Showing 1–31 of 31 results for author: Weber, B

Orbitally resolved single-photon emission from an individual atomic vacancy center in a semiconductor

Authors: Gagandeep Singh, Xiaodan Lyu, Bi Qi Chong, Ryan Li Yen Tang, Rejaul SK, Yande Que, Ranjith Shivajirao, Thasneem Aliyar, Radha Krishnan, Junxiang Jia, Michael S. Fuhrer, Teck Seng Koh, Weibo Gao, Bent Weber

Abstract: Atomically confined spins are emerging as active components in quantum optoelectronic devices such as quantum bits and sensors. However, interrogating single spins at atomic length-scales remains a sizeable challenge, limited by diffraction in conventional optics. Here we show that the highly-local excitation provided by injecting energetic charge carriers from the atomically sharp probe of a scan… ▽ More Atomically confined spins are emerging as active components in quantum optoelectronic devices such as quantum bits and sensors. However, interrogating single spins at atomic length-scales remains a sizeable challenge, limited by diffraction in conventional optics. Here we show that the highly-local excitation provided by injecting energetic charge carriers from the atomically sharp probe of a scanning tunneling microscope can trigger single-photon emission from individual atomic vacancy centers in a layered semiconductor. With an effective spatial resolution of <1 nm, we show that the captured light closely mirrors the orbital symmetry of the bound-state wavefunction of the vacancy center while photon correlation measurements confirm single-photon emission, as reflected in clear photon anti-bunching signatures. Our results constitute an important step toward the realization of an electrically addressable single-atom quantum light source and solid-state spinphoton interface, addressed at the atomic-scale. △ Less

Submitted 27 February, 2026; originally announced February 2026.

Computing the Full Earth System at 1 km Resolution

Authors: Daniel Klocke, Claudia Frauen, Jan Frederik Engels, Dmitry Alexeev, René Redler, Reiner Schnur, Helmuth Haak, Luis Kornblueh, Nils Brüggemann, Fatemeh Chegini, Manoel Römmer, Lars Hoffmann, Sabine Griessbach, Mathis Bode, Jonathan Coles, Miguel Gila, William Sawyer, Alexandru Calotoiu, Yakup Budanaz, Pratyai Mazumder, Marcin Copik, Benjamin Weber, Andreas Herten, Hendryk Bockelmann, Torsten Hoefler , et al. (2 additional authors not shown)

Abstract: We present the first-ever global simulation of the full Earth system at 1.25 km grid spacing, achieving highest time compression with an unseen number of degrees of freedom. Our model captures the flow of energy, water, and carbon through key components of the Earth system: atmosphere, ocean, and land. To achieve this landmark simulation, we harness the power of 8192 GPUs on Alps and 20480 GPUs on… ▽ More We present the first-ever global simulation of the full Earth system at 1.25 km grid spacing, achieving highest time compression with an unseen number of degrees of freedom. Our model captures the flow of energy, water, and carbon through key components of the Earth system: atmosphere, ocean, and land. To achieve this landmark simulation, we harness the power of 8192 GPUs on Alps and 20480 GPUs on JUPITER, two of the world's largest GH200 superchip installations. We use both the Grace CPUs and Hopper GPUs by carefully balancing Earth's components in a heterogeneous setup and optimizing acceleration techniques available in ICON's codebase. We show how separation of concerns can reduce the code complexity by half while increasing performance and portability. Our achieved time compression of 145.7 simulated days per day enables long studies including full interactions in the Earth system and even outperforms earlier atmosphere-only simulations at a similar resolution. △ Less

Submitted 7 November, 2025; v1 submitted 3 November, 2025; originally announced November 2025.

On the experimental properties of the TS defect in 4H-SiC

Authors: Johannes A. F. Lehmeyer, Alexander D. Fuchs, Zhengming Li, Titus Bornträger, Fabio Candolfi, Maximilian Schober, Marcus Fischer, Martin Hartmann, Elke Neu, Michel Bockstedte, Michael Krieger, Heiko B. Weber

Abstract: When annealing a 4H silicon carbide (SiC) crystal, a sequence of optically active defect centers occurs among which the TS center is a prominent example. Here, we present low-temperature photoluminescence analyses on the single defect level. They reveal that the three occurring spectral signatures TS1, TS2 and TS3 originate from one single defect. Their polarization dependences expose three differ… ▽ More When annealing a 4H silicon carbide (SiC) crystal, a sequence of optically active defect centers occurs among which the TS center is a prominent example. Here, we present low-temperature photoluminescence analyses on the single defect level. They reveal that the three occurring spectral signatures TS1, TS2 and TS3 originate from one single defect. Their polarization dependences expose three different crystallographic orientations in the basal plane, which relate to the projections of the nearest neighbor directions. Accordingly, we find a three-fold level-splitting in ensemble studies, when applying mechanical strain. This dependency is quantitatively calibrated. A complementary electrical measurement, deep level transient spectroscopy, reveals a charge transition level of the TS defect at 0.6 eV above the valence band. For a future identification, this accurate characterization of its optical and electronic properties along with their response to mechanical strain is a milestone. △ Less

Submitted 15 April, 2024; originally announced April 2024.

Comments: 8 pages + supporting information

NOMAD CAMELS: Configurable Application for Measurements, Experiments and Laboratory Systems

Authors: Alexander D. Fuchs, Johannes A. F. Lehmeyer, Heinz Junkes, Heiko B. Weber, Michael Krieger

Abstract: NOMAD CAMELS (short: CAMELS) is a configurable, open-source measurement software that records fully self-describing experimental data. It has its origins in the field of experimental physics where a wide variety of measurement instruments are used in frequently changing experimental setups and measurement protocols. CAMELS provides a graphical user interface (GUI) which allows the user to configur… ▽ More NOMAD CAMELS (short: CAMELS) is a configurable, open-source measurement software that records fully self-describing experimental data. It has its origins in the field of experimental physics where a wide variety of measurement instruments are used in frequently changing experimental setups and measurement protocols. CAMELS provides a graphical user interface (GUI) which allows the user to configure experiments without the need of programming skills or deep understanding of instrument communication. CAMELS translates user-defined measurement protocols into stand-alone executable Python code for full transparency of the actual measurement sequences. Existing large-scale, distributed control systems using e.g. EPICS can be natively implemented. CAMELS is designed with focus on full recording of data and metadata. When shared with others, data produced with CAMELS allow full understanding of the measurement and the resulting data in accordance with the FAIR (Findable, Accessible, Interoperable and Re-usable) principles. △ Less

Submitted 12 February, 2024; originally announced February 2024.

