In this work, we propose and analyze a thermally tunable metasurface based on indium antimonide (InSb), designed to operate in the terahertz (THz) frequency range. The metasurface exhibits dual functionalities: single-band perfect absorption and efficient polarization conversion, enabled by the temperature-dependent permittivity of InSb. At approximately 280 K, InSb transitions into a metallic state, enabling the metasurface to achieve near-unity absorptance (100%) at 0.408 THz under normal incidence, independent of polarization. Conversely, when InSb behaves as a dielectric at 200 K, the metasurface operates as an efficient polarization converter. By exploiting structural anisotropy, it achieves a polarization conversion ratio exceeding 85% over the frequency range from 0.56 to 0.93 THz, while maintaining stable performance for incident angles up to 45°. Parametric analyses show that the resonance frequency and absorption intensity can be effectively tuned by varying the InSb square size and the silica (SiO₂) layer thickness, achieving maximum absorptance at a SiO₂ thickness of 16 μm. The proposed tunable metasurface offers significant potential for applications in THz sensing, imaging, filtering, and wavefront engineering.

El artículo presenta un prototipo diseñado para la enseñanza superior, este prototipo es un espectrofotómetro modular, el cual consta de tres módulos, el primer módulo es la fuente de luz, el segundo módulo es el portacubetas en el cual ocurren las transiciones electrónicas y en el tercer módulo las transiciones electrónicas que ocurren en el segundo módulo se convierten en datos numéricos. Este prototipo tiene la ventaja de ser móvil, no sé descalibra, debido a que utiliza un juego de diodos emisores de luz (LEDs) como fuente de luz. Este prototipo mide impedancias de una fotorresistencia, la cual es afectada por las transiciones electrónicas ocurridas en el segundo módulo. Este prototipo de espectrofotómetro modular nos permite utilizarlo para la química analítica correlacionando las concentraciones de una muestra con la impedancia de la fotorresistencia, la cual se mide con un multímetro. Este prototipo presenta coeficientes de determinación de 0.9993, 0.9990, 0.9989 y 0.9961, respectivamente para soluciones de sulfato de cobre, permanganato de potasio, pigmento amarillo huevo y colágeno, estas mediciones nos permiten aplicar la ley de Lambert-Beer para la espectrofotometría. Palabras clave: Espectroscopia Visible; Espectrofotómetro modular; Química analítica; Fotoquímica; ley de Lambert-Beer. Prototype of a modular spectrophotometer for chemistry education Abstract: The article presents a prototype designed for higher education, this prototype is a modular spectrophotometer, which consists of three modules, the first module is the light source, the second module is the cuvette holder in which the electronic transitions occur and in the third module the electronic transitions that occur in the second module are converted into numerical data. This prototype has the advantage of being mobile, it does not become out of calibration, because it uses a set of light emitting diodes (LEDs) as a light source. This prototype measures impedances of a photoresistor, which is affected by the electronic transitions occurring in the second module. This modular spectrophotometer prototype allows us to use it for analytical chemistry by correlating the concentrations of a sample with the impedance of the photoresistor, which is measured with a multimeter. This prototype presents determination coefficients of 0.9993, 0.9990, 0.9989 and 0.9961, respectively for solutions of copper sulfate, potassium permanganate, egg yellow pigment and collagen, these measurements allow us to apply Lambert-Beer law for spectrophotometry. Keywords: Visible spectroscopy; Modular spectrophotometer; Analytical chemistry; Photochemistry; Lambert-Beer law.

Perfect absorbers operating in the terahertz (THz) band are key enablers for next-generation wireless systems. However, conventional metal–dielectric designs suffer from Ohmic losses and limited reconfigurability. Here, we propose an all-dielectric indium antimonide (InSb) cylindrical pillar metasurface that achieves near-unity absorption at $f_0=1.83$ THz with a high quality factor of $Q=72.3$. Critical coupling between coexisting electric and magnetic dipoles enables perfect impedance matching, while InSb’s low damping minimizes energy loss. The resonance is tunable via temperature and magnetic bias at sensitivities of $S_T\approx 2.8\mathrm{GHz}·{\mathrm{K}}^{-1}$, $S_B^{\mathrm{TE}}\approx -132.7\mathrm{GHz}·{\mathrm{T}}^{-1}$, and $S_B^{\mathrm{TM}}\approx -34.7\mathrm{GHz}·{\mathrm{T}}^{-1}$, respectively, without compromising absorption strength. At zero magnetic bias ($B=0$), the metasurface is polarization-independent under normal incidence; under magnetic bias ($B\ne 0$), it maintains near-unity absorbance for both TE and TM, while the resonance frequency becomes polarization-dependent. Additionally, the 90% absorptance bandwidth ($\Delta f_{A\ge 0.9}$) can be modulated from 8.3 GHz to 3.3 GHz with temperature, or broadened from 8.5 GHz to 14.8 GHz under magnetic bias. This allows gapless suppression of up to 14 consecutive 1 GHz-spaced channels. This standards-agnostic bandwidth metric illustrates dynamic spectral filtering for future THz links and beyond-5G/6G research. Owing to its sharp selectivity, dual-mode tunability, and metal-free construction, the proposed absorber offers a compact and reconfigurable platform for advanced THz filtering applications.

Les défauts d’arc dans les systèmes électriques représentent un risque majeur pour la sécurité et nécessitent des méthodes de détection fiables. Alors que les techniques traditionnelles reposent sur l’analyse du courant, cette étude explore l’utilisation de la radiation électromagnétique émise lors des défauts d’arc pour leur détection. Une antenne fractale de Hilbert de quatrième ordre (HCFA) a été conçue, fabriquée et testée afin de capter les émissions électromagnétiques à large bande générées par les décharges d’arc. Les résultats expérimentaux révèlent une forte corrélation entre les variations brusques de tension et la radiation électromagnétique émise. L’analyse fréquentielle montre que le spectre de radiation est principalement concentré dans les bandes 22–44 MHz et 50–68 MHz. De plus, l’analyse par transformation de Fourier à court terme (STFT) met en évidence les caractéristiques temps-fréquence du rayonnement d’arc, permettant d’identifier précisément son initiation, sa durée et son extinction. Ces résultats confirment la faisabilité de la détection des arcs par radiation électromagnétique et ouvrent la voie au développement de systèmes de surveillance en temps réel basés sur des antennes pour les environnements électriques complexes.