good greenie about 50mw?

[Brock]

I have an ebay green laser about 50mw or so it said. I also have a 5 mw green. The problem is both lasers changes intensity and are not consistent. The 50 mw is brighter all the time than the 5 mw but sort of flicks back and forth between brighter and about the 5mw level while on. I tend to use them for longer periods of time point things out so a constant on might be the issue? They are both 2 AAA lasers. Since I use it regularly at work I want a more reliable unit, suggestions?

 

[GBD]

Such is the issue with cheap chinese lasers, you must realize to achive 532nm (green) you require a DPSS system, where you start off with a pump diode of 808nm, which emits onto a crystal set (ND:YVO/KTP) to shift the wavelenth to 1064nm, before performing frequency doubling to 532nm.

This entire process requires fairly stable tempertures to have a consistant power output and maintain its emittion without mode hopping. Generally the modules in the pens you speak of are fine with running at higher tempertures (keep in mind your pen is not a good heatsink), but they swing in power as they do so, and at colder tempertures, even fail to lase altogether (the KTP part fails to double is usually what happens, 808nm from the diode still emits).

My point here is, due to the design of your pen bieng a cheaply made DPSS module with an insufficient heatsink (bieng your pen), you will need to find a unit with either a far larger heatsink (That will run cold and keep the module at a stable temperture) or to find a unit that has inbuilt thermoelectric cooling. (which is not typical for small portables, and mostly found in lab style lasers).

So now comes the part where you must ask yourself how much you want to compromise for power and stability, while cheap lasers like those pens can achive some pretty decent powers, they fluctuate and mode hop in the process, better built lasers are obviosly going to cost more, but will take care of these issues. For pre-built lasers I can vouch for lasers from O-like, Rayfoss, CNI and dragonlasers. Those companies do sell stable units and are typically more high quality then most of the stuff you will find around (dragon bieng just resellers of CNI, CNI bieng one of the best of what I listed).

The lesser of the two evils is to get a laser that is based on a diode alone, (but you will not find any greens this way) as it requires alot less stabilizing to achive fairly consistant powers. (it will still vary, don't get me wrong, its just you will not notice it without test equipment, so visually its nothing of concern.) 405nm, 445nm, 635nm, 650nm come to mind, the cheapest and most visable of the latter bieng 200mw of 650nm (more or less equiv in brightness to 50mw of 532nm).

405nm is good too, but lacks visability without stepping into serious powers (500mw>). So if you are really set on green and don't want to bother with other diode lasers, then I suggest you visit the companies I listed, they will have what you wanted originally.

The only issue with diode lasers, is that the beam specs at the moment will not outperform a DPSS system, with diodes you will have a fatter beam, and worse divergance then you would with any DPSS system. (single mode diodes like 405nm/650nm still have very nice beams and will go the distance, its just they will not outperform a DPSS system in terms of distance and divergance). multimode diodes such as high powered 635nm and 445nm have mulitiple emitter sources, so more or less its harder to properly focus the beam and results in more terrible spread then the latter without correctional optics. That, and diodes vary between eachother, both thier technical specs, but also thier price and availablity, 650nm/405nm comes from our favorite blu-ray and burner drives, a fairly common and cheap source, 445nm comes from a projector, so the costs even rise more, and 635nm is still only available from some manufacturers, so you can imagine it not to be cheap at high powers.
There are way more diodes then what I just listed, but these are currently the most common ones.

Either way you go on about it, I really suggest you also buy yourself some goggles made for whatever wavelenth you choose, if you ever use it up close or for prolonged periods it can damage your eyes, 50mw is dangerous for a direct flash. So if you value your vision do take some precautions.

Hope that helps you out a little to what to look for.

 

[Throwjunkie]

GBD your correct here is a Pic to show what you explained with DPSS lasers

Joe

 

[Brock]

I should add I am typically pointing out objects in buildings in the 100+ foot range, often about 300+ feet away and the buildings are usually lit well. I have a "good" red one but it doesn't even come close to the the cheap 5mw green (when its working) for people to notice what I am pointing at.

Thanks for this great information. So now my question looking at Dragon I like the viper or maybe the spartan line. I am guessing the viper 55mw will actually be brighter than the supposed 50mw unit I have now. I can see the beam at night but not at all during the day and there is no way would would melt even thin black plastic bags. I was also looking at the Spartan 30mw. Whats the real difference in layman's terms between the viper and spartan if they were both 35mw?

 

[Brock]

Wow, just went to o-like and they seem to have a 50mw pretty inexpensive

http://www.o-like.com/index.php?main_page=product_info&cPath=2&products_id=53

Maybe these are the way to go? I realize they are larger than the pen ones I have, but if it is buiolt better adn better all around I am fine with a little increase in size.

 

[GBD]

Well, my viper that I got a while ago turned out to be way overspec (was outing 165mw IIRC, metered with a laser power meter). mw to mw, the differance of true 50mw to true 55mw is really not very noticable without a meter(as your laser will probably fluctuate that much anyways).

For the range you listed, green and diode alike will have no problem with it (spread wise) so your options are really wide.

That O-like is good too, I never owned that particular one, but I have several modules from O-like that run fairly stable, and there are a good number of reviews, so I would say either O-like or DL are good choices.

Here is a little guide for you on visability, conider this ratio:

(R)4 : (G)1 : (B) 2

This is general idea, to true powers, matching mw from different colors (for this I used RGB, 650nm,532nm,473nm).
as a general rule here, you will need 4mw of red to match 1mw of green. so this is a rough guide if you want the same visablity at different colors.

The links you listed however are good, and those lasers will not dissapoint you. DL especailly, but the only downside about them is the price.

 

[Brock]

Thanks for all the info!

 

[bshanahan14rulz]

By the way, pic courtesy of Sam (THE Sam).

A reference for O-like, I've bought a cheap <10mW 405nm pen ("chrome" focusable 2xAAA) and a <30mW 532nm pen (the generic open-at-tail rubberized 2xAAA with cheap metal knurled star cap that screws on the front). They are both still functional getting close to a year now. Shipping, as expected, takes a while. You may be able to contact the store owner and see if you can get her to test the lasers out and pick you out a good one.

I've not personally purchased from rayfoss, but they are supposed to be another fairly cheap source for lasers. Think of these as the DX and KD (not respectively) of lasers; you may or may not need to fiddle with it some to get it to work as advertised.

Greens are hard to buy. It really is a luck of the draw, but it is also one of the best wavelengths for visibility. Direct injection green is a reality, and already available at very high prices, but for just a little while longer we must put up with the instability of the dpss system and rely on the level of expertise that the assembler of the laser module has. Over at the laser pointer modders hangout, CNI is pretty highly regarded but they are expensive and can only be bought from in batches.

Whatever your decision, keep in mind that often a reseller will make up the output power. Some, like O-like and rayfoss, just pass on the specs that the lasers were intended to match, whether or not they match is up to the customer to decide.

Good luck, and let us know what you end up going with!