Gaussian beam is a special kind of beam, which is different from spherical wave and plane wave of parallel beam emitted by point light source. Compared with the general beam, Gaussian beam has the following characteristics: the intensity distribution on the beam cross section is uneven; 1. 1 peak-valley beam characteristics: the wavefront is a plane perpendicular to the z axis, and the amplitude and phase of all points on the plane are the same.

The amplitude a has nothing to do with x and y, that is, the light intensity on the cross section perpendicular to the propagation direction of the beam is uniform. Features: The wavefront is a spherical surface with the spherical center as the point light source, and the phases of all points on the spherical surface are the same. The amplitude of each point on each sphere is A /r, and the light intensity of each point on the same sphere is uniform. . 1.3 Gaussian beam is a laser beam emitted by a laser with a stable resonator.

It is neither a uniform plane wave nor a uniform spherical wave, but a Gaussian spherical wave with varying amplitude and equal phase planes. Square mirror focal cavity: the field distribution on the mirror surface is Hermite-Gaussian function.

Properties of Gaussian beams: the intensity distribution will not change due to diffraction; W(z) gives the radius of the beam. What is the minimum value when z=0? This position is called the waist position of Gaussian beam, which corresponds to the classical focus. The radius of Gaussian beam is the distance from the maximum intensity to the cross section.