论文标题
球体的热发射的空间连贯性
Spatial Coherence of Thermal Emission by a Sphere
论文作者
论文摘要
提出了用于计算通过任意大小和材料的均匀的等温球来计算热发射能量密度和空间相关功能的分析表达式。在近场和远场状态下，研究了碳化硅，硅，硅和钨球的光谱分布和控制距离能量密度的各种尺寸参数的近场和钨球，x = 0.002至5。能量密度遵循所有尺寸和材料的远场中d^-2（d是观察距离）的功率定律。近场的功率定律很大程度上取决于材料，大小参数和比率d/a（a是球半径）。在近场，当x << 1和d/a >> 1（类似于电点偶极子）时，能量密度遵循D^-6的幂定律。随着X或D/A的增加，多物对能量密度的贡献会增加，导致D的功率增加，直到幂定律收敛到半侵入培养基为止。径向方向的空间相关长度在$λ$，0.1 $λ$和0.001 $λ$的订单中，分别为远场，近场和极端近距离。极端近场的相关角度很大程度上取决于球体大小参数，因此当X从0.002增加到5时，它降低了三个数量级（从0.5 $π$到0.001 $π$）。虽然偶极局部表面声子（LSPHS）的激发不会影响相关长度和角度，但多极LSPHS降低了两个方向上的空间相干性。
Analytical expressions for calculating the energy density and spatial correlation function of thermal emission by a homogeneous, isothermal sphere of arbitrary size and material are presented. The spectral distribution and the power law governing the distance-dependent energy density are investigated in the near-field and far-field regimes for silicon carbide, silicon and tungsten spheres of various size parameters ranging from X = 0.002 to 5. The spatial coherence of thermal field emitted by spheres is also studied in both radial and polar directions. The energy density follows a power law of d^-2 (d is the observation distance) in the far field for all sizes and materials. The power law in the near field is strongly dependent on the material, size parameter, and the ratio d/a (a is the sphere radius). In the near field, the energy density follows a power law of d^-6 when X<<1 and d/a>>1 (similar to an electric point dipole). With increasing X or decreasing d/a, the contribution of multipoles to the energy density increases resulting in an increase in the power of d until the power law converges to that for a semi-infinite medium. The spatial correlation length in the radial direction is in the orders of $λ$, 0.1$λ$, and 0.001$λ$ in the far field, intermediate near field, and extreme near field, respectively. The correlation angle in the extreme near field is strongly dependent on the sphere size parameter, such that it decreases by three orders of magnitude (from 0.5$π$ to 0.001$π$) when X increases from 0.002 to 5. In the intermediate near field and far field, the correlation angle retains the same order of magnitude (0.15$π$ - 0.7$π$) for all considered Xs. While the excitation of dipolar localized surface phonons (LSPhs) does not affect the correlation length and angle, the multipolar LSPhs reduce the spatial coherence in both directions.
