Waveform-controlled Terahertz (THz) radiation is of great importance due toits potential application in THz sensing and coherent control of quantumsystems. We demonstrated a novel scheme to generate waveform-controlled THzradiation from air plasma produced when carrier-envelope-phase (CEP) stabilizedfew-cycle laser pulses undergo filamentation in ambient air. We launchedCEP-stabilized 10 fs-long (~ 1.7 optical cycles) laser pulses at 1.8 {\mu}minto air and found that the generated THz waveform can be controlled by varyingthe filament length and the CEP of driving laser pulses. Calculations using thephotocurrent model and including the propagation effects well reproduce theexperimental results, and the origins of various phase shifts in the filamentare elucidated.
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