Need some advice for my 1W 808nm laser build

[ReNNo]

There is 18mm space between diode and exit of the module.
And cylinder lens is only 1.6mm thick.

Why do you say it's that much difficult?
It's not crystal to adjust it that much precisely.

I only need FAC that will collect all light from the diode and direct it to aixiz lens.

 

[HIMNL9]

Yes, but you need to align it at least with the chip axis and the FL ..... this way

The cylinder lens must be aligned with the chip plane (horizontal as the chip on the support) for correct the fast axis, must be aligned with the center of the chip, for collect the maximum light and not deformate the output beam, must be, ofcourse, at the right distance, in this case 3mm from the chip surface, and parallel to the chip face ..... this is the better alignment.

If you have a 9mm diode, you can cut a piece of the lens long same as the diameter of the can (any optic shop or optometrist shop can help you cutting and grinding it for get the right shape and lenght, if you don't have the needed tools for work with glass), and using some spacers, align it on the top of the can until you get the better alignment, then glue on the can (on the metal, pay attention to not pour glue on the glass window) with few epoxy resin.

The only problem is the distance from the can and the aixiz lens holder, when all is inside the module ..... if it's too short, can cause problems in focusing the beam ..... anyway, the lens usually increase this distance a little bit, so maybe it's enough ..... but i don't have your same diode and module, so cannot make any test about this.

 

[ReNNo]

Thank for these tips.
I'll give cylinder lens a try.

I'll use some 3mm spacers and glue it to diode can and see what will I get.

 

[ReNNo]

@HIMNL9
Yeah, you are right...there is some space between diode chip and end of can.
It's better to try with 2mm spacers..
I have just ordered Cylinder lens from Surplusshed...

@Asherz
Yes...That is my problem.
And here you can see difference...

(left is light that goes out of module...right is light directly from diode)


(Distance from both diodes to white paper is the same)


And take a look at this picture..

Imagine that black circle as inside diameter of module.
It's 18mm from the diode (as distance from the diode to exit of module)
You can see that just part of light goes out of module. (or trough lens)

Cylinder lens should collect all light from diode and direct it to lens.

 

[ReNNo]

I got cylinder lens today.
And here are problems.

Cylinder lens is 3mm from diodes chip and I get focal point just few millimeters from cylinder lens. (That is what I want...all light can go trough lens)
After few centimeters I get thin line.
As on picture. (about 2 meters from diode)



If I put aixiz acrylic or glass lens in front of cylinder lens best that I can get looks like this...



No matter if lens is directly on acrylic lens or few millimeter away but I can not get focal point ...


What to do?

To buy new aspherical lens?

 

[MarioMaster]

It looks like you've mounted the lens incorrectly - it should be bringing that huge stripe to a square, not focusing the stripe to a line.

 

[ReNNo]

I did everything as HIMNL9 described.
But I'll try to play more with lens tomorrow.

 

[ReNNo]

Here is video of this cylinder lens and 9mm 808nm diode.

YouTube - Cylinder lens + 1W 808nm 9mm diode

It's possible to get something that looks like cube but I think that some light might not go trough cylinder lens. Maybe I can fix that if I adjust lens very, very accurately.

Should cylinder lens act like that?

 

[HIMNL9]

Wait, you say that you get the beam focused after the cylindrical lens only, at a certain distance ? (can't see the video, i only get error message)

This mean that this lens does not have a 3mm focus lenght, probably ..... i referred to this distance, cause i've seen it mentioned somewhere as FL, but maybe i'm wrong about this ?

if you want, try a thing ..... using only the cylindrical lens, try different distances, until you see the beam become like a small spot, almost square ..... this is the FL of the cylindrical lens (ofcourse, you need to keep it centered and aligned with the chip) ..... the axis of the lens must be parallel with the chip, ofcourse.

Maybe the problem is this one ..... if so, need to find a lens with a shorter FL ..... or use a more big focusing lens after the cylindrical one (but, before, need to find the FL of that cylindrical lens)

 

[ReNNo]

No.I can not get focused beam just with cylinder lens.

I think you can see video now....

To achieve square beam I need to put cylinder lens 3mm from diode.
Earlier I was trying to put lens closer to diode and then I got focused line.
I thought it is what I need.....now I know focused line is not what I need but square beam

Now I must test if all light can go trough cylinder lens because 3mm is not small distance from diode.
Beam from diode expands very fast and lens is just 3mm wide.

 

[HIMNL9]

Right that, yes ..... in the point where the beam become a square image, that is the right FL for correct the fast axis (probably there's a little bit of loss at the borders)

Diodes with integrated FAC lenses are more efficent than external FAC lenses, anyway, cause there the lens cover directly all the chip face, and the lenses are matched for this purpose.

 

[ReNNo]

All I want is the smallest spot at 15cm from laser for the best burning.
There is one more problem.
When I adjust cylinder lens to achieve square beam, will aixiz lens focus it to smallest spot at 15mm?
And what distance from cylinder lens and aixiz lens is needed for that purpose.

I'll test it tomorrow.

 

[ReNNo]

Today, I was trying to achieve square beam and then to focus that beam with AixiZ lens.

When flat side of cylinder lens is facing chip of the diode it's impossible to get square beam.
After I managed to get something that looks like square I tried to focus light with AixiZ lens but beam looked like line, not dot.

Then I tried to face cylindrical side of lens to chip of the diode and then I managed to get very clear square.
But it's very difficult to do without precise lens holders....these holder should be adjustable so I can move lens from diode very, very precisely.
But I don't have that tool and don't have access to CNC machine.
After I managed to get the most symmetrical rectangle I again used AixiZ lens to get the smallest spot, but spot was very big and there were wings around dot.

I don't plan to use this laser for high distances so I tried to focus it to 15 cm but then only that I can get is very thin line and then I can not burn.

Here is video that shows everything:

YouTube - Problem with cylinder lens and 9mm 808nm diode


Maybe that lens is not good for these diodes or I just can not get very good square without precise lens holders.

After unsuccessful testing of cylinder lens I tried to find any other optics that can solve my problem.

Then I found very thick glass lens with very long focal point.
Here is picture of this lens:



I tried to put this lens just on the window of the diode and then to use AixiZ lens to focus beam to smallest spot at about 15cm.

And it worked...I achieved very small spot (looks like very small line) and laser can burn very well.
Laser burns better if I use that thick glass lens because all light is collected.
With only AixiZ lens some light don't pass lens.

But I don't know if this lens is optimized for 808nm wavelength and don't know how much power I lose if light goes trough this lens.
I don't have LPM to test it.

After all I'm very confused.

Should I try something else with cylinder lens, or to use that lens that I found, or to find other solution?

 

[HIMNL9]

Well, if the lens also loose a bit, there's always a gain due to the fact that more light pass through the aixiz lens than without it, so imho it can worth the try

 

[HVDischarge]

I am currently trying to collimate my first multimode 1W 808nm diode. i have asked for help on other threads and got a few replies... i ordered this lens:

PRECISION PCX CYLINDRICAL LENS 25MMX6MM, 6.4MM FL - Surplus Shed

i now think that it is too small as it has a fl of 6.4mm and is only 6mm wide :-/. any ideas anyone? i actually popped the diode just after ordering this lens... so i now need another diode too! maybe i will upgrade to 2W...

 

[ReNNo]

Is there any way to buy aspherical lense with short FL.
Lens that has 2-3mm FL will be great.

Does it even exist?