Academic Appointments

Professional Education

  • Ph.D., California Institute of Technology, Applied Physics (2013)
  • B.ASc., University of Waterloo, Electrical Engineering (2008)


  • Jeremy D Witmer, Patricio Arrangoiz-Arriola, Jeff T Hill, Amir H Safavi-Naeini, Timothy Patrick McKenna. "United States Patent US20180113373A1 Doubly-resonant electro-optic conversion using a superconducting microwave resonator", Leland Stanford Junior University, Oct 23, 2017
  • Oskar Painter, Martin WINGER, Qiang Lin, Amir SAFAVI-NAEINI, Thiago ALEGRE, Timothy Dobson BLASIUS, Alexander Grey KRAUSE. "United States Patent US20130121633 A1 Systems and methods for tuning a cavity", California Institute Of Technology, Nov 11, 2011

2019-20 Courses

Stanford Advisees

  • Doctoral Dissertation Reader (AC)
    Okan Atalar, Emily Davis, Brannon Klopfer, Stephen Kuenstner, Daniil Lukin, Ognjen Markovic, Edwin Ng, Logan Su, Jiahui Wang, Yunfan Wu
  • Postdoctoral Faculty Sponsor
    Vahid Ansari, Raphael Van Laer
  • Doctoral Dissertation Advisor (AC)
    Stephan Eismann, Rachel Gruenke, Nathan Lee, Timothy McKenna, Kevin Multani, Rishi Patel, Chris Sarabalis, Jeremy Witmer, Alex Wollack
  • Doctoral (Program)
    Jason Herrmann, Wil Kao, Vasily Kruzhilin, Sze Cheung Lau, Aaron Sharpe, Kejun Xu, Fan Yang

All Publications

  • Piezoelectric Transduction of a Wavelength-Scale Mechanical Waveguide PHYSICAL REVIEW APPLIED Dahmani, Y. D., Sarabalis, C. J., Jiang, W., Mayor, F. M., Safavi-Naeini, A. H. 2020; 13 (2)
  • S-band delay lines in suspended lithium niobate JOURNAL OF APPLIED PHYSICS Sarabalis, C. J., Dahmani, Y. D., Cleland, A. Y., Safavi-Naeini, A. H. 2020; 127 (5)

    View details for DOI 10.1063/1.5126428

    View details for Web of Science ID 000513135300009

  • Efficient bidirectional piezo-optomechanical transduction between microwave and optical frequency. Nature communications Jiang, W., Sarabalis, C. J., Dahmani, Y. D., Patel, R. N., Mayor, F. M., McKenna, T. P., Van Laer, R., Safavi-Naeini, A. H. 2020; 11 (1): 1166


    Efficient interconversion of both classical and quantum information between microwave and optical frequency is an important engineering challenge. The optomechanical approach with gigahertz-frequency mechanical devices has the potential to be extremely efficient due to the large optomechanical response of common materials, and the ability to localize mechanical energy into a micron-scale volume. However, existing demonstrations suffer from some combination of low optical quality factor, low electrical-to-mechanical transduction efficiency, and low optomechanical interaction rate. Here we demonstrate an on-chip piezo-optomechanical transducer that systematically addresses all these challenges to achieve nearly three orders of magnitude improvement in conversion efficiency over previous work. Our modulator demonstrates acousto-optic modulation with [Formula: see text] = 0.02 V. We show bidirectional conversion efficiency of [Formula: see text] with 3.3 μW  red-detuned optical pump, and [Formula: see text] with 323 μW blue-detuned pump. Further study of quantum transduction at millikelvin temperatures is required to understand how the efficiency and added noise are affected by reduced mechanical dissipation, thermal conductivity, and thermal capacity.

    View details for DOI 10.1038/s41467-020-14863-3

    View details for PubMedID 32127538

  • Mechanical Purcell filters for microwave quantum machines APPLIED PHYSICS LETTERS Cleland, A. Y., Pechal, M., Stas, P. C., Sarabalis, C. J., Wollack, E., Safavi-Naeini, A. H. 2019; 115 (26)

    View details for DOI 10.1063/1.5111151

    View details for Web of Science ID 000505613600017

  • Cryogenic packaging of an optomechanical crystal OPTICS EXPRESS McKenna, T. P., Patel, R. N., Witmer, J. D., Van Laer, R., Valery, J. A., Safavi-Naeini, A. H. 2019; 27 (20): 28782–91
  • Lithium niobate piezo-optomechanical crystals OPTICA Jiang, W., Patel, R. N., Mayor, F. M., Mckenna, T. P., Arrangoiz-Arriola, P., Sarabalis, C. J., Witmer, J. D., Van Laer, R., Safavi-Naeini, A. H. 2019; 6 (7): 845–53
  • Resolving the energy levels of a nanomechanical oscillator. Nature Arrangoiz-Arriola, P., Wollack, E. A., Wang, Z., Pechal, M., Jiang, W., McKenna, T. P., Witmer, J. D., Van Laer, R., Safavi-Naeini, A. H. 2019; 571 (7766): 537–40


