Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 30 of 31

Full-Text Articles in Physics

Imaging Cf3I Conical Intersection And Photodissociation Dynamics With Ultrafast Electron Diffraction, Jie Yang, Xiaolei Zhu, Thomas J.A. Wolf, Zheng Li, J. Pedro F. Nunes, Ryan Coffee, James P. Cryan, Markus Gühr, Kareem Hegazy, Tony F. Heinz, Keith Jobe, Renkai Li, Xiaozhe Shen, Theodore Veccione, Stephen Weathersby, Kyle J. Wilkin, Charles Yoneda, Qiang Zheng, Todd J. Martinez, Martin Centurion, Xijie Wang Jul 2018

Imaging Cf3I Conical Intersection And Photodissociation Dynamics With Ultrafast Electron Diffraction, Jie Yang, Xiaolei Zhu, Thomas J.A. Wolf, Zheng Li, J. Pedro F. Nunes, Ryan Coffee, James P. Cryan, Markus Gühr, Kareem Hegazy, Tony F. Heinz, Keith Jobe, Renkai Li, Xiaozhe Shen, Theodore Veccione, Stephen Weathersby, Kyle J. Wilkin, Charles Yoneda, Qiang Zheng, Todd J. Martinez, Martin Centurion, Xijie Wang

Martin Centurion Publications

Conical intersections play a critical role in excited-state dynamics of polyatomic molecules because they govern the reaction pathways of many nonadiabatic processes. However, ultrafast probes have lacked sufficient spatial resolution to image wave-packet trajectories through these intersections directly. Here, we present the simultaneous experimental characterization of one-photon and two-photon excitation channels in isolated CF3I molecules using ultrafast gas-phase electron diffraction. In the two-photon channel, we have mapped out the real-space trajectories of a coherent nuclear wave packet, which bifurcates onto two potential energy surfaces when passing through a conical intersection. In the one-photon channel, we have resolved excitation ...


Implementation And Modeling Of A Femtosecond Laser-Activated Streak Camera, Omid Zandi, Kyle J. Wilkin, Martin Centurion Jun 2017

Implementation And Modeling Of A Femtosecond Laser-Activated Streak Camera, Omid Zandi, Kyle J. Wilkin, Martin Centurion

Martin Centurion Publications

8 June 2017) A laser-activated streak camera was built to measure the duration of femtosecond electron pulses. The streak velocity of the device is 1.89 mrad/ps, which corresponds to a sensitivity of 34.9 fs/pixels. The streak camera also measures changes in the relative time of arrival between the laser and electron pulses with a resolution of 70 fs RMS. A full circuit analysis of the structure is presented to describe the streaking field and the general behavior of the device. We have developed a general mathematical model to analyze the streaked images. The model provides an ...


High Current Table-Top Setup For Femtosecond Gas Electron Diffraction, Omid Zandi, Kyle J. Wilkin, Martin Centurion May 2017

High Current Table-Top Setup For Femtosecond Gas Electron Diffraction, Omid Zandi, Kyle J. Wilkin, Martin Centurion

Martin Centurion Publications

We have constructed an experimental setup for gas phase electron diffraction with femtosecond resolution and a high average beam current. While gas electron diffraction has been successful at determining molecular structures, it has been a challenge to reach femtosecond resolution while maintaining sufficient beam current to retrieve structures with high spatial resolution. The main challenges are the Coulomb force that leads to broadening of the electron pulses and the temporal blurring that results from the velocity mismatch between the laser and electron pulses as they traverse the sample. We present here a device that uses pulse compression to overcome the ...


Diffractive Imaging Of Coherent Nuclear Motion In Isolated Molecules, Jie Yang, Markus Guehr, Xiaozhe Shen, Renkai Li, Theodore Vecchione, Ryan Coffee, Jeff Corbett, Alan Fry, Nick Hartmann, Carsten Hast, Kareem Hegazy, Keith Jobe, Igor Makasyuk, Joseph Robinson, Matthew S. Robinson, Sharon Vetter, Stephen Weathersby, Charles Yoneda, Xijie Wang, Martin Centurion Oct 2016

Diffractive Imaging Of Coherent Nuclear Motion In Isolated Molecules, Jie Yang, Markus Guehr, Xiaozhe Shen, Renkai Li, Theodore Vecchione, Ryan Coffee, Jeff Corbett, Alan Fry, Nick Hartmann, Carsten Hast, Kareem Hegazy, Keith Jobe, Igor Makasyuk, Joseph Robinson, Matthew S. Robinson, Sharon Vetter, Stephen Weathersby, Charles Yoneda, Xijie Wang, Martin Centurion

Martin Centurion Publications

Observing the motion of the nuclear wave packets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wave packet in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 Å and temporal resolution of 230 fs full width at half maximum. The method is not only sensitive to the position but also the shape of the nuclear wave packet.


