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Applied Physics

New submissions

[ total of 15 entries: 1-15 ]
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New submissions for Tue, 20 Mar 18

[1]  arXiv:1803.06427 [pdf]
Title: Nonlinear nano-electromechanical lattices for high-frequency, tunable stress propagation
Subjects: Applied Physics (physics.app-ph)

Active manipulation of mechanical waves at high frequencies opens opportunities in heat management, radio-frequency (RF) signal processing, and quantum technologies. Nanoelectromechanical systems (NEMS) are appropriate platforms for developing these technologies, offering energy transducibility between different physical domains, for example, converting optical or electrical signals into mechanical vibrations and viceversa. Existing NEMS platforms, however, are mostly linear, passive, and not dynamically controllable. Here, we report the realization of active manipulation of frequency band dispersion in one-dimensional (1D) nonlinear nanoelectromechanical lattices (NEML) in the RF domain (10-30 MHz). Our NEML is comprised of a periodic arrangement of mechanically coupled free-standing nano-membranes, with circular clamped boundaries. This design forms a flexural phononic crystals with a well-defined band gaps, 1.8 MHz wide. The application a DC gate voltage creates voltage-dependent on-site potentials, which can significantly shift the frequency bands of the device. Dynamic modulation of the voltage triggers nonlinear effects, which induce the formation of phononic band gaps in the acoustic branch. These devices could be used in tunable filters, ultrasonic delay lines and transducers for implantable medical devices.

[2]  arXiv:1803.06462 [pdf, other]
Title: 500MHz resonant photodetector for high-frequency, high-quantum-effciency, low-noise homodyne measurement
Comments: 7 pages, 11 figures
Subjects: Applied Physics (physics.app-ph); Quantum Physics (quant-ph)

We design and demonstrate a resonant-type differential photodetector, for high-frequency, high-quantum-efficiency, low-noise quantum homodyne measurement at 500MHz optical sideband. By using a microwave monolithic amplifier and a discrete voltage buffer circuit, a low-noise voltage amplifier is realized and applied to our detector. 12dB of signal-to-noise ratio of the shot noise to the electric noise is obtained with 5mW of continuous-wave local oscillator at 860nm. We analyze the frequency response and the noise characteristics of a resonant photodetector, and the theoretical model agrees with the shot noise measurement.

[3]  arXiv:1803.06526 [pdf]
Title: Titanium diboride ceramics for solar thermal absorbers
Journal-ref: Solar Energy Materials and Solar Cells, Volume 169 (2017) Pages 313-319
Subjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci)

Titanium diboride (TiB2) is a low-density refractory material belonging to the family of ultra-high temperature ceramics (UHTCs). This paper reports on the production and microstructural and optical characterization of nearly fully dense TiB2, with particular interest to its potential utilization as novel thermal solar absorber. Monolithic bulk samples are produced starting from elemental reactants by a two-step method consisting of the Self-propagating High-temperature Synthesis (SHS) followed by the Spark Plasma Sintering (SPS) of the resulting powders. The surface of obtained samples has-been characterized from the microstructural and topological points of view. The hemispherical reflectance spectrum has been measured from 0.3 to 15 um wavelength, to evaluate the potential of this material as solar absorber for future concentrating solar plants.

[4]  arXiv:1803.06546 [pdf, other]
Title: Microscale resolution thermal mapping using a flexible platform of patterned quantum sensors
Comments: 15 pages, 4 figures
Subjects: Applied Physics (physics.app-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

Temperature sensors with micro- and nanoscale spatial resolution have long been explored for their potential to investigate the details of physical systems at an unprecedented scale. In particular, the rapid miniaturization of transistor technology, with the associated steep boost in power density, calls for sensors that accurately monitor heating distributions. Here, we report on a simple and scalable fabrication approach, based on directed self-assembly and transfer printing techniques, to construct arrays of nanodiamonds containing temperature sensitive fluorescent spin defects. The nanoparticles are embedded within a low thermal conductivity matrix that allows for repeated use on a wide range of systems with minimal spurious effects. Additionally, we demonstrate access to a wide spectrum of array parameters ranging from sparser single particle arrays to denser devices with approximately 100 % yield and stronger photoluminescence signal, ideal for temperature measurements. With these we experimentally reconstruct the temperature map of an operating coplanar waveguide to confirm the accuracy of these platforms.

