10:45 AM - 11:00 AM
▼ [18a-Z18-7] Self-induced nonlinearity modulates the THz waveform generated by the two-color laser filament
Keywords:terahertz, nonlinear optics, laser filament
Pulsed laser-induced filaments by focused infrared fundamental wave and its second harmonic is one of the most powerful benchtop sources of terahertz (THz) pulsed radiation. This promising tool has stimulated a series of studies in both basic and application aspects. The asymmetric transient current model successfully explains the theoretical principles of the two-color excitation scheme. However, the nonlinear effects in the filament associated with changes of the refractive index when the pulse propagates through optical media have not been studied in depth. We observed the two-color laser filament emitted THz waveform variated with the incident IR pulse energy by air biased coherent detection (ABCD) method. This phenomenon can be considered as the self-phase modulation caused by free electrons in the laser filament which reshapes the two-color light envelope. The result improves our understanding of the complex nonlinear process in the filament for further correction of the THz generation model.