Help with build questions on ND:Yag

Ok, so i am doing my first build and most people will say that I am going overboard but my plan is to learn as I work through this as my goal is a DPSS for my cnc plasma cutter to turn it into a laser cutter/engraver.

I am currently experimenting with a 20w 808nm laser diode bar which I recieved surplus.

I was looking to power this one and maybe later down the road 1-2 more of them or maybe a more powerful like 60-80w unit.

Diode drivers are expensive and so I was wondering if a DC bench top power supply with current and voltage regulation could be used either directly or with some minimal modification (like some add on regulation or conditioning circuit).

I was looking at this unit:
PowerTen Inc 3350D-7.575 DC Power Supply - eBay (item 220547495661 end time Dec-23-10 14:26:34 PST)

and here is a spec sheet on it:
http://www.airlink.dk/Dokumenter/PT3300.pdf

Any advice would be helpful, thank you in advance.
-rtavk3

I can't offer much advice on powering the diode bar, but I'm curious as to why you are wanting to go DPSS for engraving or cutting. You'll be loosing a lot of your cutting power through the DPSS system, plus you'll have all the complications of aligning everything and making sure everything stays cool.

Do you have the datasheet for the diode bar or any idea what sort of current it requires? That info would defiantly help you with finding a proper power supply.

You should consider CO2 if you are serious about laser engraving or cutting. A CO2 laser would be cheaper, more powerful, and more versatile as an engraver/cutter than an 808nm diode bar.

I have heard that both Yag and CO2 have their good and bad points. For me mainly the draw for yag was that it can be compact which allows me to not have to have complex optics to get the beam to the cnc head. a small dpss laser can actually sit on the head while a CO2 laser at close to a meter cant really do so. Also I would rather work with low voltage than high.

At this point I am still kinda going slow on the dpss side and if it does turn out to be a problem will then start researching CO2.

What sort of CNC setup are you working with? Is it a moving table or moving gantry system?

Still, the entire DPSS system is not really necessary. You could use the raw output of the 808 diode and you'd have more potential cutting power.

Also, with a diode bar you'll be working with relatively low voltage at very high currents. With a CO2 you'll be working with high voltage at low currents. A CO2 would be a heck of a lot safer once you were actually cutting too, a lot safer than any wavelength you'll possibly get from an 808nm diode that is.

Did you manage to find the power requirements of your diode bar? I might be able to point you in the right direction if I knew what sort of current that bar needs.

The DPSS system is really necessary, what made you think that a diode bar could ever be focussed properly? Some extremely complicated optics could do that to some extend, but definately not a good as a DPSS.

A DPSS head can be far more compact, the whole resonator can be even shorter than 10cm. If you want the head to be compact you can use watercooling, but a few TEC's and a large heatsink will probably work too up to some power level. CO2 lasers will defiantely require good water cooling.

You don't have to use high voltage. A clean current source is easy to make, I can draw a schematic in 5 minutes. A CO2 power supply is more complicated. A good bench powersupply can be connected directly, but I'd take a few precautions because for example my power supply spikes enormously when turning on.

Diode bars usually take tens of amps at around 2.2V. Usually 25A for a 20W diode bar, 50A for a 40W diode bar. And recently diode bars go dirt cheap at ebay. Add a crystal and two mirrors in a cavity and you're done.

I'm planning of making one myself, but it's not the first thing on the priority list, first I'm working on my pulsed Nd:YAG and then the 355nm yag I have, but I already have 4 diode bars, 2 Nd:YAG crystals and 1 mirror set.