Journal ref: Journal of Open Source Software, 9(95), 6371 (2024)

Electrochemical etching strategy for shaping monolithic 3D structures from 4H-SiC wafers

Authors: André Hochreiter, Fabian Groß, Morris-Niklas Möller, Michael Krieger, Heiko B. Weber

Abstract: Silicon Carbide (SiC) is an outstanding material, not only for electronic applications, but also for projected functionalities in the realm of photonic quantum technologies, nano-mechanical resonators and photonics on-a-chip. For shaping 3D structures out of SiC wafers, predominantly dry-etching techniques are used. SiC is nearly inert with respect to wet-etching, occasionally photoelectrochemical… ▽ More Silicon Carbide (SiC) is an outstanding material, not only for electronic applications, but also for projected functionalities in the realm of photonic quantum technologies, nano-mechanical resonators and photonics on-a-chip. For shaping 3D structures out of SiC wafers, predominantly dry-etching techniques are used. SiC is nearly inert with respect to wet-etching, occasionally photoelectrochemical etching strategies have been applied. Here, we propose an electrochemical etching strategy that solely relies on defining etchable volumina by implantation of p-dopands. Together with the inertness of the n-doped regions, very sharp etching contrasts can be achieved. We present devices as different as monolithic cantilevers, disk-shaped optical resonators and membranes etched out of a single crystal wafer. The high quality of the resulting surfaces can even be enhanced by thermal treatment, with shape-stable devices up to and even beyond 1550°C. The versatility of our approach paves the way for new functionalities on SiC as high-performance multi-functional wafer platform. △ Less

Submitted 21 June, 2023; originally announced June 2023.

Comments: 13 pages

Journal ref: Scientific Reports 13, 19086 (2023)

Datenkompetenz im Physikstudium -- ein Erfahrungsbericht

Authors: Michael Krieger, Heiko B. Weber, Christopher van Eldik

Abstract: Do our physics curricula provide the appropriate data management competences in a world where data are considered a crucial resource and substantial funding is available for building a national research data infrastructure (German: Nationale Forschungsdateninfrastuktur = NFDI)? Although basic data evaluation and systematic documentation are practiced when students first come into contact with data… ▽ More Do our physics curricula provide the appropriate data management competences in a world where data are considered a crucial resource and substantial funding is available for building a national research data infrastructure (German: Nationale Forschungsdateninfrastuktur = NFDI)? Although basic data evaluation and systematic documentation are practiced when students first come into contact with data, particularly in experimental physics lab courses, they do not meet the increasing demands of research and professional practice to deal with the analysis of huge datasets. In many cases, the problem starts with the fact that there is no consensus on a suitable entry-level programming language. At the Department of Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg, we have made minor adjustments to the physics curriculum in recent years, which we present in this article. We placed data management competences early in the bachelor curriculum, which has resulted in considerable advantages throughout the further course of studies. The authors feel that students are quickly moving into the fast lane in data management; we can already see in our research groups that they are becoming a driving force towards modern research data management. -- Vermitteln unsere Physikcurricula die passenden Datenverarbeitungskompetenzen in einer Welt, in der Daten als entscheidende Ressource betrachtet werden und erhebliche Fördermittel für eine Nationale Forschungsdateninfrastruktur (NFDI) bereitstehen? Beim Erstkontakt mit Daten, also insbesondere in den Praktika der Experimentalphysik, werden zwar elementare Datenevaluation und systematische Dokumentation eingeübt, diese genügen aber nicht den steigenden Ansprüchen der Forschung und der Berufspraxis, sich zunehmend mit der Analyse großer Datenmengen zu befassen. Es scheitert oft schon an einem Konsens über eine geeignete Einstiegsprogrammiersprache. Am Department Physik der Friedrich-Alexander-Universität Erlangen-Nürnberg haben wir in den letzten Jahren kleinere Anpassungen im Physikcurriculum vorgenommen, die wir in diesem Artikel vorstellen. Datenkompetenz wurde früh im Bachelorstudium platziert, woraus sich erhebliche Vorteile für den weiteren Studienverlauf ergeben haben. Die Autoren können sich des Eindrucks nicht erwehren, dass die Studierenden in puncto Datenkompetenz schnell auf die Überholspur gehen; wir sehen bereits jetzt in unseren Arbeitsgruppen, dass sie sich als treibende Kräfte hin zu einem modernen Forschungsdatenmanagement erweisen. △ Less

Submitted 22 December, 2022; originally announced January 2023.

Comments: 10 pages, 3 figures, in German

Journal ref: Physik Journal 21 (2022) Nr. 12, S. 42

Light-field control of real and virtual charge carriers

Authors: Tobias Boolakee, Christian Heide, Antonio Garzón-Ramírez, Heiko B. Weber, Ignacio Franco, Peter Hommelhoff

Abstract: Light-driven electronic excitation is a cornerstone for energy and information transfer. In the interaction of intense and ultrafast light fields with solids, electrons may be excited irreversibly, or transiently during illumination only. As the transient electron population cannot be observed after the light pulse is gone it is referred to as virtual, while the population remaining excited is cal… ▽ More Light-driven electronic excitation is a cornerstone for energy and information transfer. In the interaction of intense and ultrafast light fields with solids, electrons may be excited irreversibly, or transiently during illumination only. As the transient electron population cannot be observed after the light pulse is gone it is referred to as virtual, while the population remaining excited is called real. Virtual charge carriers have recently been associated with high-harmonic generation and transient absorption, while photocurrent generation may stem from real as well as virtual charge carriers. Yet, a link between the carrier types in their generation and importance for observables up to technological relevance is missing. Here we show that real and virtual carriers can be excited and disentangled in the optical generation of currents in a gold-graphene-gold heterostructure using few-cycle laser pulses. Depending on the waveform used for photoexcitation, real carriers receive net momentum and propagate to the gold electrodes, while virtual carriers generate a polarization response read out at the gold-graphene interfaces. Based on these insights, we further demonstrate a proof of concept of a logic gate for future lightwave electronics. Our results offer a direct means to monitor and excite real and virtual charge carriers. Individual control over each type will dramatically increase the integrated circuit design space and bring closer to reality petahertz signal processing. △ Less

Submitted 8 March, 2022; v1 submitted 7 March, 2022; originally announced March 2022.

