Impact of laser-accelerated micron-size projectile on dense plasma

The impact of a laser-accelerated micron-size projectile on a dense plasma target is studied using two-dimensional particle-in-cell simulations. The projectile is first accelerated by an ultraintense laser. It then impinges on the dense plasma target and merges with the latter. Part of the kinetic energy of the laser-accelerated ions in the projectile is deposited in the fused target, and an extremely high concentration of plasma ions with a mean kinetic energy needed for fusion reaction is induced. The interaction is thus useful for laser-driven impact fusion and as a compact neutron source.

Core size scaling of helical-core optical fibres

The mode-area, scaling properties of helical-core optical fibres are numerically studied and the limit of core size for achievable single-mode operation is explored. By appropriate design, helical-core fibres can operate in a single mode with possible scaling up to 300 mu m in core diameter with numerical aperture 0.1.

Phase-shifting apodizer for next-generation digital versatile disk

The next generation digital versatile disk (DVD) using blue lasers will have a capacity of 13 to 15 Gbytes. Compared with current DVD, the wavelength will be shorter and the numerical aperture (NA) will be higher. But with the increase of NA and decrease of wave length, the depth of focus (DOF) decrease rapidly, which makes it hard for the servo-system to track. We propose an optimized three-portion phase-shifting apodizer to increase the depth of focus and at the same time minimize the spot size, which makes the DOF of next generation DVD comparable to current DVD. The simulation result shows that an optical system with this apodizer also has a good defocus characteristic. (C) 2001 Society of Photo-Optical Instrumentation Engineers.

Techniques for fabrication of large-size graded reflectivity mirrors

According to the parameter requirements of a graded reflectivity mirror with a Gaussian profile, the layer structure and the mask pattern are designed using a graded-thickness middle layer. The mask and the automatic mask-switchover equipment are designed considering the actual requirement of the thin films and the specific deposit facility. The uniformity of the layer thickness is analyzed. The measurement results indicate that samples prepared with this technique are basically in accordance with the design parameter. The scattering effect between the material molecules and the mask, thickness errors, and the alignment error between the mask and the substrate are the main factors that influence the deposit result. (c) 2008 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3027595]