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Cheapie Laser – Part Two

Posted 2006.11.09 12.19 in Lasers by Stephanie

I’ve already discussed the dangers of cheap green high-power lasers in another article. Now, I’ve fully disassembled that same laser in order to learn more about how it works, what it does well, and what it doesn’t. I’ll also hopefully find ways to fix or remedy some of the problems.

To review, here’s a photo of the laser as it was when it first arrived:

green ebay laser

This laser exhibits the following problems:

  1. Came with no IR filter – lots of IR leakage! (fixed as per my other article with an IR filter)
  2. Starts off with a lot of output power but quickly drops off very low.
  3. Output is very messy, at 10 feet, the speckle is at least 6 feet across – lots of power wasted in speckle instead of the main beam.
  4. Output of the laser has a large line through the dot, like dirt or a scratch somewhere inside.

The following image is one I took of this laser going from my livingroom to a bedroom. From the laser to the doorway, the distance is about 13 feet. Note, to the right of the visible beam, you can see green light along the wall and onto the edge of the sofa. Now look to the left of the beam, to the coat tree. Just to the left of the coat tree, just below the lower edge of the red jacket, you can see some more green light. That light is speckle, emitted from the laser. It’s not a TEM multi-mode, it’s just wasted energy, coming out at all angles and cannot be collimated. It is not dust on the lens.


When shining this laser at a blank white wall, the dot is surrounded by a ‘galaxy’ of little dots. It’s all technically output though, and if all that junk were part of the primary beam, the primary beam would be that much stronger. Instead, perhaps 15% of its power is wasted. It’s still ‘output’ though, along with the IR that you get without a proper filter.

And now, on with the dissection… I don’t have any photos of how I got the laser module and circuit board out of the shiny metal tube. Suffice to say, it was a destructive process and the shiny metal tube did not survive.


The Laser Guts

Laser Module

Here is the complete module. From left to right, the major components are: Green circuit board (with black pushbutton); Knurled brass diode holder; Brass lens barrel; Chrome aperture. The aperture part unscrews very easily.

You can see at the back of the circuit board, the stubs of red and black wires that I had soldered to the board when I had this laser module mounted inside a project box. You can also see the trim-pot that can be used to modify the output of the laser. Bear in mind that the output of this laser is not stable at any power level.

lens barrel

To unscrew the lens barrel from the rest of the laser, I gripped the knurled part tightly in pliers then gently but firmly unscrewed the barrel. If you are doing this yourself, start very slowly, like 1/10th of a turn, and verify that the diode and circuit board are not moving relative to the knurled ring or lens barrel.

Without the lens barrel, the laser still works fine, but the beam collimation is much worse – it starts off as a very tiny pin-prick but at 10 feet its about 2 or 3 inches across. The lens barrel contains two lenses, the first expands the beam even wider then the second lens collimates that…more or less.

lasing without the lenses

Here you can see the laser working just fine without the lenses.

laser mca unit

Once the lens barrel is off, you will see inside the end of the laser module a smaller threaded brass tube. This tube holds the MCA (multiple crystal assembly) in place infront of the pump diode. The MCA holder just unscrews and comes out.

cicruit board and laser diode

From the back, the laser diode appears to be a standard 5.6mm can format. When assembled, the case of the diode and the brass assembly is at +3vdc.

I haven’t bothered to map out the circuit diagram, or to check the current the board draws. It is pretty straighforward though – a button, a trim pot, one resistor, two capacitors, one transistor and one component which looks like a voltage regulator.

front of pump diode

From the front, the pump diode does not look at all like a 5.6mm can. In fact there’s no can at all. It’s basicaly just a bare diode in there. It is tiny, you can’t even see the diode in this picture. The diode sits on the lower side of the brass ‘rectangle’ bit, between the two pins. The square bit below all that is the photodiode, used for feedback.

Also note that there is no lens here to focus the pump diode – it is completely bare. The divergence from a bare IR diode like this is measured in degrees, not mrads. When activating the laser in this form, at about 3 inches the 808nm light is about 1/8 inch thick and about 3 inches long.

