New! Sharp Diodes 1W 520nm & 5W 455nm & +2W 638nm

[logsquared]

So, if I have a handle on this now, what is happening with a FAC lens placed uber close to the diode is the fast axis alone is collimated early (or partially collimated) to reduce the amount of fast axis beam spreading so it more closely matches the slow axis output?

For now, it appears to me what we do with a cylinder pair to square up a rectangle shaped beam to more closely approximate a rounded output is the opposite of what is happening when using a FAC lens close to the diode.

This is exactly right


Keep in mind what happens before the collimator lens affects what happens after in a inverse ratiometric way.

For example... Say the raw diode beam angle is reduced so the beam height when it hits the collimator lens is 1/2 what is was before, the FF spot will now be 2X bigger in that axis. This is true of any axis. Make the height where it hits the collimator 2X bigger and the FF of that axis is now 1/2.

This size ratio relationship is easily observed if we go from a 4mmEFL to an 8mmEFL. If no clipping occurs the laser dimensions at the lens will be 2x bigger in height and width with the 8mm lens (this is simple geometry of triangles). And as we know the 8mm will have 1/2 the FF dimensions.

Another thing to think about when trying to "square" MM diodes is the aspect ratio of the emitter. The ratio is usually much greater than the inverted ratio of the raw FA vs SA beam angle.

A rough example from memory: the m140 has roughly a 2um x 15um emitter, about a 1:7.5 ratio. This is what gives the bar shape in the FF. The FF "bar" has nothing to do with the raw divergence of the diode. The m140 raw FA is around 40deg and the SA is around say 10deg. We see that the ratio here is about 4:1. So, even if we manipulate the beam at aperture to be square the FF spot will not be square. To make the FF spot square we could increase the SA by 7.5X.

 

[CDBEAM777]

HMMMM....For the sake of my lifelong education....What axis are we manipulating with a FAC. lens ???????? Fast or Slow....Are we expanding/correcting the Slow Axis to achieve X=Y Aspect ratio....or are we reducing/correcting the Fast Axis to achieve X=Y Aspect ratio ???

Again....I believe Human eye sight Parallax view is the great " Band Aid" here.....for beam propagation as seen heading out to a great distance.....it all looks good. I do really not give a hoot what the beam geometry is in reality on the Lunar Surface....Again..the perception is truly much improved over reality.....Gaussian...or LD....at truly great Distances....Both spread to cover huge geometries....Sigh.....Interesting and educational discussions !!!....Like others.....I am hopeful the FAC units will deliver a much improved native beam profile to any Multimode LD.....specifically in the Mid Field....We will see !!! CDBeam

Added.….Hurmph ….See attached info from Hamamatso Optical concerning the function of a FAC lens !! Someone(s) earlier in this thread noted that the FAC acts upon the LD fast axis....thereby reducing its divergence....and therefore delivering an X=Y aspect ratio. Interesting !!!

IIRC....from past readings.....a FAC MUST be placed very, very close to the emitter.... for it to work. Ultra Micron positioning and subsequent fixing/attachment are used to accomplish the Fast Axis correction !! Well...That is what I remember anyway....SO....Cut me a lot of slack !!

As long as the FAC lens works !! Great !!! Makes my little Red Antenna go..." Beep, Beep...Beep "...At the end of the day....we just need X=Y....as close as possible !!

 

[RedCowboy]

The FAC won't have the leverage that a c-lens pair has, it has to do all it's going to do in a very small space so we will get improvement as DCBEAM777 said in the mid field but far field .......maybe not so much.

WARNING: LAYMANS TERMINOLOGY AHEAD .

I use a c-lens pair to act upon the more aggressively widening plane of light after a coli lens, by expanding then reducing the spread of the aggressive plane of light we do what would have taken more distance to achieve there by changing the angle of the divergence having gained leverage as I say it.

I call the more aggressively widening plane of light the fast axis.
CDBEAM777 and myself both know how to get the desired results I just explain it differently and admittedly likely wrongly however
the wide part of one axis vs. the narrow part of the other is the same thing so you can say expanding the slow axis but it's also expanding the more aggressively widening plane of light after the coli lens but it does flip over as far as what appears wide vs. narrow

If you take a NDB7475 focused to infinity and shine it onto a wall right in front of you while wearing your laser glasses you will see a bar, now as you walk backwards you will see it flip, what was narrow becomes wide and what was wide is now narrow, actually it's diverging on both axis just one faster than the other so the initial shape we see it the shape of the emitting region of which the narrow part has a wider emission and this is what's corrected.

