Generation of extreme ultraviolet tunable frequencies from mixed fields

The generation of harmonics from two mixed laser fields of noncommensurate frequencies is analyzed. We address the case of the hydrogen atom irradiate d both by a laser field of wavelength lambda(0) = 1231 nm with an intensity I-0 = 4 x 10(13) W cm(-2) and by a tunable laser held of wavelength approx imately lambda(1) = 2071 nm with an intensity I-1 much less than I-0. We st udy the temporal profile and the efficiency of two-color harmonic generatio n far from the saturation regime. me focus on situations in which an even n umber of photons omega(0) are absorbed in association with the emission or absorption of one photon ol of the second laser. The influence of the secon d laser on the production of the main harmonic spectrum is also analyzed. ( C) 1999 Optical Society of America [S0740-3224(99)03110-0].