CN107703652A - A kind of electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive is adjustable THz wave absorber and preparation method thereof - Google Patents

Abstract

An electronically controlled liquid crystal tunable terahertz wave absorber based on graphene/metamaterial synergistic drive and a preparation method thereof, belonging to the field of terahertz optoelectronic technology. The absorber includes a quartz substrate a, a liquid crystal layer and a quartz substrate b, the quartz substrate a and the quartz substrate b are combined by a frame glue to form a liquid crystal cell, and the liquid crystal layer is arranged at the junction of the quartz substrate a and the quartz substrate b; the quartz substrate a The inner side includes a periodic subwavelength metal unit array, a porous graphene layer, and a photo-alignment layer a from the inside to the outside; the inside of the quartz substrate b includes a metal mirror and a photo-alignment layer b from the inside to the outside, and the liquid crystal layer is injected into Large birefringence liquid crystal material in the terahertz band. The preparation method of the present invention is simple and efficient, and the sub-wavelength unit structure array can be designed arbitrarily. The prepared terahertz wave absorber has good electric field distribution and ability to control liquid crystals, and has the advantages of wide modulation frequency band and fast modulation speed.

Description

An electronically controlled liquid crystal tunable terahertz wave based on graphene/metamaterial synergistic drive Absorber and its preparation method

technical field

The invention relates to the technical field of terahertz optoelectronics, in particular to an electronically controlled liquid crystal tunable terahertz wave absorber driven by graphene/metamaterial synergy and a preparation method thereof.

Background technique

Liquid crystal materials have both the fluidity of liquids and the orderliness of crystals. Due to their excellent tuning characteristics of external fields (electric field, magnetic field, light field, sound field, temperature field, etc.), they play an important role in information display and adjustable photonic devices. Applications. Nematic liquid crystal is the most commonly used phase state, and in all nematic liquid crystal applications, orientation is the first step. The traditional orientation method, rubbing orientation, is the most widely used method, which has defects such as mechanical damage to the surface, electrostatic charge residue and particle contamination, and difficulty in realizing multi-domain structure orientation. The emerging photo-alignment technology can completely overcome the above-mentioned shortcomings, and is regarded as the most competitive next-generation liquid crystal alignment technology.

In recent years, people's research and application of terahertz frequency band has been increasing, but photonic devices suitable for terahertz frequency band, especially tunable devices are still very rare. As a commonly used tunable electro-optic material, liquid crystals have been widely developed and applied in photonic devices in the visible and infrared bands. However, when applied in the terahertz frequency band, on the one hand, the commonly used transparent conductive film indium tin oxide is no longer applicable, and a simple metal layer cannot meet the requirements, so it is necessary to seek a new electrode design. On the other hand, the birefringence of most liquid crystal materials will be relatively small in the terahertz frequency band, so the adjustable amount is also small, and it is difficult to meet practical requirements in general design. And some special means to increase the modulation amount, such as stacked structure, etc., will seriously increase the loss under the condition of lack of transparent electrodes.

Contents of the invention

Technical problem to be solved: Aiming at the above technical problems, the present invention provides an electronically controlled liquid crystal tunable terahertz wave absorber based on graphene/metamaterial synergistic drive and its preparation method. The preparation method is simple and efficient, and sub-wavelength can be arbitrarily designed The unit structure array, the prepared terahertz wave absorber has good electric field distribution and the ability to control liquid crystal, and has the advantages of wide modulation frequency band and fast modulation speed.

