Search

Gravimetry typically lacks the resolution to measure single microdroplets, whereas microscopy is often inaccurate beyond the resolution limit. To address these issues, we advance and integrate these complementary methods, introducing simultaneous measurements of the same microdroplets, comprehensive calibrations that are independently traceable to the International System of Units (SI), and Monte-Carlo evaluations of volumetric uncertainty. We achieve sub-picoliter agreement of measurements of microdroplets in flight with volumes of approximately 70 pL, with ensemble gravimetry and optical microscopy both yielding 95% coverage intervals of +/- 0.6 pL, or relative uncertainties of +/- 0.9%, and root-mean-square deviations of mean values between the two methods of 0.2 pL or 0.3%. These uncertainties match previous gravimetry results and improve upon previous microscopy results by an order of magnitude. Gravimetry precision depends on the continuity of droplet formation, whereas microscopy accuracy requires that optical diffraction from an edge reference matches that from a microdroplet. Applying our microscopy method, we jet and image water microdroplets suspending fluorescent nanoplastics, count nanoplastic particles after deposition and evaporation, and transfer volumetric traceability to number concentration. We expect that our methods will impact diverse fields involving dimensional metrology and volumetric analysis of microdroplets, including inkjet microfabrication, disease transmission, and industrial sprays.

Traceability to the International System of Units (SI) is fundamental to measurement accuracy and reliability. In this study, we demonstrate subnanometer traceability of localization microscopy, establishing a metrological foundation for the maturation and application of super-resolution methods. To do so, we create a master standard by measuring the positions of submicrometer apertures in an array by traceable atomic-force microscopy. We perform correlative measurements of this master standard by optical microscopy, calibrating scale factor and correcting aberration effects. We introduce the concept of a localization uncertainty field due to optical localization errors and scale factor uncertainty, with regions of position traceability to within a 68 % coverage interval of +/- 1 nm. These results enable localization metrology with high throughput, which we apply to measure working standards that we fabricate by electron-beam lithography, validating the accuracy of mean pitch and closing the loop for disseminating and integrating reference arrays. We then apply our novel methods to calibrate an optical microscope with a sample cryostat, accounting for thermal contraction by use of a submicrometer pillar array in silicon as a reference material and elucidating complex distortion. This new calibration enables the accurate integration of quantum emitters and photonic structures with high yield, as we demonstrate theoretically through simulations of the dependence of the Purcell factor of radiative enhancement on registration errors across a wide field. Our study illuminates the challenges and opportunities of achieving traceable localization for comparison of position data across lithography and microscopy systems, from ambient to cryogenic temperatures.

Plastic nanoparticles present technological opportunities and environmental concerns, but measurement challenges impede product development and hazard assessment. To meet these challenges, we advance a lateral nanoflow assay that integrates complex nanofluidic replicas, optical localization microscopy, and novel statistical analyses. We apply our sample-in-answer-out system to measure polystyrene nanoparticles that sorb and carry hydrophobic fluorophores. An elegant scaling of surface forces automates advection and dominates diffusion to drive the analytical separation of colloidal nanoparticles by their steric diameters. Reference nanoparticles, with a mean of 99 nm and a standard deviation of 8.4 nm, test the unknown limits of silicone replicas to function as separation matrices. New calibrations correct aberrations from microscope and device, improving the accuracy of reducing single micrographs to joint histograms of steric diameter and fluorescence intensity. A dimensional model approaches the information limit of the system to discriminate size exclusion from surface adsorption, yielding errors of the mean ranging from 0.2 nm to 2.3 nm and errors of the standard deviation ranging from 2.2 nm to 4.2 nm. A hierarchical model accounts for metrological, optical, and dimensional variability to reveal a fundamental structure-property relationship. Intensity scales with diameter to the power of 3.6 +/- 0.5 at 95 % coverage, confounding basic concepts of surface adsorption or volume absorption. Distributions of fluorescivity - the product of the number density, absorption cross section, and quantum yield of an ensemble of fluorophores - are ultrabroad and asymmetric, limiting any inference from fluorescence intensity. This surprising characterization of common nanoplastics resets expectations for optimizing products, applying standards, and understanding byproducts.