    The quantum nature of an oscillating mechanical object is anything but apparent. The coherent states that describe the classical motion of a mechanical oscillator do not have a well defined energy, but are quantum superpositions of equally spaced energy eigenstates. Revealing this quantized structure is only possible with an apparatus that measures energy with a precision greater than the energy of a single phonon. One way to achieve this sensitivity is by engineering a strong but nonresonant interaction between the oscillator and an atom. In a system with sufficient quantum coherence, this interaction allows one to distinguish different energy eigenstates using resolvable differences in the atom's transition frequency. For photons, such dispersive measurements have been performed in cavity1,2 and circuit quantum electrodynamics3. Here we report an experiment in which an artificial atom senses the motional energy of a driven nanomechanical oscillator with sufficient sensitivity to resolve the quantization of its energy. To realize this, we build a hybrid platform that integrates nanomechanical piezoelectric resonators with a microwave superconducting qubit on the same chip. We excite phonons with resonant pulses and probe the resulting excitation spectrum of the qubit to observe phonon-number-dependent frequency shifts that are about five times larger than the qubit linewidth. Our result demonstrates a fully integrated platform for quantum acoustics that combines large couplings, considerable coherence times and excellent control over the mechanical mode structure. With modest experimental improvements, we expect that our approach will enable quantum nondemolition measurements of phonons4 and will lead to quantum sensors and information-processing approaches5 that use chip-scale nanomechanical devices.

    View details for DOI 10.1038/s41586-019-1386-x

    View details for PubMedID 31341303

  • Quantum Dynamics of a Few-Photon Parametric Oscillator PHYSICAL REVIEW X Wang, Z., Pechal, M., Wollack, E., Arrangoiz-Arriola, P., Gao, M., Lee, N. R., Safavi-Naeini, A. H. 2019; 9 (2)
  • Controlling phonons and photons at the wavelength scale: integrated photonics meets integrated phononics (vol 6, pg 213, 2019) OPTICA Safavi-Naeini, A. H., Van Thourhout, D., Baets, R., Van Laer, R. 2019; 6 (4): 410
  • Diamond optomechanical crystals with embedded nitrogen-vacancy centers QUANTUM SCIENCE AND TECHNOLOGY Cady, J., Michel, O., Lee, K. W., Patel, R. N., Sarabalis, C. J., Safavi-Naeini, A. H., Jayich, A. 2019; 4 (2)
  • Time-of-flight imaging based on resonant photoelastic modulation APPLIED OPTICS Atalar, O., Van Laer, R., Sarabalis, C. J., Safavi-Naeini, A. H., Arbabian, A. 2019; 58 (9): 2235–47
  • Controlling phonons and photons at the wavelength scale: integrated photonics meets integrated phononics OPTICA Safavi-Naeini, A. H., Van Thourhout, D., Baets, R., Van Laer, R. 2019; 6 (2): 213–32
  • Superconducting circuit quantum computing with nanomechanical resonators as storage QUANTUM SCIENCE AND TECHNOLOGY Pechal, M., Arrangoiz-Arriola, P., Safavi-Naeini, A. H. 2019; 4 (1)
  • Electro-Optics with Gigahertz Phonons in Silicon Photonics Van Laer, R., Patel, R. N., Witmer, J. D., McKenna, T. P., Safavi-Naeini, A. H., IEEE IEEE. 2019
  • High-quality Lithium Niobate Optomechanical Crystal Jiang, W., Patel, R. N., Mayor, F. M., McKenna, T. P., Arrangoiz-Arriola, P., Sarabalis, C. J., Van Laer, R., Safavi-Naeini, A. H., IEEE IEEE. 2019
  • Quantum Acoustics with Lithium Niobate Nanocavities Arrangoiz-Arriola, P., Wollack, E., Pechal, M., Jiang, W., Wang, Z., McKenna, T. P., Safavi-Naeini, A. H., IEEE IEEE. 2019
  • Frequency Tunable Single-Photon Emission From a Single Atomic Defect in a Solid Sun, S., Zhang, J., Fischer, K. A., Burek, M. J., Dory, C., Lagoudakis, K. G., Tzeng, Y., Radulaski, M., Kelaita, Y., Safavi-Naeini, A., Shen, Z., Melosh, N. A., Chu, S., Loncar, M., Vuckovic, J., IEEE IEEE. 2019
  • Microwave Quantum Acoustic Processor Arrangoiz-Arriola, P., Wollack, E., Pechal, M., Jiang, W., Wang, Z., McKenna, T. P., Witmer, J., Van Laer, R., Cleland, A., Lee, N., Sarabalis, C. J., Stas, P., Safavi-Naeini, A. H., IEEE IEEE. 2019: 255–58
  • Painting Nonclassical States of Spin or Motion with Shaped Single Photons PHYSICAL REVIEW LETTERS Davis, E. J., Wang, Z., Safavi-Naeini, A. H., Schleier-Smith, M. H. 2018; 121 (12)
  • Cavity-Enhanced Raman Emission from a Single Color Center in a Solid. Physical review letters Sun, S., Zhang, J. L., Fischer, K. A., Burek, M. J., Dory, C., Lagoudakis, K. G., Tzeng, Y., Radulaski, M., Kelaita, Y., Safavi-Naeini, A., Shen, Z., Melosh, N. A., Chu, S., Loncar, M., Vuckovic, J. 2018; 121 (8): 083601


