CN211603602U - Liquid crystal optical vortex demultiplexer - Google Patents
Liquid crystal optical vortex demultiplexer Download PDFInfo
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- CN211603602U CN211603602U CN201922221468.4U CN201922221468U CN211603602U CN 211603602 U CN211603602 U CN 211603602U CN 201922221468 U CN201922221468 U CN 201922221468U CN 211603602 U CN211603602 U CN 211603602U
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Abstract
The utility model discloses a liquid crystal optical vortex demultiplexer, a serial communication port, include: a first transparent substrate for transmitting modulated light; the first orientation layer is arranged on one side of the first transparent substrate; the liquid crystal layer is arranged on one side, away from the first transparent substrate, of the first alignment layer; the second orientation layer is arranged on one side of the liquid crystal layer, which is far away from the first orientation layer; the second transparent substrate is arranged on one side, away from the liquid crystal layer, of the second alignment layer; the liquid crystal layer includes an alignment region including a phase correction region and a demultiplexing region, and a non-alignment region. Through the utility model provides a pair of liquid crystal light vortex demultiplexer sets up phase correction region and demultiplexing region in order to avoid because set up demultiplexing device and phase correction device respectively in same device, and both can't be parallel completely, coaxial and then cause demultiplexing device and phase correction subassembly to be not enough to the optical vortex correction precision.
Description
Technical Field
The utility model belongs to the technical field of optical communication and specifically relates to a liquid crystal optical vortex demultiplexer is related to.
Background
Currently, optical communication has long been the most dominant transmission means in information networks. In order to meet the increasing demand for information amount of human beings, new technologies are continuously emerging in the field of optical communication, wherein a technology of multiplexing various degrees of freedom and characteristics of light is a core key in optical communication. The mode division multiplexing technology using a set of mutually orthogonal spatial modes is also widely applied to free space and optical fiber communication, in the technology, spatial overlapping modes with the same frequency are coaxially transmitted in independent signal channels, mutual orthogonality and mutual noninterference between different modes are achieved, so that the spectral efficiency and the information capacity of an optical path are improved, and the parameters are proportional to the number of the transmitted modes. In the orthogonal mode concentration including the frequency, polarization, intensity and the like of light, the photon orbital angular momentum provides a high-dimensional state space for the light, and the information capacity in optical communication can be remarkably improved. While the beam with orbital angular momentum exhibits a characteristic azimuthal phase term exp (il phi), i.e. phi is the azimuthal coordinate in the plane perpendicular to the propagation direction and l is the azimuthal coordinate for each photon
Orbital angular momentum in units. Since the light beam carrying orbital angular momentum has a helical isophase surface, it is also called optical vortex. The most important two stages in the photon orbital angular momentum-based mode division multiplexing technology are the multiplexing stage and the demultiplexing stage of optical vortex, namely how to form collimated orthogonal optical vortex modes at the output end and how to demultiplex and identify them according to their orbital angular momentum information at the receiver after propagation.
However, diffractive optical elements manufactured by electron beam lithography or 3D laser printing tend to have disadvantages such as electrostatic loss and uneven phase change. The spiral coordinate conversion is applied to the phase design of the demultiplexer, but the scheme is realized by two spatial light modulators, so that the device integration precision is insufficient, and the defects of low resolution, high noise and the like exist.
SUMMERY OF THE UTILITY MODEL
The utility model discloses aim at solving one of the technical problem that exists among the prior art at least. Therefore, the utility model provides a liquid crystal light vortex demultiplexer can solve the device and can't be parallel completely, coaxial and then cause demultiplexing device and phase correction subassembly to the not enough technical problem of optical vortex correction precision.
The utility model discloses still provide a liquid crystal light vortex demultiplexer.
