A5005860170- Laser-Matter Interactions and Applications
- Advanced Fiber Laser Technologies
- Orbital Angular Momentum in Optics
- Laser-Plasma Interactions and Diagnostics
- Spectroscopy and Laser Applications
- Laser-induced spectroscopy and plasma
- Laser Design and Applications
- Spectroscopy and Quantum Chemical Studies
- Mass Spectrometry Techniques and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Mobile Ad Hoc Networks
- Blind Source Separation Techniques
- Energy Efficient Wireless Sensor Networks
- Photonic Crystal and Fiber Optics
- Atomic and Molecular Physics
- Photonic and Optical Devices
- Spectroscopy Techniques in Biomedical and Chemical Research
- Power Line Communications and Noise
- Network Traffic and Congestion Control
- Complexity and Algorithms in Graphs
- Particle Accelerators and Free-Electron Lasers
- Optimization and Search Problems
- Optical and Acousto-Optic Technologies
- Nonlinear Photonic Systems
- Advanced Adaptive Filtering Techniques
University of Maryland, College Park
2014-2024
Colorado State University
2023-2024
Sharif University of Technology
2008-2009
We identify a class of modal solutions for spatiotemporal optical vortex (STOV) electromagnetic pulses propagating in dispersive media with orbital angular momentum (OAM) orthogonal to propagation. find that symmetric STOVs vacuum can carry half-integer intrinsic OAM; general asymmetric medium, the OAM is quantized integer multiples parameter depends on STOV symmetry and group velocity dispersion. Our results suggest are accompanied by polaritonlike quasiparticle. The theory excellent...
Abstract Structured waves are ubiquitous for all areas of wave physics, both classical and quantum, where the wavefields inhomogeneous cannot be approximated by a single plane wave. Even interference two waves, or (evanescent) wave, provides number nontrivial phenomena additional functionalities as compared to Complex with inhomogeneities in amplitude, phase, polarization, including topological structures singularities, underpin modern nanooptics photonics, yet they equally important, e.g....
A spatiotemporal optical vortex (STOV) is an intrinsic orbital angular momentum (OAM) structure in which the OAM vector orthogonal to propagation direction [ Optica 6 , 1547 ( 2019 ) OPTIC8 2334-2536 10.1364/OPTICA.6.001547 ] and phase circulates space-time. Here, we experimentally theoretically demonstrate generation of second harmonic a STOV-carrying pulse along with conservation STOV-based OAM. Our experiments verify that photons can have perpendicular their direction.
We demonstrate the controlled spatiotemporal transfer of transverse orbital angular momentum (OAM) to electromagnetic waves: torquing light. This is a radically different situation from OAM longitudinal, spatially defined light by stationary or slowly varying refractive-index structures such as phase plates air turbulence. show that net per photon can be spatiotemporally imparted pulse only if (1) transient perturbation well overlapped with in spacetime, (2) initially has nonzero density,...
We measure the nonlinear refractive index coefficients in N₂, O₂, and Ar from visible through mid-infrared wavelengths (λ=0.4-2.4 μm). The investigated correspond to transparency windows atmosphere. Good agreement is found with theoretical models of χ((3)). Our results are essential for accurately simulating propagation ultrashort pulses
We present the first experimental evidence, supported by theory and simulation, of spatiotemporal optical vortices (STOVs). A STOV is an vortex with phase energy circulation in a plane. Depending on sign material dispersion, local electromagnetic flow saddle or spiral about STOV. STOVs are fundamental element nonlinear collapse subsequent propagation short pulses media, conserve topological charge, constraining their birth, evolution, annihilation. measure self-generated consisting...
Spatio-temporal optical vortices (STOVs) are a new type of orbital angular momentum (OAM) with phase circulation in space-time. In prior work [N. Jhajj et al., Phys. Rev X 6, 031037 (2016)], we demonstrated that STOV is universal structure emerging from the arrest self-focusing collapse leading to nonlinear self-guiding material media. Here, demonstrate linear generation and propagation free space STOV-carrying pulses. Our measurements simulations mediation space-time energy flow within...
We present time-resolved measurements of the gas acoustic dynamics following interaction spatial single- and higher-mode 50 fs, 800 nm pulses in air at 10 Hz 1 kHz repetition rates. Results are excellent agreement with hydrodynamic simulations. Under no conditions for single filaments do we find on-axis enhancement density; this occurs only multifilaments. also investigate propagation probe beams density profile induced by a extended filament. that light trapping expanding annular wave can...
We demonstrate that strong impulsive gas heating or suppression at standard temperature and pressure can occur from coherent rotational excitation de-excitation of molecular gases using a sequence non-ionizing laser pulses. For the case excitation, subsequent collisional decoherence ensemble leads to significantly exceeding plasma absorption under same focusing conditions. In both cases, macroscopic hydrodynamics be finely controlled with ~40 fs temporal sensitivity.
We present spatially resolved measurements of energy deposition into atmospheric air by femtosecond laser filaments. Single filaments formed with varying pulse and pulsewidth were examined using longitudinal interferometry, sonographic probing, direct loss measurements. measure peak average absorption ∼4 μJ/cm ∼1 for input powers up to ∼6 times the critical power self-focusing.
