An experiment on the Purcell effect in a wedge cavity

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An excited atom spontaneously emitting in a cavity of nanoscale dimensions is known to exhibit the Purcell effect in that it experiences quantifiable changes in its emission rate relative to that in free space. For cavity dimensions below half a radiation wavelength the emission rate is completely suppressed. Although it is generally understood that spontaneous emission by atoms is a quantum mechanical effect, we describe here an experiment showing that the Purcell effect is also exhibited by a classical dipole radiating at wavelengths of the order of a few centimetres inside a wedge-shaped cavity, a scaling up in dimensions by about five orders of magnitude. We highlight the limitations of such an experiment and suggest improvements. Results for the fractional radiated power from a dipole antenna shows a strong dependence on the dipole orientation, as well as the angle of the cavity wedge. We also discuss using an impedance model programme to account for the finiteness of the dipole length in order to explain the differences between the predictions of the quantum theory and this classical experiment, which can be set up and performed in an undergraduate laboratory.

Original languageEnglish
Pages (from-to)S81-S88
Number of pages8
JournalEuropean Journal of Physics
Issue number4
Publication statusPublished - Jul 2009

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