Direct observation of surface wave excitations in magnetostatic wave devices

The Brillouin light scattering (BLS) technique has been used for the direct detection of magnetostatic wave (MSW) excitations in a signal-to-noise enhancer MSW device structure. The device consists of a 23 μm wide microstrip transmission line in contact with a 26.6 μm thick single crystal yttrium iron garnet film on a gadolinium gallium garnet substrate, with the applied static magnetic field parallel to the strip-line. By utilizing the wave vector- and frequency-selective capabilities of the BLS spectrometer, it was possible to determine the wave vector distributions of the MSW excitations at both low and high input microwave power levels. At low power levels, the spectra at 3.6 GHz consisted of magnetostatic surface wave excitations with wave number k from about 50 cm^-1to 200 cm^-1and propagation perpendicular to the field and microstrip line direction. At high power levels, parametric half-frequency excitations were observed with k-values greater than 10⁴cm^-1.