Controlling the interaction of photons and single molecules in a λ/2-microresonator

Optical microresonators are structures which confine light to a small region in the range of one wavelength. A practical design for a single-mode microresonator is formed by two silver mirrors enclosing a transparent dielectric medium with single quantum emitters. The radiation of a quantum emitter is coupled to cavity resonances which leads to an optical confinement of the broadband fluorescence. Using a tunable microresonator, we were able to actively change the optical properties of an embedded single molecule. The radiative coupling of the emitter to the electromagnetic field is also determined by the orientation of its transition dipole moment with respect to the cavity normal. We describe here a method to determine the 3D-orientation and position of quantum emitters embedded in the microresonator. In addition, this method can be used to detect the longitudinal position of a fluorescent bead in the microresonator with an accuracy of a few nanometers. We will also present first experiments on Förster Resonance Energy Transfer (FRET) control on the DsRed protein system in a microresonator.