Super-large octave adjustable electromagnetic window based on photoconductive material

Abstract

The invention discloses an ultra-large octave adjustable electromagnetic window based on a photoconductive material, and belongs to the field of reconfigurable metasurfaces. The top end of the cavity is open, the electromagnetic surface is packaged at the open end of the cavity, and an optical driving module is arranged in the cavity; the optical driving module projects different patterns on an electromagnetic surface, and switches a band-pass / band-stop working mode through light-operated equivalent surface impedance; the electromagnetic surface comprises a dielectric plate and a photoconductive material film coated on the dielectric plate; the light driving module can project a preset light pattern on the electromagnetic surface, so that the equivalent impedance distribution of the electromagnetic surface is changed; the cavity is used for supporting the electromagnetic surface and absorbing reflected light of the photoconductive material film. The core problems of a traditional electromagnetic window in the aspects of bandwidth, response speed, loss and cost are solved.

Description

Technical Field

[0001] The present invention belongs to the field of reconfigurable metasurfaces, and particularly relates to an ultra-wide octave tunable electromagnetic window based on photoconductive materials. Background Art

[0002] As a kind of system that can dynamically regulate the propagation characteristics of electromagnetic waves, electromagnetic windows have shown great potential in wireless communication, radar detection, stealth technology, intelligent environment adaptation, etc. in recent years. The design of traditional electromagnetic windows mainly relies on metal patterning structures or phase change materials (such as vanadium dioxide) to achieve the regulation of electromagnetic properties. However, these technologies have obvious limitations: First, the tunable range of the band-pass or band-stop of metal patterning structures is usually narrow and it is difficult to cover a wide frequency spectrum range; Second, the response time of phase change materials is relatively long, and their phase change process is often accompanied by large energy consumption and complex control mechanisms; Third, designing electromagnetic surface structures with broadband and high-efficiency characteristics requires highly precise process control, resulting in high manufacturing costs.

[0003] In addition, with the rapid development of wireless communication technology, the requirements for the efficient utilization of spectrum resources and the in-depth perception of intelligent environments in 5G and future 6G communications have put forward higher requirements for the regulation ability of electromagnetic windows, including but not limited to ultra-wideband tunability, fast response, low-cost manufacturing, and intelligent control ability. Therefore, exploring new materials and technologies to achieve ultra-wide octave tunable, efficient and economical electromagnetic windows has become a hot and difficult point in current research.

[0004] Therefore, the present invention combines photoconductive materials with advanced electromagnetic regulation technologies to develop an ultra-wide octave tunable, fast-response, flexible design and cost-effective electromagnetic window to meet the urgent needs in future communication, radar detection, intelligent environment adaptation and other fields. Summary of the Invention

[0005] Technical Problems to be Solved

[0006] In order to avoid the deficiencies of the prior art, the present invention provides an ultra-wide octave tunable electromagnetic window based on photoconductive materials, which combines photoconductive materials and a light driving module. By illuminating, the conductive state of the electromagnetic surface is dynamically regulated, replacing traditional metal patterns or phase change materials, and realizing flexible reconstruction of electromagnetic properties; wherein the light driving module can generate dynamic patterns with micron-level resolution, and directly switch the band-pass / band-stop working mode by controlling the equivalent surface impedance, without complex physical structure modification. The present invention solves the core problems of traditional electromagnetic windows in terms of bandwidth, response speed, loss and cost.

[0007] The technical solution of the present invention is: an ultra-wide octave tunable electromagnetic window based on a photoconductive material, including a cavity with an open top end and an electromagnetic surface encapsulated at its open end, and a light driving module is arranged in the cavity; the light driving module projects different patterns on the electromagnetic surface, and switches between band-pass / band-stop working modes by optically controlling the equivalent surface impedance;

[0008] The electromagnetic surface is composed of a dielectric plate and a photoconductive material thin film coated on the dielectric plate;

[0009] The light driving module can project a preset light pattern on the electromagnetic surface, thereby changing the equivalent impedance distribution of the electromagnetic surface;

[0010] The cavity is used to support the electromagnetic surface and absorb the reflected light of the photoconductive material thin film.

