15 research outputs found
High-order Harmonic Generation from Noble Gas Clusters
At modest laser intensities atomic dipole moment is induced with the interaction of
light which creates a radiation. The emitted radiation contains low-order harmonics of the
laser frequency with exponentially decreasing intensity. At about 1013 W/cm2 light intensity
due to ionization processes high-order harmonics can also be generated approximately
with the same strength
Cluster size distributions in gas jets for different nozzle geometries
Cluster size distributions were investigated in case of different nozzle
geometries in argon and xenon using Rayleigh scattering diagnostics. Different
nozzle geometries result in different behaviour, therefore both spatial- and
temporal cluster size distributions were studied to obtain a well-characterized
cluster target. It is shown that the generally used Hagena scaling can result
in a significant deviation from the observed data and the behaviour cannot be
described by a single material condensation parameter. The results along with
the nanoplasma model applied to the data of previous high harmonic generation
experiments allow the independent measurement of cluster size and cluster
density.Comment: 7 pages, 6 figure
High harmonic generation on noble gas clusters
High order harmonics (HHG) were generated on noble gas cluster targets with
different cluster sizes. The independently characterized cluster sources enabled experimental
investigation of the recombination mechanism. HHG spectra were recorded for different backing
pressures and gases (Ar, Xe) as a function of driver pulse ellipticity. Since the ellipticity-dependent
HHG decay is essentially the same for the different gas-pressure pairs, we can conclude that the
recombination process is dominated by atom-to-itself recollisions irrespective of cluster size and
material
Laser particle acceleration technologies : probe laser beam diagnostics of extended plasmas
As plasma-based particle acceleration techniques are becoming intensely developed, the diagnostic tools for the study of the generation and properties of plasmas are increasingly important. We present results on the investigation of probe laser beam diagnostics for the measurement of the plasma density in extended spatial regions. Such extended plasmas are used in particle driven plasma wakefield acceleration experiments for the acceleration of electron/positron bunches to as high as TeV energies in the foreseeable future
The Effect of Femtosecond Laser Irradiation and Plasmon Field on the Degree of Conversion of a UDMA-TEGDMA Copolymer Nanocomposite Doped with Gold Nanorods
In this work, the effects of femtosecond laser irradiation and doping with plasmonic gold nanorods on the degree of conversion (DC) of a urethane dimethacrylate (UDMA)–triethylene glycol dimethacrylate (TEGDMA) nanocomposite were investigated. The UDMA-TEGDMA photopolymer was prepared in a 3:1 weight ratio and doped with dodecanethiol- (DDT) capped gold nanorods of 25 × 75 or 25 × 85 nm nominal diameter and length. It was found that the presence of the gold nanorods alone (without direct plasmonic excitation) can increase the DC of the photopolymer by 6–15%. This increase was found to be similar to what could be achieved with a control heat treatment of 30 min at 180 °C. It was also shown that femtosecond laser impulses (795 nm, 5 mJ pulse energy, 50 fs pulse length, 2.83 Jcm−2 fluence), applied after the photopolymerization under a standard dental curing lamp, can cause a 2–7% increase in the DC of undoped samples, even after thermal pre-treatment. The best DC values (12–15% increase) were obtained with combined nanorod doping and subsequent laser irradiation close to the plasmon resonance peak of the nanorods (760–800 nm), which proves that the excited plasmon field can directly facilitate double bond breakage (without thermoplasmonic effects due to the short pulse length) and increase the crosslink density independently from the initial photopolymerization process.publishedVersio
The Effect of Femtosecond Laser Irradiation and Plasmon Field on the Degree of Conversion of a UDMA-TEGDMA Copolymer Nanocomposite Doped with Gold Nanorods
In this work, the effects of femtosecond laser irradiation and doping with plasmonic gold nanorods on the degree of conversion (DC) of a urethane dimethacrylate (UDMA)–triethylene glycol dimethacrylate (TEGDMA) nanocomposite were investigated. The UDMA-TEGDMA photopolymer was prepared in a 3:1 weight ratio and doped with dodecanethiol- (DDT) capped gold nanorods of 25 × 75 or 25 × 85 nm nominal diameter and length. It was found that the presence of the gold nanorods alone (without direct plasmonic excitation) can increase the DC of the photopolymer by 6–15%. This increase was found to be similar to what could be achieved with a control heat treatment of 30 min at 180 °C. It was also shown that femtosecond laser impulses (795 nm, 5 mJ pulse energy, 50 fs pulse length, 2.83 Jcm−2 fluence), applied after the photopolymerization under a standard dental curing lamp, can cause a 2–7% increase in the DC of undoped samples, even after thermal pre-treatment. The best DC values (12–15% increase) were obtained with combined nanorod doping and subsequent laser irradiation close to the plasmon resonance peak of the nanorods (760–800 nm), which proves that the excited plasmon field can directly facilitate double bond breakage (without thermoplasmonic effects due to the short pulse length) and increase the crosslink density independently from the initial photopolymerization process
Measuring a Few-pulse Attotrain from CEP-dependent Relativistic High Harmonics
We present laser-waveform-dependent relativistic high harmonics from plasma surfaces, and use spectral interferometry to understand its generation process. The attotrain structure as well as the field-driven plasma surface motion during the process are revealed