Journal ref: Nature 605, 251-255 (2022)

Electronic coherence and coherent dephasing in the optical control of electrons in graphene

Authors: Christian Heide, Timo Eckstein, Tobias Boolakee, Constanze Gerner, Heiko B. Weber, Ignacio Franco, Peter Hommelhoff

Abstract: Electronic coherence is of utmost importance for the access and control of quantum-mechanical solid-state properties. Using a purely electronic observable, the photocurrent, we measure an electronic coherence time of 22 +/- 4 fs in graphene. The photocurrent is ideally suited to measure electronic coherence as it is a direct result of quantum path interference, controlled by the delay between two… ▽ More Electronic coherence is of utmost importance for the access and control of quantum-mechanical solid-state properties. Using a purely electronic observable, the photocurrent, we measure an electronic coherence time of 22 +/- 4 fs in graphene. The photocurrent is ideally suited to measure electronic coherence as it is a direct result of quantum path interference, controlled by the delay between two ultrashort two-color laser pulses. The maximum delay for which interference between the population amplitude injected by the first pulse interferes with that generated by the second pulse determines the electronic coherence time. In particular, numerical simulations reveal that the experimental data yield a lower boundary on the electronic coherence time and that coherent dephasing masks a lower coherence time. We expect that our results will significantly advance the understanding of coherent quantum-control in solid-state systems ranging from excitation with weak fields to strongly driven systems. △ Less

Submitted 14 July, 2021; originally announced July 2021.

Narrow inhomogeneous distribution of spin-active emitters in silicon carbide

Authors: Roland Nagy, Durga Bhaktavatsala Rao Dasari, Charles Babin, Di Liu, Vadim Vorobyov, Matthias Niethammer, Matthias Widmann, Tobias Linkewitz, Rainer Stöhr, Heiko B. Weber, Takeshi Ohshima, Misagh Ghezellou, Nguyen Tien Son, Jawad Ul-Hassan, Florian Kaiser, Jörg Wrachtrup

Abstract: Optically active solid-state spin registers have demonstrated their unique potential in quantum computing, communication and sensing. Realizing scalability and increasing application complexity requires entangling multiple individual systems, e.g. via photon interference in an optical network. However, most solid-state emitters show relatively broad spectral distributions, which hinders optical in… ▽ More Optically active solid-state spin registers have demonstrated their unique potential in quantum computing, communication and sensing. Realizing scalability and increasing application complexity requires entangling multiple individual systems, e.g. via photon interference in an optical network. However, most solid-state emitters show relatively broad spectral distributions, which hinders optical interference experiments. Here, we demonstrate that silicon vacancy centres in semiconductor silicon carbide (SiC) provide a remarkably small natural distribution of their optical absorption/emission lines despite an elevated defect concentration of $\approx 0.43\,\rm μm^{-3}$. In particular, without any external tuning mechanism, we show that only 13 defects have to be investigated until at least two optical lines overlap within the lifetime-limited linewidth. Moreover, we identify emitters with overlapping emission profiles within diffraction limited excitation spots, for which we introduce simplified schemes for generation of computationally-relevant Greenberger-Horne-Zeilinger (GHZ) and cluster states. Our results underline the potential of the CMOS-compatible SiC platform toward realizing networked quantum technology applications. △ Less

Submitted 12 March, 2021; v1 submitted 10 March, 2021; originally announced March 2021.

Comments: 7 pages, 4 figures

Journal ref: Applied Physics Letters 118, 144003 (2021)

Attosecond-fast internal photoemission

Authors: Christian Heide, Martin Hauck, Takuya Higuchi, Jürgen Ristein, Lothar Ley, Heiko B. Weber, Peter Hommelhoff

Abstract: The photoelectric effect has a sister process relevant in optoelectronics called internal photoemission. Here an electron is photoemitted from a metal into a semiconductor. While the photoelectric effect takes place within less than 100 attoseconds, the attosecond time scale has so far not been measured for internal photoemission. Based on the new method CHArge transfer time MEasurement via Laser… ▽ More The photoelectric effect has a sister process relevant in optoelectronics called internal photoemission. Here an electron is photoemitted from a metal into a semiconductor. While the photoelectric effect takes place within less than 100 attoseconds, the attosecond time scale has so far not been measured for internal photoemission. Based on the new method CHArge transfer time MEasurement via Laser pulse duration-dependent saturation fluEnce determinatiON, CHAMELEON, we show that the atomically thin semi-metal graphene coupled to bulk silicon carbide, forming a Schottky junction, allows charge transfer times as fast as (300 $\pm$ 200) attoseconds. These results are supported by a simple quantum mechanical model simulation. With the obtained cut-off bandwidth of 3.3 PHz for the charge transfer rate, this semimetal-semiconductor interface represents the first functional solid-state interface offering the speed and design space required for future light-wave signal processing. △ Less

Submitted 9 January, 2020; originally announced January 2020.

Interaction of carrier envelope phase-stable laser pulses with graphene: the transition from the weak-field to the strong-field regime

Authors: Christian Heide, Tobias Boolakee, Takuya Higuchi, Heiko B. Weber, Peter Hommelhoff

Abstract: Ultrafast control of electron dynamics in solid state systems has recently found particular attention. By increasing the electric field strength of laser pulses, the light-matter interaction in solids might turn from a perturbative into a novel non-perturbative regime, where interband transitions from the valence to the conduction band become strongly affected by intraband motion. We have demonstr… ▽ More Ultrafast control of electron dynamics in solid state systems has recently found particular attention. By increasing the electric field strength of laser pulses, the light-matter interaction in solids might turn from a perturbative into a novel non-perturbative regime, where interband transitions from the valence to the conduction band become strongly affected by intraband motion. We have demonstrated experimentally and numerically that this combined dynamics can be controlled in graphene with the electric field waveform of phase-stabilized few-cycle laser pulses. Here we show new experimental data and matching simulation results at comparably low optical fields, which allows us to focus on the highly interesting transition regime where the light-matter interaction turns from perturbative to non-perturbative. We find a 5th order power-law scaling of the laser induced waveform-dependent current at low optical fields, which breaks down for higher optical fields, indicating the transition. △ Less

Submitted 18 March, 2019; originally announced March 2019.

