Peter T. Rakich

Yale University, New Haven, Connecticut, United States

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Publications (115)317.41 Total impact

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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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    William H. Renninger, Peter T. Rakich
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    ABSTRACT: A variety of analytical and numerical methods have been used to describe coherent waveform generation in Kerr frequency comb systems. However, a universal and simple analytical framework that captures the diversity of nonlinear phenomena in such systems remains elusive. Here we identify a single closed-form analytical solution of the driven nonlinear Schrodinger equation, and we demonstrate that this solution reproduces a large class of the behaviors in Kerr-comb systems. Specifically, we show that bright and dark soliton solutions as well as periodic wavetrain solutions arise from the same solution. In correspondence with experiments, solitons exist only at negative detuning and dispersion whereas wavetrains can exist for any sign of dispersion and detuning. From this closed-form solution, an area theorem is derived that relates the pulse duration and peak powers within Kerr-comb systems; conditions for existence of such pulses is given by a pump-detuning relation. These results are validated using simulations, demonstrating good agreement with established experimental results. Hence, this analytical framework provides simple design guidelines for the prediction of new regimes of improved Kerr-comb performance.
  • Heedeuk Shin, Peter T Rakich
    Nature Nanotechnology 11/2014; 9(11):878-80. DOI:10.1038/nnano.2014.259 · 33.27 Impact Factor
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    ABSTRACT: Rapid progress in silicon photonics has fostered numerous chip-scale sensing, computing, and signal processing technologies. However, many crucial filtering and signal delay operations are difficult to perform with all-optical devices. Unlike photons propagating at luminal speeds, GHz-acoustic phonons with slow velocity allow information to be stored, filtered, and delayed over comparatively smaller length-scales with remarkable fidelity. Hence, controllable and efficient coupling between coherent photons and phonons enables new signal processing technologies that greatly enhance the performance and potential impact of silicon photonics. Here, we demonstrate a novel mechanism for coherent information processing based on traveling-wave photon-phonon transduction, which achieves a phonon emit-and-receive process between distinct nanophotonic waveguides. Using this device physics-which can support 1-20GHz frequencies-we create wavelength-insensitive radio-frequency photonic filters with an unrivaled combination of stopband attenuation, selectivity, linewidth, and power-handling in silicon. More generally, this emit-receive concept is the impetus for numerous powerful new signal processing schemes.
    Nature Communications 09/2014; 6. DOI:10.1038/ncomms7427 · 10.74 Impact Factor
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    S. Hossein Mousavi, Peter T. Rakich, Zheng Wang
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    ABSTRACT: Single-layer graphene exhibits exceptional mechanical properties attractive for optomechanics: it combines low mass density, large tensile modulus, and low bending stiffness. However, at visible wavelengths, graphene absorbs weakly and reflects even less, thereby inadequate to generate large optical forces needed in optomechanics. Here, we numerically show that a single-layer graphene sheet is sufficient to produce strong optical forces under terahertz or infrared illumination. For a system as simple as graphene suspended atop a uniform substrate, high reflectivity from the substrate is crucial in creating a standing-wave pattern, leading to a strong optical force on graphene. This force is readily tunable in amplitude and direction by adjusting the suspension height. In particular, repellent optical forces can levitate graphene to a series of stable equilibrium heights above the substrate. One of the key parameters to maximize the optical force is the excitation frequency: peak forces are found near the scattering frequency of free carriers in graphene. With a dynamically controllable Fermi level, graphene opens up new possibilities of tunable nanoscale optomechanical devices.
    06/2014; 1(11). DOI:10.1021/ph500207y
  • Hossein Mousavi, Peter Rakich, Zheng Wang
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    ABSTRACT: We demonstrate that judicious selection of mirrors/substrates, operational frequency, and graphene location inside a cavity yields unprecedented optical forces on graphene, while tolerably modifies Q of the cavity .
