  Stimulated Emission Depletion (STED) microscopy has emerged as a powerful
technique providing visualization of biological structures at the molecular
level in living samples. In this technique, the diffraction limit is broken by
selectively depleting the fluorophore's excited state by stimulated emission,
typically using a donut-shaped optical vortex beam. STED microscopy performs
unrivalably well in degraded optical conditions such as living tissues.
Nevertheless, photo-bleaching and acquisition time are among the main
challenges for imaging large volumetric field of views. In this regard, random
light beams like speckle patterns have proved to be especially promising for
three-dimensional imaging in compressed sensing schemes. Taking advantage of
the high spatial density of intrisic optical vortices in speckles -- the most
commonly used beam spatial structure used in STED microscopy -- we propose here
a novel scheme consisting in performing STED microscopy using speckles. Two
speckle patterns are generated at the excitation and the depletion wavelengths,
respectively, exhibiting inverted intensity contrasts. We illustrate spatial
resolution enhancement using complementary speckles as excitation and depletion
beam on both fluorescent beads and biological samples. Our results establish a
robust method for super-resolved three-dimensional imaging with promising
perspectives in terms of temporal resolution and photobleaching.
