FORMATION, PROPAGATION, REFLECTION, AND COLLISION OF MICROWAVE ENVELOPE SOLITONS IN YTTRIUM-IRON-GARNET FILMS

The end edge reflection and collision of backward volume wave bright m icrowave magnetic envelope solitons in long and narrow yttrium iron ga rnet single-crystal films has been studied experimentally. The experim ents were done on 5.1-mu m-thick, 1-mm-wide films. The bright solitons were excited by single or double 8-36-ns-wide microwave pulses with a nominal carrier frequency of 5.8 GHz. The experiments utilized a mova ble transducer structure to make measurements for a range of transduce r separations from 2 to 15 mm and for pulses before and after reflecti on. The soliton character was established from single-pulse decay vers us time and distance measurements. Three decay regions were observed, a slow decay region before soliton formation, a fast decay region char acteristic of solitons, and a second slow decay for linear pulses. The soliton region included both incident and reflected pulses. The expon ential decay rate for the soliton regime was greater than for the Line ar. The soliton pulses retained the same shape and speed after edge re flection. An observed drop in pulse amplitude after passing under the pickup transducer provided a way to measure the actual power and ampli tude of the soliton signal. The measured amplitudes and widths were in fair agreement with predictions fur a simple sech-type order one soli ton pulse. For properly timed double-pulse experiments in which a refl ected lead pulse collides with the follow-on pulse before detection, t he effects of soliton collisions could be examined. In the single soli ton power regime, the pulses were found to rt tain their shape and spe ed after collision. At higher powers, shapes were nor retained. In add ition, a wake effect was observed in which the lead pulse causes a cha nge in the detected signal for the follow-on poise, even without colli sion.