摘要
讨论与M^2参数有关的一些问题。当采用光束二阶强度矩方法定义光束光斑大小和远场发散角时,M^2参数满足M^2≥1。但当改变其定义后,例如,采用86.5%(或其它百分比)功率通量法定义光束光斑大小和远场发散角时,由此定义的M^2参数(M_(pc)~2)的最小值是多少,什么样的光束具有最小的M^2参数(M_(pc)~2)。本文在采用86.5%(或其它百分比)功率通量法定义光束光斑大小和远场发散角的前提下,对这些问题进行了讨论。结果表明:共焦腔的输出光束应具有最小的M^2参数(M_(pc)~2);当采用86.5%功率通量法定义光束光斑大小和远场发散角时,M^2参数(M_(pc)~2)仍满足:M_(pc)~2≥1;但当采用其它百分比定义时,M^2参数(M_(pc)~2)有可能小于1,M_(pc)~2的大小取决于所定义的光斑半径内包含的光功率的百分数。
The problems concerning the M^2 factor are discussed. When the real-beam spot size and far-field divergence angle are defined by the second moments, it is pointed out that M^2≥1 holds. But when the premise of the definitions by the second moments is changed, what will happen？ For example, when the real-beam spot size and far-field divergence are defined by 86.5% （or other percentage） power content values, here what is the minimum of the defined M^2 factor （M^2pc）？ What kind of beam possesses the smallest M^2 factor （M^2pc）？ In this paper, these problems have been discussed, when the real beam spot size and farfield divergence are defined by 86.5 % （or other percentage） power content values. The results indicate that the output beam of the confocal cavity possesses the smallest M^2 factor （M^2pc）. When the real beam spot size and far-field divergence are defined by 86.5% power content values, it is pointed out that M^2pc≥1 holds all the same. But when the definition with other percentage of the beam power is introduced. The M^2 factor defined by the power content can be smaller than one, depending on the percentage of the enclosed power.
出处
《应用激光》
CSCD
北大核心
2009年第2期148-153,共6页
Applied Laser
关键词
激光光学
M^2参数
功率通量法
光束质量
laser optics
the M^2 factor
power content values method
beam quality
作者简介
通信作者：pfchen@mail．hust．edu．cn
