Comparison of the spectra of a blackbody and thermally stimulated surface plasmon polaritons in the infrared range

The emission spectra of thermally stimulated surface plasmon polaritons (thermally stimulated surface plasmon polaritons) and a blackbody have been analyzed and compared, and the temperature dependence of these spectra has been studied. It has been found that the total energy of the entire ensemble of surface plasmons is proportional to the cube of temperature and their spectrum is red-shifted from the blackbody spectrum. It has been shown that the spectrum of thermally stimulated surface plasmon polaritons obeys the Wien’s displacement law, yet with another constant. The fraction of the photon energy of the conducting layer transferred to the surface plasmons has been estimated. It has been demonstrated numerically by the example of a gold layer that this fraction can exceed 10% for a layer thickness of less than 1 mm.     

Femtosecond laser-induced surface structures to significantly improve the thermal emission of light from metals

Extraordinary thermal emission properties of the metallic surface microstructures induced by femtosecond lasers are investigated in both experiment and theory. Within the spectral range of 4–17 μm, the measured maximum thermal emissivities at different temperatures enhance significantly to about 100%. Especially for the coral-like surface structure, the improved thermal emission behaviors can extend largely over the whole spectrum rather than happening at some distinctive wavelengths. Moreover, the enhancement factor of the thermal emissivity is observed to depend on the wavelength and the idiographic morphology of the microstructures. This phenomenon can be understood well by equivalent recognizing the SPP field coupling assisted transmission of blackbody radiation through the microstructured interfaces, and the finite-difference time-domain simulations elucidate the underlying physical pictures.     

Synchrotron radiation spectrum for galactic-sized plasma filaments

The radiation spectrum for synchrotron-emitting electrons in galactic-sized Birkeland current filaments is analyzed. It is shown that the number of filaments required to thermalize the emission spectrum to blackbody is not reduced when a non-Maxwellian electron distribution is assumed. If the cosmic background radiation (CBR) spectrum (T=2.76 K) is due to absorption and re-emission of radiation from galactic-sized current filaments, higher-order synchrotron modes are not as highly self absorbed as lower-order modes, resulting in a distortion of the blackbody curve at higher frequencies. This is especially true for a non-Maxwellian distribution of electrons for which the emission coefficient at high frequencies is shown to be significantly less than that for a Maxwellian distribution. The deviation of the CBR spectrum in the high-frequency regime may thus be derivable from actual astrophysical parameters, such as filamentary magnetic fields and electron energies in the model     

阵列型微波黑体的发射率分析

在微波波段, 用于标定温度和辐射功率的发射率接近于1的标准发射率器件, 即微波频段的黑体, 结构形式一般为表面涂覆吸波材料的金属锥体阵列. 这种黑体器件常用于为微波辐射计提供参考亮温, 要求具有高发射率和均匀的温度分布. 对此类黑体器件的发射率评估主要基于基尔霍夫热平衡定律, 即通过评估反射率来确定发射率. 已报道的研究集中在黑体发射率随频率的变化趋势, 较少针对其随方向和极化状态的变化趋势. 本文针对此类周期型排布的黑体, 提出基于Floquet模式分析的反射率评估方法, 相比已报道的基于后向散射的评估方法, 具有更大的适用范围. 基于这种方法, 对某黑体的发射率随频率、角度和极化状态的变化规律进行了计算分析. 分析结果表明: 此黑体发射率在X到K_α波段内随频率提高而增大; 在发射率较低的低频处, 垂直极化与水平极化的发射率随俯仰角的变化趋势不同, 并且存在垂直极化发射率随俯仰角增大而明显降低的现象. 这些规律均与其物理上低频段内涂层对电磁波的衰减特性相符合.     

Spectrum of luminescence from laser-created bubbles in water

The spectrum of the luminescence emitted at the collapse of single laser-induced bubbles in water is measured for different maximum bubble radii. Bubbles as large as 2 mm show a molecular OH(*) band at 310 nm in the spectrum, which otherwise can be fitted approximately with a blackbody curve at a temperature of 7800 K. This finding provides a connection between the light emission of single bubbles and multibubble sonoluminescence, since in the latter case the same molecular band is observed. Surface instabilities are observed in the larger bubbles, and may be connected with the OH(*) emission.     

