Voltage-Controlled, Nonreciprocal Millimeter-Wave Propagation From Magnetoelastic Membranes Infused With Aligned Nickel Microparticles

Differential Faraday rotation of the linear polarization of millimeter-wave (mmW) Gaussian beams has been observed from a magnetoelastic material system consisting of a silicone membrane that was infused with aligned nickel microparticles, mounted to a piezoelectric annulus, and immersed in a static magnetic field. The piezoelectric crystal was driven near its radial mode of resonance by an ac voltage signal so as to periodically stretch the membrane about the axis of mmW propagation. The stretching modulated the distribution of nickel microparticles and resulted in a change in magnetic properties of the material, specifically the effective Verdet constant. A customized, quasi-optical apparatus was phase locked with the ac driving signal to determine the difference in Faraday rotation due to the stretched and un-stretched states of the membrane.