[0011] A further technical solution of the present invention is: the dielectric plate is made of FR4 epoxy resin material; the photoconductive material thin film is a polyimide / copper phthalocyanine composite thin film with a thickness of 20 μm.

[0012] A further technical solution of the present invention is: the resistivity of the photoconductive material thin film in the illuminated area drops from 10 8 Ω·cm in the dark state to 10 3 Ω·cm in the photoconductive state. The equivalent impedance of the electromagnetic surface is dynamically regulated by the light driving module to realize the reconfigurable control of the electromagnetic wave transmission characteristics in the 1-40 GHz frequency band.

[0013] A further technical solution of the present invention is: the light driving module is a DLP projection system, including a 780 nm laser, an illumination lens group, a total reflection prism, a DMD chip, and a projection objective lens arranged in sequence along the optical path, and is used to project a dynamic pattern on the photoconductive material thin film.

[0014] A further technical solution of the present invention is: the DLP projection system adopts a telecentric optical path structure, and the illumination lens group includes a laser beam expander system and an 8×8 fly-eye lens array; among them, the input lens of the laser beam expander system has a focal length of -3.1 mm, the output lens has a focal length of 3.1 mm; the size of the fly-eye lens unit is 2.5 mm×1.88 mm.

[0015] A further technical solution of the present invention is: the working wavelength of the projection objective lens is 780 nm, the full field of view angle 2ω = 70°, and the aperture ratio F / # of the DMD chip is 2.4.

[0016] A further technical solution of the present invention is: the total reflection prism is made of K9 glass material, the refractive index n = 1.517, the incident beam has an incident angle greater than the critical angle on the prism surface to cause total reflection, and the reflected beam is modulated by the DMD chip and then transmitted out of the prism.

[0017] A further technical solution of the present invention is that the DMD chip is a 2048×1080 pixel array, the micromirror flipping speed is at the 10 μs level, the pattern refresh rate > 5 kHz, combined with the sub-millisecond-level optical response characteristics of the photoconductive material thin film, and the overall system response time ≤ 200 μs.

[0018] A further technical solution of the present invention is that the transmission efficiency of the electromagnetic window > 90%.

[0019] A further technical solution of the present invention is that the cavity depth is 50 cm, the bottom area is the same as the size of the electromagnetic surface, and the inner wall of the cavity is coated with an absorbent material with a reflectivity < 0.1%.

[0020] Beneficial effects

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. Ultra-large octave tunability (solving the problem of narrow tunable range in the background technology)

[0023] The present invention combines the optoelectronic characteristics of the photoconductive material thin film (such as polyimide / copper phthalocyanine composite thin film) with the high resolution of DLP projection for patterning control. By generating a dynamic conductive pattern (spatial resolution reaching the micron level) on the electromagnetic surface through a DLP projection system, the distribution state of the reconfigurable equivalent electromagnetic unit can be changed. Experiments show that under 780 nm laser irradiation, the resistivity of the 20 μm thick photoconductive material thin film decreases from 10 8 Ω·cm (dark state) to 10 3 Ω·cm (photoconductive state), covering 8 octaves from the L band (1 - 2 GHz) to the Ka band (26 - 40 GHz) (frequency span reaching 39 GHz). It realizes fast response and control (breaking through the response speed bottleneck of phase change materials).

[0024] Based on the micromirror flipping speed of the DMD chip (at the 10 μs level) and the photogenerated carrier relaxation time of the photoconductive material (< 100 μs). Using a 0.7-inch DMD chip (2048×1080 pixels) to achieve a pattern refresh rate > 5 kHz, combined with the sub-millisecond-level optical response characteristics of the photoconductive material. The overall system response time measured in the experiment ≤ 200 μs, which is 2 orders of magnitude higher than that of traditional vanadium dioxide phase change materials (response time > 1 ms). In the dynamic switching experiment, the transmission state switching delay of the electromagnetic window for the 1 - 40 GHz swept signal is 180 ± 20 μs (3σ confidence interval).

