according to US Patent Number: 5371756 direct blue-green laser diodes can be manufactured using CdZnSe, ZnSSe, and ZnSe, for each of the p-type clad layer and the n-type clad layer contains at least one of ZnSSe, ZnSe and ZnMgSSe. This direct blue-green laser diodes would be cheaper to manufacture compared to diode pumped solid state lasers using high-power infrared diodes and then doubling or tripling the frequency to produce visible light.
Here are the patent claims of the said patent:
1. A semiconductor blue-green light emitting device in a double heterostructure configuration, comprising:
a substrate;
a light emitting layer which contains at least one of CdZnSe, ZnSSe, and ZnSe;
a p-type clad layer and an n-type clad layer each of which contains at least one of ZnSSe, ZnSe and ZnMgSSe and which are provided at two sides of said light emitting layer, respectively;
a cap layer of (Al.sub.X Ga.sub.1-X).sub.0.5 In.sub.0.5 P (0.ltoreq.X.ltoreq.1) which is deposited on said clad layer located at an opposite side of said light emitting layer from said substrate; and
a contact layer of Al.sub.X Ga.sub.1-X As (0.ltoreq.X.ltoreq.1) which is deposited on said cap layer.
2. A semiconductor blue-green light emitting device according to claim 1, in which said cap layer and said contact layer are made of organic group V materials.
3. A semiconductor blue-green light emitting device according to claim 1, which further comprises a dielectric insulating layer which is formed on said contact layer and which has a stripe opening, and a metal electrode which is provided in said stripe opening.
4. A semiconductor blue-green light emitting device according to claim 1, in which said clad layer disposed at the opposite side of said light emitting layer from the substrate is configured in a mesa stripe with its two side surfaces and two laterally positioned surfaces being covered with dielectric insulating films, respectively.
Thursday, October 25, 2007
The story of cheap Green Laser Pointer
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.
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.
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:
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.
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.
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.
Results
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:
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.
Summary
With the IR filter infront of the laser, the IR 'halo' is completely gone now, as visible in these Before and After shots: 
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!
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.
Retinopathy from a Green Laser Pointer
Arch Ophthalmol. 2005;123:629-633.
Objective To report retinopathy following exposure to light from a commercially available class 3A green laser pointer.
Methods A 55-year-old woman with a ring melanoma was scheduled for enucleation. The eye (visual acuity 20/20) had a healthy-appearing macular retina. The retina was exposed to light from a commercially available class 3A green laser: 60 seconds to the fovea, 5 minutes to a site 5° below the fovea, and 15 minutes to a site 5° superior to the fovea. Color photographs were obtained before and after exposure. The eye was enucleated 20 days after exposure.
Results Laser power measurements averaged less than 5 mW. Retinopathy was observed 24 hours after laser exposure. This was characterized by a yellowish discoloration at the level of the retinal pigment epithelium (RPE) in the subfoveal region and at the site superior to the macula where the retina received 15 minutes of laser exposure. Each site developed granular changes at the level of the RPE within 5 days of exposure. Histologic study showed RPE damage in the exposed subfoveal and parafoveal regions.
Conclusion A class 3A green laser pointer caused visible retinopathy in the human eye with exposures as short as 60 seconds.
Author Affiliations: Department of Ophthalmology, Mayo Clinic, Mayo Foundation, and Mayo Medical School, Rochester, Minn.
Experiments for High Power Green laser Pointer
Conducting experiments with laser pointers is both educational and loads of fun. Listed below are some basic experiments you can perform with green laser pointers. Please when experimenting, always keep safety foremost in mind.
Thermal experiments
Burning plastic
This is the easiest of the thermal experiments to perform and only requires a 55mW laser pointer.
Instructions/tips:
-Use thin black plastic such as shopping bags.
-Hold the laser pointer very close to the bag and rest it on something solid to keep the beam steady.
-The first sign of success will be tendrils of smoke from the point you are aiming at.
-When you’ve finished, holding the plastic up to the light should reveal small pin pricks burnt into the plastic.
Bursting or popping balloons
Laser pointers of roughly 75mW or higher in power can pop dark or black colored balloons.
