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Increasing the power of a 5mW green laser pointer

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Andrew L.

Tue Apr 17 2007, 06:58PM

Registered Member #515 Joined: Sun Feb 11 2007, 02:06PM
Location: Slovenia/Ljubljana
Posts: 94

Hello

I have two green laser pointers at home(5mW) and I was thinging of taking apart one of them. And my question is can I increse the output power of the green beam just by putting in a more powerful 808nm infrared laser diode than the one that is inside.

Alessandro

Tue Apr 17 2007, 09:51PM

Registered Member #70 Joined: Thu Feb 09 2006, 08:19AM
Location:
Posts: 43

Typical 5mw green lasers are "underclocked" when they leave the factory. Almost all of the cheaper versions have a pot mounted on the circuit board inside. You can increase the the power to at least 10-15mw by adjusting that, defending of the efficiency of the crystal set inside (varies with each batch) some people have hit over 50mw. These lasers usually have an 200mw IR diode inside. How successful in boosting the power buy replacing this depends on the quality of the crystals. You might also find that heating caused by the increased power might effect the precise crystall alignment. All in all, if your happy to risk one laser they try it! Try adjusting the pot first of all, this will give you an idea if its power can be increased alot.

...

Wed Apr 18 2007, 03:16AM

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

You can probably get 50mw out of it as it is (but it will only run for a few minuted before the pump diode dies) or you can probably put in a more powerful diode and get 50mw for a reasonable period of time.

And actually, the diodes are very easy to replace in most pointers, you just use a 1/4" screwdriver to unscrew the ring holding it in, lift the old one out, drop the new one in, and screw it back together. Due to the differences between diodes, you will probably also have to adjust the focus on the beam, which can be tricky but usually has a thread to adjust it. Unfortunately, it is hard to find diodes that put out >200mw in a 5.6mm can (for heat reasons), so you will probably end up having to heavily modify the laser to make it work with a laser in a 9mm can, or preferably in a to-3 can with an internal TEC cooler (as you need to keep the diode as close to 25C as you can, otherwise the wavelength shifts away from 808nm). Roithner is a great place to get them, you are looking for a diode in a 5.6mm can 808nm.

Basically what you end up doing is unscrewing all of the parts of the laser (being very careful to not touch any of the optical surfaces as a scratch/chip will kill you, and dirt is a major pain to get off) and you will end up with a piece of Nd:YVO4 and KTP bonded together in a tiny block about 1mmx1mmx3mm that is glued to a brass 3/4cylinder (don't try to separate it from the brass cylinder, just remove the whole part as a single unit), 3 or 4 lenses (depending on how th pump diode is focused), a laser diode, a small piece of green tinted glass (it blocks IR light) and possibly a small photo diode. Then you take you pump diode, glue the pump diode focusing lens(es) on it, then use some washers/etc to get the crystal at the optimum distance (brightest beam). Then you use the 2 remaining lenses (it usually works to leave them in their original piece of brass, they form a ~10x beam expander to tighten up the beam) to make the beam a nice well collimated beam.

GreySoul

Wed Apr 18 2007, 04:11AM

Registered Member #546 Joined: Fri Feb 23 2007, 11:43PM
Location: Albuquerque, NM
Posts: 239

On this note... anyone here recommend any particular source for a green laser pointer? I'd like something I can easily disassemble, that has a pot on it I can adjust.

Anyone I should specifically avoid?

-Doug

Michael W.

Wed Apr 18 2007, 05:06AM

Registered Member #50 Joined: Thu Feb 09 2006, 04:07AM
Location: Vernon, B.C, Canada
Posts: 324

I bought mine off of ebay and pot modded it....

Andrew L.

Wed Apr 18 2007, 04:35PM

Registered Member #515 Joined: Sun Feb 11 2007, 02:06PM
Location: Slovenia/Ljubljana
Posts: 94

Ok

Thanks for all the replies. So if I understood correctly the laser diod is run with a constant frequency and the output power can be adjusted by adjusting the duty cycle of that frequency right?

...

Thu Apr 19 2007, 02:15AM

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

Usually the diode is run at a constant current, and you can increase the power by increasing the current (usualoly set by a small pot on the driver circuit board). But there are a few pointers (usually only older ones) that pulsed. To check what kind you have just draw a line on a wall with it, if it is a solid line then the diode is on all of the time, if it is dashed then the diode is pulsed.

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