Dalziel Wilson

Interests

Research

I lead an experimental group in the field of cavity optomechanics. We are interested in measuring weak forces using ultra-high-Q nanomechanical resonators coupled to optical cavities. Applications include development of quantum-enhanced (via squeezed light, e.g.) force and inertial sensors, studying the quantum limits of measurement and feedback control, and searching for fundamental weak signals including spontaneous waveform collapse and dark matter forces. I am particularly interested in ultralight dark matter detection, as a convergent science goal and as a springboard for developing and studying quantum-limited optomechanical sensor arrays. Central to all of these goals is the development of ultra-high-Q nanomechanical resonators. We dedicate a significant amount of time to this engineering/nanofabrication effort as well.

Teaching

I created a 10 week course on Cavity Optomechanics (OPTI-600KL) starting in the Spring Semester of 2018. I have also taught the Advanced Laser Lab (OPTI-511L) and Laser Beams and Resonators (OPTI-600G). In Spring 2020 I will begin teaching Physical Optics (OPTI-210). I would also like to teach a course on technical writing.

Courses

Scholarly Contributions

Books

• Wilson, D. J. (2012). Cavity Optomechanics with High Stress Silicon Nitride Films. doi:10.7907/VB3C-1G76.
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  There has been a barrage of interest in recent years to marry the fields of nanomechanics and quantum optics. Mechanical systems provide sensitive and scalable architectures for sensing applications ranging from atomic force microscopy to gravity wave interferometry. Optical resonators driven by low noise lasers provide a quiet and well-understood means to read-out and manipulate mechanical motion, by way of the radiation pressure force. Taken to an extreme, a device consisting of a high-Q nanomechanical oscillator coupled to a high-finesse optical cavity may enable ground-state preparation of the mechanical element, thus paving the way for a new class of quantum technology based on chip-scale phononic devices coupled to optical photons. By way of mutual coupling to the optical field, this architecture may enable coupling of single phonons to real or artificial atoms, an enticing prospect because of the vast "quantum optics toolbox" already developed for cavity quantum electrodynamics. The first step towards these goals --- ground-state cooling of the mechanical element in a "cavity optomechanical" system --- has very recently been realized in a cryogenic setup. The work presented in this thesis describes an effort to extend this capability to a room temperature apparatus, so that the usual panoply of table-top optical/atomic physics tools can be brought to bear. This requires a mechanical oscillator with exceptionally low dissipation, as well as careful attention to extraneous sources of noise in both the optical and mechanical componentry. Our particular system is based on a high-Q, high-stress silicon nitride membrane coupled to a high-finesse Fabry-Perot cavity. The purpose of this thesis is to record in detail the procedure for characterizing/modeling the physical properties of the membrane resonator, the optical cavity, and their mutual interaction, as well as extraneous sources of noise related to multimode thermal motion of the oscillator, thermal motion of the cavity apparatus, optical absorption, and laser phase fluctuations. Our principle experimental result is the radiation pressure-based cooling of a high order, 4.8 MHz drum mode of the membrane from room temperature to ~ 100 mK (~ 500 phonons). Secondary results include an investigation of the Q-factor of membrane oscillators with various geometries, some of which exhibit state-of-the-art Q x frequency products of 3 x 10^13 Hz, and a novel technique to suppress extraneous radiation pressure noise using electro-optic feedback.