I tried to measure the raw 808nm output to see what it was producing. With 2.4vdc input (two NiMH AAA batteries) I was able to measure just over 300mW of IR on my LaserCheck meter. If I had a good 3 volts going in, there might be up to 500mW of unfocused, uncollimated IR available.

mca input

Here is a close-up of the input side of the MCA. The grey gunk is glue that holds the crystal in position. The purple of the crystal is, I think, the Vanadate responding to the flash in the camera. Note also that the purple is not consistent. You can clearly see lots of imperfections on the face. I am pretty sure these imperfections cause some of the serious speckle and poor beam quality that this laser exhibits.

The poor quality of this image is due to the magnification. This component is about 5mm in diameter at most. The MCA itself is perhaps 1.5mm x 1.5mm x 3mm long.

mca output

You can see the output coupler side of the MCA here. This is the KTP crystal. I think the green ‘glow’ is a result again of the crystal interacting with the flash in the camera. To the naked eye, the crystal looks slightly pink when looking through it. This side of the crystal looks a lot nicer than the input side.

input side of the lenses

This is the side of the lens barrel that faces into the MCA. The lens you can see is just cheap plastic, and it is held in place with glue. You can’t get a good idea of depth but the lens is about 8 or 10 mm down into the barrel.

What you don’t see here is the IR filter, because there isn’t one. If there was though, this is where I would have put it – after the MCA, before the lenses. That way nobody can remove it without complete disassembly.

output side of lenses

The external lens is also cheap plastic, and also held in place with glue. This makes it really hard to adjust the focus / collimation. By really hard, I mean, you can’t. I was able to remove the output lens as the white glue was kind of crumbly, but you can’t focus it, you just kind of push the lens around and hope for the best. If it were threaded you could at least tweak it till it was good.



I had fun taking the laser apart and learned a lot more about it – what it does well, what it doesn’t.

As for the problems listed above, here’s what I’ve determined:

  1. I added an IR filter into the chrome aperture, as per my other article.
  2. I don’t know the cause or solution to the power drop-off yet. It’s either a diode problem or an MCA problem. More research will tell me the Why. I think it’s the diode though, shifting frequency as its temperature changes.
  3. The speckle is definately because the MCA is bunged up on the Vanadate side, and maybe bunged up inside as well. Basicaly the MCA is low quality, IMHO.
  4. The line across the output is because the pump diode is not shaped or focused! The laser outputs a line because the diode is feeding a line into the MCA.

Now, if I were to go and buy a new MCA that would clean up most or all of the speckle, and maybe add a lens to focus the pump better into the MCA, and then maybe devise a better set of lenses for shaping and collimating the beam… As for the power dropping off fast that probably would require a new pump diode anyhow. By this point I’d have built a whole new laser from scratch. Cheaper and easier to go buy a good laser in the first place.

That’s about it for now. I hope you’ve all learned some more about cheap green high-power lasers.


The Fine Print
Information provided on this page is based on my own personal experiences.

My Three Lasers

Posted 2006.10.29 0.00 in Lasers by Stephanie

For no reason at all, here’s a picture of the three red lasers I made out of computer DVD burner drives.

Three Red Lasers

Business End of DVD Laser

Posted 2006.10.05 0.00 in Lasers by Stephanie

More tinkering with lasers. I’ve pumped up my DVD laser even more. A better lens gives it higher output. From 180mW to 205mW, on week-old batteries.

Enough power, when focused, to cut through electrical tape in 6 seconds. Enough power even, to burn the wood-like-finish of my desk!

Stephanie likes lasers.

6-Second Tape Cut Movie

Business End


Posted 2006.09.25 0.00 in Lasers by Stephanie

Here’s a great link, everything you want to know about how laser diodes work.

Laser diodes are super tiny but can be surprisingly powerful. Find out how, and why. Warning: Linked site may contain science, physics, and education.

How Laser Diodes Work

Laser Diode and a Penny.
Photo from Wiki

Yet Another Lasers Post

Posted 2006.09.17 0.00 in Lasers by Stephanie

I was doing a bunch of cleaning and a little redecorating today, and for a break in the middle of it all, I made another high-power laser.

In this case, I took an old low-power laser pointer apart, removed the 2.5mW diode, hot-wired the driver board, and replaced the diode with a high-power diode from another DVD burner.

