Rabi Oscillations for High Resolution Microscopy on Single Molecules

Wednesday, March 17, 2010 -
4:00pm to 5:00pm
Ilja Gerhardt
Speaker's Institution: 
ETH Zurich


Single dye molecules at cryogenic temperatures exhibit many spectroscopic phenomena known from the study of free atoms and are thus promising candidates for experiments in fundamental quantum optics. However, the past techniques for their detection have either sacrificed information on the coherence of the excited state or have been inefficient. We are able to show that these problems can be addressed by focusing the excitation light near to the extinction cross-section of a molecule.

By short optical pulses we can prepare a single quantum system in a well defined state. Two methods to detect this highly non-linear feature are introduced. These rely on time correlated single photon counting and on detecting the integrated Stokes-shifted signal. On a single molecule we are able to observe up to 5 Rabi flops. A $\pi$-pulse excitation was demonstrated with merely 500 photons [1].  Since the coherent state preparation is highly dependent on the specific excitation strength, it is possible to optimize the position of the excitation laser exactly onto the observed single emitter. This high non-linear feature can be used for high resolution microscopy.

Higher spatial frequencies in the resulting images allow superior localization accuracy with less detected photons in a shorter time. By Monte Carlo simulations we gain interesting insights on the parameters influencing the localization accuracy.

[1] I. Gerhardt, G. Wrigge, G. Zumofen, J. Hwang, A. Renn, V. Sandoghdar, Coherent state preparation and observation of Rabi oscillations in a single molecule, Physical Review A, 2009, 79, 4