阅读说明：本技术 基于光激发的太赫兹激光器 (Terahertz laser based on optical excitation ) 是由 欧阳征标 黄粤龙 黄海涛 于 2020-03-04 设计创作，主要内容包括：本发明公开了一种基于光激发的太赫兹激光器,所述太赫兹激光器包括激发光源、光波导单元和太赫兹谐振单元,所述光波导单元一端连接所述激发光源；所述太赫兹谐振单元包括第一太赫兹反射镜、第二太赫兹反射镜、工作物质承载箱以及设置在工作物质承载箱内的工作物质,所述工作物质承载箱设置有激发光入射窗,所述光波导单元另一端接入所述激发光入射窗；所述第一太赫兹反射镜与所述第二太赫兹反射镜共轴,且所述工作物质承载箱设置在所述第一太赫兹反射镜以及所述第二太赫兹反射镜之间。调节第一太赫兹反射镜与第二太赫兹反射镜之间的距离即可以有效调节太赫兹输出激光的频率。(The invention discloses a terahertz laser based on optical excitation, which comprises an excitation light source, an optical waveguide unit and a terahertz resonance unit, wherein one end of the optical waveguide unit is connected with the excitation light source; the terahertz resonance unit comprises a first terahertz reflector, a second terahertz reflector, a working substance bearing box and a working substance arranged in the working substance bearing box, wherein the working substance bearing box is provided with an excitation light incidence window, and the other end of the optical waveguide unit is connected to the excitation light incidence window; the first terahertz reflector and the second terahertz reflector are coaxial, and the working substance bearing box is arranged between the first terahertz reflector and the second terahertz reflector. The frequency of the terahertz output laser can be effectively adjusted by adjusting the distance between the first terahertz reflector and the second terahertz reflector.)

1. The terahertz laser based on optical excitation is characterized by comprising an excitation light source, an optical waveguide unit and a terahertz resonance unit, wherein one end of the optical waveguide unit is connected with the excitation light source; the terahertz resonance unit comprises a first terahertz reflector, a second terahertz reflector, a working substance bearing box and a working substance arranged in the working substance bearing box, wherein the working substance bearing box is provided with an excitation light incidence window, and the other end of the optical waveguide unit is connected to the excitation light incidence window; the first terahertz reflector and the second terahertz reflector are coaxial; the first terahertz reflector and the second terahertz reflector are respectively arranged at two ends of the working substance bearing box.

2. The terahertz laser based on optical excitation according to claim 1, wherein two terahertz transmission mirrors are arranged at two ends of the working substance carrying box; the two terahertz transmission mirrors are arranged at two ends of the working substance bearing box respectively, and are opposite to the first terahertz reflector and the second terahertz reflector respectively.

3. The photoexcitation-based terahertz laser according to claim 2, wherein the two terahertz transmission mirrors and the two terahertz reflection mirrors, wherein the terahertz transmission mirror near the first terahertz reflection mirror is replaced with the first terahertz reflection mirror and is disposed at the terahertz transmission mirror position near the first terahertz reflection mirror, and wherein the terahertz transmission mirror near the second terahertz reflection mirror and the second terahertz reflection mirror can be replaced with one second terahertz reflection mirror and are disposed at the terahertz transmission mirror position near the second terahertz reflection mirror.

4. The terahertz laser based on optical excitation according to claim 2, wherein an excitation light reflector is arranged in the working substance carrying box opposite to the excitation light incident window; the distance between the excitation light reflector and the excitation light incidence window is half integral multiple of the wavelength of the excitation light; excitation light of the excitation light source enters the working substance from the excitation light entrance window through the optical waveguide unit in a direction perpendicular to the coaxial direction of the first terahertz reflector and the second terahertz reflector.

5. The terahertz laser based on photoexcitation, as set forth in claim 1, wherein the terahertz resonance unit further comprises an insulating layer that wraps the working substance carrying tank.

6. The terahertz laser based on optical excitation according to claims 1-2, further comprising a frequency control unit connected with the first terahertz mirror to control a distance between the first terahertz mirror and the second terahertz mirror.

