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Best way to collimate a fiber coupled laser
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Neviolograpy:
I have a laser diode, an array of diode at 808 nm, for a total power of 100W CW coming out with a multimode optical fiber (105 um fiber core, 0.22 NA).
I would like to use it for engraving, and I need to transform its output into a collimated beam of about 30 mm in diameter. :box:
I know these lasers are not made for the purpose, but for pumping Nd: YAG rods etc ...
Anyhow I wonder which is the best optical system.
The two solutions I found are the following, and I can't decide which of the two is the best, that is, it allows me to obtain an output beam with less divergence. |O
1. use a pre-assembled collimator (Edmud Optics, Thorlabs...) that comes out with a diameter of 2-3 mm, and in series build an ad hoc beam expander, for example a 10x with first aspherical lens of f = -50 mm and second spherical lens with f = 500 mm (therefore large focal lengths)
2. exploit the diverging beam exiting the optical fiber (0.22 NA = 25 ° full angle) and then use only one pcx condenser lens with NA 0.22-0.25 to collimate the beam (therefore f = 70-75 mm).
What is better in terms of output beam divergence and what costs me less in terms of the cost of optics?
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