Microwavephysics and Atmospheric Physics
Biomedizinische Photonik
Ultrafast Science and Technology
FS 2018  ·  HS 2017
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FS 2016  ·  HS 2015
FS 2015  ·  HS 2014
FS 2014  ·  HS 2013
FS 2013  ·  HS 2012
FS 2012  ·  HS 2011
Last update: 29.03.2018
FS 2018: Seminare über Ultrafast Science and Technology
Thursday 11:15am
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Freitag, 02.03.2018

PhD Defense: Long-Range Energy Transfer in DNA-Hosted Multichromophoric Systems by Ultrafast 1D and 2D fs UV-VisTransient Absorption Spectroscopy

Zeit: 14:00 Uhr
Hörsaal: B7
 
Maryam Nazari Haghighi Pashaki
Institute of Applied Physics
University of Bern

 
Donnerstag, 22.03.2018

Investigation of photoionization time delays in atomic and molecular targets

Zeit: 11:15 Uhr
Hörsaal: B116
 
Dr. Laura Cattaneo
Institute for Quantum Electronics, Ultrafast Laser Physics
ETH Zürich

The recent progress in the generation of ultra-short light pulses has enabled the determination of photoionization time delays with attosecond precision. The two dominating techniques used to investigate these electron dynamics are the attosecond streak camera or Streaking, and the reconstruction of attosecond beating by interference of two photon transitions or RABBITT. Both techniques are based on a pump-probe scheme, employing an extreme ultraviolet (XUV) single attosecond pulse (Streaking) or attosecond pulse train (RABBITT) as pump, and an infrared (IR) pulse as probe. Here it may arise the question whether the two methods give the same answer. I will first present a complete study, supported by both experiments and simulations, about the comparison of these two techniques when the photoemission time delay between valence electrons emitted from Ne2p and Ar3p ground states is investigated. To continue, I will show how to extend this type of investigation to more complex targets, such as molecules, identifying the key parameters involved in molecular photoionization reactions. In particular I will present the dissociative ionization of oriented H2 molecule, a fundamental case of study where the dynamics of the escaping electron wavepacket is influenced not only by electron correlation due to the presence of autoionizing states, but also by nuclear dynamics which takes place at comparable time scales as the electron dynamics. These experimental results are confirmed and complemented by a complete ab initio theoretical study incorporating not only the electronic, but also the nuclear coordinates in the description of the molecular wave function.

 
Montag, 26.03.2018

PhD Defense: Nonlocal Correlations in High-Dimensional Entangled Systems

Zeit: 15:15 Uhr
Hörsaal: 119
 
Sacha Schwarz
Institute of Applied Physics
University of Bern

 
Donnerstag, 29.03.2018

Master Thesis: Operation State Mapping and Self-optimization of Ultrashort Pulsed Fiber Lasers

Zeit: 11:15 Uhr
Hörsaal: B116
 
Christoph Lätt
Institute of Applied Physics
University of Bern

We present a highly versatile fiber ring laser based on the scheme of polarization additive pulse mode-locking. In this type of cavity, the laser oscillation state can be directly controlled by three waveplates. However, manually controlling and aligning such a cavity is very time-consuming because the parameter space is three-dimensional. In addition, the optimal adjustment trough temperature changes or mechanical perturbations of the fiber laser. To solve this problem, we have equipped our fiber ring laser with motorized waveplates and online monitoring. A software framework enables the automated measurement and creation of high-resolution 3D maps of different oscillation states by scanning through all waveplate positions. The high-resolution mapping allows a complete characterization of the cavity. In practice, however, it is desirable to be able to adjust the cavity to a desired operation condition within a short time. Therefore, we demonstrate the self-optimization of the fiber laser with a genetic algorithm in the direction of a desired oscillation state. This enables selective laser operation, e.g. in pulsed or continuous operation.

