Microcavities: tailoring the optical properties of single quantum emitters.

We present a general review of different microresonator structures and how they can be used in future device applications in modern analytical methods by tailoring the optical properties of single quantum emitters. The main emphasis is on the tunable lambda/2-Fabry-Perot-type microresonator which we used to obtain the results presented in this article. By varying the mirror distance the local mode structure of the electromagnetic field is altered and thus the radiative coupling of fluorescent single quantum emitters embedded inside the resonator to that field is changed, too. As a result a modification of the optical properties of these quantum emitters can be observed. We present experimental as well as theoretical results illustrating this effect. Furthermore, the developed resonator can be used to determine the longitudinal position of embedded emitters with an accuracy of lambda/60 by analyzing the excitation patterns of nano-sized fluorescent polymer spheres after excitation with a radially polarized doughnut mode laser beam. Finally, we will apply this resonator to a biological system and demonstrate the modification of Förster resonant energy transfer (FRET) efficiency by inhibiting the excited state energy transfer from the donor to the acceptor chromophore of a single DsRed protein.