Stimulated Emission Depletion (STED) Microscopy is a far-field laser scanning microscopy technique able to provide resolution below the diffraciton limit. The technique was invented by Stefan Hell1 and pioneered by his Nanobiophotonics research group at the Max-Planck Institute for Biophysical Chemistry at Göttingen in Germany. Their website contains many useful publications and resources for super-resolved microscopy techniques, including STED.
In the Photonics Group we are working to develop STED microscopes for biological and other applications including the study of the immunological synapse (with Dan Davis' group) and nitrogen vacancy defects in diamond (with the Diamond Trading Company). Our approach has been to develop versatile implementations of STED and we were the first group to report STED using a femtosecond Ti:Sapphire laser pumped supercontinuum to provide tunable excitation pulses inherently synchronised with the Ti:Sapphire laser radiation being used as the depletion beam2. In this paper we also reported the first combination of STED microscopy with fluorescence lifetime imaging, observing that the early part of the detected fluorescence sigal was not super-resolved and so using the time-resolved detection to gate the later super-resolved fluorescence signal for our STED images.
To generate the required spatial profile ("doughnut" mode) for the depletion beam we employed a programmable spatial light modulator (SLM) with which we were also able to correct for aberrations induced by propgation through the opticl elements of the microscope and the sample.
1 Breaking the diffraction resolution limit by stimulated emission: stimulated-emission-depletion fluorescence microscopy, S. W. Hell, and J. Wichmann, Opt. Lett. 19, (1994) 780-782
2 Stimulated emission depletion microscopy with a supercontinuum source and fluorescence lifetime imaging, E. Auksorius, B. R. Boruah, C. Dunsby, P. M. P. Lanigan, G. Kennedy, M. A. A. Neil and P. M. W. French, Opt Lett 33 (2008) 113-115