The origin of polarized blackbody radiation from resistively heated multiwalled carbon nanotubes

We observed very pronounced polarization of light emitted by highly aligned free-standing multiwall carbon nanotube (MWNT) sheet in axial direction which is turned to the perpendicular polarization when a number of layers are increased. The radiation spectrum of resistively heated MWNT sheet closely follows to the Plank's blackbody radiation distribution. The obtained polarization features can be described by a classical dielectric cylindrical shell model, taking into consideration the contribution of delocalized π-electrons (π surface plasmons). In absorption (emission) the optical transverse polarizability, which is much smaller than longitudinal one, is substantially suppressed by depolarization effect due to screening by induced charges. This phenomenon suggests very simple and precise method to estimate the alignment of nanotubes in bundles or large assemblies.     

Optical characterisation of the photolytic decomposition of ferrocene into nanoparticles

Optical emission from the photolytic dissociation of ferrocene Fe(C₅H₅)₂, often abbreviated as FeCp₂, in argon atmosphere was studied. The dissociation was performed by using an ArF excimer laser, operating at a wavelength of 193 nm. Two pressure regions were examined. At low (0.1 mbar) pressure, several emission lines of Fe could be identified, however no C, C₂, or CH emission lines/bands were found. At a higher (20 mbar) pressure of the FeCp₂/Ar gas mixture, a broadband emission identified as blackbody radiation was observed. This blackbody radiation originates from nanoparticles with a mean size of 30 nm, which consist of both metallic iron and amorphous carbon. The initial colour temperature of the particles was 2600 K.     

The Influence of the Temperature of Blackbody for Calibrating FTIR System on the Instrument Response Function∗

The instrument response function of Fourier transform infrared spectrometer is a very important parameter in infrared emission Spectroscopy to obtain infrared spectral radiance distribution of the desired sample, the concentrations of the components of combustion products in the flame etc. This paper gives the effect of the temperature of the standard blackbody for calibrating Fourier transform infrared spectrometer on the instrument response function. The result illustrates that the values of the instrument response functions decrease as the blackbody temperature increased, and tends to a limit. The paper points out that the condition must be observed for using instrument response function correctly.

     

Thermal radiation from photonic crystals: a direct calculation

A classical simulation of equilibrium thermal emissivity from dispersive, lossy photonic crystals is presented. Normal emission results consistent with those assuming Kirchoff's law are obtained; i.e., a photonic crystal does not emit more than what a blackbody does. Significant enhancement, however, can be achieved over the radiation intensity from a uniform slab, indicating the potential usefulness of photonic crystals in incandescent lighting and thermal photovoltaic applications.     

纳秒脉冲激光诱导空气等离子体的近红外辐射特性

开展纳秒激光诱导空气等离子体近红外辐射特性的实验研究,对波长为532 nm的脉冲ns激光诱导产生的空气等离子体的近红外光谱进行测量.结果表明:空气等离子体的近红外辐射在光谱范围为1100-2400 nm内由连续谱和线状谱组成,光谱指认表明线谱主要来源于N,O原子的中性原子谱和氮分子的振动光谱.通过对连续谱的分析得知,黑体辐射是连续辐射的主要来源.空气中波长1128 nm附近的辐射,可能是N和O中性原子谱的贡献.保持真空腔内气压不变,改变腔内氮气和氧气气体组分含量,分析测得的红外光谱数据,可知混合气体中氧气和氮气含量变化只对波长为1128 nm附近的辐射有影响.利用二元线性回归分析对数据进行分析后得知,氧气对波长为1128 nm附近的辐射贡献较大.最后从电离难易的角度分析造成这一结果的原因.     

Photon emission from polycrystalline Ag induced by scanning tunneling microscopy: comparison of different tip materials

Photon emission from polycrystalline silver induced by scanning tunneling microscopy is studied for three different tip materials (Au, PtIr and W). Photon emission intensity curves as a function of the tip voltage are observed to be almost identical for platinum-iridium alloy and gold tips (and more than 10 times enhanced as compared with the tungsten tip). An evolution in topography and photon map for different applied voltages is investigated along with the study of the spatial distribution of photon emission in dependence upon the surface local differential height. It turns out that no clear correlation between a local curvature and enhancement of light emission can be found. Simultaneous measurements of tunneling current and photon intensity as a function of vertical tip displacement confirm the earlier observation, namely, that similar apparent barrier heights exist for both elastic and inelastic tunneling channels. The role of the tip material as well as its shape is discussed.     

