CN213042096U - Adjustable terahertz signal deflection device - Google Patents
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- CN213042096U CN213042096U CN202022455131.2U CN202022455131U CN213042096U CN 213042096 U CN213042096 U CN 213042096U CN 202022455131 U CN202022455131 U CN 202022455131U CN 213042096 U CN213042096 U CN 213042096U
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Abstract
The utility model discloses an adjustable terahertz signal deflection ware relates to photoelectric measurement technical field. The embodiment of the utility model provides an adjustable terahertz signal deflection ware includes: the liquid crystal display panel comprises a first transparent substrate, a second transparent substrate, a liquid crystal layer, a transparent electrode layer and a light control orientation layer, wherein the first transparent substrate and the second transparent substrate are arranged oppositely; the light control orientation layer is provided with a control pattern of the periodic gradual change distribution of molecular directors along a certain direction and is used for controlling the periodic gradual change distribution of the liquid crystal molecular directors in the liquid crystal layer along the certain direction to form a blazed grating phase distribution based on a geometric phase, and when a circularly polarized terahertz signal is incident, the circularly polarized terahertz signal can be deflected to a specific angle. The utility model provides a deflection ware can be with terahertz signal deflection to specific angle to add the switching that can realize signal deflection and non-deflection function on transparent electrode with electricity, have that the broadband is suitable for, the miniaturization is easily integrated, characteristics with low costs, have very big application potentiality in the aspect of terahertz communication etc..
Description
Technical Field
The utility model relates to a photoelectric measurement technical field especially relates to an adjustable terahertz signal deflection ware.
Background
The frequency of the terahertz signal is between 0.1 and 10THz (the corresponding wavelength is 30 to 3000 mu m), and due to the unique property, the terahertz technology has wide application prospects in various fields such as safety inspection, biomedicine, high-speed wireless communication and the like. High performance optics for transmission and control of terahertz signals are still in a primary stage of development relative to terahertz sources and detectors. The terahertz signal deflector is one of basic elements for modulating terahertz signals, and has wide application in terahertz communication systems. It is usually made of a prism or a tilted phase plate, and the principle is the accumulation of optical path differences in the propagation direction. These devices are bulky and difficult to implement in a miniaturized, integrated system design. Although the terahertz signal deflecting device prepared by the super-structured surface design is gradually developed later, and the terahertz signal deflecting device can realize a light and thin structure design, the terahertz signal deflecting device has the defects of low efficiency, narrow modulation waveband range and lack of tunability. Therefore, a tunable terahertz signal deflecting device is to be developed to realize dynamic, efficient and broadband terahertz signal deflecting so as to meet the needs of practical application.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide an adjustable terahertz signal deflection ware to solve the problem that current terahertz signal deflection ware efficiency is lower, modulation wave band scope is narrower, and lack the tunability, realize the terahertz signal deflection of developments, high-efficient, broadband, satisfy practical application's needs.
In order to achieve the above object, an embodiment of the present invention provides an adjustable terahertz signal deflection device, including:
the liquid crystal display panel comprises a first transparent substrate, a second transparent substrate and a liquid crystal layer, wherein the first transparent substrate and the second transparent substrate are oppositely arranged, and the liquid crystal layer is positioned between the first transparent substrate and the second transparent substrate;
a first transparent electrode layer and a second transparent electrode layer are respectively arranged on one sides of the first transparent substrate and the second transparent substrate, which are close to the liquid crystal layer;
a first light control orientation layer and a second light control orientation layer are respectively arranged on one sides, adjacent to the liquid crystal layer, of the first transparent electrode layer and the second transparent electrode layer;
the first transparent electrode layer and the second transparent electrode layer are made of materials with high transmittance and good conductivity in a terahertz wave band; the photoalignment layer is provided with a control pattern with a molecular director periodically and gradually distributed along a certain direction; the control pattern is used for controlling liquid crystal molecule director in the liquid crystal layer to be periodically and gradually distributed along a certain direction to form blazed grating phase distribution based on a geometric phase, and when a circular polarization terahertz signal is incident, the blazed grating phase distribution can be deflected to a specific angle.