[0025] 2. Low loss and high integration (overcoming the complexity of traditional processes and insertion loss problems)

[0026] The electromagnetic surface of the present invention adopts a metal-free pattern design, realizes transmission regulation through optically controlled equivalent surface impedance, and avoids the high-frequency skin effect loss of traditional metal structures. Tests show that at the Ka band (30 GHz), the insertion loss is <1.2 dB (the typical value of the traditional metal array structure is >3 dB). The measured transmission efficiency by using a vector network analyzer (Keysight N5227B) is >90% (S21 = -0.46 dB at 30 GHz).

[0027] 3. Low cost and scalability (solving the problem of high-precision process cost)

[0028] The present invention utilizes the direct reuse and large-area coating process of commercial DLP projection components (including DMD chips and TIR prisms).

[0029] The present invention measures the transmission efficiency by using a vector network analyzer (Keysight N5227B) to be >90% (S21 = -0.46 dB at 30 GHz). Using laser direct writing projection to replace the lithography process, the manufacturing cost of a 50 cm × 50 cm electromagnetic surface is only 1 / 10 of that of the traditional EBL lithography process. The compound eye lens group (8×8 array) achieves a light field uniformity of >95% (the measured standard deviation σ < 2%), meeting the requirements of industrial mass production. Comparative tests show that under the same functional area, the processing cost of this solution is 120 / m 2 , while the processing cost of the traditional FSS is >120 / m 2 .

[0030] 4. Anti-interference and stability (coping with performance degradation in complex electromagnetic environments)

[0031] The present invention uses light-absorbing materials to suppress the stray light interference caused by the reflection of the photoconductive thin film (reflectivity <0.1%), and cooperates with a projection objective lens with F / # = 2.4 (depth of field ±2.5 mm) to ensure long-term working stability.

[0032] In summary, the technical solution of the present invention realizes an ultra-large octave, microsecond-level response, low-loss, and low-cost tunable electromagnetic window through the collaborative innovation of an electromagnetic surface based on photoconductive materials, DLP projection technology, and an absorbing cavity design. Its performance parameters exceed those of traditional metal / phase change material solutions and meet the stringent requirements of 5G / 6G communication and intelligent radar systems. Brief Description of the Drawings

[0033] Figure 1 It is a schematic diagram of the structural decomposition of the electromagnetic window in the embodiment of the present invention.

[0034] Figure 2 It is a typical structural diagram of an electromagnetic surface unit in the embodiment of the present invention.

[0035] Figure 3Schematic diagram of the band - pass electromagnetic surface structure and electromagnetic simulation model in the embodiments of the present invention.

[0036] Figure 4 is Figure 3 Schematic diagram of the transmission coefficients of different band - pass units in

[0037] Figure 5 Schematic diagram of the band - stop electromagnetic surface structure and electromagnetic simulation model in the embodiments of the present invention.

[0038] Figure 6 is Figure 5 Schematic diagram of the transmission coefficients of different band - stop units in

[0039] Figure 7 Schematic diagram of the DLP projection structure based on the DMD chip in the embodiments of the present invention.

[0040] Figure 8 Schematic diagram of the telecentric optical path structure using a TIR prism in the embodiments of the present invention.