[5]  arXiv:1803.06551 [pdf]
Title: A new elliptical-beam method based on time-domain thermoreflectance (TDTR) to measure the in-plane anisotropic thermal conductivity and its comparison with the beam-offset method
Comments: 35 pages, 12 figures, submitted to RSI
Subjects: Applied Physics (physics.app-ph)

Materials lacking in-plane symmetry are ubiquitous in a wide range of applications such as electronics, thermoelectrics, and high-temperature superconductors, in all of which the thermal properties of the materials play a critical part. However, very few experimental techniques can be used to measure in-plane anisotropic thermal conductivity. A beam-offset method based on time-domain thermoreflectance (TDTR) was previously proposed to measure in-plane anisotropic thermal conductivity. However, a detailed analysis of the beam-offset method is still lacking. Our analysis shows that uncertainties can be large if the laser spot size or the modulation frequency is not properly chosen. Here we propose an alternative approach based on TDTR to measure in-plane anisotropic thermal conductivity using a highly elliptical pump (heating) beam. The highly elliptical pump beam induces a quasi-one-dimensional temperature profile on the sample surface that has a fast decay along the short axis of the pump beam. The detected TDTR signal is exclusively sensitive to the in-plane thermal conductivity along the short axis of the elliptical beam. By conducting TDTR measurements as a function of delay time with the rotation of the elliptical pump beam to different orientations, the in-plane thermal conductivity tensor of the sample can be determined. In this work, we first conduct detailed signal sensitivity analyses for both techniques and provide guidelines in determining the optimal experimental conditions. We then compare the two techniques under their optimal experimental conditions by measuring the in-plane thermal conductivity tensor of a ZnO [11-20] sample. The accuracy and limitations of both methods are discussed.

[6]  arXiv:1803.06562 [pdf, other]
Title: Nanoscale domain patterns and a concept for an energy harvester
Comments: 8 pages, 9 figures
Journal-ref: Smart Materials and Structures, 25(10), 104001 (2016)
Subjects: Applied Physics (physics.app-ph)

The current work employs a phase-field model to test the stability of nanoscale periodic domain patterns, and to explore the application of one pattern in an energy harvester device. At first, the stability of several periodic domain patterns with in-plane polarizations is tested under stress-free and electric field-free conditions. It is found that simple domain patterns with stripe-like features are stable, while patterns with more complex domain configurations are typically unstable at the nanoscale. Upon identifying a stable domain pattern with suitable properties, a conceptual design of a thin film energy harvester device is explored. The harvester is modelled as a thin ferroelectric film bound to a substrate. In the initial state a periodic stripe domain pattern with zero net charge on the top electrode is modelled. On bending the substrate, a mechanical strain is induced in the film, causing polarized domains to undergo ferroelectric switching and thus generate electrical energy. The results demonstrate the working cycle of a conceptual energy harvester which, on operating at kHz frequencies, such as from vibrations in the environment, could produce an area power density of about 40W/m2.

[7]  arXiv:1803.07028 [pdf, ps, other]
Title: Speckle characterization in a cinematography projection configuration
Subjects: Applied Physics (physics.app-ph)

Due to high exploitation costs and other environmental issues, it would be desirable to phase out large cinema projection systems based on standard xenon lamps in favor of laser based projection devices. Lasers provide longer lifetime and wider color gamut of light output. But the high degree of coherence of these sources also lead to the formation of granular structures, usually known as speckle. When an imaging system is involved, as in the cinema projection case because of the capacity of the human eye to form an image of the screen, we speak about subjective speckle. In order to remove this spatial random pattern, different methods have been studied as temporal and/or spatial coherence reduction. But most of them can't be used in the context of cinema projection because they don't respect the cinematography projection standard. In our work, we have studied the possibility to reduce the subjective speckle either by changing the coherence of the light source or by studying the influence of the different elements constituting the projection display in the conditions imposed by cinematography industry. Thanks to a lasers array formed by N independant semiconductor lasers, we have measured the evolution of the subjective speckle contrast in function of the number of sources. The resulting contrast discreases as a square root function and reach a saturation level when a light pipe is used. This behavior is directly due to the light pipe which limit at its output the spatial coherence of the source. Futhermore, in a different configuration, we have studied the influence of diffusers and the magnification of the projector zoom. It has been demonstrated that magnification plays an important role on the speckle formation because it increases the coherence length determined by the light pipe. On the contrary, the diffusers placed before the light pipe doesn't change the subjective speckle.

