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Analog coupled oscillator based weighted Ising machine

Summary

We report on an analog computing system with coupled non-linear oscillators which is capable of solving complex combinatorial optimization problems using the weighted Ising model. The circuit is composed of a fully-connected 4-node LC oscillator network with low-cost electronic components and compatible with traditional integrated circuit technologies. We present the theoretical modeling, experimental characterization, and statistical analysis our system, demonstrating single-run ground state accuracies of 98% on randomized MAX-CUT problem sets with binary weights and 84% with 5-bit weight resolutions. Solutions are obtained within 5 oscillator cycles, and the time-to-solution has been demonstrated to scale directly with oscillator frequency. We present scaling analysis which suggests that large coupled oscillator networks may be used to solve computationally intensive problems faster and more efficiently than conventional algorithms. The proof-of-concept system presented here provides the foundation for realizing such larger scale systems using existing hardware technologies and could pave the way towards an entirely novel computing paradigm.
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Summary

We report on an analog computing system with coupled non-linear oscillators which is capable of solving complex combinatorial optimization problems using the weighted Ising model. The circuit is composed of a fully-connected 4-node LC oscillator network with low-cost electronic components and compatible with traditional integrated circuit technologies. We present the...

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Design, simulation, and fabrication of three-dimensional microsystem components using grayscale photolithography

Summary

Grayscale lithography is a widely known but underutilized microfabrication technique for creating three-dimensional (3-D) microstructures in photoresist. One of the hurdles for its widespread use is that developing the grayscale photolithography masks can be time-consuming and costly since it often requires an iterative process, especially for complex geometries. We discuss the use of PROLITH, a lithography simulation tool, to predict 3-D photoresist profiles from grayscale mask designs. Several examples of optical microsystems and microelectromechanical systems where PROLITH was used to validate the mask design prior to implementation in the microfabrication process are presented. In all examples, PROLITH was able to accurately and quantitatively predict resist profiles, which reduced both design time and the number of trial photomasks, effectively reducing the cost of component fabrication.
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Summary

Grayscale lithography is a widely known but underutilized microfabrication technique for creating three-dimensional (3-D) microstructures in photoresist. One of the hurdles for its widespread use is that developing the grayscale photolithography masks can be time-consuming and costly since it often requires an iterative process, especially for complex geometries. We discuss...

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Chip-scale molecular clock

Published in:
IEEE J. Solid-State Circuits, Vol. 54, No. 4, April 2019, pp. 914-26.

Summary

An ultra-stable time-keeping device is presented, which locks its output clock frequency to the rotational-mode transition of polar gaseous molecules. Based on a high-precision spectrometer in the sub-terahertz (THz) range, our new clocking scheme realizes not only fully electronic operation but also implementations using mainstream CMOS technology. Meanwhile, the small wavelength of probing wave and high absorption intensity of our adopted molecules (carbonyl sulfide, 16O12C32S) also enable miniaturization of the gas cell. All these result in an "atomic-clock-grade" frequency reference with small size, power, and cost. This paper provides the architectural and chip-design details of the first proof-of-concept molecular clock using a 65-nm CMOS bulk technology. Using a 231.061-GHz phase-locked loop (PLL) with frequency-shift keying (FSK) modulation and a sub-THz FET detector with integrated lock-in function, the chip probes the accurate transition frequency of carbonyl sulfide (OCS) gas inside a single-mode waveguide, and accordingly adjusts the 80-MHz output of a crystal oscillator. The clock consumes only 66 mW of dc power and has a measured Allan deviation of 3.8 × 10^−10 at an averaging time of tau = 1000 s.
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Summary

An ultra-stable time-keeping device is presented, which locks its output clock frequency to the rotational-mode transition of polar gaseous molecules. Based on a high-precision spectrometer in the sub-terahertz (THz) range, our new clocking scheme realizes not only fully electronic operation but also implementations using mainstream CMOS technology. Meanwhile, the small...

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Linear and rotational microhydraulic actuators driven by electrowetting

Published in:
Sci. Robot., Vol. 3, No. 22, 19 September 2018.