Technical solution: An electronically controlled liquid crystal tunable terahertz wave absorber based on graphene/metamaterial synergistic drive, the absorber includes a quartz substrate a, a liquid crystal layer and a quartz substrate b, and the quartz substrate a and quartz substrate b pass through the frame The liquid crystal cell is formed by glue bonding, and the liquid crystal layer is arranged at the junction of the quartz substrate a and the quartz substrate b; the inner side of the quartz substrate a sequentially includes a periodic sub-wavelength metal unit array, a porous graphene layer and a photo-alignment layer a; The inner side of the quartz substrate b sequentially includes a metal reflector and a photo-alignment layer b; The surroundings of the liquid crystal layer are respectively connected to the inner sides of the quartz substrate a and the quartz substrate b. The liquid crystal material is a liquid crystal material with a large birefringence in the terahertz band. After the frame glue is combined into a liquid crystal cell, it is injected into the intermediate air layer formed by the silica microsphere gasket material.

Preferably, the number of graphene layers in the porous graphene layer is 2-5 layers, and pores with a diameter of micron scale are distributed on the surface thereof.

Preferably, the period of the periodic sub-wavelength metal unit array is smaller than the wavelength of the incident light terahertz, and is 100-200 μm.

Preferably, the periodic sub-wavelength metal unit array is in the shape of a cross or a disc, with a thickness of 100-500 nm.

Preferably, the metal mirror is a metal plate with a thickness of 100-500 nm.

Preferably, the liquid crystal material has a birefringence of 0.25-0.4 at 0.5-2.5 THz.

Another technical solution of the present invention is the preparation method of the electrically controlled liquid crystal tunable terahertz wave absorber based on graphene/metamaterial synergistic drive, the preparation method comprising the following steps:

Step 1. Melting the quartz substrate a and the quartz substrate b, setting a periodic sub-wavelength metal unit array on the inside of the fused quartz substrate a through photolithography and coating processes, and setting a metal reflector on the inside of the quartz substrate b through a coating process;

Step 2. Grow 2 to 5 layers of graphene grown by chemical vapor deposition (CVD) on the copper foil substrate, and then transfer the graphene film from the copper foil substrate to the surface of the periodic subwavelength metal unit array by conventional transfer method , and then its surface is treated with ultraviolet ozone method to obtain a porous graphene layer with micron-sized holes on the surface;

Step 3. coating the photoalignment agent film on the surface of the porous graphene layer to obtain the photoalignment layer a, and coating the photoalignment agent film on the surface of the metal reflector to obtain the photoalignment layer b, the photoalignment agent film Prepared for film orientation on a photosensitive alignment agent;

Step 4. Select the liquid crystal material, calculate the required liquid crystal layer thickness d according to the refractive index parameter of the selected liquid crystal material and the target absorber type, and the liquid crystal layer thickness d is between λ/(40n) to λ/(20n), And select the silicon dioxide microsphere whose diameter corresponds to the thickness value of the liquid crystal layer as the surrounding pad material, λ is the wavelength, and n is the refractive index of the liquid crystal;

Step 5. After placing the silicon dioxide microsphere liner material around the surface of the photo-alignment layer b, place the surface where the photo-alignment layer a inside the quartz substrate a is located and the surface where the photo-alignment layer b is located inside the quartz substrate b, and then expose and give The molecules of the photoalignment agent film are uniformly oriented, and then the quartz substrate a, the silica microsphere gasket material and the quartz substrate b are packaged from top to bottom into a liquid crystal cell by using a sealant;

Step 6. Inject the liquid crystal material into the intermediate air layer formed by the silica microsphere liner in the liquid crystal cell, and finally use the electronically controlled birefringence characteristics of the liquid crystal to adjust the refractive index of the liquid crystal by voltage to realize the regulation of the ultra-wideband terahertz wave .

As a preference, when the exposure in the step 5 imparts a uniform orientation to the molecules of the photoalignment agent film and is arranged before being packaged into a liquid crystal cell, the polarization direction is first parallel to the direction of any arm or diameter in the periodic pressure wavelength metal unit array. Linearly polarized ultraviolet or blue light vertical exposure endows the molecules of the alignment agent with uniform orientation, and then makes a liquid crystal cell; when the exposure in the fifth step imparts uniform orientation to the molecules of the light control alignment agent film and is installed after packaging into a liquid crystal cell, first use the sealant Packaged into a liquid crystal cell, and then vertically exposed to linearly polarized ultraviolet or blue light with a polarization direction parallel to the direction of any arm or diameter in the periodic voltage wavelength metal unit array to endow the alignment agent molecules in the photo-alignment layer a and b with uniform orientation.