Comments: 12 pages, 3 figures. New J. Phys 2019

Coherent electron trajectory control in graphene

Authors: Christian Heide, Takuya Higuchi, Heiko B. Weber, Peter Hommelhoff

Abstract: We investigate coherent electron dynamics in graphene, interacting with the electric field waveform of two orthogonally polarized, few-cycle laser pulses. Recently, we demonstrated that linearly polarized driving pulses lead to sub-optical-cycle Landau-Zener quantum path interference by virtue of the combination of intraband motion and interband transition [Higuchi $\textit{et al.}$, Nature… ▽ More We investigate coherent electron dynamics in graphene, interacting with the electric field waveform of two orthogonally polarized, few-cycle laser pulses. Recently, we demonstrated that linearly polarized driving pulses lead to sub-optical-cycle Landau-Zener quantum path interference by virtue of the combination of intraband motion and interband transition [Higuchi $\textit{et al.}$, Nature $\textbf{550}$, 224 (2017)]. Here we introduce a pulsed control laser beam, orthogonally polarized to the driving pulses, and observe the ensuing electron dynamics. The relative delay between the two pulses is a tuning parameter to control the electron trajectory, now in a complex fashion exploring the full two-dimensional reciprocal space in graphene. Depending on the relative phase, the electron trajectory in the reciprocal space can, for example, be deformed to suppress the quantum path interference resulting from the driving laser pulse. Intriguingly, this strong-field-based complex matter wave manipulation in a two-dimensional conductor is driven by a high repetition rate \textit{laser oscillator}, rendering unnecessary complex and expensive amplified laser systems. △ Less

Submitted 15 November, 2018; originally announced November 2018.

Journal ref: Christian Heide, Takuya Higuchi, Heiko B. Weber, Peter Hommelhoff; Phys. Rev. Lett. 121, 207401 (2018)

Supercooled fog as a natural laboratory for studying ice formation in clouds

Authors: Lea B. Weber, Franz Conen

Abstract: The ice phase in clouds contributes largely to uncertainties in global climate models partly due to a lack of atmospheric observations. At moderate supercooling ice nucleating particles (INP) and ice particles (IP) are present in small concentrations and a large volume of air is necessary for observation. Here, we report on initial observations of IP in supercooled fog with a new setup. We use a 0… ▽ More The ice phase in clouds contributes largely to uncertainties in global climate models partly due to a lack of atmospheric observations. At moderate supercooling ice nucleating particles (INP) and ice particles (IP) are present in small concentrations and a large volume of air is necessary for observation. Here, we report on initial observations of IP in supercooled fog with a new setup. We use a 0.3 m wide, vertical curtain of light and a camera pointing perpendicularly at it to record light scattered by IP formed in radiation fog near the ground at temperatures between -3 °C and -9 °C. Deposition rates of IP were several times larger than expected from number concentrations of INP found on $PM_{10}$-filters at a nearby air quality monitoring station. The discrepancy might be explained by secondary ice formation through the fragmentation of freezing water droplets, the entrainment of INP from above the fog layer through settling, the loss or deactivation of INP on $PM_{10}$-filters prior to analysis, or radiative cooling of INP below the temperature of the surrounding air. In summary, radiation fog constitutes an easily accessible form of a supercooled cloud, in which observations can be made for long enough to quantify the deposition rate of rare IP produced in a natural environment. △ Less

Submitted 10 November, 2018; originally announced November 2018.

Comments: 13 pages, 3 figures

Self-assembly of magnetic iron oxide nanoparticles into cuboidal superstructures

Authors: Sabine Rosenfeldt, Stephan Förster, Thomas Friedrich, Ingo Rehberg, Birgit Weber

Abstract: This chapter describes the synthesis and some characteristics of magnetic iron oxide nanoparticles, mainly nanocubes, and focus on their self-assembly into crystalline cuboids in dispersion. The influence of external magnetic fields, the concentration of particles, and the temperature on the assembly process is experimentally investigated. This chapter describes the synthesis and some characteristics of magnetic iron oxide nanoparticles, mainly nanocubes, and focus on their self-assembly into crystalline cuboids in dispersion. The influence of external magnetic fields, the concentration of particles, and the temperature on the assembly process is experimentally investigated. △ Less

Submitted 21 March, 2018; originally announced March 2018.

Journal ref: Domracheva, Natalia ; Caporali, Maria ; Rentschler, Eva (Hrsg.): Novel Magnetic Nanostructures. - Amsterdam : Elsevier , 2018 . - S. 165-189 . - (Micro & Nano Technologies Series ) ISBN 978-0-12-813594-5

On the uncertainty of temperature estimation in a rapid compression machine

Authors: Bryan W. Weber, Chih-Jen Sung, Michael W. Renfro

Abstract: Rapid compression machines (RCMs) have been widely used in the combustion literature to study the low-to-intermediate temperature ignition of many fuels. In a typical RCM, the pressure during and after the compression stroke is measured. However, measurement of the temperature history in the RCM reaction chamber is challenging. Thus, the temperature is generally calculated by the isentropic relati… ▽ More Rapid compression machines (RCMs) have been widely used in the combustion literature to study the low-to-intermediate temperature ignition of many fuels. In a typical RCM, the pressure during and after the compression stroke is measured. However, measurement of the temperature history in the RCM reaction chamber is challenging. Thus, the temperature is generally calculated by the isentropic relations between pressure and temperature, assuming that the adiabatic core hypothesis holds. To estimate the uncertainty in the calculated temperature, an uncertainty propagation analysis must be carried out. Our previous analyses assumed that the uncertainties of the parameters in the equation to calculate the temperature were normally distributed and independent, but these assumptions do not hold for typical RCM operating procedures. In this work, a Monte Carlo method is developed to estimate the uncertainty in the calculated temperature, while taking into account the correlation between parameters and the possibility of non-normal probability distributions. In addition, the Monte Carlo method is compared to an analysis that assumes normally distributed, independent parameters. Both analysis methods show that the magnitude of the initial pressure and the uncertainty of the initial temperature have strong influences on the magnitude of the uncertainty. Finally, the uncertainty estimation methods studied here provide a reference value for the uncertainty of the reference temperature in an RCM and can be generalized to other similar facilities. △ Less

Submitted 9 June, 2017; originally announced June 2017.

