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Dual-color nonlinear optical microscope imaging and its applications

Dual-color nonlinear optical microscope imaging and its appl...

2011 International Quantum Electronics Conference, IQEC 2011 and Conference on Lasers and Electro-Optics, CLEO Pacific Rim 2011

作者： Lee, Jang Hyuk Choi, Dae Sik Song, Dong Hoon Cho, Eun Hee Shin, Sang-Mo Oh, Myoung-Kyu Ko, Do-Kyeong Graduate Program of Photonics and Applied Physics Gwangju Institute of Science and Technology Gwangju 500-712 Korea Republic of Graduate Program of Medical System Engineering Gwangju Institute of Science and Technology Gwangju 500-712 Korea Republic of Advanced Photonics Research Institute Gwangju Institute of Science and Technology Gwangju 500-712 Korea Republic of

ISBN: (纸本)9780977565771

A photonic crystal fiber (PCF) based dual-color nonlinear microscope that combines coherent anti-Stokes Raman scattering (CARS) microscopy and two-photon excitation fluorescence (TPEF) microscopy was developed and applied to imaging of polystyrene beads, lily pollens, and live breast cancer cells using a femtosecond laser. © 2011 IEEE.

关键词： Photonic crystal fibers

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Physical limits on chemical sensing in bounded domains

arXiv

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arXiv 2024年

作者： McCusker, Daniel R. Lubensky, David K. Applied Physics Graduate Program University of Michigan United States Department of Physics University of Michigan United States

Cells respond to chemical cues, and the precision with which they can sense these cues is fundamentally limited by the stochastic nature of diffusion and ligand binding. Berg and Purcell famously investigated how well a small sensor in an infinite ligand bath can determine the ligand concentration, and a number of subsequent analyses have refined and built upon their classical estimates. Not all concentration sensing problems, however, occur in such an infinite geometry. At different scales, subcellular sensors and cells in tissues are both often confronted with signals whose diffusion is affected by confining boundaries. It is thus valuable to understand how basic limits on chemosensation depend on the sensor’s size and on its position in the domain in which ligand diffuses. Here we compute how sensor size and proximity to reflecting boundaries affect the diffusion-limited precision of chemosensation for various geometries in one and three dimensions. We derive analytical expressions for the sensing limit in these geometries. Among our conclusions is the surprising result that, in certain circumstances, smaller sensors can be more effective than larger sensors. This effect arises from a trade-off between spatial averaging and time averaging that we analyze in detail. We also find that proximity to confining boundaries can degrade a sensor’s precision significantly compared to the precision of the same sensor far from any boundaries. Copyright © 2024, The Authors. All rights reserved.

关键词： Ligands

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Singular vectors of sums of rectangular random matrices and optimal estimation of high-rank signals: The extensive spike model

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Physical Review E 2023年第5期108卷 054129-054129页

作者： Itamar D. Landau Gabriel C. Mel Surya Ganguli Department of Applied Physics Stanford University Stanford California 94305 USA Neuroscience Graduate Program Stanford University Stanford California 94305 USA

Across many disciplines spanning from neuroscience and genomics to machine learning, atmospheric science, and finance, the problems of denoising large data matrices to recover hidden signals obscured by noise, and of estimating the structure of these signals, is of fundamental importance. A key to solving these problems lies in understanding how the singular value structure of a signal is deformed by noise. This question has been thoroughly studied in the well-known spiked matrix model, in which data matrices originate from low-rank signal matrices perturbed by additive noise matrices, in an asymptotic limit where matrix size tends to infinity but the signal rank remains finite. We first show, strikingly, that the singular value structure of large finite matrices (of size ∼1000) with even moderate-rank signals, as low as 10, is not accurately predicted by the finite-rank theory, thereby limiting the application of this theory to real data. To address these deficiencies, we analytically compute how the singular values and vectors of an arbitrary high-rank signal matrix are deformed by additive noise. We focus on an asymptotic limit corresponding to an extensive spike model, in which both the signal rank and the size of the data matrix tend to infinity at a constant ratio. We map out the phase diagram of the singular value structure of the extensive spike model as a joint function of signal strength and rank. We further exploit these analytics to derive optimal rotationally invariant denoisers to recover the hidden high-rank signal from the data, as well as optimal invariant estimators of the signal covariance structure. Our extensive-rank results yield several conceptual differences compared to the finite-rank case: (1) as signal strength increases, the singular value spectrum does not directly transition from a unimodal bulk phase to a disconnected phase, but instead there is a bimodal connected regime separating them; (2) the signal singular vectors can be partiall

关键词： Stochastic inference Data analysis Random matrix theory Statistical methods Stochastic analysis methods

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Photoassociative spectroscopy of Sr87

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Physical Review A 2021年第2期103卷 023111-023111页