Femtosecond Gas Phase Electron Diffraction With Mev Electrons, Jie Yang, Markus Guehr, Theodore Vecchione, Matthew S. Robinson, Renkai Li, Nick Hartmann, Xiaozhe Shen, Ryan Coffee, Jeff Corbett, Alan Fry, Kelly Gaffney, Tais Gorkhover, Carsten Hast, Keith Jobe, Igor Makasyuk, Alexander Reid, Joseph Robinson, Sharon Vetter, Fenglin Wang, Stephen Weathersby, Charles Yoneda, Xijie Wang, Martin Centurion Jun 2016

Femtosecond Gas Phase Electron Diffraction With Mev Electrons, Jie Yang, Markus Guehr, Theodore Vecchione, Matthew S. Robinson, Renkai Li, Nick Hartmann, Xiaozhe Shen, Ryan Coffee, Jeff Corbett, Alan Fry, Kelly Gaffney, Tais Gorkhover, Carsten Hast, Keith Jobe, Igor Makasyuk, Alexander Reid, Joseph Robinson, Sharon Vetter, Fenglin Wang, Stephen Weathersby, Charles Yoneda, Xijie Wang, Martin Centurion

Martin Centurion Publications

We present results on ultrafast gas electron diffraction (UGED) experiments with femtosecond resolution using the MeV electron gun at SLAC National Accelerator Laboratory. UGED is a promising method to investigate molecular dynamics in the gas phase because electron pulses can probe the structure with a high spatial resolution. Until recently, however, it was not possible for UGED to reach the relevant timescale for the motion of the nuclei during a molecular reaction. Using MeV electron pulses has allowed us to overcome the main challenges in reaching femtosecond resolution, namely delivering short electron pulses on a gas target, overcoming the effect ...


Diffractive Imaging Of A Rotational Wavepacket In Nitrogen Molecules With Femtosecond Megaelectronvolt Electron Pulses, Jie Yang, Markus Guehr, Theodore Vecchione, Matthew S. Robinson, Renkai Li, Nick Hartmann, Xiaozhe Shen, Ryan Coffee, Jeff Corbett, Alan Fry, Kelly Gaffney, Tais Gorkhover, Carsten Hast, Keith Jobe, Igor Makasyuk, Alexander Reid, Joseph Robinson, Sharon Vetter, Fenglin Wang, Stephen Weathersby, Charles Yoneda, Martin Centurion, Xijie Wang Apr 2016

Diffractive Imaging Of A Rotational Wavepacket In Nitrogen Molecules With Femtosecond Megaelectronvolt Electron Pulses, Jie Yang, Markus Guehr, Theodore Vecchione, Matthew S. Robinson, Renkai Li, Nick Hartmann, Xiaozhe Shen, Ryan Coffee, Jeff Corbett, Alan Fry, Kelly Gaffney, Tais Gorkhover, Carsten Hast, Keith Jobe, Igor Makasyuk, Alexander Reid, Joseph Robinson, Sharon Vetter, Fenglin Wang, Stephen Weathersby, Charles Yoneda, Martin Centurion, Xijie Wang

Martin Centurion Publications

This work is licensed under a Creative Commons Attribution 4.0 International License.


Ultrafast Imaging Of Isolated Molecules With Electron Diffraction, Martin Centurion Feb 2016

Ultrafast Imaging Of Isolated Molecules With Electron Diffraction, Martin Centurion

Martin Centurion Publications

Recent advances in ultrafast electron diffraction offer the possibility to image isolated molecules with sub-Angstrom spatial resolution in ultrafast time scales. In particular, diffraction from aligned molecules has opened the door to retrieving three-dimensional structures directly from experimental data. In this manuscript we review the progress in ultrafast gas electron diffraction and discuss remaining challenges to achieve a temporal resolution of sub-100 fs, which is needed to observe the nuclear motion in chemical reactions in the gas phase.


