Step 1: Prepare Your Lasers.
For this project we used an assortment of continuous operation lasers from Laserglow.com's Brightline Series. The lasers ranged in power outputs of 25 mW to 40 mW, but you can use lowered powered units, but it won't be as awesome.
We removed the mounting brackets and prepared them with matching power supplies to be placed on the tree. If you don't have access to continuous operation lasers you can use a regular laser pointers by taping the button so it stays on. Your battery will die eventually, but you'll have a temporary solution to create your own display. Green laser pointers can be purchased from both Laserglow.com and Novalasers.com.
Step 2: Attach Diffraction Gratings to Your Lasers.
As we did in the Laser Pumpkin Instructable, we used electrical tape to attach Diffraction Gratings to the end of our lasers. Diffraction Gratings that give multiple beams are the best for this project. We tried to use a wide variety of Diffraction Gratings to show how different ones create different displays. Diffraction Gratings can be purchased from Novalasers.com under the Shop Nova section.
Step 3: Attach Lasers to the Christmas Tree.
We used black twist ties to attach each laser module to a different branch on the tree. Twist ties allowed us to easily move the lasers to create better displays and they did a great job of holding the unit to the branch. You can use string or tape, but I think twist ties would be the best bet.
We spread out the lasers to have contrasting colours between the red and the green lasers, and we also tried to have a variety of Diffraction Gratings to create a more dynamic display.
Step 4: Adjust the Lasers
After the lasers are attached and you've connected power you may not be immediately satisfied with the display. Once the lasers were active we were able to decide how they should be spread out to effectively create an interesting display. It's important to note that lasers displays appear more dynamic when colours are contrasting each other. Two green lasers beside each other did not look as impressive as a red and a green nearby each other.
Step 5: Add Your Star.
We used Laserglow.com's 2.4 Watt Laser Projector that we were lucky enough to have out our disposal. Naturally, you can use whatever you'd like for the star/angel, but I would suggest using something that appears drastically different from the rest of the tree. If you are using primarily green and red lasers, than a yellow or a blue might be a good idea for your star. If you happen to have a yellow or a blue laser at your disposal than try it with a diffraction grating pointing up and you should be able to create a unique star for the top of your tree.
Step 6: Add Some Fog or Smoke.
Keep in mind that your tree will look best when all the lights are completely off, so if you wish to add ornaments be sure to showcase the ones that reflect laser beams and are visible in the dark. Adding smoke or fog now will reveal all beams projecting from the tree and truly make your Laser Tree come to life. Fog can be purchased from Novalasers.com.
Be sure to check out our Flickr page for more photos and other laser related stuff!