Smoothing the side lobes of a focused pattern by spectral dispersion in the broadband laser

Starting from the Huygens-Fresnel diffraction integral, the propagation equations of a broadband laser passing through a dispersive lens and a dispersive wedge are derived. Smoothing effect on the side lobes of the focused pattern is achieved as the broadband laser passes through the lens because of the spectral dispersion of the lens. By inserting a dispersive wedge behind the lens, better smoothing effect is realized because a relative position shift between focused patterns of different frequency components is generated due to the spectral dispersion of the wedge. Smoothing effect on the side lobe is obtained even with small bandwidth of the broadband laser as the wedge is used. (c) 2006 Elsevier GmbH. All rights reserved.

ICF中可调法布里-珀罗滤波器间距稳定度研究

在神光Ⅱ第9路ICF高功率激光装置中，采用可调法布里-珀罗（F-P）滤波器对幅度调制效应进行补偿，根据补偿装置的技术要求，提出-种应用nm量级精度的电容式位移传感器对可调F-P滤波器间距稳定度进行监控的系统，详细论述了监控系统的结构与工作原理。给出了电容式位移传感器的驱动电路及数据处理与控制软件的设计方案，并对电容式位移传感器的精度进行了标定。实验结果表明，该位移监控系统能够使可调F—P滤波器的间距稳定度保持在15nm／h以内，使幅度调制效应的调制深度优于4％。

Split-aperture laser pulse compressor design tolerant to alignment and line-density differences

We introduce a four-pass laser pulse compressor design based on two grating apertures with two gratings per aperture that is tolerant to some alignment errors and, importantly, to grating-to-grating period variations. Each half-beam samples each grating in a diamond-shaped compressor that is symmetric about a central bisecting plane. For any given grating, the two half-beams impinge on opposite sides of its surface normal. It is shown that the two split beams have no pointing difference from paired gratings with different periods. Furthermore, no phase shift between half-beams is incurred as long as the planes containing a grating line and the surface normal for each grating of the pair are parallel. For grating pairs satisfying this condition, gratings surfaces need not be on the same plane, as changes in the gap between the two can compensate to bring the beams back in phase. © 2008 Optical Society of America.

Natural cone formation for fast ignition of laser fusion

We propose to utilize the leading pulse of a petawatt class laser to create a conic plasma channel in the dense plasmas. This plasma channel could serve as a natural cone to guide the main pulse to the cone tip, as behaves similarly to the physical Au cone. We estimate that the leading pulse of a petawatt laser could create a natural cone with cone tip only about 100 mu m away from the edge of compressed core plasma. The natural cone formation should be compatible for a good uniform compression and efficient fast heating of the imploded fuel.

75 mW robust single frequency Yb-doped DFB fiber Bragg grating laser

Incorporating the shielded method and post-processing method, a 75 mW single frequency Yb-doped DFB fiber laser was obtained with a 250 mW laser diode pump source at 978 nm. The threshold of the laser is 2 mW. The laser is single-polarization operation and the output power fluctuation is less than 0.2 mW in one hour when the pump power is 250 mW.