Under certain conditions, powerful ultrashort laser pulses can form greatly extended, propagating filaments of concentrated high intensity in gases, leaving behind a very long trail plasma. Such be much longer than the longitudinal scale over which beam typically diverges by diffraction, with possible applications ranging from laser-guided electrical discharges to power propagation atmosphere. Understanding detail microscopic processes leading filamentation requires ultrafast measurements...
The axial dependence of femtosecond filamentation in air is measured under conditions varying laser pulsewidth, energy, and focusing f-number. Filaments are characterized by the ultrafast z-dependent absorption energy from pulse diagnosed measuring local single cycle acoustic wave generated. Results compared to 2D + 1 simulations propagation, whose results highly sensitive instantaneous (electronic) part nonlinear response N2 O2. We find that recent measurements refractive index (n2)...
Single-shot supercontinuum spectral interferometry is a powerful technique for measuring transient refractive index changes. In principle, its time resolution limited only by the available probe bandwidth. However, this assumes that phase extraction has sufficient and exactly known. Using an analytical model amplitude modulation of chirped pulse weak perturbation, we show how chirp determine achievable resolution. A simple, practical precise in situ measurement described detail, sensitivity...
We measure the detailed spatiotemporal profiles of femtosecond laser pulses in infrared wavelength range λ=2.5-11 μm and absolute nonlinear response major air constituents (N2, O2, Ar) over this range. The measurements reveal wavelength-dependent pulse front tilt temporal stretching pulses.
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The electronic, rotational, and vibrational components of the ultrafast optical nonlinearity in ${\mathrm{H}}_{2}$ ${\mathrm{D}}_{2}$ are measured directly absolutely at intensities up to ionization threshold $\ensuremath{\sim}{10}^{14}\phantom{\rule{0.16em}{0ex}}{\mathrm{W}/\mathrm{cm}}^{2}$. As most basic nonlinear interactions simplest molecules exposed high fields, these results constitute a benchmark for high-field laser-matter theory simulation.
Although high field laser-induced ionization is a fundamental process underlying many applications, there have been no absolute measurements of the nonlinear polarizability atoms and molecules in presence ionization. Such information crucial, for example, understanding propagation intensity ultrashort pulses matter. Here, we present space- time-resolved ultrafast laser-driven argon, krypton, xenon, nitrogen, oxygen up to an fraction few percent. These enable determination non-perturbative...
High repetition rate laser systems enable new strategies for diagnosing plasma behavior with large datasets. Here, we define an ensemble technique that relies on randomized targeting of x-ray tracer micro-stripes. On each shot, a high-intensity pulse is focused solid target Ti stripes embedded in Al foil, randomly micro-stripe, portion stripe, or gap between stripes. High-resolution, time-integrated spectrometers capture line emission from the micro-stripe heated to sufficiently high...
In this paper, we propose a new method to recover band-limited signals corrupted by impulsive noise. The proposed successively uses adaptive thresholding and soft decisioning find the locations amplitudes of impulses. our method, after estimating positions additive noise, an algorithm, followed decision, is employed detect attenuate next step, using iterative approximation signal obtained. This used improve noise estimate. algorithm analyzed verified computer simulations. Simulation results...
We present the development of a flexible tape-drive target system to generate and control secondary high-intensity laser-plasma sources. Its adjustable design permits generation relativistic MeV particles x rays at (i.e., ≥1 × 1018 W cm-2) laser facilities, high repetition rates (>1 Hz). The compact robust structure shows good mechanical stability placement accuracy (<4 μm RMS). allows for mounting in both horizontal vertical planes, which makes it practical use cluttered experimental...
Abstract The application high intensity ultrafast lasers to compact plasma-based electron accelerators has recently been an extremely active area of research. Here, for the first time, we show experimentally and theoretically that carefully sculpting intense pulse in spatio-temporal domain allows ponderomotive pressure be used direct acceleration bunches from rest relativistic energies. With subluminal group velocity above-threshold intensity, a laser can capture accelerate electrons,...
X-ray line emission spectra can thoroughly characterize hot plasmas, especially when shapes and ratios convey distinct aspects of plasma conditions. However, the high spectral resolution required for observing is often at odds with large bandwidth to observe many across a wide range. One strategy obtain over use multiple crystals calibrated reflectivity so that intensities different be compared. Here, we explore low-resolution, wide-bandwidth mica survey spectrometer infer relative two...
Spatiotemporal optical vortices (STOVs), arise naturally during nonlinear self-focusing collapse arrest. Here, we use a 4-f pulse shaper to impose STOVs linearly on Gaussian and directly measure the vortex in spatiotemporal domains.
The nonlinear polarization response and plasma generation produced by intense optical pulses, modeled the metastable-electronic-state approach, are verified against space-and-time resolved measurements with single-shot supercontinuum spectral interferometry. This first of a kind theory-experiment comparison is done in intensity regime typical for filamentation, where self-focusing play competing roles. Excellent agreement between theory experiment shows that nonlinearity can be approximated...