Showing 1–16 of 16 results for author: Cole, G

Moisture-driven CO2 direct air capture and delivery for cultivating cyanobacteria

Authors: Justin Flory, Shuqin Li, Samantha Taylor, Sunil Tiwari, Garrett Cole, Marlene Velazco Medel, Amory Lowe, Jordan Monroe, Sara Sarbaz, Nick Lowery, Joel Eliston, Heidi P. Feigenbaum, Heather Emady, Jason C. Quinn, Matthew Green, John McGowen, Klaus Lackner, Wim Vermaas

Abstract: A moisture-driven air capture system was developed and demonstrated for cultivating cyanobacteria and microalgae at the flask (50 mL), bench (12 L) and small pilot (840 L) scale. Purolite A501 anion exchange resin beads were found to be biocompatible and rapidly deliver air-captured CO2 when immersed directly in an alkaline cultivation medium containing cyanobacteria or microalgae. Flask-scale cul… ▽ More A moisture-driven air capture system was developed and demonstrated for cultivating cyanobacteria and microalgae at the flask (50 mL), bench (12 L) and small pilot (840 L) scale. Purolite A501 anion exchange resin beads were found to be biocompatible and rapidly deliver air-captured CO2 when immersed directly in an alkaline cultivation medium containing cyanobacteria or microalgae. Flask-scale cultivation trials showed A501 could sustain rapid growth (190 mg/L/d) of the cyanobacterium Synechocystis sp. PCC 6803 strain engineered to produce laurate. A bench-scale system installed in a laminar flow hood was able to deliver 2 g CO2/d into abiotic alkaline cultivation medium and 0.5 g/d in the presence of Synechocystis to support vigorous growth (39 mg/L/d) limited by the CO2 delivered by the sorbent. A small pilot-scale system installed in a 4.2 m2 outdoor raceway pond in Mesa, Arizona was able to deliver 100 g CO2/d into abiotic alkaline cultivation medium. Exopolysaccharides and other products excreted by Synechocystis 6803 covered the sorbent beads, reducing their capacity to 25%, which could be partially restored to 70% capacity using a wash protocol, but the CO2 delivery kinetics remained 3-4 fold slower. Analysis of the sorbent beads used as part of four separate outdoor cultivation trials with over 300 days of outdoor wet and dry cycling over four seasons showed significant mechanical fracturing. Infrared spectroscopy and thermogravimetric analysis showed a significant loss of NR4+ functional groups necessary for CO2 capture correlated with extended use. Under the assumption that abiotic performance eventually can be retained by delivering CO2 into the media recycle stream in a way that avoids biofouling, technoeconomic and life cycle analyses show the viability of a small first-of-a-kind biorefinery producing 500 barrels per day of biofuel. △ Less

Submitted 6 August, 2025; originally announced August 2025.

Comments: 18 pages, 13 main figures

Design and demonstration of a direct air capture system with moisture-driven CO2 delivery into aqueous medium

Authors: Justin Flory, Samantha Taylor, Shuqin Li, Sunil Tiwari, Garrett Cole, Amory Lowe, Lindsey Hamblin, Samuel Piorkowski, Matthew Ryan, Thiago Stangherlin Barbosa, Jason Kmon, Nick Lowery, Joel Eliston, Jason C. Quinn, John McGowen, Matthew D. Green, Klaus Lackner, Wim Vermaas