Preferably, the signal deflector further includes a spacer between the first and second transparent substrates, the spacer supporting the first and second transparent substrates to form a filling space of the liquid crystal layer.
Preferably, the thickness of the liquid crystal layer is 200-700 μm.
Preferably, the material used for the first transparent electrode layer and the second transparent electrode layer includes graphene, PEDOT or metal wire grid.
Preferably, the liquid crystal layer adopts a dielectric material with birefringence.
Preferably, the birefringence of the liquid crystal layer is 0.2 or more and 0.4 or less.
Preferably, the first transparent substrate and the second transparent substrate are made of materials having high transmittance and low loss rate in the terahertz range, and comprise quartz glass or silicon wafers.
The embodiment of the utility model provides a, following beneficial effect has:
the utility model provides an adjustable terahertz signal deflection ware, include: the liquid crystal display panel comprises a first transparent substrate, a second transparent substrate and a liquid crystal layer, wherein the first transparent substrate and the second transparent substrate are oppositely arranged, and the liquid crystal layer is positioned between the first transparent substrate and the second transparent substrate; a first transparent electrode layer and a second transparent electrode layer are respectively arranged on one sides of the first transparent substrate and the second transparent substrate, which are close to the liquid crystal layer; a first light control orientation layer and a second light control orientation layer are respectively arranged on one sides, adjacent to the liquid crystal layer, of the first transparent electrode layer and the second transparent electrode layer; the first transparent electrode layer and the second transparent electrode layer are made of materials with high transmittance and good conductivity in a terahertz wave band; the photoalignment layer is provided with a control pattern with a molecular director periodically and gradually distributed along a certain direction; the control pattern is used for controlling liquid crystal molecule director in the liquid crystal layer to be periodically and gradually distributed along a certain direction to form blazed grating phase distribution based on a geometric phase, and when a circular polarization terahertz signal is incident, the blazed grating phase distribution can be deflected to a specific angle. The terahertz signal deflecting device based on the broadband application of the electrically-tunable liquid crystal has the characteristics of suitability for the broadband, miniaturization and easiness in integration. Compared with terahertz signal deflectors prepared on quartz crystals and ultrastructural surfaces in the prior art, the terahertz signal deflectors with different deflection angles can be prepared through flexible exposure pattern design, and have great application potential in the fields of terahertz communication and the like.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings required for the embodiments will be briefly described below, and obviously, the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic cross-sectional structure diagram of an adjustable terahertz signal deflecting device according to an embodiment of the present invention;
fig. 2 is a schematic diagram illustrating a distribution simulation of director of liquid crystal molecules in an adjustable terahertz signal deflector according to an embodiment of the present invention;
fig. 3 is a schematic diagram illustrating phase distribution simulation of an adjustable terahertz signal deflecting device according to an embodiment of the present invention;
fig. 4 is an orthogonal polarization microscope photograph of an adjustable terahertz signal polarizer provided by an embodiment of the present invention;
fig. 5 is a schematic optical path diagram of a characterization system of an adjustable terahertz signal deflector according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of normalized terahertz far-field intensity distribution at a 1THz frequency with left-handed circularly polarized terahertz signal incident, with the xy-plane being a terahertz signal transmission cross-section and the xz-plane being a terahertz signal transmission plane;
fig. 7 is a schematic diagram of normalized terahertz far-field intensity distribution at a 1THz frequency upon incidence of a right-handed circularly polarized terahertz signal, where the xy-plane is a terahertz signal transmission cross-section and the xz-plane is a terahertz signal transmission plane;
FIG. 8 is a graphical illustration of a normalized terahertz far-field intensity distribution at 1THz frequency at line-polarized terahertz signal incidence with a 200V voltage applied to the transparent electrode;
fig. 9 is a graph of theoretical modulation efficiency and deflection angle of an adjustable terahertz signal deflector at different terahertz frequencies according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
It should be understood that the step numbers used herein are for convenience of description only and are not intended as limitations on the order in which the steps are performed.
