  Nanowire lasers can be monolithically and site-selectively integrated onto
silicon photonic circuits. To assess their full potential for ultrafast
opto-electronic devices, a detailed understanding of their lasing dynamics is
crucial. However, the roles played by their resonator geometry and the
microscopic processes that mediate energy exchange between the photonic,
electronic, and phononic subsystems are largely unexplored. Here, we study the
dynamics of GaAs-AlGaAs core-shell nanowire lasers at cryogenic temperatures
using a combined experimental and theoretical approach. Our results indicate
that these NW lasers exhibit sustained intensity oscillations with frequencies
ranging from 160 GHz to 260 GHz. As the underlying physical mechanism, we
identified self-induced electron-hole plasma temperature oscillations resulting
from a dynamic competition between photoinduced carrier heating and cooling via
phonon scattering. These dynamics are intimately linked to the strong
interaction between the lasing mode and the gain material, which arises from
the wavelength-scale dimensions of these lasers. We anticipate that our results
could lead to new approaches for ultrafast intensity and phase modulation of
chip-integrated nanoscale semiconductor lasers.
