Abstract

In the field of optical imaging, diffraction limit is one of the most serious barriers that limit the spatial resolution to roughly half of wavelength. It was not until last decade had the diffraction limit been broken and from then on, super-resolution microscopy has generated strong impact to biological and material researches. Among these techniques, stimulated emission depletion (STED) microscopy is arguably the most successful one, which reaches super-resolution by turning fluorophores on and off with stimulated emission process. This technique needs two beams: a short-wavelength beam with solid shape to excite the fluorophore and a long-wavelength beam with doughnut shape to suppress spontaneous fluorescence via STED. As a result, spontaneous fluorescence is only allowed in the central region of the doughnut-shaped beam, and therefore resolution can be effectively improved. The higher the STED beam intensity, the better the resolution can be enhanced. However, the fluorophores need extraordinary photostability to sustain strong depletion beam as well as repeated excitation and depletion.

© 2014 Japan Society of Applied Physics, Optical Society of America