Abstract: A moisture-driven air capture (DAC) system was designed and demonstrated. A laboratory-scale system delivering ~1 g CO2 per day was demonstrated in a laminar flow hood and a small pilot-scale system that could deliver ~100 g CO2 daily was operated outdoors in a 4.2 m2 (areal surface area) raceway pond. Elongated mesh tube packets were designed to contain AER beads with high surface area for contac… ▽ More A moisture-driven air capture (DAC) system was designed and demonstrated. A laboratory-scale system delivering ~1 g CO2 per day was demonstrated in a laminar flow hood and a small pilot-scale system that could deliver ~100 g CO2 daily was operated outdoors in a 4.2 m2 (areal surface area) raceway pond. Elongated mesh tube packets were designed to contain AER beads with high surface area for contacting the air and were found to reduce drying and CO2 loading time ~4-fold over larger mesh bags. Whereas this system was designed for CO2 delivery for cultivating photosynthetic microbes, its potential uses are much broader and include CO2 use in the food and beverage industry, conversion to fuels and chemicals, and sequestration. Techno-economic assessments for a practical scenario based on current results are \$670/tonne to capture CO2 into an alkaline solution and an additional \$280/tonne to extract CO2 from solution, purify and compress to 15 MPa for sequestration. An aspirational scenario modelling reasonable improvements to develop AER sorbents with a capacity of 4 mmol CO2 per gram of sorbent and water uptake of 50 wt.%, which leads to sorbent drying and loading within 1 h, shows a potential to reach \$51/tonne to capture CO2 into an alkaline solution and an additional \$109/tonne to get to 15 MPa for sequestration. Life cycle analysis shows the aspirational moisture-driven process uses up to 87% less energy than thermal and/or vacuum swing DAC by using energy from water evaporation; however, ~330 wt.% water uptake by the sorbent contained in a hydrophilic mesh packets leads to ~33-fold higher water use than the thermodynamic limits, which emphasizes future research is needed to increase sorbent hydrophobicity while maintaining and further increasing ion exchange capacity needed to bind CO2. △ Less

Submitted 4 August, 2025; originally announced August 2025.

Comments: 14 pages, 11 figures. To be submitted to Energy & Environmental Science

Simultaneous Measurement of Mid-Infrared Refractive Indices in Thin-Film Heterostructures: Methodology and Results for GaAs/AlGaAs

Authors: Lukas W. Perner, Gar-Wing Truong, David Follman, Maximilian Prinz, Georg Winkler, Stephan Puchegger, Garrett D. Cole, Oliver H. Heckl

Abstract: We present our results for simultaneous measurement of the refractive indices of gallium arsenide (GaAs) and aluminum gallium arsenide (Al$_\mathrm{x}$Ga$_\mathrm{1-x}$As) from $2.0$ to $7.1\,\mathrm{μm}$ ($5000$ to $1400\,\mathrm{cm^{-1}}$). We obtain these values from a monocrystalline superlattice Bragg mirror of excellent purity (background doping $\leq 1 \times 10^{-14}\,\mathrm{cm^{-3}}$), g… ▽ More We present our results for simultaneous measurement of the refractive indices of gallium arsenide (GaAs) and aluminum gallium arsenide (Al$_\mathrm{x}$Ga$_\mathrm{1-x}$As) from $2.0$ to $7.1\,\mathrm{μm}$ ($5000$ to $1400\,\mathrm{cm^{-1}}$). We obtain these values from a monocrystalline superlattice Bragg mirror of excellent purity (background doping $\leq 1 \times 10^{-14}\,\mathrm{cm^{-3}}$), grown via molecular beam epitaxy. To recover the refractive indices over such a broad wavelength range, we fit a dispersion model for each material. In a novel combination of well-established methods, we measure both a photometrically accurate transmittance spectrum of the Bragg mirror via Fourier-transform infrared spectrometry and the individual physical layer thicknesses of the structure via scanning electron microscopy. To infer the uncertainty of the refractive index values, we estimate relevant measurement uncertainties and propagate them via a Monte-Carlo method. This highly-adaptable approach conclusively yields propagated relative uncertainties on the order of $10^{-4}$ over the measured spectral range for both GaAs and Al$_{0.929}$Ga$_{0.071}$As. The fitted model can also approximate the refractive index for MBE-grown Al$_\mathrm{x}$Ga$_\mathrm{1-x}$As for $0\leq x \leq 1$. Both these updated values and the measurement approach will be essential in the design, fabrication, and characterization of next-generation active and passive optical devices in a spectral region that is of high interest in many fields, e.g., laser design and cavity-enhanced spectroscopy in the mid-infrared spectral region. △ Less

Submitted 16 May, 2023; v1 submitted 18 January, 2023; originally announced January 2023.