Imaging Of Alignment And Structural Changes Of Carbon Disulfide Molecules Using Ultrafast Electron Diffraction, Jie Yang, Joshua Beck, Cornelis J. Uiterwaal, Martin Centurion Sep 2015

Imaging Of Alignment And Structural Changes Of Carbon Disulfide Molecules Using Ultrafast Electron Diffraction, Jie Yang, Joshua Beck, Cornelis J. Uiterwaal, Martin Centurion

Martin Centurion Publications

Imaging the structure of molecules in transient-excited states remains a challenge due to the extreme requirements for spatial and temporal resolution. Ultrafast electron diffraction from aligned molecules provides atomic resolution and allows for the retrieval of structural information without the need to rely on theoretical models. Here we use ultrafast electron diffraction from aligned molecules and femtosecond laser mass spectrometry to investigate the dynamics in carbon disulfide following the interaction with an intense femtosecond laser pulse. We observe that the degree of alignment reaches an upper limit at laser intensities below the ionization threshold, and find evidence of structural deformation ...


Gas-Phase Electron Diffraction From Laser-Aligned Molecules, Jie Yang, Martin Centurion Aug 2015

Gas-Phase Electron Diffraction From Laser-Aligned Molecules, Jie Yang, Martin Centurion

Martin Centurion Publications

Electron diffraction is a valuable tool to capture structural information from molecules in the gas phase. However, the information contained in the diffraction patterns is limited due to the random orientation of the molecules. Additional structural information can be retrieved if the molecules are aligned. Molecules can be impulsively aligned with femtosecond laser pulses, producing a transient alignment. The alignment persists only for a time on the order of a picosecond, so a pulsed electron gun is needed to record the diffraction patterns. In this manuscript, we describe the alignment process and show the changes in the diffraction pattern as ...


Mega-Electron-Volt Ultrafast Electron Diffraction At Slac National Accelerator Laboratory, Stephen Weathersby, G. Brown, Martin Centurion, T. F. Chase, Ryan Coffee, Jeff Corbett, J. P. Eichner, J. C. Frisch, A. R. Fry, M. Gühr, Nick Hartmann, Carsten Hast, R. Hettel, R. K. Jobe, E. N. Jongewaard, J. R. Lewandowski, R. K. Li, A. M. Lindenberg, Igor Makasyuk, J. E. May, D. Mccormick, M. N. Nguyen, Alexander Reid, Xiaozhe Shen, K. Sokolowski-Tinten, Theodore Vecchione, Sharon Vetter, J. Wu, Jie Yang, H. A. Dürr, Xijie Wang Jan 2015

Mega-Electron-Volt Ultrafast Electron Diffraction At Slac National Accelerator Laboratory, Stephen Weathersby, G. Brown, Martin Centurion, T. F. Chase, Ryan Coffee, Jeff Corbett, J. P. Eichner, J. C. Frisch, A. R. Fry, M. Gühr, Nick Hartmann, Carsten Hast, R. Hettel, R. K. Jobe, E. N. Jongewaard, J. R. Lewandowski, R. K. Li, A. M. Lindenberg, Igor Makasyuk, J. E. May, D. Mccormick, M. N. Nguyen, Alexander Reid, Xiaozhe Shen, K. Sokolowski-Tinten, Theodore Vecchione, Sharon Vetter, J. Wu, Jie Yang, H. A. Dürr, Xijie Wang

Martin Centurion Publications

Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition rate ...


Tilted Femtosecond Pulses For Velocity Matching In Gas-Phase Ultrafast Electron Diffraction, Ping Zhang, Jie Yang, Martin Centurion Jan 2014

Tilted Femtosecond Pulses For Velocity Matching In Gas-Phase Ultrafast Electron Diffraction, Ping Zhang, Jie Yang, Martin Centurion

Martin Centurion Publications

Recent advances in pulsed electron gun technology have resulted in femtosecond electron pulses becoming available for ultrafast electron diffraction experiments. For experiments investigating chemical dynamics in the gas phase, the resolution is still limited to picosecond time scales due to the velocity mismatch between laser and electron pulses. Tilted laser pulses can be used for velocity matching, but thus far this has not been demonstrated over an extended target in a diffraction setting. We demonstrate an optical configuration to deliver high-intensity laser pulses with a tilted pulse front for velocity matching over the typical length of a gas jet. A ...


