Electromagnetic shielding cover formed based on ultrafast laser plasma

Abstract

The invention discloses an electromagnetic shielding case formed based on ultrafast laser plasma, and the electromagnetic shielding case comprises an ultrafast laser which is used for emitting ultrafast laser; the phase modulation element is used for carrying out annular modulation on the phase of the ultrafast laser to enable the cross section of a light beam to be in an annular shape; and the focusing device is used for pre-focusing the annular modulation light emitted by the phase modulation element in air to form a hollow cylindrical plasma cylinder, and the plasma cylinder is used for being nested at the periphery of equipment to be shielded so as to realize a signal shielding effect. Therefore, the generation and dissipation process of the ultrafast laser plasma is very rapid and can be completed on the nanosecond-level time scale, rapid response to electromagnetic waves can be achieved, and the method is suitable for occasions where the shielding effect needs to be dynamically adjusted.

Description

Technical Field

[0001] The present invention relates to an electromagnetic shielding cover composed of ultrafast laser plasma, and pertains to the technical field of electromagnetic shielding. Background Art

[0002] Existing electromagnetic shielding technologies mainly use metal materials, magnetic materials, or composite materials to make shielding covers for protecting electronic devices from external electromagnetic interference. However, the above-mentioned shielding covers have certain limitations, such as large weight, large volume, and intolerance to high temperatures.

[0003] In recent years, plasma technology has shown great potential in the field of electromagnetic shielding, with advantages such as high shielding efficiency and high temperature resistance. However, traditional plasma generation methods usually require complex equipment and technologies, such as using microwave discharge, radio frequency discharge, or DC discharge. The above methods require precise control and a large amount of energy input to stably generate and maintain plasma. In addition, traditional plasma generation methods cannot quickly respond to the dynamic changes of the electromagnetic environment, so they perform poorly in application scenarios where the shielding effect needs to be quickly adjusted. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, in view of the above problems, the object of the present invention is to provide an electromagnetic shielding cover composed of ultrafast laser plasma that can achieve a rapid response to electromagnetic waves.

[0005] To achieve the above object of the invention, the technical solution adopted by the present invention is as follows: An electromagnetic shielding cover composed of ultrafast laser plasma provided by the present invention, the electromagnetic shielding cover includes:

[0006] An ultrafast laser, the ultrafast laser is used to emit ultrafast laser;

[0007] A phase modulation element, the phase modulation element is used to perform circular modulation on the phase of the ultrafast laser so that the beam cross-section becomes circular;

[0008] A focusing device, the focusing device is used to pre-focus the circularly modulated light emitted by the phase modulation element so as to form a hollow cylindrical plasma cylinder in the air, and the plasma cylinder is used to be nested around the device to be shielded to achieve signal shielding.

[0009] In some possible embodiments, it further includes an attenuation element, and the attenuation element is arranged at the light output port of the ultrafast laser for adjusting the intensity of the ultrafast laser.

[0010] In some possible embodiments, by adjusting the parameters of the ultrafast laser, the optical density of the attenuation element, and / or the focal length of the focusing device, the plasma cylinder can shield electromagnetic waves in a specific frequency band.

[0011] In some possible embodiments, when the frequency of the electromagnetic wave is less than the frequency ω of the plasma cylinder p , the electromagnetic wave will be reflected or strongly attenuated by the plasma cylinder, achieving the effect of an electromagnetic shielding cover. Among them, the frequency ω of the plasma cylinder p is calculated by the formula:

[0012]

[0013] In the formula, n e is the electron density, e is the electron charge, ε0 is the vacuum permittivity, and m e is the electron mass.

[0014] In some possible embodiments, the ultrafast laser uses femtosecond laser, picosecond laser or nanosecond laser. Among them, the plasma cylinder can exist or disappear with the switching of the ultrafast laser.

[0015] In some possible embodiments, the phase modulation element uses a vortex phase plate, a conical lens or a holographic stop sheet with an annular modulation effect.

