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demystifying 808nm laser diode

Ethienne

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Hey everyone!

I'm pretty new to the world of lasers but i've been doing quite alot of research. I'd like to build a solid state laser based on 808nm laser diodes that would cut metal, say 1/4" thick, that would ultimately attach to a ShapeOko CNC.

Here is list of quesiton i'd like ansered I wou beleive you could help me:

1) I was searching on ebay for diodes and something has been confusing me.
I see stand alone 4w 808nm laser diodes with aperture for 120$ or so. Then I see 100W arrays of diodes for only 100$. Why is it that I get so much more lasing power for the same price?

2) Can I just use the laser beam coming out of these diodes to do the cutting job or will i need to pass them through a Nd-YAG bar ? In both cases, what kind of lense/mirror and else would I need?

3) Is there a good guide to build out own laser diode driver off of scraped electronic componenet, i'm sure I could build somthing for much less.

4) what does TO-5 TO-9 and etc mean? what about B-mount c-mount??

Thanks you very much for taking the time to help me out!

Have a great day.
 

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Besides the obvious difference between the diodes IE power out, when you power up the 4W diode it's going to cost you about $12.00 to $25.00 for the driver
but when you power up the 100W it's going to cost you $910.00 just for the driver and a tractor battery to power the driver is extra :crackup: actually I
think the driver is 120 or 240 volt input.

Also optics are much more expensive for high power laser applications.

But once you get all the hurdles tackled your going to have something that can most likely punch through 1/4" steel, who knows, some one dose :)

TO-5 and TO-92 are can size designation common in the electronics industry, Google it ! > http://en.wikipedia.org/wiki/TO-5

A "C" mount is a type of diode mount, do you know how to use Google ? here let me do it for you (laser diode C mount)>http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=5245

Good Luck :wave:



Hey everyone!

I'm pretty new to the world of lasers but i've been doing quite alot of research. I'd like to build a solid state laser based on 808nm laser diodes that would cut metal, say 1/4" thick, that would ultimately attach to a ShapeOko CNC.

Here is list of quesiton i'd like ansered I wou beleive you could help me:

1) I was searching on ebay for diodes and something has been confusing me.
I see stand alone 4w 808nm laser diodes with aperture for 120$ or so. Then I see 100W arrays of diodes for only 100$. Why is it that I get so much more lasing power for the same price?

2) Can I just use the laser beam coming out of these diodes to do the cutting job or will i need to pass them through a Nd-YAG bar ? In both cases, what kind of lense/mirror and else would I need?

3) Is there a good guide to build out own laser diode driver off of scraped electronic componenet, i'm sure I could build somthing for much less.

4) what does TO-5 TO-9 and etc mean? what about B-mount c-mount??

Thanks you very much for taking the time to help me out!

Have a great day.
 
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Meatball

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Hey there! Welcome to the Forum!

You ask some good questions. Let me give them a go for you, eh?

1) Those diodes are "multimode, single emitter" devices. The little chips are just that, a diode. A PN junction of some kind made from some magic rocks that glow in a special way. They cost just about as much to produce as the arrays cost. The arrays, are simply an array of diode stacked up next to each other, right? Not so difficult to fund its production. Price is not dependent on "lasing power". Mounting a high power "magic rock" doesn't usually cost much more or less than mounting 30-100 of them next to each other on a hunk of metal.

2) Generally, 808nm semiconductor lasers are terrible for precision marking, cutting, or engraving. Its not that it can't be done, its that its costly and rather difficult to tame the single (or sometimes dozens) of rectangular beams into something useful. Even after doing so, the energy density of the square does not match that of a DPSS, or gas laser.

The Nd:YAG crystal is used as a lasing medium which is pumped by 808 nm diodes in some cases. You're essentially going to end up building a lasing cavity, with the correct optics with the correct shape and coatings and with control of pump energy and thermal control. Its a mess of a system really. Lots of maths.

3) Define scrapped electronic equipment. How much would you be willing to spend on parts that builds a circuit that does what? You can build a 1.5A driver for $5 or a 50A driver for $30. Depends on your needs.

B-mount:


C-mount:


Just two different ways to mount the magic rocks. The C-mount takes a threaded bolt to secured the diode into position, as well as tightly lock it to a heat-sinking surface.

