A5010981863- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Particle accelerators and beam dynamics
- Mechanical and Optical Resonators
- Advanced X-ray Imaging Techniques
- Photonic and Optical Devices
- Emergency and Acute Care Studies
- Laser-Matter Interactions and Applications
- Advanced Fiber Laser Technologies
- Spectroscopy and Quantum Chemical Studies
- Photorefractive and Nonlinear Optics
- Nonlinear Optical Materials Studies
- Healthcare Policy and Management
- Advanced Electron Microscopy Techniques and Applications
- Molecular spectroscopy and chirality
- Nonlinear Optical Materials Research
- Quantum Information and Cryptography
- Quantum optics and atomic interactions
- Magnetic properties of thin films
- Solid State Laser Technologies
- Copper-based nanomaterials and applications
- Liquid Crystal Research Advancements
- Spectroscopy and Laser Applications
- Terahertz technology and applications
- Physics of Superconductivity and Magnetism
Zhejiang Sci-Tech University
2023-2024
University of California, Berkeley
1972-2022
Singapore General Hospital
2017-2021
National Heart Centre Singapore
2018
Brookhaven National Laboratory
2003-2015
National Synchrotron Light Source II
2003-2010
RIKEN BNL Research Center
2004-2007
University at Buffalo, State University of New York
1999
Lawrence Berkeley National Laboratory
1971-1993
Berkeley College
1987
We show that by using polarization coherent anti-Stokes Raman spectroscopy, the detection sensitivity of weak modes is greatly enhanced. The spectra real part, imaginary and absolute magnitude resonant nonlinear susceptibility can be separately measured. with cross sections as low 2×10−4 times 992-cm−1 mode benzene are detectable less than 10-kW-peak-power lasers.
We have demonstrated nonlinear cross-phase modulation in electro-optic crystals using intense, single-cycle terahertz (THz) radiation. Individual THz pulses, generated by coherent transition radiation emitted subpicosecond electron bunches, peak energies of up to 100 microJ per pulse. The time-dependent electric field the intense pulses induces through Pockels effect, leading spectral shifting, broadening, and copropagating laser pulses. observed THz-induced agrees well with a phase-shift model.
We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV beams. High-quality, single-shot patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (∼3 × 104 electrons) pulse electrons at 2.8 MeV. The high quality confirms that beam has normalized emittance ∼50 nm rad. transverse longitudinal coherence length is ∼11 ∼2.5 nm, respectively. timing jitter between pump laser probe was found to be ∼100 fs...
We present what are to our knowledge the first measurements of phase infrared-visible sum-frequency generation signal. introduce two techniques and apply determination polar orientation a selected group atoms within an adsorbed molecule.
We have studied the photoluminescence spectrum of ${\mathrm{Cu}}_{2}$O using a tunable dye laser. found that most luminescence peaks can be identified as due to recombination $1 s$ yellow exciton or its phonon replica. These replicas showed asymmetric broadening with increase in temperature. A few lines very strong temperature dependence disappearing rapidly at high The origins these are still matter speculation. excitation is also presented and interpreted.
Neither local modes nor extended phonons precisely describe the excitations of anharmonic solids. A simple model Hamiltonian presented here characterizes transition from oscillator to optical phonon which would take place if one could continuously increase dispersion. The is used two types transitions: a phonon-localization analog Mott for electrons, and spectral associated with appearance two-phonon bound states. In real materials, sharp probably not achievable, but striking effects may be...
We demonstrate here that nonlinear mixing of four surface-plasmon waves can be used to probe the Raman resonances liquids. The results are in good agreement with theoretical prediction. technique should useful for surface studies.
A picosecond, widely tunable, optical parametric generator–amplifier system can be constructed with barium borate and lithium triborate crystals pumped by third- or second-harmonic output of an active–passive mode-locked Nd:YAG laser. tunable several hundred mirojoules per pulse a conversion efficiency as high 30% has been obtained. The tuning range covers from 0.4 to 2.0 0.6 2.5 μm extended sum- difference-frequency generation near 0.2 in the UV 8 IR. linewidth narrowed transform limit help...
We show that optical second-harmonic generation can also be used as an effective surface probe with a submonolayer sensitivity for media without inversion symmetry. The adsorption of Sn on GaAs is example. A detailed summary all accessible elements the nonlinear susceptibility tensor χ(2) various crystal faces provided.
Far-infrared radiation generated from the difference frequency between two temperature-tuned ruby lasers has been observed over range 1.2 to 8.1 ${\mathrm{cm}}^{\ensuremath{-}1}$. Lithium niobate and quartz were used as mixing crystals. The conversion efficiency was measured a function of angle around phase-matched direction. expected spectral content far-infrared verified using Fabry-Perot interferometer.
