In response to multispectral detection threats and functional conflicts or complex structures in existing stealth materials, this paper proposes a flexible multiband stealth metasurface compatible with visible-laser-infrared (IR)microwave spectra. The "three functional layers" architecture-optical camouflage layer (OCL), IR functional layer (IRFL), and microwave functional layer (MFL)-achieves multiband stealth via layered design and process optimization. OCL uses SiO2/ZnS film interference to match visible light colors. IRFL employs an asymmetric Fabry-P & eacute;rot structure based on ultrathin Ag tunneling and surface plasmon polaritons, achieving more than 90% absorption of 1.06 mu m laser and maintaining emissivity below 10% at 2-14 mu m. MFL forms a frequency selective surface by etching OCL and IRFL to enable the transmission of 2-14 GHz electromagnetic waves. Combined with the underlying indium-tin-oxide wave-absorbing structure, it achieves 90% absorption in the X-band. The overall structure, with a thickness of less than 5 mm, exhibits a certain degree of flexibility and visible transparency, adopting mature processes such as electron beam evaporation and laser etching, which are low-cost and suitable for mass production. The designed metasurface realizes multiband stealth with a simple structure, high functional integration, and easy engineering implementation, demonstrating broad application potential in multiband compatible stealth fields. (c) 2026 Chinese Laser Press

Metasurfaces or artificial electromagnetic structures offer viable solutions for electromagnetic (EM) wave manipulation with their compact periodic configurations. Tunable metasurfaces capable of controlling wavefronts are highly desirable in numerous engineering and scientific applications. This paper presents the design and implementation of a reconfigurable electromagnetic metasurface based on circular dichroism (CD), which integrates PIN diodes to achieve dynamic manipulation of circularly polarized (CP) waves and enables vortex beam generation under corresponding states. The metasurface consists of a 30 × 30 array of meta-atoms, each independently controllable. By switching the diode states, each meta-atom switch between functioning as a high-efficiency reflector, high-efficiency absorber, left-handed circular polarization (LHCP) metamirror, and right-handed circular polarization (RHCP) metamirror. Leveraging the Pancharatnam-Berry (PB) phase principle, chiral mirror elements are arranged in arrays to generate vortex beams. Through simulations and experimental verification, the metasurface achieves multi-modal generation by simultaneously generating vortex beams with topological charges l =  + 1 and l = -1, enables selective generation of orbital angular momentum (OAM) modes to produce vortex beams carrying either l =  + 1 or l = -1 topological charge, and demonstrates efficient absorption of CP beams under specific operational conditions. The device demonstrates superior performance in the 8.5-13.5 GHz frequency range, providing innovative technical approaches for optics, communications, quantum technologies, biomedicine, and other fields. It is expected to enhance information transmission efficiency, strengthen optical manipulation capabilities, and drive the realization of more cutting-edge applications.

Metamaterials provide amazing opportunities for developing frequency selective radiation because of their unique electromagnetic resonance properties. However most frequency-selective thermal radiation metamaterials currently do not have an optical transparency property, which prevents them from being used in some special occasions. Here, an optically transparent frequency-selective thermal radiator is designed and fabricated using the metallic-like properties of ITO. The emissivity of the metamaterial in the atmospheric transparent windows (3.0-5.0 mu m and 8.0-14.0 mu m) is less than 0.1, while the emissivity outside the windows (5.5-7.6 mu m) is very high, thus achieving strong thermal radiation efficiency. Finally, the thermal radiation power of frequencyselective thermal radiator, low-emissivity coatings, and black body was analyzed using the thermal radiation model. Compared to traditional low-emissivity coatings, the advantage of frequency-selective thermal radiators is that it provides an efficient thermal radiation window for the target, further enhancing its infrared stealth capability through radiative cooling.

With the rapid development of detection technology and artificial intelligence, the widespread use of multispectral detectors has increased challenges to stealth capabilities. This paper presents a bispectral camouflage metasurface with microwave diffuse emission and tunable infrared (IR) emissivity, achieving an integrated design for radar cross-section (RCS) reduction and tunable IR emissivity. The structure consists of layers from bottom to top: aerogel felt, indium-tin-oxide (ITO), air, polyethylene terephthalate (PET), and ITO. It reduces RCS through microwave diffuse reflection and adjusts IR emissivity by controlling the ITO fill ratio. Both simulations and experiments demonstrate effective suppression of electromagnetic (EM) wave backscattering within 4.5–10.3 GHz, achieving radar invisibility. The tunable IR emissivity ranges from 0.2 to 0.7 with good thermal insulation. This design alleviates issues related to structural thickness and processing complexity and avoids increased thermal load from microwave absorption, offering better tunable IR emissivity for various thermal camouflage environments. This metasurface holds significant promise for multispectral stealth and IR camouflage applications.

