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: 18.10.2017
FS 2014: Seminare über Ultrafast Science and Technology
Thursday 11:15am
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
Änderungen und Korrekturen bitte an Franziska Stämpfli (IAP Sekretariat) melden!
 
Donnerstag, 20.02.2014

Software updates (internal discussions regarding the changes of the new semester)

Zeit: 10:15 Uhr
Hörsaal: B116
 
Fei Jia
Prof. Dr. Thomas Feurer
Institute of Applied Physics
University of Bern

 
Donnerstag, 27.02.2014

joint IAP and DCB seminar on Physical Chemistry

Spectroscopy of weakly-bound nanosized aerosol particles

Zeit: 11:15 Uhr
Hörsaal: S481 Freiestr.3
 
Prof. Dr. Ruth Signorell
Laboratory of Physical Chemistry, ETH Zürich
and
Dept. of Chemistry, University of British Columbia, Vancouver, Canada

 
Donnerstag, 06.03.2014

Presentations of Master's theses

Development of THz Time-Domain Spectroscopic Ellipsometer (Gregory Gäumann)

Cavity-Enhanced Generation of Energy-Time Entangled Photon Pairs (Manuel Unternährer)

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

 
Donnerstag, 13.03.2014

2 Micron and beyond – new fibers, sources and applications for the mid-IR

Zeit: 10:15 Uhr
Hörsaal: B116
 
Dr. Alexander Heidt
Optoelectronics Research Centre
University of Southampton, UK

The mid-infrared (mid-IR) spectral region at wavelengths of 2 micron and beyond is increasingly becoming the center of attention in photonics as it promises a multitude of exciting new applications – from “molecular fingerprinting” to high-intensity physics on timescales of attoseconds. In this talk I will review our latest progress and results in the development and application of novel optical fibers and light sources for the emerging mid-IR waveband.

At the heart of our approach are high power short- and ultrashort pulsed Thulium-doped fiber amplifier (TDFA) systems seeded by semiconductor laser diodes at 2 micron. The diode-seeding and the master oscillator power amplifier (MOPA) design allow for the construction of extremely versatile laser systems that can operate over wide ranges of peak power, pulse energy and repetition rate in the ultrashort picosecond to the long nanosecond pulsed regimes. We achieve a record peak power of 130 kW in picosecond mode, while demonstrating user-defined pulse-shaping capabilities at millijoule pulse energy levels in the nanosecond regime from essentially the same amplifier system. I will highlight recent results in the application of these MOPA systems and their high performance TDFA sub-components in such diverse application areas as next generation telecommunication networks, mid-IR supercontinuum generation and high sensitivity (sub-ppm) broadband spectroscopic gas sensing, using the latest generation of ultra-low-loss hollow-core photonic bandgap fibers, for environmental, security, and healthcare applications.

Finally, I will present novel fiber designs based on soft glasses such as tellurite and chalcogenide that allow the efficient generation of ultrashort pulses with the duration as short as a single cycle of the light field in the mid-IR, forming the basis of ultrafast fiber optics at this waveband with intriguing prospects for spectroscopy, bio-photonic imaging and material science.

 
Donnerstag, 20.03.2014

Non-linear THz spectroscopy on water

Zeit: 10:15 Uhr
Hörsaal: B116
 
Dr. Janne Savolainen
Department of Chemistry
University of Zurich

Two different approaches to non-linear THz spectroscopy are discussed. The fist one, optical pump THz probe, concerns the early-time dynamics of the initially delocalized excess electron in water. The second approach is a novel 2D Raman-THz spectroscopy that is used to interrogate intermolecular hydrogen-bonding network motions of liquid water (PNAS 110, 51, 20402,2013).

