  In this article, we introduce the concept of a dielectric nanolaser that is
nanoscopic in all spatial dimensions. Our proposal is based on dielectric
nanoparticles of high refractive index, e.g., silicon, acting as a (passive)
cavity (without intrinsic gain) that is decorated with a thin film of organic
gain media. Its resonance frequencies can be tuned over the entire visible
range and bright and dark modes can be addressed. So called "magnetic" modes
can be utilized, which makes this dielectric nanolaser a complementary source
of coherent nearfields similar to the surface plasmon laser (which exploits
electric modes). The small intrinsic losses in silicon yield relatively high
quality factors and low non-radiative decay rates of emitters close to the
cavity, both of which will lead to low thresholds. As we show in this work, the
dielectric nanolaser exhibits certain advantages relative to nanowire lasers
and spasers, such as reduced laser threshold, short switch-on times, size and
design flexibility. The dielectric nanolaser is compatible with standard
lithographic fabrication approaches and its relative simple design may allow
for easy testing and realization of the concept. Thus, the silicon nanolaser
might soon find many applications in nanooptics and metamaterials.