[0016] In some possible embodiments, the focusing device uses a focusing lens or a focusing lens group.

[0017] In some possible embodiments, the focusing device can control the electron density, length and / or generation position of the plasma cylinder. The focusing device controls the electron density, length and / or generation position of the plasma cylinder by adjusting the focal length of the focusing device or replacing the focusing device with different focal lengths.

[0018] Due to the above technical solutions adopted by the present invention, it has the following characteristics:

[0019] 1. Fast response and dynamic adjustment: By adding a phase modulation element with an annular modulation effect after the ultrafast laser in the present invention, and then focusing to form a hollow cylindrical plasma structure for electromagnetic shielding. The generation and dissipation processes of the ultrafast laser plasma are very rapid and can be completed on a time scale of nanoseconds, which means that this shielding device can achieve a fast response to electromagnetic waves and is suitable for occasions where the shielding effect needs to be dynamically adjusted.

[0020] 2. Frequency Band Selectivity: The present invention has the characteristic of frequency band selection. By adjusting the parameters of the ultrafast laser, the optical density of the attenuation element, and / or the focal length of the focusing lens, the electron density of the plasma can be changed, thereby affecting the plasma frequency, achieving the shielding of electromagnetic waves in specific frequency bands and allowing electromagnetic waves in other frequency bands to pass through, that is, having a shielding effect with frequency band selectivity.

[0021] 3. Turn-on and Use Immediately and Flexible Adaptability: Compared with the physical electromagnetic shielding cover, the present invention has the characteristic of turn-on and use immediately, which is more convenient for arrangement and withdrawal, and the diameter of the shielding cover can be adjusted through the design of the phase modulation element to adapt to antennas or devices of different shapes and sizes.

[0022] 4. High Tolerance Threshold: The present invention has good high tolerance threshold performance and is applicable to various high-temperature environments.

[0023] In summary, the present invention has the advantages of high-efficiency shielding, high temperature resistance, and frequency selectivity, and is particularly applicable to antennas or devices in extreme electromagnetic environments, providing a new direction and possibility for the development of electromagnetic shielding technology. Description of the Drawings

[0024] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0025] Figure 1 It is a schematic structural diagram of the electromagnetic shielding cover according to an embodiment of the present invention.

[0026] Figure 2 It is the cross-section of the ultrafast laser beam modulated by the phase modulation element according to an embodiment of the present invention. It can be seen that the beam cross-section is annular. Among them, (a) is the use of a vortex phase plate; (b) is the use of a conical lens; (c) is the use of a holographic phase plate.

[0027] Figure 3 It is the shielding effect of the plasma electromagnetic shielding cover according to an embodiment of the present invention. Among them, (a) is the plasma shielding cover closed; (b) is the plasma shielding cover opened, where the arrow is the direction of the electric field.

[0028] Figure 4 It is the far-field gain attenuation effect of the plasma electromagnetic shielding cover on the antenna according to an embodiment of the present invention. Among them, (a) is the plasma shielding cover closed; (b) is the plasma shielding cover opened.

[0029] Figure 5 It is the effect of the plasma shielding cover with different electron densities on antennas with different operating wavelengths according to an embodiment of the present invention. Among them, (a) the electron density is 1*1015 / cm 3 ; (b) The electron density is 1*10 17 / cm 3 ; (c) The electron density is 1*10 19 / cm 3 ; wherein:

[0030] The reference signs in the drawings are: 1 - ultrafast laser, 2 - attenuation element, 3 - phase modulation element, 4 - focusing lens, 5 - plasma cylinder, 6 - antenna. Detailed implementation manners

[0031] It should be understood that the terms used herein are for the purpose of describing particular example embodiments only and are not intended to be limiting. Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" as used herein may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of the stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the particular order described or illustrated, unless the order of performance is explicitly stated. It should also be understood that additional or alternative steps may be used.