In a first aspect, an embodiment of the present invention provides a liquid crystal optical vortex demultiplexer: a first transparent substrate for transmitting modulated light;
the first orientation layer is arranged on one side of the first transparent substrate;
the liquid crystal layer is arranged on one side, far away from the first transparent substrate, of the first alignment layer;
the second alignment layer is arranged on one side, away from the first alignment layer, of the liquid crystal layer;
the second transparent substrate is arranged on one side, far away from the liquid crystal layer, of the second alignment layer;
the liquid crystal layer includes an alignment region including a phase correction region and a demultiplexing region, and a non-alignment region.
The utility model discloses liquid crystal optical vortex demultiplexer has following beneficial effect at least: the optical vortex correction device has the advantages that the optical vortex correction device has low crosstalk, clear light spots and less light spot overlapping due to spiral coordinate conversion, the orientation area has high resolution and is free of mechanical damage, and the phase correction area and the demultiplexing area are arranged in the same device, so that the problem that the demultiplexing device and the phase correction device cannot be completely parallel and coaxial due to the fact that the demultiplexing device and the phase correction device are arranged in the same device is solved, and further the optical vortex correction precision of the demultiplexing device and the phase correction component is insufficient.
According to other embodiments of the present invention, the liquid crystal optical vortex demultiplexer comprises a phase correction region disposed in a central region of the alignment region;
the demultiplexing area is arranged at the edge area of the orientation area and surrounds the phase correction area.
According to other embodiments of the present invention, the liquid crystal optical vortex demultiplexer is provided with a support structure between the first transparent substrate and the second transparent substrate.
According to other embodiments of the present invention, the liquid crystal optical vortex demultiplexer comprises a plurality of phase correction regions.
According to other embodiments of the present invention, the liquid crystal optical vortex demultiplexer comprises a plurality of demultiplexing regions.
Drawings
Fig. 1 is a schematic structural diagram of a liquid crystal optical vortex demultiplexer according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an optimized design system for the liquid crystal optical vortex demultiplexer of FIG. 1;
fig. 3A-3C are schematic diagrams of a liquid crystal layer in a liquid crystal optical vortex demultiplexer according to an embodiment of the present invention.
Reference numeral, 10, a first transparent substrate; 20. a first alignment layer; 30. a liquid crystal layer; 40. a second alignment layer; 50. a second transparent substrate; 31. a support structure; 32. an orientation region; 311. a phase correction area; 312. a demultiplexing area; 61. a controller; 62. a digital micromirror array; 63. a laser; 64. a beam splitter; 65. a polarizing plate; 66. and a beam reduction objective lens.
Detailed Description
The conception and the resulting technical effects of the present invention will be described clearly and completely with reference to the following embodiments, so that the objects, features and effects of the present invention can be fully understood. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and other embodiments obtained by those skilled in the art without inventive labor based on the embodiments of the present invention all belong to the protection scope of the present invention.
In the description of the present invention, if an orientation description is referred to, for example, the directions or positional relationships indicated by "upper", "lower", "front", "rear", "left", "right", etc. are based on the directions or positional relationships shown in the drawings, only for convenience of description and simplification of description, and it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. If a feature is referred to as being "disposed," "secured," "connected," or "mounted" to another feature, it can be directly disposed, secured, or connected to the other feature or indirectly disposed, secured, connected, or mounted to the other feature.
In the description of the embodiments of the present invention, if "a plurality" is referred to, it means one or more, if "a plurality" is referred to, it means two or more, if "greater than", "less than" or "more than" is referred to, it is understood that the number is not included, and if "more than", "less than" or "within" is referred to, it is understood that the number is included. If reference is made to "first" or "second", this should be understood to distinguish between features and not to indicate or imply relative importance or to implicitly indicate the number of indicated features or to implicitly indicate the precedence of the indicated features.
Referring to fig. 1, fig. 1 shows a schematic structural diagram of a liquid crystal optical vortex demultiplexer according to an embodiment of the present invention. As shown in fig. 1, a liquid crystal optical vortex demultiplexer includes: a first transparent substrate 10 for transmitting modulated light; a first alignment layer 20 disposed on one side of the first transparent substrate 10; the liquid crystal layer 30 is arranged on one side, far away from the first transparent substrate 10, of the first alignment layer 20; the second alignment layer 40 is arranged on one side of the liquid crystal layer 30 far away from the first alignment layer 20; the second transparent substrate 50 is arranged on one side of the second alignment layer 40 away from the liquid crystal layer 30; the liquid crystal layer 30 includes an alignment region including a phase correction region 311 and a demultiplexing region 312, and a non-alignment region.