Beneficial effect:

(1) As a metamaterial/graphene composite electrode, metamaterials can design subwavelength unit structure arrays arbitrarily, and realize metamaterial absorbers with specific performance and high quality factor, without the limitation that subwavelength units must be connected in at least one direction in the past ;

(2) Graphene, as a metamaterial/graphene composite electrode, has a transmittance close to 100% in the terahertz band, does not affect the absorber characteristics of the metamaterial, and has good electric field distribution and control of the liquid crystal together with the metamaterial. ability, and its surface resistance is further lower than that of pure graphene electrodes, which is conducive to the fabrication of array devices.

(3) On the one hand, the metal plate is used as the reflective surface of the terahertz absorber, which can ensure that the terahertz wave has 100% reflectivity in the ultra-wide frequency band; on the other hand, as the ground electrode, it has good electric field distribution and The ability to control liquid crystals;

(4) Use light-controlled orientation technology to achieve uniform and effective orientation, and achieve precise control of the orientation direction and alignment direction, ensuring that the device obtains the maximum modulation amount and the fastest modulation speed; and will not cause damage to the relatively fragile graphene transparent electrode ;

(5) The liquid crystal material with low absorption loss and large birefringence in the terahertz frequency band is selected to effectively reduce the thickness of the cell, reduce the applied voltage and greatly improve the modulation range of the near field and far field of the terahertz wave;

(6) The preparation method is simple, efficient, cheap, and can be mass-produced, the performance of the device is stable, and all indicators meet the practical requirements of terahertz photonic devices;

(7) The present invention is an electronically controlled terahertz wave absorber that can realize ultra-wide frequency band, large modulation amount, and fast response. The broadband adjustable terahertz wave absorber can be used for terahertz wave modulation and detection. Communication, terahertz sensing, terahertz imaging and other fields have broad application prospects.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the electronically controlled liquid crystal tunable terahertz wave absorber driven by graphene/metamaterial synergy in Example 1.

FIG. 2 is a microscope picture of the cross-shaped periodic subwavelength metal unit array metamaterial in Example 1. FIG.

Figure 3 is a schematic diagram of electrostatic field and liquid crystal director distribution. In the figure, a represents only a cross-shaped periodic sub-wavelength metal unit array metamaterial electrode, and b represents a cross-shaped periodic sub-wavelength metal unit array and graphene composite as an electrode.

Figure 4 is a simulation characteristic diagram of the adjustable terahertz wave absorber of the present invention, Figure a is a simulation characteristic diagram of far-field absorption, and Figure b is a simulation characteristic diagram of near-field variation.

Fig. 5 is an experimental test diagram of the terahertz transmittance of the graphene/metamaterial composite electrode.

Figure 6 is a pressurized test diagram of the electronically controlled adjustable terahertz wave absorber, Figure a is the experimental test diagram of the frequency absorption characteristics of the electrically controlled adjustable terahertz wave absorber, and Figure b is the electrically controlled adjustable terahertz wave absorber The resonant frequency test chart of the absorber under different voltages.

Fig. 7 is a schematic structural view of the disc-shaped electronically controlled liquid crystal tunable terahertz wave absorber described in Example 2.

Fig. 8 is a simulated characteristic diagram of the disc-type electronically controlled liquid crystal tunable terahertz wave absorber described in Example 2.