 
Donnerstag, 27.03.2014

Presentations of Master's theses

Beam shaping issues in a hybrid OPCPA/Nd:YLF laser amplifier chain (Christoph Bacher)


High Spatial Resolution Optical Time Domain Reflectometer
(Ali El Sayed)

Zeit: 10:15 Uhr
Hörsaal: B116
 
Christoph Bacher
Ali El Sayed
Institute of Applied Physics
University of Bern

 
Donnerstag, 03.04.2014

2D-VIS spectroscopy

Zeit: 10:15 Uhr
Hörsaal: B116
 
Yuseff Rodriguez
Institute of Applied Physics
University of Bern

Understanding nuclear and electronic dynamics of molecular systems has advanced considerably by probing their nonlinear response with suitable sequences of shaped pulses. The ability to control various features of the excitation pulses such as duration, sequence, frequency, polarization, and shapes has led to a variety of time-resolved spectroscopic methods. Among them, two dimensional electronic spectroscopy (2D-ES) with ultrashort pulses is becoming a more and more popular tool because it allows us accessing the third-order susceptibility of the investigated sample and getting information on molecular dynamics, line broadening mechanisms and quantum coherence phenomena in biology and molecular complexes in general. In our group it has been implemented a 2D ES set-up, which exploits the versatility of pulse-shaping methods to achieve a full control on the amplitude and phase of the exciting and probing pulses. In this talk, I will explain first the basics of 2D-ES also in comparison to other ultrafast experimental techniques like pump-probe. Then, with a special focusing on biological systems, I will discuss several experimental studies where 2D-ES lead to insightful and experimentally well-founded perspectives on intricate molecular population- and coherence-dynamics. From this discussion I will show the unique advantages that originate from using shaped pulses and several possible detection schemes where we take advantage of phase and amplitude modulations.

 
Donnerstag, 10.04.2014

joint IAP and DCB seminar on Physical Chemistry

Low-dimensional quantum magnets composed of strong hydrogen bonds

Zeit: 11:15 Uhr
Hörsaal: S481 Freiestr.3
 
CANCELLED / Prof. Dr. Jamie L. Manson
Eastern Washington University, Cheney, WA, USA

 
Dienstag, 15.04.2014

Quantum Information Processing with light carrying Orbital Angular Momentum

Zeit: 10:15 Uhr
Hörsaal: B77
 
Prof. Dr. Thomas Konrad
School of Physics
University of KwaZulu-Natal
Durban, ZA

We look at a few aspects of Quantum Information Processing and Communication (QIPC) with light carrying Orbital Angular Momentum, such as quantum teleportation of qudits, quantum key distribution and the transfer of entanglement through turbulent atmosphere. Moreover, we claim that there are applications of QIPC that can be implemented even with classical light.

 
Donnerstag, 17.04.2014

Harmonic nanoparticles for nonlinear imaging and DNA photo-interaction

Zeit: 10:15 Uhr
Hörsaal: B116
 
Dr. Luigi Bonacina
GAP Biophotonics
University of Geneva

The term harmonic nanoparticles designate a family of inorganic nanometric crystals (size < 100 nm) of different materials (KNbO3, BiFeO3, LiNbO3, KTP, …) sharing the characteristic of noncentrosymmetric structure. This property determines their large nonlinear optical efficiency, and, in fact, in the last years they have been mostly investigated as localized sources for second harmonic generation. After introducing this approach and comparing it with respect to other nanoparticles-based labelling strategies (quantum dots, upconversion NPs), I will highlight some recent applications in the field of (multi-photon) imaging and optical detection of biological samples together with NPs-mediated photo-interaction with cellular DNA.

