Infrared Emission Characteristics Research Articles

Infrared emission properties of VO2 films fabricated with different oxygen flow ratios

Infrared (IR) camouflage materials are widely used to realize thermal camouflage by adjusting the IR emissivity (ε) of the target object. However, ε modulation without an external energy supply is still a great challenge. Self-regulating VO2 films with different IR emission properties are investigated by adjusting the oxygen flow ratio (O2%) and film thickness. The ε of VO2 films changes before and after the phase transition, and the Δε (the difference of ε before and after the phase transition) of films is different under different O2%, and the maximum Δε can reach 0.49. In addition, the difference temperature (ΔTIR) between the actual temperature (TA: the surface temperature of a standard silicon wafer measured by IR camera, which represents the actual temperature of VO2 samples.) and the IR trapping temperature (TIR: the temperature of VO2 samples measured by IR camera.) is greater than 35 °C after the phase transition. With the range of 1.6 %–2.2 % O2, the IR emission transition temperature (Tε-MIT) and hysteretic width (ΔTε-MIT) increase with increasing O2%. The thickness of the VO2 film affects the IR emission characteristics. The VO2 film is suitable for thermal camouflage materials and for IR anticounterfeiting.

Preparation of copper ion doped strontium zirconate and its infrared emission characteristics

Cu2+ doped SrZrO3 (SrZr1-xCuxO3, x = 0, 0.01, 0.03, 0.05 and 0.07) perovskite powders were prepared by sol-gel method with Zr(NO3)4·5H2O, Sr(NO3)2 and Cu(NO3)2·2.5H2O as raw material. The influence of the ratio of metal ion to citric acid, pH value, and calcination temperature on the synthesis of high-purity SrZrO3 powder and the infrared emissivity characteristics of the synthesized material was systematically studied. XRD, XPS, FT-IR and dual-band emittance measuring instrument were used to study the phase composition, microstructure of the sample and the effect of copper ion doping on the infrared emittance of SrZrO3 at 3–5 μm. The results show that the infrared emissivity of SrZrO3 doped with Cu2+ is lower than that of SrZrO3. When x = 0.03, the infrared emissivity at room temperature of 3∼5 μm reaches the lowest value of 0.4259. With the increase of temperature and time, SrZr1-xCuxO3 showed better thermal infrared properties, and the samples all showed weak thermal infrared intensity, and the surface temperature was lower than the background temperature and relatively stable. These findings suggest that Cu2+-doped SrZrO3 holds great potential as a promising candidate material for infrared stealth applications.

Femtosecond laser fabrication of silicon surface microstructures for enhanced infrared radiation under electric drive

Silicon surface microstructures can significantly improve their reflection and absorption characteristics and are widely used in photovoltaics and optoelectronic detection. But there is little research on the infrared emission characteristics of microstructure silicon since silicon is an indirect bandgap material. Here, we fabricate surface microstructures on highly doped silicon by femtosecond laser scanning, enhancing its broadband infrared radiation significantly under electric driving. At 12 μm, it can be enhanced to 274% of the untreated silicon. Our results show that silicon with surface microstructures can be used as a wideband infrared emitter. This study provides a new method for realizing a broad-spectrum silicon-based electrical drive infrared light source.

Evolution of fullerenes in circumstellar envelopes by carbon condensation: insights from reactive molecular dynamics simulations

ABSTRACT Fullerenes, including C60 and C70, have been detected in various astronomical environments. Understanding how their structures evolve over time is essential for gaining insights into their life cycle and making further observations. To address this, we conducted reactive molecular dynamics simulations to investigate the evolution of fullerenes in the circumstellar envelopes surrounding carbon-rich asymptotic giant branch stars. Our simulations employed a bottom-up chemistry scheme, wherein fullerenes grow by absorbing and condensing small carbon-based molecules. The results revealed the formation of different structures through heterogeneous reactions based on hydrogen concentration, leading to the emergence of onion-like nanostructures or single-layer fullerenes. To examine the impact of these structural changes on the infrared emission characteristics of fullerenes, we performed quantum chemical calculations. The results indicate that as fullerenes grow larger, additional emission features are introduced in the infrared spectrum. Moreover, two-layered fullerenes show noticeable blueshift or weakening effects on the bands associated with out-of-plane vibration modes.

Numerical study on enhanced radiation cooling characteristics of Ti-GE-W microstructure surfaces

Surfaces with high infrared emission characteristics in the atmosphere window range (8–13 μm) play a pivotal role in radiation cooling. In this paper, a Ti-Ge-W based metamaterial was proposed as a cooling surface and the influence of its geometric parameters on the emissivity was analyzed as well. Studies of the physical mechanism showed that: The spectral emissivity of the single structure can reach over 80% in the range of 9–13 μm. In contrast, the expansion of more Ti strips in the horizontal direction can effectively broaden the emission spectrum and enhance the radiation performance. Due to the coupling effect between the surface plasmon polaritons (SPPs) and magnetic polarizations (MPs), the structures showed strong absorption properties, leading to strong emissivity according to Kirchhoff's Law. This research provides a new idea in radiation cooling, which is of great value in building cooling, aerospace refrigeration, and other fields.