    We demonstrate cavity-enhanced Raman emission from a single atomic defect in a solid. Our platform is a single silicon-vacancy center in diamond coupled with a monolithic diamond photonic crystal cavity. The cavity enables an unprecedented frequency tuning range of the Raman emission (100GHz) that significantly exceeds the spectral inhomogeneity of silicon-vacancy centers in diamond nanostructures. We also show that the cavity selectively suppresses the phonon-induced spontaneous emission that degrades the efficiency of Raman photon generation. Our results pave the way towards photon-mediated many-body interactions between solid-state quantum emitters in a nanophotonic platform.

    View details for PubMedID 30192607

  • Optomechanical antennas for on-chip beam-steering OPTICS EXPRESS Sarabalis, C. J., Van Laer, R., Safavi-Naeini, A. H. 2018; 26 (17): 22075–99


    Rapid and low-power control over the direction of a radiating light field is a major challenge in photonics and a key enabling technology for emerging sensors and free-space communication links. Current approaches based on bulky motorized components are limited by their high cost and power consumption, while on-chip optical phased arrays face challenges in scaling and programmability. Here, we propose a solid-state approach to beam-steering using optomechanical antennas. We combine recent progress in simultaneous control of optical and mechanical waves with remarkable advances in on-chip optical phased arrays to enable low-power and full two-dimensional beam-steering of monochromatic light. We present a design of a silicon photonic system made of photonic-phononic waveguides that achieves 44° field of view with 880 resolvable spots by sweeping the mechanical wavelength with about a milliwatt of mechanical power. Using mechanical waves as nonreciprocal, active gratings allows us to quickly reconfigure the beam direction, beam shape, and the number of beams. It also enables us to distinguish between light that we send and receive.

    View details for DOI 10.1364/OE.26.022075

    View details for Web of Science ID 000442136200061

    View details for PubMedID 30130907

  • Single-Mode Phononic Wire PHYSICAL REVIEW LETTERS Patel, R. N., Wang, Z., Jiang, W., Sarabalis, C. J., Hill, J. T., Safavi-Naeini, A. H. 2018; 121 (4)
  • Coupling a Superconducting Quantum Circuit to a Phononic Crystal Defect Cavity PHYSICAL REVIEW X Arrangoiz-Arriola, P., Wollack, E., Pechal, M., Witmer, J. D., Hill, J. T., Safavi-Naeini, A. H. 2018; 8 (3)
  • Single-Mode Phononic Wire. Physical review letters Patel, R. N., Wang, Z., Jiang, W., Sarabalis, C. J., Hill, J. T., Safavi-Naeini, A. H. 2018; 121 (4): 040501


    Photons and electrons transmit information to form complex systems and networks. Phonons on the other hand, the quanta of mechanical motion, are often considered only as carriers of thermal energy. Nonetheless, their flow can also be molded in fabricated nanoscale circuits. We design and experimentally demonstrate wires for phonons by patterning the surface of a silicon chip. Our device eliminates all but one channel of phonon conduction, allowing coherent phonon transport over millimeter length scales. We characterize the phononic wire optically, by coupling it strongly to an optomechanical transducer. The phononic wire enables new ways to manipulate information and energy on a chip. In particular, our result is an important step towards realizing on-chip phonon networks, in which quantum information is transmitted between nodes via phonons.

    View details for PubMedID 30095955

  • Painting Nonclassical States of Spin or Motion with Shaped Single Photons. Physical review letters Davis, E. J., Wang, Z., Safavi-Naeini, A. H., Schleier-Smith, M. H. 2018; 121 (12): 123602


    We propose a robust scheme for generating macroscopic superposition states of spin or motion with the aid of a single photon. Shaping the wave packet of the photon enables high-fidelity preparation of nonclassical states of matter even in the presence of photon loss. Success is heralded by photodetection, enabling the scheme to be implemented with a weak coherent field. We analyze applications to preparing Schrödinger cat states of a collective atomic spin or of a mechanical oscillator coupled to an optical resonator. The method generalizes to preparing arbitrary superpositions of coherent states, enabling full quantum control. We illustrate this versatility by showing how to prepare Dicke or Fock states, as well as superpositions in the Dicke or Fock basis.

