referring to FIG. 7, a vector vortex beam at 633nm is incident with a topological charge of the right-hand circular polarization component of-3 and a topological charge of the left-hand circular polarization component of + 1. In a first aspect, the first liquid crystal cell 10 is controlled to have a temperature of 27.7 ℃ and the second liquid crystal cell to have a temperature of 35.5 ℃ such that the reflection band of the dextrorotatory cholesteric liquid crystal layer contains 633nm and the reflection band of the levorotatory cholesteric liquid crystal layer does not contain 633nm, and the topological charge of the right-handed circular polarization component of the vector vortex light is selectively detected. FIG. 7 a represents the diffraction spot on the first receiving screen of FIG. 5, with a visible topological charge of-3; in fig. 7 b represents the phenomenon on the second receiving screen of fig. 5, ideally without diffraction. At this point, the right-handed circularly polarized component is detected and the left-handed circularly polarized component is transmitted through the detector, i.e., the vortex beam with a topological charge of + 1. In a second aspect, the first liquid crystal cell 10 is controlled to 35.5 ℃ and the second liquid crystal cell 20 is controlled to 27.7 ℃ such that the reflection band of the levorotatory cholesteric liquid crystal layer contains 633nm and the reflection band of the dextrorotatory cholesteric liquid crystal layer does not contain 633nm, and the topological charge of the levorotatory circular polarization component of the vector vortex light is selectively detected. In fig. 7 c represents the phenomenon on the first receiving screen of fig. 5, ideally without diffraction; in fig. 7 d represents the diffraction spot on the second receiving screen of fig. 5, the visible topological charge is + 1. At this point, the left-handed circularly polarized component is detected and the right-handed circularly polarized component is transmitted through the detector, i.e., the vortex beam with a topological charge of-3.
Fig. 8 is a schematic flow chart of a method for manufacturing a temperature-controlled vector vortex beam detector according to an embodiment of the present invention, where this embodiment is applicable to manufacturing any one of the vector vortex beam detectors according to the foregoing embodiments, and referring to fig. 8, the method includes:
step S110, providing a first substrate, a second substrate, a third substrate and a fourth substrate, wherein the first substrate and the second substrate are disposed oppositely, and the third substrate and the fourth substrate are disposed oppositely.
The first substrate, the second substrate, the third substrate and the fourth substrate may be flexible substrates or rigid substrates with high light transmittance (greater than or equal to 85%). Illustratively, the first, second, third and fourth substrate materials may include quartz glass, ITO glass or ordinary glass, and the thickness of the substrate may be 1-2 mm.
Step S120, a first alignment layer is formed on a side of the first substrate facing the second substrate, a second alignment layer is formed on a side of the second substrate facing the first substrate, a third alignment layer is formed on a side of the third substrate facing the fourth substrate, and a fourth alignment layer is formed on a side of the fourth substrate facing the third substrate.
Optionally, forming a first alignment layer on a side of the first substrate facing the second substrate, forming a second alignment layer on a side of the second substrate facing the first substrate, forming a third alignment layer on a side of the third substrate facing the fourth substrate, and forming a fourth alignment layer on a side of the fourth substrate facing the third substrate includes:
spin coating the orientation material on the side of the first substrate facing the second substrate, the side of the second substrate facing the first substrate, the side of the third substrate facing the fourth substrate, and the side of the fourth substrate facing the third substrate;
and annealing the first substrate, the second substrate, the third substrate and the fourth substrate which are coated with the orientation materials in a rotating mode to form a first orientation layer, a second orientation layer, a third orientation layer and a fourth orientation layer which have the same orientation direction.
Illustratively, the spin coating process may include: firstly, the rotating speed is adjusted to 600-900 revolutions per minute, and the first spin coating time is controlled to be 5-10 seconds, so that the orientation material is uniformly distributed on the surface of the spin-coated substrate; then, the rotation speed is adjusted to 2500-3500 rpm, and the second spin coating time is controlled to be 30-50 seconds, so that the alignment material is coated.
The annealing process may include: the annealing atmosphere is air, the annealing temperature is 80-120 ℃, and the annealing time is 8-12 minutes.
It should be noted that the above rotation speed and spin coating time are only exemplary, and in other embodiments, the rotation speed and spin coating time may be adjusted according to actual requirements, so that the alignment film may control the alignment of the cholesteric liquid crystal molecules.
Step S130, a first spin-to-cholesteric liquid crystal layer with temperature control is prepared between the first substrate and the second substrate to form a first liquid crystal cell, and a second spin-to-cholesteric liquid crystal layer with temperature control is prepared between the third substrate and the fourth substrate to form a second liquid crystal cell.
And S140, cascading the first liquid crystal box and the second liquid crystal box to form the vector vortex beam detector.