[0041] Explanation of reference numerals: 1. Electromagnetic surface, 11. Dielectric plate, 12. Photoconductive material thin film; 2. DLP projection system, 21. Projection lens, 22. TIR prism, 23. DMD chip, 24. Illumination lens group, 25. 780nm laser; 3. Cavity. Detailed implementation manners

[0042] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0043] Based on the problem that the traditional electromagnetic window cannot achieve the ultra - large octave tunable technology, the present invention provides an ultra - large octave tunable electromagnetic window based on photoconductive materials. Through the collaborative design of the light - controlled characteristics of photoconductive materials, the dynamic patterning technology of DLP projection, and the cavity, the core problems of the traditional electromagnetic window in terms of bandwidth, response speed, loss, and cost are solved. Its performance advantages such as ultra - large octave coverage, micro - second - level response, low loss (<1.2dB), low cost (120 yuan / m 2 ) and high stability (temperature - change fluctuation σ < 0.15dB) provide a disruptive solution for fields such as high - frequency communication, intelligent radar, and electromagnetic stealth.

[0044] Among them, as a new type of functional material, the photoconductive material has received extensive attention in the fields of optoelectronics, display technology, and sensors due to its excellent optoelectronic conversion characteristics, good tunability, and relatively low cost. The organic material exhibits different resistance states under different light intensities. In the dark, it is approximately a dielectric, and in strong light conditions, it is approximately a conductor. Therefore, by using a light source sensitive to the photoconductive material to prepare a projection light source similar to a projector and irradiating the photoconductive material thin film, the illuminated part can be quickly switched to a conductive state or a low-resistance state. Through different projection pattern arrangements, the working state of the band-pass and band-stop can be flexibly switched, thereby realizing the rapid adjustment of electromagnetic wave transmission and forming a new reconfigurable working mechanism for electromagnetic surfaces. Applying the photoconductive material to the design of electromagnetic surfaces to achieve ultra-large octave tunability, integrating key components of large-scale digital micromirror arrays and electromagnetic information sensing modules, can solve the limitations of existing electromagnetic windows in terms of adjustable bandwidth, response speed, design complexity, and processing cost, and provide a high-performance and flexibly controllable electromagnetic window solution for fields such as radar systems, wireless communication, and intelligent reflecting surface design.

[0045] Based on this, the present invention designs an ultra-large octave tunable electromagnetic window based on a photoconductive material, which includes a cavity with an open top end and an electromagnetic surface encapsulated at its open end. A light driving module is arranged in the cavity; the light driving module projects different patterns on the electromagnetic surface and switches the band-pass / band-stop working mode by controlling the equivalent surface impedance optically; the electromagnetic surface is composed of a dielectric plate and a photoconductive material thin film coated on the dielectric plate; the light driving module can project a preset light pattern on the electromagnetic surface, thereby changing the equivalent impedance distribution of the electromagnetic surface; the cavity is used to support the electromagnetic surface and absorb the reflected light of the photoconductive material thin film.

[0046] The above technical solutions will be further described below in conjunction with the drawings and embodiments:

[0047] In one embodiment, referring to Figure 1 as shown, in this embodiment, the electromagnetic window includes three main parts: an electromagnetic surface 1, a DLP projection system 2, and a cavity 3.

[0048] Specifically, referring to Figure 1 as shown, the electromagnetic surface 1 is divided into two layers. One layer is a dielectric plate 11, and the other layer is a photoconductive material thin film 12 (coated on the dielectric plate). The electromagnetic surface 1 is supported by the cavity 3 and the side coated with the photoconductive material thin film 12 faces the inside of the cavity. The inner wall of the cavity 3 is coated with an absorbent material to absorb the light reflected by the photoconductive material thin film.

[0049] Specifically, referring to Figure 7As shown in the figure, the DLP projection system consists of a 780nm laser 25, an illumination lens group 24, a projection lens 21, a total internal reflection (TIR) prism 22, and a Digital Micro-Mirror Device (DMD) array chip 23, which is the core device of the projection. Based on the projection method of DLP technology, a telecentric optical path structure as shown in Figure 8 is selected as the overall structure of the entire laser projection system. The laser emitted by the 780nm laser 25 passes through a shaping and homogenizing lens group and enters the TIR prism 22. Total internal reflection occurs on the reflecting surface of the TIR prism and the light is incident on the surface of the DMD chip 23. After being modulated by the micromirrors, the light beam enters the TIR prism 22 again and finally forms an image on the electromagnetic surface 1 of the photoconductive material film through the projection objective lens.