 

[CDBEAM777]

The FAC won't have the leverage that a c-lens pair has, it has to do all it's going to do in a very small space so we will get improvement as DCBEAM777 said in the mid field but far field .......maybe not so much.

WARNING: LAYMANS TERMINOLOGY AHEAD .

I use a c-lens pair to act upon the more aggressively widening plane of light after a coli lens, by expanding then reducing the spread of the aggressive plane of light we do what would have taken more distance to achieve there by changing the angle of the divergence having gained leverage as I say it.

I call the more aggressively widening plane of light the fast axis.
CDBEAM777 and myself both know how to get the desired results I just explain it differently and admittedly likely wrongly however
the wide part of one axis vs. the narrow part of the other is the same thing so you can say expanding the slow axis but it's also expanding the more aggressively widening plane of light after the coli lens but it does flip over as far as what appears wide vs. narrow

If you take a NDB7475 focused to infinity and shine it onto a wall right in front of you while wearing your laser glasses you will see a bar, now as you walk backwards you will see it flip, what was narrow becomes wide and what was wide is now narrow, actually it's diverging on both axis just one faster than the other so the initial shape we see it the shape of the emitting region of which the narrow part has a wider emission and this is what's corrected.

This is a GREAT thread !! I am very glad to be a participant....and LEARN. I have NO formal Optical Training....but...I have worked to understand the fundamentals....and produce results...for years. I have shared my journeys....and always attempt to remain humble in my general approach...well...most times humble !!! hahaha

What any of us lack in formal training....we compensate for with a good degree of Passion and Curiosity….SO....what more can you ask for. This is the Internet !!! HAHAHAHA.... Who knows if our terminology is textbook correct....I do not care...I simply desire good results....and I have an ongoing desire and ability to somewhat share my travels with all you fine people !!

Thank you all !! CDBeam

 

[logsquared]

I suppose we could give up on all terminology and convention. Its way more fun that way. I'll give it a try. If we squash the tall unicorn with the eye of the eagle it will look much better when taking flight. If the path of the golden ray is long walked the health of the ray improved. Sorry couldn't resist

 

[RedCowboy]

It's ok I get it and also like to learn the correct terminology so I don't look like a buffoon while conversing and it is of course the right way to share knowledge and build on what we know and learn, but I have seen people quote from the online laser encyclopedia and get what it said completely backwards, others copy and paste definitions and miss the point completely.

 

[CDBEAM777]

Ya know...There is ONE....in every crowd !!!! HAHAHAHA.....Unicorn my ____ !!

Well...We struggle....and I am used to looking....well....Challenged !!! But...I just do not care.... I will attempt to use the correct nomenclature....just to be accurate in my sharing and gathering of knowledge.....But...I really do not care !!! If I make mistakes... Oh Well .But....as long as one consistently tries....that is the measure that is important !!

Anyway....we march onward.....ENJOY THE RIDE !!!! CDBeam

 

[Alaskan]

The one subject which can easily bite my back side is this one, a single FAC lens, FAC & SAC combined lenses, what happens where when, i.e. the geometry of the bar flipping in the distance etc. have all been subjects I've had to google and google doesn't have as much to say about these things as I would like. So, I'm learning from others in the forum too, they've already struggled with some of this themselves and can lend a helping hand up. Thanks, appreciate the info.

Edit: Bob, I've seen you post that photo before and liked it, today I adopted it as my avatar, for awhile. As you know, I change them every now and then With my open interest in UAP's, it is quite fitting for that too. Yes, I stole from your bag of humor Don't worry, I will return it after it is well used.

Edit 2: I just learned Laser Tree did not actually have the FAC corrected 525 nm 1 watt laser diodes ready to sell, they might take a week (I expect more) to add the FAC lenses to them. When I ordered them there was no statement on the listing in regard to this, only afterwards and they charged the DHL expedited shipping ahead of time as an additional invoice with no mention of the delay, only when I asked for a tracking number was it mentioned they did not have the completed diodes in stock to ship. The good news is there is no adverse affect to a timeline because the project they are going to be used for is still coming together for some of the other parts we need, but it sure would be nice to have them in hand to test.

Guys, I'm thinking of breaking into a sub hobby of FAC correcting diodes but I don't think I can do it as cheap as the Chinese, maybe better with AR coated D form PCX FAC lenses, but not cheaper, cannot compete with these prices but might be fun to try doing a few diodes for my own use. You can buy some very nice FAC lenses, almost a half inch length of it for about 160 dollars on EdmundOptics.com - Ouch. Good thing it doesn't take much to correct a diode, but I don't know if they can be snapped into smaller pieces or not while simple round fiber can.

