A tunable infrared emitter based on phase-changing material GST for visible-infrared compatible camouflage with thermal management

Visible-infrared compatible camouflage is important to increase the counter-detection ability of a target due to the fast development of detection systems. However, most of the previously reported visible-infrared compatible camouflage structures are not suitable when the temperature of targets and type of background environment change. In this paper, we propose a tunable infrared emitter composed of ZnS/Ge/Ag/Ge2Sb2Te5/Ag films and numerically demonstrate visible-infrared compatible camouflage and radiation heat dissipation. Firstly, the proposed infrared emitter can produce different structural colors as the thickness of the ZnS film changes, which can be applied to visible camouflage. Secondly, the crystallization fraction of the Ge2Sb2Te5 (GST) layer could help to engineer the average emissivity of the proposed infrared emitter, achieving tunable mid-infrared (MIR) camouflage, radiation heat dissipation, and long-infrared (LIR) camouflage in wavelength ranges of 3-5 μm, 5-8 μm, and 8-14 μm, respectively. Finally, we numerically demonstrate the visible camouflage and infrared camouflage for different application scenarios by using the simulated visible and infrared images. This work has promising application potential in visible-infrared compatible camouflage technology.

Tunable near-perfect nonreciprocal radiation with a Weyl semimetal and graphene

A tunable near-perfect nonreciprocal thermal emitter, consisting of a dielectric plane and a monolayer graphene sandwiched between a subwavelength grating and a Weyl semimetal plane, is proposed and investigated. Near-complete nonreciprocal radiation can be achieved at resonance, breaking the traditional Kirchhoff's law. The underlying physical mechanism, resulting from a guided mode resonance, is disclosed by illustrating the magnetic field distribution. Moreover, the strong nonreciprocity remains well within a wide range of geometrical parameters. What's more, the performance of the near-perfect spectral nonreciprocity can be flexibly controlled in a wide spectral range through varying the Fermi level of graphene and the axial vector of the Weyl semimetal, which reduces the cost and should be interesting for real application. The conclusions of this paper should prompt the further development of tunable nonreciprocal thermal emitters.

Selective Mid-IR Metamaterial-Based Gas Sensor System: Proof of Concept and Performances Tests

In this paper, we propose a highly selective and efficient gas detection system based on a narrow-band IR metasurface emitter integrated with a resistive heater. In order to develop the sensor for the detection of specific gases, both the microheater and metasurface structures have been optimized in terms of geometry and materials. Devices with different metamaterial structures and geometries for the heater have been tested. Our prototype showed that the modification of the spectral response of metasurface-based structures is easily achieved by adapting the geometrical parameters of the plasmonic micro-/nanostructures in the metasurface. The advantage of this system is the on-chip integration of a thermal source with broad IR radiation with the metasurface structure, obtaining a compact selective radiation source. From the experimental data, narrow emission peaks (FWHM as low as 0.15 μm), corresponding to the CO₂, CH₄, and CO absorption bands, with a radiant power of a few mW were obtained. It has been shown that, by changing the bias voltage, a shift of a few tens of nm around the central emission wavelength can be obtained, allowing fine optimization for gas detection applications.