Seminário de Óptica será na terça-feira (2) no Departamento de Física
O seminário será apresentado pela pós-doutoranda no DF Michelle Araújo
“Super-and subradiance in a dilute cloud of cold atoms” é o tema do Seminário de Óptica da próxima terça-feira (2). O evento será às 14h, no auditório do Departamento de Física, no Centro de Ciências Exatas e da Natureza (CCEN), no Campus Recife da UFPE. O seminário será apresentado pela pós-doutoranda no Departamento de Física Michelle Araújo. Apesar de a pesquisa ter sido escrita em inglês, o seminário será realizado em português.
The problem of the interaction of N atoms with a laser beam and vacuum modes gives rise to many interesting phenomena concerning the spontaneous emission of light and its propagation in the medium. Cooperative effects, like super- and subradiance, are related to the coherence created between atoms when a photon is emitted spontaneously by a single excited atom. Superradiance is the enhancement of the spontaneous emission due to constructive interference of the scattered light, while subradiance is the trapping of some remaining light due to destructive interference. In cold atoms, theoretical works describe these two cooperative effects in a large and diluted atomic cloud, in the regime of low intensities and large detunings of the incident laser. The experiment consists in measuring the super- and subradiant decay rates from the temporal emitted intensity after switching off of the incident laser in the steady state using a magneto-optical trap of 87Rb atoms at large resonant optical thicknesses. A probe beam excites the atoms close to the D2 line. In this work, we report the experimental observation of super- and subradiance in a large cloud of cold atoms. For subradiance, the main result is the linear evolution of the characteristic time with the resonant optical thickness of the cloud and its independence of the detuning. For superradiance, it is observed out of the forward direction. We discuss the interplay of subradiance and radiation trapping, as well as theoretical predictions for a setup of a phased cloud, to control the subradiant amplitude emission, and temperature effects, where subradiance is shown to be robust in a large range of temperatures.
Departamento de Física