Focused-ion-beam machining is a powerful process to fabricate complex nanostructures, often through a sacrificial mask that enables milling beyond the resolution limit of the ion beam. However, current understanding of this super-resolution effect is empirical in the spatial domain and nonexistent in the temporal domain. This article reports the primary study of this fundamental tradespace of resolution and throughput. Chromia functions well as a masking material due to its smooth, uniform, and amorphous structure. An efficient method of in-line metrology enables characterization of ion-beam focus by scanning electron microscopy. Fabrication and characterization of complex test-structures through chromia and into silica probe the response of the bilayer to a focused beam of gallium cations, demonstrating super-resolution factors of up to 6 $\pm$ 2 and improvements to volume throughput of at least factors of 42 $\pm$ 2, with uncertainties denoting 95 % coverage intervals. Tractable theory models the essential aspects of the super-resolution effect for various nanostructures. Application of the new tradespace increases the volume throughput of machining Fresnel lenses by a factor of 75, which we introduce as projection standards for optical microscopy. These results enable paradigm shifts of sacrificial masking from empirical to engineering design, and from prototyping to manufacturing.

A standard paradigm of localization microscopy involves extension from two to three dimensions by engineering information into emitter images, and approximation of errors resulting from the field dependence of optical aberrations. We invert this standard paradigm, introducing the concept of fully exploiting the latent information of intrinsic aberrations by comprehensive calibration of an ordinary microscope, enabling accurate localization of single emitters in three dimensions throughout an ultrawide and deep field. To complete the extraction of spatial information from microscale bodies ranging from imaging substrates to microsystem technologies, we introduce a synergistic concept of the rigid transformation of the positions of multiple emitters in three dimensions, improving precision, testing accuracy, and yielding measurements in six degrees of freedom. Our study illuminates the challenge of aberration effects in localization microscopy, redefines the challenge as an opportunity for accurate, precise, and complete localization, and elucidates the performance and reliability of a complex microelectromechanical system.

Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities to explore fundamental physics and enable new measurements. However, their size and use of bulk components prevent them from being more widely adopted in applications that require precision timing. By leveraging silicon-chip photonics for integration and to reduce component size and complexity, we demonstrate a compact optical-clock architecture. Here a semiconductor laser is stabilized to an optical transition in a microfabricated rubidium vapor cell, and a pair of interlocked Kerr-microresonator frequency combs provide fully coherent optical division of the clock laser to generate an electronic 22 GHz clock signal with a fractional frequency instability of one part in 10^13. These results demonstrate key concepts of how to use silicon-chip devices in future portable and ultraprecise optical clocks., Comment: 11 pages, 4 figures

We demonstrate the fabrication of $\sim$1.08 $\mu$m deep microfluidic cavities with characteristic size as large as 7 mm $\times$ 11 mm or 11 mm diameter, using a silicon$-$glass anodic bonding technique that does not require posts to act as separators to define cavity height. Since the phase diagram of $^3$He is significantly altered under confinement, posts might act as pinning centers for phase boundaries. The previous generation of cavities relied on full wafer-bonding which is more prone to failure and requires dicing post-bonding, whereas the these cavities are made by bonding a pre-cut piece of Hoya SD-2 glass to a patterned piece of silicon in which the cavity is defined by etching. Anodic bonding was carried out at 425 $^{\circ}$C with 200 V, and we observe that pressurizing the cavity to failure ($>$ 30 bar pressure) results in glass breaking, rather than the glass-silicon bond separation. In this article, we discuss the detailed fabrication of the cavity, its edges, and details of the junction between the coin silver fill line and the silicon base of the cavity that enables a low internal-friction joint. This feature is important for mass coupling torsional oscillator experimental assays of the superfluid inertial contribution where a high quality factor ($Q$) improves frequency resolution. The surface preparation that yields well-characterized smooth surfaces to eliminate pinning sites, the use of transparent glass as a cover permitting optical access, low temperature capability and attachment of pressure-capable ports for fluid access may be features that are important in other applications., Comment: 10 figures

