  Three-dimensional direct laser writing has become a well established,
versatile, widespread, and even readily commercially available "workhorse" of
nano- and micro-technology. However, its lateral and axial spatial resolution
is inherently governed by Abbe's diffraction limitation - analogous to optical
microscopy. In microscopy, stimulated-emission-depletion approaches have lately
circumvented Abbe's barrier and lateral resolutions down to 5.6 nm using
visible light have been achieved. In this paper, after very briefly reviewing
our previous efforts with respect to translating this success in optical
microscopy to optical lithography, we present our latest results regarding
resolution improvement in the lateral as well as in the much more relevant
axial direction. The structures presented in this paper set a new
resolution-benchmark for next-generation direct-laser-writing optical
lithography. In particular, we break the lateral and the axial Abbe criterion
for the first time.