Journals/Publications

• , J. R., , A. R., , C. A., , C. M., , S. S., & , D. J. (2022). Nanoscale torsional dissipation dilution for quantum experiments and precision measurement.
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  We show that torsion resonators can experience massive dissipation dilutiondue to nanoscale strain, and draw a connection to a century-old theory from thetorsion balance community which suggests that a simple torsion ribbon isnaturally soft-clamped. By disrupting a commonly held belief in thenanomechanics community, our findings invite a rethinking of strategies towardsquantum experiments and precision measurement with nanomechanical resonators.For example, we revisit the optical lever technique for monitoringdisplacement, and find that the rotation of a strained nanobeam can be resolvedwith an imprecision smaller than the zero-point motion of its fundamentaltorsional mode, without the use of a cavity or interferometric stability. Wealso find that a strained torsion ribbon can be mass-loaded without changingits $Q$ factor. We use this strategy to engineer a chip-scale torsion balancewhose resonance frequency is sensitive to micro-$g$ fluctuations of the localgravitational field. Enabling both these advances is the fabrication ofhigh-stress Si$_3$N$_4$ nanobeams with width-to-thickness ratios of $10^4$ andthe recognition that their torsional modes have $Q$ factors scaling as theirwidth-to-thickness ratio squared, yielding $Q$ factors as high as $10^8$ and$Q$-frequency products as high as $10^{13}$ Hz.[Journal_ref: ]
• Carney, D., Krnjaic, G., Moore, D. C., Regal, C. A., Afek, G., Bhave, S., Brubaker, B., Corbitt, T., Cripe, J., Crisosto, N., & others, . (2021). Mechanical quantum sensing in the search for dark matter. Quantum Science and Technology, 6(2), 024002.
• Wilson, D. J. (2021). Optomechanical sensors as probes for new physics. Bulletin of the American Physical Society.
• Wilson, D. J., Pluchar, C. M., & Agrawal, A. (2021). Towards observation of radiation pressure shot noise at acoustic frequencies. Bulletin of the American Physical Society.
• Agrawal, A., Schenk, E., Schenk, E., Wilson, D. J., & Pluchar, C. M. (2020). A compact trampoline-in-the-middle system for acoustic frequency quantum optomechanics. Bulletin of the American Physical Society.
• Wilson, D. (2020). Searching for scalar dark matter with compact mechanical resonators. Physical Review Letters.
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  We explore the viability of laboratory-scale mechanical resonators asdetectors for ultralight scalar dark matter. The signal we investigate is anatomic strain due to modulation of the fine structure constant and the leptonmass at the Compton frequency of dark matter particles. The resulting stresscan drive an elastic body with acoustic breathing modes, producingdisplacements that are accessible with opto- or electromechanical readouttechniques. To address the unknown mass of dark matter particles (whichdetermines their Compton frequency), we consider various resonator designsoperating at kHz to MHz frequencies, corresponding to $10^{-12}-10^{-5}$ eVparticle mass. Current resonant-mass gravitational wave detectors that havebeen repurposed as dark matter detectors weigh $\sim \! 10^3$ kg. We find thata large unexplored parameter space can be accessed with ultra-high-$Q$,cryogenically-cooled, cm-scale mechanical resonators possessing $\sim \! 10^7$times smaller mass.[Journal_ref: ]
• Wilson, D. J., Kippenberg, T. J., Fedorov, S. A., Engelsen, N. J., Beccari, A., & Arabmoheghi, A. (2020). Thermal intermodulation noise in cavity-based measurements. Optica, 7(11), 1609-1616. doi:10.1364/optica.402449
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  Thermal frequency fluctuations in optical cavities limit the sensitivity of precision experiments ranging from gravitational wave observatories to optical atomic clocks. Conventional modeling of these noises assumes a linear response of the optical field to the fluctuations of cavity frequency. Fundamentally, however, this response is nonlinear. Here we show that nonlinearly transduced thermal fluctuations of cavity frequency can dominate the broadband noise in photodetection, even when the magnitude of fluctuations is much smaller than the cavity linewidth. We term this noise “thermal intermodulation noise” and show that for a resonant laser probe it manifests as intensity fluctuations. We report and characterize thermal intermodulation noise in an optomechanical cavity, where the frequency fluctuations are caused by mechanical Brownian motion, and find excellent agreement with our developed theoretical model. We demonstrate that the effect is particularly relevant to quantum optomechanics: using a phononic crystal Si3N4 membrane with a low-mass, soft-clamped mechanical mode, we are able to operate in the regime where measurement quantum backaction contributes as much force noise as the thermal environment does. However, in the presence of intermodulation noise, quantum signatures of measurement are not revealed in direct photodetection. The reported noise mechanism, while studied for an optomechanical system, can exist in any optical cavity.
