Why do I have wings?

Here's a cropped photo of the spot from my 6W NUBM44 laser diode expanded to about 2 inches diameter. Most of the power is concentrated in a dot at the center, but I also have these huge wings left and right of the spot, can anyone tell me why? I'm using a 2 inch OD PCX lens in an expander setup and don't know how to get rid of these wings.



I suppose I could simply put a mask over the output of my lens and cut them off before they can leave the lens, but I prefer an optic solution.

I think it's just the nature of the diode. Artifacts. Mass produced semiconductor lasers won't have perfect output like a lab laser such as a hene. If I'm wrong please let me know.

Look at the output in the picture in this post. See the differences?
http://laserpointerforums.com/f65/ndb7242e-diode-update-94986.html#post1378674

When I point this laser at a tree 500 feet away the wings are like 15 feet wide on the tree, I don't like to see them. I was hoping I was doing something wrong with my optics.

Yea, seems like wonkey reflections. Your expander lenses aren't coated, right? They are just from a generic camera lens iirc?

True, I will have some coated lenses to play with soon and see what they do.

Usually a sign of dirty or scratched lenses, or a reflection off the aperture in my experience.

Some lens may be on backwards.

It looks a lot like what happens when we over focus or focus past the perfect point, but I think it's because of the divergence being so much more aggressive on one axis than the other.

A Plano concave cylindrical lens used to rein in the aggressive axis before focusing through your lens set/expander would probably fix it.

That's what it seems like to me.

With the A series diode it was easy. The 44 is so much more divergent on the faster axis that it needs some beam shaping first.

Cylindrical lenses 445 nm - Opt Lasers

The lens on the left is what I'm talking about, this set is for the M and 7875 diodes, I am waiting for opt to offer about an 8x to 10x pair for the NUBM44.

Their pair for the 638 is coated for 400-700 so I'm not worried about the AR coating and the concave lens looks more like what the NUBM44 will need, but I would like the right prescription for the other axis as well, because one it contracts and the other it expands to make it closer to square, then our expanders will work as intended after a final focusing lens that produces a proper box shaped beam. So for me it's either try the 638 pair or wait for a NUBM44 pair.

p.s. opt also sells the bracket for mounting these in front of your S1/G2/G9

it looks like the lenses are oriented in a way that makes those wings. i've seen the same thing when collimating a laser with a lens that was backwards. i would recommend trying to flip the lenses, and try all the configurations you can until you get one that doesn't do this. your lenses may just not be compatible with each other for this set up.

IF they are produced by the lens system, not the diode itself, it can help to color the edges of the lenses black. This sounds rather silly, but in some situations it actually helps to blacked the outer, rough, edge of a lense with a sharpie or something similar.

Doing so is not likely to have any adverse effect even if it doesnt improve things, but if it does it can be quite easily be removed using isopropanol.

For my NUBM44 445nm laser, putting a single cylinder lens on the G2 expanded output prior to the collimation lens didn't work out for me, but having a PCX cylinder lens on the output of my NDG7475T 520nm laser diode (after the G2) and then replacing my expander lens on the end got rid of the wings, those two together made the difference.

I will keep working on the 445nm host, above, and try some of the suggestions, thanks!

Is that a powder white finish? :O

FireMyLaser said:

Some lens may be on backwards.

Click to expand...

Just what I was thinking. To elaborate:
The flat side of a lens should go to the side of the beam that is diverging/converging.
The curved side of a lens should go to the side of the beam that is parallel.

I've tried flipping the output lens, it makes a difference, but wings still there, maybe I will have a nicer beam if I flip that PCX cylinder around, will try that to see what it does for me, thanks! I bought this host 2nd hand, its a MrCrouse Zaser XL host but not sure if it's what is called a powder coat or not, but it sure is durable, maybe it is. The black tape is to fill the gap for a beam expander made out of a camera zoom focus mechanism I put over the end and just tape on, kind of ghetto but it works. It's the same one you see in the photo of the black Mace of Doom pointer (although the heat sink is buried inside, not a good place for it but it doesn't get too warm) I posted in the first post of this thread, I use it on two different pointers right now until I get another one: http://www.ebay.com/itm/New-2-inch-...-for-telescope-guider-Precision-/321444103013

As soon as I get my monster host from Ehgemus which uses 32650 batteries, I'm putting the NUBM44 6W 445nm diode in that host.

I have the other one if those sam was selling, remember? Anyway that's a convex, you are expanding the slow axis and you need to contract the very very divergent fast axis on the NUBM44.

Some people call fast and slow by distance of focus, but I call the faster diverging axis fast and the slower diverging axis slow, I may be saying it wrong, but the concave cylindrical will draw that rake of a beam back in.

Yea, I remember, just that the same PCX cylinder which worked well for the 1 watt 520nm NDG 7475T diode didn't work at all for the NUBM44, it's just too wide for it to work correctly the way I am using my beam expander with a de-focused G2 lens in front of it.