    View details for PubMedID 30296158

  • Enhancing a slow and weak optomechanical nonlinearity with delayed quantum feedback NATURE COMMUNICATIONS Wang, Z., Safavi-Naeini, A. H. 2017; 8: 15886


    A central goal of quantum optics is to generate large interactions between single photons so that one photon can strongly modify the state of another one. In cavity optomechanics, photons interact with the motional degrees of freedom of an optical resonator, for example, by imparting radiation pressure forces on a movable mirror or sensing minute fluctuations in the position of the mirror. Here, we show that the optical nonlinearity arising from these effects, typically too small to operate on single photons, can be sufficiently enhanced with feedback to generate large interactions between single photons. We propose a protocol that allows photons propagating in a waveguide to interact with each other through multiple bounces off an optomechanical system. The protocol is analysed by evolving the full many-body quantum state of the waveguide-coupled system, illustrating that large photon-photon interactions mediated by mechanical motion may be within experimental reach.

    View details for PubMedID 28677674

  • High-Q photonic resonators and electro-optic coupling using silicon-on-lithium-niobate SCIENTIFIC REPORTS Witmer, J. D., Valery, J. A., Arrangoiz-Arriola, P., Sarabalis, C. J., Hill, J. T., Safavi-Naeini, A. H. 2017; 7


    Future quantum networks, in which superconducting quantum processors are connected via optical links, will require microwave-to-optical photon converters that preserve entanglement. A doubly-resonant electro-optic modulator (EOM) is a promising platform to realize this conversion. Here, we present our progress towards building such a modulator by demonstrating the optically-resonant half of the device. We demonstrate high quality (Q) factor ring, disk and photonic crystal resonators using a hybrid silicon-on-lithium-niobate material system. Optical Q factors up to 730,000 are achieved, corresponding to propagation loss of 0.8 dB/cm. We also use the electro-optic effect to modulate the resonance frequency of a photonic crystal cavity, achieving a electro-optic modulation coefficient between 1 and 2 pm/V. In addition to quantum technology, we expect that our results will be useful both in traditional silicon photonics applications and in high-sensitivity acousto-optic devices.

    View details for DOI 10.1038/srep46313

    View details for Web of Science ID 000399157100001

    View details for PubMedID 28406177

  • Thermal Brillouin noise observed in silicon optomechanical waveguide JOURNAL OF OPTICS Van Laer, R., Sarabalis, C. J., Baets, R., Van Thourhout, D., Safavi-Naeini, A. H. 2017; 19 (4)
  • Enabling Strong Coupling in Nanoscale Silicon Optomechanical Waveguides Van Laer, R., Safavi-Naeini, A., IEEE IEEE. 2017
  • Engineering interactions between superconducting qubits and phononic nanostructures PHYSICAL REVIEW A Arrangoiz-Arriola, P., Safavi-Naeini, A. H. 2016; 94 (6)
  • Design of nanobeam photonic crystal resonators for a silicon-on-lithium-niobate platform OPTICS EXPRESS Witmer, J. D., Hill, J. T., Safavi-Naeini, A. H. 2016; 24 (6): 5876-5885


    We outline the design for a photonic crystal resonator made in a hybrid Silicon/Lithium Niobate material system. Using the index contrast between silicon and lithium niobate, it is possible to guide and confine photonic resonances in a thin film of silicon bonded on top of lithium niobate. Quality factors greater than 106 at optical wavelength scale mode volumes are achievable. We show that patterning electrodes on such a system can yield an electro-optic coupling rate of 0.6 GHz/V (4 pm/V).

    View details for DOI 10.1364/OE.24.005876

    View details for Web of Science ID 000373395700046

    View details for PubMedID 27136784

  • Nonlinear Radiation Pressure Dynamics in an Optomechanical Crystal PHYSICAL REVIEW LETTERS Krause, A. G., Hill, J. T., Ludwig, M., Safavi-Naeini, A. H., Chan, J., Marquardt, F., Painter, O. 2015; 115 (23)

    View details for DOI 10.1103/PhysRevLett.115.233601

    View details for PubMedID 26684117

  • Phonon counting and intensity interferometry of a nanomechanical resonator NATURE Cohen, J. D., Meenehan, S. M., MacCabe, G. S., Groeblacher, S., Safavi-Naeini, A. H., Marsili, F., Shaw, M. D., Painter, O. 2015; 520 (7548): 522-525


    In optics, the ability to measure individual quanta of light (photons) enables a great many applications, ranging from dynamic imaging within living organisms to secure quantum communication. Pioneering photon counting experiments, such as the intensity interferometry performed by Hanbury Brown and Twiss to measure the angular width of visible stars, have played a critical role in our understanding of the full quantum nature of light. As with matter at the atomic scale, the laws of quantum mechanics also govern the properties of macroscopic mechanical objects, providing fundamental quantum limits to the sensitivity of mechanical sensors and transducers. Current research in cavity optomechanics seeks to use light to explore the quantum properties of mechanical systems ranging in size from kilogram-mass mirrors to nanoscale membranes, as well as to develop technologies for precision sensing and quantum information processing. Here we use an optical probe and single-photon detection to study the acoustic emission and absorption processes in a silicon nanomechanical resonator, and perform a measurement similar to that used by Hanbury Brown and Twiss to measure correlations in the emitted phonons as the resonator undergoes a parametric instability formally equivalent to that of a laser. Owing to the cavity-enhanced coupling of light with mechanical motion, this effective phonon counting technique has a noise equivalent phonon sensitivity of 0.89 ± 0.05. With straightforward improvements to this method, a variety of quantum state engineering tasks using mesoscopic mechanical resonators would be enabled, including the generation and heralding of single-phonon Fock states and the quantum entanglement of remote mechanical elements.