作者： J. C. Hill W. Huie P. Lunia J. D. Whalen S. K. Kanungo Y. Lu T. C. Killian Department of Physics and Astronomy Rice University Houston Texas 77005 USA Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston Texas 77005 USA

We demonstrate photoassociation (PA) of ultracold fermionic Sr87 atoms. The binding energies of a series of molecular states on the Σu+15s2S01+5s5pP11 molecular potential are fit with the semiclassical LeRoy-Bernstein model, and PA resonance strengths are compared to predictions based on the known S01+S01 ground-state potential. Similar measurements and analysis were performed for the bosonic isotopes Sr84 and Sr86, allowing a combined analysis of the long-range portion of the excited-state potential and determination of the 5s5pP11 atomic state lifetime of 5.20±0.02ns. The results enable prediction of PA rates across a wide range of experimental conditions.

关键词： Atomic spectra Cold and ultracold molecules Molecular spectra Photoassociation Ultracold collisions

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Accuracy of DFT computed oxygen-vacancy formation energies and high-throughput search of solar thermochemical water-splitting compounds

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Physical Review Materials 2023年第6期7卷 065403-065403页

作者： Bianca Baldassarri Jiangang He Xin Qian Emanuela Mastronardo Sean Griesemer Sossina M. Haile Christopher Wolverton Graduate Program in Applied Physics Northwestern University Evanston Illinois USA Department of Materials Science and Engineering Northwestern University Evanston Illinois USA

The enthalpy change involved in metal oxide reduction is a key quantity in various processes related to energy conversion and storage and is of particular interest for computational prediction. Often this prediction involves the simulation of a high-temperature reduction process with a 0-K methodology like density functional theory (DFT), and it is not infrequent for the high temperature and 0-K stable crystal structures to differ. This introduces a conundrum with regard to the choice of crystal structure to utilize in the computation, with approaches in the literature varying and experimental validation remaining scarce. In this work, we address both the crystal structure conundrum and the experimental validation, and then apply the insights we gain to guide a high-throughput search for new materials for solar thermochemical water-splitting applications. By computing the DFT+U oxygen-vacancy formation energy (ΔEvf) of a selection of ABO3 compounds and comparing different crystal structures for each composition, we highlight the issues that arise when the structure utilized in the computation is dynamically unstable at 0 K, namely the presence of an artificial lowering of ΔEvf, and the lack of convergence of ΔEvf with cell size. We solve these limitations by identifying and employing a suitable surrogate dynamically stable structure. We then validate the predictive power of our calculations against appositely generated experimental measurements of reduction enthalpy for a series of Hubbard U values, finding an accuracy ranging between 0.2–0.6 eV/O. In light of such conclusions, we revise and expand a previous a high-throughput DFT study on ABO3 perovskite oxides. We provide a list of candidate STCH materials, highlight trends with redox-active cation and structural distortion, and identify Mn4+, Mn3+, and Co3+ as the most promising redox-active cations.

关键词： Energy applications First-principles calculations Hydrogen energy

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Lumen loaded of kenaf pulp with magnetic pigment

Lumen loaded of kenaf pulp with magnetic pigment

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59th Appita Annual Conference and Exhibition, incorporating the 13th ISWFPC: International Symposium on Wood, Fibre and Pulping Chemistry

作者： Zakaria, Sarani Hoong, Ong Boon Ahmad, Sahrim Hj. Abdullah, Mustaffc Hj. Van De Ven, T.G.M. Yamauchi, Tatsuo Materilsl Science Program School of Applied Physics Universiti Kebangsaan Malaysia 43600 Bangi Malaysia Pulp and Paper Research Center McGill University Montreal Canada Graduate School Faculty of Agricultre Kyoto University Kyoto

Lumen-loading technology allows filler particles to be introduced exclusively into the lumens of the fibres while leaving the external surfaces free of filler. This study focuses on the development of lumen-loading process for the preparation of magnetic pulp. Magnetic pulp was prepared from unbleached kraft pulp lumen-loaded with magnetite (Fe3O4). Cationic polyethylenimine (PEI) or alum as retention aids in the lumen-loading process produced a better retention of the pigments in the preparation of this magnetic pulp. The physical properties of loading pup showed a decreased value as the filler content increased. The SEM picture showed the deposition of filler in the lumen.

