The generation of frequency upshifted, pressure-tunable third-harmonic pulses during ultrafast ionization of subatmospheric noble gases at peak intensity 1016 W/cm2 is reported. Pressure tuning of the power spectrum centroid over the range 10−5 ≲ Δω/ω ≲ 10−1, corresponding to a pressure range of 0.1 ≲ p ≲ 700 Torr, is demonstrated. We also demonstrate that the blue-shifted portions of both the 3ω and the ω pulses are preferentially self-guided in a limited pressure range (10 ≲ p ≲ 500 Torr), which is key to separating the pressure-tunable component of the harmonic from nontunable harmonic generated by means of atomic nonlinearities.
© 1996 Optical Society of America
C. W. Siders, N. C. Turner, M. C. Downer, A. Babine, A. Stepanov, and A. M. Sergeev, "Blue-shifted third-harmonic generation and correlated self-guiding during ultrafast barrier suppression ionization of subatmospheric density noble gases," J. Opt. Soc. Am. B 13, 330-335 (1996)