Self-Referenced Measurement of Light Waves

The wave nature of light has been known for more than 100 years. However, it is still very difficult to directly sample an optical field transient on a time scale below the oscillation period. It has been naturally believed that the field oscillation can be detected only by using a reference pulse that has a shorter duration than the period of the oscillation. In this Letter, an experimental demonstration of a self-referenced light wave measurement is shown. Frequency-resolved optical gating capable of carrier-envelope phase determination was used to measure the complete electric field evolution of a 21-fs few-cycle pulse without any reference pulses. A second harmonic generation frequency-resolved optical gating spectrogram and an interferogram between second harmonic and self-diffraction signals were simultaneously recorded. The phase-controlled light waves of few-cycle pulses were clearly observed by using this method.