7. The photoexcitation-based terahertz laser according to claim 6, further comprising a temperature sensor inside the working substance carrying tank, wherein the temperature sensor is connected to the frequency control unit.

8. The terahertz laser based on optical excitation according to claim 1, further comprising a power control unit connected with the excitation light source to control the power emitted by the excitation light source.

9. The photoexcitation-based terahertz laser according to claim 1, wherein the reflectance of the first terahertz mirror is in a range of 90% to 100%, and the transmittance of the first terahertz mirror is 0.

10. The photoexcitation-based terahertz laser of claim 9, wherein the reflectivity of the second terahertz mirror is in a range of 90% to 99%.

11. The photoexcitation-based terahertz laser according to claim 10, wherein the transmittance of the second terahertz mirror is 1% to 10%.

12. The photoexcitation-based terahertz laser according to claim 1, wherein the working substance is an organic substance and/or an inorganic substance.

Technical Field

The invention relates to the field of terahertz lasers, in particular to a terahertz laser based on optical excitation.

Background

Terahertz technology has wide applications in communication, sensing, remote sensing, security, drug detection, medical treatment, radar and the like, and has been widely regarded in recent years. The existing terahertz light mainly realizes the generation of terahertz laser based on technologies such as electronic technology frequency conversion, vacuum technology free electron devices, semiconductor technology quantum cascade devices, optical down-conversion and the like, but the existing terahertz source has the problems of low efficiency, low power, inconvenience in adjustment and the like, and cannot meet the current use requirement.

Disclosure of Invention

The invention mainly aims to provide a terahertz laser which is high in output power, high in efficiency, small in size and capable of conveniently adjusting terahertz wave output frequency.

In order to achieve the purpose, the invention provides a terahertz laser, which comprises an excitation light source, an optical waveguide unit and a terahertz resonance unit, wherein one end of the optical waveguide unit is connected with the excitation light source; the terahertz resonance unit comprises a first terahertz reflector, a second terahertz reflector, a working substance bearing box and a working substance arranged in the working substance bearing box, wherein the working substance bearing box is provided with an excitation light incidence window, and the other end of the optical waveguide unit is connected to the excitation light incidence window; the first terahertz reflector and the second terahertz reflector are coaxial, and the first terahertz reflector and the second terahertz reflector are respectively arranged at two ends of the working substance bearing box.

Furthermore, two ends of the working substance bearing box are provided with two terahertz light-transmitting mirrors, and the working substance is positioned in the working substance bearing box; the two terahertz transmission mirrors are arranged at two ends of the working substance bearing box respectively, and are opposite to the first terahertz reflector and the second terahertz reflector respectively.

Further, two terahertz printing opacity mirrors and two terahertz reflectors, wherein the terahertz printing opacity mirror that is close to first terahertz reflector is used with first terahertz reflector the first terahertz reflector replaces to set up in being close to first terahertz reflector terahertz printing opacity mirror position, wherein the terahertz printing opacity mirror that is close to second terahertz reflector can be replaced with a second terahertz reflector with second terahertz reflector, and set up in being close to second terahertz reflector's terahertz printing opacity mirror position department.

Furthermore, an excitation light reflector is arranged in the working substance bearing box and is positioned opposite to the excitation light incidence window; the distance between the excitation light reflector and the excitation light incidence window is half integral multiple of the wavelength of the excitation light; excitation light of the excitation light source enters the working substance from the excitation light entrance window through the optical waveguide unit in a direction perpendicular to the coaxial direction of the first terahertz reflector and the second terahertz reflector.

Further, the terahertz resonance unit further comprises a heat insulating layer, and the heat insulating layer wraps the working substance bearing box.

Further, the terahertz laser further comprises a frequency control unit, and the frequency control unit is connected with the first terahertz reflector to control the distance between the first terahertz reflector and the second terahertz reflector.

Further, still include temperature sensor in the work material bears the weight of the case, temperature sensor with the frequency control unit is connected.

Further, the terahertz laser further comprises a power control unit, and the power control unit is connected with the excitation light source to control the power emitted by the excitation light source.