Comments: 25 pages, 4 figures, 8 tables

Journal ref: Combustion and Flame, vol. 162, no. 6 (June 2015): 2518-2528

Autoigniton of n-Butanol at Low to Intermediate Temperature and Elevated Pressure

Authors: Bryan W. Weber

Abstract: Autoignition delay experiments were performed for n-butanol in a heated rapid compression machine. Experiments were performed at pressures of 15 and 30 bar, in the temperature range 650-900 K, and for equivalence ratios of 0.5, 1.0, and 2.0. Additionally, the initial fuel mole fraction and initial oxygen mole fraction were varied independently to determine the influence of each on ignition delay.… ▽ More Autoignition delay experiments were performed for n-butanol in a heated rapid compression machine. Experiments were performed at pressures of 15 and 30 bar, in the temperature range 650-900 K, and for equivalence ratios of 0.5, 1.0, and 2.0. Additionally, the initial fuel mole fraction and initial oxygen mole fraction were varied independently to determine the influence of each on ignition delay. Over the conditions studied, it was found that the reactivity of the mixture increased as equivalence ratio, initial fuel mole fraction or initial oxygen mole fraction increased. A non-linear correlation to the experimental data was performed and showed nearly second order dependence on the initial oxygen mole fraction and nearly first order dependence on initial fuel mole fraction and compressed pressure. This was the first study of the ignition of n-butanol in this temperature and pressure range, and contributes to a better understanding of the chemistry of this fuel under the conditions relevant to practical devices. Experimentally measured ignition delays were compared against the ignition delay computed from several reaction mechanisms in the literature. The agreement between experiments and simulations was found to be unsatisfactory. Sensitivity analysis was performed and indicated that the uncertainties of the rate constants of parent fuel decomposition reactions play a major role in causing the poor agreement. Further path analysis of the fuel decomposition reactions supported this conclusion and highlighted the particular importance of certain pathways. Based on these results, it was concluded that further investigation of the fuel decomposition, including speciation measurements, will be required. △ Less

Submitted 9 June, 2017; originally announced June 2017.

Comments: 63 pages, 32 figures, 2 tables, MS Thesis (August 2010)

Experiments and Modeling of the Autoignition of Methylcyclohexane at High Pressure

Authors: Bryan W. Weber, WIlliam J. Pitz, Marco Mehl, Emma Silke, Alexander C. Davis, Chih-Jen Sung

Abstract: New experimental data are collected for methyl-cyclohexane (MCH) autoignition in a heated rapid compression machine (RCM). Three mixtures of MCH/O2/N2/Ar at equivalence ratios of $φ$=0.5, 1.0, and 1.5 are studied and the ignition delays are measured at compressed pressure of 50 bar and for compressed temperatures in the range of 690-900 K. By keeping the fuel mole fraction in the mixture constant,… ▽ More New experimental data are collected for methyl-cyclohexane (MCH) autoignition in a heated rapid compression machine (RCM). Three mixtures of MCH/O2/N2/Ar at equivalence ratios of $φ$=0.5, 1.0, and 1.5 are studied and the ignition delays are measured at compressed pressure of 50 bar and for compressed temperatures in the range of 690-900 K. By keeping the fuel mole fraction in the mixture constant, the order of reactivity, in terms of inverse ignition delay, is measured to be $φ$=0.5 > $φ$=1.0 > $φ$=1.5, demonstrating the dependence of the ignition delay on oxygen concentration. In addition, an existing model for the combustion of MCH is updated with new reaction rates and pathways, including substantial updates to the low-temperature chemistry. The new model shows good agreement with the overall ignition delays measured in this study, as well as the ignition delays measured previously in the literature using RCMs and shock tubes. This model therefore represents a strong improvement compared to the previous version, which uniformly over-predicted the ignition delays. Chemical kinetic analyses of the updated mechanism are also conducted to help understand the fuel decomposition pathways and the reactions controlling the ignition. Combined, these results and analyses suggest that further investigation of several of the low-temperature fuel decomposition pathways is required. △ Less

Submitted 9 June, 2017; originally announced June 2017.

Comments: 38 pages, 12 figures, 2 tables

Journal ref: Combustion and Flame, vol. 161, no. 8 (August 2014): 1972-1983

Comparative Autoignition Trends in the Butanol Isomers at Elevated Pressure

Authors: Bryan W. Weber, Chih-Jen Sung

Abstract: Autoignition experiments of stoichiometric mixtures of s-, t-, and i-butanol in air have been performed using a heated rapid compression machine (RCM). At compressed pressures of 15 and 30 bar and for compressed temperatures in the range of 715-910 K, no evidence of a negative temperature coefficient region in terms of ignition delay response is found. The present experimental results are also com… ▽ More Autoignition experiments of stoichiometric mixtures of s-, t-, and i-butanol in air have been performed using a heated rapid compression machine (RCM). At compressed pressures of 15 and 30 bar and for compressed temperatures in the range of 715-910 K, no evidence of a negative temperature coefficient region in terms of ignition delay response is found. The present experimental results are also compared with previously reported RCM data of n-butanol in air. The order of reactivity of the butanols is n-butanol>s-butanol$\approx$i-butanol>t-butanol at the lower pressure, but changes to n-butanol>t-butanol>s-butanol>i-butanol at higher pressure. In addition, t-butanol shows pre-ignition heat release behavior, which is especially evident at higher pressures. To help identify the controlling chemistry leading to this pre-ignition heat release, off-stoichiometric experiments are further performed at 30 bar compressed pressure, for t-butanol at $φ$ = 0.5 and $φ$ = 2.0 in air. For these experiments, higher fuel loading (i.e. $φ$ = 2.0) causes greater pre-ignition heat release (as indicated by greater pressure rise) than the stoichiometric or $φ$ = 0.5 cases. Comparison of the experimental ignition delays with the simulated results using two literature kinetic mechanisms shows generally good agreement, and one mechanism is further used to explore and compare the fuel decomposition pathways of the butanol isomers. Using this mechanism, the importance of peroxy chemistry in the autoignition of the butanol isomers is highlighted and discussed. △ Less

Submitted 9 June, 2017; originally announced June 2017.

Comments: 49 pages, 21 figures, 10 tables

Journal ref: Energy & Fuels vol. 27, no. 3 (March 2013): 1688-1698

ChemKED: a human- and machine-readable data standard for chemical kinetics experiments

Authors: Bryan W. Weber, Kyle E. Niemeyer

Abstract: Fundamental experimental measurements of quantities such as ignition delay times, laminar flame speeds, and species profiles (among others) serve important roles in understanding fuel chemistry and validating chemical kinetic models. However, despite both the importance and abundance of such information in the literature, the community lacks a widely adopted standard format for this data. This imp… ▽ More Fundamental experimental measurements of quantities such as ignition delay times, laminar flame speeds, and species profiles (among others) serve important roles in understanding fuel chemistry and validating chemical kinetic models. However, despite both the importance and abundance of such information in the literature, the community lacks a widely adopted standard format for this data. This impedes both sharing and wide use by the community. Here we introduce a new chemical kinetics experimental data format, ChemKED, and the related Python-based package for validating and working with ChemKED-formatted files called PyKED. We also review past and related efforts, and motivate the need for a new solution. ChemKED currently supports the representation of autoignition delay time measurements from shock tubes and rapid compression machines. ChemKED-formatted files contain all of the information needed to simulate experimental data points, including the uncertainty of the data. ChemKED is based on the YAML data serialization language, and is intended as a human- and machine-readable standard for easy creation and automated use. Development of ChemKED and PyKED occurs openly on GitHub under the BSD 3-clause license, and contributions from the community are welcome. Plans for future development include support for experimental data from laminar flame, jet stirred reactor, and speciation measurements. △ Less

Submitted 15 November, 2017; v1 submitted 6 June, 2017; originally announced June 2017.

