Academic Appointments

Professional Education

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


  • 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

2017-18 Courses

Stanford Advisees

All Publications

  • 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)
  • 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)
  • 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