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.
We have studied the intensity correlations between two orthogonally linearly polarized components of a laser field propagating through a resonant atomic medium. These experiments have been performed in a Rubidium atomic vapor. We observe that the correlations between the orthogonally polarized components of the laser beam are maximal in the absence of a magnetic field. The magnitude of the correlations depends on the applied magnetic field, and the magnitude first decreases and then increases with increasing magnetic field. Minimal correlations and maximal rotation angles are observed at the same magnetic fields. The width of the correlation function is directly proportional to the excited state lifetime and inversely proportional to the Rabi frequency of laser field. These results can be useful for improving optical magnetometers and for optical field or atomic spin squeezing.