Instructions/tips: Dark or black balloons are best because they are better at absorbing green light. White or green balloons will have too much reflection and the absorbed energy will not be enough to pop the balloon. If you don’t have any dark/black balloons, you can use a sharpie (black texta) to put a black spot on the balloon that you can aim the laser at. Make sure the balloon is fully blown up because if it is not blown up properly and lacks tension, popping it will be difficult.
Lighting matches
This is harder to do than popping balloons and requires a minimum of 95mW or higher laser pointer.
Instructions/tips:
-As with balloons, the color of the match head is also important. If the color is too light such as white, too much energy from the laser beam will be reflected and there will not be enough energy remaining to light the match. Black or dark red matches are ideal. You can also use a sharpie to darken the match head.
-Make sure both the laser pointer and the match are fixed and not moving
-don’t hold the laser pointer too close to the match or you may get ash and debris on the laser pointer lens.
Cutting black electrical tape
Another one of the more difficult burning experiments that requires a laser pointer of at least 95mW in power.
Tips/instructions:
-Attach the loose end of the tape to a fixed point such as the edge of a table then leave roughly 10 cm of tape with the tape roll suspended at the end. The tape roll will create tension that makes cutting the tape easier.
-keep the laser steady and aimed at the edge of the tape.
Mirrors
Experiments with mirrors can range from the very basic to the very advanced and are only limited by your imagination. The advantage of mirror experiments is that there are no specific power requirements and low powered laser pointers will be just as effective (but less visible) as the higher powered laser pointers.
Laser accordion
Very easy to do and can be visually very impressive.
Instructions/tips:
-Carefully line up two rectangular mirrors of similar size parallel to each other.
-change the angle of the laser pointer to the mirror to create more beams between the mirrors
Measure your pulse
Sounds difficult but is actually very easy to do.
Instructions/tips:
-attach a very small mirror (no more than 4cm in diameter) directly over the inner part of your wrist where pulse is normally measured. Use a small round object like blue tack or chewing gum (messy but effective) to attach the mirror to your wrist.
-reflect the laser pointer beam of the mirror onto a smooth surface such as a wall at least 4 meters away.
-if the laser pointer and your wrist are held steady, the rhythmic movements in the reflected image on the wall will be your pulse.
Security alarm
This experiment is an extension of the laser accordion experiment.
Instructions/tips:
-at a security point such as an exit/doorway or a hall way, line up two rectangular mirrors and create a grid of laser beams. The beam should be aimed to fall on a photoelectric detector that is connected to an alarm.
-once the beam is broken, the alarm will be activated.
-IR lasers could be used to create an invisible security alarm.
Cool beam effects
There are a number of experiments ranging from very simple to quite advanced that can create beautiful beam effects such as the ones listed below.
Ice
The crystalline structure of ice is full of hollows, gaps and imperfections that will scatter and diffract the laser beam.
Laser drawing and writing
Instructions/tips:
-make sure the exposure time on your camera is at least 2 seconds
-aim the laser pointer beam at a smooth non reflective surface with a good contrast
-then use the beam point to write/draw pictures
-use smoke or fog to provide additional effect
Bend light
Using wave propagation theory, you can actually bend light from your laser pointer and see it clearly.
Instructions/tips:
-Aim the laser at a smooth surface 4 meters away such as a white wall
-Use an object with a very precise smooth edge such a new razor blade.
-partially block the laser beam with the edge and note the interference patterns produced.
-the patterns will not be flat or smooth. Instead there will be a diffraction pattern
Moving objects
No kidding, high power laser pointers have a beam powerful enough to move objects. At least they can move the vanes in a Crookes radiometer.
-instructions/tips:
-you need a Crookes radiometer that has a complete vacuum in the globe and the vanes have virtually frictionless support.
-aim the laser pointer beam at the silver side of the vanes and they should start to move very rapidly.
Beam splitting
There are various methods and numerous pieces of equipment that can split the beam of a laser. This is one of the simplest methods.
Instructions/tips:
-using microscope slides, split the laser pointer beam by angling the beam on the slide.
-for really spectacular results, you can use a diffraction grating.
Home made laser microscope
The humble green laser pointer is versatile enough to be used as a very basic microscope.
Instructions/tips:
-put a drop or two of water on a transparent piece of glass such as a microscope slide.
-shine the laser through the glass onto a smooth surface such as your roof. You’ll see a magnified image of the water and its contents on your roof.
