John S. Denker wrote:
> (snip...)
> 2b) If you and/or your students are not up-to-speed on density
> matrices, the following approach may help:
>
> *) To make unpolarized light, combine vertical light with horizontal
> light _with an arbitary adjustable relative phase_. (If you
> combine them with a definite phase, you don't have unpolarized
> light, you just have some cockeyed polarization.)
>
> *) Perform whatever propagation, filtering, and/or basis changes you
> like.
>
> *) Calculate the intensity by taking the absolute-square, taking the
> phase into account according to the usual rules.
>
> *) Now take the average over all phases.
>
While this prescription (including an arbitrary phase, then averaging at
the end) works mathematically, I've never been completely <satisfied
with/confident in> my own *physical* picture of unpolarized light. How
can the phase vary without also varying the wavelength?
The best I think I've come up with is the superposition of many wave
packets (photons?), each with a randomly selected but definite
polarization. Each packet has a spread of wavelength, of course, but at
least they all have the same average wavelength.
Is that a good picture? Anyone have anything better? Can a single
photon be unpolarized?
--
Dr. James McLean phone: (585) 245-5897
Dept. of Physics and Astronomy FAX: (585) 245-5288
SUNY Geneseo email: mclean@geneseo.edu
1 College Circle
Geneseo, NY 14454-1401