The numbers in the figure represent the following: 1. Quartz substrate a; 2. Periodic sub-wavelength metal unit array; 3. Porous graphene layer; 4. Optical alignment layer a; 5. Liquid crystal layer; 6. Metal mirror; 7. Photo-alignment layer b; 8. Quartz substrate b.

detailed description

The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Example 1

An electronically controlled liquid crystal tunable terahertz wave absorber based on graphene/metamaterial synergistic drive, referring to Figure 1, the absorber includes a quartz substrate a 1, a liquid crystal layer 5 and a quartz substrate b 8, the quartz substrate a 1 and The quartz substrate b 8 is bonded by frame glue to form a liquid crystal cell, and the liquid crystal layer 5 is arranged at the junction of the quartz substrate a 1 and the quartz substrate b 8 .

The inner side of the quartz substrate a 1 includes a periodic subwavelength metal unit array 2, a porous graphene layer 3 and a photo-alignment layer a 4 in sequence from the inside to the outside. The periodic subwavelength metal unit array 2 is a cross-shaped metal unit array, and the period The thickness is 150 μm, less than the wavelength of incident light terahertz, and the thickness is 100 nm. The number of layers of graphene in the porous graphene layer 3 is 3 layers, and the surface of the porous graphene layer 3 is distributed with holes with a diameter of micron scale.

The inner side of the quartz substrate b 8 includes a metal mirror 6 and a photo-alignment layer b 7 sequentially from the inside to the outside, and the metal mirror 6 is a metal flat plate with a thickness of 200 nm. The photo-alignment layer a 4 and photo-alignment layer b 7 are aligned on a film of a photosensitive alignment agent, and the photosensitive alignment agent is azobenzene dye, polyimide, polyvinyl alcohol, cinnamate, etc. The anisotropy of molecular arrangement is induced by isomerization, directional photocrosslinking or photocleavage reactions, and this order can be further transferred to liquid crystal molecules through intermolecular interactions.

The liquid crystal layer 5 includes a silicon dioxide microsphere spacer material and a liquid crystal material, and the silicon dioxide microsphere spacer material is arranged around the liquid crystal layer 5 and is connected to the inside of the quartz substrate a1 and the quartz substrate b8 respectively. Next, the liquid crystal material is a large birefringence liquid crystal material in the terahertz band, and the liquid crystal material selected in this embodiment is room temperature large birefringence liquid crystal NJU-LDn-4 (the material prepared in the open document with the application number CN2012103780326 , the birefringence of the liquid crystal at 0.5~2.5THz is 0.03.) After the quartz substrate a 1, the silica microsphere gasket material and the quartz substrate b 8 frame glue are combined to form a liquid crystal cell, the silica microsphere gasket is injected In the intermediate air layer formed by the material.

The preparation method of the electronically controlled liquid crystal tunable terahertz wave absorber based on graphene/metamaterial synergistic drive is as follows:

Step 1. Take the quartz substrate a1 and the quartz substrate b8 to melt, and set the cross-shaped periodic sub-wavelength metal unit array 2 on the inner side of the fused silica substrate a1 through photolithography and coating process, and the cross-shaped periodic sub-wavelength metal unit array 2 The preparation method is as follows: photolithography and development were carried out on the fused silica substrate a1, a photolithography template with a cross arm length of 100 μm+120 μm was selected, and a gold film with a thickness of 100 nm was deposited by electron beam evaporation physical vapor deposition method to After photolithography, the residual photoresist is eluted by ultrasonic cleaning to obtain a gold cross array with a period of 150 μm and a line width of 10 μm, and a microscope for the morphology of the cross array metamaterial (periodic subwavelength metal unit) Refer to Figure 2 for the picture, the scale in the figure is 50 μm, lx and ly are the arm lengths in the x and y directions respectively, w is the line width, and P is the period. A metal mirror 6 is provided on the inner side of the quartz substrate b8 through a coating process. The preparation method of the metal mirror 6 is as follows: a gold film with a thickness of 200 nm is deposited on the inner surface of the fused silica substrate b8 by electron beam evaporation physical vapor deposition.

