  Integration of optical interconnects with silicon-based electronics can
address the growing limitations facing chip-scale data transport as
microprocessors become progressively faster. However, material lattice mismatch
and incompatible growth temperatures have fundamentally limited monolithic
integration of lasers onto silicon substrates until now. Here, we use a novel
growth scheme to overcome this roadblock and directly grow on-chip InGaAs
nanopillar lasers, demonstrating the potency of bottom-up nano-optoelectronic
integration. Unique helically-propagating cavity modes are employed to strongly
confine light within subwavelength nanopillars despite low refractive index
contrast between InGaAs and silicon. These modes thereby provide an avenue for
engineering on-chip nanophotonic devices such as lasers. Nanopillar lasers are
as-grown on silicon, offer tiny footprints and scalability, and are thereby
particularly suited to high-density optoelectronics. They may ultimately form
the basis of the missing monolithic light sources needed to bridge the existing
gap between photonic and electronic circuits.
