Cleaning up beam through a hole

Greetings,

I'm building a 445nm laser (around 1-1.5W) using the standard Aixiz module and glass lens - and I was considering installing the module in a metal box and mounting it back a ways from the light opening, and having it shine through a hold (drilled in a heat sink) to tidy up the beam. Anyone ever tried this and was it worth the effort (I can see it being a bit of a pita to get it lined up nicely).

Ive seen it done in DPSS to clean up artifacts, but may not necessarily make
things better on a 445.

The divergence will not change, and you also may be adding more artifacts
to the beam with the glare produced by the beam reflecting off the inner surface
of the hole..

Try it out and see what you think. Most likely you will end up with a halo surrounding
the beam and a wider area of 'glare'.

Don't for get that the beam profile of a 445nm LD is
similar to this.... ==== by shining this beam through
a hole (besides possible added artifact pointed out by
wannaburn) your bean profile would like more like this...
==

That would suggest that you are loosing perhaps 50%
of the total output of your LD for a more X/Y proportional
beam.


Jerry

Ok I didn't realize it would be shaped so rectangular.

Is the noise from these 445 diodes typically bad like on a pen pointer?

What do your mean by "noise"...
Yes it makes a noise if you drop it.....:crackup::beer:

Jerry

Lol! My wife calls it the 'flower arrangement' around the outside of the beam spot, after expanding for a few meters. Looks like flare around the edge of the real beam spot.

Those are called artifacts that can be caused by a number
of different things.... dirt on the colimating lens... dirt on
the LD lens... reflections in the colimating lens assembly....
aberrations in the lenses themselves... etc...etc...

Jerry

lasersbee said:

That would suggest that you are loosing perhaps 50%....

Click to expand...

Quite true, and not a bad thing if a lower output is what you're going
for. I did exactly this on a pen build so that it did not exceed 5mW with
a a140 LD.

The aperture is approx 0.2mm and reduces the output while
the diode is running at a higher more stable current.

Even with such a tiny hole it doesnt do much other than mimic
a DPSS thin beam for the first few feet.

Wannaburn - your .2mm hole was how far from the diode - just after the lens? Wouldn't that act like a pinhole camera and keep the artifacts the same? What if it were moved 6 inches away?

I drilled the hole in a 10mm long piece of aluminum.. Im not sure if there
was any artifacts before hand, so I cant say if there was a 'better or worse'.

The idea was to make a stable (as possible) 5mW pen, but did note that there
was some glare added. ALso got a really tiny drill bit set, and have been dying to
use them for months

If you have the room to set it further, give it a try. With mine its on a pen, so no real
choice in the matter.

If that's the drill set where the box is the size of a quarter, I have the same! Came in useful once or twice.

I wonder if you could try this (I don't have my laser yet): Point at a wall say 50' away, and photograph the beam and artifacts. Now mount a jewel case black sheet 6 inches in front and let it burn through and stabilize, and then without moving it, go back and take another picture. I know this sounds cheesy but I think it would be very interesting to see if there is any improvement.

I have tried that as well as paper and other items. CNI actually uses
what looks like a small piece of soda can cut into a square, and placed
in the path of the 473nm labby beam on a few I repaired.

Have a look below at pic# 1, you can see the square piece with the hole,
and below that, the artifacts being stopped by it. Again this is DPSS and the
beam is thin and sharp before passing through the hole, but same idea.

Cool - thanks for the pics. Am I looking at this right - in pic #2, there looks to be a black circle on the RHS with a bunch of artifacts (4 big blobs of blue). Is that circle the hole you mean, or is it the tiny dot in the middle of the circle? Looks like the beam is very thin there.

Beautiful lasers, btw! I always like the laser systems over handhelds.

The black circle there is the exit aperture. All the blue you see around it are the artifacts. I removed the soda can square from mine since it really wasn't doing anything; all the artifacts mine generates are within the initial beam and only visible once it diverges out.

Sorry, I miss-typed.. In pic#1 shows the tin they used for the same
laser in pic# 2. Those blobs are what the tin was in place to remove.

In pic# 2 though, the tin is not in place, as it was attached to the plastic
cover seen in pic# 1 which was removed.

On other units, that tin was attached to the black metal where you can
see the 'blobs' of 473 around the beam. Most that had this, had the tin
in place on the AL, not on the plastic.

The laser in the pics is the CNI / B&W TEK 473 labbies found used on ebay
for good prices once in a while.

They're a nice little project laser and a nice colour :Beer:

BTW, pic#4 is a corrected 445 in the same housing. Its using the
anamorphic prism pair that comes in those 473 labbies to shape the 808.

Below is a pic of the corrected 445 seen in more detail.


@ Sigurthr If the artifacts cant be removed with the tin in place, try flipping
around the LBO crystal and re-aligning. You may lose some power, but I have
found this to be effective in cleaning up the output..