Tilted Femtosecond Pulses For Velocity Matching In Gas-Phase Ultrafast Electron Diffraction, Ping Zhang, Jie Yang, Martin Centurion Jan 2014

Tilted Femtosecond Pulses For Velocity Matching In Gas-Phase Ultrafast Electron Diffraction, Ping Zhang, Jie Yang, Martin Centurion

Martin Centurion Publications

Recent advances in pulsed electron gun technology have resulted in femtosecond electron pulses becoming available for ultrafast electron diffraction experiments. For experiments investigating chemical dynamics in the gas phase, the resolution is still limited to picosecond time scales due to the velocity mismatch between laser and electron pulses. Tilted laser pulses can be used for velocity matching, but thus far this has not been demonstrated over an extended target in a diffraction setting. We demonstrate an optical configuration to deliver high-intensity laser pulses with a tilted pulse front for velocity matching over the typical length of a gas jet. A ...


Reconstruction Of Three-Dimensional Molecular Structure From Diffraction Of Laseraligned Molecules, Jie Yang, Varun Makhija, Vinod Kumarappan, Martin Centurion Jan 2014

Reconstruction Of Three-Dimensional Molecular Structure From Diffraction Of Laseraligned Molecules, Jie Yang, Varun Makhija, Vinod Kumarappan, Martin Centurion

Martin Centurion Publications

Diffraction from laser-aligned molecules has been proposed as a method for determining 3-D molecular structures in the gas phase. However, existing structural retrieval algorithms are limited by the imperfect alignment in experiments and the rotational averaging in 1-D alignment. Here, we demonstrate a two-step reconstruction comprising a genetic algorithm that corrects for the imperfect alignment followed by an iterative phase retrieval method in cylindrical coordinates. The algorithm was tested with simulated diffraction patterns. We show that the full 3-D structure of trifluorotoluene, an asymmetric-top molecule, can be reconstructed with atomic resolution.


Reconstruction Of Three-Dimensional Molecular Structure From Diffraction Of Laser-Aligned Molecules, Jie Yang, Varun Makhija, Vinod Kumarappan, Martin Centurion Jan 2014

Reconstruction Of Three-Dimensional Molecular Structure From Diffraction Of Laser-Aligned Molecules, Jie Yang, Varun Makhija, Vinod Kumarappan, Martin Centurion

Martin Centurion Publications

Diffraction from laser-aligned molecules has been proposed as a method for determining 3-D molecular structures in the gas phase. However, existing structural retrieval algorithms are limited by the imperfect alignment in experiments and the rotational averaging in 1-D alignment. Here, we demonstrate a two-step reconstruction comprising a genetic algorithm that corrects for the imperfect alignment followed by an iterative phase retrieval method in cylindrical coordinates. The algorithm was tested with simulated diffraction patterns. We show that the full 3-D structure of trifluorotoluene, an asymmetric-top molecule, can be reconstructed with atomic resolution.


Imaging Of Isolated Molecules With Ultrafast Electron Pulses, Christopher J. Hensley, Jie Yang, Martin Centurion Jan 2012

Imaging Of Isolated Molecules With Ultrafast Electron Pulses, Christopher J. Hensley, Jie Yang, Martin Centurion

Martin Centurion Publications

Imaging isolated molecules in three dimensions with atomic resolution is important for elucidating complex molecular structures and intermediate states in molecular dynamics. This goal has so far remained elusive due to the random orientation of molecules in the gas phase. We show that threedimensional structural information can be retrieved from multiple electron diffraction patterns of aligned molecules. The molecules are aligned impulsively with a femtosecond laser pulse and probed with a femtosecond electron pulse two picoseconds later, when the degree of alignment reaches a maximum.


