# Redirecting light beams from beam splitters

I'm doing a project where I am taking a laser beam and sending it through a beam splitter. As I understand, approximately 50% of the light will go pass through and 50% will be reflected. So this means that half of the total energy of the beam will go one way, and the other half will go the other. The intensity must be halved right? I want to be able to keep on dividing it so that I keep getting twice the amount of laser beams that I have before that are 1/2 the intensity. I want to intersect all the laser beams together at a single point like a gamma knife. I want to demonstrate the gamma knife idea with the aid of some medium, and show that a point of light will be where the intersection is.

My question is, will a point of light be present? Will I be successful in doing this?

What arrangement of mirrors will allow for me to direct all the beams to an intersection point?

Is it possible to use one beam splitter and lots of mirrors to repeatedly send it through the same beam splitter so that I won't have to buy multiple beams splitters?

Of course I want to use the least amount of mirrors and beam splitters to save money...

Can you guys help me think of the arrangement of mirrors to achieve this?

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How about just a focusing lens?

Shine the laser through it and move a card back and forth around the focus to see how the beam area shrinks and the intensity grows.

If you really want discrete beams, you could use a mask right before/after the lens to block out all the light but a few circles.

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I don't want to use a focusing lens because they are bulky and expensive, where as if I were to only purchase a single beam splitter and have a configuration of mirrors to go through it in such a way to divide up the beam... This is what I am in need of help for. – QEntanglement Oct 1 '12 at 19:34
Actually, what would be by far the cheapest and easiest solution, and more closely resemble the real gamma knife would be to just buy a dozen or so cheap laser pointers from a dollar store. Then just arrange them so their beams intersect. – user2963 Oct 1 '12 at 19:47
I agree, however, I'll need A LOT of laser to do this, and I can't control the intensity of the lasers... So when they all intersect, it is difficult to see the "brighter" spot at the intersection... – QEntanglement Oct 2 '12 at 1:14

If working with mirrors and (free-space) beam splitters is not a tight constraint in your project, then an assembly of 1x2 fiber fused couplers could solve your problem.

Purchased in bulk quantities, I have the feeling that a 1x2 fiber coupler may come out to be quite cheap (40-50 EUR). For implementing $n$ stages, you would need ~$2^{n+1}$ such couplers. The best thing about this solution is convenience... there's no alignment required.

In the end, you could use a Nx1 coupler to bring out the light from your $n$ stages into a single fiber and hence, to a single point; though it will probably not be feasible if $n$ is large... Or if it is feasible, it will most likely be quite expensive.

An alternative would be get cheap fiber-collimators and get a single point of light using mirrors titled at appropriate angles.

• I prepared an image to show one possible methodology, but the website unfortunately prohibits me from attaching it.
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