Re: problems with beaming

[T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)]

To Lee and Rex,

Thank you for clarifying the hidden peculiarities of a laser. To make sure
that I have understood everything, I will summarize what both of you explained:

There are two effects playing a role:
1. Diffraction (spreading and interference of the beam by a "small" aperture)
2. Non-parallel beam (attenuation because of the inverse square law)

I like to clear a equivocality about my term non-parallel, I do not mean a
divergent beam since I assume not all "lightrays" of the beam will have
their origin into a single point. So I mean that it is a higly directional
beam build of slightly diffuse "lightrays".

Finally I like to ask a few questions, I hope they are not to specialistic:

I assume that smaller and longer lasers will decrease effect 2, can one of
you confirm this?

To solve effect 1 there is no other solution than to increase the aperture.
I only wonder, can a laser be made thicker without much side effects? (Does
it also mean that it should become longer?)

If know a laser needs to be "stimulated" before it can emit (hence the
name), but how is that done? I know that in earlier days they use a flashing
light for a ruby laser, but how is it done today?

I've heard of semi-conductor lasers, do these have an aperture too? (and are
the effects the same as for "normal" lasers?)


Timothy


P.S. to Lee, in your letter you wrote the following formula:
      sin(theta)~theta=1.22*lambda/d
     What does the ~ mean?