• Wilson, D. J., Schneider, K., Hoenl, S., Anderson, M., Baumgartner, Y., Czornomaz, L., Kippenberg, T. J., & Seidler, P. (2020). Integrated gallium phosphide nonlinear photonics. NATURE PHOTONICS, 14(1), 57-+.
• Wilson, D., Pluchar, C., & Agraway, A. (2020). Towards Cavity-Free Ground State Cooling of an Acoustic Frequency Silicon Nitride Membrane. Applied Optics.
• Wilson, D., Singh, S., Chowdury, M. D., & Manley, J. (2021). Searching for Vector Dark Matter with an Optomechanical Accelerometer. Physical Review Letters.
• Bereyhi, M. J., Beccari, A., Fedorov, S. A., Ghadimi, A. H., Schilling, R., Wilson, D. J., Engelsen, N. J., & Kippenberg, T. J. (2019). Clamp-Tapering Increases the Quality Factor of Stressed Nanobeams. NANO LETTERS, 19(4), 2329-2333.
• Engelsen, N. J., Fedorov, S. A., Ghadimi, A. H., Bereyhi, M. J., Beccari, A., Schilling, R., Wilson, D. J., & Kippenberg, T. J. (2019). Ultralow Dissipation Mechanical Resonators for Quantum Optomechanics. 2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO).
• Fedorov, S. A., Engelsen, N. J., Ghadimi, A. H., Bereyhi, M. J., Schilling, R., Wilson, D. J., & Kippenberg, T. J. (2019). Generalized dissipation dilution in strained mechanical resonators. Physical Review B, 99(5). doi:10.1103/physrevb.99.054107
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  Mechanical resonators with high quality factors are widely used in precision experiments, ranging from gravitational wave detection and force sensing to quantum optomechanics. Beams and membranes are well known to exhibit flexural modes with enhanced quality factors when subjected to tensile stress. The mechanism for this enhancement has been a subject of debate, but is typically attributed to elastic energy being ``diluted'' by a lossless potential. Here we clarify the origin of the lossless potential to be the combination of tension and geometric nonlinearity of strain. We present a general theory of dissipation dilution that is applicable to arbitrary resonator geometries and discuss why this effect is particularly strong for flexural modes of nanomechanical structures with high aspect ratios. Applying the theory to a nonuniform doubly clamped beam, we show analytically how dissipation dilution can be enhanced by modifying the beam shape to implement ``soft clamping,'' thin clamping, and geometric strain engineering, and derive the ultimate limit for dissipation dilution.
• Schneider, K., Baumgartner, Y., Honl, S., Welter, P., Hahn, H., Wilson, D. J., Czornomaz, L., & Seidler, P. (2019). Optomechanics with one-dimensional gallium phosphide photonic crystal cavities. OPTICA, 6(5), 577-584.
• Wilson, D. J., Honl, S., Schneider, K., Anderson, M., Kippenberg, T. J., & Seidler, P. (2018). Gallium Phosphide Microresonator Frequency Combs. Frontiers in Optics. doi:10.1364/fio.2018.fth3c.6
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  We demonstrate the first microresonator frequency combs in GaP, a III-V semiconductor transparent above 549 nm. High Kerr nonlinearity (~10−17 m2/W) yields THz combs at 1550 nm with a 3-mW power threshold and >100-nm bandwidth.
• Ghadimi, A. H., Wilson, D. J., & Kippenberg, T. J. (2017). Radiation and Internal Loss Engineering of High-Stress Silicon Nitride Nanobeams.. Nano letters, 17(6), 3501-3505. doi:10.1021/acs.nanolett.7b00573
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  High-stress Si3N4 nanoresonators have become an attractive choice for electro- and optomechanical devices. Membrane resonators can achieve quality factor (Q)-frequency (f) products exceeding 1013 Hz, enabling (in principle) quantum coherent operation at room temperature. String-like beam resonators possess smaller Q × f products; however, on account of their significantly lower mass and mode density, they remain a canonical choice for precision force, mass, and charge sensing, and have recently enabled Heisenberg-limited position measurements at cryogenic temperatures. Here we explore two techniques to enhance the Q of a nanomechanical beam. The techniques relate to two main loss mechanisms: internal loss, which dominates for high aspect ratios and f ≲ 100 MHz, and radiation loss, which dominates for low aspect ratios and f ≳ 100 MHz. First, we show that by embedding a nanobeam in a 1D phononic crystal (PnC), it is possible to localize its flexural motion and shield it against radiation loss. Using this method, we realize f > 100 MHz modes with Q ≈ 104, consistent with internal loss and contrasting sharply with unshielded beams of similar dimensions. We then study the Q × f product of high-order modes of millimeter-long nanobeams. Taking advantage of the mode-shape dependence of stress-induced "loss dilution", we realize a f ≈ 4 MHz mode with Q × f ≈ 9 × 1012 Hz. Our results complement recent work on PnC-based "soft-clamping" of nanomembranes, in which mode localization is used to enhance loss dilution. Combining these strategies should enable ultra-low-mass nanobeam oscillators that operate deep in the quantum coherent regime at room temperature.