关键词： Kenaf fibers

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Model for describing plasmonic nanolasers using Maxwell-Liouville equations with finite-difference time-domain calculations

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Physical Review A 2017年第5期96卷 053825-053825页

作者： Dhara J. Trivedi Danqing Wang Teri W. Odom George C. Schatz Department of Chemistry Northwestern University Evanston Illinois 60208 USA Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208 USA

We present a theoretical study of lasing action when plasmonic metallic structures that show lattice plasmon resonances are embedded in a gain medium. Our model combines classical electrodynamics for arrays of gold nanoparticles with a four-level quantum Liouville model of the laser dye photophysics. A numerical solution was implemented using finite-difference time-domain calculations coupled with a finite-difference solution to the Liouville equation. A particular focus of this work is the influence of dephasing in the quantum dynamics on the emission intensity at the threshold for lasing. We find that dephasing in the quantum system leads to reduced lasing emission, but with little effect on the long-term population inversion. Both electronic and vibrational dephasing is considered, but only electronic dephasing is significant, with the fully dephased result appearing for dephasing times comparable to plasmon dephasing (∼10 fs) while fully coherent results involve >100 ps dephasing times as determined by the rate of stimulated emission. There are factor-of-2 differences between the Maxwell-Liouville results (greater emission intensities and narrower widths) compared to the corresponding results of rate-equation models of the dye states, which indicates the importance of using the Maxwell-Liouville approach in modeling these systems. We also examine rate-equation models with and without constraints arising from the Pauli exclusion principle, and we find relatively small effects.

关键词： Laser dynamics Nanophotonics Plasmonics Plasmons Dye lasers Finite-difference time-domain method

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Phase-controlled switching between incoherent optical images in a double-Λ system

Phase-controlled switching between incoherent optical images...

引用

Quantum Information and Measurement, QIM 2012

作者： Kim, Bongjune Park, Young Ho Sohn, Byoung Uk Ko, Do-Keyung Oh, Cha-Hwan Kang, Hoonsoo Quantum Optics Lab Advanced Photonics Research Institute GIST Gwangju 500-712 Korea Republic of Department of Physics Hanyang University Seoul 133-791 Korea Republic of Graduate program of Photonics and Applied Physics GIST Gwangju 500-712 Korea Republic of

ISBN: (纸本)9781557529398

The coherent control of optical images has garnered attention because the range of information embedded in optical images is expected to be controlled in high efficiency. Recently, the storage of optical images using coherent control techniques opened a method for multiple information storage. Image control in coherent medium might move up new era of quantum information technology since the generation of entangled image pairs was realized with parametric process in coherent medium. One of the most important optical controls is switch for information distribution. Here, phase-controlled optical image switching with low light intensity was demonstrated in a double-Λ system. Switching by interference in a double-Λ system was observed as having a 90 % switching depth between incoherent image pixels. Two independent laser sources were adopted for a double-Λ system such that images inscribed in two weak probe lights were incoherent with each other.

关键词： Diode lasers Image storage Laser sources Light intensity Phase shift Quantum information Atom optics (020.1335) Coherence (030.1640) Coherent optical effects (030.1670)

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Circuit quantization in the presence of time-dependent external flux

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Physical Review B 2019年第17期99卷 174512-174512页

作者： Xinyuan You J. A. Sauls Jens Koch Northwestern–Fermilab Center for Applied Physics and Superconducting Technologies Northwestern University Evanston Illinois 60208 USA Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208 USA Department of Physics and Astronomy Northwestern University Evanston Illinois 60208 USA

Circuit quantization links a physical circuit to its corresponding quantum Hamiltonian. The standard quantization procedure generally assumes any external magnetic flux to be static. Time dependence naturally arises, however, when flux is modulated or when flux noise is considered. In this case, application of the existing quantization procedure can lead to inconsistencies. To resolve these, we generalize circuit quantization to incorporate time-dependent external flux.

关键词： Quantum information with solid state qubits Josephson junctions SQUID Superconducting qubits

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Dipolar Weyl semimetals

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Physical Review B 2024年第8期109卷 L081101-L081101页

作者： Alexander C. Tyner Shouvik Sur Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208 USA Department of Physics and Astronomy Rice Center for Quantum Materials Rice University Houston Texas 77005 USA

In Weyl semimetals, Weyl points act as monopoles and antimonopoles of the Berry curvature, with a monopole-antimonopole pair producing a net-zero Berry flux. When inversion symmetry is preserved, the two-dimensional (2D) planes that separate a monopole-antimonopole pair of Weyl points carry quantized Berry flux. In this work, we introduce a class of symmetry-protected Weyl semimetals which host monopole-antimonopole pairs of Weyl points that generate a dipolar Berry flux. Thus, both monopolar and dipolar Berry fluxes coexist in the Brillouin zone, which results in two distinct types of topologically nontrivial planes separating the Weyl points, carrying either a quantized monopolar or a quantized dipolar flux. We construct a topological invariant—the staggered Chern number—to measure the latter, and employ it to topologically distinguish between various Weyl points. Finally, through a minimal two-band model, we investigate physical signatures of bulk topology, including surface Fermi arcs, zero-energy hinge states, and response to insertion of a π-flux vortex.

关键词： Dipolar interaction Symmetry protected topological states Weyl semimetal

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