Time tunnel
Laser pointers can be used to create a light tunnel reminiscence of Doctor Who and several other famous science fiction programs
Instructions/tips:
-you attach a mirror to an electric motor at a slight angle.
-aim the laser beam on the mirror when the motor is turned on and the laser beam will spin around itself to create a laser cone or tunnel
source: www.dragonlasers.com
Thermal experiments
Burning plastic
This is the easiest of the thermal experiments to perform and only requires a 55mW laser pointer.
Instructions/tips:
-Use thin black plastic such as shopping bags.
-Hold the laser pointer very close to the bag and rest it on something solid to keep the beam steady.
-The first sign of success will be tendrils of smoke from the point you are aiming at.
-When you’ve finished, holding the plastic up to the light should reveal small pin pricks burnt into the plastic.
Bursting or popping balloons
Laser pointers of roughly 75mW or higher in power can pop dark or black colored balloons.
Instructions/tips: Dark or black balloons are best because they are better at absorbing green light. White or green balloons will have too much reflection and the absorbed energy will not be enough to pop the balloon. If you don’t have any dark/black balloons, you can use a sharpie (black texta) to put a black spot on the balloon that you can aim the laser at. Make sure the balloon is fully blown up because if it is not blown up properly and lacks tension, popping it will be difficult.
Lighting matches
This is harder to do than popping balloons and requires a minimum of 95mW or higher laser pointer.
Instructions/tips:
-As with balloons, the color of the match head is also important. If the color is too light such as white, too much energy from the laser beam will be reflected and there will not be enough energy remaining to light the match. Black or dark red matches are ideal. You can also use a sharpie to darken the match head.
-Make sure both the laser pointer and the match are fixed and not moving
-don’t hold the laser pointer too close to the match or you may get ash and debris on the laser pointer lens.
Cutting black electrical tape
Another one of the more difficult burning experiments that requires a laser pointer of at least 95mW in power.
Tips/instructions:
-Attach the loose end of the tape to a fixed point such as the edge of a table then leave roughly 10 cm of tape with the tape roll suspended at the end. The tape roll will create tension that makes cutting the tape easier.
-keep the laser steady and aimed at the edge of the tape.
Mirrors
Experiments with mirrors can range from the very basic to the very advanced and are only limited by your imagination. The advantage of mirror experiments is that there are no specific power requirements and low powered laser pointers will be just as effective (but less visible) as the higher powered laser pointers.
Laser accordion
Very easy to do and can be visually very impressive.
Instructions/tips:
-Carefully line up two rectangular mirrors of similar size parallel to each other.
-change the angle of the laser pointer to the mirror to create more beams between the mirrors
Measure your pulse
Sounds difficult but is actually very easy to do.
Instructions/tips:
-attach a very small mirror (no more than 4cm in diameter) directly over the inner part of your wrist where pulse is normally measured. Use a small round object like blue tack or chewing gum (messy but effective) to attach the mirror to your wrist.
-reflect the laser pointer beam of the mirror onto a smooth surface such as a wall at least 4 meters away.
-if the laser pointer and your wrist are held steady, the rhythmic movements in the reflected image on the wall will be your pulse.
Security alarm
This experiment is an extension of the laser accordion experiment.
Instructions/tips:
-at a security point such as an exit/doorway or a hall way, line up two rectangular mirrors and create a grid of laser beams. The beam should be aimed to fall on a photoelectric detector that is connected to an alarm.
-once the beam is broken, the alarm will be activated.
-IR lasers could be used to create an invisible security alarm.
Cool beam effects
There are a number of experiments ranging from very simple to quite advanced that can create beautiful beam effects such as the ones listed below.
Ice
The crystalline structure of ice is full of hollows, gaps and imperfections that will scatter and diffract the laser beam.
Laser drawing and writing
Instructions/tips:
-make sure the exposure time on your camera is at least 2 seconds
-aim the laser pointer beam at a smooth non reflective surface with a good contrast
-then use the beam point to write/draw pictures
-use smoke or fog to provide additional effect
Bend light
Using wave propagation theory, you can actually bend light from your laser pointer and see it clearly.
Instructions/tips:
-Aim the laser at a smooth surface 4 meters away such as a white wall
-Use an object with a very precise smooth edge such a new razor blade.