    View details for DOI 10.1038/nature14349

    View details for Web of Science ID 000353334500038

    View details for PubMedID 25903632

  • Strong opto-electro-mechanical coupling in a silicon photonic crystal cavity OPTICS EXPRESS Pitanti, A., Fink, J. M., Safavi-Naeini, A. H., Hill, J. T., Lei, C. U., Tredicucci, A., Painter, O. 2015; 23 (3): 3196-3208
  • Silicon optomechanical crystal resonator at millikelvin temperatures PHYSICAL REVIEW A Meenehan, S. M., Cohen, J. D., Groeblacher, S., Hill, J. T., Safavi-Naeini, A. H., Aspelmeyer, M., Painter, O. 2014; 90 (1)
  • Two-Dimensional Phononic-Photonic Band Gap Optomechanical Crystal Cavity PHYSICAL REVIEW LETTERS Safavi-Naeini, A. H., Hill, J. T., Meenehan, S., Chan, J., Groeblacher, S., Painter, O. 2014; 112 (15)
  • Highly efficient coupling from an optical fiber to a nanoscale silicon optomechanical cavity APPLIED PHYSICS LETTERS Groeblacher, S., Hill, J. T., Safavi-Naeini, A. H., Chan, J., Painter, O. 2013; 103 (18)

    View details for DOI 10.1063/1.4826924

    View details for Web of Science ID 000327816000024

  • Squeezed light from a silicon micromechanical resonator NATURE Safavi-Naeini, A. H., Groeblacher, S., Hill, J. T., Chan, J., Aspelmeyer, M., Painter, O. 2013; 500 (7461): 185-189


    Monitoring a mechanical object's motion, even with the gentle touch of light, fundamentally alters its dynamics. The experimental manifestation of this basic principle of quantum mechanics, its link to the quantum nature of light and the extension of quantum measurement to the macroscopic realm have all received extensive attention over the past half-century. The use of squeezed light, with quantum fluctuations below that of the vacuum field, was proposed nearly three decades ago as a means of reducing the optical read-out noise in precision force measurements. Conversely, it has also been proposed that a continuous measurement of a mirror's position with light may itself give rise to squeezed light. Such squeezed-light generation has recently been demonstrated in a system of ultracold gas-phase atoms whose centre-of-mass motion is analogous to the motion of a mirror. Here we describe the continuous position measurement of a solid-state, optomechanical system fabricated from a silicon microchip and comprising a micromechanical resonator coupled to a nanophotonic cavity. Laser light sent into the cavity is used to measure the fluctuations in the position of the mechanical resonator at a measurement rate comparable to its resonance frequency and greater than its thermal decoherence rate. Despite the mechanical resonator's highly excited thermal state (10(4) phonons), we observe, through homodyne detection, squeezing of the reflected light's fluctuation spectrum at a level 4.5 ± 0.2 per cent below that of vacuum noise over a bandwidth of a few megahertz around the mechanical resonance frequency of 28 megahertz. With further device improvements, on-chip squeezing at significant levels should be possible, making such integrated microscale devices well suited for precision metrology applications.

    View details for DOI 10.1038/nature12307

    View details for Web of Science ID 000322825500030

    View details for PubMedID 23925241

  • Laser noise in cavity-optomechanical cooling and thermometry NEW JOURNAL OF PHYSICS Safavi-Naeini, A. H., Chan, J., Hill, J. T., Groeblacher, S., Miao, H., Chen, Y., Aspelmeyer, M., Painter, O. 2013; 15
  • Si3N4 nanobeam optomechanical crystals 2013 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) Davanco, M., Chan, J., Safavi-Naeini, A. H., Painter, O., Srinivasan, K. 2013
  • Coherent optical wavelength conversion via cavity optomechanics NATURE COMMUNICATIONS Hill, J. T., Safavi-Naeini, A. H., Chan, J., Painter, O. 2012; 3


    Both classical and quantum systems utilize the interaction of light and matter across a wide range of energies. These systems are often not naturally compatible with one another and require a means of converting photons of dissimilar wavelengths to combine and exploit their different strengths. Here we theoretically propose and experimentally demonstrate coherent wavelength conversion of optical photons using photon-phonon translation in a cavity-optomechanical system. For an engineered silicon optomechanical crystal nanocavity supporting a 4-GHz localized phonon mode, optical signals in a 1.5 MHz bandwidth are coherently converted over a 11.2 THz frequency span between one cavity mode at wavelength 1,460 nm and a second cavity mode at 1,545 nm with a 93% internal (2% external) peak efficiency. The thermal- and quantum-limiting noise involved in the conversion process is also analysed, and in terms of an equivalent photon number signal level are found to correspond to an internal noise level of only 6 and 4 × 10(-3) quanta, respectively.

