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.

Breaking the symmetry of electromagnetic wave propagation enables important technological functionality. In particular, circulators are nonreciprocal components that can route photons directionally in classical or quantum photonic circuits and offer prospects for fundamental research on electromagnetic transport. Developing highly efficient circulators thus presents an important challenge, especially to realise compact reconfigurable implementations that do not rely on magnetic fields to break reciprocity. We demonstrate optical circulation utilising radiation pressure interactions in an on-chip multimode optomechanical system. Mechanically mediated optical mode conversion in a silica microtoroid provides a synthetic gauge bias for light, enabling four-port circulation that exploits tailored interference between appropriate light paths. We identify two sideband conditions under which ideal circulation is approached. This allows to experimentally demonstrate ~10 dB isolation and <3 dB insertion loss in all relevant channels. We show the possibility of actively controlling the circulator properties, enabling ideal opportunities for reconfigurable integrated nanophotonic circuits.

Optical isolation, non-reciprocal phase transmission and topological phases for light based

Perturbing open cavities: Anomalous resonance frequency shifts in a hybrid cavitynanoantenna system Ruesink, F.; Doeleman, H.M.; Hendrikx, R.; Koenderink, A.F.; Verhagen, E. Link to publicationCitation for published version (APA): Ruesink, F., Doeleman, H. M., Hendrikx, R., Koenderink, A. F., & Verhagen, E. (2015). Perturbing open cavities: Anomalous resonance frequency shifts in a hybrid cavity-nanoantenna system. Physical Review Letters, 115(29), [203904]. https://doi.org/10.1103/PhysRevLett.115.203904 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. The influence of a small perturbation on a cavity mode plays an important role in fields like optical sensing, cavity quantum electrodynamics, and cavity optomechanics. Typically, the resulting cavity frequency shift directly relates to the polarizability of the perturbation. Here, we demonstrate that particles perturbing a radiating cavity can induce strong frequency shifts that are opposite to, and even exceed, the effects based on the particles' polarizability. A full electrodynamic theory reveals that these anomalous results rely on a nontrivial phase relation between cavity and nanoparticle radiation, allowing backaction via the radiation continuum. In addition, an intuitive model based on coupled mode theory is presented that relates the phenomenon to retardation. Because of the ubiquity of dissipation, we expect these findings to benefit the understanding and engineering of a wide class of systems.

We study the structural dynamics of the photoactivated molecular proton crane 7-hydroxy-8-(morpholinomethyl)quinoline using femtosecond UV-pump IR-probe spectroscopy. Upon electronic excitation, a proton is transferred from the hydroxy to the amine group located on the rotatable morpholino side group. This morpholino group subsequently delivers the proton to the aromatic quinoline nitrogen by rotation around the C-C bond. Time-resolved vibrational spectroscopy allows us to study this process in unprecedented detail. We find that the transport of the proton involves multiple time scales. Upon photoexcitation, the OH proton is transferred within <300 fs to the morpholino side group. After this, the intramolecular hydrogen bond that locks the crane arm breaks with a time constant of 36 ± 1 ps. Subsequently, the protonated crane arm rotates with a time constant of 334 ± 12 ps to deliver the proton at the quinoline moiety. After the proton crane has returned to its electronic ground state with a time constant 700 ± 22 ps, the proton is transferred back from the quinoline nitrogen to the negatively charged O atom. The time constant of the back rotation is 39.8 ± 0.2 ns, about 200 times slower than the forward proton transfer.