    CLEO: Science and Innovations; 06/2014
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    ABSTRACT: We present the first time-domain measurement of a guided-wave nano-opto-mechanical system, resulting in the coherent excitation of multiple mechanical modes. We deconvolved the electronic and mechanical responses to observe the evolution of the coherent superposition.
    CLEO: Science and Innovations; 06/2014
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    ABSTRACT: We present progress towards the development of novel hybrid photonic-phononic oscillator technologies in both nanoscale silicon photonics and in fiber optic systems. These systems utilize traveling-wave photon-phonon couplings involving both stimulated Brillouin scattering processes (SBS). We explore numerous geometries that have enabled large forward-SBS processes in nanoscale silicon waveguides for the first time, and examine new approaches to achieving integrated Brillouin based signal processing.
    SPIE Defense + Security; 06/2014
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    ABSTRACT: We develop a general framework of evaluating the gain coefficient of Stimulated Brillouin Scattering (SBS) in optical waveguides via the overlap integral between optical and elastic eigen-modes. We show that spatial symmetry of the optical force dictates the selection rules of the excitable elastic modes. By applying this method to a rectangular silicon waveguide, we demonstrate the spatial distributions of optical force and elastic eigen-modes jointly determine the magnitude and scaling of SBS gain coefficient in both forward and backward SBS processes. We further apply this method to inter-modal SBS process, and demonstrate that the coupling between distinct optical modes are necessary to excite elastic modes with all possible symmetries.
    Optics Express 12/2013; 21(25):31402-19. DOI:10.1364/OE.21.031402 · 3.53 Impact Factor
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    ABSTRACT: Strong light-boundary interactions alter the nature of traveling-wave photon-phonon coupling at nanoscales. Harnessing such effects, stimulated Brillouin scattering is realized for the first time in silicon photonics via a new class of waveguides.
    Integrated Photonics Research, Silicon and Nanophotonics; 07/2013
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    ABSTRACT: The dispersive properties of phononic crystals can be utilized to manipulate the phononic impedance of a material and to engineer the frequency-delay response of time domain signal processing circuits. In this paper we study, in both the frequency and time domains, the dispersive properties of phononic crystals formed in thin suspended plates of aluminum nitride.
    2013 IEEE International Ultrasonics Symposium (IUS); 07/2013
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    ABSTRACT: The nonlinear of a nanoscale Brillouin-active silicon waveguide is examined through heterodyne four-wave mixing experiments. The interference between Brillouin scattering, Kerr, and dispersive free-carrier nonlinearities are analytically described to explain the characteristic line-shapes observed.
    CLEO: Science and Innovations; 06/2013
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    ABSTRACT: We develop a general framework of evaluating slow-light performance using Stimulated Brillouin Scattering (SBS) in optical waveguides via the overlap integral between optical and elastic eigen-modes. We show that spatial symmetry of the optical force dictates the selection rules of the excitable elastic modes. By applying this method to a rectangular silicon waveguide, we demonstrate the spatial distributions of optical force and elastic eigen-modes jointly determine the magnitude and scaling of SBS gain coefficient in both forward and backward SBS processes. We further apply this method to inter-modal SBS process, and demonstrate that the coupling between distinct optical modes is necessary to excite elastic modes with all possible symmetries.
    Proceedings of SPIE - The International Society for Optical Engineering 03/2013; DOI:10.1117/12.2010049 · 0.20 Impact Factor