Summary

Microhydraulic actuators offer a new way to convert electrical power to mechanical power on a microscale with an unmatched combination of power density and efficiency. Actuators work by combining surface tension force contributions from a large number of droplets distorted by electrowetting electrodes. This paper reports on the behavior of microgram-scale linear and rotational microhydraulic actuators with output force/weight ratios of 5500, cycle frequencies of 4 kilohertz, <1-micrometer movement precision, and accelerations of 3 kilometers/second. The power density and the efficiency of the actuators were characterized by simultaneously measuring the mechanical work performed and the electrical power applied. Maximum output power density was 0.93 kilowatt/kilogram, comparable with the best electric motors. At maximum power, the actuator was 60% efficient, but efficiencies were as high as 83% at lower power. Rotational actuators demonstrated a torque density of 79 newton meters/kilogram, substantially more than electric motors of comparable diameter. Scaling the droplet pitch from 100 to 48 micrometers increased power density from 0.27 to 0.93 kilowatt/kilogram, validating the quadratic scaling of actuator power.
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Summary

Microhydraulic actuators offer a new way to convert electrical power to mechanical power on a microscale with an unmatched combination of power density and efficiency. Actuators work by combining surface tension force contributions from a large number of droplets distorted by electrowetting electrodes. This paper reports on the behavior of...

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Valleytronics: opportunities, challenges, and paths forward

Summary

A lack of inversion symmetry coupled with the presence of time-reversal symmetry endows 2D transition metal dichalcogenides with individually addressable valleys in momentum space at the K and K' points in the first Brillouin zone. This valley addressability opens up the possibility of using the momentum state of electrons, holes, or excitons as a completely new paradigm in information processing. The opportunities and challenges associated with manipulation of the valley degree of freedom for practical quantum and classical information processing applications were analyzed during the 2017 Workshop on Valleytronic Materials, Architectures, and Devices; this Review presents the major findings of the workshop.
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Summary

A lack of inversion symmetry coupled with the presence of time-reversal symmetry endows 2D transition metal dichalcogenides with individually addressable valleys in momentum space at the K and K' points in the first Brillouin zone. This valley addressability opens up the possibility of using the momentum state of electrons, holes...

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Rapid Quantitative Analysis of Multiple Explosive Compound Classes on a Single Instrument via Flow-Injection Analysis Tandem Mass Spectrometry

Summary

A flow-injection analysis tandem mass spectrometry (FIA MSMS) method was developed for rapid quantitative analysis of 10 different inorganic and organic explosives. Performance is optimized by tailoring the ionization method (APCI/ESI), de-clustering potentials, and collision energies for each specific analyte. In doing so, a single instrument can be used to detect urea nitrate, potassium chlorate, 2,4,6-trinitrotoluene, 2,4,6-trinitrophenylmethylnitramine, triacetone triperoxide, hexamethylene triperoxide diamine, pentaerythritol tetranitrate, 1,3,5-trinitroperhydro-1,3,5-triazine, nitroglycerin, and octohy-dro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine with sensitivities all in the picogram per milliliter range. In conclusion, FIA APCI/ESI MSMS is a fast (<1 min/sample), sensitive (~pg/mL LOQ), and precise (intraday RSD < 10%) method for trace explosive detection that can play an important role in criminal and attributional forensics, counterterrorism, and environmental protection areas, and has the potential to augment or replace several of the existing explosive detection methods.
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Summary

A flow-injection analysis tandem mass spectrometry (FIA MSMS) method was developed for rapid quantitative analysis of 10 different inorganic and organic explosives. Performance is optimized by tailoring the ionization method (APCI/ESI), de-clustering potentials, and collision energies for each specific analyte. In doing so, a single instrument can be used to...

