Forward volume wave microwave envelope solitons in yttrium iron garnet thin films: Peak profiles and multisoliton signatures (abstract)

Abstract

Microwave envelope solitons have been observed in yttrium iron garnet (YIG) films for different field configurations and surface pinning conditions. Earlier work on magnetostatic forward volume wave (MSFVW) solitons in YIG films has focused on the break from the low power linear dependence of the output pulse peak power Pout on input pulse power Pin,1 or on the evolution of the shape of the microwave pulse envelope with increasing power.2 In this work, both (1) the nonlinear dependence of Pout on Pin and (2) the shape of the output pulses for MSFVW solitons have been examined over a wide range of power levels and pulse widths. The experiments used 7.2-μm-thick single crystal YIG films with unpinned surface spins. A field of 3744 Oe was applied perpendicular to the plane of a 15×2 mm film sample. Microwave pulses at 5.4–6 GHz, with a width τ of 5–50 ns and peak powers up to 3 W, were launched by a microstrip antenna about 5 mm from one end and picked up by a second, parallel antenna about 5 mm from the other end. Data were processed with a microwave transition analyzer operated in a time domain mode. For a given pulse width, the initial break and nonlinear increase in Pout relative to Pin noted in Ref. 1 is followed by a gradual leveling off in Pout at high power. For a given pulse power above soliton threshold, the Pout versus τ profiles show an initial linear increase which is followed by a decrease and an oscillatory response as multiple solitons are formed. These profiles are directly correlated with the formation of a single soliton pulse which evolves into multiple soliton wave packets with increasing either power or pulse length.