A method and system generates two synchronized trains of laser pulses at different wavelengths, wherein the two pulse trains are temporally synchronized and have a stable phase relation, and wherein the wavelength of one of the pulse trains is de-tunable. The method includes the steps of: generating a train of ultra-short seed laser pulses; splitting the train of seed laser pulses into a first pulse train and a second pulse train; and frequency-shifting the first pulse train by soliton self-frequency shift in an optically pumped waveguide having anomalous dispersion, wherein the spectrum of the frequency-shifted first pulse train is de-tunable by varying the pump power.