A5044513118- Advanced Fiber Laser Technologies
- Semiconductor Lasers and Optical Devices
- Photonic and Optical Devices
- Nonlinear Dynamics and Pattern Formation
- Force Microscopy Techniques and Applications
- Mechanical and Optical Resonators
- Quantum optics and atomic interactions
- Adhesion, Friction, and Surface Interactions
- Solid State Laser Technologies
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Optical Network Technologies
- Photonic Crystal and Fiber Optics
- Atomic and Subatomic Physics Research
- Advanced Memory and Neural Computing
- Semiconductor materials and devices
- Nonlinear Photonic Systems
- Advanced Fiber Optic Sensors
- Theoretical and Computational Physics
- Spectroscopy and Laser Applications
- Semiconductor Quantum Structures and Devices
- stochastic dynamics and bifurcation
- Neural Networks and Reservoir Computing
- Brake Systems and Friction Analysis
- Lubricants and Their Additives
University of Central Florida
2021-2025
Oak Ridge National Laboratory
2012-2024
University of Tennessee at Knoxville
2009-2019
Advanced Engineering (Czechia)
2008
Pohang University of Science and Technology
2007
Emory University
1995-2000
Georgia Institute of Technology
1995
Tel Aviv University
1990-1993
Israel Institute for Biological Research
1990
The possibility of eliminating chaos in a dynamical system or decreasing the leading Liapunov exponent by applying weak periodic external forcing to is demonstrated through example periodically driven pendulum. applications also results other striking changes dynamics such as stabilization narrow subharmonic steps and achievement very low winding numbers.
We have studied the dynamical routes toward phase-locking of coupled, high-power, highly heterogeneous, low fill factor arrays blue diodes. demonstrated coherent beam combining and phase locking large groups lasers in linear 1D array broad-area laser diodes emitting around 443 nm. The was confirmed by measuring clear stable far-field interference fringes comparing with a numerically calculated intensity profile. can be tuned between in-phase out-of-phase super modes slightly changing...
We propose a new algorithm to control frictional dynamics of small array particles towards preassigned values the average sliding velocity. The is based on concepts non-Lipschitzian and terminal attractor. Extensive numerical simulations illustrate robustness, efficiency, convenience algorithm.
We have coherently combined a high-power broad-area laser diode array by using feedback loop closed off-axis external Talbot cavity. The from two gratings provides transverse-mode control of lasers. configuration the cavity implements diffractive coupling among diodes. Feedback increases quality factor and spectrum selection capability. As result, spatial coherence was improved spectral linewidth narrowed down. high visibility far-field profile indicates that achieved. also observed...
We find that the natural antiphasing tendency in linear solid-state laser arrays can be overcome by an injected field, even if N elements are not identical. derive a condition for full entrainment agrees well with numerical simulations using experimentally accessible parameters. The resulting output intensity saturates near maximum coherent value of ${\mathit{N}}^{2}$ times single laser. entrained modulated prescribed manner suitable choice field.
We studied the effect of periodic normal (out-of-plane) surface vibrations on friction in an atomic force microscope experiment. Vibration frequency was varied range 1–100kHz, and vibration amplitude a few nanometers. observed reduction orders magnitude coefficient due to vibrations. Friction is over wide frequencies amplitudes. Very low values (of order 0.01) were measured. Our numerical simulation based minimalist modeling qualitatively agrees with experimental results. Based simulations,...
We explored a path of achieving high quality phase-locking broad-area laser diode (BALD) array that operates at electrical to optical power conversion efficiency (PCE). found (a) improving single transverse mode control for each individual BALD, (b) employing global Talbot coupling among diodes, and (c) enhancing strength diodes are key factors in BALD array. Subsequently, we redesigned improved V-shaped external cavity employed low reflectivity anti-reflection (AR) coated, low-"smile" meet...
We suggest that coupling-induced orbit hopping is one possible mechanism for stick-slip dynamics. This dominant in the highly nonlinear regime. Our example a one-dimensional array of nonlinearly coupled oscillators subject to strong periodic potential. The dynamics leads fundamentally different friction law, particular when driving force barely larger than minimal needed start motion. find dramatic increase coefficient compared single uncoupled oscillator, even though same constant f applied...