Comments: 22 pages, accepted for publication in the International Journal of Chemical Kinetics

UConnRCMPy: Python-based data analysis for rapid compression machines

Authors: Bryan W. Weber, Chih-Jen Sung

Abstract: The ignition delay of a fuel/air mixture is an important quantity in designing combustion devices, and these data are also used to validate chemical kinetic models for combustion. One of the typical experimental devices used to measure the ignition delay is called a Rapid Compression Machine (RCM). This paper presents UConnRCMPy, an open-source Python package to process experimental data from the… ▽ More The ignition delay of a fuel/air mixture is an important quantity in designing combustion devices, and these data are also used to validate chemical kinetic models for combustion. One of the typical experimental devices used to measure the ignition delay is called a Rapid Compression Machine (RCM). This paper presents UConnRCMPy, an open-source Python package to process experimental data from the RCM at the University of Connecticut. Given an experimental measurement, UConnRCMPy computes the thermodynamic conditions in the reaction chamber of the RCM during an experiment along with the ignition delay. UConnRCMPy implements an extensible framework, so that alternative experimental data formats can be incorporated easily. In this way, UConnRCMPy improves the consistency of RCM data processing and enables the community to reproduce data analysis procedures. △ Less

Submitted 6 June, 2017; originally announced June 2017.

Comments: 8 pages, 3 figures, presented at the 10th US National Combustion Meeting

Comparative Investigation of the High Pressure Autoignition of the Butanol Isomers

Authors: Bryan W. Weber, Chih-Jen Sung

Abstract: Investigation of the autoignition delay of the butanol isomers has been performed at elevated pressures of 15 bar and 30 bar and low to intermediate temperatures of 680-860 K. The reactivity of the stoichiometric isomers of butanol, in terms of inverse ignition delay, was ranked as n-butanol > sec-butanol ~ iso-butanol > tert-butanol at a compressed pressure of 15 bar but changed to n-butanol > te… ▽ More Investigation of the autoignition delay of the butanol isomers has been performed at elevated pressures of 15 bar and 30 bar and low to intermediate temperatures of 680-860 K. The reactivity of the stoichiometric isomers of butanol, in terms of inverse ignition delay, was ranked as n-butanol > sec-butanol ~ iso-butanol > tert-butanol at a compressed pressure of 15 bar but changed to n-butanol > tert-butanol > sec-butanol > iso-butanol at 30 bar. For the temperature and pressure conditions in this study, no NTC or two-stage ignition behavior were observed. However, for both of the compressed pressures studied in this work, tert-butanol exhibited unique pre-ignition heat release characteristics. As such, tert-butanol was further studied at two additional equivalence ratios ($φ$ = 0.5 and 2.0) to help determine the cause of the heat release. △ Less

Submitted 6 June, 2017; originally announced June 2017.

Comments: 4 pages, 4 figures, presented at the 2011 Meeting of the Eastern States Sections of the Combustion Institute

Autoignition of Butanol Isomers at Low to Intermediate Temperature and Elevated Pressure

Authors: Bryan W. Weber, Kamal Kumar, Chih-Jen Sung

Abstract: Autoignition delay experiments for the isomers of butanol, including n-, sec-, tert-, and iso-butanol, have been performed using a heated rapid compression machine. For a compressed pressure of 15 bar, the compressed temperatures have been varied in the range of 725-855 K for all the stoichiometric fuel/oxidizer mixtures. Over the conditions investigated in this study, the ignition delay decreases… ▽ More Autoignition delay experiments for the isomers of butanol, including n-, sec-, tert-, and iso-butanol, have been performed using a heated rapid compression machine. For a compressed pressure of 15 bar, the compressed temperatures have been varied in the range of 725-855 K for all the stoichiometric fuel/oxidizer mixtures. Over the conditions investigated in this study, the ignition delay decreases monotonically as temperature increases and exhibits single-stage characteristics. Experimental ignition delays are also compared to simulations computed using three kinetic mechanisms available in the literature. Reasonable agreement is found for three isomers (tert-, iso-, and n-butanol). △ Less

Submitted 6 June, 2017; originally announced June 2017.

Comments: 8 pages, 5 figures, presented at the 49th AIAA Aerospace Sciences meeting

A Rapid Compression Study of the Butanol Isomers at Elevated Pressure

Authors: Bryan W. Weber, Chih-Jen Sung

Abstract: Investigation of the autoignition delay of the butanol isomers has been performed at elevated pressure of 15 bar and low to intermediate temperatures of 725-870 K. Stoichiometric mixtures made in nitrogen/oxygen air were studied. For the temperature and pressure conditions in this study, no NTC or two-stage ignition behavior were observed. The reactivity of the isomers of butanol, in terms of inve… ▽ More Investigation of the autoignition delay of the butanol isomers has been performed at elevated pressure of 15 bar and low to intermediate temperatures of 725-870 K. Stoichiometric mixtures made in nitrogen/oxygen air were studied. For the temperature and pressure conditions in this study, no NTC or two-stage ignition behavior were observed. The reactivity of the isomers of butanol, in terms of inverse ignition delay, was ranked as n-butanol > sec-butanol ~ iso-butanol > tert-butanol. Predictions of the ignition delay by several kinetic mechanisms available in the literature generally over-predict the ignition delays. △ Less

Submitted 6 June, 2017; originally announced June 2017.