Comments: 21 pages, 6 figures, transferred to PRResearch

Journal ref: Phys. Rev. Research 5 (2023) 033048

Precise Measurement of Refractive Indices in Thin Film Heterostructures

Authors: Lukas W. Perner, Gar-Wing Truong, David Follman, Maximilian Prinz, Georg Winkler, Stephan Puchegger, Garrett D. Cole, Oliver H. Heckl

Abstract: We present a robust, precise, and accurate method to simultaneously measure the refractive indices of two transparent materials within an interference coating. This is achieved by measuring both a photometrically accurate transmittance spectrum and the as-grown individual layer thicknesses of a thin-film multilayer structure. These measurements are used for a TMM-based curve-fitting routine which… ▽ More We present a robust, precise, and accurate method to simultaneously measure the refractive indices of two transparent materials within an interference coating. This is achieved by measuring both a photometrically accurate transmittance spectrum and the as-grown individual layer thicknesses of a thin-film multilayer structure. These measurements are used for a TMM-based curve-fitting routine which extracts the refractive indices and their measurement uncertainties via a Monte-Carlo-type error propagation. We demonstrate the performance of this approach by experimentally measuring the refractive indices of both, GaAs and Al$_{0.929}$Ga$_{0.071}$As, as present in an epitaxial distributed Bragg reflector. A variety of devices can be used to obtain the transmittance spectrum (e.g., FTIR, grating-based spectrophotometer) and layer thicknesses (e.g., SEM, TEM, AFM), the discussed approach is readily adaptable to virtually any wavelength region and many transparent material combinations of interest. The subsequent model-fitting approach yields refractive index values with $10^{-4}$-level uncertainty for both materials. △ Less

Submitted 18 January, 2023; originally announced January 2023.

Comments: 13 pages, 3 figures, submitted to PRL

Mid-infrared monocrystalline interference coatings with excess optical loss below 10 ppm

Authors: G. Winkler, L. W. Perner, G. -W. Truong, G. Zhao, D. Bachmann, A. S. Mayer, J. Fellinger, D. Follman, P. Heu, C. Deutsch, D. M. Bailey, H. Peelaers, S. Puchegger, A. J. Fleisher, G. D. Cole, O. H. Heckl

Abstract: We present high-reflectivity substrate-transferred single-crystal GaAs/AlGaAs interference coatings at a center wavelength of 4.54 um with record-low excess optical loss below 10 parts per million. These high-performance mirrors are realized via a novel microfabrication process that differs significantly from the production of amorphous multilayers generated via physical vapor deposition processes… ▽ More We present high-reflectivity substrate-transferred single-crystal GaAs/AlGaAs interference coatings at a center wavelength of 4.54 um with record-low excess optical loss below 10 parts per million. These high-performance mirrors are realized via a novel microfabrication process that differs significantly from the production of amorphous multilayers generated via physical vapor deposition processes. This new process enables reduced scatter loss due to the low surface and interfacial roughness, while low background doping in epitaxial growth ensures strongly reduced absorption. We report on a suite of optical measurements, including cavity ring-down, transmittance spectroscopy, and direct absorption tests to reveal the optical losses for a set of prototype mirrors. In the course of these measurements, we observe a unique polarization-orientation-dependent loss mechanism which we attribute to elastic anisotropy of these strained epitaxial multilayers. A future increase in layer count and a corresponding reduction of transmittance will enable optical resonators with a finesse in excess of 100 000 in the mid-infrared spectral region, allowing for advances in high resolution spectroscopy, narrow-linewidth laser stabilization, and ultrasensitive measurements of various light-matter interactions. △ Less

Submitted 10 September, 2020; originally announced September 2020.

Mechanical Ringdown Studies of Large-Area Substrate-Transferred GaAs/AlGaAs Crystalline Coatings

Authors: Steven D. Penn, Maya M. Kinley-Hanlon, Ian A. O. MacMillan, Paula Heu, David Follman, Christoph Deutsch, Garrett D. Cole, Gregory M. Harry

Abstract: We investigated elastic loss in GaAs/AlGaAs multilayers to help determine the suitability of these coatings for future gravitational wave detectors. We measured large ($\approx 70$-mm diameter) substrate-transferred crystalline coating samples with an improved substrate polish and bonding method. The elastic loss, when decomposed into bulk and shear contributions, was shown to arise entirely from… ▽ More We investigated elastic loss in GaAs/AlGaAs multilayers to help determine the suitability of these coatings for future gravitational wave detectors. We measured large ($\approx 70$-mm diameter) substrate-transferred crystalline coating samples with an improved substrate polish and bonding method. The elastic loss, when decomposed into bulk and shear contributions, was shown to arise entirely from the bulk loss, $φ_{\mathrm{Bulk}} = (5.33 \pm 0.03)\times 10^{-4}$, with $φ_{\mathrm{Shear}} = (0.0 \pm 5.2) \times 10^{-7}$. These results predict the coating loss of an 8-mm diameter coating in a 35-mm long cavity with a 250-$μ$m spot size (radius) to be $φ_{\mathrm{coating}} = (4.78 \pm 0.05) \times 10^{-5}$, in agreement with the published result from direct thermal noise measurement of $φ_{\mathrm{coating}} = (4 \pm 4) \times 10^{-5}$. Bonding defects were shown to have little impact on the overall elastic loss. △ Less

Submitted 14 November, 2018; originally announced November 2018.