Step 2. Grow three layers of graphene grown by chemical vapor deposition (CVD) on the copper foil substrate, and then transfer the graphene film from the copper foil substrate to the surface of the periodic subwavelength metal unit array 2 by a conventional transfer method, Then its surface is treated with ultraviolet ozone method, and the porous graphene layer 3 with micron-scale holes on the surface is prepared.

Step 3. Coating a photo-alignment agent film on the surface of the porous graphene layer 3 to obtain a photo-alignment layer a 4, and coating a photo-control alignment agent film on the surface of the metal mirror 6 to obtain a photo-alignment layer b 7 The film of the alignment agent is made by aligning the film of the photosensitive alignment agent.

Step 4. Select the liquid crystal material NJU-LDn-4, and calculate the required liquid crystal layer thickness d according to the refractive index parameter of the selected liquid crystal material and the target absorber type to be 15 μm, and the liquid crystal layer thickness d is taken from λ/(40n) to between λ/(20n), and select silicon dioxide microspheres whose diameter corresponds to the thickness of the liquid crystal layer as the surrounding gasket material, where λ is the wavelength, and n is the refractive index of the liquid crystal.

Step 5. After placing the silicon dioxide microsphere liner material around the surface of the photo-alignment layer b7, place the surface of the photo-alignment layer a4 inside the quartz substrate a1 and the surface of the photo-alignment layer b7 inside the quartz substrate b8 facing each other , and then expose to impart uniform orientation to the molecules of the photoalignment agent film, and vertically expose the polarized ultraviolet or blue light of 405±10 nm whose polarization direction is parallel to the direction of any arm in the periodic subwavelength metal unit array 2 to impart uniform orientation to the molecules of the alignment agent (the alignment direction is 0° to one arm of 100 μm in the periodic subwavelength metal unit array 2 to obtain the photo-controlled alignment layer), and then use the frame glue to seal the quartz substrate a 1, the silica microsphere liner material and the quartz substrate b 8 Packaged into a liquid crystal cell from top to bottom.

Step 6. Inject the liquid crystal material into the intermediate air layer formed by the silicon dioxide microsphere liner in the liquid crystal cell on a hot stage at 120 ℃, and finally use the electronically controlled birefringence characteristics of the liquid crystal to adjust the refractive index of the liquid crystal by voltage to achieve super Manipulation of broadband terahertz waves.

