计算聚焦激光束传输的非自适应坐标变换

非自适应坐标变换对于提高计算聚焦激光束传输问题的精度和速度非常有效．常用的非自适应坐标变换是以真空中高斯型聚焦束的传输特征为基础的．在这种坐标变换中，高斯束的形状、大小保持不变，但其它类型的聚焦束，如平顶分布等，焦点处光斑(在变换后的坐标系中)会变大，这会使光束与计算区域的边界发生碰撞而使计算失败．本文提出另外一种非自适应坐标变换，可以根据焦点处光斑的实际大小来调整计算网格的收缩(或放大)，从而避免光束与计算边界的碰撞．

Non-adaptive Transformation to Calculate the Propagation of the Focused Laser Beams

Non-adaptive transformations are effective in calculating the propagations of the focused laser beams. The usual non-adaptive transformation is based on the free-space propagation properties of the Gaussian beams. In this kind of transformation, the shape and the size of the Gaussian beam will be reserved, while the focused spot sizes of other kinds of beams, such as uniform wave, will increase with the increase of the focal length so that the beam will collide with the boundary of the calculation field. In this report a new kind of non-adaptive transformation is adopted in which the shrink of the calculation field will depend on the real size of the focused beams.