There are matrix methods that can be used for propagating the diameter and curvature of the beam, but if your main interest is simply the location of the new focus (i.e. beam waist) or the size of the focal spot, you can use the Focal Spot Size Calculator tool on the Ophir website. Dr. Ivker Our expert – will explain you how
When focusing a laser, or anything for that matter, there’s a handy formula that is used to calculate the focus size and position.
It is generally called the thin lens formula, and it looks like this: