Optical-Magnetostatic Wave Interaction For Spectrum Analysis

Spectrum analysis of microwave signals can be performed using Bragg diffraction of light by magnetostatic waves (MSW's). MSW wave propagation must occur in a thin-film magnetic, ferrite medium, such as YIG. Since it is possible to propagate guided optical waves in the same film, rf spectrum analyzers analogous to those using guided optical wave interaction with surface acoustic waves can be constructed. Intrinsic advantages of the optical-MSW device include high center frequencies of operation, up to 20 GHz and beyond, and tunability of the center frequency. The theory of optical-MSW interactions and laboratory demonstrations of such interactions are summarized. Design considerations for a spectrum analyzer device are discussed, including materials, rf-to-MSW transduction, light sources, thin-film light coupling, and photodetectors.