title: Giant non-reciprocity at the subwavelength scale using angular momentum-biased metamaterials.
abstract: Breaking time-reversal symmetry enables the realization of non-reciprocal devices, such as isolators and circulators, of fundamental importance in microwave and photonic communication systems. This effect is almost exclusively achieved today through magneto-optical phenomena, which are incompatible with integrated technology because of the required large magnetic bias. However, this is not the only option to break reciprocity. The Onsager-Casimir principle states that any odd vector under time reversal, such as electric current and linear momentum, can also produce a non-reciprocal response. These recently analysed alternatives typically work over a limited portion of the electromagnetic spectrum and/or are often characterized by weak effects, requiring large volumes of operation. Here we show that these limitations may be overcome by angular momentum-biased metamaterials, in which a properly tailored spatiotemporal modulation is azimuthally applied to subwavelength Fano-resonant inclusions, producing largely enhanced non-reciprocal response at the subwavelength scale, in principle applicable from radio to optical frequencies.
authors.affiliation: Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Dimitrios L
authors.initials: DL
authors.lastname: Sounas
authors.forename: Christophe
authors.initials: C
authors.lastname: Caloz
authors.forename: Andrea
authors.initials: A
authors.lastname: Alù