[8]  arXiv:1803.07065 [pdf]
Title: Sensorless Resonance Tracking of Resonant Electromagnetic Actuator through Back-EMF Estimation for Mobile Devices
Authors: Youngjun Cho
Subjects: Applied Physics (physics.app-ph); Systems and Control (cs.SY); Signal Processing (eess.SP); Dynamical Systems (math.DS)

Resonant electromagnetic actuators have been broadly used as vibration motors for mobile devices given their ability of generating relatively fast, strong, and controllable vibration force at a given resonant frequency. Mechanism of the actuators that is based on mechanical resonance, however, limits their use to a situation where their resonant frequencies are known and unshifted. In reality, there are many factors that alter the resonant frequency: for example, manufacturing tolerances, worn mechanical components such as a spring, nonlinearity in association with different input voltage levels. Here, we describe a sensorless resonance tracking method that actuates the motor and automatically detects its unknown damped natural frequency through the estimation of back electromotive force (EMF) and inner mass movements. We demonstrate the tracking performance of the proposed method through a series of experiments. This approach has the potential to control residual vibrations and then improve vibrotactile feedback, which can potentially be used for human-computer interaction, cognitive and affective neuroscience research.

Cross-lists for Tue, 20 Mar 18

[9]  arXiv:1803.06433 (cross-list from cond-mat.mtrl-sci) [pdf]
Title: Thermal conduction of one-dimensional carbon nanomaterials and nanoarchitectures
Comments: 10 pages, 10 figures
Journal-ref: Chin. Phys. B, 2018, 27 (3): 038103
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

This review summarizes the current studies of the thermal transport properties of one-dimensional (1D) carbon nanomaterials and nanoarchitectures. Considering different hybridization states of carbon, emphases are laid on a variety of 1D carbon nanomaterials, such as diamond nanothreads, penta-graphene nanotubes, supernanotubes, and carbyne. Based on experimental measurements and simulation/calculation results, we discuss the dependence of the thermal conductivity of these 1D carbon nanomaterials on a wide range of factors, including the size effect, temperature influence, strain effect, and others. This review provides an overall understanding of the thermal transport properties of 1D carbon nanomaterials and nanoarchitectures, which paves the way for effective thermal management at nanoscale.

[10]  arXiv:1803.06435 (cross-list from cond-mat.mtrl-sci) [pdf]
Title: Chapter 7 - Thermal Conductivity of Diamond Nanothread
Comments: 19 pages, 13 figures
Journal-ref: A volume in Micro and Nano Technologies, 2017, Pages 185-204
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

This chapter introduces the thermal conductivity of a novel one-dimensional carbon nanostructure - diamond nanothread. It starts by introducing the family of the diamond nanothread as acquired from density functional theory calculations and also its successful experimental synthesisation. It then briefs the mechanical properties of the diamond nanothreads as a fundamental for their engineering applications. After that, it focuses on the thermal transport properties of the diamond nanothreads by examining the influences from various parameters such as size, geometry, and temperature. Then, the application of diamond nanothread as reinforcements for nanocomposites is discussed. By the end of the chapter, future directions and their potential applications are discussed.

[11]  arXiv:1803.06437 (cross-list from cond-mat.mtrl-sci) [pdf]
Title: Graphene and Carbon Nanotube Hybrid Structure: A Review
Comments: 8 pages, 7 figures
Journal-ref: Procedia IUTAM,Volume 21, 2017, Pages 94-101
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

Graphene has been reported with record-breaking properties which have opened up huge potential applications. Considerable amount of researches have been devoted to manipulating or modify the properties of graphene to target a more smart nanoscale device. Graphene and carbon nanotube hybrid structure (GNHS) is one of the promising graphene derivate. The synthesis process and the mechanical properties are essential for the GNHS based devices. Therefore, this review will summarise the recent progress of the highly ordered GNHS synthesis/assembly, and discuss the mechanical properties of GNHS under various conditions as obtained from molecular dynamics simulations.

[12]  arXiv:1803.06440 (cross-list from cond-mat.mtrl-sci) [pdf]
Title: Failure mechanism of monolayer graphene under hypervelocity impact of spherical projectile
Comments: 10 pages, 9 figures
Journal-ref: Scientific Reports volume 6, Article number: 33139 (2016)
Subjects: Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph)

The excellent mechanical properties of graphene have enabled it as appealing candidate in the field of impact protection or protective shield. By considering a monolayer graphene membrane, in this work, we assessed its deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on a serial of in silico studies. It is found that the cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation. Specifically, the boundary condition is found to exert an obvious influence on the stress distribution and transmission during the impact process, which eventually influences the penetration energy and crack growth. For similar sample size, the circular shape graphene possesses the best impact resistance, followed by hexagonal graphene membrane. Moreover, it is found the failure shape of graphene membrane has a strong relationship with the initial kinetic energy of the projectile. The higher kinetic energy, the more number the cracks. This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft.

