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A nonlinear optical processor that is capable of real-time conversion of a femtosecond pulse sequence into its spatial image is introduced, analyzed, and experimentally characterized. The method employs nonlinear spectral domain three-wave mixing in a crystal of LiB 3 O 5 , where spectral decomposition waves of a shaped femtosecond pulse are mixed with those of a transform-limited pulse to generate a quasi-monochromatic second-harmonic field. By means of this nonlinear process, the temporal-frequency content of the shaped pulse is directly encoded onto the spatial-frequency content of the second-harmonic field, producing a spatial image of the temporal shaped pulse. We show that, unlike the commonly used autocorrelator, such time-tospace conversion carries both amplitude and phase information on the shape of the femtosecond pulses.

Optical processors that perform parallel-to-serial and serial-to-parallel data conversion are introduced and experimentally demonstrated for long-distance optical communication networks.

We describe a new method for quantum key distribution that utilizes phase modulation of sidebands of modulation by use of integrated electro-optic modulators at the transmitting and receiving modules. The system is shown to produce constructive or destructive interference with unity visibility, which should allow quantum cryptography to be carried out with high flexibility by use of conventional devices.

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We propose a method for direct conversion of an ultrashort pulse into a monochromatic beam whose wave front either repeats or is related to the phase structure of the pulse or its spectrum. This can be done by sum-frequency generation of the spectrally resolved pulses. Experimentally, we projected two spectra of the same chirped pulse onto the nonlinear crystal so that the dispersions were opposite. After sum-frequency generation, a converging or diverging monochromatic beam was formed that was the analog of the pulse spectrum. We could determine the chirp value by the measurement of the wave-front radius.