激光诱导表面周期性结构对铜薄膜红外发射特性的改变

激光诱导表面周期性结构对铜薄膜红外发射特性的改变

Effect of heating/cooling dynamics in the hysteresis loop and tunable IR emissivity of VO2 thin films

We experimentally investigate the semiconductor-to-metal transition (SMT) in vanadium dioxide thin films using an infrared thermographic technique. During the semiconductor to metal phase change process, VO2 optical properties dynamically change and infrared emission undergoes a hysteresis loop due to differences between heating and cooling stages. The shape of the hysteresis loop was accurately monitored under different dynamic heating/cooling rates. In order to quantify and understand the effects of different rates, we used a numerical modelling approach in which a VO2 thin layer was modeled as metamaterial. The main experimental findings are interpreted assuming that both the rate of formation and shape of metallic inclusions are tuned with the heating/cooling rate. The structural transition from monoclinic to tetragonal phases is the main mechanism for controlling the global properties of the phase transition. However, our experimental results reveal that the dynamics of the heating/cooling process can become a useful parameter for further tuning options and lays out a macroscopic optical sensing scheme for the microscopic phase change dynamics of VO2. Our study sheds light on phase-transition dynamics and their effect on the infrared emission spectra of VO2 thin films, therefore enabling the heating/cooling rate to be an additional parameter to control infrared emission characteristics of thermal emitters. The hysteresis loop represents the phase coexistence region, thus being of fundamental importance for several applications, such as the operation of radiative thermal logic elements based on phase transition materials. For such applications, the phase transition region is shifted for heating and cooling processes. We also show that, depending on the way the phase change elements are heated, the temperature operation range will be slightly modified.

OBSCURANT AND EMISSION CHARACTERISTICS OF THE SCREENING SMOKE COMPOSITIONS USED IN NAVAL SHIPS

Obscurant and optronic decoy compositions are the pyrotechnic formulations that are an effective way to protect naval ships from optical guided missile seekers. In this work, the obscurant characteristics (i.e. the transmittance and the extinction coefficient) and the infrared emission characteristics (i.e. the infrared emission distribution and the radiance) of the obscurant and optronic decoy compositions were described. The results showed that the obscurant cloud made from the mixture of red phosphorus, Ba(NO3)2 and Viton rubber has a low transmittance, high extinction coefficient with 1.06 µm laser and strong infrared emission in the wavelength range of 8.0 to 14.0 µm. On the other hand, the infrared emission radiance (in the wavelength range of 2.5 to 5.0 µm) of the optronic decoy composition based on Mg-Al, hexachloroethane and Viton rubber reaches maximum values (i.e. 17.77E-3 W.cm-2.Sr-1) at about 17 wt% Mg-Al. Finally, the above obscurant and optronic decoy compositions can be used combination in naval ships against the anti-ship missile.

Effects of Mg Al Alloy Powder on the Combustion and Infrared Emission Characteristics of the Mg Al PTFE Viton Composition

Metal-Fluorocarbon compositions are the pyrotechnic formulations which have been widely used in infrared decoy flares to protect aerial targets from infrared guide missile seekers. In this work, the effect of Mg-Al alloy powder (i.e. the particle size and the content) on the combustion and the infrared emission characteristics (i.e. the infrared emission distribution and the infrared radiance) of the pyrotechnic composition based on Mg-Al alloy, polytetrafluoroethylene (PTFE) and Viton rubber are described. The results show that the high burning rate (with the values of 4.0 mm.s-1 to 10.0 mm.s-1, depend on the compression density) of this composition is achieved with a high content of Mg-Al alloy or when using fine Mg-Al alloy particles as well as coarse PTFE particles. On the other hand, the infrared emission radiance (in the wavelength range of 2.5 μm to 5.0 μm) of Mg-Al/PTFE/Viton composition reaches maximum values (i.e. 17.7 W.cm-2.Sr-1 and 21.0 W.cm-2.Sr-1 with the size of Mg-Al particles are 20 μm and 120 μm, respectively) at 60 wt% Mg-Al alloy. Finally, the Mg-Al/PTFE/Viton composition has a similar combustion and emission characteristics as the Mg/PTFE/Viton composition.