 
Donnerstag, 12.04.2018

Ptychographic reconstruction of XFEL pulses

Zeit: 11:15 Uhr
Hörsaal: B116
 
Tobias Schweizer
Institute of Applied Physics
University of Bern

In recent years the transfer of common spatial Ptychography algorithms to the time domain has gained a lot of interest in the scientific community. Time-domain Pytychography (TDP) has already been used by various groups to characterise fs laser pulses. In this talk, the application of TDP to the characterisation of FEL X-ray pulses is discussed. We will take a closer look at how TDP works and how it is applied to angular streaking data acquired at the LCLS free electron laser. Some simulations are presented as proof of concept, as well as some preliminary results obtained from the actual data. Towards the end of the presentation current challenges will be highlighted and discussed.

 
Freitag, 20.04.2018

Thulium Doped Fiber Laser Mode-locked by Graphene Saturable Absorber

Zeit: 11:15 Uhr
Hörsaal: B116
 
Sheida Mahmoodi
Institute of Applied Physics
University of Bern

Ultra-short pulsed fiber lasers in 2 micron wavelength range have many applications in medicine, material processing and free space sensing, which is why thulium-doped fiber lasers are of great interests for such purposes. In our work we investigate techniques for the generation of ultra-short pulses in 2 micron fiber lasers. To operate a fiber laser in the ultrashort-pulse regime, a saturable absorber that acts as an ultrafast optical modulator, must be introduced into the fiber laser cavity. There are various techniques for achieving saturable absorption and to mode-lock a fiber laser. In our current work we investigate two of these techniques. Namely the mode-locking by the technique of nonlinear polarization rotation and the mode-locking with Graphene layers. A software framework allows us to scan our setup that is equipped with motorized waveplates and to prepare a high resolution 3D map of the laser operation. With these maps we can compare in details the characteristics of different configurations of our fiber laser.

 
Donnerstag, 26.04.2018

PhD Defense: On Quantum Imaging with Time-Resolving Detector Arrays

Zeit: 11:15 Uhr
Hörsaal: B5
 
Manuel Unternährer
Institute of Applied Physics
University of Bern

 
Freitag, 27.04.2018

PhD defense: NIR pump/THz probe ellipsometry and nonlinear THz spectroscopy of VO2 and graphene

Zeit: 10:15 Uhr
Hörsaal: B5
 
Gregory Gäumann
Institute of Applied Physics
University of Bern

 
Donnerstag, 03.05.2018

Scientific opportunities and challenges for chemistry using X-ray Free Electron Lasers

Zeit: 11:15 Uhr
Hörsaal: B116
 
Dr. Wojciech Gawelda
European XFEL GmbH, Schenefeld, Germany

With the advent of soft- and hard X-ray Free Electron Lasers (XFEL) sources, entirely new scientific opportunities and prospects have been become available in the field of time-resolved X-ray spectroscopy and X-ray scattering. One of the most unprecedented features of XFELs is their ability to produce high intensity pulsed Xray pulse trains with single pulse duration well below 100 femtoseconds. This property allows dynamical studies of light-matter interactions virtually in any medium on the very fundamental timescales of interatomic motions, i.e. intra- and intermolecular vibrations, from gas-phase to complex molecular systems, i.e. biomolecules and proteins. In this talk I will present a state-of-the-art overview of the above mentioned research venues, with special emphasis on chemical dynamics studies, which highly benefit from the progress in the field of XFEL technology. In particular, I will focus on those aspects, which profit most from the temporal properties of the XFEL beams. Some very recent examples of early user experiments carried out at the European XFEL facility in the past few months will be presented and discussed.

 
Freitag, 04.05.2018

PhD Defense: From Theory to Application: Role of Numerical Simulations in Laser-Material Interaction and Laser Amplifier

Zeit: 11:15 Uhr
Hörsaal: B5
 
Yiming Zhang
Institute of Applied Physics
University of Bern

 
Donnerstag, 10.05.2018

No seminar (Ascension day)

Zeit: 11:15 Uhr
Hörsaal: B116
 

 
Donnerstag, 17.05.2018

NCCR MUST Site visit

Zeit: 11:15 Uhr
Hörsaal: B116
 

 
Donnerstag, 24.05.2018

tba

Zeit: 11:15 Uhr
Hörsaal: B116
 
Dr. Bernhard Lang
Institute ....
University of Geneva

 
Donnerstag, 31.05.2018

tba

Zeit: 11:15 Uhr
Hörsaal: B116
 
tba