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udkm1Dsim toolbox
A Simulation Toolkit for
1D Ultrafast Dynamics
in Condensed Matter


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X-Ray Lab

 Plasma

Laser System

Laser Type: Oscillator 2-Stage Amplifier
Model: Coherent Mantis Coherent Legend Duo
Center Wavelength: 800 nm 800 nm
Bandwidth: 80 nm 30 nm
Pulse Duration: < 30 fs 40 fs
Pulse Energy: 5 nJ 8 mJ
Repetition Rate: 80 MHz 1 kHz

Plasma X-Ray Source

The laser-driven Plasma X-Ray Source (PXS) generates hard x-ray pulses (Cu Kα) with a duration of approx. 200 fs and a repetition rate of 1 kHz. In combination with a 7-axis Goniometer and a fast area detector (Pilatus 100k) the setup is an ideal tool to follow photo-induced structural dynamics in condensed matter. In addition, a closed-cycle cryostat allows for cooling various sample types down to 30 K and hence enables to investigate low-temperature phase transitions.

Rev. Sci. Instrum., 83:2(025104)

PXS Setup

Pictures of the PXS Setup

PXSPXS

Optical Transient Grating Setup

The optical excitation of ultrafast lattice dynamics is performed in wave vector selective transient grating arrangement. In particular, we impulsively stimulate phonon polaritons in selected ferroelectric dielectrics such as LiNbO3. We monitor spectral resolved transient dynamics via Impulsive Stimulated Raman Scattering (ISRS) and deduce phase and group velocity, as well as k-dependent optical phonon associated lateral damping rates. The phase mask based optical setup has a high interferometric stability and an effective phase tilted excitation advantages. We are thankful to Prof. K. A. Nelson from MIT supporting us with phase masks.

 BoxCarSetup

Time-Resolved THz Spectroscopy

Single-cycle THz Pulses with a center frequency of 2THz and spectral width of 2THz corresponding to a sub-picossecond temporal width (τP ≈ 0.5ps) are generated via difference-frequency mixing of femtosecond laserpulses in GaSe and detected with electro-optic sampling in ZnTe. Transmitted or reflected THz pulses from samples can be measured in time-domain to get the full complex dielectric function of the sample. The dielectric function ε(ω) is closely related/equivalent to the frequency dependent conductivity σ(ω). This is used to test the validity of several models of electrical conduction (e.g. Drude ...).

 

Setup THZ EOS
THz Generation and EOS Sampling


In addition, optical pump/ THz probe spectroscopy on semiconductors is performed to investigate the temporal evolution of optical induced conductivity with picosecond resolution. As a next step those experiments could be performed on solar cells.
Due to the fact that one gets the full dielectric function of the sample in the THz-regime one can also investigate transverse optical phonon resonances of several crystals (e.g. LiNbO3, BaTiO3, ...).

Setup THZ Pump Probe

Pictures of the THz Setup

therahertz