Comments: 6 pages, 4 figures, presented at the 7th US National Combustion Meeting

Experiments and Modeling of the Autoignition of Methyl-Cyclohexane at High Pressure

Authors: Bryan W. Weber, William J. Pitz, Chih-Jen Sung, Marco Mehl, Emma J. Silke, Alexander C. Davis

Abstract: The autoignition delays of mixtures of methyl-cyclohexane (MCH), oxygen, nitrogen, and argon have been studied in a heated rapid compression machine under the conditions $P_C$ = 50 bar, $T_C$ = 690 - 910K. Three different mixture compositions were studied, with equivalence ratios ranging from $φ$ = 0.5 - 1.5. The trends of the ignition delay measured at 50 bar were similar to the trends measured i… ▽ More The autoignition delays of mixtures of methyl-cyclohexane (MCH), oxygen, nitrogen, and argon have been studied in a heated rapid compression machine under the conditions $P_C$ = 50 bar, $T_C$ = 690 - 910K. Three different mixture compositions were studied, with equivalence ratios ranging from $φ$ = 0.5 - 1.5. The trends of the ignition delay measured at 50 bar were similar to the trends measured in earlier experiments at $P_C$ = 15.1 and 25.5 bar. The experimentally measured ignition delays were compared to a newly updated chemical kinetic model for the combustion of MCH. The model has been updated to include newly calculated reaction rates for much of the low-temperature chemistry. The agreement between the experiments and the model was substantially improved compared to a previous version of the model. Nevertheless, despite the encouraging improvements, work continues on further advances, e.g. in improving predictions of the first stage ignition delays. △ Less

Submitted 6 June, 2017; originally announced June 2017.

Comments: 8 pages, 8 figures, 1 table, presented at the 8th US National Combustion Meeting

An Autoignition Study of iso-Butanol: Experiments and Modeling

Authors: Bryan W. Weber, Shamel Merchant, Chih-Jen Sung, William H. Green

Abstract: The autoignition delays of iso-butanol, oxygen, and nitrogen mixtures have been measured in a heated rapid compression machine (RCM). At compressed pressures of 15 and 30 bar, over the temperature range 800-950 K, and for equivalence ratio of $φ$ = 0.5 in air, no evidence of an NTC region of overall ignition delay is found. By comparing the data from this study taken at $φ$ = 0.5 to previous data… ▽ More The autoignition delays of iso-butanol, oxygen, and nitrogen mixtures have been measured in a heated rapid compression machine (RCM). At compressed pressures of 15 and 30 bar, over the temperature range 800-950 K, and for equivalence ratio of $φ$ = 0.5 in air, no evidence of an NTC region of overall ignition delay is found. By comparing the data from this study taken at $φ$ = 0.5 to previous data collected at $φ$ = 1.0 (Weber et al. 2013), it was found that the $φ$ = 0.5 mixture was less reactive (as measured by the inverse of the ignition delay) than the $φ$ = 1.0 mixture for the same compressed pressure. Furthermore, a recent chemical kinetic model of iso-butanol combustion was updated using the automated software Reaction Mechanism Generator (RMG) to include low- temperature chain branching pathways. Comparison of the ignition delays with the updated model showed reasonable agreement for most of the experimental conditions. Nevertheless, further work is needed to fully understand the low temperature pathways that control iso-butanol autoignition in the RCM. △ Less

Submitted 6 June, 2017; originally announced June 2017.

Comments: 6 pages, 4 figures, 8th US National Combustion Meeting

High-Pressure Autoignition of Binary Blends of Methanol and Dimethyl Ether

Authors: Hongfu Wang, Bryan W. Weber, Ruozhou Fang, Chih-Jen Sung

Abstract: Reactivity Controlled Compression Ignition (RCCI) is a new advanced engine concept that uses a dual fuel mode of operation to achieve significant improvements in fuel economy and emissions output. The fuels that are typically used in this mode include a low- and a high-reactivity fuel in varying proportions to control ignition timing. As such, understanding the interaction effects during autoignit… ▽ More Reactivity Controlled Compression Ignition (RCCI) is a new advanced engine concept that uses a dual fuel mode of operation to achieve significant improvements in fuel economy and emissions output. The fuels that are typically used in this mode include a low- and a high-reactivity fuel in varying proportions to control ignition timing. As such, understanding the interaction effects during autoignition of binary fuel blends is critical to optimizing these RCCI engines. In this work, we measure the autoignition delays of binary blends of dimethyl ether (C$_2$H$_6$O, DME) and methanol (CH$_4$O, MeOH) in a rapid compression machine. In these experiments, dimethyl ether and methanol function as the high- and low-reactivity fuels, respectively. We considered five fuel blends at varying blending ratios (by mole), including 100% DME-0% MeOH, 75% DME-25% MeOH, 0% DME-0% MeOH, 25% DME-75% MeOH, and 0% DME-100% MeOH. Experiments are conducted at an engine-relevant pressure of 30 bar, for the stoichiometric equivalence ratio. In addition, the experimental results are compared with simulations using a chemical kinetic model for DME/MeOH combustion generated by merging independent, well-validated models for DME and MeOH. △ Less

Submitted 5 June, 2017; originally announced June 2017.

Comments: 7 pages, 3 figures, 1 table, presented at the 10th US National Combustion Meeting

Autoignition of Methyl Valerate at Low to Intermediate Temperatures and Elevated Pressures in a Rapid Compression Machine

Authors: Bryan W. Weber, Justin Bunnell, Kamal Kumar, Chih-Jen Sung

Abstract: Methyl valerate (C$_6$H$_{12}$O$_2$, methyl pentanoate) is a methyl ester and a relevant surrogate component for biodiesel. In this work, we present ignition delays of methyl valerate measured using a rapid compression machine at a range of engine-relevant temperature, pressure, and equivalence ratio conditions. The conditions we have studied include equivalence ratios from 0.25 to 2.0, temperatur… ▽ More Methyl valerate (C$_6$H$_{12}$O$_2$, methyl pentanoate) is a methyl ester and a relevant surrogate component for biodiesel. In this work, we present ignition delays of methyl valerate measured using a rapid compression machine at a range of engine-relevant temperature, pressure, and equivalence ratio conditions. The conditions we have studied include equivalence ratios from 0.25 to 2.0, temperatures between 680 K and 1050 K, and pressures of 15 bar and 30 bar. The ignition delay data demonstrate a negative temperature coefficient region in the temperature range of 720 K-800 K for both $φ$=2.0, 15 bar and $φ$=1.0, 30 bar, with two-stage ignition apparent over the narrower temperature ranges of 720 K-760 K for the lower pressure and 740 K-800 K at the higher pressure. In addition, the experimental ignition delay data are compared with simulations using an existing chemical kinetic model from the literature. The simulations with the literature model under-predict the data by factors between 2 and 10 over the entire range of the experimental data. To help determine the possible reasons for the discrepancy between simulations and experiments, a new chemical kinetic model is developed using the Reaction Mechanism Generator (RMG) software. The agreement between the experimental data and the RMG model is improved but still not satisfactory. Directions for future improvement of the methyl valerate model are discussed. △ Less

Submitted 5 June, 2017; originally announced June 2017.

