title: Nonreciprocity and magnetic-free isolation based on optomechanical interactions.
abstract: Nonreciprocal components, such as isolators and circulators, provide highly desirable functionalities for optical circuitry. This motivates the active investigation of mechanisms that break reciprocity, and pose alternatives to magneto-optic effects in on-chip systems. In this work, we use optomechanical interactions to strongly break reciprocity in a compact system. We derive minimal requirements to create nonreciprocity in a wide class of systems that couple two optical modes to a mechanical mode, highlighting the importance of optically biasing the modes at a controlled phase difference. We realize these principles in a silica microtoroid optomechanical resonator and use quantitative heterodyne spectroscopy to demonstrate up to 10 dB optical isolation at telecom wavelengths. We show that nonreciprocal transmission is preserved for nondegenerate modes, and demonstrate nonreciprocal parametric amplification. These results open a route to exploiting various nonreciprocal effects in optomechanical systems in different electromagnetic and mechanical frequency regimes, including optomechanical metamaterials with topologically non-trivial properties.
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.
authors.forename: Freek
authors.initials: F
authors.lastname: Ruesink
authors.affiliation: Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Mohammad-Ali
authors.initials: MA
authors.lastname: Miri
authors.affiliation: Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Alù
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands.
authors.forename: Ewold
authors.initials: E
authors.lastname: Verhagen