Noncollinear six-wave mixing of femtosecond laser pulses in air

摘要

Noncollinear six-wave mixing of femtosecond light pulses in air by two crossed laser beams has been demonstrated. It was shown that within a wide range of laser intensities this process leads to efficient third-order-harmonic generation, which indicates the importance of higher-order optical nonlinearities in intense light-matter interactions. A direct comparison of the experiment and theory allowed us to estimate unambiguously the magnitude of the quintic optical nonlinearity χxyyyyx(5)(-3ω;ω,ω,ω, ω,-ω) of air as 2×10-49 (m/V)4. We expect that this technique could be useful for multiphoton spectroscopy and laser frequency conversion, as well as for ultrashort light-pulse characterization and verification of theoretical models describing propagation of powerful laser pulses in gaseous media.