Laser beam through a lens

[PilotLaser]

Hi all, I'm trying to figure out the beam diameter after a certain distance using a focusing lens and I've found this website:

Focal Spot Size Calculator | Gaussian Laser Beams

Considering reliable the results from online calculator, here my doubt: the value of the beam waist in the laser company's datasheet is usually the beam diameter at aperture w or the actual beam waist diameter w0?

Thanks! :yh:

 

[Cyparagon]

Hi all, I'm trying to figure out the beam diameter after a certain distance using a focusing lens

For what purpose? Your answer will establish an acceptable error margin, and therefore a more appropriate method for evaluating things.

 

[Benm]

There is no difference between the beam waist and the width at the output aperture if a laser unit is set up with a diverging output pattern, as most fixed-focus types are.

With a variable focus system you can obviously create a waist in the beam at any distance from the laser you like. The size of that depends on the lasers emitting area, lens quality, distance from the laser and such.

This can be useful to know if you need a specific light intensity at a know distance from the laser, such as for engraving or laser cutting. If it's just for use as a pointer i reckon most units are rated for the performance when focussed at infinity.