Further, the reflectivity range of the first terahertz reflector is 90% -100%, and the transmissivity of the first terahertz reflector is 0.

Further, the reflectivity range of the second terahertz reflector is 90% -99%.

Further, the transmissivity of the second terahertz reflector is 1% -10%.

Further, the working substance is organic and/or inorganic.

The terahertz laser has the beneficial effects that the molecular spontaneous emission light is broadband, and the frequency of the terahertz output laser is mainly determined by the resonance frequency of the terahertz resonant cavity. Therefore, the frequency of the terahertz output laser can be effectively adjusted by adjusting the distance between the first terahertz reflector and the second terahertz reflector.

Drawings

Fig. 1 is a block diagram of a terahertz laser according to a first embodiment of the present invention;

fig. 2 is a schematic structural diagram of a terahertz laser according to a first embodiment of the present invention;

fig. 3 is a schematic structural diagram of a terahertz resonance unit of a terahertz laser according to a second embodiment of the present invention;

the implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terms "first," "second," "third," "fourth," and the like in the description and in the claims of the present application and in the drawings described above, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that the embodiments described herein may be practiced otherwise than as specifically illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

It should be noted that the description relating to "first", "second", etc. in the present invention is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

Referring to fig. 1, an embodiment of the present invention provides a terahertz laser based on optical excitation, in which an excitation light emitted by an excitation light source 10 excites a working substance, a molecular motion speed of the working substance in a terahertz resonance unit 30 is accelerated, and a terahertz spontaneous emission wave is generated, and the terahertz spontaneous emission wave forms terahertz laser through cooperation of the terahertz resonance unit.

Referring to fig. 2, the terahertz laser includes an excitation light source 10, an optical waveguide unit 20 and a terahertz resonance unit 30, wherein one end of the optical waveguide unit 20 is connected to the excitation light source 10; the terahertz resonance unit 30 comprises a first terahertz reflector 301, a second terahertz reflector 302, a working substance carrying box 303 and a working substance arranged in the working substance carrying box 303, wherein the working substance carrying box 303 is provided with an excitation light incident window 304, and the other end of the optical waveguide unit 20 is connected to the excitation light incident window 304; the first terahertz reflector 301 and the second terahertz reflector 302 are coaxial, and the first terahertz reflector 301 and the second terahertz reflector 302 are respectively arranged at two ends of the working substance bearing box 303.

In this embodiment, an output port of an excitation light source of an optical waveguide unit 20 is connected to the excitation light incident window 304, excitation light excited by an excitation light source 10 is transmitted through the optical waveguide unit 20, and is guided into a working substance carrying box 303 through the excitation light incident window 304 in a single direction, the working substance in the working substance carrying box 303 is heated, and spontaneous radiation including terahertz waves is performed on the working substance, a first terahertz mirror 301 and a second terahertz mirror 302 are arranged at two ends of the working substance carrying box 303 to form a terahertz resonant cavity 309, the terahertz waves form terahertz laser through cooperation of the terahertz resonant unit 303, a resonant frequency of the terahertz resonant cavity 309 is equal to a frequency of the emitted terahertz waves, specifically, the excitation light source 10 can be an incandescent lamp, L ED, a halogen lamp, an arc lamp, a mercury lamp, a fluorescent lamp, a sodium lamp, a laser or the like, a working wavelength of the excitation light source 10 is between 180 nanometers and 10 micrometers, the optical waveguide unit 20 can be a cavity waveguide, a dielectric waveguide, an optical fiber or the like, the first terahertz mirror 301 and the second terahertz mirror 302 are metal or dielectric reflector 302, the terahertz mirror 301 and the terahertz reflector are in a range from 0% terahertz reflection, the terahertz reflection ratio of the second terahertz reflector 301 to 90% of the terahertz reflector 302 is equal to 1% of the terahertz reflection mirror 301, the terahertz reflection mirror 301 and the terahertz reflection of the terahertz reflection mirror 302 of the terahertz reflection mirror 301.