Comments: Submitted to Journal of the Optical Society of America B, Feature: Fluctuation-Induced Phenomena in Photonic Systems

Stress control of tensile-strained In$_{1-x}$Ga$_{x}$P nanomechanical string resonators

Authors: Maximilian Bückle, Valentin C. Hauber, Garrett D. Cole, Claus Gärtner, Ute Zeimer, Jörg Grenzer, Eva M. Weig

Abstract: We investigate the mechanical properties of freely suspended nanostrings fabricated from tensile-stressed, crystalline In$_{1-x}$Ga$_{x}$P. The intrinsic strain is a consequence of the epitaxial growth given by the lattice mismatch between the thin film and the substrate which is confirmed by x-ray diffraction measurements. The flexural eigenfrequencies of the nanomechanical string resonators reve… ▽ More We investigate the mechanical properties of freely suspended nanostrings fabricated from tensile-stressed, crystalline In$_{1-x}$Ga$_{x}$P. The intrinsic strain is a consequence of the epitaxial growth given by the lattice mismatch between the thin film and the substrate which is confirmed by x-ray diffraction measurements. The flexural eigenfrequencies of the nanomechanical string resonators reveal an orientation dependent stress with a maximum value of 650 MPa. The angular dependence is explained by a combination of anisotropic Young's modulus and a change of elastic properties caused by defects. As a function of the crystal orientation a stress variation of up to 50 % is observed. This enables fine tuning of the tensile stress for any given Ga content $x$, which implies interesting prospects for the study of high Q nanomechanical systems. △ Less

Submitted 15 November, 2018; v1 submitted 29 August, 2018; originally announced August 2018.

Journal ref: Appl. Phys. Lett. 113, 201903 (2018)

High-performance near- and mid-infrared crystalline coatings

Authors: Garrett D. Cole, Wei Zhang, Bryce J. Bjork, David Follman, Paula Heu, Christoph Deutsch, Lindsay Sonderhouse, John Robinson, Chris Franz, Alexei Alexandrovski, Mark Notcutt, Oliver H. Heckl, Jun Ye, Markus Aspelmeyer

Abstract: Substrate-transferred crystalline coatings have recently emerged as a groundbreaking new concept in optical interference coatings. Building upon our initial demonstration of this technology, we have now realized significant improvements in the limiting optical performance of these novel single-crystal $GaAs/Al_{x}Ga_{1-x}As$ multilayers. In the near-infrared (NIR), for coating center wavelengths s… ▽ More Substrate-transferred crystalline coatings have recently emerged as a groundbreaking new concept in optical interference coatings. Building upon our initial demonstration of this technology, we have now realized significant improvements in the limiting optical performance of these novel single-crystal $GaAs/Al_{x}Ga_{1-x}As$ multilayers. In the near-infrared (NIR), for coating center wavelengths spanning 1064 to 1560 nm, we have reduced the excess optical losses (scatter + absorption) to levels as low as 3 parts per million, enabling the realization of a cavity finesse exceeding $3\times 10^{5}$ at the telecom-relevant wavelength range near 1550 nm. Moreover, we demonstrate the direct measurement of sub-ppm optical absorption at 1064 nm. Concurrently, we investigate the mid-IR (MIR) properties of these coatings and observe exceptional performance for first attempts in this important wavelength region. Specifically, we verify excess losses at the hundred ppm level for wavelengths of 3300 and 3700 nm. Taken together, our NIR optical losses are now fully competitive with ion beam sputtered multilayer coatings, while our first prototype MIR optics have already reached state-of-the-art performance levels for reflectors covering this portion of the fingerprint region for optical gas sensing. Mirrors fabricated with our crystalline coating technique exhibit the lowest mechanical loss, and thus the lowest Brownian noise, the highest thermal conductivity, and, potentially, the widest spectral coverage of any "supermirror" technology in a single material platform. Looking ahead, we see a bright future for crystalline coatings in applications requiring the ultimate levels of optical, thermal, and optomechanical performance △ Less

Submitted 22 March, 2016; originally announced April 2016.

