Ultrafast spin dynamics in ferromagnetic half-metallic compound Sr 2 FeMoO 6 is investigated by pump-probe measurements of magneto-optical Kerr effect.Half-metallic nature of this material gives rise to anomalous thermal insulation between spins and electrons, and allows us to pursue the spin dynamics from a few to several hundred picoseconds after the optical excitation. The optically detected magnetization dynamics clearly shows the crossover from microscopic photo-induced demagnetization to macroscopic critical behavior with universal power law divergence of relaxation time for wide dynamical critical region.Typeset using REVT E X 1

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We experimentally demonstrate 50 cascaded all-optical 3R regenerators over a 1,000 km transmission distance for 10-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) signals. The regenerator consists of integrated Mach-Zehnder interferometer (MZI) semiconductor optical amplifier (SOA) based wavelength converters. Regenerative properties and tolerance to pattern dependent effects have been studied in terms of Q-factor measurement, and error free operation with input OSNR of 20 dB/0.1 nm has also been demonstrated.

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