    View details for DOI 10.1038/ncomms2201

    View details for Web of Science ID 000315992100031

    View details for PubMedID 23149741

  • Slot-mode-coupled optomechanical crystals OPTICS EXPRESS Davanco, M., Chan, J., Safavi-Naeini, A. H., Painter, O., Srinivasan, K. 2012; 20 (22): 24394-24410


    We present a design methodology and analysis of a cavity optomechanical system in which a localized GHz frequency mechanical mode of a nanobeam resonator is evanescently coupled to a high quality factor (Q > 10(6)) optical mode of a separate nanobeam optical cavity. Using separate nanobeams provides flexibility, enabling the independent design and optimization of the optics and mechanics of the system. In addition, the small gap (≈ 25 nm) between the two resonators gives rise to a slot mode effect that enables a large zero-point optomechanical coupling strength to be achieved, with g/2 π > 300 kHz in a Si(3)N(4) system at 980 nm and g/2 π ≈ 900 kHz in a Si system at 1550 nm. The fact that large coupling strengths to GHz mechanical oscillators can be achieved in Si(3)N(4) is important, as this material has a broad optical transparency window, which allows operation throughout the visible and near-infrared. As an application of this platform, we consider wide-band optical frequency conversion between 1300 nm and 980 nm, using two optical nanobeam cavities coupled on either side to the breathing mode of a mechanical nanobeam resonator.

    View details for DOI 10.1364/OE.20.024394

    View details for Web of Science ID 000310443400032

    View details for PubMedID 23187203

  • Quantum back-action in measurements of zero-point mechanical oscillations PHYSICAL REVIEW A Khalili, F. Y., Miao, H., Yang, H., Safavi-Naeini, A. H., Painter, O., Chen, Y. 2012; 86 (3)
  • Optimized optomechanical crystal cavity with acoustic radiation shield APPLIED PHYSICS LETTERS Chan, J., Safavi-Naeini, A. H., Hill, J. T., Meenehan, S., Painter, O. 2012; 101 (8)

    View details for DOI 10.1063/1.4747726

    View details for Web of Science ID 000308420800015

  • Enhanced Quantum Nonlinearities in a Two-Mode Optomechanical System PHYSICAL REVIEW LETTERS Ludwig, M., Safavi-Naeini, A. H., Painter, O., Marquardt, F. 2012; 109 (6)


    In cavity optomechanics, nanomechanical motion couples to a localized optical mode. The regime of single-photon strong coupling is reached when the optical shift induced by a single phonon becomes comparable to the cavity linewidth. We consider a setup in this regime comprising two optical modes and one mechanical mode. For mechanical frequencies nearly resonant to the optical level splitting, we find the photon-phonon and the photon-photon interactions to be significantly enhanced. In addition to dispersive phonon detection in a novel regime, this offers the prospect of optomechanical photon measurement. We study these quantum nondemolition detection processes using both analytical and numerical approaches.

    View details for DOI 10.1103/PhysRevLett.109.063601

    View details for Web of Science ID 000307283300005

    View details for PubMedID 23006265

  • Observation of Quantum Motion of a Nanomechanical Resonator PHYSICAL REVIEW LETTERS Safavi-Naeini, A. H., Chan, J., Hill, J. T., Alegre, T. P., Krause, A., Painter, O. 2012; 108 (3)


    In this Letter we use resolved sideband laser cooling to cool a mesoscopic mechanical resonator to near its quantum ground state (phonon occupancy 2.6±0.2), and observe the motional sidebands generated on a second probe laser. Asymmetry in the sideband amplitudes provides a direct measure of the displacement noise power associated with quantum zero-point fluctuations of the nanomechanical resonator, and allows for an intrinsic calibration of the phonon occupation number.

    View details for DOI 10.1103/PhysRevLett.108.033602

    View details for Web of Science ID 000299328100002

    View details for PubMedID 22400740

  • A chip-scale integrated cavity-electro-optomechanics platform OPTICS EXPRESS Winger, M., Blasius, T. D., Alegre, T. P., Safavi-Naeini, A. H., Meenehan, S., Cohen, J., Stobbe, S., Painter, O. 2011; 19 (25): 24905-24921


    We present an integrated optomechanical and electromechanical nanocavity, in which a common mechanical degree of freedom is coupled to an ultrahigh-Q photonic crystal defect cavity and an electrical circuit. The system allows for wide-range, fast electrical tuning of the optical nanocavity resonances, and for electrical control of optical radiation pressure back-action effects such as mechanical amplification (phonon lasing), cooling, and stiffening. These sort of integrated devices offer a new means to efficiently interconvert weak microwave and optical signals, and are expected to pave the way for a new class of micro-sensors utilizing optomechanical back-action for thermal noise reduction and low-noise optical read-out.

