scholarly journals Decelerated lattice excitation and absence of bulk phonon modes at surfaces: Ultra-fast electron diffraction from Bi(111) surface upon fs-laser excitation

2019 ◽  
Vol 6 (6) ◽  
pp. 065101 ◽  
Author(s):  
V. Tinnemann ◽  
C. Streubühr ◽  
B. Hafke ◽  
T. Witte ◽  
A. Kalus ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Fast Electron ◽  
Laser Excitation ◽  
Phonon Modes ◽  
Fs Laser ◽  
Bulk Phonon

scholarly journals Theoretical study of the ultrashort dynamics in graphene after fs-laser excitation

2019 ◽  
Vol 205 ◽  
pp. 05006 ◽  
Author(s):  
Krylow Sergej ◽  
Garcia Martin E.
Keyword(s):  
Decay Time ◽  
Theoretical Study ◽  
Laser Excitation ◽  
Low Frequency ◽  
Ultrafast Laser ◽  
Ab Initio Molecular Dynamics ◽  
Fast Decay ◽  
Phonon Modes ◽  
Fs Laser ◽  
Dynamics Simulations

We report on the calculation of the full dynamics of graphene after ultrafast laser excitation using ab-initio molecular dynamics simulations. Our calculations show a biexponential decay of the (100) and (110) Bragg peaks in time, similar to experimental results. Furthermore, we calculate the time-evolution of the phonon energies averaged over sets of phonons, chosen by their phonon frequencies. Our results suggest that the fast decay time can be accounted by phonon-phonon interactions rather than the generation of SCOPs. The slower decay time is governed by the equilibration of the system with low frequency phonon modes.

From Semiconductor to Metal in a Flash: Observing Ultrafast Laser-Induced Phase Transformations

1997 ◽  
Vol 481 ◽  
Author(s):  
J. P. Callan ◽  
A. M.-T. Kim ◽  
L. Huangt ◽  
E. N. Glezer ◽  
E. Mazur
Keyword(s):  
Phase Transformations ◽  
Dielectric Function ◽  
Spectral Range ◽  
Laser Excitation ◽  
Spectroscopic Technique ◽  
Ultrafast Laser ◽  
Lattice Heating ◽  
Fs Laser

ABSTRACTWe use a new broadband spectroscopic technique to measure ultrafast changes in the dielectric function of a material over the spectral range 1.5–3.5 eV following intense 70-fs laser excitation. The results reveal the nature of the phase transformations which occur in the material following excitation. We studied the response of GaAs and Si. For GaAs, there are three distinct regimes of behavior as the pump fluence is increased — lattice heating, lattice disordering, and a semiconductor-to-metal transition.

scholarly journals lntersubband Relaxation in Step Quantum Well Structures

VLSI Design ◽  
1998 ◽  
Vol 8 (1-4) ◽  
pp. 289-293
Author(s):  
J. P. Sun ◽  
H. B. Teng ◽  
G. I. Haddad ◽  
M. A. Stroscio ◽  
G. J. Iafrate
Keyword(s):  
Quantum Well ◽  
Form Factors ◽  
Phonon Energy ◽  
Longitudinal Optical Phonon ◽  
Relaxation Rates ◽  
Phonon Modes ◽  
Quantum Well Structures ◽  
Bulk Phonon ◽  
Interface Phonons ◽  
Intersubband Relaxation

