证明了任何一个在真空中稳态传输的单色标量光束,在忽略了瞬逝波的条件下,其光束截面能量的径向分量E及轴向分量E||都与轴坐标无关,它们都为不变量;文中还进一步给出了光束能量衍射发散度的x、y分量的表达式。

We prove that, for any stable propagating monochromatic scalar beam in vacuum, the radial component E and the z component E of the beam cross-section energy are invariances and independent of the position of the cross- section if the evanescent waves of the plane-wave spectrum of the beam are ignored. The expressions of x and y component of beam energy diffraction divergence are derived.