Preferably, two terahertz light-transmitting mirrors 305 are arranged at two ends of the working substance bearing box 303, the two terahertz light-transmitting mirrors 305 are respectively arranged at two ends of the working substance bearing box 303, and the two terahertz light-transmitting mirrors 305 are respectively opposite to the first terahertz reflector 301 and the second terahertz reflector 302.

Specifically, the terahertz waves spontaneously radiated by the working substance in the working substance carrying box 303 generate terahertz laser light through the cooperation of the terahertz resonance unit 30 including the terahertz transmission mirror 305, the first terahertz mirror 301, the working substance and the second terahertz mirror 302.

Further, referring to fig. 3, the two terahertz transmission mirrors and the two terahertz reflection mirrors, wherein the terahertz transmission mirror 305 and the first terahertz reflection mirror 301 close to the first terahertz reflection mirror 301 can be replaced by one first terahertz reflection mirror 301 and are disposed at the position of the terahertz transmission mirror 305 close to the first terahertz reflection mirror 301, and wherein the terahertz transmission mirror 305 and the second terahertz reflection mirror 302 close to the second terahertz reflection mirror 302 can be replaced by one second terahertz reflection mirror 302 and are disposed at the position of the terahertz transmission mirror 305 close to the second terahertz reflection mirror 302.

Preferably, an excitation light reflecting mirror 3031 is arranged in the working substance carrying box 303 and opposite to the excitation light incidence window 304; the distance between the excitation light reflecting mirror 3031 and the excitation light entrance window 304 is half integral multiple of the wavelength of the excitation light. Excitation light of the excitation light source 10 passes through the optical waveguide unit 20, and enters the inside of the working substance from the excitation light entrance window 304 perpendicularly to the coaxial directions of the first terahertz reflecting mirror 301 and the second terahertz reflecting mirror 302. It can be understood that by controlling the distance between the excitation light reflecting mirror 3031 at the upper wall 3032 of the working substance bearing box 303 and the excitation light incidence window 304 at the lower wall 3033, the excitation light can be in a resonance state in the working substance bearing box 303 to generate a strongest excitation light field, so that the efficiency of the excitation light for exciting the working substance to generate terahertz spontaneous radiation is greatly improved. In order to realize the resonance of the excitation light in the working substance bearing box 303, the optical distance between the excitation light reflection mirror 3031 at the upper wall 3032 of the working substance bearing box 303 and the excitation light incidence window 304 at the lower wall 3032 is integral multiple of the wavelength of the excitation light, and the excitation light is required to enter the working substance perpendicularly to the coaxial direction of the first terahertz reflection mirror 301 and the second terahertz reflection mirror 302.

Preferably, the terahertz resonance unit 30 further comprises a heat insulating layer 307, and the heat insulating layer 307 wraps the working substance carrying box 303. Specifically, the spontaneous radiation frequency of the working substance in the working substance carrying box 303 is greatly influenced by the temperature, and in order to avoid the influence of the temperature on the spontaneous radiation, the working substance carrying box 303 needs to be wrapped by the heat insulating layer 307 so as to reduce the influence of the external environment temperature on the frequency of the terahertz laser. The insulation layer 307 may wrap around the surface of the work material carrier box 303.

Preferably, the terahertz laser further comprises a frequency control unit 40, wherein the frequency control unit 40 is connected with the first terahertz mirror 301 to control the distance between the first terahertz mirror 301 and the second terahertz mirror 302.

Specifically, since the equivalent optical distance between the first terahertz mirror 301 and the second terahertz mirror 302 is an integral multiple of the half wavelength of the working terahertz wave, the frequency of the terahertz laser is adjusted by controlling the equivalent optical distance between the first terahertz mirror 301 and the second terahertz mirror 302. In some embodiments, the working substance carrier tank 303 further comprises a temperature sensor 308, wherein the temperature sensor 308 is connected to the frequency control unit 40. The frequency control unit 40 can control the distance between the first terahertz mirror 301 and the second terahertz mirror 302 according to the change of the temperature sensor 308.