This pointer is old, more than 5 years, maybe as much as 10 years old. I know it cost me about $50, and it came from Radio Shack. But they don’t appear to sell anything like it any more. I like it though because of the tiny size, only 3 inches long and 1.5 inches wide. It runs on two AAA batteries, but they go in side-by-side.

Anyhow, now that it’s been pumped-up and had a diode transplant, it’s now pumping out about 100mW, as much as the low-end Pulsar. Enough to pop a balloon or light a match, with the help of a focusing lens. Without a focusing lens, it’s just a really, really, really bright laser pointer.

Update: As a pointer, this laser has a switch to select between dot and line. The line was produced by a little optic. I’ve removed that optic and replaced it with a focusing lens from a DVD player. Now, at the flick of a switch, I can select between well-collimated long-range dot, or close-up burning power. Now I’m thinking if only I could have put a 150mW diode in there instead of the 100mW, this could become my favorite pocket-laser.


Group Shot

Posted 2006.09.12 0.00 in Lasers by Stephanie

Here’s a recent pic of four of my lasers in my home-made enclosures, and a fifth enclosure waiting for a laser to go in it.

The DVD Laser is the one I made from a DVD burner, it’s running at 200mW now which I think is pretty impressive. The IR laser is also up a bit, running around 130mW. The 635nm Red laser is <10mW, mostly used for amusing cats. And the Cheap Green Laser is a repackaged laser pointer.

The Usual Suspects

A Cheap Green Laser

Posted 2006.09.10 1.00 in Lasers by Stephanie

When I was new to the exciting world of high-power green lasers, like many folks I didn’t really know much about what I was getting in to. I had learned that there were pocket-sized ‘laser pointers’ that could pop balloons and light matches, and I wanted in on that kind of fun.

I had found the Wicked Lasers web site and saw what they had but it seemed kind of pricey. So like many of us, I went to ebay to see what was there, cheaper.

I should have known better because a) cheaper means both ‘less expensive’ and ‘poor quality’, and b) if something seems too good to be true then it probably is.

Nonetheless, I soon found an auction listing for an ’80mW Green Laser Pointer’. The price was almost $100 less than Wicked Lasers wanted for their 75mW laser. And the vendor was in Canada, which meant faster shipping and no duties / brokerage, and no hassles at the border. So I plunked out the money, and in a few days, it arrived.
green ebay laser

The Good, Bad, and Uncertain

Sure enough, the first match I put it to ignited almost instantly. I was wowwed, I was happy. Strangely though, the second match I tried, smoked a bit then did nothing at all.

Soon I realized that it was only super-powerful in the first few seconds. Then its power tapered off considerably. You could even see it, shine the bright green dot on a white wall and it went from blinding, to just bright, really fast.

During all this time, I was still reading and learning and gaining more experience. I quickly learned the complicated way that green lasers work – much more complicated and finicky than a red laser pointer. Over at Green Lasers UK they have a great little tutorial on how green lasers work and how they differ from red lasers. Suffice to say, I soon understood that there are two ways to state laser power: peak, and average. Wicked Lasers might cost more but the stated power is their average. Cheap lasers usually seem inexpensive because they quote you the peak power – a rating which it might only attain once or twice, if ever.

By this time, I had decided that I wanted to get involved with lasers quite a bit, so I decided to invest in a laser power meter. The LaserCheck by Coherent was the most inexpensive, small meter that would work fine for the ranges I was looking for.
Coherent LaserCheck

So I got my meter, checked all my lasers, and lo and behold, it worked for all the red and infrared ones, but not the cheap green one! The reading was crazy, like over 400mW! Was my new LaserCheck not working? No, it works fine. I soon learned that the LaserCheck, which measures optical brightness, is easily confused by multiple-wavelength lasers. My ‘green’ laser was putting out green at 532nm, but also infrared, at 808nm and/or 1064nm. (For information as to why there is IR in a green laser, see the link above.)

Aha! Here is another way for the unscrupulous to get away with selling what seems like a high-powered laser. If you take a cheap green 5mW pointer and remove the IR filters, you will still have 5mW of green light, but now you also have a lot (as much as over 100mW) of IR light as well! So you can sell your cheap green pointer, as a 50mW, 80mW, or even 100mW laser, make lots of money, and claim that you are not lying since it is in fact generating that much IR!

