Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 62, Number 17
Friday–Saturday, October 20–21, 2017; Fort Collins, CO
Session K3: Atomic, Molecular and Optical Physics IV: High Intensity and Short Wavelengths |
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Chair: Mario Marconi, Colorado State University Room: Lory Student Center 322 |
Saturday, October 21, 2017 9:25AM - 9:49AM |
K3.00001: Photo Emission from Large Electron Wave Packets in Strong Laser Fields Invited Speaker: Michael Ware We report direct measurements of the single-photon-level light emitted from large electron wavepackets being driven by high-intensity laser pulses (10$^{\mathrm{18}}$ W/cm$^{\mathrm{2}})$. The high intensities cause the electron wavepackets to drift forward at mildly relativistic speeds, red-shifting the single-photon scattered signal and allowing it to be distinguished from the 10$^{\mathrm{18}}$ photons in the driving field. We explore how the size of the electron wavepacket influence the strength of this scattered signal. A full description of the phenomenon requires Quantum Electrodynamics (QED), where both the electron and the photon are treated in a fully quantum mechanical framework. But the complexity of QED makes it intractable to describe even this simple situation. We discuss how our experimental, computational, and theoretical efforts can help guide intuition in these situations. [Preview Abstract] |
Saturday, October 21, 2017 9:49AM - 10:01AM |
K3.00002: Power scaling of extreme-ultraviolet frequency combs to the mW level per high-harmonic order Stephen Schoun, Gil Porat, Christoph Heyl, Craig Benko, Jun Ye The extreme ultraviolet (XUV) presents a barely-explored region for precision spectroscopy studies with promising targets such as ground-state transitions in few-electron atoms and ions, and even nuclear transitions. Newly-developed XUV frequency combs can reach Hz-level linewidths, but their usefulness for precision spectroscopy has been limited by their low power. XUV frequency combs are produced via high-order harmonic generation (HHG) in a weakly-ionized gas medium driven by an intense IR laser. A high repetition rate ($\gg$10 MHz) is needed for stable frequency-comb operation, but the short time interval between consecutive laser pulses ($\ll$100 ns) leads to the accumulation of a high-density steady-state plasma which inhibits phase-matching of HHG, thus restricting the conversion efficiency. By heating the gas nozzle and seeding the heavy generation gas (xenon) in a light carrier gas (helium), we significantly increase the supersonic jet velocity, thus reducing the number of laser pulses that interact with the same atom/ion, reaching the single-pulse regime at 77 MHz repetition rate. We demonstrate phase-matched high-repetition-rate HHG for the first time, and generate 2 mW at 97 nm and 0.9 mW at 63 nm, surpassing previous XUV-comb power records by an order of magnitude. [Preview Abstract] |
Saturday, October 21, 2017 10:01AM - 10:13AM |
K3.00003: Compact gain--saturated X-ray lasers down to 6.9 nm wavelength and amplification down to at 5.9 nm Alex Rockwood, Yong Wang, Shoujun Wang, Mark Berrill, Vyacheslav Shlyaptsev, Jorge Rocca Plasma-based x-ray lasers allow single-shot nano-scale imaging and other experiments requiring a large number of photons per pulse to be conducted in compact facilities. However, compact repetitively fired gain-saturated x-ray lasers have been limited to wavelengths above $\lambda =$8.8 nm. We extend their range to $\lambda \quad =$ 6.89 nm by transient traveling wave excitation of Ni-like ions in a Gd plasma created with an optimized pre-pulse followed by rapid heating with an intense sub-ps pulse. Isolectronic scaling also produced strong lasing at 6.6 nm and 6.1 nm in Ni-like Tb, and amplification at 6.4 nm and 5.89 nm in Ni-like Dy. This scaling to shorter wavelengths was obtained progressively increasing the pump pulse gracing angle. We show that the optimum grazing angle of incidence increases linearly with atomic number from 17 degrees for Z$=$42 to 43 degrees for Z$=$66, in agreement with hydrodynamic/atomic physics simulations. The results will enable applications of sub-7 nm lasers at compact facilities. [Preview Abstract] |
Saturday, October 21, 2017 10:13AM - 10:25AM |
K3.00004: 3-D Visualization of an electron and its field in a high-intensity laser focus Jacob Barker We describe the methods used to create a visualization of an electron and its field as it is reacts to a laser pulse. We use the Singh model of a laser focus to determine the trajectory of an electron. From this trajectory we are able to determine the elecromagnetic field radiated from the electron by using the Li\'enart-Wiechert potentials. We are using a virtual camera that was developed previously. We determine the color and intensity of a certain pixel by integrating along a line of sight. In order to improve perspective we added gridlines in three dimensions. We also discuss various methods used in order to improve run time. We conclude by analyzing the animation produced. [Preview Abstract] |
Saturday, October 21, 2017 10:25AM - 10:37AM |
K3.00005: Petawatt-class laser operation at 3.3 Hz and high-contrast ultrahigh-intensity $\lambda =$ 400 nm second-harmonic beamline Shoujun Wang, Yong Wang, Alex Rockwood, Bradley Luther, Reed Hollinger, Alden Curtis, Chase Calvi, Carmen S. Menoni, Jorge J. Rocca There is great interest in ultra-high intensity laser pulses for relativistic ultrahigh energy density science, ultrashort wavelength coherent and incoherent radiation sources, and particle acceleration. Here we report the demonstration of a Ti:sapphire CPA laser that generates 0.85 PW average peak power, 3.3 Hz, 30 fs pulses with an average power of 85 W. This is the highest average power obtained from a PW class laser. The system is enabled by a frequency-doubled high-energy-flash-lamp-pumped Nd:glass zig-zag slab pump laser designed to operate at repetition rates up to 5 Hz with good beam quality. Pulses containing 80{\%} of the maximum available energy were frequency doubled in a KDP crystal to generate ultra-high contrast $\lambda =$400 nm fs pulses that were focused with an f/2 parabola to obtain an intensity of 6.5\times 10$^{\mathrm{21}}$ W/cm$^{\mathrm{2}}$. Intensities greater than 2\times 10$^{\mathrm{22}}$ W/cm$^{\mathrm{2}}$ will be obtainable using f/1 focusing optics. This PW-class laser will enable relativistic plasma experiments at high repetition rate and will extend high repetition rate soft x-ray lasers to shorter wavelengths. [Preview Abstract] |
Saturday, October 21, 2017 10:37AM - 10:49AM |
K3.00006: Population of Rydberg states in short intense laser pulses Joel Venzke, Brynn Reiff, Zetong Xue, Erez Shani, Agnieszka Jaron-Becker, Andreas Becker Recently, the role of highly excited states in atoms for processes such as ionization and high harmonic generation in intense laser fields has been discussed. By solving the Time Dependent Schrodinger Equation, we are able to resolve Rydberg state populations with respect to the principal and the orbital angular quantum number at the end of the pulse. We will present results for the dependence of the angular momentum distribution in various Rydberg states on the laser parameters and the potential impact on HHG spectra and time dependent susceptibility. [Preview Abstract] |
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