Preferably, the terahertz laser further comprises a power control unit 40, and the power control unit 40 is connected with the excitation light source 10 to control the power emitted by the excitation light source 10.

Specifically, the frequency of the terahertz waves spontaneously radiated by the working substance is influenced by temperature, and the temperature of the working substance can be adjusted by adjusting the power of the exciting light emitted into the working substance, so that the frequency of the terahertz waves spontaneously radiated can be controlled.

Further, the working substance is organic and/or inorganic.

Preferably, the working substance is organic.

Specifically, the working substance carrier box 303 may contain only organic substances or only inorganic substances, or a mixture of organic substances or inorganic substances. Specifically, the organic substance of the working substance may be ketones, aldehydes, ethane, propane, butane, pentane, hydrocarbon mixtures, ethylene, propylene, butene, olefinic mixtures, freon, saturated hydrocarbons, unsaturated hydrocarbons, azeotropic mixtures, or the like. The inorganic substance of the working substance may be air, carbon dioxide, oxygen, nitrogen, hydrogen, sulfur dioxide, or the like, and the specific substances of the organic substance and the inorganic substance are not limited herein. Furthermore, the working substance may be a solid, a liquid or a gas, which is not limited herein.

It can be understood that the working substance is excited by the excitation light to transition to a high-energy level, the movement of the molecular atoms and the lattice therein is accelerated, and since the molecular atoms all carry charges, the accelerated movement of the molecular atomic nucleus lattice is necessarily accompanied by the accelerated movement of the charges, and according to the classical physics theory, the accelerated movement of the charges generates spontaneous radiation, and according to the quantum mechanics theory, the molecular atoms transition to the high-energy level and then spontaneously transition to a low-energy level to generate spontaneous radiation. The frequency of this spontaneous emission depends on the energy difference of the energy levels before and after the transition. Setting the molecule at energy level E without light excitation₁State (corresponding to temperature T)₁) And reaches an energy level E after being excited by light₂State (corresponding to temperature T)₂) The molecule consists of energy level E₂Spontaneous transition to E₃The frequency v of the spontaneous radiation is expressed by formula (1):

υ＝h-¹(E₂-E₃)＝h-¹ΔE………………….(1)

where h is the Planckian constant. When the temperature rise amount of the working substance is increased, a larger transition energy difference can be obtained, that is, a part of the increase amount of the internal energy of the molecule caused by the temperature rise can be converted into spontaneous radiant energy when the molecule transits from the excited state to the lower energy level, and the formula (2) is expressed as follows:

where q is the conversion coefficient, i is the degree of freedom of the molecule, k is the Boltzmann constant, and Δ T is the energy level E of the molecule₂Working substance temperature corresponding to state and at energy level E₃The difference in temperature of the working substance corresponding to the state. Formula (3) is obtained from formulas (1) and (2):

that is, adjusting the power of the excitation light source can adjust the frequency of the spontaneous emission. Meanwhile, when the power of the excitation light is increased, more molecular transitions can be excited, so that the power of the terahertz output laser is increased.

Using a monatomic gas as an example of a working substance, for monatomic molecules: i is 3, q is 0.6, according to formula (3), Δ T is 5.333K, and ν is 0.1000097 THz; getting v 0.2000383THz by taking T10.667K; v is 0.300048THz obtained by taking Δ T as 16K; getting v 0.4000577THz by taking T21.333K; getting v 0.5000853THz by taking T26.667K; v is 0.600096THz obtained by taking Δ T32K; getting v 0.7001057THz by taking T37.333K; getting v 0.8001343THz by taking T42.667K; v is 0.900144THz obtained by taking Delta T as 48K; getting v 1.000154THz by taking T53.333K; getting v 2.0003263THz by taking T106.667K; getting Δ T160K, which can get ν 3.00048 THz; getting v 4.000634THz by taking T213.333K; getting v 5.0007963THz by taking T266.667K; v is 10.000154THz obtained by taking Δ T as 533.333K.

