Third and fifth harmonics generation by tightly focused femtosecond   pulses at 2.2 {\mu}m wavelength in air
  We report experiments on the generation of third and fifth harmonics of millijoule-level, tightly focused, femtosecond laser pulses at 2.2 {\mu}m wavelength in air. The measured ratio of yields of the third and fifth harmonics in our setup is about 2 \cdot 10-4. This result contradicts the recent suggestion that the Kerr effect in air saturates and changes sign in ultra-intense optical fields. 
Gombojav O. Ariunbold, Pavel Polynkin, and Jerome V. Moloney
physics.optics