Prolonged wait times at the emergency department (ED) are associated with increased morbidity and mortality, decreased patient satisfaction. Reducing ED is challenging. The objective of this study to determine if implementation a series interventions would help decrease time consultation (WTC) for patients within 6 months. Interventions include creation common board detailing work output, matching manpower arrivals adopting team-based model care. A retrospective analysis period from January...
<sec> <title>BACKGROUND</title> The current landscape of Emergency Care (EC) is marked by high demand leading to issues such as Department boarding, overcrowding and subsequent delays that impact the quality safety patient care. Integrating data science into EC can enhance decision-making with predictive, preventative, personalized, participatory approaches. However, gaps in adherence fairness, accountability, interpretability, responsibility are evident, particularly due barriers...
The theory of far-infrared generation by optical mixing focused Gaussian beams is developed, taking into account the effects diffraction, absorption, double refraction, and multiple total reflections at boundary surfaces. Results numerical calculations are presented. It shown that focusing pump appreciably enhances output despite strong diffraction. In a 1-cm-long crystal, optimum focal-spot size approximately equal to or smaller than wavelength for an frequency less 100...
Resonance Raman scattering in InSb near the ${E}_{1}$ transition has been measured at low temperatures for various different configurations with a tunable dye laser. The experimental curves show resonance peak an incident photon energy appreciably higher than of reflectivity spectra, contrary to predictions existing theories. Double tensor involving transitions band continuum is proposed explain result.
Experimental results on the self-focusing of a laser beam in many liquids are reported. It is shown that optical Kerr effect and electrostriction cannot explain temperature variation some liquids. Forward stimulated Brillouin scattering seems important such cases. Measurements generation Raman radiation presented. The selffocusing self-trapping forward-backward asymmetry Stokes discussed. Other qualitative features explained.
Triaging of patients at the emergency department (ED) is one key steps prior to initiation doctor consult. To improve overall wait time consultation, we have identified need reduce triage for ED patients. We seek determine if implementation a series plan, do, study, act (PDSA) cycles would within 1 year. The interventions related PDSA include refining criteria, 'eyeball' by senior nurses facilitate direct bedding patients, formation nurse clinician role, and needs analysis required nursing...
In this Letter we report the first experimental characterization of superradiance in a single-pass high-gain free-electron laser (FEL) seeded by 150 femtosecond (FWHM) Ti:sapphire laser. The nonlinear energy gain after an exponential regime was observed. We also measured evolution longitudinal phase space both and superradiant regimes. output FEL pulse duration to be as short 81 fs, roughly 50% reduction compared input seed temporal distribution radiation predicted numerical simulation...
We report the first experimental characterization of efficiency and spectrum enhancement in a laser-seeded free-electron laser using tapered undulator. Output spectra fundamental third harmonic were measured versus distance for uniform undulators. With 4% field taper over 3 m, 300% (50%) increase (third harmonic) output was observed. A significant improvement with elimination sidebands observed The experiment is good agreement predictions MEDUSA simulation code.
The study of modulated electron beams is important because they can be used to produce coherent radiation, but the modulations cause unwanted instabilities in some devices. Specifically, a free laser, proper prebunching at desired emission frequency enhance performance, while bunching resulting from and bunch compression schemes degrade performance. In photoinjector accelerator, tailoring shape drive laser pulse could as technique either or mitigate effect these modulations. This work...
We have observed shifts in energy of a number Raman modes ${\mathrm{Cu}}_{2}$O as function incident photon energy. explain such due to dispersion the phonons involved and obtain quantitative agreement between theory experiment. From our data we also determined effective mass $1s$ yellow exciton be $(3.0\ifmmode\pm\else\textpm\fi{}0.2){m}_{0}$.
Emergency Departments (EDs) worldwide are confronted with rising patient volumes causing significant strains on both Medicine and entire healthcare systems. Consequently, many EDs in a situation where the number of patients ED is temporarily beyond capacity for which designed resourced to manage―a phenomenon called Department (ED) crowding. crowding can impair quality care delivered lead longer waiting times doctor’s consult (time provider) admission hospital ward. In Singapore, total...
The anharmonicity and lifetime of the CH stretching vibration H-terminated diamond H/C(111)-(1 × 1) surface are investigated. It is found that ν1→2 transition 110 cm-1 lower than ν0→1 fundamental. Theoretical calculations show good agreement with experimental observations predict existence a strongly bound two-phonon state. A vibrational 19 ps similar ground-state recovery time measured.
The photoinduced structural dynamics in 2H-TaSe2 the charge-density wave (CDW) state is investigated using MeV ultrafast electron diffraction. By simultaneously tracking both melting of periodic lattice distortion (PLD) associated with CDW and heating, following an impulsive photoexcitation, separate contributions electronic excitation thermalization to process are disentangled time domain. Two distinct time-constants, reflecting corresponding individual subsystems, observed. Our...