    View details for DOI 10.1364/OE.19.024905

    View details for Web of Science ID 000297702400008

    View details for PubMedID 22273884

  • Laser cooling of a nanomechanical oscillator into its quantum ground state. Nature Chan, J., Alegre, T. P., Safavi-Naeini, A. H., Hill, J. T., Krause, A., Gröblacher, S., Aspelmeyer, M., Painter, O. 2011; 478 (7367): 89-92


    The simple mechanical oscillator, canonically consisting of a coupled mass-spring system, is used in a wide variety of sensitive measurements, including the detection of weak forces and small masses. On the one hand, a classical oscillator has a well-defined amplitude of motion; a quantum oscillator, on the other hand, has a lowest-energy state, or ground state, with a finite-amplitude uncertainty corresponding to zero-point motion. On the macroscopic scale of our everyday experience, owing to interactions with its highly fluctuating thermal environment a mechanical oscillator is filled with many energy quanta and its quantum nature is all but hidden. Recently, in experiments performed at temperatures of a few hundredths of a kelvin, engineered nanomechanical resonators coupled to electrical circuits have been measured to be oscillating in their quantum ground state. These experiments, in addition to providing a glimpse into the underlying quantum behaviour of mesoscopic systems consisting of billions of atoms, represent the initial steps towards the use of mechanical devices as tools for quantum metrology or as a means of coupling hybrid quantum systems. Here we report the development of a coupled, nanoscale optical and mechanical resonator formed in a silicon microchip, in which radiation pressure from a laser is used to cool the mechanical motion down to its quantum ground state (reaching an average phonon occupancy number of 0.85 ± 0.08). This cooling is realized at an environmental temperature of 20 K, roughly one thousand times larger than in previous experiments and paves the way for optical control of mesoscale mechanical oscillators in the quantum regime.

    View details for DOI 10.1038/nature10461

    View details for PubMedID 21979049

  • Laser cooling of a nanomechanical oscillator into its quantum ground state NATURE Chan, J., Mayer Alegre, T. P., Safavi-Naeini, A. H., Hill, J. T., Krause, A., Groeblacher, S., Aspelmeyer, M., Painter, O. 2011; 478 (7367): 89-92
  • Electromagnetically induced transparency and slow light with optomechanics NATURE Safavi-Naeini, A. H., Alegre, T. P., Chan, J., Eichenfield, M., Winger, M., Lin, Q., Hill, J. T., Chang, D. E., Painter, O. 2011; 472 (7341): 69-73


    Controlling the interaction between localized optical and mechanical excitations has recently become possible following advances in micro- and nanofabrication techniques. So far, most experimental studies of optomechanics have focused on measurement and control of the mechanical subsystem through its interaction with optics, and have led to the experimental demonstration of dynamical back-action cooling and optical rigidity of the mechanical system. Conversely, the optical response of these systems is also modified in the presence of mechanical interactions, leading to effects such as electromagnetically induced transparency (EIT) and parametric normal-mode splitting. In atomic systems, studies of slow and stopped light (applicable to modern optical networks and future quantum networks) have thrust EIT to the forefront of experimental study during the past two decades. Here we demonstrate EIT and tunable optical delays in a nanoscale optomechanical crystal, using the optomechanical nonlinearity to control the velocity of light by way of engineered photon-phonon interactions. Our device is fabricated by simply etching holes into a thin film of silicon. At low temperature (8.7 kelvin), we report an optically tunable delay of 50 nanoseconds with near-unity optical transparency, and superluminal light with a 1.4 microsecond signal advance. These results, while indicating significant progress towards an integrated quantum optomechanical memory, are also relevant to classical signal processing applications. Measurements at room temperature in the analogous regime of electromagnetically induced absorption show the utility of these chip-scale optomechanical systems for optical buffering, amplification, and filtering of microwave-over-optical signals.

    View details for DOI 10.1038/nature09933

    View details for Web of Science ID 000289199400038

    View details for PubMedID 21412237

  • Quasi-two-dimensional optomechanical crystals with a complete phononic bandgap OPTICS EXPRESS Alegre, T. P., Safavi-Naeini, A., Winger, M., Painter, O. 2011; 19 (6): 5658-5669


    A fully planar two-dimensional optomechanical crystal formed in a silicon microchip is used to create a structure devoid of phonons in the GHz frequency range. A nanoscale photonic crystal cavity is placed inside the phononic bandgap crystal in order to probe the properties of the localized acoustic modes. By studying the trends in mechanical damping, mode density, and optomechanical coupling strength of the acoustic resonances over an array of structures with varying geometric properties, clear evidence of a complete phononic bandgap is shown.