TO-5 is a 9mm package with a large window, and the T0-9 is similar is size except the output window is tiny.

^^ Those two packages compared to the standard, smaller, T0-56 package

Again, just another set of kickstands for the magic rocks to sit on.


EDIT: Bah Jeff! You've foiled me again!
 
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Ethienne

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Thanks for the detailed feedback! you guys are awesome. lol meatball:
A PN junction of some kind made from some magic rocks that glow in a special way
And sorry for not googl-ing it you're right it would of been a simple search.

Alright so If I conclude well, I'm better off to build a laser from a Nd:YAG rod because, although I will loose efficiency, the outputted laser will be of better quality and I will require less expensive optics in order to cut?

So, lets say I buy a optical cavity and Nd:YAG rod combo from ebay for 200$, would it be a reasonable project to revamp it so that I can use a 100W 808nm diode array for 100$ as a pump?

Also, for the power supply, I dont really understand the high prices...I mean ( and please tell me if im guetting this wrong) All we need to do is somehow convert 60Hz 120v ( canada) signal from a wall outlet to get a continuous steady 2.2v 110 A signal right ( for the diode array)? I've seen people use microwave parts and other electronic componenet to build drivers so I'm guessing it's possible to build one at a reasonable price. If you could give me some pointers on good stuff ( electronics) to look for and good references ( other similar projects) please let me know!

As for optics, that, I know very little about. What optics ( part bumber? type of lense?) do I need to have after the beam exits the optical cavity?

on a side note: The reason why i'm not using a CO2 laser is that lower wavelength are apparently better for cutting metal.

Thanks!

Ethienne.
 
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MarioMaster

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Unfortunately you will probably want to abandon this project unless you want to do it for an educational experience.

100W of 808nm will not cut metal, not even aluminum foil. The beam will be reflected. While lower wavelengths can be better for cutting, this generally only applies once you get below about 400nm.

Metal cutting (especially for say 1/4" aluminum or steel) will likely require a CO2 laser in the 500+W range. A video I found on youtube claimed maximum 2mm cutting depth for steel using a 150W CO2 laser.

You need much more power for metal, the focal point of the laser must reach the melting point of the metal for the air or oxygen assist system to blow the molten material out of the cutting area.
 

Meatball

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"You need much more power for metal, the focal point of the laser must reach the melting point of the metal for the air or oxygen assist system to blow the molten material out of the cutting area."
^^
Yes. And it must be able to do so very quickly. This ensures the material surrounding the cut is largely unaffected at all.


^^If you look at the edges of the material he poked hole in (in the video), you can see that the edges of the output are definitely not hot enough to cleanly process the material without distoring it shape and color - it spends too much time heating the material rather than cutting it. This is why the beam quality is so important.

I'm sure 100W of 808nm can do damage to various metals if you have it all fiber coupled, but can it match the performance of a YAG or Co2 setup with better quality, higher speed, and similar cost?

Just like our little 2W laser diodes can burn holes in paper, wood, fabric and whatnot - while at the same time not being suitable for materials processing of those same materials.

It seems that you aim to build a YAG. Its seems the best thing to point you to is "the book".
Sam's Laser FAQ - Preface, Introduction, What is a Laser?, Safety

After reading the section on laser safety, amateur laser construction safety, the section on DIY YAG, and YAG power supplies, you may find the project quite daunting for someone that knows very little about optics.

I highly recommend finding a ready made solution, unless you ready to learn more than your physics professor ever taught you in two semesters.

Eg: The cavity you linked to is for a flashlamp - pumped YAG. Diode pumping chambers are much less "standardized" in their design since diodes and diode pumping methods vary to a large degree.

The only successful DIY DPSS attempt I've ever seen was done by two of the more brilliant (and wealthy) gentlemen on the laser show forum.
 

Ethienne

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Again, Thanks for the feedback! I'll definitely have a look at "the book" . Nice video! I realized that, being a student at university, I had access to TONS of experiment reports on lasers and I found a couple of interesting ones I though you might want to have a look at... ( I don't know if infringing copy right but whatever -_-)

sorry I don't have the figures...