It is to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The terms "comprises" and "comprising" indicate the presence of the described features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The term "and/or" refers to and includes any and all possible combinations of one or more of the associated listed items.
Please refer to fig. 1.
The embodiment of the utility model provides an adjustable terahertz signal deflection ware, including relative first transparent substrate 1 and the second transparent substrate 6 that sets up, and be located the liquid crystal layer 8 between first transparent substrate 1 and the second transparent substrate 6; a first transparent electrode layer 2 and a second transparent electrode layer 5 are respectively arranged on one sides of the first transparent substrate 1 and the second transparent substrate 6, which are close to the liquid crystal layer 8; a first photoalignment layer 3 and a second photoalignment layer 4 are respectively arranged on one sides, adjacent to the liquid crystal layer 8, of the first transparent electrode layer 2 and the second transparent electrode layer 5; the first transparent electrode layer 2 and the second transparent electrode layer 5 are made of materials with high transmittance and good conductivity in a terahertz signal section, and include graphene, a metal wire grid or PEDOT (PEDOT is a polymer of EDOT (3, 4-ethylene dioxythiophene monomer), and PEDOT has the characteristics of simple molecular structure, small energy gap, high conductivity and the like, and is widely used as a research in the fields of organic thin-film solar cell materials, OLED materials, electrochromic materials, transparent electrode materials and the like), and as an example, the first transparent substrate 1 and the second transparent substrate 2 are made of materials with high transmittance in a terahertz section, including quartz glass or silicon wafers; the first transparent electrode layer 2 and the second transparent electrode layer 5 are made of graphene materials with high transmittance and good conductivity in a terahertz signal section; the photo-alignment layer is provided with a control pattern with a molecular director periodically and gradually distributed along a certain direction, as an example, the photo-alignment layer is made of azo dyes which are sensitive to linearly polarized ultraviolet light, and when the linearly polarized ultraviolet light is irradiated, the alignment direction is arranged along the direction vertical to the polarization direction; the control pattern of the photoalignment layer controls the liquid crystal molecular director in the liquid crystal layer 8 to be periodically and gradually distributed along a certain direction to form blazed grating phase distribution based on a geometric phase, and when a circularly polarized terahertz signal is incident, the circularly polarized terahertz signal can be deflected to a specific angle. The light-forming alignment layer is made of azo dyes, the azo dyes are sensitive to linearly polarized ultraviolet light, and when the linearly polarized ultraviolet light irradiates, the alignment direction can be arranged along the direction vertical to the polarization direction. In the experiment, ultraviolet light irradiates different orientation areas each time, and the designed arbitrary orientation direction control can be realized by using the ultraviolet light with different linear polarization directions in each area.
The geometric phase is a phase only related to the deflection direction of the crystal axis of the liquid crystal, and when left (right) circularly polarized light is incident into the geometric phase optical element, the emergent right (left) circularly polarized light carries an additional phase which is equal to twice the deflection azimuth angle of the crystal axis of the liquid crystal in value. As shown in fig. 2, the embodiment of the present invention provides a schematic diagram for simulating the distribution of director of liquid crystal molecules in an adjustable terahertz signal deflecting device, wherein the director of liquid crystal is periodically changed from 0 to 180 ° in the x direction, and the generated geometric phase is periodically changed from 0 to 360 ° in the x direction to generate an inclined phase of a blazed grating, thereby realizing signal deflection at a specific angle. For different deflection angles, the grating period P can be changed, thereby obtaining different signal deflection angles. The grating period P has the following relationship with the deflection angle θ and the incident light frequency f: p sin θ is c/f, where c is the speed of light in vacuum. By way of example, in the embodiment of the present invention, a signal deflecting device with a deflection angle of 14 ° at 1THz is designed, and the grating period P is 1240 μm through the calculation of the above formula.
