Jiaming Hao

The long wavelength infrared (LWIR) range (8–14 µm) is crucial for thermal radiation detection, necessitating effective camouflage against advanced infrared technologies. Conventional camouflage approaches often rely on complicated photonic structures, facing significant implementation challenges. This study introduces a novel polarization‐insensitive and angle‐robust metacoating emitter for LWIR camouflage, inversely designed through a deep neural network (DNN) framework. The DNN framework facilitates the automatic optimization of the metacoating’s structural and material parameters. The resulting emitter achieves an average emissivity of 0.96 covering the LWIR range and a low emissivity of 0.25 in the other mid‐infrared (MIR) region. Enhanced electromagnetic wave localization and energy dissipation, driven by high‐lossy materials like bismuth and titanium, contribute to these properties. Infrared imaging confirms the emitter’s superior camouflage performance, maintain effectiveness at incident angle up to 70° while exhibiting strong polarization independence. This inverse‐designed metacoating demonstrates significant potential to advance infrared camouflage technology, providing robust countermeasures against modern, wide‐angle, and polarization‐sensitive detection systems.

The development of novel camouflage technologies is of great significance, exerting an impact on both fundamental science and diverse military and civilian applications. Effective camouflage aims to reduce the recognizability of an object, making it to effortlessly blend with the environment. For infrared camouflage, it necessitates precise control over surface emissivity and temperature to ensure that the target blends effectively with the surrounding infrared background. This study presents a semimetal–dielectric–metal metasurface emitter engineered for the application of infrared camouflage. The metasurface, with a total thickness of only 545 nm, consists of a Bi micro‐disk array and a continuous ZnS and Ti film beneath it. Unlike conventional metal‐based metasurface design, our approach leverages the unique optical properties of Bi, achieving an average emissivity of 0.91 in the 5–8 μm non‐atmospheric transparency window. Experimental results indicate that the metasurface emitter achieves lower radiation and actual temperatures compared to those observed in comparative experiments, highlighting its superior energy dissipation and thermal stability. The metasurface offers advantages such as structural simplicity, cost‐effectiveness, angular insensitivity, and deep‐subwavelength features, rendering it suitable for a range of applications including military camouflage and anti‐counterfeiting, with potential for broad deployment in infrared technologies.

Phase singularities (PSs) in topological darkness-based sensors have received significant attention in optical sensing due to their rapid, ultra-sensitive, and label-free detection capabilities. Here, we present both experimental and theoretical investigations of an ultrasensitive and multiplexed phase-sensitive sensor utilizing dual topological PSs in the visible and near-infrared regions. This sensor uses a simple structure, which consists of an ultra-thin highly absorbing film deposited on a metal substrate. We demonstrate the achievement of dual-polarization darkness points for s- and p-polarizations at different incident angles. Furthermore, we theoretically explain the double topological PSs accompanied by a perfect ±π-jump near a zero-reflection point, based on the temporal coupled-mode formalism. To validate its multifunctional capabilities, humidity sensing tests were carried out. The results demonstrate that the sensor has a detection limit reaching the level of 0.12 ‰. These findings go beyond the scope of conventional interference optical coatings and highlight the potential applications of this technology in gas sensing and biosensing domains.

In this study, we propose a strategy to construct high-performance ultra-thin optical power converters (OPCs) based on Gires–Tournois resonator configurations operating in high-order modes. Despite reducing the absorber thickness by 5.8 to 8.1 times, the proposed ultra-thin OPCs exhibit the same (comparable) energy absorption characteristic and demonstrate superior electrical performance compared to a thick OPC. It is revealed that such high absorption effects originated from the excitation of optical asymmetric Fabry–Perot-type high-order inference resonance modes and the electrical performance enhancement can be attributed to the reduction of the absorber thickness.

Camouflage is a common technique in nature, enabling organisms to protect themselves from predators. The development of novel camouflage technologies, not only in fundamental science, but also in the fields of military and civilian applications, is of great significance. In this study, we propose a new type of deep‐subwavelength four‐layered meta‐coating consisting of Si, Bi, Si, and Cr from top to bottom with total thickness of only ∼355 nm for visible‐infrared compatible camouflage. The visible color and the infrared emission properties of the meta‐coating can be independently adjusted. Colorful meta‐coating for visible camouflage can be obtained by changing the thickness of top Si layer, while the selective high emissivity in non‐atmospheric window for infrared camouflage remains. Due to the deep‐subwavelength properties, the meta‐coating shows high angle tolerance in both visible and infrared regions. The compatible camouflage capability of our proposed meta‐coating in the visible‐infrared region is validated under different environments. The deep‐subwavelength, angular insensitivity, visible‐infrared compatibility and large‐area fabrication feasibility promise the meta‐coating an effective solution for camouflage in various applications such as military weapons and anti‐counterfeiting.

Controlling the bandwidth and directionality of thermal emission is important for a broad range of applications, from imaging and sensing to energy harvesting. Here, we propose a new, to the best of our knowledge, type of long-wavelength infrared narrowband thermal emitter that is basically composed of aperiodic Tamm plasmon polariton structures. Compared to the thermal emitter based on periodic structures, more parameters need to be considered. An inverse design algorithm instead of traditional forward methodologies is employed to do the geometric parameter optimization. Both theoretical and experimental results show that the thermal emitter exhibits a narrowband thermal emission peak at the wavelength of 8.6 µm in the normal direction. The angular response of emission properties of the thermal emitter is dependent on the emission angle. We believe that our proposed thermal emitter provides an alternative for low-cost, high-effective narrowband mid-infrared light sources and would have a great potential in many applications.

High performance photodetectors operating in the mid-wavelength infrared spectral range are of great significance in many applications such as defense, surveillance, gas sensing, and night vision. A key parameter in the design of infrared detectors is the thickness of the absorber layer; reaching high absorption with a thin absorber layer can significantly enhance the performance of the device. In this work, we demonstrate the enhancement of InAs-base infrared detectors using surface plasmon nanostructures. Experimental results show that our device exhibits broadband enhancement compared to the reference with an increase in peak responsivity of about 50%. Further analysis shows that the enhancement of the device is attributed to the near-field localization effect of the plasma structure, which is well demonstrated by the experimental dual-peak spectrum. Such mechanisms provide valuable insight into the plasmon-enhanced infrared photodetector.

A metal–insulator–metal (MIM) planar trilayer thin-film nanostructure was used to realize a bolometric detector, which features compact design, simple structure and cost-efficiency.

Strain engineering is a powerful tool that can modulate semiconductor device performance. Here, we demonstrate that the bandgap of thin film (∼40 nm) black phosphorus (bP) can be continuously tuned from 2.9 to 3.9 μm by applying an in-plane uniaxial strain, as evidenced by mid-infrared photoluminescence (PL) spectroscopy. The deduced bandgap strain coefficients are ∼103 meV %^-1, which coincide with those obtained in few-layer bP. On the basis of first-principles calculations, the origin of the uniaxial tensile strain-induced PL enhancement is suggested to be due to the increase in both the effective mass ratio (m_e^*/m_h^*) and the bandgap, leading to the increment of the radiative efficiency. Moreover, the mid-infrared PL emission remains perfectly linear-polarized along the armchair direction regardless of tensile or compressive strain. The highly tunable bandgap of bP in the mid-infrared regime opens up opportunities for the realization of mid-infrared light-emitting diodes and lasers using layered materials.