The doubly-pumped design depicted
in Fig. 1 is a confocal-to-concentric remnator
that is highly insensitive to misalignment
or pump power variation. The
cavity length of this resonator is about 70
cm. Output powers as high as 11 W with
M^2 ~ 1.1 are obtained for a total pump
power from the fiber bundles of 32 W.
This conversion efficiency is 34%, Figure
2 depicts the TEMoo output power as
a function of Q-switched repetition rate
for 32 W of total pump power and for 26
W of total pump power. The lower pump
power (26 W total) is consistent with a
diode operating point that has been derated
for increased diode lifetime.
In conclusion, we have demonstrated
diode-bmpumped NdYAG laser remnators
with 11 W of polarized TEMoo,
mode output power, both in cw and Qswitched
modes. High optical efficiencies
were achieved for fundamental mode operation
in spite of the presence of large,
pump-induced, nonparabolic phase aberrations
and the presence of thermal
birefringence. The high efficiency allows
deration of the diode pump sources in order
to meet the lifetime requirements of
industrial applicatioris.
-Nighan, W.L., Jr.; Hutchinson, S.B.; Dudley, D.; Keirstead, M.S., "Highly efficient, diode-bar-end-pumped Q-switched Nd:YAG laser with 11 W TEM/sub 00/ output," Lasers and Electro-Optics, 1996. CLEO '96., Summaries of papers presented at the Conference on , vol., no., pp.320,321, 2-7 June 1996-

Also:
Figure 2 shows an experimental setup of a
diode pumped NdYAG laser amplifier system.
The oscillator produces a maximum output pow-
er of llOW at the beam quality of M^2 = 1.1 with
575 W total pump LD output power. Details of
the laser performance of the oscillator are going
to be reported elsewhere. The amplifier consists
of two pump heads and a 90 degrees polarization
rotator. The amplifier was designed to achieve
polarization dependent bifocusing compensa-
tion.*
Figure 3 shows 1064-nm average output pow-
er of the amplifier system as a function of ampli-
fier pump LD output power. A maximum output
power of 206 W was obtained at the beam quali-
ty of M^2 = 1.34 with 800 W amplifier pump LD
power.
- Konno, S.; Fujikawa, Shuichi; Yasui, K., "200 W continuous-wave TEM00 mode 1064-nm beam generation by a laser-diode-pumped Nd:YAG laser amplifier," Lasers and Electro-Optics, 2001. CLEO '01. Technical Digest. Summaries of papers presented at the Conference on , vol., no., pp.420,421, 2001

So from what I've been reading W^2 as close to 1 as possible means the beam is Uber good quality and easily focus-able. So now I know that the beam coming out of a Nd:Yad diode pumped array is definitely of good quality.

You're right for the cavity I couldn't really use that..Also, I realize that I may not need a cavity if I get a properly coated YAG that allows for TIR ( total internal reflection) confinement. As for the learning curve don't worry, if i'm passionate about something I'll find the patience to learn what I need. Also, I am definitely doing this to learn as well.

Found that too as an assessment that Nd:YAG lasers are used in cutting aircraft aluminium:

Pulsed laser sources are extensively used in recent years for micro-processing of composite materials for structuring and patterning of surfaces. Alumina-aluminium (Al2O2-Al) Interpenetrating Phase Composites (IPCs) have increasingly widened their use in structural application in aircraft and space stations owing to their superior qualities. In this research, pulsed Nd:YAG laser micro-cutting on alumina-aluminium IPC have been carried out to investigate the influence of laser machining parameters such as lamp current, Q-switched pulse frequency and cutting speed on surface roughness. Response Surface Methodology (RSM) based optimal parametric analysis has been performed for achieving minimum surface roughness (Ra) of the micro-cut surface. Copyright © 2008, Inderscience Publishers.(16 refs)
- Influence of machining parameters on surface roughness in Nd:YAG laser micro-cutting of alumina-aluminium interpenetrating phase composite
Biswas, Ranjib1 ; Kuar, Aruna Shu2 ; Mitra, Souren2 , International Journal of Surface Science and Engineering, v 2, n 3-4, p 252-264, 2008;

Would you mind posting a link to the project of these
two of the more brilliant (and wealthy) gentlemen?
Alright, Well I'm gonna focus on finals for the next two weeks and if I indeed do end up doing this project over the summer I'll keep you guys updated. I'm sure its doable within a budget of 400$, it'll be a good engineering challenge =)

Thanks.

