Second Quantization of Light
In this chapter we discuss the quantization of electromagnetic waves, which we also denoted as light (visible or invisible to human eyes). After reviewing classical and quantum properties of the light in the vacuum, we discuss the so-called second quantization of the light field showing that this electromagnetic field can be expressed as a infinite sum of harmonic oscillators. These oscillators, which describe the possible frequencies of the radiation field, are quantized by introducing creation and annihilation operators acting on the Fock space of number representation. We analyze the Fock states of the radiation field and compare them with the coherent states. Finally, we consider two enlightening applications: the Casimir effect and the radiation field at finite temperature.