Abstract

The coupling of light between orthogonally polarized dielectric waveguide modes by means of optical effects stimulated in yttrium iron garnet (YIG) films by magnetostatic waves (MSWs) has been demonstrated in a variety of ways. MSW magnetooptic Bragg diffraction has been reported¹ with efficiency of 5%/W cm (rf power, interaction length) at frequencies above 3 GHz using surface waves (MSSWs) in a collinear diffraction geometry. Doppler shift of the frequency of the diffracted optical beam has been observed using forward volume waves (MSFVWs) in a transverse geometry. In recent work, the dependence of MSW dispersion characteristics on bias magnetic field strength has been exploited to extend the MSW-optical Bragg interaction bandwidth by employing a spatially gradient magnetic field. The basic character of this dependence is outlined for the particular case of MSFVW propagation perpendicular to the direction of the bias H-field variation, and theoretical results for various linear gradients are presented. Experimental observations which support predictions are presented; constant MSW propagation velocity over a broad frequency range is indicative of operation in a delimited wave number regime which can be tailored to coincide with the optical Bragg diffraction criteria. The trade-offs of decreased diffraction efficiency for increased bandwidth are discussed.

© 1985 Optical Society of America