The phase correction region 311 is disposed in the central region of the alignment region of the liquid crystal layer 30; the demultiplexing region 312 is disposed at an edge region of the alignment region of the liquid crystal layer 30 and surrounds the phase correction region 311.
A support structure 31 is disposed between the first transparent substrate 10 and the second transparent substrate 50.
The phase correction region 311 is spirally distributed; the demultiplexing regions 312 are symmetrically distributed.
The working principle of the liquid crystal optical vortex demultiplexer in this embodiment is further explained below.
Liquid crystals are anisotropic materials that have birefringent properties. When a light beam passes through the liquid crystal device, the light beam may generate a certain phase delay. When the phase retardation satisfies the half-wave condition, the geometric phase of the light beam (also referred to as Pancharatnam-Berry phase) can be modulated by the phase distribution of the liquid crystal device.
Because the phase distribution of the conventional demultiplexing device and the phase correction device is complex, the resolution requirement of the corresponding devices is higher, and the demultiplexing device and the phase correction device cannot be completely parallel and coaxially aligned in the practical application process.
Based on the characteristic that the optical vortex light spots are in annular intensity distribution, the liquid crystal optical vortex demultiplexer is manufactured by compositely designing the demultiplexing device and the phase correction device, and is provided with the phase correction area and the demultiplexing area so as to respectively perform phase correction and demultiplexing on the light beams through the same device.
And the diffraction characteristics of the phase modulation can be accurately and effectively analyzed through Jones matrix calculation. For a liquid crystal demultiplexer device (liquid crystal half-wave plate) with a constant α (i.e., the angle between the optical axis of the liquid crystal molecules and the polarization vector of the incident light), the jones matrix is:
alpha is a fixed constant, namely the arrangement directions of liquid crystal molecules in the liquid crystal demultiplexing device are completely the same, so that the linear polarization vector of an incident beam is rotated by 2 alpha. Due to the natural smoothness of the liquid crystal molecular orientation variation curve, when a two-dimensional function α (x, y) is used instead of the constant α, the liquid crystal molecular distribution is patterned and the geometric phase of the light beam can be modulated. Therefore, the liquid crystal optical vortex demultiplexer with high efficiency and strong demultiplexing performance can be prepared by arranging the demultiplexing area in the liquid crystal optical vortex demultiplexer and applying the demultiplexer phase function based on the spiral conversion.
Unlike log-polar transformation, which maps circles to parallel lines, helical transformation provides N-fold phase shift for the wavefront of the output light through helical to linear mapping to extend the periodic phase of the input orbital angular momentum.
The phase function of a liquid crystal optical vortex demultiplexer derived by a logarithmic spiral (where a >0, s is any integer) is as follows:
wherein a and β are scale parameters,
is the wave vector of the light beam. And r is a radial coordinate and theta is an angular coordinate to represent a polar coordinate of the position of the logarithmic spiral, so the theta threshold is not limited to 0,2 pi). The polar coordinates (r, θ) are related to the cartesian coordinates (x, y) by:
r＝(x2+y2)1/2，θ＝θ0+2mπ (3)
wherein, theta0Is a standard polar coordinate and can be expressed as
The integer m represents the ordinal number of the helix and can be expressed as:
r0the point θ representing the spiral is 0, which is the distance of (0,0) mapped onto the output plane.