[0032] Although the terms first, second, third, etc. may be used herein to describe multiple elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another. Unless the context clearly dictates otherwise, terms such as "first", "second", and other numerical terms as used herein do not imply an order or sequence. Thus, the first element, component, region, layer, or section discussed below may be referred to as the second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0033] For ease of description, spatial relative relationship terms may be used herein to describe the relationship of one element or feature shown in the figure to another element or feature, such as "inside", "outside", "inner side", "outer side", "below", "above", etc. Such spatial relative relationship terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figure.

[0034] High-intensity ultrafast lasers, such as femtosecond lasers, can generate high-concentration plasmas after focusing. These plasmas have very high electrical conductivity and can effectively absorb and reflect electromagnetic waves, promising efficient and dynamic electromagnetic shielding. In addition, the intensity, wavefront, etc. of ultrafast lasers can be precisely controlled, thereby achieving precise adjustment of plasma characteristics (such as electron density, electron temperature, and distribution) to meet specific shielding requirements for electromagnetic waves of different frequencies. Moreover, ultrafast laser plasmas have a relatively high tolerance threshold, can withstand high temperatures, and are suitable for electromagnetic shielding in extreme environments. The electromagnetic shielding cover based on ultrafast laser plasmas provided by the present invention includes: an ultrafast laser for emitting ultrafast laser; a phase modulation element for performing circular modulation on the phase of the ultrafast laser to make the beam cross-section circular; a focusing device for pre-focusing the circularly modulated light emitted by the phase modulation element to form a hollow cylindrical plasma cylinder in the air, and the plasma cylinder is used to nest around the device to be shielded to achieve signal shielding. Therefore, the present invention has characteristics such as fast response, frequency band selection, strong spatial adaptability, and high tolerance threshold, and can provide efficient electromagnetic shielding effects in various environments, especially suitable for application scenarios that require dynamic adjustment of shielding effects and extreme environments.

[0035] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0036] Example 1: As Figure 1 shown, the electromagnetic shielding cover based on ultrafast laser plasmas provided by the present invention includes an ultrafast laser 1, an attenuation element 2, a phase modulation element 3, and a focusing lens 4.

[0037] The ultrafast laser 1 sequentially emits the collimated ultrafast laser to the attenuation element 2 and the phase modulation element 3. The attenuation element 2 is used to adjust the intensity of the ultrafast laser, and the phase modulation element 3 is used to perform circular modulation on the phase of the ultrafast laser to make the beam cross-section circular. The circularly modulated light emitted by the phase modulation element 3 is pre-focused by the focusing lens 4 to form a hollow cylindrical plasma cylinder 5 in the air, and the plasma cylinder 5 is used to nest around the device to be shielded, such as an antenna 6, to achieve a signal shielding effect.

[0038] In a preferred embodiment, the formation principle of the plasma cylinder 5 is as follows: for a Gaussian-shaped ultrafast pulsed laser during propagation, the nonlinear Kerr effect in air will cause self-focusing, while the formation of plasma leads to a defocusing effect. The two interact to reach a dynamic equilibrium, thus forming a stable plasma filament with a diameter on the order of hundreds of micrometers on the laser path. Similarly, for the propagation of an annular ultrafast laser beam in air, due to the dynamic equilibrium of the self-focusing and defocusing effects, a hollow plasma cylinder 5 can be formed on the laser path. By adjusting the parameters of the ultrafast laser 1, the optical density of the attenuation element 2, and the focal length of the focusing lens 4, the shielding of specific frequency band electromagnetic waves by the plasma can be achieved. Among them, the parameters of the ultrafast laser 1, the optical density of the attenuation element 2, and the focal length of the focusing lens 4 all affect the electron density of the plasma, and the implementer can adjust them according to requirements during the implementation process. For example, if the electron density is too small, the output power of the ultrafast laser 1 can be increased, the optical density of the attenuation element 2 can be decreased, or the focusing lens 4 can be replaced with a focusing lens 4 with a shorter focal length.