Ethienne.
 
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MarioMaster

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Fiber coupling dramatically increases beam quality and attainable power density at the focal point. Results are still poor and significantly more power would be needed to cut 1/4" metal.

OP was referring to the cheap diode bars that emit a wide stripe anyway.
 

Ethienne

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Fiber coupling dramatically increases beam quality and attainable power density at the focal point. Results are still poor and significantly more power would be needed to cut 1/4" metal.

OP was referring to the cheap diode bars that emit a wide stripe anyway.
Hi MarioMaster, As I mentioned, after discussion, I dont intend to cut with a 808nm diode. I will be using a 1064nm wavelength emitted by a Nd:YAG rod that will be pumped by the 808nm diod array. So this video is not representative of a cut made by a Nd:YAG laser. here is a video that i closer to my project:

http://www.youtube.com/watch?v=bexQ2esojkc


I dont understand your skeptisism, here is video detailing the awesomeness of 1064nm metal cutting :lasergun: ( I do realise ill probably need closer 200-300W of diode pumping power though):

http://www.youtube.com/watch?v=3dy4qhUqxh4
 
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Fiber coupling dramatically increases beam quality and attainable power density at the focal point. Results are still poor and significantly more power would be needed to cut 1/4" metal.

OP was referring to the cheap diode bars that emit a wide stripe anyway.
Understood, but why claim that 100W of 808nm could not cut foil? or any metal
for that matter? Too shiny? Those are false statements.

This is 15W cutting through a highly reflective 0.2mm stainless steel:


Besides, who uses any laser without optics? 60W 808 can also etch / cut glass
with a few simple lenses, no need for fiber coupling.

One of those Coherent bar diodes with liquid cooling come with correction optics, the diode
could be replaced with a larger output diode.

Yes it may be inefficient when compared to a CO2, but you cant say its not possible.

400W & 800W diode bars are also available on ebay, so I wouldn't count them out entirely.

Just saying :beer:
 

Meatball

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Understood, but why claim that 100W of 808nm could not cut foil? or any metal
for that matter? Too shiny? Those are false statements.

This is 15W cutting through a highly reflective 0.2mm stainless steel:


Besides, who uses any laser without optics? 60W 808 can also etch / cut glass
with a few simple lenses, no need for fiber coupling.

One of those Coherent bar diodes with liquid cooling come with correction optics, the diode
could be replaced with a larger output diode.

Yes it may be inefficient when compared to a CO2, but you cant say its not possible.

400W & 800W diode bars are also available on ebay, so I wouldn't count them out entirely.

Just saying :beer:
All these 808nm CNC applications you show are with fiber coupled beams. They are certainly not mounting the diode as well as aberration correction optics on the CNC head. The setup would be difficult to install, maintain, and control. It would have only a fixed focal length, and would be subject to vibration and mechanical shock which risks optical alignment and reliability.

Instead, the fiber coupled array is not local to the head, it is off somewhere else, being water cooled/temp controlled, away from machinery.

Yes, you could take lenses and poke some holes in various metal with the ebay diodes, but you cannot make a "laser cutter" device out of it. That is my point. The two functions are very different.

OP will have plenty of work to do, even if he scores a 100W fiber bundle. Getting holes poked through a sheet of aluminum will be some of the least of his worries to begin with. That worry comes later on..
 

Ethienne

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All these 808nm CNC applications you show are with fiber coupled beams. They are certainly not mounting the diode as well as aberration correction optics on the CNC head. The setup would be difficult to install, maintain, and control. It would have only a fixed focal length, and would be subject to vibration and mechanical shock which risks optical alignment and reliability.

Instead, the fiber coupled array is not local to the head, it is off somewhere else, being water cooled/temp controlled, away from machinery.

Yes, you could take lenses and poke some holes in various metal with the ebay diodes, but you cannot make a "laser cutter" device out of it. That is my point. The two functions are very different.

OP will have plenty of work to do, even if he scores a 100W fiber bundle. Getting holes poked through a sheet of aluminum will be some of the least of his worries to begin with. That worry comes later on..

