Ive always been fascinated by lasers they are just such neat devices, the only problem is after a while you get a little bored just shining them at things. I always wanted the 007 laser that will just slice through anything, while this instructable wont give you that but it will let you easily slice through the black trashbag or electrical tape that Dr. No has tied you up with. All you need to be able to do it is a cheap 5mw laser from ebay and a small lens.
Dont expect crazy amount of power from this just enough to make dark plastics smoke, pop dark balloons from close range, and maybe if youre lucky light a black match.
Step 1: How It Works
Seeing this diagram might help you understand why a lens will seemingly increase the amount of power a laser puts out. Its clear that it doesnt actually increase the amount power it just focuses it at a specific point, this is one drawback to this burning method because your laser wont behave like a normal laser point after this because past the focal point your beam will diverge, acting more like a flashlight. This is why I wanted to make my lens attachment removable so I can go back to a normal laser pointer whenever I want to.
Which laser to use? In my experience the best bang for you buck is to get the 405nm blue/violet laser not only does it look awesome, change color when it hits light colored clothing, and light up glow in the dark objects, but according the second diagram because its wavelength is shorter it also has higher energy than the other two. However another thing to consider is the mW's your laser produces I believe given the same mW a violet laser will burn the best but a 40mW green is probably more powerful than a 5mW violet. Its really up to you, what you have, what you want to do with it, what you want to spend, and whats legal where you live. I found all three of my lasers for $15.00 on ebay so decided to try all three.
Step 2: Parts
To make a burning laser the most important part is the laser, I got three; a red, a green, and a violet/blue. They are all rated at 5mw although I do not have a meter to verify this. Wavelengths are 650nm, 532nm, and 405nm respectively.
The other critical piece you will need is a lens, I am no expert but I believe the lens should be convex I explain in the why it works step.
The last part is how you will attach the lens to your laser I show two ways in this instructable first is the dead simplest just electrical tape it onto the end, this is the fastest way to get burning and is a good thing to try out if you want to decide if its worth it making a better mount.
After playing with the electrical tape I decided I wanted a nicer looking and more durable yet removable attachment method so I turned an adapter out of delrin on my lathe. You can really use your imagination for this part, you can use anything you have around you, in one of my videos seen in the last step you I made an adapter out of an old magic marker.
Step 3: Get Your Lens
Find a source with a relatively high quality convex lens plastic is preferable but glass will work also(thanks merlinjim). It only needs to be as wide as your lasers beam. I found that the front lens on these same cheap ebay lasers works quite well so I found a dead green laser and using needle nose pliers simply unscrewed it.
Step 4: Attachment (electrical Tape)
Dead easy, just line up the plastic housing and tape away. Electrical tape is nice because it holds strong enough and looks decent.
Step 5: Attachment (delrin)
This creates a much more professional look but in turn requires much more work, the nice thing is it is easily removable and can be used on any of these lasers.
The design varies based on the type of lens you use and what size it is, for me I just cut the lens off of the rest of the housing and drilled a hole for it in the delrin. Then I bored a hole that was a loose press fit onto the silver part on the front of the laser, it was a fun and easy project because delrin is so nice to machine.
In the final picture you can see magic marker lens holder a made a few years ago, just to show you can make just about anything work.
Step 6: Burn
In the first video it appears that the green is the weakest this is because I had been using the green the most and wore the batteries down.