We investigate the ultrafast carrier dynamics in a ZnO crystal irradiated by a strong, linearly polarized midinfrared laser pulse. Depending on the laser intensity, there exist two dominant light wave-driven processes, i.e., the electron-hole collision recombination and the electron-electron impact excitation. The corresponding optical signatures are high-order harmonic generation and stimulated emission, respectively. By adding a weak infrared or telecom wavelength laser pulse with an orthogonal polarization, we show that these two carrier dynamic processes can be effectively controlled by tuning the time delay between the two laser pulses. This all-optical control has an ultrafast speed, a low threshold, and a broad spectral responsiveness, which have implications in understanding the ultrafast carrier dynamics in the condensed matter and the design of next-generation optoelectronic switches.

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• Carrier generation & recombination
• Excitons
• Semiconductors
• High-harmonic generation
• Infrared spectroscopy
• Photoluminescence