Single Dark Soliton Research Articles

Phase properties of microwave magnetic envelope dark solitons in yttrium iron garnet thin films (abstract)

Although microwave magnetic envelope (MME) solitons in thin yttrium iron garnet (YIG) films have been studied extensively, only recently have dark MME solitons been observed. For a single dark soliton, one has a carrier phase change of 180°. Reference 1 indicated such a change. However, the overall phase change for a given dark pulse experiment should be 0°. The objective of this work was to examine phase profiles in detail for the dark soliton experiment. The results show that both of the above expectations are, in fact, satisfied. The 5 GHz measurements were done with a magnetostatic wave delay line structure with a long and narrow 7.2 μm thick single crystal YIG film oriented in the surface wave configuration. A GaAs microwave switch produced 300 ns long bright pulses separated by a dark pulse with a width in the 15 ns range. The input power was 0.002–1.0 W. The output signal showed two main dark pulse features, independent of power level. At low powers, the changes in phase across both features were small. With increasing power, the phase change across the first feature showed a rapid increase while the phase change for the second feature remained small. The phase change for the first feature saturated at a large value, on the order of 200°, relative to the phase change at low power. The phase change over the entire profile was always 0°. These results show: (1) There are significant phase changes at both low and high powers in the dark pulse experiment. (2) The phase change for a dark soliton must take into account the background phase change at lower powers. (3) Only the main dark pulse feature in the output profile exhibits single dark soliton characteristics through a clearly resolved phase saturation at 180°. (4) These thresholds are on the order of 10 mW for typical strip line transducer structures, compared to 100 mW or so for bright solitons.