The common assumption that precision is the limit of accuracy in localization microscopy and the typical absence of comprehensive calibration of optical microscopes lead to a widespread issue - overconfidence in measurement results with nanoscale statistical uncertainties that can be invalid due to microscale systematic errors. In this article, we report a comprehensive solution to this underappreciated problem. We develop arrays of subresolution apertures into the first reference materials that enable localization errors approaching the atomic scale across a submillimeter field. We present novel methods for calibrating our microscope system using aperture arrays and develop aberration corrections that reach the precision limit of our reference materials. We correct and register localization data from multiple colors and test different sources of light emission with equal accuracy, indicating the general applicability of our reference materials and calibration methods. In a first application of our new measurement capability, we introduce the concept of critical dimension localization microscopy, facilitating tests of nanofabrication processes and quality control of aperture arrays. In a second application, we apply these stable reference materials to answer open questions about the apparent instability of fluorescent nanoparticles that commonly serve as fiducial markers. Our study establishes a foundation for subnanometer localization accuracy in widefield optical microscopy., Comment: Light: Science & Applications (2018) 7

Integrated-photonics microchips now enable a range of advanced functionalities for high-coherence applications such as data transmission, highly optimized physical sensors, and harnessing quantum states, but with cost, efficiency, and portability much beyond tabletop experiments. Through high-volume semiconductor processing built around advanced materials there exists an opportunity for integrated devices to impact applications cutting across disciplines of basic science and technology. Here we show how to synthesize the absolute frequency of a lightwave signal, using integrated photonics to implement lasers, system interconnects, and nonlinear frequency comb generation. The laser frequency output of our synthesizer is programmed by a microwave clock across 4 THz near 1550 nm with 1 Hz resolution and traceability to the SI second. This is accomplished with a heterogeneously integrated III/V-Si tunable laser, which is guided by dual dissipative-Kerr-soliton frequency combs fabricated on silicon chips. Through out-of-loop measurements of the phase-coherent, microwave-to-optical link, we verify that the fractional-frequency instability of the integrated photonics synthesizer matches the $7.0*10^{-13}$ reference-clock instability for a 1 second acquisition, and constrain any synthesis error to $7.7*10^{-15}$ while stepping the synthesizer across the telecommunication C band. Any application of an optical frequency source would be enabled by the precision optical synthesis presented here. Building on the ubiquitous capability in the microwave domain, our results demonstrate a first path to synthesis with integrated photonics, leveraging low-cost, low-power, and compact features that will be critical for its widespread use., Comment: 10 pages, 6 figures

Topological effects typically discussed in the context of quantum physics are emerging as one of the central paradigms of physics. Here, we demonstrate the role of topology in energy transport through dimerized micro- and nano-mechanical lattices in the classical regime, i.e., essentially "masses and springs". We show that the thermal conductance factorizes into topological and non-topological components. The former takes on three discrete values and arises due to the appearance of edge modes that prevent good contact between the heat reservoirs and the bulk, giving a length-independent reduction of the conductance. In essence, energy input at the boundary mostly stays there, an effect robust against disorder and nonlinearity. These results bridge two seemingly disconnected disciplines of physics, namely topology and thermal transport, and suggest ways to engineer thermal contacts, opening a direction to explore the ramifications of topological properties on nanoscale technology., Comment: 6 pages, 3 figures; Supplemental information included as an ancillary file