Synthesis and the characterization for transition metal-ion based photonics: Broadband near-IR emission properties of nickel ion doped NaSbO3 ceramics

We report the preparation method and broadband near infrared emission characteristics of nickel ion-doped NaSbO3 ceramics in an easy way. Selective doping of Ni2+ ions into proper octahedral sites is crucial to the enhancement of broadband near-infrared (NIR) emission. In this work, a broadband NIR emission with central wavelength at 1430 nm and with a full-width-at-half-maximum (FWHM) of 230 nm is reported from Ni2+ ion-doped perovskite NaSbO3 lattice, which has never been reported until now, to the best of our knowledge. Nickel ion doped NaSbO3 nanocrystals was elaborated to show the prospect that this kind of perovskite nanostructure is promising for transition metal ion (TMI) based photonics. A red shift of the emission spectra is observed comparing to the most of the former research, which is due to the Ni2+ ions embedded into the low crystal field. The broadband of NIR emission in the NaSbO3: Ni2+ ceramics do not only cover the whole second biological NIR region, but also present a new novel structure to approach the broadband emission spectra for TMI ions.

Adaptive tuning of infrared emission using VO2 thin films

Phase-transition materials provide exciting opportunities for controlling optical properties of photonic devices dynamically. Here, we systematically investigate the infrared emission from a thin film of vanadium dioxide (VO2). We experimentally demonstrate that such thin films are promising candidates to tune and control the thermal radiation of an underlying hot body with different emissivity features. In particular, we studied two different heat sources with completely different emissivity features, i.e. a black body-like and a mirror-like heated body. The infrared emission characteristics were investigated in the 3.5–5.1 μm spectral range using the infrared thermography technique which included heating the sample, and then cooling back. Experimental results were theoretically analyzed by modelling the VO2 film as a metamaterial for a temperature range close to its critical temperature. Our systematic study reveals that VO2 thin films with just one layer 80 nm thick has the potential to develop completely different dynamic tuning of infrared radiation, enabling both black-body emission suppression and as well as mirror emissivity boosting, in the same single layer device. Understanding the dynamics and effects of thermal tuning on infrared emission will benefit wide range of infrared technologies including thermal emitters, sensors, active IR filters and detectors.

Band optimization of passive methane gas leak detection based on uncooled infrared focal plane array.

Current methane gas leak detection technology uses infrared imaging in the medium wave (MW) or long wave (LW) bands, essentially applying cooled infrared detectors. In this study, a simplified three-layer radiative transfer model is adopted based on methane gas detection theory, considering background radiation, atmospheric infrared absorption, gas absorption, and emission characteristics to analyze the contrast of methane gas thermography in different infrared bands. The analysis results suggest that under certain conditions, the 6.6-8.6μm LW band provides higher contrast compared to the 3-5μm MW band. The optimal imaging wavelength band is selected according to imaging contrast advantages and disadvantages, and infrared optical systems and infrared filters are designed and optimized. We build a passive methane gas leak detection system based on uncooled infrared focal plane array detectors. By collecting gas images under different conditions, the imaging detection capabilities for methane gas leaks in the MW and LW bands in a laboratory environment are compared. Finally, the developing trends in methane gas detection technology are analyzed.

Multi-angular thermal infrared emission characteristics of Bohai Sea ice based on in situ measurements

AbstractWe report on the radiative transfer process and optical properties of sea ice in the thermal infrared (TIR) band, presenting two new linear kernel driver models (Relative Emissivity Distribution Function, REDF) that describe TIR emission characteristics of smooth and rough ice. In order to test the models and determine the necessary coefficients, in situ measurements from the Bohai Sea were carried out during the 2011/12 and 2012/13 boreal winters. The results show that the relative emissivity of smooth sea ice decreases along with increasing viewing zenith angle, and the shape of the relative emissivity curve is similar to that of an ideal plane. Affected by parameters such as roughness and surface temperature distribution, the anisotropy of relative emissivity of sea ice with a high degree of roughness is stronger relative to the cosine emitter. The model coefficients were also obtained using a robust regression method based on the measured data. The presented models are more practical than the numerical radiative transfer model and can be used for multi-angular TIR remote sensing.

Infrared Studies on the Jet Exhaust of a Turbojet Aircraft

In an attempt to evaluate the effective Infrared radiant energy from a conical jet exhaust of a jet aircraft, infrared emission characteristics have been worked out with special reference to guidance and decoy purpose.Suitable infrared absorbing materials used for shielding the infrared emitting skin of the radiating part have also been discussed.attempts have also been made to evaluate the effective radiation on a detecting system after allowing for allowing for the solar radiant heat and also atmospheric absorption.

1.53 μm emission properties in Er3+ doped Y2O3 and Nb2O5 modified germanate glasses for an optical amplifier

Er3+ doped Y2O3 and Nb2O5 modified germanate glasses have been reported which possesses excellent thermal stability. Near infrared emission characteristics upon excitation of a conventional 980nm laser diode have been investigated. According to absorption spectra and refractive index, Judd–Ofelt intensity parameters, spontaneous radiative transition probabilities, radiative lifetimes and stimulated emission cross sections have been calculated and discussed. These results indicate that the predicted spontaneous transition probability and emission cross section of Er3+:4I13/2→4I15/2 transition in developed glasses can reach as large as 192.39s−1 and 7.14×10−21cm2, respectively. Hence, germanate glasses with superior performances might be a useful material for applications in optical amplifiers around 1.53μm.

