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Why do diodes need lenses?

Soren

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Diode lasers and gas lasers work on the same principles, so why do diodes need lenses and gas lasers do not? Is it because the cavity is so short?
 

Cyparagon

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It's because the cavity is so thin.

We know that beam size is inversely proportional to divergence, so Imagine if you took a laser beam, and compressed the beam down to a few microns. The divergence would be pretty terrible. That's what a bare laser diode is.

As for the lens: the emitter is so small that you could consider it a point. You've probably seen this diagram:



Well, it works in reverse, too. Place the laser diode at the focal point of the lens, and bingo - proper laser beam.
 
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NoMercyFate

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Simple physics ;) You've got diverging lines and you want them to form a beam with aprallel lines so thats what the lens does, else its not much of a laser :p

Grtz
 

daawood123

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wait, about that reverse thing, does that mean if you screw a lens into a aixiz module in reverse, there will be a point where you will acheive fixed focus? i have tried so many time to get fixed focus with my LPC-826, but either the dot will be too large closer to the aperture or too big say 20ft away
 

lasergal

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