Optical probing of magnetostatic forward volume waves in thin film yttrium-iron-garnet

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Abstract
An optical probe system has been developed that uses magneto-optic effects to examine the microwave magnetization of microwave magnetostatic waves propagating in thin ferrite films. The optical probe uses light from a 45 mW, 1.15 μm He-Ne laser which is focused upon a ferrite for localized probing. An effective spatial resolution of 100 μm was achieved with the optical probe. Experiments to examine linear and nonlinear magnetostatic forward volume waves (MSFVW) were conducted with the probe. MSFVW, with microwave frequency from 1 to 2 GHz, were launched in the [21̄1̄] direction of a thin film of liquid-phase-epitaxy (LPE) yttrium-iron-garnet (YIG). The LPE-YIG thin film was 47.4 μm thick, and deposited on a 1-in. disk of gadolinium-gallium-garnet with the [111] direction perpendicular to the surface of the disk. The nonlinear microwave MSFVW effects were characterized by a MSFVW power saturation and then a decline as input power to the MSFVW was increased. Localized optical probing of nonlinear effects, along the propagation path of the MSFVW, showed that a monotonic increase in MSFVW modulation of light with increasing microwave input power does not always occur. Optical probing of linear MSFVW examined the evolution of a MSFVW profile, transverse to the phase-propagation direction, as the MSFVW traveled from its launching antenna.