Spectral compression and frequency tuning of femtosecond pulses by second harmonic generation

We propose and experimentally demonstrate a new, aberration-free method of pulse spectral compression, based on second harmonic generation. The technique is self-reference by the use of a nonlinear-spectronic reference pulse self-shaped in a single-mode fiber without gain. As compared with the traditional spectral compression, the proposed method is free of demand to separate the reference and signal radiation by frequency or polarization.