Why is everyone posting about cutting using 808nm to cut?...I understand that the initial discussion was about that but, as I posted above, I turned away from the idea, since you guys convinced me that the laser was of bad quality and could not be used to "Cut" cleanly. My intend is to use a Nd:YAG as a gain medium. Is it still that much of a bitch to get the laser output from a Nd:YAG to cut? ( compared to 808nm) Isn't all I need a focusing lens... I mean research has proven that beam quality approaches a M^2 of 1.1 using 808nm diodes as a pump.
 

MarioMaster

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Creating an appropriate cavity for side pumping a YAG rod with diode bars is a significant step up in difficulty. You'll need appropriate power cooling for the diode bars, a reflective cavity with the rod in the focal point, then find appropriate mirrors to create your YAG's lasing cavity. You'll probably end up having that fiber coupled anyway since you wouldn't want to mount the entire laser to a moving gantry unless you can reconfigure it to move the bed instead of the laser.
 

Meatball

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Why is everyone posting about cutting using 808nm to cut?...I understand that the initial discussion was about that but, as I posted above, I turned away from the idea, since you guys convinced me that the laser was of bad quality and could not be used to "Cut" cleanly. My intend is to use a Nd:YAG as a gain medium. Is it still that much of a bitch to get the laser output from a Nd:YAG to cut? ( compared to 808nm) Isn't all I need a focusing lens... I mean research has proven that beam quality approaches a M^2 of 1.1 using 808nm diodes as a pump.
Just trying to clear of the air of information which isn't quite right...
I'm picky like that.

Sure, getting a high power/quality YAG beam to cut something is relatively easy! The journey will be in the design and construction of the high quality beam. There are numerous design parameters to select appropriate to your needs - which I'm still not quite clear on.

MM is quite right, the pump chamber/cavity will need to be suited to efficiently coupling the 808nm beam into the rod - either from the side, multiple sides, or the end. Depending on your application, the pumping configuration, rod size, duty cycle, all affect the ultimate design of the lasing cavity. I read this section a long time ago, but I'll just point you to it if you know what your needs are already.

Sam's Laser FAQ - Home-Built Diode Pumped Solid State (DPSS) Laser

There's stuff in there about doubling the output - but you don't need those sections. You'll need access to a good machine shop, a clean, dust-free work space, and a few hundred $$ just to get your initial setup arranged.

If you're lucky, and find a diode pumping chamber for YAG on ebay or somewhere, you can start with that and find a new rod on the bay as well as 1-2 of the multi-watt pump diodes. Then you'll need to construct a PSU for the diode (info can be found on the forum about that), a cooling method for the diode, some cylindrical lenses to focus the diode array (probably around 3-4 of them), and some basic HR and OC mirrors to setup your basic lasing cavity. Good mirror mounts are recommended for accurate adjust-ability. High grade safety glasses are a little more than mandatory - 808 and 1064 are well within the MOST MOST MOST dangerous of wavelengths to work with.

This might prove useful for you: The aberration correction of a Diode Laser

Cooling the diode might be as simple as mounting it on a big heatsink - but the temp coefficient for the magic rocks on top may require temp regulation for pumping efficiency (not all diode bars are 808, might be more like 803-810 which is bad for pumping YAG), so water cooling may be another "system" you need to install. Same goes for the lasing medium, the rod will get hot and become easily damaged without (usually water) cooling around the rod sides.

If you choose CW, consider going with vandate instead of YAG, (lower efficiency, but better thermal properties and not as sensitive to pump wavelength). A pulsed setup may be difficult to setup, but easy to achieve great power with. CW would be more dangerous for you and the components which are then more likely to fail (thermally) at some point if things are not regulated or actively controlled.

Are you USA based? Try going for a classic SSY-1 laser from ebay or somewhere. Its a small YAG setup perfect for a first solid state laser experience/experiment.

If you cannot find a diode pump chamber for a rod ready made, well, then you've got some classical optics to study and a bit a math to do!

Set aside about 100 hours of your life to get things aligned right, and optimized for passable performance - working with IR is time consuming.

Hopefully its starting to sink in, that you're looking at quite a project!
 




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