[0050] In one embodiment, the dielectric plate 11 is made of FR4 epoxy resin material with a size of 20 inches (50cm × 50cm); the photoconductive material film 12 is a polyimide / copper phthalocyanine composite film with a thickness of 20μm.

[0051] Preferably, the resistivity of the photoconductive material film in the illuminated area drops from 10 8 Ω·cm in the dark state to 10 3 Ω·cm in the photoconductive state. By dynamically regulating the equivalent impedance of the electromagnetic surface through the light driving module, reconfigurable control of the electromagnetic wave transmission characteristics in the 1 - 40GHz frequency band is achieved.

[0052] In one embodiment, the illumination lens group 24 of the DLP projection system 2 includes a laser beam expander system and an 8×8 fly-eye lens array; the focal length of the input mirror of the laser beam expander system is -3.1mm, and the focal length of the output mirror is 3.1mm; the size of the fly-eye lens unit is 2.5mm × 1.88mm. The working wavelength of the projection objective lens 21 is 780nm, the full field of view angle 2ω = 70°, and the aperture ratio F / # of the DMD chip is 2.4. The total internal reflection prism is made of K9 glass material with a refractive index n = 1.517. The incident angle of the incident light beam on the surface of the TIR prism 22 is greater than the critical angle to cause total internal reflection, and the reflected light beam is transmitted through the prism after being modulated by the DMD chip 23.

[0053] In one embodiment, the vertical magnification of the projection objective lens 21 is the ratio of the size of the electromagnetic surface to the size of the projection chip. When the projection distance is 0.25M, the size of the electromagnetic surface is 20 inches (50cm × 50cm), and a 0.7-inch DMD chip is selected, the vertical magnification β = 20 / 0.7 = 29. According to the lens focal length calculation formula Substituting the image distance, that is, the distance l' between the projection objective lens and the electromagnetic surface is 0.25M, we can get f = 9mm.

[0054] In one embodiment, the material of the total reflection prism 22 is K9 glass (refractive index n = 1.517), and the included angle α between the prism and the DMD chip 23 is 33.4°. Considering the absorbing cavity space and the ease of assembly and alignment, the prism structure adopted is that the incident beam incident angle is greater than the critical angle, total reflection occurs on the prism surface, the reflected beam is incident on the prism surface again after being modulated by the DMD, and since the incident angle is less than the critical angle, the beam transmits through the prism.

[0055] In one embodiment, the DMD chip 23 is a 2048×1080 pixel array, the micromirror flipping speed is at the 10 μs level, the pattern refresh rate > 5 kHz, and combined with the sub-millisecond light response characteristics of the photoconductive material thin film, the overall system response time ≤ 200 μs.

[0056] In one embodiment, the transmission efficiency of the electromagnetic window > 90%.

[0057] In one embodiment, the cavity depth is 50 cm, the bottom area is the same as the electromagnetic surface size, and the inner wall of the cavity is coated with an absorbing material with a reflectivity < 0.1%.

[0058] The specific working process of an ultra-wide octave tunable electromagnetic window based on photoconductive materials in the present invention is as follows:

[0059] 1. Determine the required working frequency band and the corresponding electromagnetic surface pattern

[0060] According to the actual application requirements, use electromagnetic simulation software (such as CST, HFSS) to optimize the unit size and spacing, and determine the required working frequency band and the corresponding electromagnetic surface pattern, as Figure 2 shown. When designing the electromagnetic surface pattern, parameters such as the target, direction, and gain of beam control need to be considered to achieve the required electromagnetic characteristics. Based on the frequency band - wavelength mapping formula and the frequency response model: the free space wavelength λ0 corresponding to the working frequency f = c / f (c is the speed of light). It should be noted during design that the period P of the metasurface unit needs to satisfy P < λ0 / 2 to avoid high-order diffraction effects.

