Re: De-polarize light?


"martin+x@xxx" <martin.usenet@xxxxxxxxx> wrote in message
news:1164160956.729998.264680@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
What are the options here? I saw something about mylar film. Will
that work?

Thanks.

Mylar will act like a multiorder waveplate. If you orient its stretched
axis at 45 deg. to incoming linear polarization, the output polarization
state will change somewhat slowly versus wavelength. For a single
wavelength, if you are very lucky, it might act like a 1/4 wave plate and
produce circular polarization. This is still not depolarized, but might be
good enough for some purposes.

Lyot depolarizers are made of two thick birefringent crystals at 45 deg. to
each other, and vary the output polarization very quickly versus wavlength
regardless of the input state.

Wedge depolarizers change the output state versus position in the aperture,
and will work for monochromatic light.

Since un-polarized light is actually just light that takes on random
polarization states versus time, it is impossible to truly de-polarize light
without a time-varying optic. Although, you can argue that something like a
Lyot depolarizer with a retardance much greater than the coherence length of
the bandwidth being detected will be produce essentially depolarized light.

--
Adam Norton

Norton Engineered Optics
Optical design and systems engineering for Silicon Valley and beyond.
http://home.ix.netcom.com/~anorton/

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