Comments: 8 pages and 7 figures

Tensile strained $In_{x}Ga_{1-x}P$ membranes for cavity optomechanics

Authors: G. D. Cole, P. -L. Yu, C. Gärtner, K. Siquans, R. Moghadas Nia, J. Schmöle, J. Hoelscher-Obermaier, T. P. Purdy, W. Wieczorek, C. A. Regal, M. Aspelmeyer

Abstract: We investigate the optomechanical properties of tensile-strained ternary InGaP nanomembranes grown on GaAs. This material system combines the benefits of highly strained membranes based on stoichiometric silicon nitride, with the unique properties of thin-film semiconductor single crystals, as previously demonstrated with suspended GaAs. Here we employ lattice mismatch in epitaxial growth to impar… ▽ More We investigate the optomechanical properties of tensile-strained ternary InGaP nanomembranes grown on GaAs. This material system combines the benefits of highly strained membranes based on stoichiometric silicon nitride, with the unique properties of thin-film semiconductor single crystals, as previously demonstrated with suspended GaAs. Here we employ lattice mismatch in epitaxial growth to impart an intrinsic tensile strain to a monocrystalline thin film (approximately 30 nm thick). These structures exhibit mechanical quality factors of 2*10^6 or beyond at room temperature and 17 K for eigenfrequencies up to 1 MHz, yielding Q*f products of 2*10^12 Hz for a tensile stress of ~170 MPa. Incorporating such membranes in a high finesse Fabry-Perot cavity, we extract an upper limit to the total optical loss (including both absorption and scatter) of 40 ppm at 1064 nm and room temperature. Further reductions of the In content of this alloy will enable tensile stress levels of 1 GPa, with the potential for a significant increase in the Q*f product, assuming no deterioration in the mechanical loss at this composition and strain level. This materials system is a promising candidate for the integration of strained semiconductor membrane structures with low-loss semiconductor mirrors and for realizing stacks of membranes for enhanced optomechanical coupling. △ Less

Submitted 31 March, 2014; originally announced April 2014.

Comments: 10 pages, 3 figures

Observation of non-Markovian micro-mechanical Brownian motion

Authors: S. Groeblacher, A. Trubarov, N. Prigge, G. D. Cole, M. Aspelmeyer, J. Eisert

Abstract: All physical systems are to some extent open and interacting with their environment. This insight, basic as it may seem, gives rise to the necessity of protecting quantum systems from decoherence in quantum technologies and is at the heart of the emergence of classical properties in quantum physics. The precise decoherence mechanisms, however, are often unknown for a given system. In this work, we… ▽ More All physical systems are to some extent open and interacting with their environment. This insight, basic as it may seem, gives rise to the necessity of protecting quantum systems from decoherence in quantum technologies and is at the heart of the emergence of classical properties in quantum physics. The precise decoherence mechanisms, however, are often unknown for a given system. In this work, we make use of an opto-mechanical resonator to obtain key information about spectral densities of its condensed-matter heat bath. In sharp contrast to what is commonly assumed in high-temperature quantum Brownian motion describing the dynamics of the mechanical degree of freedom, based on a statistical analysis of the emitted light, it is shown that this spectral density is highly non-Ohmic, reflected by non-Markovian dynamics, which we quantify. We conclude by elaborating on further applications of opto-mechanical systems in open system identification. △ Less

Submitted 28 July, 2015; v1 submitted 29 May, 2013; originally announced May 2013.

Comments: 5+6 pages, 3 figures. Replaced by final version

Journal ref: Nature Comm. 6, 7606 (2015)

Tenfold reduction of Brownian noise in optical interferometry

Authors: Garrett D. Cole, Wei Zhang, Michael J. Martin, Jun Ye, Markus Aspelmeyer

