Overview of Linear Optical Effects
If an electromagnetic wave, or a photon, hits atoms or molecules of a material, these particles can react in two distinct ways. If the photons were absorbed, an excitation of the particles onto a higher energy level is the result. In this case the band gap of the material is smaller or equal to the energy of the photons (ħω). After the absorption, the excitation of the atom can decay in many different ways. The most important, in the context of optical telecommunications, is the spontaneous emission; in this case the material emits on its part photons with a different energy. This spontaneous emission can in some materials be transmuted into a stimulated emission and is the basis of lasers and the erbium-doped fiber amplifier (EDFA).
KeywordsPermeability Vortex Hydroxyl Attenuation Recombination
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