ABSTRACT
We have developed a system of laser-pump and synchrotron radiation probe microdiffraction to investigate the phase-change process on a nanosecond time scale of Ge2Sb2Te5 film embedded in multi-layer structures, which corresponds to real optical recording media. The measurements were achieved by combining (i) the pump-laser system with a pulse width of 300 ps, (ii) a highly brilliant focused microbeam with wide peak-energy width (ΔE∕E ~ 2%) made by focusing helical undulator radiation without monochromatization, and (iii) a precise sample rotation stage to make repetitive measurements. We successfully detected a very weak time-resolved diffraction signal by using this system from 100-nm-thick Ge2Sb2Te5 phase-change layers. This enabled us to find the dependence of the crystal-amorphous phase change process of the Ge2Sb2Te5 layers on laser power.
ABSTRACT
The performance of a fast pixel array detector with a grid mask resolution enhancer has been demonstrated for X-ray photon correlation spectroscopy (XPCS) measurements to investigate fast dynamics on a microscopic scale. A detecting system, in which each pixel of a single-photon-counting pixel array detector, PILATUS, is covered by grid mask apertures, was constructed for XPCS measurements of silica nanoparticles in polymer melts. The experimental results are confirmed to be consistent by comparison with other independent experiments. By applying this method, XPCS measurements can be carried out by customizing the hole size of the grid mask to suit the experimental conditions, such as beam size, detector size and sample-to-detector distance.
ABSTRACT
Liquid crystalline molecules carrying photopolymerizable end groups absorb photon energy via a two-photon process, enabling the photofabrication of 3D structures. In this work, we prepared microgears with different heights and tooth lengths. These birefringent microgears can be induced to rotate by circularly polarized light. Here, we demonstrate that the use of phase plate for switching between left- and right-handed polarization reverses the optically induced rotation while maintaining the same rotational frequency. Due to the precise switching control, these birefringent microgears have advantages over previous microrotors that are fabricated from non-birefringent light-curing resins.