Abstract: Thermally induced fluctuations impose a fundamental limit on precision measurement. In optical interferometry, the current bounds of stability and sensitivity are dictated by the excess mechanical damping of the high-reflectivity coatings that comprise the cavity end mirrors. Over the preceding decade, the mechanical loss of these amorphous multilayer reflectors has at best been reduced by a facto… ▽ More Thermally induced fluctuations impose a fundamental limit on precision measurement. In optical interferometry, the current bounds of stability and sensitivity are dictated by the excess mechanical damping of the high-reflectivity coatings that comprise the cavity end mirrors. Over the preceding decade, the mechanical loss of these amorphous multilayer reflectors has at best been reduced by a factor of two. Here we demonstrate a new paradigm in optical coating technology based on direct-bonded monocrystalline multilayers, which exhibit both intrinsically low mechanical loss and high optical quality. Employing these "crystalline coatings" as end mirrors in a Fabry-Pérot cavity, we obtain a finesse of 150,000. More importantly, at room temperature, we observe a thermally-limited noise floor consistent with a tenfold reduction in mechanical damping when compared with the best dielectric multilayers. These results pave the way for the next generation of ultra-sensitive interferometers, as well as for new levels of laser stability. △ Less

Submitted 26 February, 2013; originally announced February 2013.

Journal ref: Nature Photonics 7, 644 - 650 (2013)

Cooling-by-measurement and mechanical state tomography via pulsed optomechanics

Authors: M. R. Vanner, J. Hofer, G. D. Cole, M. Aspelmeyer

Abstract: Observing a physical quantity without disturbing it is a key capability for the control of individual quantum systems. Such back-action-evading or quantum-non-demolition measurements were first introduced in the 1970s in the context of gravitational wave detection to measure weak forces on test masses by high precision monitoring of their motion. Now, such techniques have become an indispensable t… ▽ More Observing a physical quantity without disturbing it is a key capability for the control of individual quantum systems. Such back-action-evading or quantum-non-demolition measurements were first introduced in the 1970s in the context of gravitational wave detection to measure weak forces on test masses by high precision monitoring of their motion. Now, such techniques have become an indispensable tool in quantum science for preparing, manipulating, and detecting quantum states of light, atoms, and other quantum systems. Here we experimentally perform rapid optical quantum-noise-limited measurements of the position of a mechanical oscillator by using pulses of light with a duration much shorter than a period of mechanical motion. Using this back-action evading interaction we performed both state preparation and full state tomography of the mechanical motional state. We have reconstructed mechanical states with a position uncertainty reduced to 19 pm, limited by the quantum fluctuations of the optical pulse, and we have performed `cooling-by-measurement' to reduce the mechanical mode temperature from an initial 1100 K to 16 K. Future improvements to this technique may allow for quantum squeezing of mechanical motion, even from room temperature, and reconstruction of non-classical states exhibiting negative regions in their phase-space quasi-probability distribution. △ Less

Submitted 15 May, 2013; v1 submitted 29 November, 2012; originally announced November 2012.

Comments: Note title change, 10 pages, 5 figures, includes supplementary information

Journal ref: Nature Communications 4, 2295 (2013)

Pulsed quantum optomechanics

Authors: M. R. Vanner, I. Pikovski, G. D. Cole, M. S. Kim, C. Brukner, K. Hammerer, G. J. Milburn, M. Aspelmeyer

Abstract: Studying mechanical resonators via radiation pressure offers a rich avenue for the exploration of quantum mechanical behavior in a macroscopic regime. However, quantum state preparation and especially quantum state reconstruction of mechanical oscillators remains a significant challenge. Here we propose a scheme to realize quantum state tomography, squeezing and state purification of a mechanical… ▽ More Studying mechanical resonators via radiation pressure offers a rich avenue for the exploration of quantum mechanical behavior in a macroscopic regime. However, quantum state preparation and especially quantum state reconstruction of mechanical oscillators remains a significant challenge. Here we propose a scheme to realize quantum state tomography, squeezing and state purification of a mechanical resonator using short optical pulses. The scheme presented allows observation of mechanical quantum features despite preparation from a thermal state and is shown to be experimentally feasible using optical microcavities. Our framework thus provides a promising means to explore the quantum nature of massive mechanical oscillators and can be applied to other systems such as trapped ions. △ Less

Submitted 11 October, 2011; v1 submitted 3 November, 2010; originally announced November 2010.