Microresonator frequency combs can be an enabling technology for optical frequency synthesis and timekeeping in low size, weight, and power architectures. Such systems require comb operation in low-noise, phase-coherent states such as solitons, with broad spectral bandwidths (e.g., octave-spanning) for self-referencing to detect the carrier-envelope offset frequency. However, stably accessing such states is complicated by thermo-optic dispersion. For example, in the Si3N4 platform, precisely dispersion-engineered structures can support broadband operation, but microsecond thermal time constants have necessitated fast pump power or frequency control to stabilize the solitons. In contrast, here we consider how broadband soliton states can be accessed with simple pump laser frequency tuning, at a rate much slower than the thermal dynamics. We demonstrate octave-spanning soliton frequency combs in Si3N4 microresonators, including the generation of a multi-soliton state with a pump power near 40 mW and a single-soliton state with a pump power near 120 mW. We also develop a simplified two-step analysis to explain how these states are accessed in a thermally stable way without fast control of the pump laser, and outline the required thermal properties for such operation. Our model agrees with experimental results as well as numerical simulations based on a Lugiato-Lefever equation that incorporates thermo-optic dispersion. Moreover, it also explains an experimental observation that a member of an adjacent mode family on the red-detuned side of the pump mode can mitigate the thermal requirements for accessing soliton states.

Acoustic wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (RF) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4 GHz RF waves to 194 THz (1550 nm) optical waves, through coupling to propagating and localized 2.4 GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the RF carrier are mapped to the optical field. We also show opto-acoustic modulation, in which the application of optical pulses gates the transmission of propagating acoustic waves. The time-domain characteristics of this system under both pulsed RF and pulsed optical excitation are considered in the context of the different physical pathways involved in driving the acoustic waves, and modeled through the coupled mode equations of cavity optomechanics., Comment: 8 pages, 6 figures

Both low frequency and high frequency impurity modes have been produced in a SiN micromechanical cantilever array by illumination with either an infrared or visible laser. When such laser-induced impurities are placed near a driven intrinsic localized mode (ILM) it is either repelled or attracted. By measuring the linear response spectrum for these two cases it was found that vibrational hopping of the ILM takes place when the natural frequency of the ILM and an even symmetry linear local mode are symmetrically located about the driven ILM frequency so that parametric excitation of these two linear modes is enhanced, amplifying the lateral motion of the ILM. Numerical simulations are consistent with these signature findings. It is also demonstrated that the correct sign of the observed interaction can be found with a harmonic lattice-impurity model but the magnitude of the effect is enhanced in a nonlinear lattice., Comment: to be published in CHAOS

We have fabricated and tested mechanical resonators consisting of a single-atomic-layer of graphene deposited on suspended silicon nitride membranes. With the addition of the graphene layer we retain the desirable mechanical properties of silicon nitride but utilize the electrical and optical properties of graphene to transduce resonant motion by both optical and electrical means. By positioning the graphene-on-silicon-nitride drums in a tunable optical cavity we observe position dependent damping and resonant frequency control of the devices due to optical absorption by graphene.

High stress stoichiometric silicon nitride resonators, whose quality factors exceed one million, have shown promise for applications in sensing and signal processing. Yet, electrical integration of the insulating silicon nitride resonators has been challenging, as depositing even a thin layer of metal degrades the quality factor significantly. In this work, we show that graphene used as a conductive coating for Si3N4 membranes reduces the quality factor by less than 30 % on average, which is minimal when compared to the effect of conventional metallization layers such as chromium or aluminum. The electrical integration of Si3N4-Graphene (SiNG) heterostructure resonators is demonstrated with electrical readout and electro-static tuning of the frequency by up to 1 % per volt. These studies demonstrate the feasibility of hybrid graphene/nitride mechanical resonators in which the electrical properties of graphene are combined with the superior mechanical performance of silicon nitride., Comment: 8 pages, 5 figures, journal

Linear response spectra of a driven intrinsic localized mode in a micromechanical array are measured as it approaches two fundamentally different kinds of bifurcation points. A linear phase mode associated with this autoresonant state softens in frequency and its amplitude grows as the upper frequency bifurcation point is approached, similar to the soft mode kinetic transition for a single driven Duffing resonator. A lower frequency bifurcation point occurs when the four-wave-mixing partner of this same phase mode intercepts the top of the extended wave branch, initiating a second kinetic transition process., Comment: 4 pages, 5 figures. Accepted to PRL