Dispersion Compensation For Attosecond Electron Pulses, Peter Hansen, Cory Baumgarten, Herman Batelaan, Martin Centurion Jan 2012

Dispersion Compensation For Attosecond Electron Pulses, Peter Hansen, Cory Baumgarten, Herman Batelaan, Martin Centurion

Martin Centurion Publications

We propose a device to compensate for the dispersion of attosecond electron pulses. The device uses only static electric and magnetic fields and therefore does not require synchronization to the pulsed electron source. Analogous to the well-known optical dispersion compensator, an electron dispersion compensator separates paths by energy in space. Magnetic fields are used as the dispersing element, while a Wien filter is used for compensation of the electron arrival times. We analyze a device with a size of centimeters, which can be applied to ultrafast electron diffraction and microscopy, and fundamental studies.


Picosecond Electron Diffraction From Molecules Aligned By Dissociation, Martin Centurion, Peter Reckenthaeler, Ferenc Krausz, Ernst E. Fill Jan 2010

Picosecond Electron Diffraction From Molecules Aligned By Dissociation, Martin Centurion, Peter Reckenthaeler, Ferenc Krausz, Ernst E. Fill

Martin Centurion Publications

In gas electron diffraction an averaging over statistical directions of the molecules takes place. This results in diffraction patterns in the form of isotropic rings which yield information only on the radial distribution function displaying the inter-atomic distances. We demonstrate that by dissociating molecules with linearly polarized light the pattern becomes anisotropic. In the experiments the iodide C2F4I2 is dissociated and molecular difference intensities and difference radial distribution curves are measured for directions parallel and perpendicular to the direction of polarization. With picosecond temporal resolution the curves clearly demonstrate transient anisotropy and its decay by ...


Time-Resolved Electron Diffraction From Selectively Aligned Molecules, Peter Reckenthaeler, Martin Centurion, Werner Fuß, Sergei A. Trushin, Ferenc Krausz, Ernst E. Fill May 2009

Time-Resolved Electron Diffraction From Selectively Aligned Molecules, Peter Reckenthaeler, Martin Centurion, Werner Fuß, Sergei A. Trushin, Ferenc Krausz, Ernst E. Fill

Martin Centurion Publications

We experimentally demonstrate ultrafast electron diffraction from transiently aligned molecules in the absence of external (aligning) fields. A sample of aligned molecules is generated through photodissociation with femtosecond laser pulses, and the diffraction pattern is captured by probing the sample with picosecond electron pulses shortly after dissociation—before molecular rotation causes the alignment to vanish. In our experiments the alignment decays with a time constant of 2.6 ± 1.2 ps.


Picosecond Imaging Of Low-Density Plasmas By Electron Deflectometry, Martin Centurion, P. Reckenthaeler, F. Krausz, E. E. Fill Feb 2009

Picosecond Imaging Of Low-Density Plasmas By Electron Deflectometry, Martin Centurion, P. Reckenthaeler, F. Krausz, E. E. Fill

Martin Centurion Publications

We have imaged optical-field ionized plasmas with electron densities as low as 1013 cm−3 on a picosecond timescale using ultrashort electron pulses. Electric fields generated by the separation of charges are imprinted on a 20 keV probe electron pulse and reveal a cloud of electrons expanding away from a positively charged plasma core. Our method allows for a direct measurement of the electron energy required to escape the plasma and the total charge. Simulations reproduce the main features of the experiment and allow determination of the energy of the electrons.


Ultrashort Pulse Electron Gun With A Mhz Repetition Rate, D. Wytrykus, Martin Centurion, P. Reckenthaeler, F. Krausz, A. Apolonski, E. Fill Jan 2009

Ultrashort Pulse Electron Gun With A Mhz Repetition Rate, D. Wytrykus, Martin Centurion, P. Reckenthaeler, F. Krausz, A. Apolonski, E. Fill

Martin Centurion Publications

We report the construction of an electron gun emitting ultrashort pulses with a repetition rate of 2.7 MHz. The gun works at an acceleration voltage of 20 kV and is operated with a laser oscillator having an ultralong cavity. A low number of electrons per pulse eliminates space charge broadening. Electron yield and beam profiles are measured for operation with laser wavelengths of 800, 400, and 266 nm. The initial energy spread of the electrons is determined for these three wavelengths, and pulse durations of 600, 390, and 270 fs are inferred from the data.


