Abstract

Tunneling ionization and harmonic generation in two-color fields were studied using a fundamental beam (ωw) and its harmonies (2ωw, 3ωw) generated by a 100-fs Ti:sapphire laser. Ion yields of atoms and molecules were successfully controlled by changing the relative phase between ωw and 3ωw pulses. Adding the third harmonic with an intensity of only 10% enhances the ion yield by a factor of 7. Two-color interference was clearly observed in photoelectron spectra and harmonic spectra. The intensities of high-order harmonics in the plateau region are enhanced by an order of magnitude[1]. In the ωw-2ωw field, even-order harmonics were observed in He with the intensity almost equal to the odd harmonics due to an asymmetric optical field as shown in Fig. 1.

© 1996 Optical Society of America