title: Near optimal graphene terahertz non-reciprocal isolator.
abstract: Isolators, or optical diodes, are devices enabling unidirectional light propagation by using non-reciprocal optical materials, namely materials able to break Lorentz reciprocity. The realization of isolators at terahertz frequencies is a very important open challenge made difficult by the intrinsically lossy propagation of terahertz radiation in current non-reciprocal materials. Here we report the design, fabrication and measurement of a terahertz non-reciprocal isolator for circularly polarized waves based on magnetostatically biased monolayer graphene, operating in reflection. The device exploits the non-reciprocal optical conductivity of graphene and, in spite of its simple design, it exhibits almost 20 dB of isolation and only 7.5 dB of insertion loss at 2.9 THz. Operation with linearly polarized light can be achieved using quarter-wave plates as polarization converters. These results demonstrate the superiority of graphene with respect to currently used terahertz non-reciprocal materials and pave the way to a novel class of optimal non-reciprocal devices.
authors.affiliation: Laboratory of Electromagnetics and Antennas (LEMA), Ecole Polytechnique Fédérale de Lausanne, EPFL, Station 11, 1015 Lausanne, Switzerland.
authors.forename: Michele
authors.initials: M
authors.lastname: Tamagnone
authors.affiliation: Nanoelectronic Devices Laboratory (NANOLAB), École Polytechnique Fédérale de Lausanne, EPFL, Station 11, 1015 Lausanne, Switzerland.
authors.forename: Clara
authors.initials: C
authors.lastname: Moldovan
authors.affiliation: Department of Quantum Matter Physics (DQMP), Université de Genève, Quai Ernest-Ansermet 24, 1211 Genève-4, Switzerland.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Poumirol
authors.affiliation: Department of Quantum Matter Physics (DQMP), Université de Genève, Quai Ernest-Ansermet 24, 1211 Genève-4, Switzerland.
authors.forename: Alexey B
authors.initials: AB
authors.lastname: Kuzmenko
authors.affiliation: Nanoelectronic Devices Laboratory (NANOLAB), École Polytechnique Fédérale de Lausanne, EPFL, Station 11, 1015 Lausanne, Switzerland.
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Ionescu
authors.affiliation: Laboratory of Electromagnetics and Antennas (LEMA), Ecole Polytechnique Fédérale de Lausanne, EPFL, Station 11, 1015 Lausanne, Switzerland.
authors.forename: Juan R
authors.initials: JR
authors.lastname: Mosig
authors.affiliation: Adaptive MicroNano Wave Systems, Ecole Polytechnique Fédérale de Lausanne, EPFL, Station 11, 1015 Lausanne, Switzerland.
authors.forename: Julien
authors.initials: J
authors.lastname: Perruisseau-Carrier