[0061] For example, when performing beam control in the low frequency band (< 10 GHz), square patches (such as Figure 3 , 4 shown), circular patches (such as Figure 5 , 6 shown) or cross-shaped structures (size a ≈ λ0 / 3a ≈ λ0 / 3) can be used; when performing beam control in the high frequency band (20 GHz), the array form can adopt a fractal structure or a sub-wavelength hole array to improve the equivalent inductance and capacitance.

[0062] 2. Digital signal processing and DMD input

[0063] Convert the pattern of the electromagnetic surface 1 into a digital signal and perform appropriate digital signal processing, such as filtering, amplification, and modulation. The processed digital signal is input into the DMD chip 23 in the DLP projection system for pattern projection preparation.

[0064] 3. The DLP projection system projects the pattern

[0065] The DLP projection system 2 illuminates the DMD chip 23 with a 780-nm laser light source and projects the pattern on the DMD chip 23 onto the photoconductive material thin film 12 through an optical system. During the projection process, the intensity and stability of the light source are ensured by controlling the DMD chip 23 to guarantee the clarity and accuracy of the pattern. At the same time, by adjusting the flipping state of the DMD chip 23, dynamic adjustment and control of the pattern can be achieved.

[0066] The specific adjustment process is as follows: Convert each electromagnetic surface structure image into a set of digital signals consisting of 0 / 1 codes. The control circuit receives this set of digital signals from a computer or other device, and these signals determine the state of each micromirror. When the digital signals are written into the SRAM, the electrostatically activated addressing electrodes, the mirror, and the armature are prompted to rotate the hinge device, and the mirror tilts by 12°, thus changing the reflection direction of the incident light. Each micromirror will rotate to one of two positions: on (+12°) or off (-12°). By controlling the on and off of each micromirror, the DMD chip modulates the passing light, thereby forming an electromagnetic surface array on the screen. The key lies in that through reasonable code and logic design, after the required array is formed, each micromirror maintains its angle unchanged, and the required array image is stably projected onto the organic photoconductor surface to maintain the stable performance of the electromagnetic surface. When it is necessary to switch to other electromagnetic surface array forms, re-enter the 0 / 1 codes of the new electromagnetic surface array image. At this time, after the micromirrors are reset, repeat the above working process to project a new array image again, and quickly realize the reconstruction of the electromagnetic surface.

[0067] 4. Electromagnetic surface beam steering

[0068] After the pattern is projected onto the electromagnetic surface 1 based on the photoconductive material, unit patterns and matrix patterns with different shapes and sizes as shown in Figure 2 are formed, that is, the corresponding electromagnetic surface structure is formed to achieve effective wave transmission or filtering of electromagnetic waves within an ultra-wide frequency band. When the projection unit structure is as shown in Figure 3 , by changing the unit size, the movement of the bandpass frequency point within the octave range from 2 GHz to 16 GHz as shown in Figure 4 can be achieved; when the projection unit structure is as shown in Figure 5 , by changing the unit size, the movement of the bandstop frequency point within the octave range from 2 GHz to 16 GHz as shown in Figure 6 can be achieved. By changing the projection pattern and switching to use Figure 2The electromagnetic surface unit structures of different sizes and shapes such as square rings and circular rings are used on the Chinese side, and the arrangement and combination methods are flexibly changed to achieve the control of electromagnetic wave transmission within an ultra-wide octave range; the transmission and filtering states are switched by instantaneously changing the patch type and slot type of the projection pattern.

[0069] In summary, the ultra-wide octave tunable electromagnetic window based on photoconductive materials provided by the present invention can adapt to different environments and requirements, reduce external interference, improve the detection ability and accuracy of radar, and has the advantages of a wide tunable bandwidth range, fast response speed, flexible design, and low processing cost. This electromagnetic window can also be used in the design of intelligent reflecting surfaces. By projecting the electromagnetic surface unit pattern through a DLP projection system, an electromagnetic surface with different reflection frequency bands is formed to achieve the ultra-wide octave dynamic control of electromagnetic waves, providing new solutions for fields such as wireless communication and electromagnetic stealth.