The phase function on the demultiplexing area of the input plane is the phase required to map the input plane's vortex phase to the linear phase after the beam propagation distance d. (u, v) are cartesian coordinates on the output plane, and the phase correction zone is placed on this plane from the demultiplexing component d to correct for phase distortions caused by propagation. The phase function of the phase correction zone is as follows:
the optical vortex first passes through the demultiplexing region (while the input intensity of the phase correction region is zero), and then the light beam is reflected by the mirror and illuminates the phase correction region of the liquid crystal optical vortex demultiplexer. The overall phase function for this compact configuration is therefore a combination of the phase functions in equations (2) and (5), as shown below:
αsum＝α(x,y)θ(ρ-ρ1)+α(u,v)θ(ρ1-ρ) (6)
ρ is the radius of the phase correction region, and θ is the hervesaide function (for x >0, otherwise θ (x) ═ 0).
Referring to FIGS. 3A-3C, phase distribution diagrams of alignment regions of a liquid crystal layer in a liquid crystal optical vortex demultiplexer are shown. The liquid crystal layer alignment area comprises a phase correction area and a demultiplexing area, wherein the phase correction area is arranged in the central area of the liquid crystal layer alignment area, and the demultiplexing area is arranged in the edge area of the liquid crystal layer alignment area and surrounds the phase correction area.
The demultiplexing area is used for demultiplexing the optical vortex, and the phase correction area is used for performing phase correction on the optical vortex after demultiplexing.
Based on the characteristic that the optical vortex light spots are in annular intensity distribution, the liquid crystal optical vortex demultiplexer is manufactured by compositely designing the demultiplexing device and the phase correction device, and is provided with the phase correction area and the demultiplexing area so as to respectively perform phase correction and demultiplexing on the light beams through the same device.
Referring to fig. 2 and fig. 3A to fig. 3C, a phase correction region 311 and a demultiplexing region 312 are disposed in the liquid crystal layer 30, specifically, the micro-mirror array miniature projection exposure system aligns the first alignment layer 20 and the second alignment layer 40 to pattern the first alignment layer 20 and the second alignment layer 40. A hollow interlayer is provided in advance between the first alignment layer 20 and the second alignment layer 40 in which the support structure 31 is provided.
After the first alignment layer 20 and the second alignment layer 40 are patterned, the hollow interlayer is filled with liquid crystal, and the alignment regions 32 in the liquid crystal layer 30 form preset patterns of the phase correction regions 311 and the demultiplexing regions 312.
The micro-lenses in the digital micro-lens array 62 are modulated by the controller 61 according to the preset pattern information, so that the surface of the digital micro-lens array 62 forms a preset pattern. The laser 63 generates a laser beam, which is incident on the beam splitter 64 and partially reflected to the surface of the digital micromirror array 62 to form a laser beam carrying predetermined pattern information. The laser beam carrying the predetermined pattern information is reflected on the surface of the micromirror array 62 and propagates back to the polarizer 65. The polarizing plate 65 modulates the polarization state of the laser beam carrying the preset pattern information to form a target modulated beam. The objective lens 66 focuses the target modulated light beam such that the converged light beam of the target modulated light beam crosses the first and second photo- alignment layers 10 and 40, and simultaneously modulates the alignment patterns of the first and second photo- alignment layers 10 and 40.
Based on the characteristic that the optical vortex light spots are in annular intensity distribution, the liquid crystal optical vortex demultiplexer is manufactured by compositely designing the demultiplexing device and the phase correction device, and is provided with the phase correction area and the demultiplexing area so as to respectively perform phase correction and demultiplexing on the light beams through the same device.
And the diffraction characteristics of the phase modulation can be accurately and effectively analyzed through Jones matrix calculation. For a liquid crystal demultiplexer device (liquid crystal half-wave plate) with a constant α (i.e., the angle between the optical axis of the liquid crystal molecules and the polarization vector of the incident light), the jones matrix is:
alpha is a fixed constant, namely the arrangement directions of liquid crystal molecules in the liquid crystal demultiplexing device are completely the same, so that the linear polarization vector of an incident beam is rotated by 2 alpha. Due to the natural smoothness of the liquid crystal molecular orientation variation curve, when a two-dimensional function α (x, y) is used instead of the constant α, the liquid crystal molecular distribution is patterned and the geometric phase of the light beam can be modulated. Therefore, the liquid crystal optical vortex demultiplexer with high efficiency and strong demultiplexing performance can be prepared by arranging the demultiplexing area in the liquid crystal optical vortex demultiplexer and applying the demultiplexer phase function based on the spiral conversion.
