Characterization of optical signals in fiber-optic Fourier converter

We demonstrate a new technique for the direct real-time pico- femtosecond scale temporal measurements based on the nonlinear-optic process of Fourier transformation (NOFT): the conversion of the temporal information to the spectral. This performance is implemented in the fiber-optic spectral compressor, first stretching and up-chirping the pulses in dispersive delay, and after quenching the induced chirp by means of self- or cross- phase modulation in the single-mode fiber. The accurate quenching of the induced chirp brings to the spectral imaging of pulse temporal profile, reducing the problem of the high-resolution temporal measurements to the standard spectrometry. The problem of spectroscopy becomes complicated for ultrafast processes because of the low temporal resolution of electronic oscilloscopes, and often the complex techniques of phase measurements are developed. NOFT with a spectrometer can serve as an ultrafast optical oscilloscope: the resolution is limited only by the temporal response of the Kerr effect, which is similar to 5fs for silica. In our pico- and femtosecond scale experiments, with the Nd:YAG and Ti:Sapphire lasers, we shaped the multi-peak pulses, implement the radiation spectral compression, and check the given shapes of purses by means of the spectrometer in order to demonstrate the above mentioned "oscilloscopic" performance.