Comments: 9 pages, 6 figures, 2 tables, presented at the 10th US National Combustion Meeting

Autoignition of n-Butanol at Elevated Pressure and Low to Intermediate Temperature

Authors: Bryan W. Weber, Kamal Kumar, Yu Zhang, Chih-Jen Sung

Abstract: Autoignition experiments for n-butanol have been performed using a heated rapid compression machine at compressed pressures of 15 and 30 bar, in the compressed temperature range of 675-925 K, and for equivalence ratios of 0.5, 1.0, and 2.0. Over the conditions studied, the ignition delay decreases monotonically as temperature increases, and the autoignition response exhibits single-stage character… ▽ More Autoignition experiments for n-butanol have been performed using a heated rapid compression machine at compressed pressures of 15 and 30 bar, in the compressed temperature range of 675-925 K, and for equivalence ratios of 0.5, 1.0, and 2.0. Over the conditions studied, the ignition delay decreases monotonically as temperature increases, and the autoignition response exhibits single-stage characteristics. A non-linear fit to the experimental data is performed and the reactivity, in terms of the inverse of ignition delay, shows nearly second order dependence on the initial oxygen mole fraction and slightly greater than first order dependence on initial fuel mole fraction and compressed pressure. Experimentally measured ignition delays are also compared to simulations using several reaction mechanisms available in the literature. Agreement between simulated and experimental ignition delay is found to be unsatisfactory. Sensitivity analysis is performed on one recent mechanism and indicates that uncertainties in the rate coefficients of parent fuel decomposition reactions play a major role in causing the poor agreement. Path analysis of the fuel decomposition reactions supports this conclusion and also highlights the particular importance of certain pathways. Further experimental investigations of the fuel decomposition, including speciation measurements, are required. △ Less

Submitted 2 June, 2017; originally announced June 2017.

Comments: 45 pages, 16 figures, 1 table, accepted at Combustion and Flame

Journal ref: Combust. Flame, vol. 158, no. 5, pp. 809-819, Mar. 2011

Light-field driven currents in graphene

Authors: Takuya Higuchi, Christian Heide, Konrad Ullmann, Heiko B. Weber, Peter Hommelhoff

Abstract: Ultrafast electron dynamics in solids under strong optical fields has recently found particular attention. In dielectrics and semiconductors, various light-field-driven effects have been explored, such as high-harmonic generation, sub-optical-cycle interband population transfer and nonperturbative increase of transient polarizability. In contrast, much less is known about field-driven electron dyn… ▽ More Ultrafast electron dynamics in solids under strong optical fields has recently found particular attention. In dielectrics and semiconductors, various light-field-driven effects have been explored, such as high-harmonic generation, sub-optical-cycle interband population transfer and nonperturbative increase of transient polarizability. In contrast, much less is known about field-driven electron dynamics in metals because charge carriers screen an external electric field in ordinary metals. Here we show that atomically thin monolayer Graphene offers unique opportunities to study light-field-driven processes in a metal. With a comparably modest field strength of up to 0.3 V/Å, we drive combined interband and intraband electron dynamics, leading to a light-field-waveform controlled residual conduction current after the laser pulse is gone. We identify the underlying pivotal physical mechanism as electron quantum-path interference taking place on the 1-femtosecond ($10^{-15}$ second) timescale. The process can be categorized as Landau-Zener-Stückelberg interferometry. These fully coherent electron dynamics in graphene take place on a hitherto unexplored timescale faster than electron-electron scattering (tens of femtoseconds) and electron-phonon scattering (hundreds of femtoseconds). These results broaden the scope of light-field control of electrons in solids to an entirely new and eminently important material class -- metals -- promising wide ramifications for band structure tomography and light-field-driven electronics. △ Less

Submitted 14 July, 2016; originally announced July 2016.

Comments: 12 pages, 7 figures, including supplementary information

Ultra-fast transistor-based detectors for precise timing of near infrared and THz signals

Authors: S. Preu, M. Mittendorff, S. Winnerl, H. Lu, A. C. Gossard, H. B. Weber

Abstract: A whole class of two-color experiments involves intense, short Terahertz radiation pulses. A fast detector that is sensitive and able to resolve both near-infrared and Terahertz pulses at the same time is highly desirable. Here we present the first detector of this kind. The detector element is a GaAs-based field effect transistor operated at room temperature. THz detection is successfully demonst… ▽ More A whole class of two-color experiments involves intense, short Terahertz radiation pulses. A fast detector that is sensitive and able to resolve both near-infrared and Terahertz pulses at the same time is highly desirable. Here we present the first detector of this kind. The detector element is a GaAs-based field effect transistor operated at room temperature. THz detection is successfully demonstrated at frequencies up to 4.9 THz. The THz detection time constant is shorter than 30 ps, the optical time constant is 150 ps. This detector is ideally suited for precise, simultaneous resolution of optical and THz pulses and for pulse characterization of high-power THz pulses up to tens of kW peak power levels. The dynamic range of the detector was as large as 65 $\pm$ 3 dB/$\sqrt{Hz}$, enabling applications in a large variety of experiments and setups, also including table-top systems. △ Less

Submitted 19 March, 2013; originally announced March 2013.

Comments: 8 pages, 4 figures

Journal ref: Optics Express, Vol. 21, Issue 15, pp. 17941-17950 (2013)

Noise in laser speckle correlation and imaging techniques

Authors: Sergey E. Skipetrov, Joern Peuser, Roberto Cerbino, Pavel Zakharov, Bruno Weber, Frank Scheffold

Abstract: We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent pixels… ▽ More We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent pixels as well as to the effective time averaging (due to the finite sampling time) and spatial averaging (due to the finite pixel size). Our results provide a guide to estimation of noise level in such applications as the multi-speckle dynamic light scattering, time-resolved correlation spectroscopy, speckle visibility spectroscopy, laser speckle imaging etc. △ Less

Submitted 17 May, 2010; originally announced May 2010.

Comments: submitted 14 May 2010

Journal ref: Optics Express, Vol. 18, Issue 14, pp. 14519-14534 (2010)