Flutuações do vácuo quântico a temperatura finita na propagação da luz em meios óticos não lineares.

Abstract

In this dissertation, we will study the effects of quantum and thermal fluctuations in dielectric material media. The basic idea here will be to consider a pulse of light, called a probe pulse, passing through a sample of dielectric material. In this case, we will use Cadmiun Selenide (CdSe). Material nonlinearities will be activated by a background electric field E0

. The classic result says that this pulse will cross the sample of length (d) in a certain time of flight (t). However, when quantized, E0 will suffer the effects of quantum fluctuations, the so-called vacuum fluctuations. We will show that such fluctuations will alter the time of flight of the probe pulse in the sample. To do so, we will calculate the fractional variance for the flight time, and for a sample of CdSe of approximately 10μm it will be approximately 10−8

. Such a result could, in principle, be measured in the laboratory. However, in a real physical experiment, fluctuations of thermal origin are also present and they will influence the result described above. Therefore, we will also consider the effects that thermal fluctuations have on E0 and then we will see how they will affect the flight time of the probe pulse that passes through the CdSe sample. In particular, we find that for a temperature T < 46K, quantum vacuum fluctuations are dominant over fluctuations of thermal origin. To perform such calculations, we consider terms of up to second order in the susceptibilities of the CdSe sample, since it is from these terms that the nonlinearities appear. We also consider a test function, which, from a practical point of view, regularizes divergent integrals that will appear in the course of the dissertation and from a physical point of view, models the geometry of the dielectric.