L. Bonacina, Nonlinear Nanomedecine: Harmonic Nanoparticles toward Targeted Diagnosis and Therapy, Mol. Pharmaceutics, 10(3) 783-792 (2013)

D. Staedler et al., Deep UV generation and direct DNA photointeraction by harmonic nanoparticles in labelled samples, Nanoscale 6, 2929 (2014)

 
Donnerstag, 24.04.2014

It is water which matters: Observing the rattling modes of ions in the THz Range

Zeit: 10:15 Uhr
Hörsaal: B116
 
Prof. Dr. Martina Havenith
Laserspektroskopie & Biophotonik
Ruhr-Universität Bochum, DE

The details of ion hydration still raise fundamental questions relevant to a large variety of problems in chemistry and biology. The concept of water "structure breaking" and "structure making" by ions in aqueous solutions has been invoked to explain the Hofmeister series introduced over 100 years ago, which still provides the basis for the interpretation of experimental observations, in particular the stabilization/destabilization of biomolecules. Recent studies, using state-of-the-art experiments and molecular dynamics simulations, either challenge or support some key points of the structure maker/breaker concept, specifically regarding longranged ordering/disordering effects. Terahertz absorption spectroscopy in combination with molecular dynamics simulations is shown to be an important tool to study ion hydration. I will show the results for a series of aqueous solutions of divalent salts, which adds a new piece to the puzzle. The picture that emerges from the concentration dependence and assignment of the observed absorption features is one of a limited range of ion effects that is confined to the first solvation shell. For other salt, like lathanum we could show that the terahertz (THz) absorption spectrum allows to dissect the spectrum of the lanthanum with counter chloride and bromide ions in aqueous phase. When dissecting the spectrum we see the influence on cation due to counter anions ranges from self-confinement of both ions to solvent shared ion-pairing, with increasing salt concentration.

Reference: S. Funkner, G. Niehues, D.A. Schmidt, M. Heyden, G. Schwaab, K.M. Callahan, D.J. Tobias, M. Havenith Watching the low frequency motions in aqueous salt solutions – the terahertz vibrational signatures of hydrated ions JACS 134, 1030-1035 (2012).

 
Donnerstag, 01.05.2014

Ptychography

Zeit: 10:15 Uhr
Hörsaal: B116
 
Prof. Dr. Thomas Feurer
Institute of Applied Physics
University of Bern

Through dedicated measurements in the optical regime we demonstrate that ptychography can be applied to reconstruct complex valued object functions that vary with time from a sequence of spectral measurements. A probe pulse of approximately 1 ps duration, time delayed in increments of 0.25 ps is shown to recover dynamics on a ten times faster time scale with an experimental limit of approximately 5 fs. This opens up numerous new probing concepts in nonlinear spectroscopy or in the reconstruction of aperiodic objects with atomic scale spatial and temporal resolution.

 
Donnerstag, 08.05.2014

Comsol simulation of high field THz focusing

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

To facilitate nonlinear THz experiments it is essential to reach the highest possible focused intensities, i.e. the smallest possible spot size. The THz pulses are single-cycle pulses, therefore, they cover a rather large spectral bandwidth (100µm - 3000µm). This has two important consequences. First, the dimensions of the optical elements are comparable in size to the THz wavelengths and, second, any achromatic element will have a negative effect.

Through dedicated COMSOL simulations we investigate a number of important questions:

1) Is the paraxial approximation, e.g. Gaussian beams, still a useful description?

2) Can we assume an almost linear polarization in the focal plane?

3) What is the best focusing system given the different THz sources used in the lab?

4) Focusing versus imaging.

5) How careful do these systems have to be aligned?

 
Donnerstag, 15.05.2014

Laborbesuch

Zeit: 10:15 Uhr
Hörsaal: B116
 
METAS

 
Donnerstag, 22.05.2014

Presentation of Master's Thesis (Mehmet Oezdemir)
Raman Spectroscopy

Presentation of Bachelor's Thesis (Ramon Gfeller)
Detection of blood sugar

Zeit: 10:15 Uhr
Hörsaal: B116
 
Mehmet Oezdemir
Ramon Gfeller
Institute of Applied Physics
University of Bern

 
Donnerstag, 29.05.2014

public holiday (Ascension Day)

Zeit: 10:15 Uhr
Hörsaal: B116