A bi-crystal heterostructure includes a first, substantially uniaxial, crystal layer; a second, substantially uniaxial, crystal layer positioned adjacent to the first crystal layer, and wherein the first and second crystal layers have mutually opposite rotations of their respective principal cross-sectional axes of a degree sufficient to impart negative refractivity in the heterostructure; a conductive metal strip positioned between the crystal layers and having a principal longitudinal axis sufficiently aligned with an unrotated principal axis of each of the first and second crystal layers to permit unidirectional electromagnetic wave propagation in the conductive metal strip; and a lossy metal strip positioned between the crystal layers and having a principal axis positioned substantially parallel to the principal axis of the conductive metal strip. Alternatively, one or both of the crystal layers can be replaced with a ferroelectric crystal with an associated static bias voltage source for imparting the uniaxial property to achieve the said crystal layers mutually opposite axes rotations. The conductive metal strip when wired with connectors at each end and positioned in an electrical circuit, e.g. an rf transmitting system, operates as an electrical isolator, substantially blocking signals in one direction while transmitting in the opposite direction.
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