Objective Accurately determining the optical constants (refractive index n and extinction coefficient k) of transparent solid materials is a crucial issue in optical design. The dual thickness transmittance method offers a straightforward approach that does not require the Kramers-Kronig relationship. For weakly absorbing materials, high-precision measurement results can be obtained by changing the thickness. The double thickness transmittance method establishes nonlinear equations about optical constants by measuring the transmittance of materials with two different thicknesses. Due to the complexity of the equations, it is difficult to obtain analytical solutions, and inversion methods are often used to solve optical constants. These inversion methods present challenges including computational time requirements, iterative errors, and multiple potential values for refractive index results. While researchers have attempted to address these issues through faster iterative algorithms or combinations with methods such as ellipsometry, the outcomes remain suboptimal. Methods Recent research has employed transmittance spectra of stacked samples combined with inversion methods to determine material optical constants, though the inherent limitations of inversion methods persist. An alternative approach utilizing dual spectral analysis for determining optical constants based on transmittance and reflectance spectra of single-layer samples has been proposed. However, this method faces challenges due to inconsistent experimental conditions between transmittance and reflectance measurements. The present study integrates the advantages of both stacked sample transmittance spectrum inversion and single-layer sample dual spectrum analysis methods. The approach involves measuring transmittance of various stacked sample combinations and deriving single-layer sample reflectance through algebraic operations. This enables optical constant determination without direct reflectance measurement while avoiding inversion method limitations. This analytical method based on stacked sample transmittance spectra significantly streamlines experimental measurement and calculation processes. For demonstration, transmittance measurements of Zinc Selenide samples under various stacking combinations were conducted using a Fourier transform infrared spectrometer in the 2-18 mu m infrared band. The optical constants were determined using this novel method, followed by error analysis of extinction coefficient and refractive index measurements. Finally, the factors affecting the accuracy of optical constant measurement were studied by combining experiments and numerical simulations. Results and Discussions The optical constants of Zinc Selenide were measured using an application example. The relative uncertainty of the extinction coefficient k was less than 10% in the ranges of 3.5-5.5, 7.0-8.5, and 14-18 mu m, and less than 5% in the range of 15.0-17.5 mu m (Figs. 4 and 5). The relative uncertainty of refractive index n is less than 0.5% in the range of 3 -15 mu m, and less than 0.25% in the range of 7 -12 mu m (Figs. 6 and 7). Comparatively speaking, the measurement accuracy of refractive index is higher, and the extinction coefficient and its errors have almost no effect on the refractive index and its measurement accuracy. The main source of error for both is the measurement error of sample transmittance. The influence of sample thickness on the transmittance of stacked samples was studied through numerical simulation, and it was pointed out that sample thickness is crucial for reducing measurement errors in transmittance (Figs. 10 and 11). The new method proposes requirements for the transmittance t and thickness L of single-layer samples: under the condition of a spectrometer transmittance accuracy of 0.001, the transmittance t of single-layer sample should be greater than 0.004 and less than 0.953; adjusting the sample thickness L to ensure that the transmittance of the stacked sample falls as close as possible to the middle position between t(2 )and t/(2-t), will help improve the measurement accuracy of transmittance and achieve accurate determination of optical constants. Conclusions This study combines the advantages of the stacked sample transmittance spectrum inversion method and the single-layer sample dual spectrum analysis method, and proposes an analytical model based on the stacked sample transmittance spectrum. It realizes the use of the single-layer sample dual spectrum analysis method to determine optical constants without measuring reflectance, while avoiding the disadvantages of inversion methods and greatly simplifying the experimental measurement and solution calculation process. The application example uses transmittance of Zinc Selenide stacked samples to demonstrate the specific use of the new method, and the results show that the method is feasible. Numerical simulation was conducted to study the influence of sample thickness on the transmittance of stacked samples. Adjusting the sample thickness reasonably to make the transmittance curve of stacked samples as close as possible to the middle position of its allowable range will help improve the measurement accuracy of transmittance and achieve accurate determination of optical constants. Our research results provide an alternative solution for the precise determination of the optical constants of transparent solids.