The first transparent electrode layer 2 and the second transparent electrode layer 5 are made of materials with high transmittance and good conductivity in a terahertz signal section; the photoalignment layer is provided with a control pattern with a molecular director periodically and gradually distributed along a certain direction; the control pattern is used for controlling the liquid crystal molecule director in the liquid crystal layer 8 to be periodically and gradually distributed along a certain direction to form blazed grating phase distribution based on a geometric phase, and when a circular polarization terahertz signal is incident, the blazed grating phase distribution can be deflected to a specific angle.
The signal deflector further comprises a spacer 7 positioned between the first transparent substrate 1 and the second transparent substrate 6, wherein the spacer 7 is used for supporting the first transparent substrate 1 and the second transparent substrate 6 to form a filling space of a liquid crystal layer 8, and in order to enable the thickness of the liquid crystal layer 8 to meet the incident light frequency range of the terahertz lens to be 0.6-1.4 THz, the thickness of the liquid crystal layer is designed to be 500 μm, so that the optimal modulation efficiency at 1THz is realized.
In order to enable the thickness of the liquid crystal layer 8 to meet the half-wave condition of the incident terahertz signal, namely the incident light frequency range is 0.6-1.4 THz, the thickness of the liquid crystal layer 8 is 200-700 μm.
Preferably, the liquid crystal layer 8 is made of a dielectric material having a birefringence. The liquid crystal of the liquid crystal layer 8 is made of a material with a birefringence in a terahertz signal section, wherein the birefringence is the maximum difference between two or three main refractive indexes in a non-homogeneous body; in order to enable the thickness of the liquid crystal layer 8 to meet the half-wave condition of an incident terahertz signal, namely the frequency range of the incident light is 0.6-1.4 THz, the birefringence of the liquid crystal layer 8 is more than or equal to 0.2 and less than or equal to 0.4; as a best example, in order to enable the thickness of the liquid crystal layer 8 to meet the condition that the frequency range of incident light entering the terahertz lens is 0.6-1.4 THz, the birefringence of the liquid crystal layer 8 is 0.3.
Please refer to fig. 2-4.
Fig. 3 is a schematic diagram showing phase distribution simulation of the adjustable terahertz signal deflecting device according to an embodiment of the present invention, in which a continuous periodic change of a phase of 0-360 ° in the x direction can be seen, and the phase distribution is matched with the liquid crystal director distribution diagram of the design shown in fig. 2. Fig. 4 is an orthogonal polarization microscope photograph of an adjustable terahertz signal polarizer prepared by using an ultraviolet polarization exposure orientation system based on a digital micromirror array. In this embodiment, the photograph brightness exhibits continuous brightness variation over 360 ° with orientation in the x direction. This intensity variation is the result of the continuous variation of the liquid crystal director, which is shown in fig. 4 by the dark to light to dark gradual change from 0 to 90. The overall intensity variation coincides with the theoretical liquid crystal director distribution in figure 2.
In a specific embodiment, by enabling the liquid crystal molecular director to be distributed in a periodic 0-180-degree gradual change manner along the x direction, after an incident circularly polarized terahertz signal passes through the device, an emergent orthogonal circularly polarized terahertz signal generates blazed grating type phase modulation, the terahertz signal is deflected by an angle, and the modulation effect can cover a wider terahertz frequency range. If the orthogonal circular polarization state incidence is changed, the deflection angle is changed symmetrically along the propagation direction.
On the basis of the above embodiment, optionally, the thickness d of the liquid crystal layer satisfies: d is more than or equal to 200 mu m and less than or equal to 700 mu m. It is understood that since the phase retardation condition Δ Φ ═ 2 pi Δ nd/λ where Δ n denotes a difference in birefringence of liquid crystal molecules and d denotes a thickness of the liquid crystal layer, a half-wave condition needs to be satisfied at a specific wavelength λ to maximize the operation efficiency of the geometric phase optical element. For the terahertz signal deflector in the present embodiment, a theoretically preferred value of the thickness d is 500 μm, and if d is smaller than this value, the modulation efficiency gradually decreases. However, the orientation effect of the liquid crystal layer becomes worse under the thickness of more than 700 μm, so in this embodiment, the thickness of the liquid crystal polymer film can be designed to be 200 μm-700 μm, and when d is less than 200 μm, the efficiency of the device is very low because the phase accumulation of the terahertz signal passing through the device far does not reach the half-wave condition of the terahertz signal section; when d is larger than 700 μm, too large thickness results in poor alignment of the liquid crystal in the intermediate layer, which may affect the device. Further, the preferred value of the thickness d of the liquid crystal polymer film is 500 μm, at which the alignment effect is good and the modulation efficiency is high at 1 THz.
