Plasmonic Optomechanical Switch

In this work we theoretically demonstrate the use of a two-level optomechanical system actuated by plasmon-mediated optical forces as a reconfigurable nanophotonic switch. We have simulated a nanostructured suspended gold membrane allowing the normal excitation of a Surface Plasmon Polariton by patterning an air nanohole array. By placing the membrane in a close proximity of a reflecting substrate, we observe a mode splitting which provides two stable mechanical states accessible by tunning the illuminating wavelength.<br/><br/>In recent years the active control of optical forces is attracting more and more attention from the scientific community ranging from the fundamental physics [1] to diverse applications such as optical (and plasmonic) tweezers [2], optically reconfigurable nanophotonic devices and cooling and/or amplification of the mechanical modes to reach the fundamental ground state [3] or to increase the sensitivity of inertial sensors [4]. In this work, we present a two level optomechanical system that can be statically or dynamically manipulated to act as an optical bit in photonic nanoprocessors or as an optical switcher. The accomplishment of the optical force modulation is theoretically demonstrated by means of the mechanical excitation of a suspended membrane consisting of an array of air nanoholes in a gold layer supporting surface plasmon polariton modes [5]. The nanostructured membrane is suspended over a silicon substrate assembling a Fabry-Perot microcavity that enables strong coupling between cavity and plasmonic modes [6].<br/>We simulate the whole optomechanical device through finite element simulations, including the coupled Fabry-Perot cavity. The optical force is calculated by the asymmetries in the integral of the Maxwell stress tensor over a closed surface around the suspended membrane. The Surface Plasmon Polariton and its influence on the optical force is calculated as a function of the cavity length. From the force calculation at a fixed wavelength a double potential well is obtained, showing two stable states with a central energy barrier. It is possible to dynamically actuate on the length of the cavity by introducing a mechanical actuation on the membrane by means of a harmonic displacement. The oscillatory movement of the suspended membrane can be modeled by a Duffing non-linear mechanical oscillator whose amplitude can be manipulated via optomechanical amplitude modulation (cooling or amplification). Therefore, the final state (stable) of the dynamical system can then be actively chosen, opening the door for the development of an optomechanical switch.<br/><br/><br/>1. Kim, E., Zhang, X., Ferreira, V. S., Banker, J., Iverson, J. K., Sipahigil, A., Bello, M., González-Tudela, A.,<br/>Mirhosseini, M. Painter O. “Quantum Electrodynamics in a Topological Waveguide” Phys. Rev. X 11,<br/>011015, 2021.<br/>2. Ashkin, A. “Optical trapping and manipulation of neutral particles using lasers” Proc. Natl. Acad. Sci. 94,<br/>4853–4860, 1997.<br/>3. Chan, J., Alegre, T. P., Safavi-Naeini, A. H., Hill, J. T., Krause, A., Gröblacher, S., Aspelmeyer, M. and<br/>Painter, O. “Laser cooling of a nanomechanical oscillator into its quantum ground state” Nature 478 (7367),<br/>89-92, 2010.<br/>4. Ramos, D., Gil-Santos, E., Pini, V., Llorens, J. M., Fernández-Regúlez, M., San Paulo, A., Calleja, M. and<br/>Tamayo J. “Optomechanics with silicon nanowires by harnessing confined electromagnetic modes” Nano<br/>letters 12 (2), 932-937, 2012<br/>5. Ramos, D., Malvar, O., Davis, Z. J., Tamayo, J. and Calleja, M. “Nanomechanical plasmon spectroscopy of<br/>single gold nanoparticles” Nano Letters 18 (11), 7165-7170, 2018.<br/>6. Castro, I., Garcia-Martin, A. and Ramos, D., “Plasmon Optomechanical Switch” In press.