Mechanical dissipation poses an ubiquitous challenge to the performance of nanomechanical devices. Here we analyze the support-induced dissipation of high-stress nanomechanical resonators. We develop a model for this loss mechanism and test it on silicon nitride membranes with circular and square geometries. The measured Q-values of different harmonics present a non-monotonic behavior which is successfully explained. For azimuthal harmonics of the circular geometry we predict that destructive interference of the radiated waves leads to an exponential suppression of the clamping loss in the harmonic index. Our model can also be applied to graphene drums under high tension., Comment: 8 pages, 1 figure

The manipulation of geometrically constrained magnetic domain walls (DWs) in nanoscale magnetic strips has attracted much interest recently, with proposals for prospective memory and logic devices. Here we propose to use the high controllability of the motion of geometrically constrained DWs for the manipulation of individual nanoparticles on a chip with an active control of position at the nanometer scale. The proposed method exploits the fact that magnetic nanoparticles in solution can be captured by a DW, whose position can be manipulated with nanometric accuracy in a specifically designed magnetic nanowire structure. We show that the high control over DW nucleation, displacement, and annihilation processes in such structures can be used to capture, transport and release magnetic nanoparticles. As magnetic particles with functionalized surfaces are commonly used as molecule labels in several applications - including single molecule manipulation, separation, cells manipulation and biomagnetic sensing, the accurate control over the handling of the single magnetic nanoparticles becomes crucial as it may reflect the handling of the single molecules. The approach described here opens the path to the implementation and design of nano-transport lines, with application to single molecule study and lab-on-chip devices. In perspective, the easy integration on chip with sensors of domain walls and particles will allow for the realization of programmable circuits for molecular manipulation with continuous control of the desired process.

The manipulation of geometrically constrained magnetic domain walls (DWs) in nanoscale magnetic strips has attracted much interest recently, with proposals for prospective memory and logic devices. Here we propose to use the high controllability of the motion of geometrically constrained DWs for the manipulation of individual nanoparticles on a chip with an active control of position at the nanometer scale. The proposed method exploits the fact that magnetic nanoparticles in solution can be captured by a DW, whose position can be manipulated with nanometric accuracy in a specifically designed magnetic nanowire structure. We show that the high control over DW nucleation, displacement, and annihilation processes in such structures can be used to capture, transport and release magnetic nanoparticles. As magnetic particles with functionalized surfaces are commonly used as molecule carriers or labels, the accurate control over the handling of the single magnetic nanoparticle is crucial for several applications including single molecule manipulation, separation, cells manipulation and biomagnetic sensing.

The vortex dynamics in a low temperature superconductor deposited on top of a rectangular array of micrometer size permalloy triangles is investigated experimentally. The rectangular unit cell is such that neighboring triangles physically touch each other along one direction. This design stabilizes remanent states which differ from the magnetic vortex state typical of individual non-interacting triangles. Magnetic Force Microscopy images have revealed that the magnetic landscape of the template can be switched to an ordered configuration after magnetizing the sample with an in-plane field. The ordered phase exhibits a broad flux flow regime with relatively low critical current and a highly anisotropic response. This behavior is caused by the spontaneous formation of two separated rows of vortices and antivortices along each line of connected triangles. The existence of a clear flux flow regime even for zero external field supports this interpretation. The density of induced vortex-antivortex pairs is directly obtained using a high frequency measurement technique which allows us to resolve the discrete motion of vortices. Strikingly, the presence of vortex-antivortex rows gives rise to a self organized synchronized motion of vortices which manifests itself as field independent Shapiro steps in the current-voltage characteristics., Comment: 9 pages, 11 figures

We present evidence of magnetically controlled guided vortex motion in a hybrid superconductor/ferromagnet nanosystem consisting of an Al film on top of a square array of permalloy square rings. When the rings are magnetized with an in-plane external field H, an array of point-like dipoles with moments antiparallel to H, is formed. The resulting magnetic template generates a strongly anisotropic pinning potential landscape for vortices in the superconducting layer. Transport measurements show that this anisotropy is able to confine the flux motion along the high symmetry axes of the square lattice of dipoles. This guided vortex motion can be either re-routed by 90 degrees by simply changing the dipole orientation or even strongly suppressed by inducing a flux-closure magnetic state with very low stray fields in the rings., Comment: 5 pages, 3 figures