-partially block the laser beam with the edge and note the interference patterns produced.
-the patterns will not be flat or smooth. Instead there will be a diffraction pattern
Moving objects
No kidding, high power laser pointers have a beam powerful enough to move objects. At least they can move the vanes in a Crookes radiometer.
-instructions/tips:
-you need a Crookes radiometer that has a complete vacuum in the globe and the vanes have virtually frictionless support.
-aim the laser pointer beam at the silver side of the vanes and they should start to move very rapidly.
Beam splitting
There are various methods and numerous pieces of equipment that can split the beam of a laser. This is one of the simplest methods.
Instructions/tips:
-using microscope slides, split the laser pointer beam by angling the beam on the slide.
-for really spectacular results, you can use a diffraction grating.
Home made laser microscope
The humble green laser pointer is versatile enough to be used as a very basic microscope.
Instructions/tips:
-put a drop or two of water on a transparent piece of glass such as a microscope slide.
-shine the laser through the glass onto a smooth surface such as your roof. You’ll see a magnified image of the water and its contents on your roof.
Time tunnel
Laser pointers can be used to create a light tunnel reminiscence of Doctor Who and several other famous science fiction programs
Instructions/tips:
-you attach a mirror to an electric motor at a slight angle.
-aim the laser beam on the mirror when the motor is turned on and the laser beam will spin around itself to create a laser cone or tunnel
source: www.dragonlasers.com
808nm Diode from Green Laser Pointer
While fitting a heatsink to the outside of a green laser pointer I broke the cyanoacrylate glue holding the driver board to the brass housing. I did not think this was a problem. I was quite wrong. A laser diode is very fragile inside. I thought I only had to be careful with heat and static shock. Here are some photos of the inside of a dead 808nm laser diode.
This is the diode at 10x.
This is the laser diode chip. It is about .020 inch square! It sits on the front edge of the end of the can. I did not find it with my naked eye. I thought the laser diode was lost until I looked at 60x.
This is the photo diode at 60x.
This is the laser diode at 60x from the front. The two lines are for alignment and are about .025 inch apart.
Here is a picture of the Laser Diode and the pin it used to conect to. The wire hanging on the pin was soldered to the laser diode. If you look closely the blob of solder is still on the end of the wire.
Here is the photodiode. Notice the wire soldered to the corner. The ring is the strain relief for the pin. The pin was pulled out of the diode.
I could not see the wire on the pin with my naked eye but with a little help it is still there!
This is a strand of hair to show the scale involved.
Can this be repaired?
Here is Chris Luebner's method. I don't think I will try. Without a 60x stereo microscope the method he describes would be very difficult.
Looks like the bonding wires got yanked off the diode, set it up so the diode is facing a cm or so from some white paper and tie the can to the positive side of 2 d cells hooked up in series.
Then add a 2 ohm resistor in serieswith the negative side of the battery and gently touch the top of the diode (with the gentleness and steadyness of a neruosurgeon) with the free reistor lead to see if it still lases.
You should see a dim red elipse if it still is alive, be sure you are more than a foot away when you view it and do not do so for very long. Technically it is defused to an eye safe value after a mere couple inches when shone on paper, but it's still VERY very bright and you will ge a nasty headache because your eyes still _FEEL_ it as if you are looking at a 1/2 watt argon laser.
If you have an IR sensitive camera or night vision scope handy you can use that to view it, be sure that you have the pinhole attenuator for the NV scope or it will die.
If the diode is still good you may try a soldering pin (Yes, really smd tips are much too big! Wire wrap a brass pin to a 15W temp controlled soldering pen tip.) with indium tin solder. To re-attach a wire try to move the bonding wires using a cactus needle to the diode, or if they are too far gone a tiny piece of wire like a single strand from a cheap bad headphone wire works well. Never use any other solder but indium/tin on the pin, and never let it get very hot and allways pre-heat your part on a hotplate before soldering it or it will fail to bond if you don't.
If all else fails I do have some fiber coupled 1-2W laser pump diodes that i'll sell ya for 125.00 each. The c-mount diode inside has a circulaser lens that makes the beam round and would be ideal for pumping a dpss crystal.
hope this helps, Chris
source: http://www.designerinlight.com/holo/dld.htm
DIY Green laser pointer power meter
Here is a simple cheap and accurate way to measure laser output power.
