Re: Faraday isolators

[Herbert H Gottlieb <herbgottlieb@JUNO.COM>]

Don't we have a similar situation with  one-way
transmission using diode rectifiers and diode
detectors?  There is greater resistance in one
direction than the reverse direction.

Bob Sciamanda <trebor@VELOCITY.NET> writes:
> Let me try to get this discussion going:
>
> The Faraday isolator is effectively a pair of crossed polarizers for
> the "blocked" radiation.
> The (outside) radiation which enters the isolator, but does not exit,
> is absorbed inside the isolator and raises the temperature of the
> isolator (and the cavity walls of which it is a part).  ( As does the
radiation
> trapped between any pair of crossed polarizers.)
>
> I think the physics of any  polarizing mechanism forbids you, in
> principle, from ignoring such absorption (or equivalent energy
re-direction)
> effects.
>
> I must add that I didn't fully understand your F/S/F scheme.
>
> -Bob
>
> Bob Sciamanda
> Physics, Edinboro Univ of PA (ret)
> trebor@velocity.net
> http://www.velocity.net/~trebor
>
> -----Original Message-----
> From: Carl E. Mungan <cmungan@UWF.EDU>
> To: PHYS-L@LISTS.NAU.EDU <PHYS-L@LISTS.NAU.EDU>
> Date: Wednesday, December 30, 1998 7:06 PM
> Subject: Faraday isolators
>
>
> > It bothers me that Faraday isolators don't obey optical
> reversibility. The
> > fact that looking through one I could see you but you not see me is
> > disquieting. In particular, I don't quite see how to save Kirchhoff's
> law
> > (absorptivity = emissivity) with these gizmos.
> >
> > The arrangement I have in mind is simple. A black sample is inserted
> into a
> > cavity having perfectly reflective walls. Then I make a small window
> in the
> > walls into which I place a Faraday isolator. Now what prevents the
> sample
> > from radiating away energy continuously and cooling down to 0 K? The
> basic
> > idea is so simple I'm sure some of you have thought of it before.
> >
> > To dispense with a couple of objections off the bat:
> >
> > (1) a Faraday isolator only works at one wavelength - okay, put an
> ideal
> > filter in front of it (i.e., one which perfectly transmits a narrow
> > passband and perfectly reflects everything else)
> >
> > (2) a Faraday isolator only transmits one linear polarization - okay,
> how
> > about the following arrangement:
> >  F
> > S / F
> >
> > where S is the sample, / is an ideal 45-degree cube polarizing
> beamsplitter
> > which perfectly transmits say the p-polarization and perfectly
> reflects the
> > s-polarization, and F are two isolators consisting of a magnetic
> rotator
> > and an output linear polarizer (which perfectly reflects the
> rejected
> > polarization from the outside and perfectly transmits the other
> > polarization from both sides) oriented at 45 degrees (to pass the
> rotated
> > light in the usual way). Radiation from the outside which passes
> through
> > either F gets sent out through the open bottom channel of the cube.
> Notice
> > that I have studiously avoided absorption in all components so there
> is
> > nothing to heat up the sample.
> >
> > Carl Mungan <cmungan@uwf.edu> (who only reads the digest)