This paper investigates the connection between college physics courses and professional courses related to radio communication. First, it reviews the historical development of thermal noise research, clarifies the origin of the concept of noise temperature, and provides a general definition of noise temperature. Next, taking the antenna as an electromagnetic wave transducer, it derives the quantitative expression for the antenna thermal noise power spectral density by combining the theory of blackbody radiation with Kirchhoff's law of thermal radiation. Based on revealing the physical mechanism of antenna thermal noise, the paper elaborates on the logical construction and physical connotations of the concept of antenna noise temperature. Teaching practice has shown that integrating the above ideas into teaching deepens students' understanding of the relevant physical knowledge. This study aims to deepen students' understanding of the blackbody radiation theory in college physics courses and provide a reference for the teaching of radio communication professional courses. By extending the basic physical theory to the field of radio communication, it demonstrates the bridging role of basic physics courses in the curriculum system, which is conducive to cultivating students' interdisciplinary comprehensive literacy and innovative thinking abilities.

MXene is widely used in the fields of microwave absorption and electromagnetic shielding to balance electromagnetic pollution with the development of communication technologies and human health, due to its excellent surface functional groups and tunable electronic properties. Although pure multilayered MXene has an excellent accordion-like structure, the weak dielectric loss and lack of magnetic loss result in poor microwave absorption performance. Here, we propose a strategy for the catalytic growth of CNTs by the electrophoretic deposition of adsorbed metal ions, leading to the successful preparation of Ni-MWCNTs/Ti3C2Tx composites with a “layer-by-layer” structure, achieved through in situ regulated growth of CNTs. By introducing dielectric–magnetic synergy to improve the impedance matching conditions, and by regulating the diameter of the CNTs to alter the electromagnetic parameters of Ni-MWCNTs/Ti3C2Tx, the 2-Ni-MWCNTs/Ti3C2Tx composite achieves the best reflection loss (RL) value of −44.08 dB and an effective absorption bandwidth of 1.52 GHz at only 2.49 mm thickness. This unique layered structure and the regulation strategy provide new opportunities for the development of few-layered MXene composites.

Aiming at the requirements of multi-spectral transparency, electromagnetic (EM) shielding and radar stealth for window materials in visible-infrared (IR) integrated optoelectronic systems, this paper proposes a double-layer indium tin oxide (ITO) micro-nano structure metamaterial based on a ZnS substrate, which realizes the efficient coupling of "dual - spectral transparency - EM shielding - radar stealth". Through the periodic collaborative design of the bottom orthogonal grid network and the upper concentric square ring patches, while ensuring high transmittance in the visible light (380-780 nm) and IR (2-10 μm) bands, the EM shielding efficiency (SE) in the 100 MHz to 1 GHz frequency band is achieved to be more than 20 dB, and the absorption rate in the X-band (8-12 GHz) is more than 90%. Theoretical modeling and simulation reveal the composite action mechanism of "grid equivalent admittance shielding-resonant cavity energy dissipation", and magnetron sputtering and photolithography techniques are adopted to achieve millimeter-scale microstructure fabrication. Experimental results show that this metamaterial breaks through the balance limitations among light transmittance, SE, and radar stealth performance of traditional transparent shielding materials, providing an integrated solution for the protection of optoelectronic systems in complex EM environments.

It is a meaningful exercise that discussing the patterns of interference fringes in case introducing polarizers into the Young's double slit experiment while different combinations.H owever,"no fixed phase difference,"the commonly seen answer,does not fully understand the essence of the problem.By utilizing Malus's Law and the principle of wave superposition,this paper calculates the resulting contrast after superposition.Quantitative calculations dem-onstrate that when three polarizers are introduced in Young's double-slit interference experi-ment,the physical reason for the absence of interference fringes is the existence of a projection phase difference.Moreover,it is emphasized that in this context,the projection phase differ-ence is the determining factor for the presence or absence of interference fringes.The article provides a clear and intuitive physical image,suitable for classroom teaching,displaying the role of the projected phase difference and aiding students in gaining a deeper understanding and application of concepts related to light emission mechanisms,interference,polarization,and the interference of polarized light.