• Wilson, D. J., Sudhir, V., Schutz, H., Schilling, R., Kippenberg, T. J., & Fedorov, S. A. (2017). Quantum Correlations of Light from a Room-Temperature Mechanical Oscillator. Physical Review X, 7(3). doi:10.1103/physrevx.7.031055
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  When light reflects off a mirror, its intensity and phase become quantum correlated as a result of radiation pressure. These correlations could be used to erase quantum backaction, which poses a fundamental limit to the precision of interferometric displacement measurements. For the first time, these correlations are observed and exploited in a room-temperature interferometer, which could lead to advances in quantum-enhanced metrology.
• Wilson, D. J., Sudhir, V., Schutz, H., Schilling, R., Nunnenkamp, A., Kippenberg, T. J., Ghadimi, A. H., & Fedorov, S. A. (2017). Appearance and Disappearance of Quantum Correlations in Measurement-Based Feedback Control of a Mechanical Oscillator. Physical Review X, 7(1). doi:10.1103/physrevx.7.011001
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  One challenge of controlling quantum systems is striking a balance between the random disturbances caused by the act of measurement and stabilizing the system in a desired state. Researchers conduct an experiment in the so-called ``quantum feedback regime'' in which the disturbance due to a measurement is suppressed.
• Okamoto, H., Schilling, R., Schutz, H., Sudhir, V., Wilson, D. J., Yamaguchi, H., & Kippenberg, T. J. (2016). A strongly coupled Λ-type micromechanical system. Applied Physics Letters, 108(15), 153105. doi:10.1063/1.4945741
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  We study a classical Λ-type three-level system based on three high-Q micromechanical beam resonators embedded in a gradient electric field. By modulating the strength of the field at the difference frequency between adjacent beam modes, we realize strong dynamic two-mode coupling, via the dielectric force. Driving adjacent pairs simultaneously, we observe the formation of a purely mechanical “dark” state and an all-phononic analog of coherent population trapping—signatures of strong three-mode coupling. The Λ-type micromechanical system is a natural extension of previously demonstrated “two-level” micromechanical systems and adds to the toolbox for engineering of all-phononic micromechanical circuits and arrays.
• Sudhir, V., Wilson, D. J., Schilling, R., Schuetz, H., Nunnenkamp, A., & Kippenberg, T. J. (2016). Appearance and disappearance of motional sideband asymmetry in measurement-based control of a mechanical oscillator. Bulletin of the American Physical Society.
• Sudhir, V., Wilson, D. J., Schuetz, H., Schilling, R., Nunnenkamp, A., Kippenberg, T. J., Ghadimi, A. H., & Fedorov, S. A. (2016). Quantum correlations in measurement-based control of a mechanical oscillator. Frontiers in Optics. doi:10.1364/fio.2016.ff3d.6
• Wilson, D. J., Sudhir, V., Schutz, H., Schilling, R., Kippenberg, T. J., & Ghadimi, A. H. (2016). Near-Field Integration of a SiN Nanobeam and a SiO 2 Microcavity for Heisenberg-Limited Displacement Sensing. Physical review applied, 5(5). doi:10.1103/physrevapplied.5.054019
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  Placing a nanomechanical object in the evanescent near field of a high-Q optical microcavity gives access to strong gradient forces and quantum-limited displacement readout, offering an attractive platform for both precision sensing technology and basic quantum optics research. Robustly implementing this platform is challenging, however, as it requires integrating optically smooth surfaces separated by less than or similar to lambda/10. Here we describe an exceptionally high-cooperativity, single-chip optonanomechanical transducer based on a high-stress Si3N4 nanobeam monolithically integrated into the evanescent near field of SiO2 microdisk cavity. Employing a vertical integration technique based on planarized sacrificial layers, we realize beam-disk gaps as little as 25 nm while maintaining mechanical Qf > 10(12) Hz and intrinsic optical Q similar to 10(7). The combination of low loss, small gap, and parallel-plane geometry results in radio-frequency flexural modes with vacuum optomechanical coupling rates of 100 kHz, single-photon cooperativities in excess of unity, and large zero-point frequency (displacement) noise amplitudes of 10 kHz (fm) / root Hz. In conjunction with the high power-handling capacity of SiO2 and low extraneous substrate noise, the transducer performs particularly well as a sensor, with recent deployment in a 4-K cryostat realizing a displacement imprecision 40 dB below that at the standard quantum limit (SQL) and an imprecision-backaction product < 5h [Wilson et al., Nature (London) 524, 325 (2015)]. In this report, we provide a comprehensive description of device design, fabrication, and characterization, with an emphasis on extending Heisenberg-limited readout to room temperature. Towards this end, we describe a roomtemperature experiment in which a displacement imprecision 32 dB below that at the SQL and an imprecision-backaction product < 60h is achieved. Our results extend the outlook for measurement-based quantum control of nanomechanical oscillators and suggest an alternative platform for functionally integrated "hybrid" quantum optomechanics.