[13]  arXiv:1803.07014 (cross-list from quant-ph) [pdf, other]
Title: Two-photon interference in the telecom C-band after frequency conversion of photons from remote quantum emitters
Authors: Jonas H. Weber (1), Benjamin Kambs (2), Jan Kettler (1), Simon Kern (1), Julian Maisch (1), Hüseyin Vural (1), Michael Jetter (1), Simone L. Portalupi (1), Christoph Becher (2), Peter Michler (1) ((1) Institut für Halbleiteroptik und Funktionelle Grenzflächen, Center for Integrated Quantum Science and Technology (IQST) and SCoPE, University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany, (2) Fachrichtung Physik, Universität des Saarlandes, Campus E 2.6, 66123 Saarbrücken, Germany)
Comments: J. H. Weber and B. Kambs contributed equally to this work
Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Applied Physics (physics.app-ph); Optics (physics.optics)

Efficient fiber-based long-distance quantum communication via quantum repeaters relies on deterministic single-photon sources at telecom wavelengths, with the potential to exploit the existing world-wide infrastructures. For upscaling the experimental complexity in quantum networking, two-photon interference (TPI) of remote non-classical emitters in the low-loss telecom bands is of utmost importance. With respect to TPI of distinct emitters, several experiments have been conducted, e.g., using trapped atoms [Beugnon2006], ions [Maunz2007], NV-centers [Bernien2012, Sipahigil2012], SiV-centers [Sipahigil2014], organic molecules [Lettow2010] and semiconductor quantum dots (QDs) [Patel2010, Flagg2010, He2013b, Gold2014, Giesz2015, Thoma2017, Reindl2017, Zopf2017]; however, the spectral range was far from the highly desirable telecom C-band. Here, we report on TPI at 1550 nm between down-converted single photons from remote QDs [Michler2017Book], demonstrating quantum frequency conversion [Zaske2012, Ates2012, Kambs2016] as precise and stable mechanism to erase the frequency difference between independent emitters. On resonance, a TPI-visibility of (29+-3)% has been observed, being only limited by spectral diffusion processes of the individual QDs [Robinson2000, Kuhlmann2015]. Up to 2-km of additional fiber channel has been introduced in both or individual signal paths with no influence on TPI-visibility, proving negligible photon wave-packet distortion. The present experiment is conducted within a local fiber network covering several rooms between two floors of the building. Our studies pave the way to establish long-distance entanglement distribution between remote solid-state emitters including interfaces with various quantum hybrid systems [DeGreve2012,Maring2017,Bock2017,Maring2018].

[14]  arXiv:1803.07047 (cross-list from cond-mat.str-el) [pdf, other]
Title: Electromagnetic response of quantum Hall systems in dimensions five and six and beyond
Comments: 18 pages, 4 figures
Subjects: Strongly Correlated Electrons (cond-mat.str-el); Applied Physics (physics.app-ph)

Quantum Hall (QH) states are arguably the most ubiquitous examples of nontrivial topological order, requiring no special symmetry and elegantly characterized by the first Chern number. Their higher dimension generalizations are particularly interesting from both mathematical and phenomenological perspectives, and have attracted recent attention due to a few high profile experimental realizations. In this work, we derive from first principles the electromagnetic response of QH systems in arbitrary number of dimensions, and elaborate on the crucial roles played by their modified phase space density of states under the simultaneous presence of magnetic field and Berry curvature. Besides providing new mathematical results relating this phase space modification to the non-commutativity of phase space, we also show how it produces a non-topological response current at leading order, in addition to the well-known topological contributions. This unconventional response appear only in five, six or more dimensions, and can be directly investigated through a few minimal models with specially chosen fluxes. These models, together with more generic 6D QH systems, can be realized in realistic 3D experimental setups like cold atom systems through possibly entangled synthetic dimensions.

Replacements for Tue, 20 Mar 18

[15]  arXiv:1801.05750 (replaced) [pdf, other]
Title: No exceptional precision of exceptional point sensors
Authors: W. Langbein
Subjects: Applied Physics (physics.app-ph)
[ total of 15 entries: 1-15 ]
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