    View details for Web of Science ID 000288871300106

    View details for PubMedID 21445206

  • Slowing and stopping light using an optomechanical crystal array NEW JOURNAL OF PHYSICS Chang, D. E., Safavi-Naeini, A. H., Hafezi, M., Painter, O. 2011; 13
  • Proposal for an optomechanical traveling wave phonon-photon translator NEW JOURNAL OF PHYSICS Safavi-Naeini, A. H., Painter, O. 2011; 13
  • Tunable 2D Photonic Crystal Cavities for Cavity Electro-Optomechanics 2011 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) Winger, M., Alegre, T. P., Safavi-Naeini, A. H., Painter, O. 2011
  • Full Phononic Bandgap in 2D-Optomechanical Crystals 2011 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) Alegre, T. P., Safavi-Naeini, A. H., Winger, M., Painter, O. 2011
  • Optomechanics in an ultrahigh-Q two-dimensional photonic crystal cavity APPLIED PHYSICS LETTERS Safavi-Naeini, A. H., Alegre, T. P., Winger, M., Painter, O. 2010; 97 (18)

    View details for DOI 10.1063/1.3507288

    View details for Web of Science ID 000283934100006

  • Design of optomechanical cavities and waveguides on a simultaneous bandgap phononic-photonic crystal slab OPTICS EXPRESS Safavi-Naeini, A. H., Painter, O. 2010; 18 (14): 14926-14943


    In this paper we study and design quasi-2D optomechanical crystals, waveguides, and resonant cavities formed from patterned slabs. Two-dimensional periodicity allows for in-plane pseudo-bandgaps in frequency where resonant optical and mechanical excitations localized to the slab are forbidden. By tailoring the unit cell geometry, we show that it is possible to have a slab crystal with simultaneous optical and mechanical pseudo-bandgaps, and for which optical waveguiding is not compromised. We then use these crystals to design optomechanical cavities in which strongly interacting, co-localized photonic-phononic resonances occur. A resonant cavity structure formed by perturbing a ;;linear defect' waveguide of optical and acoustic waves in a silicon optomechanical crystal slab is shown to support an optical resonance at wavelength lambda(0) approximately 1.5 mum and a mechanical resonance of frequency omega(m)/2pi approximately 9.5 GHz. These resonances, due to the simultaneous pseudo-bandgap of the waveguide structure, are simulated to have optical and mechanical radiation-limited Q-factors greater than 10(7). The optomechanical coupling of the optical and acousticresonances in this cavity due to radiation pressure is also studied, with a quantum conversion rate, corresponding to the scattering rate of a single cavity photon via a single cavity phonon, calculated to be g/2pi = 292 kHz.

    View details for DOI 10.1364/OE.18.014926

    View details for Web of Science ID 000279639900065

    View details for PubMedID 20639979

  • Optical Probing and Actuation of Microwave Frequency Phononic Crystal Resonators without Clamping Losses 2010 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS) Eichenfield, M., Chan, J., Safavi-Naeini, A. H., Painter, O. J. 2010
  • Slowing and stopping light with an optomechanical crystal array THIRD INTERNATIONAL WORKSHOP ON THEORETICAL AND COMPUTATIONAL NANOPHOTONICS - TACONA-PHOTONICS 2010 Chang, D. E., Safavi-Naeini, A. H., Hafezi, M., Painter, O. 2010; 1291: 13-17
  • Efficient On-Chip Phonon-Photon Translation 2010 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS) Safavi-Naeini, A. H., Alegre, T. P., Painter, O. J. 2010
  • Surface-plasmon mode hybridization in subwavelength microdisk lasers APPLIED PHYSICS LETTERS Perahia, R., Alegre, T. P., Safavi-Naeini, A. H., Painter, O. 2009; 95 (20)

    View details for DOI 10.1063/1.3266843

    View details for Web of Science ID 000272052200014

  • Modeling dispersive coupling and losses of localized optical and mechanical modes in optomechanical crystals OPTICS EXPRESS Eichenfield, M., Chan, J., Safavi-Naeini, A. H., Vahala, K. J., Painter, O. 2009; 17 (22): 20078-20098


    Periodically structured materials can sustain both optical and mechanical excitations which are tailored by the geometry. Here we analyze the properties of dispersively coupled planar photonic and phononic crystals: optomechanical crystals. In particular, the properties of co-resonant optical and mechanical cavities in quasi-1D (patterned nanobeam) and quasi-2D (patterned membrane) geometries are studied. It is shown that the mechanical Q and optomechanical coupling in these structures can vary by many orders of magnitude with modest changes in geometry. An intuitive picture is developed based upon a perturbation theory for shifting material boundaries that allows the optomechanical properties to be designed and optimized. Several designs are presented with mechanical frequency approximately 1-10 GHz, optical Q-factor Qo > 107, motional masses meff approximately 100 femtograms, optomechanical coupling length LOM < 5 microm, and clampinig losses that are exponentially suppressed with increasing number of phononic crystal periods (radiation-limited mechanical Q-factor Qm > 107 for total device size less than 30 microm).

    View details for DOI 10.1364/OE.17.020078

    View details for Web of Science ID 000271629200080

    View details for PubMedID 19997232

  • Surface Plasmon Waveguide Mode Hybridization and Lasing in Sub-wavelength Microdisks at 1.3 mu m 2009 CONFERENCE ON LASERS AND ELECTRO-OPTICS AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (CLEO/QELS 2009), VOLS 1-5 Perahia, R., Alegre, T. P., Safavi-Naeini, A., Painter, O. 2009: 3232-3233