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Optical Nondestructive Dynamic Measurements of Wafer-Scale Encapsulated Nanofluidic Channels

Published in:
Applied Optics, vol. 57, no. 15

Summary

Nanofluidic channels are of great interest for DNA sequencing, chromatography, and drug delivery. However, metrology of embedded or sealed nanochannels and measurement of their fill-state have remained extremely challenging. Existing techniques have been restricted to optical microscopy, which suffers from insufficient resolution, or scanning electron microscopy, which cannot measure sealed or embedded channels without cleaving the sample. Here, we demonstrate a novel method for accurately extracting nanochannel cross-sectional dimensions and monitoring fluid filling, utilizing spectroscopic ellipsometric scatterometry, combined with rigorous electromagnetic simulations. Our technique is capable of measuring channel dimensions with better than 5-nm accuracy and assessing channel filling within seconds. The developed technique is, thus, well suited for both process monitoring of channel fabrication as well as for studying complex phenomena of fluid flow through nanochannel structures.
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Summary

Nanofluidic channels are of great interest for DNA sequencing, chromatography, and drug delivery. However, metrology of embedded or sealed nanochannels and measurement of their fill-state have remained extremely challenging. Existing techniques have been restricted to optical microscopy, which suffers from insufficient resolution, or scanning electron microscopy, which cannot measure sealed...

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Highly Efficient All-Optical Beam Modulation Utilizing Thermo-optic Effects

Summary

Suspensions of plasmonic nanoparticles can diffract optical beams due to the combination of thermal lensing and self-phase modulation. Here, we demonstrate extremely efficient optical continuous wave (CW) beam switching across the visible range in optimized suspensions of 5-nm Au and Ag nanoparticles in non-polar solvents, such as hexane and decane. On-axis modulation of greater than 30 dB is achieved at incident beam intensities as low as 100 W/cm2 with response times under 200 μs, at initial solution transparency above 70%. No evidence of laser-induced degradation is observed for the highest intensities used. Numerical modeling of experimental data reveals thermo-optic coefficients of up to −1.3 × 10−3 /K, which, to our knowledge, is the highest observed to date in such nanoparticle suspensions.
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Summary

Suspensions of plasmonic nanoparticles can diffract optical beams due to the combination of thermal lensing and self-phase modulation. Here, we demonstrate extremely efficient optical continuous wave (CW) beam switching across the visible range in optimized suspensions of 5-nm Au and Ag nanoparticles in non-polar solvents, such as hexane and decane...

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Microsputterer with integrated ion-drag focusing for additive manufacturing of thin, narrow conductive lines

Published in:
J. Phys. D.: Appl. Phys., Vol. 51, 2018, 165603.

Summary

We report the design, modelling, and proof-of-concept demonstration of a continuously fed, atmospheric-pressure microplasma metal sputterer that is capable of printing conductive lines narrower than the width of the target without the need for post-processing or lithographic patterning. Ion drag-induced focusing is harnessed to print narrow lines; the focusing mechanism is modelled via COMSOL Multiphysics simulations and validated with experiments. A microplasma sputter head with gold target is constructed and used to deposit imprints with minimum feature sizes as narrow as 9 μm, roughness as small as 55 nm, and electrical resistivity as low as 1.1 mu Omega · m.
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Summary

We report the design, modelling, and proof-of-concept demonstration of a continuously fed, atmospheric-pressure microplasma metal sputterer that is capable of printing conductive lines narrower than the width of the target without the need for post-processing or lithographic patterning. Ion drag-induced focusing is harnessed to print narrow lines; the focusing mechanism...

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Large-format Geiger-mode avalanche photodiode arrays and readout circuits

Published in:
IEEE J. Sel. Top. Quantum Electron., Vol. 24, No. 2, March/April 2018, 3800510.

Summary

Over the past 20 years, we have developed arrays of custom-fabricated silicon and InP Geiger-mode avalanche photodiode arrays, CMOS readout circuits to digitally count or time stamp single-photon detection events, and techniques to integrate these two components to make back-illuminated solid-state image sensors for lidar, optical communications, and passive imaging. Starting with 4 × 4 arrays, we have recently demonstrated 256 × 256 arrays, and are working to scale to megapixel-class imagers. In this paper, we review this progress and discuss key technical challenges to scaling to large format.
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Summary

Over the past 20 years, we have developed arrays of custom-fabricated silicon and InP Geiger-mode avalanche photodiode arrays, CMOS readout circuits to digitally count or time stamp single-photon detection events, and techniques to integrate these two components to make back-illuminated solid-state image sensors for lidar, optical communications, and passive imaging...

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