Poynting vector field lines

Figure 2. The FDTD simulation results for the electric field components Ex (a) and (c) and the Poynting vector component (h) and Sx (d). The waveguide is along z axis, the dashed lines contouring the non-etched 0.6 pm thick region of the core.

At energies on either side of 8.8 eV a small aluminum sphere presents a much smaller target to incident photons. At 5 eV, for example, the absorption efficiency of a sphere with x = 0.3 is about 0.1 as far as absorption is concerned, the sphere is much smaller than its geometrical cross-sectional area. The field lines of the Poynting vector, shown in Fig. 12.46, are what are to be... 

Figure 12.4 Field lines of the total Poynting vector (excluding that scattered) around a small aluminum sphere illuminated by light of energy 8.8 eV (a) and 5 eV (b). The dashed vertical line in (a) indicates the effective radius of the sphere for absorption of light.

The imaginary part of the dielectric function of SiC at its Frohlich frequency in the infrared (about 932 cm- ) is close to that of aluminum at 8.8 eV. So Fig. 2Aa also shows the field lines of the Poynting vector around a small SiC sphere illuminated by light of frequency 932 cm-1. At nearby frequencies, 900... 

From the transmission line approximation for the current distribution, the far electric fields can be computed. From this the Poynting vector, (watts per square meter), can be integrated over a large spherical surface to find the total radiated power. The radiation resistance at the feed point is then found from this radiated power and the known current at the feed point. The near fields dictate the imaginary part of the impedance. Some typical values of radiation resistance for various elements, which have small diameter, are given in Table 13.1. The section on dipole characteristics gives the input impedance of dipoles of various lengths computed from the latest moment method formulation described in Sec. 13.1.4. 

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