Intersubband relaxation due to electron interactions with the localized phonon modes plays an important role for population inversion in quantum well laser structures designed for intersubband lasers operating at mid-infrared to submillimeter wavelengths. In this work, intersubband relaxation rates between subbands in step quantum well structures are evaluated numerically using Fermi's golden rule, in which the localized phonon modes including the asymmetric interface modes, symmetric interface modes, and confined phonon modes and the electron – phonon interaction Hamiltonians are derived based on the macroscopic dielectric continuum model, whereas the electron wave functions are obtained by solving the Schrödinger equation for the heterostructures under investigation. The sum rule for the relationship between the form factors of the various localized phonon modes and the bulk phonon modes is examined and verified for these structures. The intersubband relaxation rates due to electron scattering by the asymmetric interface phonons, symmetric interface phonons, and confined phonons are calculated and compared with the relaxation rates calculated using the bulk phonon modes and the Fröhlich interaction Hamiltonian for step quantum well structures with subband separations of 36 meV and 50meV, corresponding to the bulk longitudinal optical phonon energy and interface phonon energy, respectively. Our results show that for preferential electron relaxation in intersubband laser structures, the effects of the localized phonon modes, especially the interface phonon modes, must be included for optimal design of these structures.

scholarly journals A compact tunable quadrupole lens for brighter and sharper ultra-fast electron diffraction imaging

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xi Yang ◽  
Lihua Yu ◽  
Victor Smaluk ◽  
Guimei Wang ◽  
Yoshitreu Hidaka ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Fast Electron ◽  
Quadrupole Lens ◽  
Diffraction Imaging

Population kinetics of the fluorescing M Na center state in CaF 2 upon fs laser excitation at 392 nm and 262 nm

2010 ◽  
Author(s):  
C. Karras ◽  
C. Mühlig ◽  
W. Paa ◽  
H. Stafast ◽  
W. Triebel ◽  
...  
Keyword(s):  
Laser Excitation ◽  
Population Kinetics ◽  
Fs Laser ◽  
Kinetics Of

scholarly journals Structural model of cowlesite by fast electron diffraction tomography

2017 ◽  
Vol 73 (a2) ◽  
pp. C999-C999 ◽  
Author(s):  
Mauro Gemmi ◽  
Enrico Mugnaioli ◽  
Jeremy David ◽  
Giuseppe Cruciani ◽  
Marco Merlini
Keyword(s):  
Electron Diffraction ◽  
Fast Electron ◽  
Structural Model ◽  
Diffraction Tomography

scholarly journals High-frequency cavity optomechanics using bulk acoustic phonons

2019 ◽  
Vol 5 (4) ◽  
pp. eaav0582 ◽  
Author(s):  
Prashanta Kharel ◽  
Glen I. Harris ◽  
Eric A. Kittlaus ◽  
William H. Renninger ◽  
Nils T. Otterstrom ◽  
...  
Keyword(s):  
Ground State ◽  
High Frequency ◽  
Optical Cavity ◽  
Parametric Instability ◽  
Phonon Modes ◽  
Power Laser ◽  
Quantum Operations ◽  
Cavity Modes ◽  
Laser Oscillators ◽  
Bulk Phonon

To date, microscale and nanoscale optomechanical systems have enabled many proof-of-principle quantum operations through access to high-frequency (gigahertz) phonon modes that are readily cooled to their thermal ground state. However, minuscule amounts of absorbed light produce excessive heating that can jeopardize robust ground-state operation within these microstructures. In contrast, we demonstrate an alternative strategy for accessing high-frequency (13 GHz) phonons within macroscopic systems (centimeter scale) using phase-matched Brillouin interactions between two distinct optical cavity modes. Counterintuitively, we show that these macroscopic systems, with motional masses that are 1 million to 100 million times larger than those of microscale counterparts, offer a complementary path toward robust ground-state operation. We perform both optomechanically induced amplification/transparency measurements and demonstrate parametric instability of bulk phonon modes. This is an important step toward using these beam splitter and two-mode squeezing interactions within bulk acoustic systems for applications ranging from quantum memories and microwave-to-optical conversion to high-power laser oscillators.

Identification of soft phonon modes in Ge–Sb–Te using electron diffraction

2005 ◽  
Vol 98 (3) ◽  
pp. 034506 ◽  
Author(s):  
Muneyuki Naito ◽  
Manabu Ishimaru ◽  
Yoshihiko Hirotsu ◽  
Masaki Takashima
Keyword(s):  
Electron Diffraction ◽  
Phonon Modes
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