J. H. Sung

Dependence of the electron beam parameters on the stability of laser propagation in a laser wakefield accelerator

Characteristics of electron beams produced by the laser wakefield acceleration are presented. The dependence of the electron beam parameters on the laser focal spot size is investigated. The experimental result shows the generation of quasimonoenergetic electron beam although the laser spot size was several times larger than the plasma wavelength. Stable electron beam generation at large laser spots was owing to the stable laser propagation in plasma channels. At a small laser spot, the beam quality is poor and this is attributed to the the filamentation instability of the laser beam.

Simultaneous generation of ions and high-order harmonics from thin conjugated polymer foil irradiated with ultrahigh contrast laser

We report the manufacturing of an (ultra-)thin foil target made of conjugated polymer, poly(9,9′-dioctylfluorene-co-benzothiadiazole) (F8BT), and the simultaneous observation of laser-accelerated ions and second harmonic radiation, when irradiated with ultrahigh-contrast laser pulse at a maximum intensity of 4u2009×u20091019u2009W/cm2. Maximum proton energy of 8 MeV is achieved along the target normal direction. Strong second harmonic with over 6% energy ratio compared to fundamental is emitted along the specular direction. Two-dimensional particle-in-cell simulations confirm the simultaneous generation of protons and high-order harmonics, which demonstrates the feasibility of applications requiring particle and radiation sources at once, effectively using the same laser and target.

Single-shot nanometer-scale holographic imaging with laser-driven x-ray laser

Single-shot nanometer-scale imaging techniques have become important because of their potential application in observing the structural dynamics of nanomaterials. We report here the image reconstruction results obtained using single-shot Fourier transform x-ray holography with an x-ray laser driven by a table top laser system. A minimum resolution of 87 nm was obtained from the reconstructed image. We could also discriminate the aggregates of carbon nanotubes, which shows the feasibility of single-exposure nanoimaging for real specimens using a laser-driven x-ray laser.

Characteristics of a Ni-like silver x-ray laser pumped by a single profiled laser pulse

We characterized a Ni-like silver soft x-ray laser realized as, what we believe is, a new variant of the grazing incidence pumping (GRIP) scheme. The x-ray laser was pumped by a single profiled laser pulse from a 10 Hz Ti:sapphire laser system. The Ni-like Ag x-ray laser was saturated with a gain coefficient of 76 cm−1 and an effective gain-length product of 28.2. The spatial characteristics of the new version of GRIP x-ray laser are presented including the far- and near-field beam profiles. Computational modeling of the lasing conditions was used to provide some qualitative explanations of the physical processes occurring in the x-ray laser. Additionally, we obtained some preliminary results on the injection seeding technique applied to the Ni-like Ag active medium using the 59th harmonic of the Ti:sapphire laser pulse as the seed. The single-pulse variant of the pumping scheme proved to be a stable and simple configuration of the table-top x-ray lasers also suitable for the injector-amplifier arrangement.

Dispersion and birefringence of irregularly microstructured fiber with an elliptic core

We have investigated the dispersion and birefringence of an irregularly microstructured fiber with an elliptic silica core and irregular airholes. The polarization-dependent output power through the fiber reveals two well-defined principal-axis modes despite the irregularity of airholes. The dispersion of the fiber is measured in the range of 680 to 1000 nm using the Mach-Zehnder interferometric technique with sub-10 fs laser pulses, which yield two zero dispersion wavelengths at 683 and 740 nm for the two principal modes, respectively. The birefringence measured using the wavelength scanning method is about 0.0055 at 800 nm. It is also demonstrated that this irregularly microstructured fiber with high birefringence and short zero dispersion wavelength is useful for the one-octave-spanning supercontinuum generation suitable for an f-2f interferometric system.

CO 2 Laser Assisted Fabrication of Micro-lensed Single-mode Optical Fiber

This paper reports the fabrication of various micro-lensed single-moden optical fibers through the use of an enhanced peak powern

Laser-driven electron beam acceleration and future application to compact light sources

CO_2

Radiography with Low Energy Protons Generated from Ultraintense Laser-plasma Interactions

laser beam. The end faces of the optical fibers aren exposed to the

On the Way Towards a High Repetition Rate X-Ray Laser

CO_2

Development of X-Ray Sources Using Intense Laser Pulses and Their Applications to X-Ray Microscopy

laser beam to form convex, concave, andn conical shape optical fiber tips. Peak power of the