Spectral phase measurements for broad Raman sidebands by using spectral interferometry.

We report a method of spectral phase measurement for a femtosecond pulse train composed of a discrete Raman spectrum. The method is based on an idea of spectral interference. Making use of a small portion of two Raman pump laser radiations, we produce two sum-frequency spectra that spectrally interfere with each other. Based on this interfering sum-frequency spectra, we successfully derive the spectral phase and reconstruct the temporal profile. The reliability of this method is also confirmed by measuring the spectral phase changes caused by intentionally inserted silica plates of various thicknesses and comparing them to theoretical predictions.