Transcript Materials WG Summary Lindenberg

Materials in Extreme THz Fields
Valery Dolgashev
Hermann Duerr
Shambhu Ghimire
Hirohito Ogasawara
Haidan Wen
Aaron Lindenberg
Science:
1. Short pulse dielectric breakdown in materials – in situ measurements
THz pump / THz probe (perfect synchronization)
THz pump / optical probe
Post-mortem analysis
2. Initiation of chemical reactions on surfaces through low frequency mode resonant
Excitation: C,H,O adsorbed on surfaces. Excite oxygen-metal bond for THz driven
desorption:
Dynamics of thermally-excited reactions (THz frequencies on the order of kT)
Break bonds, reform bonds, controlling surface chemistry
Electron and positron bunches as a new means of molecular manipulation.
Requires GV/m fields
3. Magnetism research. Experiments with samples directly in beam and through
extracted THz fields.
-time-scales for magnetic switching
-Electric field manipulation of magnetic materials
-Damage mechanisms, electrical transport under high field conditions.
-Electron/positron switching enabling reset of dynamics for averaging mode experiments.
-Access dynamics through post-mortem analysis for different bunch time-delays
-MOKE for optical measurements…
THz emission studies through electro-optical sampling
4. Ferroelectric dynamics: Manipulation of polarization dynamics using intense fields.
Optical/THz probing
THz emission spectroscopy.
Parallel ideas to magnetic samples.
5. Strong field electron dynamics in bulk solids:
THz-driven high harmonic generation in solids.
Earlier work probing effects at 4 micron wavelengths in wide-band-gap semiconductors.
Need fields comparable to the atomic field.
Bloch oscillations.
Impact ionization.
Mapping of field-dependent band structure
Simple transmission measurements. Diagnostic: visible spectrometer.
Transient absorption measurements…
Diagnostics and other comments:
Spectrometers
Bolometer
Phase-locked oscillator (~10 fs) (and associated laser safety procedures)
Timing signals
THz beam splitters for pump-probe
Mass spectrometer
Known beam parameters (pulse duration, focus)
Adjustment of bunch duration, bunch current at fixed pulse duration.
Independently controllable electron and positron bunches with arbitrary separation?
What is the jitter between the two beams?
Extraction of THz from tunnel?
FACET vs. LCLS: positrons. Control of beam parameters. Access. Samples in beam. Insertion
of waveguide.
X-ray generation?
Single-cycle pulse isn’t always optimum:
Wave guides as a means of generating longer pulses but narrow band for resonant
excitation. Sub-cycle measurements possible so doesn’t compromise time resolution
-FLASH method