The liquid's optical constants (extinction coefficient and refractive index) can be determined by the spectral inversion method, among which the double-thickness transmission is most representative. Since the liquid itself cannot form a definite shape, it needs to be stored in a transparent container (liquid cell), so the spectral transmittance obtained through experimental measurement includes the influence of the optical constant of the liquid cell, which makes the spectral transmittance equation established based on the double-thickness transmission method extremely complex and difficult to obtain an analytical solution. Usually, the inversion method is used to calculate the optical constant of the liquid. The existing inversion methods have the following problems: first, the inversion iteration consumes time; second, the inversion iteration will introduce errors; and third, the liquid refractive index obtained by the inversion method has a binary problem. To solve the above problems, based on the three-layer medium structure (liquid cell), considering the multiple reflections of light on the interface of the two media, a set of spectral transmittance equations satisfying the integral ratio of liquid thickness is established. The polynomial equation related to the extinction coefficient is obtained through algebraic operation, and the extinction coefficient is calculated by solving and selecting the real number root greater than 0 and less than 1. In addition, the quadratic equation about the reflectance of the optical window of the liquid cell is solved. The reflectance of the interface between the liquid and the container is calculated with the root greater than 0 and less than 1, and two values of the liquid refractive index are obtained. Then, the liquid cell made of another material is used to measure the spectral transmittance of the liquid, and then combined with the extinction coefficient that has been obtained for related calculation, two other values of the liquid refractive index are obtained, and the refractive index of the liquid is the same one by selecting from the four values. As an application example, this paper selects the optical constant of water in the literature at 0.5 similar to 1.0 mu m as the "theoretical value", and the quartz and polymethyl methacrylate glasses with known optical constants are taken as the liquid cell materials. Without considering the instrument measurement error, the above literature data are substituted into the spectral transmittance equation, and the calculated transmittance is taken as "experimental data". Then, the optical constants of water are determined by finding the roots of polynomials, and the results are in full agreement with the "theoretical values". The simulation process and calculation results show that the new method is available and solves the problems of the inversion method such as time-consume, iteration error, and the binary of refractive index, and provides a new option for determining the optical constants of liquids

Metamaterials provide amazing opportunities for developing frequency selective radiation because of their unique electromagnetic resonance properties. However most frequency-selective thermal radiation metamaterials currently do not have an optical transparency property, which prevents them from being used in some special occasions. Here, an optically transparent frequency-selective thermal radiator is designed and fabricated using the metallic-like properties of ITO. The emissivity of the metamaterial in the atmospheric transparent windows (3.0-5.0μm and 8.0-14.0μm) is less than 0.1, while the emissivity outside the windows (5.5-7.6μm) is very high, thus achieving strong thermal radiation efficiency. Finally, the thermal radiation power of frequency-selective thermal radiator, low-emissivity coatings, and black body was analyzed using the thermal radiation model. Compared to traditional low-emissivity coatings, the advantage of frequency-selective thermal radiators is that it provides an efficient thermal radiation window for the target, further enhancing its infrared stealth capability through radiative cooling.

为解决光谱反演法确定透明固体光学常数的一些问题,如存在反演误差、计算耗时等.本文基于传统的双厚度透射率模型,建立了厚度满足整数比的两个光谱透射率方程.通过代数运算获得了与消光系数有关的多项式方程,求解并选择大于 0小于 1的实数根来计算消光系数;然后求解关于界面反射率的一元二次方程,选择大于 0小于 1的根来计算折射率.在确定光学常数的过程中,新方法没有反演误差、迭代计算耗时及多值问题.作为应用示例,利用已知文献中的双厚度透射率实验数据计算了CaF2和Si的光学常数,并和文献的结果进行了比较.结果表明,新方法优于传统的光谱反演法,新方法为透明固体光学常数的高精度确定提供了新选择.