The effects of total gas pressure and Xe partial pressure on the properties of plasma display panels with two-opposite-electrode cells

The effects of total pressure and Xe partial pressure on the characteristics of an alternating-current plasma display panel with a two-opposite-electrode discharge cell configuration and a three-electrode surface-discharge cell configuration were investigated in terms of the following electro-optical properties: breakdown voltage, sustain voltage, wall charge transfer curve, infrared emission characteristics, luminance and luminous efficacy. Despite the longer discharge gap length, the results of the experiment and three-dimensional plasma simulation indicated that the opposite-discharge configuration has a significantly lower breakdown voltage than the surface-discharge configuration. Furthermore, the ratio of the increase in the breakdown voltage for the opposite-discharge configuration to the incremental Xe partial pressure was found to be smaller than that of the surface-discharge configuration. Because of its low driving voltage and possible use of high-Xe partial pressure, the opposite-discharge mode exhibited a higher luminous efficacy compared with the surface-discharge mode. These results indicated that the two-opposite-electrode discharge cell configuration has a cost reduction potential in electronics as well as high efficacy for plasma displays.

∼2 µm Luminescence and energy transfer characteristics in Tm3+/Ho3+co-doped silicate glass

A Tm3+/Ho3+ co-doped silicate glass with good thermal stability is prepared by the melt-quenching method. Efficient ∼2μm emission is observed under 808nm laser excitation. The infrared emission characteristics and energy transfer mechanism are investigated. To obtain efficient ∼2μm emission, the optimized concentration ratio of Tm3+ to Ho3+ is found to be 0.75:0.4 in the present silicate glass system. Additionally, the energy transfer between Tm3+ and Ho3+ plays an important role in the luminescence mechanism and energy transfer efficiency from Tm3+ to Ho3+ reaches 88%. The emission property together with good thermal property indicates that Tm3+/Ho3+ co-doped silicate glass is a potential kind of laser glass for efficient 2μm laser.

Influence of optical basicity on broadband near infrared emission in bismuth doped aluminosilicate glasses

The infrared luminescence with a full width at half maximum larger than 200 nm was observed in aluminosilicate glasses under an 808 nm LD excitation. The influence of optical basicity on broadband near infrared emission was investigated in bismuth doped aluminosilicate glasses. The intensity of the infrared fluorescence decreases with the increase in the optical basicity of the host glasses. On the base of the luminescence spectra, we thought the infrared emission might be attributed to low valence state of bismuth ions in the aluminosilicate glasses. The broadband infrared emission characteristics of the glasses suggest that they are promising candidate for broadband optical fiber amplifiers and tunable lasers.

13.4: Three‐Dimensional Observations of Reset and Address Discharges of Plasma Display Panel

AbstractThree‐dimensional infrared emission characteristics of a weak discharge in reset period and two different discharge modes in address period were investigated with 3‐D test panel. Based on 3‐D infrared emissions measured in reset period, the infrared from the cathode were not observed all during the rising and falling ramp reset period and these characteristics are closely related to the electron energy near the cathode. Based on the front and side images of the weak discharge in reset period, the address discharge mode is estimated and experimentally confirmed with the 3‐D test panel. In addition, depending upon various driving conditions, two address discharge modes (single‐tail and double‐tail modes) were observed and discussed.

Emission characteristics, crystalline phase and composition of vapor-transport-equilibrated Er:LiNbO 3 crystal codoped with 6 mol% MgO

Polarized downconversion, 980-nm-upconversion and near-infrared emission characteristics of vapor-transport-equilibrated (VTEed) bulk Er (0.4 mol%)/MgO (6 mol%)-codoped LiNbO 3 crystals were investigated. The downconversion and upconversion visible emissions display similar VTE effects including the drop of emission intensity and the weakening of polarization dependence. At 0.98 and 1.5 μm regions, the VTE has a weak effect on the emission intensity, but a strong effect on the spectral shape. The crystalline phases in these bulk Er/Mg-codoped VTE crystals are determined by comparing their infrared emission characteristics with those of pure ErNbO 4 powder and locally Er-doped MgO (4.5 mol%):LiNbO 3 crystal. The results show that the Er 3+ ions present in these bulk Er/Mg-codoped VTE crystals as a mixture of Er:LiNbO 3 and ErNbO 4 phases. The percentages of the ErNbO 4 phase contained in these VTE crystals were evaluated from the 1531 and 1536 nm characteristic absorption areas. The contents of constituent elements were determined by chemical analysis.