Please refer to fig. 5.
Fig. 5 is a schematic optical path diagram of a characterization system of an adjustable terahertz signal deflecting device provided in the embodiment of the present invention, including the terahertz signal deflecting device 13 provided in the above embodiment, further includes: a photoconductive antenna 9 for generating a linearly polarized terahertz signal; the metal parabolic mirror 10 is positioned on an emergent light path of the light guide antenna 9 and used for converging and collimating linearly polarized terahertz signals; a chopper 11 for converting the linearly polarized terahertz signal into pulsed light; a first quarter-wave plate 12 for converting the linearly polarized terahertz signal into a circularly polarized terahertz signal; the terahertz signal deflecting device 13 is used for deflecting the circularly polarized terahertz signal by a certain angle; a second quarter-wave plate 14 for converting the circularly polarized terahertz signal into a linearly polarized terahertz signal; a photoconductive antenna probe 15 for detecting a terahertz vortex beam; the chopper 11, the first quarter-wave plate 12, the terahertz signal deflector 13, the second quarter-wave plate 14, the light guide antenna probe 15 and the metal parabolic mirror 10 share an optical axis, and are sequentially arranged along the emergent light direction of the metal parabolic mirror 10.
Please refer to fig. 6-7.
Fig. 6 is a schematic diagram of normalized terahertz far-field intensity distribution at a 1THz frequency under incidence of a left-handed circularly polarized terahertz signal, where an xy plane is a terahertz signal transmission cross section, and an xz plane is a terahertz signal transmission plane. It can be found that at this time, the terahertz signal is deflected to the left side, and the deflection angle of-14 ° is matched with the designed deflection angle. Fig. 7 is a schematic diagram of normalized terahertz far-field intensity distribution at a 1THz frequency upon incidence of a right-handed circularly polarized terahertz signal, where the xy-plane is a terahertz signal transmission cross-section and the xz-plane is a terahertz signal transmission plane. It can be seen that the terahertz signal is deflected to the right at this time, which is conjugate to the situation in fig. 6, and the deflection angle of 14 ° matches the designed deflection angle. Therefore, by switching the left-right circular polarization state, the dynamic switching of the deflection of the terahertz signal on the left side and the right side can be realized.
Please refer to fig. 8.
In order to realize the function of dynamic tuning, the first transparent electrode layer 2 and the second transparent electrode layer 5 (i.e. the graphene transparent electrodes) of the first transparent substrate 1 and the second transparent substrate are energized by using an alternating voltage until the first transparent electrode layer and the second transparent electrode layer are saturated, and a voltage of 200V is required in an experiment, so that the pointing direction of liquid crystal molecules under an electric field is deflected to the z-axis direction. At this time, all liquid crystal molecules are deflected to the z-axis direction, the modulation effect of the geometric phase disappears, the function of signal deflection disappears, and the terahertz signal can directly pass through the sample when being incident without generating any modulation effect. As shown in fig. 8, is a graphical representation of the normalized terahertz far-field intensity distribution at 1THz frequency at line-polarized terahertz signal incidence with 200V applied to the transparent electrode. It can be seen that the light spot appears in the middle, not left or right, which shows that there is no deflection effect on the incident terahertz signal. The above results fully verify the dynamic tuning effect of the terahertz signal deflecting device in this embodiment, and can realize dynamic switching between deflecting and non-deflecting functions.
Please refer to fig. 9.