Proposed Method For Measuring The Duration Of Electron Pulses By Attosecond Streaking, Peter Reckenthaeler, Martin Centurion, V. S. Yakovlev, M. Lezius, F. Krausz, Ernst E. Fill Jan 2008

Proposed Method For Measuring The Duration Of Electron Pulses By Attosecond Streaking, Peter Reckenthaeler, Martin Centurion, V. S. Yakovlev, M. Lezius, F. Krausz, Ernst E. Fill

Martin Centurion Publications

We propose a method to measure the duration of ultrashort electron pulses. The electron pulse to be measured impinges on a solid target, causing the emission of Auger electrons through impact ionization. The energy spectrum of the Auger electrons is altered in the presence of an intense femtosecond laser field. Due to the extremely short lifetime of the Auger effect, this effect can be used to generate cross correlation between a laser and an electron pulse. The method is applicable to electron pulses ranging from hundreds of attoseconds to hundreds of femtoseconds in duration, and for a few hundreds of ...


Harmonic Holography: A New Holographic Principle, Ye Pu, Martin Centurion, Demetri Psaltis Nov 2007

Harmonic Holography: A New Holographic Principle, Ye Pu, Martin Centurion, Demetri Psaltis

Martin Centurion Publications

The process of second harmonic generation (SHG) has a unique property of forming a sharp optical contrast between noncentrosymmetric crystalline materials and other types of material, which is a highly valuable asset for contrast microscopy. The coherent signal obtained through SHG also allows for the recording of holograms at high spatial and temporal resolution, enabling whole-field four-dimensional microscopy for highly dynamic microsystems and nanosystems. Here we describe a new holographic principle, harmonic holography (H2), which records holograms between independently generated second harmonic signals and reference. We experimentally demonstrate this technique with digital holographic recording of second harmonic signals upconverted ...


Modulational Instability In Nonlinearity-Managed Optical Media, Martin Centurion, Mason A. Porter, Ye Pu, P. G. Kevrekidis, D. J. Frantzeskakis, Demetri Psaltis Jan 2007

Modulational Instability In Nonlinearity-Managed Optical Media, Martin Centurion, Mason A. Porter, Ye Pu, P. G. Kevrekidis, D. J. Frantzeskakis, Demetri Psaltis

Martin Centurion Publications

We investigate analytically, numerically, and experimentally the modulational instability in a layered, cubically nonlinear (Kerr) optical medium that consists of alternating layers of glass and air. We model this setting using a nonlinear Schrödinger (NLS) equation with a piecewise constant nonlinearity coefficient and conduct a theoretical analysis of its linear stability, obtaining a Kronig-Penney equation whose forbidden bands correspond to the modulationally unstable regimes. We find very good quantitative agreement between the theoretical analysis of the Kronig-Penney equation, numerical simulations of the NLS equation, and the experimental results for the modulational instability. Because of the periodicity in the evolution variable ...


Modulational Instability In A Layered Kerr Medium: Theory And Experiment, Martin Centurion, Mason A. Porter, Ye Pu, P. G. Kevrekidis, D. J. Frantzeskakis, Demetri Psaltis Dec 2006

Modulational Instability In A Layered Kerr Medium: Theory And Experiment, Martin Centurion, Mason A. Porter, Ye Pu, P. G. Kevrekidis, D. J. Frantzeskakis, Demetri Psaltis

Martin Centurion Publications

We present the first experimental investigation of modulational instability in a layered Kerr medium. The particularly interesting and appealing feature of our configuration, consisting of alternating glass-air layers, is the piecewise-constant nature of the material properties, which allows a theoretical linear stability analysis leading to a Kronig-Penney equation whose forbidden bands correspond to the modulationally unstable regimes. We find very good quantitative agreement between theoretical, numerical, and experimental diagnostics of the modulational instability. Because of the periodicity in the evolution variable arising from the layered medium, there are multiple instability regions rather than just one as in a uniform medium.


Holographic Capture Of Femtosecond Pulse Propagation, Martin Centurion, Ye Pu, Demetri Psaltis Sep 2006

Holographic Capture Of Femtosecond Pulse Propagation, Martin Centurion, Ye Pu, Demetri Psaltis

Martin Centurion Publications

We have implemented a holographic system to study the propagation of femtosecond laser pulses with high temporal (150 fs) and spatial resolutions (4 μm). The phase information in the holograms allows us to reconstruct both positive and negative index changes due to the Kerr nonlinearity (positive) and plasma formation (negative), and to reconstruct three-dimensional structure. Dramatic differences were observed in the interaction of focused femtosecond pulses with air, water, and carbon disulfide. The air becomes ionized in the focal region, while in water long plasma filaments appear before the light reaches a tight focus. In contrast, in carbon disulfide the ...


