Phase-locked ultrashort pulse trains at separate and independently tunable wavelengths.

The generation and characterization of femtosecond pulses at three independently tunable visible wavelengths is reported. Selected spectral portions of a common continuum generated in sapphire are amplified in noncollinear optical parametric amplifiers. The phase relation of the pulse trains is analyzed with a nonlinear interferometer based on coherent anti-Stokes Raman scattering and is found to be locked to better than 250?mrad rms. Small spectral shifts of the pulses lead to interference behavior that is consistent with 1?kHz frequency combs.