Fig. 9 is a graph of theoretical modulation efficiency and deflection angle of an adjustable terahertz signal deflector at different terahertz frequencies according to an embodiment of the present invention. The deflection angle θ has the following relationship with the frequency f: sin θ is c/(f · P). The deflection angle θ gradually decreases as the frequency f increases. The modulation efficiency η has the following relationship with the frequency f: η ═ sin (π f Δ nd/c) ^2, where Δ n represents the birefringence difference of the liquid crystal molecules, d represents the thickness of the liquid crystal layer, and c is the speed of light in vacuum. Since the thickness d is optimized at 1THz, the theoretical efficiency at 1THz is seen to be the highest, reaching 100%, and the efficiency gradually decreases from 1THz to both sides.
The terahertz signal deflecting device based on the broadband application of the electrically-tunable liquid crystal has the characteristics of suitability for the broadband, miniaturization and easiness in integration. Compared with the existing terahertz signal deflection device prepared from quartz crystal and a super-structured surface, the terahertz signal deflection device has obvious advantages. Through flexible exposure pattern design, terahertz signal deflectors with different deflection angles can be prepared, and the terahertz signal deflectors have great application potential in the fields of terahertz communication and the like.
The embodiment of the utility model provides a pair of adjustable terahertz signal deflection ware can use in terahertz communication system now. In terahertz communication, a modulator is required to perform beamforming on terahertz signals, so that the terahertz signals are emitted in different directions, and therefore a dynamically adjustable signal deflector with low cost and large bandwidth is required to realize the functions.
The foregoing is a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations are also considered as the protection scope of the present invention.
Claims (7)
1. An adjustable terahertz signal deflector, comprising:
the liquid crystal display panel comprises a first transparent substrate, a second transparent substrate and a liquid crystal layer positioned between the first transparent substrate and the second transparent substrate;
a first transparent electrode layer and a second transparent electrode layer are respectively arranged on one sides of the first transparent substrate and the second transparent substrate, which are close to the liquid crystal layer;
a first light control orientation layer and a second light control orientation layer are respectively arranged on one sides, adjacent to the liquid crystal layer, of the first transparent electrode layer and the second transparent electrode layer;
the first transparent electrode layer and the second transparent electrode layer are made of materials with high transmittance and good conductivity in a terahertz wave band;
the photoalignment layer is provided with a control pattern with a molecular director periodically and gradually distributed along a certain direction;
the control pattern is used for controlling liquid crystal molecule director in the liquid crystal layer to be periodically and gradually distributed along a certain direction to form blazed grating phase distribution based on a geometric phase, and when a circular polarization terahertz signal is incident, the blazed grating phase distribution can be deflected to a specific angle.
2. The adjustable terahertz signal deflector of claim 1, further comprising a spacer between the first transparent substrate and the second transparent substrate, the spacer configured to support the first transparent substrate and the second transparent substrate to form a filling space for the liquid crystal layer.
3. The adjustable terahertz signal deflector of claim 1, wherein the liquid crystal layer has a thickness of 200-700 μm.
4. The adjustable terahertz signal deflector of claim 1, wherein the materials used for the first and second transparent electrode layers comprise graphene, PEDOT or wire grid.
5. The tunable terahertz signal deflector of claim 1, wherein the liquid crystal layer is made of a dielectric material with birefringence.
6. The tunable terahertz signal polarizer of claim 1, wherein the birefringence of the liquid crystal layer is greater than or equal to 0.2 and less than or equal to 0.4.
7. The adjustable terahertz signal deflector of claim 1, wherein the first transparent substrate and the second transparent substrate are made of materials with high transmittance in the terahertz range, and comprise quartz glass or silicon wafers.
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| CN112180652A (en) * | 2020-10-28 | 2021-01-05 | 广州铁路职业技术学院（广州铁路机械学校） | Adjustable terahertz signal deflection device and preparation method thereof |
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| WO2022088203A1 (en) * | 2020-10-28 | 2022-05-05 | 广州铁路职业技术学院（广州铁路机械学校） | Tunable terahertz signal deflector and preparation method therefor |
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