[0039] Furthermore, the correspondence between the plasma electron density and its shieldable frequency band can be calculated according to the plasma cylinder frequency ω p using the formula:

[0040]

[0041] where n e is the electron density, with the unit of m -3 , e is the electron charge, 1.6×10 -19 C, ε0 is the vacuum permittivity, 8.85×10 -12 F / m, m e is the electron mass, 9.1×10 -31 kg.

[0042] When the frequency of the electromagnetic wave is less than ω p , the electromagnetic wave will be reflected or strongly attenuated by the plasma cylinder 5, achieving the effect of an electromagnetic shielding cover. For example, for a plasma with an electron density of about 10 16 m -3 , the frequency of the plasma cylinder 5 is about in the GHz level, so it can shield short-wave communications in the MHz band, but it is non-shielding for THz waves. If it is required to shield the terahertz band, the three factors of the parameters of the ultrafast laser 1, the optical density of the attenuation element 2, and / or the focal length of the focusing lens 4 can be adjusted according to the aforementioned method to increase the electron density of the plasma cylinder 5 to achieve the effect.

[0043] In a preferred embodiment, the function of the attenuation element 2 is to adjust the laser intensity to control the electron density of the air plasma excited by it. If the ultrafast laser 1 itself has the function of adjusting the output laser intensity, the attenuation element 2 can be omitted.

[0044] In a preferred embodiment, the ultrafast laser 1 can use high-peak-intensity and short-pulse-width pulsed lasers such as femtosecond lasers, picosecond lasers, or nanosecond lasers. The plasma cylinder 5 can exist or disappear with the switching of the ultrafast laser 1, which is convenient for arrangement and cancellation.

[0045] In a preferred embodiment, as Figure 2 shown, the phase modulation element 3 can use a vortex phase plate, a conical lens, or a holographic stop with an annular modulation effect. Taking this as an example, it is not limited to this.

[0046] In a preferred embodiment, the focusing lens 4 is used to shorten the process of self-focusing to form the plasma cylinder 5 and precisely control the electron density, length, and generation position of the plasma cylinder 5. The specific control process is as follows:

[0047] (1) Controlling the electron density: The femtosecond laser can be focused to a very small spot size through the focusing lens 4, thereby generating extremely high light intensity at the focal point. This high light intensity can cause air ionization to form a plasma with a high electron density. Adjusting the focal length of the focusing lens 4 or replacing the focusing lens 4 with a different focal length can change the spot size, thereby affecting the light intensity and electron density at the focal point.

[0048] (2) Controlling the plasma length: The focal length of the focusing lens 4 determines the focusing depth of the femtosecond laser in the material. The shorter the focal length, the smaller the focusing depth, and the shorter the length of the plasma cylinder 5. By selecting an appropriate focal length of the focusing lens 4, the formation length of the plasma cylinder 5 can be controlled.

[0049] (3) Controlling the plasma position: The position where the plasma cylinder 5 is generated is generally near the focal point of the used focusing lens 4. Therefore, by selecting focusing lenses 4 with different focal lengths, the generation position of the plasma cylinder 5 can be controlled. If necessary, a focusing lens group can be used to achieve the effect.

[0050] In a preferred embodiment, the plasma cylinder 5 has spatial adaptability and can adapt to shielded devices of different shapes and sizes. The device to be shielded by the plasma cylinder 5, such as the antenna 6, can be of any shape within a limited size, which is not limited here.

[0051] The following details the generation process of the electromagnetic shielding cover composed of ultrafast laser plasma according to the present invention through specific embodiments. The specific process is as follows:

[0052] 1. A femtosecond laser with a wavelength of 800 nm, a single-pulse energy of 7 mJ, a pulse width of 35 fs, and a repetition frequency of 1 kHz emits femtosecond laser pulses.

[0053] 2. The femtosecond laser is phase-modulated by a vortex phase plate so that the laser cross-section becomes annular, as shown in Figure 2 (a).

[0054] 3. The annular modulated light after being modulated by the vortex phase plate is focused by a focusing lens 4 with a focal length of 10 m to form a hollow cylindrical femtosecond laser plasma cylinder.

