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McFluffin

Sun Apr 30 2006, 02:56AM

Registered Member #119 Joined: Fri Feb 10 2006, 06:26AM
Location: USA
Posts: 114

My question is, is it worth trying to repair these? I got 4 green laser modules from a friend a while ago along with two nice red diode lasers. One of the red lasers is marked Class IIIB and is quite bright. That aside, the green lasers don't have any markings, but I finally was able to identify them with the help of an earlier thread on 4hv which makes me think that they are these:

The ones I have have the rectangular prisim aluminum casing as seen in the middle. Unfortunatly, there are some problems with them. Two of them don't prduce any beam. Originally I thought they were broken, but upon reading that site I noticed that they sell modules that are green only, so now I'm not quite sure. However, they all do have a green filter on them which I'm told is for IR bocking, so I'm fairly sure they are all green lasers. Of the other two, one of them works a little, but originally had a much stronger beam before it was hooked up to 12V for a second and now isn't working very well. Guess they are the 5V type.... The other one has been disasembled(but I still have all of the parts) and at the very lead has the Nd:YVO4 broken if not the laser diode as well.
I see comporable IR laser diodes going on Ebay for $100 or so. I was thinking that I could get one out of an old laser printer or CD-RW drive, but I'm not quite sure if that will work or not. Mostly though, I'm having a problem with getting a Nd:YVO4 cystal. I see some YVO4 on ebay, but not the Nd doped variety. Is this crystal very expensive? The KTP is still good in the laser with the cracked YVO4. The one with the broken Nd:YVO4 was a lot easier to dissasemble and is of different construction than the other 3 which have epoxy steel around the nuts holding their assembly together. Here is a picture of the half working green one with one of the dead ones:

The epoxied nuts:

Thanks for your help!

EEYORE

Sun Apr 30 2006, 04:48AM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

The laser diodes used in these are VERY picky about the driving voltage. 12volts likely damaged it instantly. They MUST be run via regulator (or battery) at the diodes specified voltage(around 3volts max). 5volts is also way to high. If you hooked the diode directly to a 12 volt source, they are fried

Those lasers in the CD-RW wont work. You need a laser diode operating near 808nm wavelenght.
Check out Sams Laser Faq online....Check out Casix, as they sell hybrid crystals with the KTP and the vanadate combined(I beleive they will take up to a watt of laser radiation input too) t. One of those, a working 808nm laser diode, and some optics will get you a green beam...
Matt

McFluffin

Sun Apr 30 2006, 05:39PM

Registered Member #119 Joined: Fri Feb 10 2006, 06:26AM
Location: USA
Posts: 114

On their web site though, I think that I had read that they had 5V and 12V modules. I had been running that one at 5V with no problems, although I have seen that most laser diodes use 3V. In the future should I assume that all unmarked laser diodes run at 3V?
That shounds a little extreme buying a laser diode, the KTP, and the Nd:YVO4 as that would be nearly starting over from sratch, especially since I think the KTP alone is rather expensive. I still have 3 KTP/YVO4 assemblies that are working. The reason why I was asking about CR-R drives is that I had read about that in Sam's laser FAQ. To quote from

: "The laser itself - For really old LaserDisc players, this is a helium-neon gas laser tube (probably linearly polarized) and high voltage power supply. All the others use diode lasers which require current limited drivers to prevent instant destruction. The output power of these lasers is usually less than 5 mW except for writeable optical drives which may go up to 30 mW (but IR) or more. " I think I read something similar about laser printers.

...

Sun Apr 30 2006, 08:14PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I would say that if you are asking these kinds of questions then it is probably not worth the effort to fix them...

From the looks of them, the modules you have don't have a driver for the diode; which means that you must be
very careful about driving them. I would test the working one by...
1. take a well regulated power supply (if you do not have a nice low ripple supply use 4 aa batteries in series with a small value variable resistor) and attach a voltmeter across it. Then make sure that that it reads 0v for a power supply, or is using a resistor/battery that you cannot draw >1a from it.
2. attach the laser diode
3. slowly turn up the voltage... There will be no beam, followed by a beam of increasing brightness, which will level off. If it is a regulated module, then it will level off right around 5v. If it is just a laser diode it will level off considerably lower than that, and turning it higher will cause the beam to get dimmer. At this point you are damaging the laser, turn it back to where the power starts to fall off immediately.
4. Record the current that it is running at, the light output of the laser diode is mainly dependent on current.

