Time-Resolved Dynamics of Semiconductor Nanolaser via Four-Wave Mixing Gating

We experimentally demonstrate the direct time-domain characterization of photonic-crystal nanolasers at telecom wavelengths using a nonlinear optical gating technique based on four-wave mixing. This approach enables the temporal characterization of the ultrafast emission dynamics under short-pulse excitation with a picosecond time resolution. When a weak continuous-wave component is added to the pulsed pump, the emission becomes less sensitive to spontaneous-emission noise, resulting in a significantly reduced buildup time. The difference between purely pulsed and hybrid excitation regimes points to the influence of pulse-to-pulse timing fluctuations. To elucidate this effect, we perform Langevin-based simulations that reproduce the experimentally observed broadening and confirm that time jitter, originating from spontaneous emission noise near threshold, dominates the temporal dispersion. These results establish four-wave mixing gating as a powerful method to probe nanolaser dynamics with picosecond precision.