Two modes of electroluminescence from single‐walled carbon nanotubes

The electroluminescence from single‐walled carbon nanotube field effect transistors is spectrally resolved, and shows two distinct modes of light emission. The vast majority of nanotubes have spectrally broad emission consistent with the spectrum of blackbody radiation. Much more rarely, superposed on the broad emission is a single narrow (<50 meV) peak which is consistent with expectation for electron–hole recombination. The narrow emission is strong even at lower biases and in general has greater peak intensity than the broadband emission. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sonoluminescence: nature's smallest blackbody

The transduction of sound into light through the implosion of a bubble of gas leads to a flash of light whose duration is delineated in picoseconds. Combined measurements of spectral irradiance, Mie scattering, and flash width (as determined by time-correlated single-photon counting) suggest that sonoluminescence from hydrogen and noble-gas bubbles is radiation from a blackbody with temperatures ranging from 6000 K (H(2)) to 20,000 K (He) and a surface of emission whose radius ranges from 0.1 microm (He) to 0.4 microm (Xe) . The state of matter that would admit photon-matter equilibrium under such conditions is a mystery.     

Abnormal properties of spontaneous emission in a Kerr nonlinear blackbody

We reexamine the atomic spontaneous decay in a Kerr nonlinear blackbody by contrast with our previous paper [M. Yin, Z. Cheng, Phys. Rev. A 78 (2008) 063829]. In the process of deriving the atomic decay rate, we use the temperature-dependent velocity of photons to take the full nonlinearity of a KNB into account. It is found that below a transition temperature T_c, the atomic spontaneous emission in a KNB might be enhanced or inhibited compared with that in a normal blackbody whose interior is filled with a nonabsorbing linear medium. The physical origin of the enhancement and inhibition of spontaneous emission is also discussed.     

Thermodynamic Properties of an Atom Inside a Kerr Nonlinear Blackbody

Thermodynamic properties of a Kerr nonlinear blackbody (KNB) are investigated. It is found that below a transition temperature T _c , the free energy of a KNB radiation is larger than that in a normal blackbody. At the transition from KNB radiation state to a normal blackbody radiation state, the photon system undergoes a first-order phase transition. The thermodynamic system of an atom interacting with a KNB radiation bath is also investigated by using a thermodynamic perturbation theory. It is found that below a transition temperature T _c , the increment of the free energy of the atom is larger than that in a normal blackbody. Above T _c , the KNB becomes a normal blackbody, and the properties in a KNB turn to be the same as those in normal blackbody radiation.     

EQUINOX55型遥感傅里叶变换红外光谱系统的校正

利用遥感傅 里叶变换红外发射光谱，对红外辐射源的绝对光谱能量分布和热气体浓度进行测量时，首先必须对测得的红外辐射源的发射光谱强度进行校正，为此，需用已知温度的标准绝对黑体对系统进行校正，本文考察了黑体温度对EQUINOX55型遥感傅里叶变换红外光谱的响应函数的影响。结果表明，仪器响应函数随着温度的升高而增加，但当温度比较高时，仪器响应函数曲线变化趋小。     

Tunable thermal emission at infrared frequencies via tungsten gratings

The author investigates the manipulation of thermal emission by using one-dimensional tungsten gratings with different groove depths. It is found that, by systematically increasing the depth of the groove, the linearly polarized emission at particular frequencies can be substantially enhanced to achieve that of the blackbody radiation limit, whereas the emission in other frequency ranges shows no noticeable changes. The results can provide useful insights into the design of thermovoltaic applications.     

基于MATLAB的黑体辐射量计算

介绍了黑体辐射理论,利用MATLAB求解了普朗克黑体辐射公式在有界域λ1～λ2内的积分,通过实例对梯形法和辛普森法两种数值积分方法进行了分析和比较。并在此基础上对距黑体一定距离处探测器表面的辐照度值E进行了研究。通过分析可知,利用梯形法和辛普森法能够方便求出黑体在有界域内的辐出度值。此外,利用MATLAB编制的相应的计算界面,能够实现辐出度和辐照度的快速计算。     

A method to retrieve blackbody temperature errors in the two points radiometric calibration

Measurements of the atmospheric thermal emission using an infrared Fourier transform spectrometer need to be radiometrically calibrated. As for several existing instruments (IASI-MetOp, IASI-balloon, NAST-I, AERI, etc.), the two points radiometric calibration is generally performed using two well-characterized blackbodies at two different temperatures (or one blackbody and the cold space), which allow to determine the response and the self-emission of the instrument. To perform an accurate radiometric calibration, the emissivity and the temperature of each blackbody should be known accurately. The blackbody temperatures are chosen to fit the characteristics of the instrument. The measurement of these temperatures is essential. This paper proposes a method to perform an accurate radiometric calibration even when one of the two blackbodies temperatures is not perfectly measured, by numerically retrieving this erroneous temperature.