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Self-excited oscillations in a mechanical resonator embedded in a nonlinear microwave cavity


  Oren Suchoi  ,  Lior Ella  ,  Oleg Shtempluk  ,  Eyal Buks  
 Russel Berry Nanotechnology Institute, Technion IIT, Israel
Faculty of electrical engineering, Technion IIT, Israel

Optomechanical cavities [1] can be used to change the e ective damping factor of mechanical resonators. While the interaction between a linear cavity and a mechanical resonator has been thoroughly investigated, the case of a nonlinear cavity has been addressed only theoretically [2]. We present an optomechanical system consisting of an oscillating mechanical resonator embedded in a superconducting microwave transmission line cavity, which is known to exhibit Dung-like nonlinear response. The devices are fabricated on silicon wafer from a single aluminum layer, and measured at 300mK. We use a niobium coated optical ber, which
is positioned precisely above the mechanical resonator at a distance of less than 1 m, thus creating a large position depended capacitor as well as an optical cavity. The microwave resonance frequency is shown to be highly dependent on the ber-mechanical resonator distance. The ber, which is electrically connected to an AC and DC voltage source can also be used for electrical actuation of the mechanical resonator. We present results of both thermally induced self-excited oscillations using the injected laser light [3] and in addition, also radiation pressure induced self-excited oscillations using injected microwave power. The region in which the self-excited oscillations are observed signi cantely deveates from what is expected from a cavity having a linear response. However, the experimental resultscan be accounted for by a model that takes into account the Dung-like nonlinearity of the microwave cavity. The system undergoes a Hopf bifurcation, which can be used to create macroscopic non-classical mechanical states [4].

[1] T. J. Kippenberg and K. J. Vahala, "Cavity opto-mechanics" Opt. Express, 15, 17172 (2007)

[2] P. D. Nation, M. P. Blencowe, and E. Buks, "Quantum analysis of a nonlinear microwave cavity-embedded dc squid displacement detector" Phys. Rev. B, 78, 104516 (2008)

[3] S. Zaitsev, A. K. Pandey, O. Shtempluck, and E. Buks, "Forced and self-excited oscillations of an optomechanical cavity" Phys. Rev. E, 84, 046605, (2011)

[4] A. Armour and D. Rodrigues, "Quantum dynamics of a mechanical resonator driven by a cavity" Comptes Rendus Physique, (2012)