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    ABSTRACT: Nanoscale modal confinement is known to radically enhance the effect of intrinsic Kerr and Raman nonlinearities within nanophotonic silicon waveguides. By contrast, stimulated Brillouin-scattering nonlinearities, which involve coherent coupling between guided photon and phonon modes, are stifled in conventional nanophotonics, preventing the realization of a host of Brillouin-based signal-processing technologies in silicon. Here we demonstrate stimulated Brillouin scattering in silicon waveguides, for the first time, through a new class of hybrid photonic-phononic waveguides. Tailorable travelling-wave forward-stimulated Brillouin scattering is realized-with over 1,000 times larger nonlinearity than reported in previous systems-yielding strong Brillouin coupling to phonons from 1 to 18 GHz. Experiments show that radiation pressures, produced by subwavelength modal confinement, yield enhancement of Brillouin nonlinearity beyond those of material nonlinearity alone. In addition, such enhanced and wideband coherent phonon emission paves the way towards the hybridization of silicon photonics, microelectromechanical systems and CMOS signal-processing technologies on chip.
    Nature Communications 01/2013; 4:1944. DOI:10.1038/ncomms2943 · 10.74 Impact Factor
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    ABSTRACT: We examine the physics of traveling-wave photon-phonon coupling within nanoscale silicon waveguides and explore a host of new Brillouin-based signal processing technologies enabled by tailorable stimulated Brillouin processes in silicon photonics. Theoretical analysis of Brillouin coupling at sub-wavelength scales is presented, revealing that strong light-boundary interactions produce large radiation pressures mediated Brillouin nonlinearities. Experimental results demonstrating stimulated Brillouin scattering in silicon waveguides for the first time are also presented, revealing 1000 times larger forward stimulated Brillouin gain coeffcients than any prior system.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2013; DOI:10.1117/12.2007918 · 0.20 Impact Factor
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    ABSTRACT: We show that the nature of stimulated Brillouin scattering (SBS) radically changes at nanoscales due to tremendous internal radiation pressures. Coherent interplay between radiation pressure and electrostriction yields giant enhancement of SBS and tailorable photon-phonon coupling.
    Laser Science; 10/2012
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    Wenjun Qiu, Peter T. Rakich, Marin Soljacic, Zheng Wang
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    ABSTRACT: We develop a general method of calculating Stimulated Brillouin Scattering (SBS) gain coefficient in axially periodic waveguides. Applying this method to a silicon periodic waveguide suspended in air, we demonstrate that SBS nonlinearity can be dramatically enhanced at the brillouin zone boundary where the decreased group velocity of light magnifies photon-phonon interaction. In addition, we show that the symmetry plane perpendicular to the propagation axis plays an important role in both forward and backward SBS processes. In forward SBS, only elastic modes which are even about this plane are excitable. In backward SBS, the SBS gain coefficients of elastic modes approach to either infinity or constants, depending on their symmetry about this plane at $q=0$.
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    ABSTRACT: Low-contrast all-optical Zeno switching has been demonstrated in a Silicon Nitride microdisk resonator surrounded by hot Rubidium vapor. The device is based on the suppression of the cavity field buildup due to non-degenerate two-photon absorption.
    Nonlinear Photonics; 06/2012
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    ABSTRACT: Low-contrast all-optical Zeno switching has been demonstrated in a silicon nitride microdisk resonator coupled to a hot atomic vapor. The device is based on the suppression of the field build-up within a microcavity due to non-degenerate two-photon absorption. This experiment used one beam in a resonator and one in free-space due to limitations related to device physics. These results suggest that a similar scheme with both beams resonant in the cavity would correspond to input power levels near 20 nW.
    Physical Review A 06/2012; 87(2). DOI:10.1103/PhysRevA.87.023808 · 2.99 Impact Factor
  • Zheng Wang, Peter Rakich
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    ABSTRACT: Optical forces have been traditionally decomposed into gradient force and scattering force. We show the limit of this decomposition and the non-conservative nature of optical forces, even for single particle confined in a single-mode waveguide.
    CLEO: Science and Innovations; 05/2012

Publication Stats

2k Citations
317.41 Total Impact Points

Institutions

  • 2013–2015
    • Yale University
      • Department of Applied Physics
      New Haven, Connecticut, United States
  • 2009–2012
    • Sandia National Laboratories
      Albuquerque, New Mexico, United States
  • 2001–2008
    • Massachusetts Institute of Technology
      • • Research Laboratory of Electronics
      • • Department of Materials Science and Engineering
      Cambridge, MA, United States
  • 2004
    • Columbia University
      New York City, New York, United States