VO2 film is expected to be used in smart radiation devices (SRD) due to changes in infrared reflection caused by semiconductor-to-metal transition (SMT). In this work, a tunable thermal emitter which consisted of Al layer, CaF2 layer and VO2 layer was designed to achieve variable emittance with temperature. The variation of dielectric parameters of VO2 shell caused by temperature change was used to regulate the absorption characteristics of the structure, to realize the positive emittance-switching performance of the thermal emitter device. It was found that the total emittance of the device could reversibly change from 0.03 at 30℃ to 0.72 at 90℃ with an emittance variability of 0.69 in 4-14 µm. In addition, the influence of the thickness of CaF2, VO2 layers and the intermediate layer material on the emittance variation of the device was studied. These results shown that the device has the best VO2 and CaF2 layer thicknesses of 20nm and 1000nm, respectively. Particularly, too high refractive index of the intermediate layer material will cause the device to produce multiple resonance peaks at high temperature, which will reduce the average emissivity of the entire band, resulting in a smaller change in the emissivity of the thermal emitter.
In this paper, radiation spectrum design methods of material were proposed. Effect of temperature and atmospheric transmission on the infrared radiation transmission of materials was studied. The radiation properties of different materials were analyzed at different temperature. The transmission of aircraft surface materials infrared radiation was studied, according to the environment and the radiation transmission. Moreover, the spectrum of the two materials with the consistent emissivity was studied. Material has less radiation characteristic peak within the 3.0−4.3 μm and low radiation intensity within the 8−14 μm, which has good spectral stealth properties at 250−450 K. The radiation spectrum peak of the material was not obvious within the 4.3−8.0 μm owing to the low transmittance of atmosphere. In conclusion, research results have good significance for the spectral stealth design of materials, and can potentially be used in infrared spectral stealth technology and equipment.
Mid-infrared (MIR, 2-6 μm wavelength) transparent metal oxides are attractive materials for planar integrated photonic devices for sensing applications. In this study, we present reactive sputtering deposited ZrO2-TiO2 (ZTO) thin films as a new material candidate for integrated MIR photonics. We demonstrate that amorphous ZTO thin films can be achieved with Ti concentration of 40 at.%. With increasing Ti concentration, the optical band gap decreases monotonically from 4.34 eV to 4.11 eV, while the index of refraction increases from 2.14 to 2.24 at 1 μm wavelength. MIR micro-disk resonators on MgO substrates are demonstrated using Ge23/Sb7S70/Zr0.6Ti0.4O2 strip-loaded waveguides with a loaded quality factor of ~11,000 at 5.2 μm wavelength. By comparing with a reference device of Ge23Sb7S70 resonator on MgO and simulating the optical confinement factors, the ZTO thin film loss is estimated to be below 10 dB/cm. Single mode shallow ridge waveguides with a ridge height of 400 nm and a slab height of 1.7 μm are also demonstrated using ZrO2 thin films on MgO substrates. The low loss, relatively high index of refraction, superior stability and proven CMOS compatibility of ZTO thin films make them highly attractive for MIR integrated photonics.
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