How to Calculate Laser Diameter

How to Calculate Laser Diameter

Before calculating the laser diameter, we need to understand two expressions of beam quality - BPP and M2.

Beam quality is an important parameter of a laser. Two common expressions of laser beam quality are BPP and M2. BPP and M2 are based on the same physical concept, and they can be converted.

The reason why the laser beam quality is important is because it is a key physical quantity to judge whether the laser is good or not and whether laser precision machining can be performed. For many types of single-mode output lasers, high-quality lasers usually have high beam quality. Corresponding to a very small M2, such as 1.05 or 1.1. And the laser can maintain a good beam quality during its service life, and the M2 value remains unchanged. For laser precision machining, a laser beam with high beam quality is more conducive to shaping, so as to perform flat-top laser processing without damaging the substrate and without thermal effects. In actual use, when marking laser specifications, M2 is mostly used for fixed lasers and gas lasers, while BPP is mostly used for fiber lasers.

Now we can start the laser focus spot size calculation：FL/CL*fiber diameter=the oretical spot size.

FL=focus length;CL=collimation length

For BM109 version, you will get 0.0625mm beam spot.(125mm/100mm)*50um=0.08

0.08*2*1.5*100mm=24mm

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