• Wilson, D. J., Sudhir, V., Piro, N., Schilling, R., Ghadimi, A. H., & Kippenberg, T. J. (2015). Measurement and control of a mechanical oscillator at its thermal decoherence rate. Bulletin of the American Physical Society.
• Wilson, D. J., Sudhir, V., Piro, N., Schilling, R., Kippenberg, T. J., & Ghadimi, A. H. (2015). Measurement-based control of a mechanical oscillator at its thermal decoherence rate.. Nature, 524(7565), 325-9. doi:10.1038/nature14672
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  In real-time quantum feedback protocols, the record of a continuous measurement is used to stabilize a desired quantum state. Recent years have seen successful applications of these protocols in a variety of well-isolated micro-systems, including microwave photons and superconducting qubits. However, stabilizing the quantum state of a tangibly massive object, such as a mechanical oscillator, remains very challenging: the main obstacle is environmental decoherence, which places stringent requirements on the timescale in which the state must be measured. Here we describe a position sensor that is capable of resolving the zero-point motion of a solid-state, 4.3-megahertz nanomechanical oscillator in the timescale of its thermal decoherence, a basic requirement for real-time (Markovian) quantum feedback control tasks, such as ground-state preparation. The sensor is based on evanescent optomechanical coupling to a high-Q microcavity, and achieves an imprecision four orders of magnitude below that at the standard quantum limit for a weak continuous position measurement--a 100-fold improvement over previous reports--while maintaining an imprecision-back-action product that is within a factor of five of the Heisenberg uncertainty limit. As a demonstration of its utility, we use the measurement as an error signal with which to feedback cool the oscillator. Using radiation pressure as an actuator, the oscillator is cold damped with high efficiency: from a cryogenic-bath temperature of 4.4 kelvin to an effective value of 1.1 ± 0.1 millikelvin, corresponding to a mean phonon number of 5.3 ± 0.6 (that is, a ground-state probability of 16 per cent). Our results set a new benchmark for the performance of a linear position sensor, and signal the emergence of mechanical oscillators as practical subjects for measurement-based quantum control.
• Piro, N., Schilling, R., Kippenberg, T. J., Wilson, D. J., & Ghadimi, A. H. (2013). Cavity Optomechanics: Controlling Mechanical Motion with Radiation Pressure. Frontiers in Optics. doi:10.1364/ls.2013.lw4g.5
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  Here we review recent progress on quantum coherent coupling, optomechanically induced transparency as well as switching, slowing and advancing of pulses via nano-optomechanical systems. Moreover the interaction of nanomechanics with two-level-defect states is discussed.
• Wilson, D. J., Painter, O., Norte, R. A., Ni, K. K., Kimble, H. J., Hood, J. D., & Chang, D. E. (2012). Enhancement of mechanical Q factors by optical trapping.. Physical review letters, 108(21), 214302. doi:10.1103/physrevlett.108.214302
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  The quality factor of a mechanical resonator is an important figure of merit for various sensing applications and for observing quantum behavior. Here, we demonstrate a technique to push the quality factor of a micromechanical resonator beyond conventional material and fabrication limits by using an optical field to stiffen or trap a particular motional mode. Optical forces increase the oscillation frequency by storing most of the mechanical energy in a nearly lossless optical potential, thereby strongly diluting the effect of material dissipation. By placing a 130 nm thick SiO2 pendulum in an optical standing wave, we achieve an increase in the pendulum center-of-mass frequency from 6.2 to 145 kHz. The corresponding quality factor increases 50-fold from its intrinsic value to a final value of Q=5.8(1.1)×10(5), representing more than an order of magnitude improvement over the conventional limits of SiO2 for this geometry. Our technique may enable new opportunities for mechanical sensing and facilitate observations of quantum behavior in this class of mechanical systems.
• Zhao, Y., Wilson, D. J., Ni, K. K., & Kimble, H. J. (2012). Suppression of extraneous thermal noise in cavity optomechanics.. Optics express, 20(4), 3586-612. doi:10.1364/oe.20.003586
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  Extraneous thermal motion can limit displacement sensitivity and radiation pressure effects, such as optical cooling, in a cavity-optomechanical system. Here we present an active noise suppression scheme and its experimental implementation. The main challenge is to selectively sense and suppress extraneous thermal noise without affecting motion of the oscillator. Our solution is to monitor two modes of the optical cavity, each with different sensitivity to the oscillator's motion but similar sensitivity to the extraneous thermal motion. This information is used to imprint "anti-noise" onto the frequency of the incident laser field. In our system, based on a nano-mechanical membrane coupled to a Fabry-Pérot cavity, simulation and experiment demonstrate that extraneous thermal noise can be selectively suppressed and that the associated limit on optical cooling can be reduced.
• Zhao, Y., Wilson, D. J., Ni, K., & Kimble, H. J. (2012). Suppression of extraneous thermal noise in cavity optomechanics. Bulletin of the American Physical Society.
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  Extraneous thermal motion can limit displacement sensitivity and radiation pressure effects, such as optical cooling, in a cavity-optomechanical system. Here we present an active noise suppression scheme and its experimental implementation. The main challenge is to selectively sense and suppress extraneous thermal noise without affecting motion of the oscillator. Our solution is to monitor two modes of the optical cavity, each with different sensitivity to the oscillator’s motion but similar sensitivity to the extraneous thermal motion. This information is used to imprint “anti-noise” onto the frequency of the incident laser field. In our system, based on a nano-mechanical membrane coupled to a Fabry-Perot cavity, simulation and experiment demonstrate that extraneous thermal noise can be selectively suppressed and that the associated limit on optical cooling can be reduced.
• Chang, D. E., Regal, C. A., Papp, S. B., Wilson, D. J., Ye, J., Painter, O., Kimble, H. J., & Zoller, P. (2010). Cavity opto-mechanics using an optically levitated nanosphere.. Proceedings of the National Academy of Sciences of the United States of America, 107(3), 1005-10. doi:10.1073/pnas.0912969107
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  Recently, remarkable advances have been made in coupling a number of high-Q modes of nano-mechanical systems to high-finesse optical cavities, with the goal of reaching regimes in which quantum behavior can be observed and leveraged toward new applications. To reach this regime, the coupling between these systems and their thermal environments must be minimized. Here we propose a novel approach to this problem, in which optically levitating a nano-mechanical system can greatly reduce its thermal contact, while simultaneously eliminating dissipation arising from clamping. Through the long coherence times allowed, this approach potentially opens the door to ground-state cooling and coherent manipulation of a single mesoscopic mechanical system or entanglement generation between spatially separate systems, even in room-temperature environments. As an example, we show that these goals should be achievable when the mechanical mode consists of the center-of-mass motion of a levitated nanosphere.
• Chang, D. E., Regal, C., Papp, S. B., Wilson, D. J., Ye, J., Zoller, P., Painter, O., & Kimble, J. (2009). Optical levitation of quantum nano-mechanical resonators. Bulletin of the American Physical Society, 40.
• Wilson, D. J., Regal, C. A., Papp, S. B., & Kimble, H. J. (2009). Cavity optomechanics with stoichiometric SiN films.. Physical review letters, 103(20), 207204. doi:10.1103/physrevlett.103.207204
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  We study high-stress SiN films for reaching the quantum regime with mesoscopic oscillators connected to a room-temperature thermal bath, for which there are stringent requirements on the oscillators' quality factors and frequencies. Our SiN films support mechanical modes with unprecedented products of mechanical quality factor Q(m) and frequency nu(m) reaching Q(m)nu(m) approximately or = 2 x 10(13) Hz. The SiN membranes exhibit a low optical absorption characterized by Im(n) < or approximately equal to 10(-5) at 935 nm, representing a 15 times reduction for SiN membranes. We have developed an apparatus to simultaneously cool the motion of multiple mechanical modes based on a short, high-finesse Fabry-Perot cavity and present initial cooling results along with future possibilities.
• Dai, X., Torres, E. A., Lerch, E. W., Wilson, D. J., & Leone, S. R. (2005). Preparation of a wave packet through a mixed level in Li2; predissociation of one member of the superposition. Chemical Physics Letters, 402(1), 126-132. doi:10.1016/j.cplett.2004.12.014
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  Abstract Through a mixed level, which has characters of both the A 1 Σ u + and b 3 Π u states of Li 2 , several singlet and triplet Rydberg states are accessed simultaneously using an ultrafast laser. The electronic, vibrational and rotational wave packets of these Rydberg states are detected. Since a single member of the excited superposition, 2 3 Σ g + ( v  = 12, N  = 16), is predissociative, the intensities of the quantum beats that have a component of this state decrease much faster with time (≈250 ps) than the other stable states. The polarization dependence of the quantum beats is utilized to assign the spectra.