The first orientation layer, the second orientation layer, the third orientation layer and the fourth orientation layer have the same orientation direction, the first orientation layer, the second orientation layer, the third orientation layer and the fourth orientation layer are provided with control patterns with molecular directors in periodic gradient distribution, the control patterns form partial areas of a plurality of concentric rings, and the liquid crystal molecular directors are in periodic gradient distribution of 0-180 degrees along the radius direction of the concentric rings to form the curved gradient grating based on the cholesteric liquid crystal. Illustratively, the period of a curved graded grating may be 100 μm, with the center of the pattern being displaced from the center of curvature by 1.6mm (in the positive Y-axis direction).
Optionally, before preparing a temperature-controlled first chiral cholesteric liquid crystal layer between the first substrate and the second substrate to form a first liquid crystal cell, and preparing a temperature-controlled second chiral cholesteric liquid crystal layer between the third substrate and the fourth substrate to form a second liquid crystal cell, the method further includes:
forming first spacer particles between the first substrate and the second substrate, and forming second spacer particles between the third substrate and the fourth substrate;
the extending length of the first spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the first spin-direction cholesteric liquid crystal layer along the direction vertical to the first substrate and the second substrate, and the extending length of the second spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the second spin-direction cholesteric liquid crystal layer along the direction vertical to the third substrate and the fourth substrate. Optionally, the first spacer particles include at least one of quartz microspheres and quartz columns, and the second spacer particles include at least one of quartz microspheres and quartz columns, which may be designed according to practical situations in implementation.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. The vector vortex beam detector with temperature control is characterized by comprising a first liquid crystal box and a second liquid crystal box which are cascaded;
the first liquid crystal box comprises a first substrate, a second substrate and a temperature-controlled first spin cholesteric liquid crystal layer, wherein the first substrate and the second substrate are oppositely arranged, the temperature-controlled first spin cholesteric liquid crystal layer is positioned between the first substrate and the second substrate, a first alignment layer is arranged on one side, facing the second substrate, of the first substrate, and a second alignment layer is arranged on one side, facing the first substrate, of the second substrate;
the second liquid crystal cell comprises a third substrate, a fourth substrate and a temperature-controlled second spin cholesteric liquid crystal layer, wherein the third substrate and the fourth substrate are arranged oppositely, the temperature-controlled second spin cholesteric liquid crystal layer is positioned between the third substrate and the fourth substrate, a third alignment layer is arranged on one side, facing the fourth substrate, of the third substrate, and a fourth alignment layer is arranged on one side, facing the third substrate, of the fourth substrate;
the first spin-direction cholesteric liquid crystal layer and the second spin-direction cholesteric liquid crystal layer have different spin directions, the first alignment layer, the second alignment layer, the third alignment layer and the fourth alignment layer have the same alignment direction, the first alignment layer, the second alignment layer, the third alignment layer and the fourth alignment layer are provided with control patterns with molecular directors in periodic gradient distribution, the control patterns form partial regions of a plurality of concentric rings, and the liquid crystal molecular directors are in periodic gradient distribution of 0-180 degrees along the radial direction of the concentric rings to form the curved gradient grating based on the cholesteric liquid crystal.
2. The vector vortex beam detector of claim 1 wherein said distribution of liquid crystal molecular directors satisfies:
alpha represents the azimuth angle of the director of the liquid crystal molecules, lambda represents the grating period, y0Representing the relative displacement of the center of the control pattern to the center of the concentric rings.
3. The vector vortex beam detector of claim 1 wherein said first handedness cholesteric liquid crystal layer is a levorotation cholesteric liquid crystal layer and said second handedness cholesteric liquid crystal layer is a dextrorotation cholesteric liquid crystal layer, or said first handedness cholesteric liquid crystal layer is a dextrorotation cholesteric liquid crystal layer and said second handedness cholesteric liquid crystal layer is a levorotation cholesteric liquid crystal layer.
4. The vector vortex beam detector of claim 3 wherein said first chiral cholesteric liquid crystal layer comprises temperature controlled left handed cholesteric liquid crystal material and said second chiral cholesteric liquid crystal layer comprises temperature controlled right handed cholesteric liquid crystal material, or said first chiral cholesteric liquid crystal layer comprises temperature controlled right handed cholesteric liquid crystal material and said second chiral cholesteric liquid crystal layer comprises temperature controlled left handed cholesteric liquid crystal material.
5. The vector vortex beam detector of claim 1 wherein said first liquid crystal cell further comprises a first spacer disposed between said first substrate and said second substrate, said first spacer configured to support said first substrate and said second substrate to form a filled space for said first chiral cholesteric liquid crystal layer;
the second liquid crystal cell further comprises second spacer particles positioned between the third substrate and the fourth substrate, and the second spacer particles are used for supporting the third substrate and the fourth substrate and forming a filling space of the second spin-direction cholesteric liquid crystal layer;
the extending length of the first spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the first spin direction cholesteric liquid crystal layer along the direction vertical to the first substrate and the second substrate, and the extending length of the second spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the second spin direction cholesteric liquid crystal layer along the direction vertical to the third substrate and the fourth substrate.