 

[kecked]

If you do decide to fac diodes make really sure you use the right glue especially on the blue or violet diodes or that glue will yellow and crumble quickly. Also if you don’t do it in an inert and DRY ATMOSPHERE your toast. Even in a nitrogen glove box the blues where dying. It was not until I also had dry nitrogen also free of co2 etc...did they live. I also found solvents in the glovebox also made a difference. This is not an easy task

 

[logsquared]

Guys, I'm thinking of breaking into a sub hobby of FAC correcting diodes but I don't think I can do it as cheap as the Chinese, maybe better with AR coated D form PCX FAC lenses, but not cheaper, cannot compete with these prices but might be fun to try doing a few diodes for my own use. You can buy some very nice FAC lenses, almost a half inch length of it for about 160 dollars on EdmundOptics.com - Ouch. Good thing it doesn't take much to correct a diode, but I don't know if they can be snapped into smaller pieces or not while simple round fiber can.

This would be an awesome undertaking. Very challenging for DIY. Very worth while to try. Maybe start with red diodes for the reasons kecked noted above.

I do think it might be possible to mount longer FL (1-2)mm EO FAC lenses directly to the can of blue or green diodes. This could fully collimate the fast axis. Then only a PCX cylinder could be used for the slow axis collimation. If the can is not removed then we mitigate the fill problem.

Im thinking a 5 axis micro manipulator is in order for the alignment.

This should probably have a thread of its own. I could go on rambling for days with ideas.

I hope nobody was offended by my nomenclature joke. I was just joking around, or being a dick as my GF would say. Seriously though, none of us are optical engineers. If we are all on the same page its easier to communicate our ideas.

 

[Alaskan]

Quote

kecked: If you do decide to fac diodes make really sure you use the right glue especially on the blue or violet diodes or that glue will yellow and crumble quickly. Also if you don’t do it in an inert and DRY ATMOSPHERE your toast. Even in a nitrogen glove box the blues where dying. It was not until I also had dry nitrogen also free of co2 etc...did they live. I also found solvents in the glovebox also made a difference. This is not an easy task.

... 5 axis micro manipulator

I'm going to need to learn more about all of this!

Quote

logsquared: I do think it might be possible to mount longer FL (1-2)mm EO FAC lenses directly to the can of blue or green diodes.

I was wondering about whether this was possible too.

I will look into the idea, might be something which could lead to actually earning money on the side while retired in five years. I am 62, but my hands and fingers are 100% calm without any amount of shakes, my father at near this age could hardly hold his cigarette still to smoke it.

Anyone know of a source of visible spectrum AR coated round fibers or PCX FAC lenses which aren't as high priced as EO, or is that the low price source?

 

[kecked]

Well I’m not your guy for this. The more I play with lasers in the lab the less I find I really know Much of anything. Drawing pretty pictures on the wall does not make on a laser expert.

 

[Alaskan]

Googling micro manipulators, OMG.... I don't know which type I could use at minimal price, they sell from $$$.00 to $$,$$$.00. I imagine one could start out with something simple interfaced to a zoom stereo scope.

 

[logsquared]

Googling micro manipulators, OMG.... I don't know which type I could use at minimal price, they sell from $$$.00 to $$,$$$.00. I imagine one could start out with something simple interfaced to a zoom stereo scope.

I've been thinking about this. I am fairly confident I can build a manually operated jig that could do this. The part that scares me is how to place the tiny little glue droplets? UV glue for sure. But how to not make a mess of the lens, diode, etc? Stumped on that one.

 

[CDBEAM777]

Good luck Chris....It may be possible to Micro position with a minimal featured manipulator....but yes....How the Hell do ya fix the Fibre ???
HMMMmmm ???????????????? Another Micro Manipulator with a micro syringe...standing by to fix the Fibre Optic....DUNNO ????...SO...now we have 2 x $$$$$....for two Manipulators...My hair is on fire !!! CDBeam

 

[Alaskan]

Perhaps a low tech method for a low budget project, a very thin needle dipped into UV glue and great care dabbing the contact surfaces prior to placing the FAC. I bet the tip of a medical syringe would work, I bet Laser Tree isn't using a micro manipulator, it may not be needed for a simple glass fiber, it's the PCX FAC lenses which need a far more accurate placement and a higher investment in equipment.