定义：激光光束的直径（束腰处）与发散角的乘积。

激光光束的直径发散角乘积是在束腰处的光束直径（光束半径的2倍）与远场的光束发散角的乘积。直径发散角乘积越大，激光器光束质量越低。 
另一个更常用的量是光束参数乘积。

Definition: product of the diameter (at a beam waist) and the divergence angle of a laser beam

The diameter–divergence product of a laser beam is the product of the beam diameter (i.e. twice the beam radius) at the beam waist and the beam divergence angle in the far field. The higher the diameter–divergence product, the lower is the laser beam quality.

A more frequently used quantity is the beam parameter product.