Chapter 4. Phenomena Involving Absorption of Light and Energy Transfer

J. C. del Toro Iniesta

“El clero era absorbente”. Sobre todo Don Fermín había sido un poco jesuita. —Leopoldo Alas, Clarín, 1885. ‘The clergy were like a sponge.’ And what was more, Don Fermin had once been something of a Jesuit. So far we have avoided detailed discussion about two physical phenomena that are crucial in the context of this book and for any understanding of the interaction between matter and radiation in general. These two phenomena are absorption and dispersion, that is, the removal of energy from the electromagnetic field by matter and the dephasing of the electric field components as light streams through the medium. Although we have barely mentioned the existence of these effects, we shall need a deeper insight into both of them. We shall see that retardance, birefringence, and absorption properties of polarization systems, assumed in the preceding sections, are based on these phenomena, whose wavelength dependence is understood in terms of the wavelength dependence of the dielectric permittivity and, hence, of the refractive index of the medium. By studying absorption and dispersion we are producing the necessary bricks with which to build a theory of radiative energy transfer which will be discussed in following chapters. We shall continue to assume unit isotropic magnetic permeability of μ = 1 for the medium. Certainly, a full account of absorption and dispersion processes can be carried out only within the framework of quantum mechanics.

Hans Joachim Eichler, Jürgen Eichler, Oliver Lux

Hai-Ning Ye, Bao-Fei Wan, Haifeng Zhang

The nonreciprocal and polarization-sensitive performances of analog of electromagnetically induced absorption (EIA-like) and electromagnetically induced transparency (EIT-like) effects are investigated by the transfer matrix method (TMM), and the layered topology metastructure containing microwave magnetized plasma is used to construct suitable bright resonators, dark resonators, and quasi-dark resonators. In the case of low frequencies, the incident TM wave fosters an evident nonreciprocal EIA-like effect, and its nonreciprocal absorptivity is higher than 0.8, while the EIA-like phenomenon fails to occur in the case of the incident TE wave. For the case of high-frequency incidence, the EIT-like and EIA-like effects can be switched by converting the TM wave into the TE one under the case of backward propagation, and the maximum nonreciprocal absorptivity can exceed 0.9 if the TE wave propagates. The effects of some critical variables such as incident angle, plasma frequency, plasma cyclotron frequency, and plasma layer thickness on nonreciprocal and polarization-sensitive characteristics have been explored, and the slow light property of the EIT-like effect has also been briefly involved, and its group refractive index can reach 1224. The energy level transition theory and the optimized two-oscillator model are also analyzed to explain the generation of EIA-like and EIT-like phenomena in depth. We hope that the relevant phenomena will be interesting for slow light devices, two-way communication of electromagnetic waves, and polarization separation devices.