Proceedings Publications

• Engelsen, N. J., Agrawal, A. R., & Wilson, D. J. (2021). Ultra-High-Q Nanomechanics Through Dissipation Dilution: Trends and Perspectives. In 2021 21st International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers).
• Wilson, D. J., Kippenberg, T. J., Sudhir, V., Ghadimi, A. H., Bereyhi, M. J., Federov, S., Engelsen, N. J., Schilling, R., & Shuetz, H. (2019). Playing quantum noise on a nanomechanical string (Conference Presentation). In Optical Trapping and Optical Micromanipulation XVI.
• Honl, S., Honl, S., Wilson, D. J., Wilson, D. J., Schneider, K., Schneider, K., Anderson, M., Anderson, M., Kippenberg, T. J., Kippenberg, T. J., Seidler, P., & Seidler, P. (2018). Gallium Phosphide Microresonator Frequency Combs. In Advanced Photonics 2018 (BGPP, IPR, NP, NOMA, Sensors, Networks, SPPCom, SOF).
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  We demonstrate the first microresonator frequency combs in GaP, a III-V semiconductor transparent above 549 nm. High Kerr nonlinearity (> 10−18 m2/W) yields a 10-mW parametric threshold and 100-nm-wide combs with THz spacing, centered at 1550 nm.
• Honl, S., Schneider, K., Anderson, M., Kippenberg, T. J., Seidler, P., & Wilson, D. J. (2018). Gallium phosphide microresonator frequency combs (Conference Presentation). In Laser Resonators, Microresonators, and Beam Control XX, 10518.
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  Gallium phosphide (GaP) is an attractive material for non-linear optics because of its broad transparency window (λ_vac > 548 nm) and large Kerr coefficient (n_2 ~ 6 × 10^-18 m^2/W). Though well-established in the semiconductor industry as a substrate for visible LEDs, its use in integrated photonics remains limited due to fabrication challenges. Recently we have developed a method to integrate high quality, epitaxially-grown GaP onto silica (SiO2) based on direct wafer bonding to an oxidized silicon carrier wafer. Here we exploit this platform to realize unprecedentedly low loss (Q > 3 × 10^5) GaP-on-SiO2 waveguide resonators which have been dispersion-engineered to support Kerr frequency comb generation in the C-band. Single-mode, grating-coupled ring resonators with radii from 10 – 100 μm are investigated. The threshold for parametric conversion is observed at input powers as little as 10 mW, followed by 0.1 – 1 THz frequency comb generation over a range exceeding 400 nm, in addition to strong second- and third-harmonic generation. Building on this advance, we discuss the prospects for low-noise, sub-mW-threshold soliton frequency combs with center frequencies tunable from the mid-IR to the near-IR. Applications of such devices range from precision molecular spectroscopy to ultrafast pulse generation to massively parallel coherent optical communication.
• Honl, S., Schneider, K., Welter, P., Baumgartner, Y., Hahn, H., Czornomaz, L., Wilson, D. J., & Seidler, P. (2018). GaP-On-Insulator as a Platform for Integrated Photonics. In Conference on Lasers and Electro-Optics.
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  We present a complete process flow for fabrication of integrated GaP-on-insulator photonic devices via direct wafer bonding of epitaxial films. High-fidelity patterning enables a range of applications, such as waveguide resonators and photonic crystal cavities.
• Wilson, D. J., Honl, S., Schneider, K., Anderson, M., Kippenberg, T. J., & Seidler, P. (2018). Gallium Phosphide Microresonator Frequency Combs. In Conference on Lasers and Electro-Optics.
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  We demonstrate the first microresonator frequency combs in GaP, a III-V semiconductor transparent above 549 nm. High Kerr nonlinearity (> 10−18 m2/W) yields a 10-mW parametric threshold and 100-nm-wide combs with THz spacing, centered at 1550 nm.
• Kippenberg, T. J., Sudhir, V., Schilling, R., Schuetz, H., Wilson, D. J., & Fedorov, S. A. (2017). Force metrology using quantum correlations of light due to a room-temperature mechanical oscillator. In Conference on Lasers and Electro-Optics.
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  We report on the observation of quantum correlations developed in a light beam that has interacted with a room-temperature nanomechanical oscillator. The vacuum fluctuations of the light drive the mechanical oscillator via the radiation pressure interaction, so that the phase of the transmitted light carries imprints of its own amplitude. We detect these subtle correlations, at the 5% level, using broadband measurements of the transmitted light in a homodyne detector tuned close to the amplitude quadrature. We also show how such correlations can be used for quantum-enhanced force metrology at room-temperature.
