  We have studied the propagation characteristics of spin wave modes in a
permalloy stripe by time-resolved magneto-optical Kerr effect techniques. We
observe a beating interference pattern in the time domain under the influence
of an electrical square pulse excitation at the center of the stripe. We also
probe the non-reciprocal behavior of propagating spin waves with a dependence
on the external magnetic field. Spatial dependence studies show that localized
edge mode spin waves have a lower frequency than spin waves in the center of
the stripe, due to the varying magnetization vector across the width of the
stripe.
