Quantum optics physical properties

The luminescence of small particles, especially of semiconductors, is a fascinating development in the field of physical chemistry, although it is too early to evaluate the potential of these particles for applications. The essential point is that the physical properties of small semiconductor particles are different from the bulk properties and from the molecular properties. It is generally observed that the optical absorption edge shifts to the blue if the semiconductor particle size decreases. This is ascribed to the quantum size effect. This is most easily understood from the electron-in-a-box model. Due to their spatial confinement the kinetic energy of the electrons increases. This results in a larger band gap (84). 

Recently in the field of physics of semiconductors and materials science a great attention has been paid to formation and optical properties of semiconductor nanocrystals (quantum dots, QDs) dispersed in inorganic matrixes. An interest to glassy materials with QDs is associated with their unique physical properties and possibility to create elements of optoelectronic devices. Phase separation processes followed by crystallization are the basic in production of such materials. They result in formation of semiconductor nanocrystals stabilized within a glass matrix. The materials are advanced for various applications because of optical and thermal stability and possibility to control optical features through the technology of glass preparation and post-synthesis thermal treatment. 

The subject of quantum optics is concerned with the quantum properties of the radiation field, i.e. the properties of photons. Since the word multiphoton has been used, it might seem that strong laser fields are in some way relevant to quantum optics. However, the word multiphoton is something of a misnomer in the strong field regime. In fact, if very many photons are involved, quantisation of the radiation field is more or less irrelevant the intense, coherent laser pulse tends to a quasiclassical beam of light. Indeed, it has been pointed out by several authors [483] that the use of the word photon in the context of laser physics is of questionable validity. 

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