As shown in Figure 3a, when only the cross-shaped metamaterial is used as the electrode to control the liquid crystal, due to the fringe field effect, the strong electric field is only concentrated under the metal cross, and the electrostatic field around the edges is weak. This uneven electrostatic field leads to very uneven director distribution of liquid crystals. Only the liquid crystal directly under the metal cross can stand up completely at 10 V. If you want to further increase the voltage to make all the liquid crystals vertical, the operating voltage It will be very large, and the power consumption of the device will increase. In order to improve the efficiency of the device, a layer of few-layer porous graphene film is covered on the cross-shaped metamaterial, as shown in Figure 3b. At this time, a uniform electrostatic field can be formed. Under the voltage of 10 V, the directors of all liquid crystals are uniform Can be turned from horizontal to vertical orientation. The simulation results of the far-field characteristics of the tunable terahertz wave absorber are shown in Fig. 4a. The absorption frequency of the terahertz wave in the TE mode (the electric field direction of the terahertz wave is parallel to the x-axis) ranges from 0.864 THz to red in the voltage range of 10V. Moving to 0.742 THz, the absorption frequency of the terahertz wave in the TM mode (the electric field direction of the terahertz wave is parallel to the y-axis) is red-shifted from 1.022 THz to 0.884 THz in the voltage range of 10 V. A indicates 0.864 THz, 0 V; B indicates 0.884 THz, 10 V; C indicates 0.742 THz, 10 V; D indicates terahertz wave far-field and near-field characteristics at 0.742 THz, 0 V. Due to the introduction of graphene, the design of the metamaterial is not limited. In this embodiment, the cross-shaped metamaterial has a better quality factor at the resonant frequency, for example, at 0.9 THz, the quality factor is 10. Its near-field simulation characteristics are shown in Figure 4b. When the voltage is adjusted, near about 0.88 THz, the near-field enhancement moves from one arm of the cross to the other, while the enhanced terahertz electric field of the original arm becomes 0.742 THz, its The near field is very weak at non-resonance. Figure 5 shows the terahertz transmittance test results of graphene/metamaterial composite electrodes. The terahertz wave transmittance characteristic map of the few-layer porous graphene covered on the metamaterial is almost the same as that of the non-covered one, indicating that graphene as a transparent electrode in the terahertz wave band has no effect on the properties of the metamaterial. At the same time, due to the combination of metal metamaterials, its surface resistance is reduced from about 900 Ω sq ^-1 to about 400 Ω sq ^-1 . As shown in Fig. 6a, in the case of no bias voltage, the experimental measurement shows that at 1 THz, the terahertz absorption rate of the TM mode is close to 96%, and the terahertz wave absorption rate of the TE mode at 0.87 THz is 97%; when When the voltage was raised to 5 V, the resonant absorption peak frequencies of the two modes were red-shifted by 80 GHz and 70 GHz, respectively; when the voltage was raised to 10 V, the resonant absorption frequencies moved to 0.88 THz and 0.75 THz. An intensity modulation of 80% can be achieved at the resonant frequency. The change law of resonance absorption frequency with voltage is shown in Figure 6b. Before 1V, the resonance frequency decreases slowly. As the bias voltage further increases, the resonance frequency decreases rapidly, and it tends to saturation at 10V. By changing the terahertz wave mode, the overall adjustable range of the device is as high as 0.25 THz, that is, from 0.75 THz to 1 THz.

Example 2:

This embodiment is a disk-type electronically controlled liquid crystal adjustable terahertz wave absorber. The specific structural design is shown in Figure 7. The structure is the same as that of the absorber described in Embodiment 1. Disc shape, the diameter of the disc is 130 μm, the period is 150 μm, and the thickness of the liquid crystal layer is 10 μm.

Concrete preparation process is as follows:

Step 1. Take the quartz substrate a1 and the quartz substrate b8 to melt, and set the disk-shaped periodic subwavelength metal unit array 2 on the inner side of the fused silica substrate a1 through photolithography and coating process, and the disk-shaped periodic subwavelength metal unit The preparation method of array 2 is as follows: photolithography and development are carried out on the fused silica substrate a 1, a photolithography template with a diameter of 130 μm is selected, and then a gold film with a thickness of 100 nm is deposited by electron beam evaporation physical vapor deposition until after photolithography. The surface of the substrate, and then the residual photoresist is eluted by ultrasonic cleaning to obtain a disc-shaped array with a period of 150 μm and a diameter of 130 μm. A metal mirror 6 is set on the inner side of the quartz substrate b 8 through a coating process. The metal mirror 6 The preparation method is as follows: Deposit a gold film with a thickness of 200 nm on the inner surface of the fused silica substrate b 8 by electron beam evaporation physical vapor deposition method.

Step 2. Grow three layers of graphene grown by chemical vapor deposition (CVD) on the copper foil substrate, and then transfer the graphene film from the copper foil substrate to the surface of the periodic subwavelength metal unit array 2 by a conventional transfer method, Then its surface is treated with ultraviolet ozone method, and the porous graphene layer 3 with micron-scale holes on the surface is prepared.

Step 3. Coating a photo-alignment agent film on the surface of the porous graphene layer 3 to obtain a photo-alignment layer a 4, and coating a photo-control alignment agent film on the surface of the metal mirror 6 to obtain a photo-alignment layer b 7 The film of the alignment agent is made by aligning the film of the photosensitive alignment agent.

