Correlation tensors of the blackbody radiation in rectangular cavities

Electromagnetic equilibrium fluctuations in finite cavities filled with a dissipative medium (dielectric function ()=+i) and bounded by walls of infinite conductivity are considered. Expanding the fields in terms of a complete and orthonormal set of functions and solving the Maxwell equations the response of the EM field to external forces (polarization and magnetization) is obtained. With the aid of the fluctuation dissipation theorem and the linear response functions the 2nd order correlation tensors of the EM field are derived.For rectangular cavities explicit considerations are made. In the case of transparent media (=0) the spectral energy density of the EM radiation is calculated.     

Modified radiation laws of a rectangular Kerr nonlinear blackbody

A Kerr nonlinear blackbody (KNB) is a new kind of blackbody in which bare photons with opposite wave vectors and helicities are bound into pairs and unpaired photons are transformed into nonpolaritons. In the present paper, we focus our investigation on the modified radiation laws, such as Planck and Stefan-Boltzmann radiation laws, of a rectangular KNB. Besides, the case of a KNB with no symmetry axes is also discussed. Finally, we make a numerical calculation of modified radiation laws of a cubic KNB under appropriate conditions, and we consider this work may lay the foundation for the experimental verification of the model of a KNB.     

Autocorrelation functions of the blackbody radiation in cavities with walls of finite conductivity

Electromagnetic equilibrium fluctuations in cavities with non ideal metallic walls are considered. On the boundary the electric and magnetic fields are connected by Leontovich's boundary condition. With the aid of Maxwell's equations and Leontovich's relation the response of the EM-field to a polarization field is calculated. The correlation functions of the EM-field are then given by the fluctuation dissipation theorem. For cube shaped cavities explicit considerations are made. Expressing the surface impedance by a frequency independent conductivity the volume averaged autocorrelation functions of the EM-field and the total energy density are calculated. Besides the contributions due to the normal modes an additional term is found which characterizes the contributions due to the evanescent waves existing near the internal surface of the cavity. As a consequence of the frequency dependence of the impedance this term shows aT ^7/2 dependence.     

Mechanism of blackbody radiation

The law of error for Bose statistics is not unique; the family of probability distributions differ insofar as zero-point energy is concerned. This is traced back to the spontaneous emission term in the Einstein mechanism of emission and absorption of radiation. It is argued that the spontaneous emission term is unimportant for blackbody radiation and an alternative mechanism is proposed in which thermal equilibrium is secured through a constraint on the number of quanta in any given mode of the radiation field. Both mechanisms predict a modification of the Maxwell velocity distribution at high frequencies and are compared in relation to Doppler broadening and their low-temperature behavior.     

蒙特-卡罗法计算黑体空腔有效发射率

介绍了蒙特-卡罗法计算黑体空腔发射率的基本思想和主要算法。首先阐述了计算黑体空腔有效发射率的理论基础,然后分别从正向光线追迹和逆向光线追迹的角度对蒙特-卡罗法的具体算法予以说明,提出逆向追迹思想能方便地计算空腔的定向有效发射率,经过运算可以得到腔积分半球有效发射率和平均垂直有效发射率。最后对比了采用蒙特-卡罗法和其它方法的计算结果,分析表明：蒙特-卡罗法在计算黑体空腔有效发射率上是准确的,劣势在于计算速度慢。     

Center frequency formulation of the blackbody radiation spectrum

The blackbody radiation spectrum is described in terms of a resonance curve that is composed of an excitation function, x⁵, and a damping function, e^–x, where x=h/kT. The energy radiated per unit area per second is expressed as E(, T)d=Kx⁵e^–xd. This mathematically simple and physically transparent formulation reproduces the features of the blackbody radiation curve and contains the valid temperature radiation laws. With the help of that formula, the blackbody radiation spectrum is also expressed in terms of the previously introduced Center Frequency concept. We derive a Center Frequency Law of Blackbody Radiation and use it to calculate the Stefan-Boltzmann radiation constant in close agreement with the best available data.     

Quantum tunneling in a blackbody radiation field

It is generally considered that for a so-called normal system dissipation decreases tunneling rates. Here we show that at least one example of a normal heat bath, the blackbody radiation field, leads to an increase in tunneling. The reason for this exception to the general rule is the presence of mass renormalization.     

黑体辐射公式的量纲分析

量纲分析是研究物理问题的重要方法之一.本文对量纲分析的解题步骤做了梳理归纳,并对于黑体辐射公式进行了量纲分析.     

