Longwave infrared (LWIR) optics are essential for several technologies, such as thermal imaging and wireless communication, but their development is hindered by their bulk and high fabrication costs. Metasurfaces have recently emerged as powerful platforms for LWIR integrated optics; however, conventional metasurfaces are highly chromatic, which adversely affects their performance in broadband applications. In this work, the chromatic dispersion properties of metasurfaces are analyzed via ray tracing, and a general method for correcting chromatic aberrations of metasurfaces is presented. By combining the dynamic and geometric phases, the desired group delay and phase profiles are imparted to the metasurfaces simultaneously, resulting in good achromatic performance. Two broadband achromatic metasurfaces based on all-germanium platforms are demonstrated in the LWIR: a broadband achromatic metalens with a numerical aperture of 0.32, an average intensity efficiency of 31%, and a Strehl ratio above 0.8 from 9.6 μm to 11.6 μm, and a broadband achromatic metasurface grating with a constant deflection angle of 30° from 9.6 μm to 11.6 μm. Compared with state-of-the-art chromatic-aberration-restricted LWIR metasurfaces, this work represents a substantial advance and brings the field a step closer to practical applications.

A bandpass filter integrated metalens based on electromagnetically induced transparency (EIT) for long-wavelength infrared (LWIR) imaging is designed in this paper. The bandwidth of the metalens, which is a diffractive optical element, decreases significantly with the increase of the aperture size to a fixed f-number, which leads to the decline of imaging performance. The same material composition and preparation process of the metalens and the EIT metasurface in the long-wavelength infrared make it feasible that the abilities of focusing imaging and filtering are integrated into a metasurface device. With the purpose of validating the feasibility of this design method, we have designed a 300-μm-diameter integrated metalens whose f-number is 0.8 and the simulation was carried out. The introduction of EIT metasurface does not affect the focusing near the diffraction limit at the target wavelength, and greatly reduces the influence of stray light caused by non-target wavelength incident light. This bandpass filter integrated metalens design method may have a great potential in the field of LWIR compact optical systems.

This paper reports the design and electromagnetic performance of a new complementary frequency selective surface (CFSS) which shows polarization selectivity and good angular stability. Each CFSS unit cell only consists of a thin substrate sandwiched by a square patch array and its complementary square slot array with lateral displacement. The polarization selectivity of the proposed CFSS is determined by the displacement introduced between two arrays. An equivalent circuit model has been developed for this structure to interpret its polarization selective feature. The CFSS structure has been analyzed with full-wave simulation. The polarization selectivity of the proposed structure was verified by experiment.

In order to meet the requirements for multiband communication, a dual-band passband frequency selective surface (FSS) with low-profile and high selectivity at its higher passband is proposed in this paper. The proposed FSS is a three-layer structure. An arc-cross patch (ACP) and four quarter-circular patches (QCP) are introduced on the outer layers to produce two transmission nulls of the higher passband, which result in high selectivity of higher passband. The inductively complementary structure on the middle layer is introduced to manipulate the coupling between layers which contribute to the low-profile and angular stability. The segmental study method is used to establish the equivalent circuit model (ECM) and analyze its mechanism. The proposed dual-band FSS, whose high selectivity was verified by experiment, is low-profile and shows good polarization insensitivity and angular stability. A feasible FSS design solution is provided for dual-band communication.

This paper presents a three-medium, double-layer Frequency Selective Surface (FSS) structure that exhibits stable filtering characteristics, including stability with respect to incident angle and stability of filtering performance under misalignment conditions. The resonant frequency remains unchanged even when the elements are misaligned. The Radar Cross Section (RCS) of this structure has been tested, and the results indicate high transmittance within the passband and an RCS reduction of up to 20 dB outside the passband. These features render the structure highly significant for applications in conformal radome designs.

A₂BB′X₆ double perovskites offer broad compositional flexibility, requiring screening strategies that jointly consider electronic properties and thermodynamic stability. We developed a leakage-controlled machine learning workflow integrating canonical-formula grouping, robustness tests, descriptor-cost analysis, and prediction uncertainty. The dataset contains 1975 Materials Project entries represented by 398 descriptors. Extra Trees predicted band gaps with a held-out MAE of 0.2031 eV and R² of 0.9437, whereas histogram gradient boosting predicted energy above the hull with an MAE of 0.02122 eV atom⁻¹ and R² of 0.8601. The stability classifier achieved ROC-AUC, PR-AUC, and MCC values of 0.9603, 0.9632, and 0.8192, respectively. Removing 39 relaxed-structure descriptors increased hull-energy MAE by approximately 12.5%, supporting a two-stage workflow of composition-based triage followed by structure-informed refinement. Chemical-distribution-shift tests revealed substantial performance degradation and defined the applicability domain. Seventeen held-out compounds met the screening criteria, representing retrospective recovery rather than prospective discovery. Path-specific phonon calculations for one Tier-1 candidate and two representative Tier-2 fluorides showed no imaginary modes along L–Γ–X–W, but cannot establish full-zone dynamical stability. Their HSE06+SOC gaps of 2.148–2.919 eV exceeded the original 1.0–2.0 eV window, underscoring the need for multi-fidelity validation. Overall, the workflow provides a reproducible and well-defined strategy for prioritizing and validating double perovskites.