We study the nonlinear contribution to stick-slip motion in a weakly coupled discrete one-dimensional array of oscillators subject periodic potential. find dramatic increase friction coefficient compared that single uncoupled oscillator, even though same constant force $f$ is applied each oscillator array. The sliding found diverge as $\ensuremath{\eta}\ensuremath{\propto}{(\ensuremath{\kappa}\ensuremath{-}{\ensuremath{\kappa}}_{c})}^{\ensuremath{-}\frac{1}{2}}$, where...
We present a numerical study of control chaos in model multimode neodymium-doped yttrium aluminum garnet laser using periodic perturbations accessible parameters. show that small modulation either the losses or pump can eliminate make system even more chaotic. Depending on parameters perturbation, two qualitatively different outputs be achieved. \textcopyright{} 1996 The American Physical Society.
Thin carbon foils are used as strippers for charge exchange injection into high intensity proton rings. However, the stripping become radioactive and produce uncontrolled beam loss, which is one of main factors limiting power in Recently, we presented a scheme laser an ${\mathrm{H}}^{\ensuremath{-}}$ Spallation Neutron Source (SNS) ring. First, atoms converted to ${\mathrm{H}}^{0}$ by magnetic field, then excited from ground state upper levels laser, states protons field. In this paper...
We designed a V-shape external Talbot cavity for broad-area laser diode array and demonstrated coherent beam combining at high power with narrow spectral linewidth. The provides good mode-discrimination does not require spatial filter. A multi-lobe far-field profile generated by low filling-factor phase-locked is confirmed our numerical simulation.
Noise and disorder are known, in certain circumstances for systems, to improve the level of coherence over that noise-free system. Examples include cases which enhances response periodic signals, those where it suppresses chaotic behavior. We report a new type disorder-enhancing mechanism, observed model describes dynamics external cavity-coupled semiconductor laser arrays, one mitigates (and overcomes) desynchronization effects due different source. Here, we demonstrate stabilization...
When a discrete nonlinear array is driven across periodic surface spatially coherent modes of motion can coexist associated with different average velocities due to resonant parametric forcing the particle fluctuations by center mass motion. Depending on coupling strength $\ensuremath{\kappa}$ and size $N$, jumps in minimum friction (maximum velocity) exhibited occur at ${\ensuremath{\kappa}}_{m}(N)\ensuremath{\sim}(N/m{)}^{2}$ as new stabilize are selected dynamics. The existence such...
In this letter, a method to measure the torsional spring constant of microcantilever is described. The cantilever was twisted laterally without any normal load by inducing Lorentz force. An electrical current applied in magnetic field, and resonance frequency obtained. Based on observation that same as second peak thermally vibrating cantilever, ratio deflection easily obtained from simple relationship. For used here, 11.24 N/m, 28 times greater than constant.
We study memory states of a circuit consisting small inductively coupled Josephson junction array and introduce basic (write, read, reset) operations logics the circuit. The presented operation paradigm is fundamentally different from conventional single quantum flux logics. calculate stability diagrams zero-voltage outline also access times energies for operations.
We present numerical and experimental evidence which demonstrates that under certain conditions friction can be reduced by spatial disorder and/or thermal noise. discuss possible mechanisms for this behavior.
Pulsed lasers with pulse durations of nanosecond to millisecond are very important tools for free-space optical communication, LADAR, laser material processing, and sensing. Although Q-switched solid-state or gas currently the most popular light sources these purposes, pulsed semiconductor have potential above applications because their compactness, accessibility direct modulation, inherently large electrical conversion efficiency. The drawbacks high-power poor beam quality low coherence...
A compound external cavity is designed and implemented to achieve a homogeneous spectrum distribution of broad area laser diodes in an array narrow the spectral linewidth entire array. The composed optical coupler Littrow with telescope along fast axis. inhomogeneous individual generated by "smile" effect was reduced telescope. effective transverse coupling among enhanced coupler, which further 49-emitter 0.1 nm at output power 12.5 W.
We study the dynamics of two coupled solid state lasers subject to an injected field. A singular perturbation technique is used reduce full set rate equations; we present a comprehensive bifurcation analysis resulting phase model. find four distinct routes entrainment as field amplitude increases; diagram predicts that (reflected in total intensity) does not monotonically improve with strength. Our numerical simulations suggest reduced model captures relevant well beyond asymptotic regime...
In this Letter we investigate a symmetry-breaking transition in the Frenkel-Kontorova model for finite chains with free-end boundary conditions. We present detailed study of behavior vicinity transition. It is shown that gap phonon spectrum, disorder parameter, and reflection-symmetry parameter display scaling properties close to Their associated critical exponents are discussed related displacements particles chains.