Safety Matters

So what’s wrong with a little IR in the mix? First, it’s not a little it’s a lot. Second, it’s invisible, you can’t see it. Third, if you’re relying on laser goggles rated at 532nm to protect your eyes, you may as well wear no goggles at all because they won’t do anything to block the IR, and worse than nothing, you might take some extra risks in the belief that your eyes are protected since the green dot is dull and doesn’t hurt to look at! Additionally, the IR is not as well-collimated, so it spreads out more, which means you might not even know you’re getting dangerous specular reflections of IR in your eyes, because the green is not reflecting your way.

Wicked Lasers sells great laser goggles at a great price – but they are not rated for IR! If you buy cheap lasers, shell out for expensive goggles. If you buy quality lasers, you can afford the lower-priced goggles. Where would you rather spend your lasers-money? Good expensive lasers, or goggles?

Wicked’s goggles work well for the wavelengths they’re designed for. These pics compare what the goggles look like to your eyes, and what they look like to infrared laser light:
Goggles for different lasers
Guess which ones are for IR Lasers
If you were relying on goggles for 532nm (the orange/red lenses) and your laser had lots of IR in it… well you get the point right?

Ok sure, the weak green laser might burn pretty good because it’s got all that IR in it. But it will only burn stuff good up close, because the IR isn’t well-collimated. And you might be slowly and unknowingly losing your eyesight, every time you use the laser!

See, there are no pain receptors at the back of the eye. You can’t see the IR so there is no blink response or aversion response. And the brain is very adept at compensating for partial vision loss, by filling in the blank spots with information from the opposite eye. Most people don’t even know they’re born with a 10 degree blind spot in both eyes (where the optic nerve enters) because the blind spot in the right eye is compensated with data from the left, and vice versa. So little bits and pieces of your vision might be slowly going away, permanently, and by the time you realize it, it is far too late to do anything! This is why having IR mixed in with your green laser is unsafe.

Knowledge Is Power

Ok. So I have established that my cheap green laser has a high initial peak but then quickly tapers off, and I am pretty sure it has no IR filter. A few more tests pretty much confirmed the IR filter situation: I took photos of the dot, using a DV Camera in normal and in ‘nightshot’ mode. In ‘nightshot’ mode it can see near IR light, and the results were pretty conculsive, and obvious.
IR halo around green dot
Here you can see the IR ‘halo’ clearly visible around the green dot. The dot is distorted and stretched because it is being refracted through a cheap plastic prism.

Still learning more, I finaly found out what brand-name the laser is appearantly made by. It’s a NewWish, which are a new manufacturer in China. The manufacturer probably aren’t trying to be malicious; appearantly they’re relatively new and they just produce what is ordered. If the distributor wants to save a dollar or whatever by omitting the IR filter, that’s them, not the maker’s fault.

What is bad of course are all the guys on ebay and elsewhere, hawking these things, and they don’t even know about the potential hazards. Or if they know, they don’t care.

Fixing It

Ok, so I’ve got a laser which is potentially dangerous to me and others around me. I smartened up and ordered a WL Fusion 125mW but in the meantime I’m not just going to throw out the cheap green laser. What to do?

Obviously the answer is to add an IR filter. The caveats: If it is just a cheap green pointer, then adding the IR filter will make it safe, and also reduce it to being just a cheap pointer. No burning power, no balloon popping. Just boring old safety. But, these are the risks you run when you buy on the cheap.

So, where to get an IR filter, and how to know if it’s working? Edmunds Optics sells IR filters that cut-off just over 700nm and also pass over 90% of the green wavelengths, so they’re a good choice. A bit pricey though, at $40-ish for a 12.5mm size. Talk about adding insult to injury, eh? Buy an overpriced unsafe laser, then spend another $40 to make it safe and take all the fun out of it.
IR filter

I’m still looking for cheaper sources…crap there’s that word again, ‘cheap’. Ok, here’s what I did. I have a lot of electronics junk. I dug up an old USB web cam from my junk box. Web cams, in fact all digital camera type devices, incorporate an IR filter of some kind. Why? Their image CCDs are very sensitive to IR light. If there were no IR filter all their pictures would look funny, i.e. would look different than we see the world, because they see the IR and we don’t. This webcam, new, cost me about $40. But it was worth nothing today, so I disassembled it, got the lens carrier out, and removed the lens. The IR filter was square, about 12.5 x 12.5 mm, and was glued into the plastic lens holder. Before trying to get it out, I figured to test it first.

