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arXiv · 1501.04248

Long-lived guided phonons in fiber by manipulating two-level systems

R. O. Behunin·P. Kharel·W. H. Renninger·H. Shin·F. Carter·E. Kittlaus·P. T. Rakich
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Abstract

The synthesis of ultra-long lived acoustic phonons in a variety of materials and device geometries could enable a range of new coherent information processing and sensing technologies; many forms of phonon dissipation pose a barrier to this goal. We explore linear and nonlinear contributions to phonon dissipation in silica at cryogenic temperatures using fiber-optic structures that tightly confine both photons and phonons to the fiber-optic core. When immersed in helium, this fiber system supports nearly perfect guidance of 9 GHz acoustic phonons; strong electrostrictively mediated photon-phonon coupling (or guided-wave stimulated Brillouin scattering) permits a flexible form of laser-based phonon spectroscopy. Through linear and nonlinear phonon spectroscopy, we isolate the effects of disorder-induced two-level tunneling states as a source of phononic dissipation in this system. We show that an ensemble of such two-level tunneling states can be driven into transparency--virtually eliminating this source of phonon dissipation over a broad range of frequencies. Experimental studies of phononic self-frequency saturation show excellent agreement with a theoretical model accounting for the phonon coupling to an ensemble of two-level tunneling states. Extending these results, we demonstrate a general approach to suppress dissipation produced by two-level tunneling states via cross-saturation, where the lifetime of a phonons at one frequency can be extended by the presence of a high intensity acoustic beam at another frequency. Although these studies were carried out in silica, our findings are quite general, and can be applied to a range of materials systems and device geometries.

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R. O. Behunin, P. Kharel, W. H. Renninger, H. Shin, F. Carter, E. Kittlaus, P. T. Rakich. 2015-01-18. Long-lived guided phonons in fiber by manipulating two-level systems. https://arxiv.org/abs/1501.04248

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