For a laser tube without mirrors, you might try Melles-Griot.
Regards,
Steven Ratliff
Northwestern College
"Timothy S. Sulllivan" <Timothy.Sullivan@AXOM.COM> on 12/13/99 10:24:32 PM
Please respond to "phys-l@lists.nau.edu: Forum for Physics Educators"
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cc: (bcc: Steve T Ratliff/Nwc)
Subject: Re: Laser question
I hesitate to step in when a real expert might appear, but...
I worked with an Ar ion laser last year. There the mirrors where removable
for cleaning. If you removed the rear cover, laser light shone out the back
end as well. However, by far the most energy went out the business end. My
understanding is that while you would like the back mirror to be perfectly
reflective, real interference mirrors are not. For an interference mirror,
the non-reflected part is transmitted out the back and that is what the
student is seeing. Interference mirrors are still more reflective than
silvered mirrors, but the non-reflected energy when using a silver mirror is
taken up in heating the mirror and is thus not visible. Hence, it appears to
look more like the simplified diagrams of lasers in textbooks.
Complicating the issue is that our eyes are sensitive and adaptive light
sensors. So we are poor at judging relative intensities, especially when we
don't have side-by-side comparisons. So the amount of light coming out the
back of the laser may look like a lot, but I suspect that a power meter
would show that the light being emitted toward the rear of the laser is
relatively small compared to that coming out the front.
Tim Sullivan
sullivan@kenyon.edu
PS Anyone know where I can get a HeNe laser tube without the mirrors? I want
to have adjustable external mirrors to demonstrate to students how aligning
the mirrors produces the lasing action.