BACKWARD-VOLUME-WAVE MICROWAVE-ENVELOPE SOLITONS IN YTTRIUM-IRON-GARNET FILMS

Microwave-magnetic-envelope (MME) solitons generated from nonlinear ma gnetostatic-backward-volume wave packets have been observed in magneti c thin films. The MME signals were excited by 5-50-ns wide microwave p ulses at 5.8 GHz in a 15-mm-long by 2.5-mm-wide, 7.2-mum-thick single- crystal yttrium iron garnet (YIG) film strip magnetized in plane and p arallel to the long side of the strip. The wave packets were propagate d parallel to the static field. The wave packets were launched and the propagating MME pulse signals were detected with planar microstrip tr ansducers 4 mm apart. Envelope soliton behavior was evident from the t ime-resolved wave forms observed for various input power and pulse wid th combinations. At low power levels, one sees a relatively broad outp ut pulse which scales with the width of the input pulse and a peak pow er which increases linearly with the input power. As the input power i s increased above some threshold in the 0.5-1-W range, output pulses s how a narrowing and steepening which is characteristic of microwave-ma gnetic-envelope solitons. Further increases in input power produce mul tiple-peak profiles, characteristic of multiple soliton generation. Th e experimental results are consistent with the various characteristic times for linear and nonlinear MME pulse propagation and soliton forma tion. However, numerical modeling based on the magnetic form of the no nlinear Schrodinger equation with initial conditions and parameters wh ich match the experiments yields calculated profiles which show solito n effects but do not quantitatively match the experimental results.