Knife Edging for Dummies (me... please help)....

[Alaskan]

I'm interested in laser knife edging but I can't seem to get a good grasp on the beam patterns which can be produced. Can someone take a look at this web page and help me understand what is being said?

https://lasertack.com/en/micro-knife-edging-/-beam-combiner-module

Here are the options for the diode patterns:

Following diode mounts are available:

•4x linear mount with a 4x1 dot shape *
•4x linear mount with different beam height for a 2x2 dot shape **
•3x L-Mount for a 2x1 or 3x1 dot shape ***

* available for 3,8mm, 5,6mm and 9mm laser diodes

** available for 3,8mm and 5,6mm laser diodes

*** available for 3,8mm, 5,6mm and 9mm laser diodes

However, I still don't quite understand them, does the asterisk show what the pattern will be? A single grouping for the first one which is more like a dot? How can it be a dot, I thought when knife edging you cannot place the outputs one on top of the other, only side by side.

 

[RB astro]

does the asterisk show what the pattern will be?

The asterisks on the top three lines denote which info (bottom three lines) they're referring to (available size LD).
One asterisk refers to the info below with one asterisk.
Two refers to the info below with two asterisks.
And so on.

So for example:
3x L-Mount for a 2x1 or 3x1 dot shape *** = *** available for 3,8mm, 5,6mm and 9mm laser diodes

 

[Alaskan]

Thank you for your help, but I'm still lost to understand what the patterns are between the two types of diode holders I'm interested in, in one type they are all in a row at the same height, another one has the diode holders staggered like this:

 

[RedCowboy]

Try firing a laser into a KE array backwards and adjust it until you get even beams, then you can see what you need to do in reverse.

You will not get a single beam out, you will get a stack of beams, so if you have rectangular multi mode beams, you want to stack them so they fit and then use a cylindrical lens pair on the output to stop if from diverging unevenly.

This 1 round beam in puts out 8 taller than wide slices. It looks like little green tall lines on the wall.

So to use it to combine 8 beams they go in like tall lines and then you use a cylindrical pair on the output that will look square to keep it square, otherwise 1 axis will diverge faster than the other.

LOOK AT THIS IMAGE
http://www.bing.com/images/search?q...9024524f926cd30b45651b78b57a3e2co0&ajaxhist=0
It depends on if you are using un corrected Multi Mode or single mode, with single mode you could edge 2 on 1 KE then 2 on another KE then those 2 lines of 2 on a third KE to make a box of 4, alignment is important.

 

[Alaskan]

I'd like to stack eight single mode diodes, that would be cool, if I can get the optics to square it up. Please check my thinking; the diode holders being in one line make a wide stack which can be squared up with a cylinder lens pair, but the diode holders which have the diodes at different levels stack them two X two, so you then have two stacks which should require less magnification from a cylinder pair to square them up, right?

What configuration for the diode holders do you believe would be better suited for wide beam expansion? That's what I'm really wanting.

 

[RedCowboy]

No because the cylindrical pair shape the beam by bending its divergence in 1 axis only, you would be better off to focus single mode laser beams with round lenses and if your beams are stacked in a rectangle of round beams then at least it stays a rectangle grouping of round beams.

The multi modes that stack as 8 lines will flip horizontal for vertical, just like any multimode diode you have, if you focus it to infinity with a 3 element or G2 it leaves the laser aperture wide in one plane but ends up wide in the other.

So if you knife edge to make a square out of lines you use the cylindrical pair to shape one axis only, the cylindrical pair only shapes one axis not both, and because without that cylindrical pair your stack of multi mode lines leaving the knife edger looking square will end up in the sky as an overlapping long line of lines, but squeezing that axis to start leaving the knife edger will prevent that, if the math is right, if not it will make at least better.

You would be better off putting your 8 single mode lasers focused to infinity in a circle all aimed into a cone and then use a beam expander to make it a circular cluster of beams. Or just a double concave near where all 8 beams collide then a doublet to hold that bundle size, but for serious distance you would go from wide ring to a distant point just like with your big lenses and a single beam.

I put some old pics on the 405 thread, you can see where I did it in the last pic

We have all seen this pic, I think this might be TechIngreedients, he has knife edged rows stacked into boxes, then lots of special filtering and cutting off the fray. You can see each row steps up so beam rows pass over to the telescope lens.

Here you can see what I mean by stacking rows into boxes in the lens reflection.

