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Question about 9mm IR diode...

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Setarip

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Quick question about 9mm 808nm diodes...
Is the beam emitted similar to the diode bars or to lets say a phr's beam? I have two 2w 808 diodes and would greatly appreciate any info regarding the beam shape! Thanks!
 





They have a single chip (also if more large than a PHR), so the shape is basically the same of any other single diodes, not like a high power bar.

Except if you have a diode with integrated FAC, that gife you a better shape.

You can safely see the shape, directing it against a white (non reflective, a piece of polystirene is ok) surface, powering them at reduced power, and looking it through a camera, webcam or surveillance cam ..... they see IR too.
 
they emit a very wide rectangle of light, and can be hard to focus unless they have an internal FAC
 
If a high-powered multimode diode (like a 1W IR diode) doesn't have FAC (fast-axis collimation), you can use a cylindrical lens to perform the same function, but using an external lens will always increase the overall bulk of the assembly.

Here's what a FAC lens looks like on a c-mount:

308-fac1-zoomed-3.jpg


You can see that there is a piece of glass fiber glued across the face of the diode. This acts as a cylindrical lens to collimate the fast axis of the diode.
 
All multimode diodes emit a rectangular beam, yes. I've never seen a diode of any wavelength over 500mW that was single mode. Most diodes over 250mW are multimode.
 
Ah ok. Thanks for the help, I have two 2w diodes right now and trying to figure out what I want to do with them.
 
Hello, Ive just this second signed up to LPF, so i don't yet know all that much about lasers. i purchased a 9mm 1W 808nm LD off ebay, when i got it out the pack and powered it up, i noticed that the beam diverges or opens up quicker one way than it does the other, like a rectangular output. i have since discovered that it is a multimode diode (i have only ever owned "single mode"? diodes). can i buy any old FAC lens or does it have to be matched to my LD? and do i still have to use a "spherical"? lens as well? my knowledge of optics isnt great... incase you hadn't noticed :-(
Any help would be greatly appreciated :-).
 
If all you want to do with the 1W diode is make a burner, you can use an aixiz acrylic lens. Get it close to the diode face, and you will be able to get a burning point a few inches in front of the laser. You will not be able to produce a beam this way, with these multimode diodes you must correct the fast axis separately with a fac or cylinder lens, and then collimate. You would need to experiment with different lenses, viewing the results with a video camera so you can see the IR. FACs can be difficult to find, I don't often see them on ebay, for instance.
 
Thank you for the help :-).
i have got this burning with a normal glass AixiZ lens before but i wish to collimate the light. FAC lenses are not exactly cheap, i have seen a few of them on ebay everynow and then. i think the seller is a member of LPF too, "hesc-photonics" (from memory). i can't really offord to buy several and try them all out :-/. maybe its worth buying a diode that already has the FAC lens. do you know roughly how much a 80mW continous/ 240mW pulsed 650nm laser diode is worth (5.6mm, short closed-can)?
Thank you.
 
Try surplusshed for cylindric lenses ..... they have some cheap offer, if you just need to make some test

Anyway, yes, diodes with FAC lens are the better choice, they are already aligned
 
FAC is not needed in a green build. Just place crystals directly in front of diode. The optics would then come after the crystals. Usally a concave converging lens sitting directly on top of the crystals followed by a plano-convex lens to focus it.
 
I really hoped someone would say that. i watched a couple of videos on youtube and there appeared to be no FAC lens... that will make it cheaper, if i ever find some crystals that are within
my budget! whats the difference between nd:yag and nd:yvo4?
will this lens work to collimate the multimode diode?

PRECISION PCX CYLINDRICAL LENS 20MM X 12MM X 20MM FL - Surplus Shed

Thank you everyone for you help so far :D .
 
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