semi-nOOb Q: power ratings, class, etc meaning?

[Ashton]

I've been interested in lasers my whole life and by the time I was 12 or so I started acctually researching, so I do know some of the basics, especially safety-wise.

However, I am a little confused by the meanings of the outputs and also how they corispond to the ratings. I looked at the stickies and the links didnt help (the one about state laws was in fact, down) Differences in measurments in mA and mW and what they acctually mean would be nice.

What I *have* noticed that I'm trying to understand is the breakpoint for lasers sold tends to come around 120-150ma. This is a concern to me because the one I'm looking at averages 220ma and the diode tops out at 500ma. --- what I want is to use it as a laser-cutter for thin plastic, latex, and, is posible, thin aluminum/steel (i.e. used for SFX work and computer case mods, I'm a grabbag of unusual interests/jobs)

I likewise got further confused by such sites as wiked lasers, who rated their lasers by odd "perks" like popping baloons and "cut healing power" (I assume cauterization?)

IF this has already been covered, I appoligize. Thanks in advance for any replies!

 

[TigerhawkT3]

It has been covered several times, but good laser info can be notoriously difficult to uncover. I'll help you out.

Laser power is measured in wattage (mW), which is a unit of "power." Amperage (mA or A) is a unit of current. Amps multiplied by volts will give you watts, although you have to remember that "watts in" will be less than "watts out" (the closer the two, the more efficient the device).

Class II: under 1mW
Class IIIa: under 5mW
Class IIIb: under 500mW
Class IV: over 500mW

You'll need a really powerful laser (Class IV) to cut at decent speeds. Around 100-200mW might be enough for thin, dark plastic or latex, but anything tougher will be more dangerous, difficult, and expensive.

Safety first!

Welcome to CPF.

 

[erckgillis]

Think of mW rating like RPM's in a car engine. Higher is not always better...

High RPM's are "relative" to the car and engine. A Kia is not a Porsche. Big engines have lower RPM. Big diodes run at 1W and up. A 250mW Diode DPSS will be hard driven to produce 50mW of Green lased light.

Over rev RPM's and blow a big V8 engine... as can a Diode driven over current limits & voltages. One spike without clean power and ...poof! Some discussions over need for Reg power with 'clean' batteries...another post

My Dremel does 12K RPM but has little touque. A small diode driven to high currents & temps will shorten life. As does removing regulated power supplies.

Many manufactures find that 1:1000 modules have a combination of better crystals, diodes or optics that produce tight high power beams. These are then sold as higher class IIIb >5mW the rest 1-5mW and all those below ares used as <5mW keychains, pens etc.

Read the specs...get the BIG diode driven below it's limits. Not the small one driven overspecs.

Also burn power etc all varies by beam size, collmination and optics.

China and Ebayed low cost units usually quote WIDE ranges "... 5mW 10mW 20mW 50mW ....etc"

These boast are usually not 532nm but TOTAL with IR. so see table below

Wavelength .....No Filter IR..... With IR filter (blocked)
532 nm...........401.0mW.......... 52.1 mW
808 nm........... 35.4 mW........... 3.68 mW
1064 nm.......... 64.1 mW........... 8.16 mW

Power

Initial Peak ............125.0 mW
After 5 Seconds...... 44.8 mW
After 10 Seconds.... 28.8 mW
After 15 Seconds.... 16.7 mW

As the Diode heats up it draws more current, more current requires regulation to limit. Without this the diode overheats...then effeiciency goes down, wavelengths change toward IR and beam becomes usless as filters remove all power....

..all power is relative

A cheap pointer could therefore be 8-125mW or 16-401mW !

Put the diode on a heatsink or liquid cooled CPU mount , remove your filters and burn your eyes out. The IR "halo" is three times the dia of the green and completely invisible, passes thru green rated goggles @ 808 and 1064 nm
...so beware...you get ONE SET of eyes. OD rated goggles would be BLACK.

Customs will confiscate any +>5mW Greens shipped with batteries...beware! US makers should not ship class IIIB/IV overseas. These are controlled and regulated.

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[Ashton]

Wow, thanks for all the info.

I have a friend who's an electronics engineer who's helping me with this, there are going to be regulators. I'm acctually building this laser myself using this as a baseline:

http://www.felesmagus.com/pages/lasers-howto.html

with this as the diode:

http://www.newegg.com/Product/Product.asp?Item=N82E16827152075

Though I think mine maybe a tad lower, I think it's only a 16x not an 18x...

I'm planning on having a switch to move between pointer/targeting mode (<5mA) and cutter mode (~220ma/300ma/???) Along with the proper resistors to prevent diode damage, and, of course, a lock mechanism so this does not turn on in my pocket (and so a little kid cant pick it up and bling hiself or someone else with it) I also do have an IR filter and a lens, however, I would think that the IR "beam" also increases the burn power of the laser, so wouldn't it be a better idea to channel the IR into a smaller beam alongside the laser than to cancel it out? (layman here, I know just enough to be dangerous, sorry)

and if all else fails, I'll just have to try to find a prebuilt laser online for <$400 that will serve my needs...

 

[Ragnarok]

If that's a visible red laser you don't need an IR filter.

Red diode laser:
Diode --------> 635-670nm red, depending on the diode. No IR.

Green diode laser:
Diode 808nm IR ---> Nd:YVO4 crystal 808+1064nm IR ---> KTP doubler crystal ---> 808+1064+532nm green ---> IR filter ---> 532nm.

 

[erckgillis]

As you cannot see this IR "leakage" it is dangerous to your eyes. As damage occurs without any warning. You'll not get 200-300mW from a diode that 10mW rated. If the original diode drives 2-3x higher than the output then this is good efficiency. you cannot get 300mW from a 10mW diode...well you can...but once.

Heat kills, so cool the diode, heatsink and all with active or passive systems and you'll see higher outputs...

The "extra" power from the iR bands will not help your "burn" performance as it's not well collumated and is very diffused or dispersed.

A small 3mm Green beam may have a 3' circle or raw IR around it.

See this IR HALO with a "Night" or Low Light CCD video camera.

Danger Will Robinson!

 

[Ashton]

O.O!!! I hope you mean 3" halo, but I suspect you did mean 3'... holy s***!

I'm glad to hear the red give sno IR though, that's a major relief.

 

[iemand]

Thx @Erckgillis for this illuminating information.