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FrozenGate by Avery

Arctic Spyder 3 beam twist?

B

bbshamsa

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Joined
May 26, 2008
Messages
185
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Hi all.

Not sure if this has been mentioned before, but while trying to figure out the divergence of my Arctic, I noticed the beam profile seems to rotate by 90 degrees at about 2 metres from the aperture.

Probably a perfectly normal optical property I'm just not aware of, but interesting to me anyway.

Here's a clip...

... YouTube - Arctic Spyder 3 beam twist?
 





Pretty weird. Must be the focusing lens.

Regarding the focusing lens, does anybody make a superior lens that drops into the Arctic? Looks like the Aixiz module is threaded for and sized correctly. Preferably it would sit closer to the diode so that the initial beam diameter is smaller. Also maybe reduce the awful splash around the dot.
 
The fast axis and slow axis switch when passed through the collimating lens. It is normal.

@ haveblue
There are other lens options. Look for LarryDFW's Hi-power lenses and Jayrob's 405-G-1.
However, the divergence with these lenses is not as good as with the Aixiz lens that is already in there. Power increase will be about 15%.
 
You have a great demonstration here of slow axis divergence vs. fast axis divergence. It does not "twist."

The Arctic is threaded the same as the AixiZ modules. It will use any lens that will screw into an AixiZ module. I have not tried using a 405-G-1 lens to see if it can be screwed down far enough to get close enough to the diode, but it will "fit."

Peace,
dave
 
daguin said:
You have a great demonstration here of slow axis divergence vs. fast axis divergence. It does not "twist."

The Arctic is threaded the same as the AixiZ modules. It will use any lens that will screw into an AixiZ module. I have not tried using a 405-G-1 lens to see if it can be screwed down far enough to get close enough to the diode, but it will "fit."

Peace,
dave
Click to expand...

It will fit, but you can't use the factory supplied spring as the lens needs to almost sit on the diode. teflon tape is highly recommended. It has improved My dot, and bumped up the power out a bit.
 
When the beam is focused at "infinity," it actually does have a "waist."
However, with these multimode diodes, the beam goes from elliptical multimode bar, to a sort of square, then to a line.

The fast axis with no collimating lens is "vertical" to the diode (the transverse direction?).
When a collimating lens is used, the fast axis gets squashed and we end up with a horizontal line.
If the lens is adjusted closer to the diode, the orientation of the axes will go back to "normal" with the fast axis in the vertical direction.
So the "fast axis" we are seeing after the lens is actually the slow axis of the laser diode.

I'm no expert in optics or laser diodes, but what I think is happening, is that when the beam is focused for negative divergence, the axes are inverted. I noticed this with multimode 808nm diodes as well.

Edit: I can think of a better way to articulate this but I guess I'll leave it alone. Hopefully it makes sense.
 
Last edited:
It's right, and it's clear (IMHO). Somebody already successfully solved the problem ?
 
That is problem with every multimode 445nm diode and regular aixiz lens.
To fix that problem you probably need correction optics.
 
Another way to look at this is that each of the laser's axes has a different (virtual) focal point back a distance from the aperture. A collimating lens will produce a parallel beam when the focal point of the collimator is at the same point as the virtual focus of the laser.

Since the two axes have different focal points, a spherical lens can't be put in a position to focus both axes. You can correct for one axis, but the other will be over- or under-corrected, and will eventually diverge.

To properly focus such a source to a parallel beam, you need an optical system with different focal lengths in each axis. Typically, you'd do that with cylindrical lenses.
 
daguin said:
You have a great demonstration here of slow axis divergence vs. fast axis divergence. It does not "twist."

The Arctic is threaded the same as the AixiZ modules. It will use any lens that will screw into an AixiZ module. I have not tried using a 405-G-1 lens to see if it can be screwed down far enough to get close enough to the diode, but it will "fit."

Peace,
dave
Click to expand...

Thanks, and yes, "twist" was a poor choice of word.

I'd love to see someone apply corrective optics to one of these diodes.
 
bbshamsa said:
Thanks, and yes, "twist" was a poor choice of word.

I'd love to see someone apply corrective optics to one of these diodes.
Click to expand...

It's been done.
Dr. Lava offers a cylindrical lens kit that can be used to get a great beam.
 
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