  Nanoscale semiconductor lasers have been developed recently using either
metal, metallo-dielectric or photonic crystal nanocavities. While the
technology of nanolasers is steadily being deployed, their expected performance
for on-chip optical interconnects is still largely unknown due to a limited
understanding of some of their key features. Specifically, as the cavity size
is reduced with respect to the emission wavelength, the stimulated and the
spontaneous emission rates are modified, which is known as the Purcell effect
in the context of cavity quantum electrodynamics. This effect is expected to
have a major impact in the 'threshold-less' behavior of nanolasers and in their
modulation speed, but its role is poorly understood in practical laser
structures, characterized by significant homogeneous and inhomogeneous
broadening and by a complex spatial distribution of the active material and
cavity field. In this work, we investigate the role of Purcell effect in the
stimulated and spontaneous emission rates of semiconductor lasers taking into
account the carriers' spatial distribution in the volume of the active region
over a wide range of cavity dimensions and emitter/cavity linewidths, enabling
the detailed modeling of the static and dynamic characteristics of either
micro- or nano-scale lasers using single-mode rate-equations analysis. The
ultimate limits of scaling down these nanoscale light sources in terms of
Purcell enhancement and modulation speed are also discussed showing that the
ultrafast modulation properties predicted in nanolasers are a direct
consequence of the enhancement of the stimulated emission rate via reduction of
the mode volume.