[0070] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. An ultra-large octave-band adjustable electromagnetic window based on photoconductive materials, characterized in that: It includes a cavity with an opening at the top and an electromagnetic surface encapsulated at the opening end, wherein a light driving module is arranged in the cavity; the light driving module projects different patterns on the electromagnetic surface, and switches the bandpass / bandstop working mode by optically controlling the equivalent surface impedance; The electromagnetic surface comprises a dielectric plate and a photoconductive material film coated on the dielectric plate; The optical driving module is capable of projecting a preset light pattern on the electromagnetic surface, thereby changing the equivalent impedance distribution of the electromagnetic surface; The cavity is used to support the electromagnetic surface and absorb the reflected light of the photoconductive material film.

2. According to claim 1, a super-large octave-band adjustable electromagnetic window based on photoconductive materials, characterized in that: The dielectric plate is made of FR4 epoxy resin material; the photoconductive material film is a polyimide / copper phthalocyanine composite film with a thickness of 20 μm.

3. According to claim 2, a super-large octave-band adjustable electromagnetic window based on photoconductive materials, characterized in that: The resistivity of the photoconductive material film in the illuminated area changes from 10 8 Ω·cm drops to 10 in the photoconductive state 3 Ω·cm, and the equivalent impedance of the electromagnetic surface is regulated by the dynamic pattern of the optical driving module to achieve reconfigurable control of the electromagnetic wave transmission characteristics in the 1-40GHz frequency band.

4. According to claim 1, a super-large octave-band adjustable electromagnetic window based on photoconductive materials, characterized in that: The optical drive module is a DLP projection system, which includes a 780nm laser, an illumination lens group, a total reflection prism, a DMD chip, and a projection objective lens arranged in sequence along the optical path, and is used to project dynamic patterns on a photoconductive material film.

5. The ultra-large octave-band adjustable electromagnetic window based on photoconductive materials according to claim 4, characterized in that: The DLP projection system adopts a telecentric optical path structure, and the illumination lens group includes a laser beam expansion system and an 8×8 compound eye lens array; the input mirror focal length of the laser beam expansion system is -3.1 mm, and the output mirror focal length is 3.1 mm; the compound eye lens unit size is 2.5 mm×1.88 mm.

6. The ultra-large octave-band adjustable electromagnetic window based on photoconductive materials according to claim 5, characterized in that: The working wavelength of the projection objective lens is 780 nm, the full field angle 2ω=70°, and the aperture ratio F / # of the DMD chip is 2.

4.

7. The ultra-large octave-band adjustable electromagnetic window based on photoconductive materials according to claim 6, characterized in that: The total reflection prism is made of K9 glass with a refractive index of n=1.

517. The incident angle of the incident light beam on the prism surface is greater than the critical angle to cause total reflection. The reflected light beam is modulated by the DMD chip and then transmitted out of the prism.

8. The ultra-large octave frequency-band adjustable electromagnetic window based on photoconductive materials according to claim 7, characterized in that: The DMD chip has a 2048×1080 pixel array, a micromirror flipping speed of 10μs, a pattern refresh rate of >5kHz, and combined with the sub-millisecond light response characteristics of the photoconductive material film, the overall response time of the system is ≤200μs.

9. The ultra-large octave frequency-band adjustable electromagnetic window based on photoconductive materials according to claim 1, characterized in that: The transmission efficiency of the electromagnetic window is >90%.

10. The ultra-large octave-band adjustable electromagnetic window based on photoconductive materials according to claim 1, characterized in that: The cavity has a depth of 50 cm, a bottom area consistent with the size of the electromagnetic surface, and an inner wall of the cavity is coated with a light-absorbing material with a reflectivity of <0.1%.

Images