Pictures are worth a 1000 words huh? Note the one dead one on the bottom left, that explains it perfectly.
Needless to say this works best with 4 or 9 or 16 ..... as long as the single mode beams stay basically round.

 

[Alaskan]

Perhaps for my single mode diodes I will do that instead, form a ring output of several in a circle, if that is the best way to deliver a higher power low divergence spot, if the beams are expanded to at least 25mm/1 inch each. At distance, the divergence, although low, will eventually cause all of the beams to overlap and increase the net power. If you think that is the best solution for higher power at distance using diodes with 1um X 4um emitters, that's what I will probably end up doing then.

 

[RedCowboy]

It all depends on if you want to concentrate power on a leaf to zap it or produce a solid looking beam for a projector or just to look pretty, the ring focused to a point can start wide and end all on top of each other, just like you do with your expanders, just with a ring of beams instead of a wide single beam, same concept, but single mode is better at doing both, especially for our suburban line of sight distances.

Just like any laser, the tighter it leaves the device the harder it is to get a super concentrated spot at longer distances, a lot of lasers look like they end in a point, but we can't see it that well.

At 1000 yards at the end of our beam 24 inches or 1 inch looks the same to our naked eye. But if it's 24 1 watt lasers one will light the leaf and the other won't.

1000 yards is an extreme example, I just wanted to use a number that no one could debate. LOL

 

[VisibleGreen]

Wow I never thought to use right angle prisms for knife edging.

 

[Alaskan]

They are just first surface mirrors coated on right angle prisms, the prism function isn't used at all.

 

[VisibleGreen]

They are just first surface mirrors coated on right angle prisms, the prism function isn't used at all.

Probably to save on optical loss then?

 

[Alaskan]

I think they just made easy to mount first surface mirrors, none of the light travels through the glass at all, just reflects off of them.

 

[RedCowboy]

Both the red beam knife edging and stacking images above run the edged and stacked box of beams through that telescope at the end to shrink the box of beams. BUT THESE ARE SINGLE MODE.

Multi mode out of your hand held focused to infinity comes out wide but ends up tall as a rectangle, the emitter is wider than tall, but the vertical divergence is wider than the horizontal, it's just a wide output.

That creates this problem.

Now if we put the 4 knife edged beams through a cylindrical pair, we could rein in that highly divergent axis, not a perfect beam but more energy density and better looking.

 

[RedCowboy]

Thank you for your help, but I'm still lost to understand what the patterns are between the two types of diode holders I'm interested in, in one type they are all in a row at the same height, another one has the diode holders staggered like this:

For anyone who is curious this is a 2x2 stacker best for single mode.
It Knife edges 1 an 3 on the top and 2 and 4 on the bottom, so you get a box of 4 beams out, like the number 4 on a pair of dice, one die 4 beams in a square, then it's through a telescope like in the images above and you have 4 single mode beams all running in a nice little box that you could run through additional lenses to do what you want.
This would be nice for 4 BDR-209's , 3 watts in a tight beam would eclipse the range and ability of any MM diode and lens off the shelf.

 

[Alaskan]

Tempting me, I have like 8, maybe more, of the 800mw 405's waiting for a project.

 

[RedCowboy]

What I can't believe is how many people don't seem to care about putting corrective optics in front of their diodes, from 7875' to 44's

Granted there are a few and there's still reading I have not done, but even the 2x 3x that are readily available in front of a 7875 and then what lenses yield the best results.

I'm almost as lazy and I'm tight on the money right now, but it seems a lot of people with the means don't care.

I mean people like to talk about stuff they do, not all of it, I still have a secret or two, but I'm afraid a lot of people just don't care about any more than a bright flashlight or lighting a match at a few feet.

Where's the American ingenuity? Where are the droves of mad scientist building giant death rays? Are they all afraid to show it off, or they all preoccupied with the mess our world is in?

The 405's sound like fun, 100mw 405' used to be very expensive, now they are cheap, one day when digital media kills off Blu-ray hopefully I can grab up some cheap surplus before it becomes treasured, but who knows what the future holds.
Still it sounds like fun.

My arranging lasers in a cone to start with skips the need for the first lens, a big lens, the more lasers the wider, but aiming into a cone you skip that. The 2ns lens in this image needs not be so wide at all.
You can let your cone of lasers cross over and lens from there, many options, but having decent roundish beams to start with helps a lot.