Microwavephysics and Atmospheric Physics
Biomedizinische Photonik
Ultrafast Science and Technology
HS 2017  ·  FS 2017
HS 2016  ·  FS 2016
HS 2015  ·  FS 2015
HS 2014  ·  FS 2014
HS 2013  ·  FS 2013
HS 2012  ·  FS 2012
HS 2011  ·  FS 2011
Last update: 13.09.2017
FS 2013: Seminare über Ultrafast Science and Technology
Thursday 11:15am
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Donnerstag, 21.02.2013

Master thesis: Two photon-atom entanglement in a nonlinear cavity

Zeit: 10:15 Uhr
Hörsaal: B116
 
Maryam Akbarimoosavi
Institute of Applied Physics
University of Bern

 
Donnerstag, 28.02.2013

Hohlraum Target for Overcoming Refractive Losses in Plasma X-ray Lasers

Zeit: 10:15 Uhr
Hörsaal: B116
 
Leili Masoudnia
Institute of Applied Physics
University of Bern

Refractive losses along laser-produced plasmas used as gain media are caused by electron density gradients, and limit the transport range of energy. The pump pulse is thus deflected from the high gain region and also the short wavelength laser signal steers-away causing loss of collimation. A Hohlraum used as a target makes the plasma homogeneous and can mitigate refractive losses by means of wave-guiding. A computational study combining a hydro-code and an atomic-physics one is presented, which includes a ray tracing modeling of the trajectory-equation. This study presents gain calculations based on population inversion produced by free-electron collisions exciting bound electrons into metastable levels in the 3d94d1(J = 0)  3d94p1(J = 1) transition of Ni-like Sn. Further, the Hohlraum suggests a dramatic enhancement of the conversion efficiency of collisionally excited X-ray lasing for Ni-like Sn.

 
Donnerstag, 07.03.2013

High-performance and miniaturized atomic clocks based on laser-microwave double-resonance

Zeit: 10:15 Uhr
Hörsaal: B116
 
Dr. Christof Affolderbach
Université de Neuchâtel
Institut de physique
Laboratoire temps-fréquence
Neuchâtel

Today the definition of the SI second - and thus also official time scales such as UTC - are based on atomic units. Atomic frequency standards (or atomic clocks) realizing this principle have become indispensable parts of several of our civilisation’s modern technologies, such as e.g. high-speed telecommunication networks or satellite navigation systems. After a short introduction on atomic clocks, this presentation will discuss the principles of laser-microwave double-resonance spectroscopy in Rb vapour cells and its application to the realisation of novel types of compact Rb atomic clocks, as pursued in our group at Laboratoire Temps-Fréquence at University of Neuchâtel. Recent developments on high-performance Rb atomic clocks reaching nanosecond-level stability over one-day timescales will be presented, which are of interest e.g. for application in next generation satellite navigation systems. Work towards miniaturized Rb atomic clocks with the potential to maintain microsecond timing accuracy over several hours from a few cm3 size package will also be discussed. Such miniaturized clocks are of interest for emerging applications in network synchronization or mobile applications.

 
Donnerstag, 14.03.2013

Inter- and Intraconfigurational luminescence in hexafluorocryolite-type K3YF6 lattice

Zeit: 10:15 Uhr
Hörsaal: B116
 
Dr. Marek Gusowski
Institute of Applied Physics
University of Bern

The growing demand for brighter, faster, more efficient phosphors, scintillators and lasers which has lasted decades, has triggered the intensive studies of the wide-gap materials. Among them the fluorides have found the significant place and become an important field of research. They offer an excellent transparency in the range from infrared (IR) to ultraviolet (UV). It enables to record the absorption peaks attributed to RE3+ electronic transitions in the UV and even in the vacuum-UV (VUV) spectral region. They also give the opportunity to measure the luminescence from the 4fN-15d levels of rare earth ions after excitation with high energetic photons. In this seminar some results of the studies of the optically active rare earth ions placed in fluorides matrix will be presented.

 
Donnerstag, 21.03.2013

Critical aspects for nano-imaging in XUV Lab-scale Laser

Zeit: 10:15 Uhr
Hörsaal: B116
 
Mabel Ruiz Lopez
Institute of Applied Physics
University of Bern

Nano-imaging tools become more and more important in the field of nano-technology. Short-wavelength actinic microscopy provides resolutions down to tens of nanometers by using shorter wavelengths. In order to overcome this limitation, the BeAGLE enables coherent diffracted imaging as a coherent laser source. Achieving a reasonable illumination profile and stability is one of the main challenges for the short-wavelength microscope design. Measured results of pointing stability, divergence and coherence will be shown at this presentation.

 
Donnerstag, 28.03.2013

Engineering quantum photonic systems

Zeit: 10:15 Uhr
Hörsaal: B116
 
Dr. Rob Thew
Quantum Photonics and Quantum Communication Group
University of Geneva

Single photons, photon pair (spontaneous parametric down-conversion) sources and nonlinear interactions (sum-frequency and difference frequency generation) have provided key enabling technologies for quantum communication over the past 20 years or so. However, interest in these technologies is becoming more widespread as the complexity of these systems increases, i.e. for large scale quantum networks such as quantum repeaters and distributed computing or simulations, as well as for quantum metrology. I will focus on the experimental aspects of our work on engineering photonic states using these nonlinear interactions, in particular: for heralded photon sources, nonlinear interactions between single photons: how we can amplify single photon quantum states without violating the no-cloning theorem, and finally look at amplifying entangled quantum states into the macroscopic regime.

