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Re: problems with beaming
- To: KellySt@aol.com, kgstar@most.fw.hac.com, stevev@efn.org, jim@bogie2.bio.purdue.edu, zkulpa@zmit1.ippt.gov.pl, hous0042@maroon.tc.umn.edu, rddesign@wolfenet.com, David@InterWorld.com, lparker@destin.gulfnet.com, DotarSojat@aol.com
- Subject: Re: problems with beaming
- From: T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)
- Date: Fri, 12 Apr 1996 15:21:38 +0100
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?