C. Spielmann

Strong-field physics using lasers and relativistic heavy ions at the high-energy storage ring hesr at fair

The HESR high-energy ion storage ring at FAIR will provide unprecedented possibilities for strong-field physics using novel laser sources on relativistic heavy ions. An overview on the planning will be given.

Optimizing phase matching of high-order harmonic radiation in the range up to 1 keV

Phase matching is indispensible for the efficient generation high-order harmonic radiation (HHG), especially in the range of several-100-eV. Recently it has been theoretically predicted that perfect pressure induced phase matching cannot be realized in helium in the 0.2-1 keV spectral range using 800 nm light pulses. In this contribution, a detailed experimental study of the phase mismatch is presented for the first time and guidelines for maximizing the short wavelength signal without perfect phase matching are derived.

Tabletop lensless imaging apparatus using an ultrashort high harmonic XUV source

Optical microscopy has been a driving motor in science for several centuries. One main principle in microscopy is that the smallest resolvable detail in a microscopic image is limited to half the wavelength of the light illuminating the object. To overcome this limitation, the object should be illuminated with shorter wavelengths in the extreme ultra violet (XUV). The main problem in the XUV is the lack of efficient imaging optics and high absorption of solid matter. A possible solution for this is lenseless imaging [1]. Here we present our first experiments towards the realization of a table-top lenseless imaging microscope at 20nm wavelength, offering a spatial resolutions of a few tens of nanometers and a temporal resolution below 30fs. The 20nm light source is based on High Harmonic Generation (HHG) [2].

Determination of axial fluorophore distributions without strong focusing apertures using noncollinear optical parametric amplification

Measuring the lifetime and axially resolved fluorescence from the human retina opens the way for a new ophthalmologic diagnosis such as age-related macular degeneration. In this contribution we report on a new method to sample an axial fluorophore distribution by temporal gating of the fluorescence.

Strong field amplification of XUV: phase matching aspects

The dependence of the yield of high-order harmonic generation (HHG) on several important experimental parameters has been successfully modeled in the last 20 years by taking into account the single atom response and propagation effects. We extended this description by adding a stimulated emission process and named it x-ray parametric amplification (XPA). Beyond the super-quadratic increase of the XUV signal, which can be explained only in a limited pressure range by HHG theory, other observed characteristics like exponential growth, gain narrowing, strong blue-shift, beam divergence, etc. and their dependence on laser intensity and gas pressure can be explained accurately only by the new XPA model. We experimentally demonstrated XPA in Argon in the spectral range of 40-50 eV in excellent agreement with the theory. XPA holds the promise to realize a new class of bright x-ray sources for spectroscopy.

Laser driven parametric amplification in the xuv and soft-x-ray spectral range

We present the first experimental realization of a new x-ray laser scheme based on strong-field parametric amplification of high-order harmonic radiation. With a simple semi-classical model, we can identify the most important experimental parameters, the spectral range and the small signal gain in gases. Using a single amplifier stage a small signal gain of 8000 has been obtained in Argon for the spectral range of 40-50 eV, using 350 fs, 7 mJ pulses at 1.05 µm. In Helium, we observed a small signal gain of 280 around 300 eV using 6 fs, 1.5 mJ pulses at 800 nm.