Place the LED into the hole of the laser head, fire the laser and read the value on the ampmeter. Use this formula to obtain the optical power : P = uA / 2.8
Note : it must be a green coloured LED for correct values (not a transparent green LED). Radio Shack sells them.
Readings : 14 uA for 5mW, and my pointer measured 310uA for 110 mW
Required material :
- A green LED like this :
- An ammeter with a 1000mA range
Connect the ammeter to the LED as shown in diagram.
Place the LED into the hole of the laser head, fire the laser and read the value on the ampmeter. Use this formula to obtain the optical power : P = uA / 2.8
Note : it must be a green coloured LED for correct values (not a transparent green LED). Radio Shack sells them.
Readings : 14 uA for 5mW, and my pointer measured 310uA for 110 mW
source: http://www.angelfire.com/co3/coinsnxs/
eBay Laser Pointer Scam Exposed
The scam itself is based on the type of light given out by the laser pointer, the way power is measured, changes made to the laser pointer and ignorant and/or dishonest sellers.
Type of light
These lasers are advertised as green lasers and should give out green light and only green light. That how ever is not the case. Virtually all supposedly high power green laser pointers on ebay emit a combination of green light with a wave length 532nm light and infrared light with wavelengths of 808nm and 1064nm light.
All genuine high power green laser pointers have a built in filter that prevents them from emitting infrared light. The laser pointers on eBay are missing these filters which have either been removed or deliberately manufactured with out. Removing the infrared filter from a laser pointer increases its power and makes it a lot more dangerous.
Take a 240mW laser pointer commonly found on eBay as an example. This laser pointer is likely to have only 40mW of green light with the remaining 200mW of light being infrared light. Customers pay for laser pointers with 240nm of green light and only get laser pointers with 40mW of light. Effectively cheating them of 84% of their money.
The other problem with missing infrared filters is the lasers are very dangerous. Infrared light spreads out like a torch beam compared to green light which is in a narrow beam. Green light being visible can be avoided but the Infrared light because it is invisible cannot be avoided. Most safety glasses that protect against green light are completely transparent to infrared light. This means a person wearing safety glasses and using one of these lasers is less likely to avoid the beam and much more likely to suffer damage to their eyes.
Measurement of power
The power of most laser pointers will peak in the first few seconds then stabilize at a level much lower than the peak. Reputable sellers will give the average power as the advertised power. Ebay sellers on the other hand use the peak power as the advertised power. This is very deceptive because it misleads people into thinking the laser is much more powerful than it really is.
Modifications
These laser pointers are only designed to handle powers from around 5mW to 10mW. The sellers modify the laser pointers by increasing the power from the batteries to the laser diode so the diode emits a more powerful laser beam. The problem with this that the diode is not built to handle the higher power and will have a much shorter life cycle and is likely to burn out. Many ebay lasers lose power or burn out completely in a matter of hours or even minutes. The lens in the laser pointer the acrylic coatings are also not designed for the increased power and are likely to damaged with reduced performance or fail completely.
These eBay sellers are not laser experts and generally have little or no understanding of the laser pointers they sell. This means they are not able to give qualified advice or recommendations and the level of support and service they can provide is minimal. Their general response to customers when there are problems with laser pointers is to ship it back for a replacement. Given that the cost of the laser is not much more then the cost of shipping it, most customers cut their losses at that point.
Possible remedies
Laser pointers with powers over 5mW are classified as hazardous goods and are not allowed on eBay. If you have been scammed by one of these sellers, you can threaten to report them to eBay and they may have their account suspended or even closed.
If you paid with PayPal, you can also open a dispute for goods not as described. The dispute may not be decided in your favor but most sellers are willing at that stage to issue you a refund. If you paid with a credit card, you can start a charge back with your credit card company in a similar manner with a greater chance of success than PayPal.
The last option is to bluff. Claim that you will contact eBay, the police and the government department in charge of consumer affairs in their country if they do not issue you with a refund. Considering they are selling an item prohibited by eBay and illegal to sell (legal to possess) in a number of countries, this bluff is very effective.
This article is provided courtesy of Dragonlasers at http://www.dragonlasers.com
Article Source: http://EzineArticles.com/?expert=Frank_Smith
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