We investigate the transport properties of superconducting films with periodic arrays of in-plane magnetized micromagnets. Two different magnetic textures are studied: a square array of magnetic bars and a close-packed array of triangular microrings. As confirmed by MFM imaging, the magnetic state of both systems can be adjusted to produce arrays of almost point-like magnetic dipoles. By carrying out transport measurements with ac drive, we observed experimentally a recently predicted ratchet effect induced by the interaction between superconducting vortices and the magnetic dipoles. Moreover, we find that these magnetic textures produce vortex-antivortex patterns, which have a crucial role on the transport properties of this hybrid system., Comment: 4 pages, 4 figures

We study the flux pinning properties of superconductor/magnetic micro-rings lattice hybrid structures. The used open triangular micromagnets represent an eight-fold degree of freedom system, with six polarized and two flux-closure possible states. By conveniently choosing the magnetic state of the underlying rings it is possible to induce different pinning potentials. We show that the magnetic vortex state with minimum stray field produces a weaker pinning in comparison with the polarized states.

Magnetization reversal mechanisms and impact of magnetization direction are studied in square arrays of interconnected circular permalloy nanorings using MOKE, local imaging, numerical simulations and transport techniques.

Optically-induced real-time impurity modes are used to shepherd intrinsic localized vibrational modes (discrete breathers) along micromechanical arrays via either attractive or replulsive interactions. Adding an electrode to the cantilever array provides control of the sign of lattice anharmonicity, hence allowing both hard and soft nonlinearities to be studied. A number of dynamical effects are demonstrated and explained, including the optical tweezing of localized vibrational energy in a nonlinear lattice., Comment: 11 pages, 4 figures to be published in Europhysics Letters

We study the interactions of the vortex lattice with a periodic square array of holes in a superconducting Nb film using magnetic and resistive measurements. Three different temperature regions have been observed. They are governed by interplay between vortex-vortex interactions and pinning by holes. At low temperatures flux jumps suppress the commensurability anomalies. In all measurements a peak has been observed close to commensurate states 5-7. The Cole-Cole plot reveals significant changes in the flux penetration mechanism at this point., Comment: 12 pages, 5 figures

A simple scheme to extract the magnetization reversals of characteristic magnetic domains on nanofabricated periodic arrays from soft x-ray resonant magnetic scattering (SXRMS) data is presented. The SXRMS peak intensities from a permalloy square ring array were measured with field cycling using circularly polarized soft x-rays at the Ni L$_3$ absorption edge. Various SXRMS hysteresis loops observed at different diffraction orders enabled the determination of the magnetization reversal of each magnetic domain using a simple linear algebra. The extracted domain-specific hysteresis loops reveal that the magnetization of the domain parallel to the field is strongly pinned, while that of the perpendicular domain rotates continuously., Comment: 4 pages, 4 figures

We study the interactions of the vortex lattice with a periodic square array of holes in a superconducting Nb film. Using high resolution magnetic field measurements of electrical losses, extremely narrow states with a magnetic field width reaching 1% of the matching field value are found at the commensurate points. They are accompanied by pronounced harmonic generation in response to ac modulation of the magnetic field or current. We relate these sharp anomalies to a locked commensurate state of the Mott insulator type., Comment: 7 pages, 4 figures

High-resolution scanning Hall probe microscopy has been used to image vortex configurations in very large periodic arrays of artificial pinning sites. Strong matching effects are seen at fields where either one or two vortices can sit at a site; with three vortices per site, however, no clear matching is observed. Matching effects have been also been observed at several fractional multiples of the matching field, including 1/5, 1/4, 1/3, 1/2, and 3/4. These fractional values are characterized by striking domain structure and grain boundaries., Comment: 4 pages, 5 figures