I thought my M462 2.2 Watt 462mn laser was bright in the night sky !

diachi said:

I believe they're definitely in the high 90s for the whole setup, but not quite 99.8% for the complete setup, i.e. both lenses together.



84mW loss at 7W input is 1.2%... Still tiny amounts of loss when you have that much power, but there's some math going wrong somewhere.

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paul1598419 said:

So, it's a matter of wishful thinking, or pride in ownership. Even good AR coated 3 element lenses have a loss of ~30% as apposed to a good AR coated single element aspherical lens. Every time you add lenses to correct for some problem you always induce losses into your output power. Add a BE and there are even more losses. The best way to know for sure is to measure the output with just the G-2 lens and then measure it again with whatever else you have added to it. One thing I can tell you for certain, your losses amount to much more than 0.2%.

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Mateusz
OptLasers Team manager
Opt Lasers
Tomorrow's System LTD

Efficiency is around 99,8% for 450-650

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badboybilly said:

We're all here to learn more, it was only 2 months ago when you asked this!

How is it being corrected, Can you explain this and what is being used a little more ?
__________________

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RedCowboy said:

I think you are making the small spot at 100 feet but losing power to clipping.

Ask this, would that size spot not burn better on your desktop at just a few feet?

The original sources divergence is always a factor, try this, hold a lens above a white sheet of paper between your overhead light and your desktop with the paper on it, you can adjust the distance to a multiple of the focal length of the lens and get a clear pic, so clear you can read the words on the bulbs.

Now move the paper half the distance from source to desk and focus it again, the image is smaller, if you cut a hole in your floor and focused it on your basement floor it would be bigger, a bigger image, a bigger spot.

A perfect focus getting all the energy should look like the emitter except we are bending the divergence of the aggressive axis.

With just a G2 the emitter image gets wider, a longer line with distance because light does not propagate evenly from our laser diode like it would a light bulb, one axis is very aggressive, but your 6X helps slow that down, still any spot containing all your energy minus only parasitic lens losses will be a rectangle/Bar/Line, a picture of the emitter with the highly divergent axis squeezed.


Anyway, the real test is to set a power meter at 100 feet and see how much power you are getting in your spot.

Your 10x BE needs wider lenses for its power, you should get a burning rectangle at your focal point, that's why I posted the burning bag video at 60 feet, notice with a G2 and 6X and a 3X BE how big my spot was and it took longer to ignite the bag, but the power was there, I think you are only seeing a round portion of the center of your true spot, the rest is clipped off into the walls of that 10X BE......If your input beam is 7mm wide it should exit at 70mm wide if 10X, but your lens is not that wide, so you can defocus and cheat it, but you lose distance that it can reproduce the full picture of the emitter.

That's what we see at a sharp focus, a picture of the emitter, it's not round.
You do squeeze one axis, but you have nothing to reshape it, no anamorphic lenses, your final focus at 100 feet should be a 5 watt rectangle, otherwise you are clipping out a round center spot, that's why the energy is missing.

Remember we are focusing an image of our diodes emitter, only 1 axis is slowed down but is still the fastest expanding axis, your spot has to be a rectangle or you are clipping unless you use something like anamorphic beam shaping.

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RedCowboy said:

Ok follow me here, your beam passes through the G2 and is fast axis corrected with a 6X pair then that 7mm beam enters your 10X expander that has a 30mm front lens also called an objective lens or output lens.

Also your input opening is only 5mm wide so your 7mm wide beam is clipped there to 5mm then that 5mm wide beam is expanded to 50mm and clipped to the center 30mm because that's all that can get out the front lens, the rest is hitting the walls inside the expander.

So you lose 2 of 7mm at the input that's what 27% roughly then you lose 20 of 50mm at the exit that's 40% of your remaining 73% so you have 60% of 73% of 6 watts, that's what ? 2 1/2 watts minus parasitic loss and any slight misalignment.

Seriously what does it look like when it's burning the wood at 100 feet, about 2 watts Right?

The real test is to use a power meter at the 100 foot mark or a known test media, a popsicle stick or a paper towel roll, something you know your 2.5 watt NDB7875 will ignite with the same size focal point on your desktop.


EDIT------

Ok I am looking at your output and it's not centered and it's the shape of round, the bottom half of the circle is just part of your beam, you can see how it fills the circle of your output aperture on the bottom half, what does the output lens look like?

It should be a line that stops before hitting the edges like this.

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RedCowboy said:

If you remove your 10X BE and aim your laser with G2 and 6X at the same plank of wood from the same place you will see a rectangle, at 100 feet maybe 1 inch by 5 inches or 1.25 x 7 something like that but what ever that rectangle is if properly focused through a 10x BE you should have a rectangle that is 1/10 as tall and 1/10 as wide.

You have what looks like a bite out of the bar, and these diodes naturally have a hot spot in the center of that bar, center of the dominant wavelength, or center of the bar. You can see it up close with a less than focused anything and G2 or 3E lens.

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RedCowboy said:

If the 10X BE had wider lenses for its power it would work fine, but it was geared more towards 532 size/divergence and only slightly bigger beams.

We need a bigger 3X maybe a 5X twice as wide. :beer:

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