Terahertz (THz) meta-devices are considered to be a promising framework for constructing integrated photonic circuitry, which is significant for processing the upsurge of data brought about by next-generation telecommunications. However, present active metasurfaces are typically restricted by a single external driving field, a single modulated frequency, fixed switching speed, and deficiency in logical operation functions which prevents devices from further practical applications. Here, to overcome these limitations, we propose a hybrid THz metasurface consisting of vanadium dioxide (VO₂) and germanium (Ge) that enables electrical and optical tuning methods individually or simultaneously and theoretically investigate its performance. Each of the two materials is arranged in the meta-atom to dominate the resonance strength of toroidal or magnetic dipoles. Controlled by either or both of the external excitations, the device can switch on or off at four different frequencies, possessing two temporal degrees of freedom in terms of manipulation when considering the nonvolatility of VO₂ and ultrafast photogenerated carriers of Ge. Furthermore, the “AND” and “OR” logic operations are respectively achieved at two adjacent frequency bands by weighing normalized transmission amplitude. This work may provide an auspicious paradigm of THz components, such as dynamic filters, multiband switches, and logical modulators, potentially promoting the design and implementation of multifunctional electro-optical devices in future THz computing and communication.

Electromagnetic rail launch technology has made impressive progress; however, the analytical method of calculating the inductance gradient for a complex electromagnetic launcher is still insufficient. By fully considering the characteristics of electromagnetics and current distribution in a device, this paper describes a model of the current skin effect by simplifying the line current distribution in the device. Based on Biot–Savart Law, an analytical method of calculating inductance gradient for an electromagnetic rail launcher with complex structure is proposed. This method has the advantages of fast calculation speed and accurate calculation results. Because of error analysis, the calculated value relatively corresponds to the simulation result of the eddy current field. To reflect the transient electromagnetic emission process, the effects of different configurations, current frequency, and armature position on the inductance gradient are further summarized. The results show that the error rate of this method in calculating the inductance gradient is about 4%, which meets the requirement for calculation accuracy. The inductance gradient of the enhanced four-rail electromagnetic launcher is about 2.22 times that of the nonenhanced one due to the equal conditions; the inductance gradient decreases with the increase in current frequency and decreases as the armature approaches the muzzle.

This article presents a dual circular polarization (CP) microstrip antenna, emitting electromagnetic waves above and below the substrate, which is fed by the double L-probe. Selecting the L-probe feed increases the bandwidth of the antenna, and different probes control the rotation of CP. The antenna could radiate two polarized waves of the same amplitude and vertical through two square radiation patches; meanwhile, adjusting the phase difference between both waves to 90° will produce a CP wave in the far-field. The simulation and measurement results show that the antenna is in 4.3–4.8 GHz band with S11<−10 dB, S22<−10 dB, and AR<3 dB. Furthermore, a lower axis ratio could be obtained in this work compared with similar antennas of the same type.

Metasurfaces enable spatially programmable control of far-field wavefronts, while broadband molecular sensing relies on strong near-field confinement and enhanced light–matter interaction. The mismatch between far-field radiation and near-field localization makes their monolithic integration in a single shared aperture challenging. Here, we report an electrically tunable terahertz (THz) VO₂-based metasurface designed under temporal coupled mode theory (TCMT). The device adopts a metal–insulator–metal (MIM) architecture integrating a VO₂ microbridge and bowtie antenna, enabling bias-controlled switching between molecular fingerprint sensing and programmable wavefront manipulation in a shared aperture. At zero bias, the metasurface operates in an over-coupled regime, supporting a broadband low Q resonance over 0.8–1.2 THz with strong local field enhancement for molecular fingerprint sensing demonstration, serving as a passive near-field sensing mode. Under the metallic state condition induced by the VO₂ phase transition, the unit cell exhibits an approximately 180° reflection phase shift with nearly invariant amplitude. An electrically assisted programmable addressing implementation is proposed by exploiting the electrothermal switching capability of VO₂. Each unit cell thus functions as a 1-bit programmable meta-atom. By reconfiguring the spatial coding sequence, the device realizes anomalous reflection and beam splitting, which are further extended to refractive index sensing: thin analyte layers (<10 μm) are detected via anomalous reflection, whereas thicker layers are detected via beam splitting when the anomalous beam is suppressed. This constitutes a far-field active sensing mode. Both functionalities originate from the same over-coupled radiative loss mechanism: enhanced near fields enable fingerprint sensing, while the open radiative channel supports far-field refractive index sensing through programmed phase coding. This shared aperture design unifies near-field and far-field, passive and active sensing, offering a compact platform for THz integrated sensing and communication.

Quasi-bound states in the continuum (q-BICs) provide an effective approach for achieving strongly confined resonances in metasurfaces. However, the simultaneous realization of high-Q, polarization-multiplexed, and tunable resonances at a single frequency using a single resonant meta-atom remains challenging. Here, we numerically design and investigate a tunable all-dielectric terahertz (THz) metasurface consisting of a single asymmetric germanium (Ge) resonator by employing COMSOL Multiphysics. By introducing only one asymmetry parameter, the symmetry-protected BIC is transformed into a radiative q-BIC under two orthogonal linear polarizations. Through the coupling between the q-BIC and the intrinsic resonant mode, distinct interference responses are generated. Specifically, at the same frequency of 1.227 THz, a Fano resonance (Q = 606) is obtained under TE polarization, whereas an electromagnetically induced transparency (EIT)-like resonance (Q = 1105) appears under TM polarization. Owing to the tunable property of Ge, the two resonances can be actively modulated, achieving modulation depths of 96.7% and 99.1%, respectively. Furthermore, under TM polarization, the group delay can be continuously tuned from 0 to 259 ps by controlling the Ge conductivity. The proposed metasurface provides a compact platform for polarization-multiplexed and dynamically tunable THz photonic devices.