6. The vector vortex beam detector of claim 5 wherein said first spacer particles comprise at least one of quartz microspheres and quartz posts and said second spacer particles comprise at least one of quartz microspheres and quartz posts.
7. A vector vortex light beam detection device with temperature control is characterized by comprising a vector vortex light beam generation unit, a first beam splitting unit, a second beam splitting unit, a first temperature control unit, a second temperature control unit, a first receiving screen, a second receiving screen and the vector vortex light beam detector as claimed in any one of claims 1 to 6;
the vector vortex light beam generating unit is used for outputting a vector vortex light beam to be measured;
the first beam splitting unit is arranged at the output end of the vector vortex beam generating unit, a first liquid crystal box of the vector vortex beam detector is positioned at the first output end of the first beam splitting unit, the first receiving screen is positioned at the second output end of the first beam splitting unit, and the light beam reflected by the first liquid crystal box is received by the first receiving screen after passing through the first beam splitting unit;
the second beam splitting unit is arranged between the first liquid crystal box and a second liquid crystal box of the vector vortex beam detector, the second liquid crystal box is positioned at a first output end of the second beam splitting unit, the second receiving screen is positioned at a second output end of the second beam splitting unit, and light beams reflected by the second liquid crystal box are received by the second receiving screen after passing through the second beam splitting unit;
the first temperature control unit is used for controlling the temperature of the first liquid crystal box so as to modulate the Bragg reflection band of the first liquid crystal box, and the second temperature control unit is used for controlling the temperature of the second liquid crystal box so as to modulate the Bragg reflection band of the second liquid crystal box.
8. A method for preparing a temperature-controlled vector vortex beam detector, which is used for preparing the vector vortex beam detector as claimed in any one of claims 1 to 6, and is characterized by comprising the following steps:
providing a first substrate, a second substrate, a third substrate and a fourth substrate, wherein the first substrate and the second substrate are oppositely arranged, and the third substrate and the fourth substrate are oppositely arranged;
forming a first alignment layer on a side of the first substrate facing the second substrate, a second alignment layer on a side of the second substrate facing the first substrate, a third alignment layer on a side of the third substrate facing the fourth substrate, and a fourth alignment layer on a side of the fourth substrate facing the third substrate;
preparing a first spin-direction cholesteric liquid crystal layer controlled by temperature between the first substrate and the second substrate to form a first liquid crystal box, and preparing a second spin-direction cholesteric liquid crystal layer controlled by temperature between the third substrate and the fourth substrate to form a second liquid crystal box;
cascading the first liquid crystal box and the second liquid crystal box to form a vector vortex beam detector;
the first alignment layer, the second alignment layer, the third alignment layer and the fourth alignment layer have the same alignment direction, the first alignment layer, the second alignment layer, the third alignment layer and the fourth alignment layer are provided with control patterns with molecular directors in periodic gradient distribution, the control patterns form partial areas of a plurality of concentric circles, and the liquid crystal molecular directors are in periodic gradient distribution of 0-180 degrees along the radius direction of the concentric circles so as to form a curved gradient grating based on cholesteric liquid crystal.
9. The method according to claim 8, wherein forming a first alignment layer on a side of the first substrate facing the second substrate, forming a second alignment layer on a side of the second substrate facing the first substrate, forming a third alignment layer on a side of the third substrate facing the fourth substrate, and forming a fourth alignment layer on a side of the fourth substrate facing the third substrate comprises:
spin coating an alignment material on a side of the first substrate facing the second substrate, a side of the second substrate facing the first substrate, a side of the third substrate facing the fourth substrate, and a side of the fourth substrate facing the third substrate;
and annealing the first substrate, the second substrate, the third substrate and the fourth substrate which are coated with the orientation materials in a rotating mode to form a first orientation layer, a second orientation layer, a third orientation layer and a fourth orientation layer which have the same orientation direction.
10. The method according to claim 8, wherein before preparing the temperature-controlled first spin-to-cholesteric liquid crystal layer between the first substrate and the second substrate to form the first liquid crystal cell and preparing the temperature-controlled second spin-to-cholesteric liquid crystal layer between the third substrate and the fourth substrate to form the second liquid crystal cell, the method further comprises:
forming first spacer particles between the first substrate and the second substrate, and forming second spacer particles between the third substrate and the fourth substrate;
the extending length of the first spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the first spin-direction cholesteric liquid crystal layer along the direction vertical to the first substrate and the second substrate, and the extending length of the second spacer particles is larger than or equal to 10 times of the pitch of liquid crystal molecules in the second spin-direction cholesteric liquid crystal layer along the direction vertical to the third substrate and the fourth substrate.
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