Comments: 9 pages, 4 figures

Journal ref: Proc Natl Acad Sci USA 108, 16182 (2011)

Minimization of phonon-tunneling dissipation in mechanical resonators

Authors: Garrett D. Cole, Ignacio Wilson-Rae, Katharina Werbach, Michael R. Vanner, Markus Aspelmeyer

Abstract: Micro- and nanoscale mechanical resonators have recently emerged as ubiquitous devices for use in advanced technological applications, for example in mobile communications and inertial sensors, and as novel tools for fundamental scientific endeavors. Their performance is in many cases limited by the deleterious effects of mechanical damping. Here, we report a significant advancement towards unders… ▽ More Micro- and nanoscale mechanical resonators have recently emerged as ubiquitous devices for use in advanced technological applications, for example in mobile communications and inertial sensors, and as novel tools for fundamental scientific endeavors. Their performance is in many cases limited by the deleterious effects of mechanical damping. Here, we report a significant advancement towards understanding and controlling support-induced losses in generic mechanical resonators. We begin by introducing an efficient numerical solver, based on the "phonon-tunneling" approach, capable of predicting the design-limited damping of high-quality mechanical resonators. Further, through careful device engineering, we isolate support-induced losses and perform the first rigorous experimental test of the strong geometric dependence of this loss mechanism. Our results are in excellent agreement with theory, demonstrating the predictive power of our approach. In combination with recent progress on complementary dissipation mechanisms, our phonon-tunneling solver represents a major step towards accurate prediction of the mechanical quality factor. △ Less

Submitted 28 July, 2010; originally announced July 2010.

Comments: 12 pages, 4 figures

Journal ref: Nat. Comm. 2:231 (2011)

Demonstration of an ultracold micro-optomechanical oscillator in a cryogenic cavity

Authors: Simon Groeblacher, Jared B. Hertzberg, Michael R. Vanner, Garrett D. Cole, Sylvain Gigan, K. C. Schwab, Markus Aspelmeyer

Abstract: Preparing and manipulating quantum states of mechanical resonators is a highly interdisciplinary undertaking that now receives enormous interest for its far-reaching potential in fundamental and applied science. Up to now, only nanoscale mechanical devices achieved operation close to the quantum regime. We report a new micro-optomechanical resonator that is laser cooled to a level of 30 thermal qu… ▽ More Preparing and manipulating quantum states of mechanical resonators is a highly interdisciplinary undertaking that now receives enormous interest for its far-reaching potential in fundamental and applied science. Up to now, only nanoscale mechanical devices achieved operation close to the quantum regime. We report a new micro-optomechanical resonator that is laser cooled to a level of 30 thermal quanta. This is equivalent to the best nanomechanical devices, however, with a mass more than four orders of magnitude larger (43 ng versus 1 pg) and at more than two orders of magnitude higher environment temperature (5 K versus 30 mK). Despite the large laser-added cooling factor of 4,000 and the cryogenic environment, our cooling performance is not limited by residual absorption effects. These results pave the way for the preparation of 100-um scale objects in the quantum regime. Possible applications range from quantum-limited optomechanical sensing devices to macroscopic tests of quantum physics. △ Less

Submitted 21 October, 2013; v1 submitted 13 January, 2009; originally announced January 2009.

Comments: Published version

Journal ref: Nature Phys. 5, 485-488 (2009)

Monocrystalline AlGaAs heterostructures for high-reflectivity high-Q micromechanical resonators in the MHz regime

Authors: Garrett D. Cole, Simon Groeblacher, Katharina Gugler, Sylvain Gigan, Markus Aspelmeyer

Abstract: We present high-performance megahertz micromechanical oscillators based on freestanding epitaxial AlGaAs distributed Bragg reflectors. Compared with dielectric reflectors, the low mechanical loss of the monocrystalline heterostructure gives rise to significant improvements in the achievable mechanical quality factor Q while simultaneously exhibiting near unity reflectivity. Experimental characte… ▽ More We present high-performance megahertz micromechanical oscillators based on freestanding epitaxial AlGaAs distributed Bragg reflectors. Compared with dielectric reflectors, the low mechanical loss of the monocrystalline heterostructure gives rise to significant improvements in the achievable mechanical quality factor Q while simultaneously exhibiting near unity reflectivity. Experimental characterization yields an optical reflectivity exceeding 99.98% and mechanical quality factors up to 20 000 at 4 K. This materials system is not only an interesting candidate for optical coatings with ultralow thermal noise, but also provides a promising path toward quantum optical control of massive micromechanical mirrors. △ Less

Submitted 18 September, 2008; v1 submitted 4 February, 2008; originally announced February 2008.

Comments: 5 pages, 2 figures

Journal ref: Appl. Phys. Lett. 92, 261108 (2008)