Unlike log-polar transformation, which maps circles to parallel lines, helical transformation provides N-fold phase shift for the wavefront of the output light through helical to linear mapping to extend the periodic phase of the input orbital angular momentum.
The phase function of a liquid crystal optical vortex demultiplexer derived by a logarithmic spiral (where a >0, s is any integer) is as follows:
wherein a and β are scale parameters,
is the wave vector of the light beam. And r is a radial coordinate and theta is an angular coordinate to represent a polar coordinate of the position of the logarithmic spiral, so the theta threshold is not limited to 0,2 pi). The polar coordinates (r, θ) are related to the cartesian coordinates (x, y) by:
r＝(x2+y2)1/2，θ＝θ0+2mπ (3)
wherein, theta0Is a standard polar coordinate and can be expressed as
The integer m represents the ordinal number of the helix and can be expressed as:
r0the point θ representing the spiral is 0, which is the distance of (0,0) mapped onto the output plane.
The phase function on the demultiplexing area of the input plane is the phase required to map the input plane's vortex phase to the linear phase after the beam propagation distance d. (u, v) are cartesian coordinates on the output plane, and the phase correction zone is placed on this plane from the demultiplexing component d to correct for phase distortions caused by propagation. The phase function of the phase correction zone is as follows:
the optical vortex first passes through the demultiplexing region (while the input intensity of the phase correction region is zero), and then the light beam is reflected by the mirror and illuminates the phase correction region of the liquid crystal optical vortex demultiplexer. The overall phase function for this compact configuration is therefore a combination of the phase functions in equations (2) and (5), as shown below:
αsum＝α(x,y)θ(ρ-ρ1)+α(u,v)θ(ρ1-ρ) (6)
ρ is the radius of the phase correction region, and θ is the hervesaide function (for x >0, otherwise θ (x) ═ 0).
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art. Furthermore, the embodiments of the present invention and features of the embodiments may be combined with each other without conflict.
Claims (5)
1. A liquid crystal optical vortex demultiplexer comprising:
a first transparent substrate for transmitting modulated light;
the first orientation layer is arranged on one side of the first transparent substrate;
the liquid crystal layer is arranged on one side, far away from the first transparent substrate, of the first alignment layer;
the second alignment layer is arranged on one side, away from the first alignment layer, of the liquid crystal layer;
the second transparent substrate is arranged on one side, far away from the liquid crystal layer, of the second alignment layer;
the liquid crystal layer includes an alignment region including a phase correction region and a demultiplexing region, and a non-alignment region.
2. The liquid crystal optical vortex demultiplexer of claim 1, wherein the phase correction region is disposed in a central region of the alignment region;
the demultiplexing area is arranged at the edge area of the orientation area and surrounds the phase correction area.
3. The liquid crystal optical vortex demultiplexer of claim 1, wherein a support structure is disposed between the first transparent substrate and the second transparent substrate.
4. The liquid crystal optical vortex demultiplexer of claim 2 wherein the phase correction regions are distributed in a spiral.
5. The liquid crystal optical vortex demultiplexer of claim 2, wherein the demultiplexing regions are symmetrically distributed.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110927856A (en) * | 2019-12-12 | 2020-03-27 | 华南师范大学 | Liquid crystal optical vortex demultiplexer and manufacturing method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110927856A (en) * | 2019-12-12 | 2020-03-27 | 华南师范大学 | Liquid crystal optical vortex demultiplexer and manufacturing method thereof |
| CN110927856B (en) * | 2019-12-12 | 2023-10-20 | 华南师范大学 | Liquid crystal optical vortex demultiplexer and manufacturing method thereof |
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