Step 4. Select the liquid crystal material NJU-LDn-4, and calculate the required liquid crystal layer thickness d according to the refractive index parameter of the selected liquid crystal material and the target absorber type to be 10 μm, and the liquid crystal layer thickness d is taken from λ/(40n) to between λ/(20n), and select silicon dioxide microspheres whose diameter corresponds to the thickness of the liquid crystal layer as the surrounding gasket material, where λ is the wavelength, and n is the refractive index of the liquid crystal.

Step 5. After placing the silicon dioxide microsphere liner material around the surface of the photo-alignment layer b7, place the surface of the photo-alignment layer a4 inside the quartz substrate a1 and the surface of the photo-alignment layer b7 inside the quartz substrate b8 facing each other , and then use sealant to seal the quartz substrate a 1, silica microsphere liner material and quartz substrate b 8 from top to bottom to form a liquid crystal cell, and then expose to give uniform orientation to the molecules of the photoalignment agent film, with the polarization direction and period Vertical exposure to polarized ultraviolet or blue light of 405±10 nm parallel to the direction of any diameter in the sub-wavelength metal unit array 2 endows alignment agent molecules with uniform orientation.

Step 6. Inject the liquid crystal material into the intermediate air layer formed by the silicon dioxide microsphere liner in the liquid crystal cell on a hot stage at 120 ℃, and finally use the electronically controlled birefringence characteristics of the liquid crystal to adjust the refractive index of the liquid crystal by voltage to achieve super The modulation of broadband terahertz waves can achieve the same modulation characteristics for terahertz waves of different polarization states, as shown in Figure 8. That is, the absorption frequency of the terahertz wave for both TE and TM modes is red-shifted from 0.74 THz to 0.62 THz in the voltage range of 10 V.

The metal selected for the periodic sub-wavelength metal unit array 2 and the metal reflector 6 may be gold, silver, aluminum or platinum.

Although the present invention has been described above with preferred embodiments, it is not intended to limit the present invention. Those skilled in the art of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the claims.

Claims (8)

1. A kind of 1. electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive is adjustable THz wave absorber, it is characterised in that institute Stating absorber includes quartz base plate a（1）, liquid crystal layer（5）With quartz base plate b（8）, quartz base plate a（1）With quartz base plate b（8）It is logical Cross frame glue and be bonded liquid crystal cell, liquid crystal layer（5）Located at quartz base plate a（1）With quartz base plate b（8）Joint；Quartz base plate a （1）Inner side include cycle sub-wavelength metal cell array successively from the inside to surface（2）, porous graphene layer（3）With light redirecting layer a （4）；The quartz base plate b（8）Inner side include metallic mirror successively from the inside to surface（6）With light redirecting layer b（7）；The liquid Crystal layer（5）Including silicon dioxide microsphere gasket material and liquid crystal material, the silicon dioxide microsphere gasket material is located at the liquid Crystal layer（5）Surrounding, respectively with quartz base plate a（1）With quartz base plate b（8）Inner side connect, the liquid crystal material is THz wave The big birefringence liquid crystal material of section, treats quartz base plate a（1）, silicon dioxide microsphere gasket material and quartz base plate b（8）Frame glue knot After synthesizing liquid crystal cell, in the intermediate air layer that injection silicon dioxide microsphere gasket material is formed.
2. A kind of 2. adjustable THz wave of electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive according to claim 1 Absorber, it is characterised in that the porous graphene layer（3）The number of plies of middle graphene is 2-5 layers, and its surface distributed has a diameter of Micron-sized hole.
3. A kind of 3. adjustable THz wave of electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive according to claim 1 Absorber, it is characterised in that the cycle sub-wavelength metal cell array（2）Cycle be less than incident light Terahertz wavelength, For 100 ~ 200 μm.
4. A kind of 4. adjustable THz wave of electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive according to claim 1 Absorber, it is characterised in that the cycle sub-wavelength metal cell array（2）For cross or disc, thickness is 100 ~ 500 nm。
5. A kind of 5. adjustable THz wave of electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive according to claim 1 Absorber, it is characterised in that the metallic mirror（6）For metal plate, thickness is 100-500 nm.
6. A kind of 6. adjustable THz wave of electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive according to claim 1 Absorber, it is characterised in that birefringence of the liquid crystal material in 0.5-2.5 THz is 0.25-0.4.
7. 7. based on a kind of adjustable THz wave of electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive described in claim 1 The preparation method of absorber, it is characterised in that the preparation method comprises the following steps：

