buffo
Terms defined...
Let me take a stab at some of these.Originally Posted by Evolve
A "cube" is shorthand for a polarizing beam-splitting cube. Basically it's a hunk of glass about the same size as a sugar cube. (say, oh, about 1 cm high.) If you send a randomly polarized laser beam into it from one side, it will split the beam into two separate beams that have opposite polarization. (one will be horizontal, the other vertical). One beam will continue in the same direction as the incoming beam, while the other beam will be "split off" at a 90 dree angle.
However, you can also use a polarizing beam-splitting cube to COMBINE two laser beams of the SAME wavelength into a single beam. The trick is that the two incoming beams have to be of opposite polarization. (One vertical, one horizontal.) You end up with a randomly polarized beam that is about 90% as strong as the sum of the power output of the two lasers. (The rest is lost due to internal reflections and other losses inside the cube.)
If you look at this picture (from Liteglow's gallery) you can see the two red lasers just up and to the left of the output. The top laser bounces off a mirror set at a 45 degree angle, and enters one face of the polarizing beam-splitting cube. The other red laser goes straight in to another face on the cube. The resulting output beam has nearly all the power of the two separate red lasers. (And the resulting beam next strikes a "dichro", where it is mixed with the blue beam... What a perfect lead-in to your next question!) 8)
A "dichro" is shorthand for a dichroic mirror. That is, a mirror that reflects light at some wavelengths, and passes light at other wavelengths. These are used to combine two laser beams that are of different wavelengths into a single beam. For example, a dichro that reflects green but passes red will allow you to mix the red and green beams, producing a yellow beam. (You can also get just red or just green by turning off the other laser.) Likewise, there are dichros that reflect blue but pass red and green. By using two dichros in series, you can add green to red, and then blue to the red-green beam, ending up with all three primary colors. (This is how most low power white-light projectors work.)
At higher power levels you'll often find one large multi-line ion laser (these are *big* gas lasers with mixtures of krypton and argon that lase at many wavelengths at the same time) rather than three single-line lasers inside the projector. These large ion laser-based projectors use something called a Poly-chromatic Acoustic Optical Modulator (PCAOM) to select individual colors from the rainbow of wavelengths produced by the laser. However, PCAOM's are expensive, difficult to align, and they waste 15% or more of the output power of the laser. Plus they require that all the light be polarized int he same direction. (Not a problem when you're dealing with just one big gas laser, but more of an issue if you're trying to combine beams from several lasers...) Anyway, you rarely see PCAOM's in small projectors. Most people use individual lasers for each color, and dichros to mix the colors together into a single beam. (The color control is done by varying the intensity of each of the three lasers...)
A "Trichro" is simply a carefully constructed optical component that combines two dichros together in a single unit. It has three optical ports on one side where the red, green, and blue beams go in, and a large output port where the resulting white light beam exits. (Note that they also work in reverse... If you send a white light beam in through the output port, you'll get a red beam, a green beam, and a blue beam out each of the respective ports as well.) Have a look here in the gallery for some pictures of a trichro all set up.
Most trichros are surplus units that were harvested from 3CCD cameras. These cameras needed to separate the incoming light into red, green, and blue components before sending each component to it's own CCD. That's what the trichro does. So really, using it to COMBINE three beams into a white light beam is actually using it in reverse from it's original application, but like I said, they're reversable.
An optical breadboard is a flat, stable surface (usually metal, but dense plastic or even wood has been used by some) that has holed drilled and tapped at regular intervals (usually every inch) to make it easy to mount optical components. The optical table is the sturdy, stable surface that the breadboard sits on, though sometimes the terms are used interchangeably.
There are several ways to make a stable optical table, but unless you're going to be making holograms, you don't need that sort of stability. On the other hand, even for a basic laser projector you'll still need some sort of breadboard to mount all your optics on. (Lasers, bounce mirrors, dichros, and galvos all need to be mounted to the same flat surface so you can align them.) You can start with a metal plate and drill the holes as you need them, or just buy a sheet of aluminum and drill all the holes in advance. If you have a PERFECT layout plan, you can just drill the holes you need. But most people like having the flexibility of extra holes if you need to move something, thus the convention of having holes drilled every inch.
There, I can't help you. Fiber optic mounts are a little tricky. I haven't had much experience with this, but perhaps some other members here can help you out.Guides such as how to make your own fiber optic cable attachment to a laser diode would be sweet.
Well, after the "cube" paragraph above, you already know how to do that...In addition, a guide that explain how to take single laser input from diode and split it into two outputs would be sweet too.All you need is a beam splitter. You don't even need a polarizing beam splitter, since you don't care about the resulting polarization. In fact, in a pinch, even a simple pane of glass will work as a beam splitter. Place it at a 45 degree angle, and you'll get a beam reflected off it, plus the main beam will pass straight through. Unfortunately, you'll get reflections of both the near and far side of the glass, which means your reflected beam will have a "ghost" beam right next to it. Try using a cover slip for a microscope slide. (These are *REALLY THIN* sheets of glass that are only about 1 inch square.) They work really well, and because they are so thin, the second reflection off the back of the glass is barely visible. But they break really easily, so be careful.
Hope that helps... Feel free to ask more questions. (Have you looked at Sam's Laser FAQ? Lots of good info in there as well.)
Adam
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