If it is a bare diode, you must be very careful with them. Whenever they are not connected to a power supply you must keep a piece of wire across the diode; they are extremely sensitive to esd. Whenever you connect it to a power supply you must be sure that that there in no voltage coming out of the supply, most supplies have a capacitor across them that is plenty to blow a laser diode. I blew a diode once because I had been using the supply for a 12v module than turned it down to 0v for the diode, but as soon as I connected the diode I hit the diode with 10v for a millisecond and killed it.

As to the rest of the optics... I wouldn't bother trying to buy individual crystals, you could get a complete 5mw 532 mn module for $20 now (laser pointer)... You could buy a vandate/ktp combination (you just hold it directly up against the laser diode and you get green light) good for 100mw out fro casix for likr $100. I would be very cautious buying crystals off ebay, a lot of the ones are rejects, missing the coatings/mirrors on the crystal, damaged, whatever. If you find the auctions with the diodes out of laser pointers you are usually ok, but you need to be absolutely sure that the crystals are not cracked.

I would also be wary of buying diodes on ebay... Most diodes >1w are actually a block of smaller diodes, which are completely useless for this application as they will focus down into a series of spots, which (without some very complex beam shaping optics) are useless for pumping laser diodes. Many others are at the end of their lifetime, and putting out much less than the rated output.

Have you considered selling/trading them?

Good luck!

Steve Conner

Sun Apr 30 2006, 09:55PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I design laser drivers for a living, and I second everything ... said. Bare laser diodes are electrically very similar to LEDs: they don't have "a rated voltage" as such because you're not supposed to run them off a voltage source. You use an electronic constant current regulator instead.

Next time check what kind of driver circuit it has, and what voltage it's intended to run off, before jamming 12v up its butt

Madgyver

Sun Apr 30 2006, 10:03PM

Registered Member #177 Joined: Wed Feb 15 2006, 02:16PM
Location: Munich, Germany
Posts: 214

Dude, good you showed up. I started to think everything I learned about Semiconductor Lasers was wrong.

How do you power up unknown Laserdiode anyway? Does the "current/output power" curve flatten at the right current rating?

Marko

Sun Apr 30 2006, 10:16PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

How do you power up unknown Laserdiode anyway? Does the "current/output power" curve flatten at the right current rating?

I usually increase current, until the diode blows up, then I turn it back a bit.

When testing an unknown diode it is good to know at least some information, some sign of max output powe, etc.

Then only thing you can do is to energize the diode with current source and slowly increase, checking for heating, if it shows any signs of bing too hot you must lower the current.
But the best thing is just to have a matching datasheet and do as it says.

McFluffin

Sun Apr 30 2006, 11:39PM

Registered Member #119 Joined: Fri Feb 10 2006, 06:26AM
Location: USA
Posts: 114

Thank your for your responses. Max output was at around 5V. How would I get a datasheet? Their site only advertises a 12V input, doesn't seem to have a datasheet, and a datasheet for a 12V module probably isn't what I'd want.
As far as selling them, not really sure who I'd sell them to. Ebay perhaps? I'm not really sure if a lot of broken lasers would go over to well, but I could be wrong. However, it does look like they were worth hundreds of dollars each new, so I guess they still would have some value.
They are inside aluminum casings and were taken out for a minute for the picture. They all have a diode across the leads, but other than that there only appears to be the raw diode. I am still curious about the CD-RW drives. Can I get a second opinion on them?
These were unmarked and came with no circuits etc. They came with my friend's uncle. My friend thinks that they were used for holography, but didn't meet specifications for some reason and so were put out of service.

Steve Conner

Mon May 01 2006, 12:36AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Unfortunately, working out the maximum power of a laser diode can be a hassle. Some devices "roll over" ie as you continue increasing the current, the optical power starts to go down. For some devices that I've worked with (like semiconductor optical amplifiers), this rollover point corresponds with a sensible maximum rating. But in the majority of laser diodes (afaik) the rollover point can be 5 to 10 times higher than the highest safe current you can use for continuous operation, or doesn't ever happen at all. So by the time you got there, you've already blown it up! :-o

I probably wouldn't buy a laser diode if I couldn't find the datasheet.

...

Mon May 01 2006, 01:05AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

no, you cannot use the laser from a cd drive. Not even a burner

You could however get a dvd/dvdr and use the laser (with appropiate driver/optics) as a red laser, the wavelength used for dvd drives is a very visable shade of red.

You need a diode that puts out (within like +/-1nm) 808nm light. This is due to the physical makeup of the vandate, it cannot be changed.

As to getting rid of them, you could ebay them... I wouldn't mind trading for them... The last time I was on the hunt for 532nm I got a lot of 3 laser pointer guts for $30. To my suprise one of them was alive, but that was the one I fried as described earlier

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