Note: The IR filter is blocking IR from outside, getting into the camera. So the side of the filter that faces out of the camera is the side you want to face into the laser. Incase it makes a difference, and I think it does.

So I slid the lens holder over the laser and got out my trusty LaserCheck. If it works, I will get a realistic reading. If it doesn’t, I’ll get a nutsy reading like I did before.


And…it worked! I got a sensible reading! I proceeded to take a series of test readings, at the three wavelengths, with the filter and without:

Wavelength No Filter With Filter
532 nm 401.0 mW 52.1 mW
808 nm 35.4 mW 3.68 mW
1064 nm 64.1 mW 8.16 mW

Well, now this is interesting! At 808nm, the IR is reduced by about 90%. And at 1064nm the IR is reduced by about 87%. It’s impossible to know how much the green is reduced, since we can’t get a good reading of just the green without a filter. But 50mW is still acceptable – a heck of a lot better than a 5mW pointer anyways…?

So, I pried the IR filter out of the webcam’s lens holder and (keeping track of which side was which) I used a little medium-strength lock-tite to affix it inside the aperture cover of the green laser. Now my green laser has an IR filter! Yippee! Now it’s reasonably safe!

Here’s a closeup of the IR filter, glued into the laser’s aperture cap:
IR filter in place

Obviously the IR filter I am using, was never designed to block such intense sources of IR, so there is bound to be some IR leakage. Who knows, the filter might even break down at some point, so I will test it periodically and find out.

But, what about the other problem? The power spike then rapid loss? Well now I can get accurate measurements, so it must be time for another chart:

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

Oh… Uh… Ok. So my 80mW laser has an initial peak of 125mW. Yeah that’s good. That’s why it will burn a match or pop a balloon almost instantly, when first turned on.

The rest of the numbers aren’t so great though, are they? I didn’t bother to test the reading past 15 seconds, I don’t really want to know. I guess the good news is, if I want to let my cat chase the green dot around, I just have to leave the laser on for half a minute first, then it’s probably safe for her to chase after that.

Footnote Regarding the Measurements:
The LaserCheck wavelength setting simply adjusts a ‘formula’ that the LaserCheck uses to calculate power – it does not filter anything. So setting it to 808 doesn’t just measure the 808 light and ignore the other lines, it simply measures everything and assumes it is all 808nm. So the readings are not assumed to be absolute or completely accurate – I have neither the experience or equipment to measure the relative strength of the separate lines. This is merely the best I can do, with the tools and experience I have at home in my livingroom. Your mileage, as always, may vary.


With the IR filter infront of the laser, the IR ‘halo’ is completely gone now, as visible in these Before and After shots:
IR halo around green dot
IR image: No IR Halo
Both images taken with the DV camera in Nightshot mode, the dot at about 3 feet, after reflecting through a cheap plastic prism (the cause of all the deformation and ‘star’ effects is the prism).

So, not really the great deal I initially thought. The cost of the laser, the cost of the IR filter I had to add, and the final results showing the under-achieving performance, all add up to… yep, that’s right: If it seems too good to be true, it probably is!

I should add: I’m not bitter or angry. I’m not upset at being cheated or ripped off. I took the chance, I bought a cheap laser from an unknown dealer on ebay. I’m dissapointed, but mostly in myself for letting myself get sucked in by the too-good-to-be-true vibes. I also have to acknowledge the educational aspect: it was my first green laser, my first ‘high power’ laser, and it has inspired me to learn quite a bit about DPSS frequency doubled lasers, IR filters, etc.

Save your money, and buy your lasers only from reputable dealers – where there is a warranty, a returns policy, and some level of responsibility.

I’ve shared my experiences with you all, so you can hopefully learn from them, save your money, save your eyeballs, and play safe!

The Fine Print
Information provided on this page is based on my own personal experiences. Although I purchased my Cheap Green Laser at Ebay, I have not identified the individual seller. Outside of the general recommendations given on this page I won’t warn against any specific laser or brand. I suggest laser buyers accept the responsibility of doing their homework before making a purchase, as much as I suggest laser sellers do the same and learn about the products they are selling.