Nonlinearity Management In Optics: Experiment, Theory, And Simulation, Martin Centurion, Mason A. Porter, P. G. Kevrekidis, Demetri Psaltis Jul 2006

Nonlinearity Management In Optics: Experiment, Theory, And Simulation, Martin Centurion, Mason A. Porter, P. G. Kevrekidis, Demetri Psaltis

Martin Centurion Publications

We conduct an experimental investigation of nonlinearity management in optics using femtosecond pulses and layered Kerr media consisting of glass and air. By examining the propagation properties over several diffraction lengths, we show that wave collapse can be prevented. We corroborate these experimental results with numerical simulations of the (2 + 1)-dimensional focusing cubic nonlinear Schrödinger equation with piecewise constant coefficients and a theoretical analysis of this setting using a moment method.


Erratum: Dynamics Of Filament Formation In A Kerr Medium [Phys Rev. A 71, 063811 (2005)], Martin Centurion, Ye Pu, Mankei Tsang, Demetri Psaltis Jan 2006

Erratum: Dynamics Of Filament Formation In A Kerr Medium [Phys Rev. A 71, 063811 (2005)], Martin Centurion, Ye Pu, Mankei Tsang, Demetri Psaltis

Martin Centurion Publications

We have found an error in this paper -- [Phys Rev. A 71, 063811 (2005)]. In our calculation of the intensity threshold for breakdown in CS2 we erroneously used the ionization energy of molecular CS2 (10.08 eV). The correct value should be 3.3 eV, the band gap energy of liquid CS2 . Using the band gap energy, nonlinear absorption will be a three-photon process, and the calculated breakdown threshold becomes 8.5 × 1011 W/cm2 (as opposed to the value of 2×1013 W/cm2 reported previously). Multiphoton absorption and plasma defocusing could ...


Self-Organization Of Spatial Solitons, Martin Centurion, Ye Pu, Demetri Psaltis Aug 2005

Self-Organization Of Spatial Solitons, Martin Centurion, Ye Pu, Demetri Psaltis

Martin Centurion Publications

We present experimental results on the transverse modulation instability of an elliptical beam propagating in a bulk nonlinear Kerr medium, and the formation and self-organization of spatial solitons. We have observed the emergence of order, self organization and a transition to an unstable state. Order emerges through the formation of spatial solitons in a periodic array. If the initial period of the array is unstable the solitons will tend to self-organize into a larger (more stable) period. Finally the system transitions to a disordered state where most of the solitons disappear and the beam profile becomes unstable to small changes ...


Dynamics Of Filament Formation In A Kerr Medium (With Erratum), Martin Centurion, Ye Pu, Mankei Tsang, Demetri Psaltis Jan 2005

Dynamics Of Filament Formation In A Kerr Medium (With Erratum), Martin Centurion, Ye Pu, Mankei Tsang, Demetri Psaltis

Martin Centurion Publications

We have studied the large-scale beam breakup and filamentation of femtosecond pulses in a Kerr medium. We have experimentally monitored the formation of stable light filaments, conical emission, and interactions between filaments. Three major stages lead to the formation of stable light filaments: First the beam breaks up into a pattern of connected lines (constellation), then filaments form on the constellations, and finally the filaments release a fraction of their energy through conical emission. We observed a phase transition to a faster filamentation rate at the onset of conical emission. We attribute this to the interaction of conical emissions with ...


Holographic Recording Of Laser-Induced Plasma, Martin Centurion, Ye Pu, Zhiwen Liu, Demetri Psaltis, Theodor W. Hänsch Apr 2004

Holographic Recording Of Laser-Induced Plasma, Martin Centurion, Ye Pu, Zhiwen Liu, Demetri Psaltis, Theodor W. Hänsch

Martin Centurion Publications

We report on a holographic probing technique that allows for measurement of free-electron distribution with fine spatial detail. Plasma is generated by focusing a femtosecond pulse in air. We also demonstrate the capability of the holographic technique of capturing the time evolution of the plasma-generation process.