• Schutz, H., Sudhir, V., Schilling, R., Wilson, D. J., Kippenberg, T. J., & Fedorov, S. A. (2017). Quantum correlations of light due to a room temperature mechanical oscillator. In Conference on Lasers and Electro-Optics.
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  We observe quantum correlations imprinted on an optical beam interacting with a room temperature nanomechanical oscillator, and show how this leads to an enhancement in the relative signal-to-noise ratio for the estimation of an arbitrary force.
• Sudhir, V., Schilling, R., Schuetz, H., Wilson, D. J., Kippenberg, T. J., & Fedorov, S. A. (2017). Force metrology using quantum correlations of light due to a room-temperature mechanical oscillator. In 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 1-1.
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  The radiation pressure interaction of light with a mechanical oscillator leads to a fundamental disturbance on the oscillator. This disturbance — measurement backaction — is due to the quantum fluctuations in the amplitude of the light. When the phase of the light is detected to infer the mechanical position, quantum fluctuations in the phase — measurement imprecision — leads to a further uncertainty in the estimate of the position. In this conventional measurement strategy, these two noise sources impose a fundamental limit on the ability to estimate the position of the mechanical object — the so-called standard quantum limit [1]. However, the two noise contributions are in general correlated. The fluctuations in the amplitude quadrature drive the mechanical oscillator, and this backaction driven motion is transduced into the phase quadrature. Correlations thus established [2] form a valuable quantum mechanical resource that can be directly employed for back-action cancellation in the measurement record via “variational measurements” [3].
• Schilling, R., Schutz, H., Sudhir, V., Wilson, D. J., Kippenberg, T. J., & Ghadimi, A. H. (2016). Near-field integration of a Si 3 N 4 nanobeam and a SiO 2 microcavity for heisenberg-limited displacement sensing. In Conference on Lasers and Electro-Optics.
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  A single-chip radio-frequency optomechanical system, consisting of a Si 3 N 4 nanobeam in the evanescent near-field of a SiO 2 optical microdisk resonator realizes displacement imprecision >30dB below the standard quantum limit at room-temperature.
• Sudhir, V., Piro, N., Schilling, R., Wilson, D. J., Kippenberg, T. J., & Ghadimi, A. H. (2015). Feedback cooling of a nanomechanical oscillator to near its quantum ground state. In CLEO: 2015, 1-2.
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  Cavity-enhanced interferometry is used to resolve the displacement of a 4.3 MHz nanobeam oscillator with an imprecision 40 dB below that at the standard quantum limit. Employing this measurement as an error signal, radiation pressure is used to feedback cool the oscillator to 5.3 mechanical quanta.
• Chang, D. E., Wilson, D. J., Hood, J. D., Painter, O., Kimble, H. J., Norte, R. A., & Ni, K. K. (2012). Ultrahigh-Q Mechanical Oscillators Through Optical Trapping of Tethered Membranes. In Frontiers in Optics 2012/Laser Science XXVIII.
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  We demonstrate a technique to push the quality factor of a micromechanical resonator beyond conventional material and fabrication limits by using an optical field to stiffen and trap a particular motional mode.
• Zhao, Y., Wilson, D. J., Kimble, H. J., & Ni, K. K. (2012). Suppression of extraneous thermal noise in cavity optomechanics. In Conference on Lasers and Electro-Optics 2012, 1-2.
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  Extraneous thermal motion can limit displacement sensitivity and radiation pressure effects, such as optical cooling, in a cavity-optomechanical system. Here we present an active noise suppression scheme and its experimental implementation.

Presentations

• Wilson, D., & Pluchar, C. (2020, October). Towards observation of radiation pressure shot noise at acoustic frequencies. APS Four Corners.
• Wilson, D. (2019, August). Playing Quantum Noise on a Nanomechanical String. SPIE San Diego. San Diego: SPIE.
• Wilson, D. (2019, June). Strained Phononic Crystal Resonators for Quantum Optomechanics at Room Temperature. Phononics 2019. Tucson.
• Wilson, D. (2019, September). Quantum Optomechanics at University of Arizona. LVK (LIGO-VIRGO-KAGRA) Meeting. Warsaw: LIGO Scientific Collaboration.
• Wilson, D. (2018, Fall). Exploring Quantum Measurement with Nanomechanical Resonators. University of Arizona Physics Colloquium. Tucson, AZ: UA.