   Step 1 takes quartz base plate a（1）With quartz base plate b（8）Melting, in fused silica substrate a（1）Inner side by photoetching and Coating process sets cycle sub-wavelength metal cell array（2）, in quartz base plate b（8）Inner side sets metal by coating process Speculum（6）；

   Step 2 is in 2 ~ 5 layers of chemical vapour deposition technique of copper foil Grown（CVD）The graphene of growth, then by graphene Film is transferred to cycle sub-wavelength metal cell array by conventional transfer method from copper foil substrate（2）Surface, then to its table Face carries out UV ozone method processing, and the porous graphene layer that surface carries micron order hole is made（3）；

   Step 3 is in porous graphene layer（3）Surface applies photo orientated agent film and light redirecting layer a is made（4）, in metallic reflection Mirror（6）Surface apply photo orientated agent film light redirecting layer b be made（7）, the photo orientated agent film is orientation photosensitive The film of alignment agent is made；

   Step 4 chooses liquid crystal material, is calculated according to the refractive index parameter of selected liquid crystal material and target absorption device type Go out required thickness of liquid crystal layer d, thickness of liquid crystal layer d takes λ/(40n) to arrive between λ/(20n), and selects diameter to correspond to liquid crystal layer For the silicon dioxide microsphere of thickness value as surrounding gasket material, λ is wavelength, and n is liquid-crystal refractive-index；

   Step 5 is in light redirecting layer b（7）After the surrounding on surface places silicon dioxide microsphere gasket material, by quartz base plate a（1） Inner side light redirecting layer a（4）Place face and quartz base plate b（8）Inner side light redirecting layer b（7）Place face is staggered relatively, and then exposure is assigned Give photo orientated agent film molecule uniformly to point to, reuse frame glue by quartz base plate a（1）, silicon dioxide microsphere gasket material and Quartz base plate b（8）Liquid crystal cell is packaged into from top to bottom；

   Liquid crystal material is injected silicon dioxide microsphere in liquid crystal cell and padded in the intermediate air layer to be formed by step 6, final to utilize The electrically conerolled birefringence characteristic of liquid crystal, the regulation and control of ultra wide band THz wave are realized by the refractive index of voltage-regulation liquid crystal.
8. A kind of 8. adjustable THz wave of electrically-controlled liquid crystal based on graphene/Meta Materials coordinated drive according to claim 7 The preparation method of absorber, it is characterised in that when the photo orientated agent film molecule of exposure imparting uniformly points in the step 5 When being arranged on before being packaged into liquid crystal cell, first with polarization direction and cycle pressure length metal cell array（2）In any support arm or The parallel linear polarization in direction where person's diameter is ultraviolet or blue light vertical exposure assigns orientation agent molecule and uniformly pointed to, and then makes again Liquid crystal cell；When in the step 5 exposure assign photo orientated agent film molecule uniformly point to be arranged on be packaged into liquid crystal cell after When, liquid crystal cell first is packaged into using frame glue, then with polarization direction and cycle pressure length metal cell array（2）In any support arm or The parallel linear polarization in direction where person's diameter is ultraviolet or blue light vertical exposure assigns light redirecting layer a（4）With light redirecting layer b（7）In Orientation agent molecule uniformly points to.