 
Donnerstag, 04.04.2013

Easter holiday

Zeit: 10:15 Uhr
Hörsaal: B116
 

 
Donnerstag, 18.04.2013

Master thesis: Cavity-enhanced generation of energy-entangled photon pairs

Zeit: 10:15 Uhr
Hörsaal: B116
 
Manuel Unternährer
Institute of Applied Physics
University of Bern

 
Donnerstag, 02.05.2013

Single shot detection and noise analysis

Zeit: 10:15 Uhr
Hörsaal: B116
 
Dr. Ariana Rondi
Institute of Applied Physics
University of Bern

Femtosecond pump-probe spectroscopy is a very powerful technique for the observation of ultrafast dynamical processes in molecules. In the last decades, the laser technology necessary for such experiments (femtosecond, broadband, high energy pulses) has become "off the shelf". While most pump-probe experiments aim at getting the best possible time resolution, a lot of efforts also go for obtaining the best signal to noise ratio (SNR), while maintaining a reasonable data accumulation time. Single-shot detection is a powerful approach for improving SNR, since it allows to correct for several important sources of noise, like intensity fluctuations of the laser, or mechanical instabilities of the experimental setup. We have developed a fast multichannel detection system for femtosecond pump-probe spectroscopy, capable of detecting single shot broadband spectra at the repetition rate of an amplified femtosecond laser system (kHz). I will present the measurements done to characterize the noise of our laser source. I will then describe our detection system, and the pump-probe experiments (transient absorption and broadband stimulated Raman spectroscopy) that we intend to conduct with this setup.

 
Donnerstag, 09.05.2013

public holiday (Ascension Day)

Zeit: 10:15 Uhr
Hörsaal: B116
 

 
Donnerstag, 16.05.2013

THz-driven streak camera based on giant field enhancement in split-ring resonators

Zeit: 10:15 Uhr
Hörsaal: B116
 
Justyna Fabianska
Institute of Applied Physics
University of Bern

Split-ring resonators (SRRs) featuring nano-gaps exhibit strong field enhancement in the gap region due to light-induced current flows and capacitive charging across the gap. The resonant behaviour of the SRR leads to narrowband amplification and results in significant field enhancement factors reaching values as high as 5000. This facilitates a large variety of THz strong field experiments even with modest THz sources. An interesting route to pursue is the manipulation of electron trajectories. Here, one particular application of SRRs in streak cameras will be presented. Streak cameras are known to be the fastest detectors to directly measure ultra-fast light phenomena. I will discuss a THz-driven streak camera, which, at least in simulations, shows the fastest response ever, namely around 1 fs.

 
Mittwoch, 22.05.2013

Lignosulfonate-Stabilized Nanoparticles: Properties and Applications

Zeit: 10:15 Uhr
Hörsaal: B116
 
Dr. Grzegorz Milczarek
Institute of Chemistry and Technical Electrochemistry
Poznan University of Technology
Poznan, Poland

The application of biorenewable materials in the design and development of advanced materials has been the area of rapidly increasing patent and literature activity. Lignosulfonates (LSs) are sulfonated derivatives of parent lignin which is the second (after cellulose) most abundant biopolymer found mainly in wood and grass. They are produced as by-products of chemical pulping of wood during making of paper. From the chemical structure point of view, lignosulfonates are easily oxidizable amphiphilic polymers showing surfactant properties. This makes them especially useful as stabilizing agents for nanoparticles. In this presentation, the chemical structure of lignin and lignosulfonates will be briefly discussed. More attention will be put on how LSs can be used in preparation of various nanoparticles such as: silver, gold, selenium and cyanometalates. The examples of applications presented will provide a brief overview of spectrophotometric chemical sensing based on silver and gold nanoparticles, Raman spectroscopy on nanostructured surfaces based on LS-stabilized silver and gold nanoparticles (SERS) and electrocatalysis with nanosized LS-stabilized transition metal hexacyanometalates.

 
Donnerstag, 23.05.2013

Terahertz Field Imaging and Spectroscopy (PhD Defense)

Zeit: 10:15 Uhr
Hörsaal: B7
 
Florian Enderli
Institute of Applied Physics
University of Bern

 
Freitag, 24.05.2013

From vacuum fluctuations of the electromagnetic field and continuum generation to versatile tunable femtosecond sources

Zeit: 10:15 Uhr
Hörsaal: B116
 
Prof. Eberhard Riedle
Ludwig-Maximilians-Universität
BioMolekulare Optik
Munich, Germany

Nonlinear optical conversion of femtosecond pulses is both of great interest from the fundamental point of view as well as a very versatile tool. In particular optical parametric amplifiers (OPA) allow the generation of tailored pulses from the deep UV to the middle IR. If the OPA is not even seeded by a weak signal, it still generates output light due to the amplification of the vacuum fluctuations of the electromagnetic field. We were recently able to "count" the modes of these fluctuations. Advanced OPAs rely on seeding with continua generated in bulk material. In the talk an overview will be given, how we generate pulses at any wavelength from 190 to 5000 nm. The continua not only allow the generation of pulses down to the 5 fs regime, but are also an unprecedented coherent light source for the probing of the ultrafast and not so fast dynamics and kinetics in physical and chemical processes.

 
Donnerstag, 30.05.2013

Master theses

Measuring the two dimensional refractive index profile of optical fibers by a reflection based method (Jonas Scheuner)

Invisibility cloaking at terahertz-frequencies (Yannik Waeber)

Zeit: 10:15 Uhr
Hörsaal: B116
 
Jonas Scheuner
Yannik Waeber
Institute of Applied Physics
University of Bern

 
Mittwoch, 31.07.2013

PhD defense: Optically Exited Metal Nanotip Cathodes for X-ray Free Electron Lasers

Zeit: 10:00 Uhr
Hörsaal: B7
 
Anna Mustonen
Paul Scherrer Institute PSI, Villigen
Institute of Applied Physics, Bern