星载定标黑体午夜太阳辐照模拟实验

为了揭示午夜太阳辐射对三轴稳定卫星光学载荷的定标黑体温度均匀性和定标精度的影响,进行了基于贴片加热电阻外热流模拟方法的真空实验,利用电压变化产生的加热功率模拟复杂的太阳辐照度波动。将实验获取的温度数据与仿真计算结果对照验证,分析了太阳照射过程中黑体温度分布的规律。根据辐射度学理论,对温度不均匀性产生的定标误差进行了理论计算。实验结果显示:在午夜太阳照射过程中,边缘受照的黑体温度分布具有对称性,黑体最高升温幅度为8.8K,最大温度梯度3.1K/m,定标相对误差0.1%。研究表明:太阳辐射会显著影响黑体温度的均匀性,由此产生的定标精度误差不会影响工程应用的要求。     

Atomic clocks with suppressed blackbody radiation shift

We develop a concept of atomic clocks where the blackbody radiation shift and its fluctuations can be suppressed by 1-3 orders of magnitude independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies ν1 and ν2) which are exposed to the same thermal environment, there exists a "synthetic" frequency ν(syn) ∝ (ν1 - ε12ν2) largely immune to the blackbody radiation shift. For example, in the case of 171Yb+ it is possible to create a synthetic-frequency-based clock in which the fractional blackbody radiation shift can be suppressed to the level of 10(-18) in a broad interval near room temperature (300±15 K). We also propose a realization of our method with the use of an optical frequency comb generator stabilized to both frequencies ν1 and ν2, where the frequency ν(syn) is generated as one of the components of the comb spectrum.     

On some relations for the inverse blackbody radiation problem

Some relations between the area-temperature distribution of a blackbody and its radiated power spectrum are derived. These relations shall be useful in verifying the adequacy and the accuracy of the various procedures recently developed for the numerical solution of the inverse blackbody radiation problem.     

Generalization of the radiation laws of a Kerr nonlinear blackbody

Within the framework of nonextensive statistical mechanics (NSM), we generalize the radiation laws, which include the Planck radiation law and Stefan-Boltzmann law, of a Kerr nonlinear blackbody (KNB) in the normalized form. In order to illustrate the influence of the parameter q on the two generalized radiation laws, we make a numerical calculation of the two laws under appropriate conditions. Furthermore, we make an attempt to extend the theory of KNB to the whole Universe.     

Breakdown of the Planck blackbody radiation law at nanoscale gaps

The Planck theory of blackbody radiation imposes a limit on the maximum radiative transfer between two objects at given temperatures. When the two objects are close enough, near-field effects due to tunneling of evanescent waves lead to enhancement of radiative transfer above the Planck limit. When the objects can support electromagnetic surface polaritons, the enhancement can be a few orders-of-magnitude larger than the blackbody limit. In this paper, we summarize our recent measurements of radiative transfer between two parallel silica surfaces and between a silica microsphere and a flat silica surface that show unambiguous evidence of enhancement of radiative transfer due to near-field effects above the Planck limit.     

Analogy between first-order phase transitions and blackbody radiation

The analogy between blackbody radiation and a phase equilibrium between vapor and liquid is drawn by deriving the Clapeyron equation in which the two probability distributions of blackbody radiation play the role of the two phases. The pressure of one of these distributions, which becomes negative at sufficiently high photon energies, is analogous to a negative pressure tending to break up a liquid. A similar type of critical phenomenon should be observed for blackbody radiation.     

Statistical properties of thermal radiation in a Kerr nonlinear blackbody

We study the statistical properties of thermal radiation in a Kerr nonlinear blackbody in which bare photons with opposite wave vectors and helities are bound into pairs and unpaired photons are transformed into a different kind of quasiparticle, the nonpolariton. This paper investigates the statistical properties of the photon blackbody field by using the second-order correlation function, the phase space distribution function, the photon number distribution and the nonclassical depth. The numerical computation and a discussion of the results are present.     

Analysis of rectangular resonant cavities in terahertz parallel-plate waveguides

We describe an experimental and theoretical characterization of rectangular resonant cavities integrated into parallel-plate waveguides, using terahertz pulses. When the waveguide is excited with the lowest-order transverse-electric mode, these cavities exhibit resonances with narrow linewidths. Broadband transmission spectra are compared with the results of mode-matching calculations, for various cavity dimensions.