A polarization-independent broadband infrared selective absorber/emitter (ISAE) based on multilaminar architecture is proposed and demonstrated. The salient features are that it has both low average emissivity of less than 0.1 in two atmospheric windows (3–5μm and 8–14μm) and otherwise high average emissivity of more than 0.8 in two non-atmospheric windows (2.5–3μm and 5–8μm), which renders it tailored infrared camouflage performance with thermal stability. Meanwhile, there is sharp narrowband absorption around at 10.6μm, which allows it to additionally possess laser camouflage performance. The comprehensive dependence of multispectral selective emissivity properties on the structural parameters, the polarization and incident angle of incoming excitation are analyzed and the underlying physical mechanisms are explored. It is found that the selective absorption/emissivity in band 5–8μm is originated from the fundamental mode plasmonic resonances, while that in 2.5–5μm is originated from the high-order hybrid mode plasmonic resonances therein. Meanwhile, there does exist a coupled competition effect between the hybrid modes in 2.5–3μm and in 3–5μm. All the results construct the basic guideline for designing these kinds of ISAE materials. Furthermore, we reexamine the physical essence of infrared camouflage based on multispectral bands selective emissivity with thermal management and establish an optimized generalized method for evaluating the camouflage performance of ISAE. The proposed ISAE proves to have much better infrared camouflage property throughout 2.5–14μm than the existing designs reported. The proof-of-principle ISAE is prepared and the selective emission spectrum is characterized, which is in good agreement with the simulations.

An optically transparent metamaterial structure with broadband microwave absorptivity is proposed. A specifically designed optically transparent metasurfaces was designed to control the microwave absorption though properly modifying the impedance and resonance peaks of the meta-atom. Within a wide incident angle of ±60o, the proposed structure displays high absorptivity greater than 90% in the region of 33.7-44.7GHz for TE polarization. For TM polarization, the absorptivity in the region of 11.8-37.2GHz is greater than 90%. The perfect consistency between experimental results and simulation results demonstrates that the proposal has practical application of multispectral stealth technology.

Based on the principle of electromagnetic wave cancellation, this paper proposes a coded metasurface which can suppress both radar backscattering and infrared radiation. Two high duty ratio superstructures with two different structures are designed and coded units are worked out on the basis of this. The experimental results indicate that the metasurface can effectively suppress the backscattering of electromagnetic waves in the 8.6–16.3 GHz band, and the average emissivity at infrared atmospheric window is 0.43. At the same time, it has good heat insulation performance, which can effectively suppress infrared radiation. In addition, the metasurface has light mass and flexibility. Therefore, the metasurface has a good prospect for application in the multispectral stealth field.

As a classic subpixel target detection algorithm in hyperspectral imagery, Orthogonal Subspace Projection (OSP) involves characterizing background subspace by using the most significant eigenvectors of the background covariance matrix. However, when the number of target pixels is high, the estimation of the background covariance matrix is easily contaminated by target information. Another problem with OSP is that the number of the most significant eigenvectors is usually determined by prior knowledge, whereas prior knowledge is rare in most detection scenarios. In order to solve these problems, a novel target detection algorithm is proposed, which first selects the pixel spectra dissimilar with the target signature to estimate the background covariance matrix, then chooses the eigenvectors corresponding to the first few larger eigenvalues to construct background endmember matrix, followed by the classic OSP algorithm to detect targets of interest. In order to demonstrate the utility of the proposed algorithm, two real Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) datasets are tested for target detection. The experimental results show that the algorithm yields much better detection performance than the classic OSP and the weighted sample covariance matrix-based OSP algorithm, and is more suitable for detecting targets occupying a number of pixels.

A visible-light-transparent metasurface has been designed to achieve infrared (IR)–radar stealth. An optically transparent material, indium tin oxide was chosen in preference to other low-IR-emissivity metals to achieve camouflage compatibility for the IR–radar stealth material. In addition, flexible polyethylene terephthalate was adopted as the dielectric material to in order to benefit from its visible light transparency; its softness could also improve its application prospects. The fabricated structure exhibited a strong absorptivity of over 90% from 8.265 GHz to 17.65 GHz and a low IR emissivity of less than 0.3 in the region of 3–14 μ m. The results demonstrated that the metasurface was polarization independent and it was still able to maintain 90% of its absorptivity with an oblique incidence of 20°. The good consistency between the experimental and simulated results verified that the proposed metasurface can be practically applied in multifunctional stealth technology.

In order to solve the problem of multiple reconstructed images in digital hologram, the lensless fourier transform hologram is taken as an example for comparative experiment. When the same experimental light path and recording conditions are used and the only variable is the sensitive element, the reconstructed image of CCD does not appear multiple images, while the reconstructed image of CMOS appears multiple images. In order to determine the reliability of the experiment, two correlated beams were imaged with the same optical path. The experimental phenomenon is still that there are multiple images in CMOS, but not in CCD. The working principle of CCD and CMOS in digital holography experiment is different.