Taking a diatomic gas as an example of a working substance, such as nitrogen, for diatomic molecules: when i is 5, q is 0.7, and Δ T is 2.757K according to formula (3), ν is 0.1005318 THz; getting v 0.5000686THz by taking T13.714K; getting v 1.000136THz by taking T27.428K; getting v 2.0003098THz by taking T54.857K; getting v 5.0007587THz by taking T137.142K; getting v 10.001574THz by taking T274.285K; getting v 20.003184Hz by taking the delta T548.571K; v is 30.0047948THz obtained by taking Δ T as 822.857K.

Taking a polyatomic gas as an example of the working substance, taking q as 0.75 for a polyatomic gas i as 6, taking Δ T as 2.133K according to formula (3), and obtaining ν as 0.1000004 THz; getting v 0.5000477THz by taking T10.666K; getting v 1.0001444THz by taking T21.333K; getting v 2.00028875THz by taking T42.666K; getting v 3.00048THz by getting Δ T64K; getting v 4.0006244THz by taking T85.333K; getting v 5.0007587THz by taking T106.666K; getting v 10.00144THz by taking T213.333K; getting v 20.00288THz by taking T426.666K; v is 30.00432THz obtained by taking Δ T as 639.999K.

Consider the case of using elastic molecules (e.g., large organic molecules) below.

Taking methane as an example of the working substance, the chemical formula CH₄Where i is 15, q is 0.375, and Δ T is 1.706K according to formula (3), so ν is 0.0999769 THz; getting v 0.5000605THz by taking T8.533K; getting v 1.0001209THz by taking T17.066K; getting v 2.0003005THz by taking T34.133K; getting v 3.00048THz by getting Δ T51.2K; getting v 4.0006009THz by taking T68.266K; getting v 5.0007705THz by taking T85.333K; getting v 10.0015409THz by taking T170.666K; getting v 20.0031405THz by taking T341.333K; v is 30.00474THz obtained by taking Δ T512K.

Ethane (ethane) is taken as an example of a working substance, and the molecular formula of the ethane (ethane) is C₂H₆Where i is 24, q is 0.3, and Δ T is 1.333K according to formula (3), so that ν is 0.099991 THz; v is 0.500029THz obtained by taking Δ T as 6.666K; getting v 1.000135THz by taking T13.333K; v is 2.000270THz obtained by taking Δ T26.666K; v is 3.00048THz obtained by taking Delta T40K; getting v 4.000615THz by taking T53.333K; getting v 5.000740THz by taking T66.666K; getting v 10.001575THz by taking T133.333K; get v ═ 266.666K by taking Δ T ═ 266.666K20.00315 THz; v is 30.0048THz obtained by taking Δ T as 400K.

Preferably, the terahertz laser further comprises a power supply 60, and the power supply 60 is connected to the frequency control unit 40, the power control unit 50 and the excitation light source 10 to supply energy to the frequency control unit 40, the power control unit 40 and the excitation light source 10, wherein the power supply 60 is an ac or dc power supply and has a voltage between 6V and 380V. The terahertz laser further includes a working parameter display unit 70 for displaying parameters such as the frequency, power voltage, power of the excitation light source, and temperature in the working substance carrying box 303 of the laser output from the terahertz laser.

In the present embodiment, the spontaneous radiation generally has a relatively wide frequency band, wherein only the spontaneous radiation of a frequency corresponding to the resonance frequency of the terahertz resonance unit 30 is amplified in the terahertz resonance unit 30 to generate the terahertz laser light. With the generation of the terahertz laser, a large number of molecules perform spontaneous radiation corresponding to the frequency of the terahertz laser, so that other spontaneous radiation frequencies are relatively inhibited, and the conversion efficiency from the exciting light power to the terahertz laser power is improved. This is what the traditional terahertz wave can not be obtained by relying on black body radiation. In the device, since the molecular spontaneous emission light is broadband, the frequency of the terahertz output laser is mainly determined by the resonance frequency of the terahertz resonant cavity 309. Therefore, the frequency of the output terahertz laser can be effectively adjusted by adjusting the distance between the first terahertz mirror 301 and the second terahertz mirror 302.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.