[0055] 4. Covering the femtosecond laser plasma cylinder on the antenna 6 can achieve electromagnetic shielding.

[0056] In this embodiment, the shielding effect and gain attenuation effect of the plasma cylinder 5 with an electron density of 8.5×10 22 / cm 3 on the 0.075 GHz electromagnetic wave electric field are as shown in Figure 3 and Figure 4 . It can be seen that the plasma cylinder 5 effectively shields the signal.

[0057] Furthermore, as shown in Figure 5 , by changing the electron density of the plasma and observing the S11 parameter in the same antenna operating band, for electromagnetic waves with a wavelength of 0.5 m - 4 m, as the electron density of the plasma electromagnetic shielding cover increases, the overall S11 parameter of the antenna rises. This indicates that the signal radiation from the antenna 6 inside the shielding cover to the outside signal decreases, showing that the increase in electron density improves the shielding ability of the plasma electromagnetic shielding cover. Among them, (a) the electron density is 1*10 15 / cm 3 ; (b) the electron density is 1*10 17 / cm 3 ; (c) the electron density is 1*10 19 / cm 3 . The experimental parameters can be adjusted according to different application scenario requirements to generate a plasma with a suitable electron density.

[0058] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other, and the key point of each embodiment is to illustrate the differences from other embodiments. In the description of this specification, the descriptions referring to terms such as "a preferred embodiment", "furthermore", "specifically", "in this embodiment", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of this specification. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electromagnetic shielding cover composed of ultrafast laser plasma, characterized in that, The electromagnetic shielding cover includes: An ultrafast laser, which is used to emit ultrafast laser light; A phase modulation element, which is used to perform an annular modulation on the phase of the ultrafast laser so that the beam cross-section becomes annular; A focusing device, which is used to pre-focus the annularly modulated light emitted from the phase modulation element so as to form a hollow cylindrical plasma cylinder in the air, and the plasma cylinder is used to be nested around the device to be shielded to achieve signal shielding.

2. The electromagnetic shielding cover formed based on ultrafast laser plasma according to claim 1, characterized in that, It further includes an attenuation element, which is arranged at the light output port of the ultrafast laser and is used to adjust the intensity of the ultrafast laser.

3. The electromagnetic shielding cover composed of an ultrafast laser plasma according to claim 2, characterized in that, By adjusting the parameters of the ultrafast laser, the optical density of the attenuation element and / or the focal length of the focusing device, the plasma cylinder realizes the shielding of electromagnetic waves in a specific frequency band.

4. The electromagnetic shielding cover formed based on ultrafast laser plasma according to claim 1, wherein When the frequency of the electromagnetic wave is less than the frequency ω of the plasma cylinder p will the electromagnetic wave be reflected or strongly attenuated by the plasma cylinder, achieving the effect of an electromagnetic shielding cover, where the frequency ω of the plasma cylinder p is calculated by the formula: Where n e is the electron density, e is the electron charge, ε0 is the vacuum permittivity, and m e is the electron mass.

5. The electromagnetic shielding cover formed based on ultrafast laser plasma according to claim 1, characterized in that, The ultrafast laser uses femtosecond laser, picosecond laser or nanosecond laser, wherein the plasma cylinder can exist or disappear with the switching on and off of the ultrafast laser.

6. The electromagnetic shielding cover formed based on ultrafast laser plasma according to claim 1, wherein, The phase modulation element uses a vortex phase plate, a conical lens or a holographic limiting plate with an annular modulation effect.

7. The electromagnetic shielding cover formed based on ultrafast laser plasma according to claim 1, characterized in that, The focusing device uses a focusing lens or a focusing lens group.

8. The electromagnetic shielding cover formed based on an ultrafast laser plasma according to claim 7, characterized in that, The focusing device can control the electron density, length and / or generation position of the plasma cylinder, and the focusing device controls the electron density, length and / or generation position of the plasma cylinder by adjusting the focal length of the focusing device or replacing the focusing device with different focal lengths.

Images