[time-nuts] Pressure sensitivity of Rb vapor cell standards

[Bruce Griffiths]

Magnus

You need a linear polariser plus a quarter waveplate to produce circularly polarised light from unpolarised light. A quarter waveplate alone wont suffice. So called circular polarisers used with modern digital cameras comprise a polariser with the linear polariser oriented correctly with respect to the following quarter waveplate to produce circularly polarised light. No idea how effective these are at 780nm as quarter waveplates can be relatively narrowband unless an achromatic stack is used.
Does it matter whether LH or RH circularly polarised light is used?

Bruce 
> On 19 February 2020 at 01:42 Magnus Danielson <magnus at rubidium.se> wrote:
> 
> 
> Hi,
> 
> On 2020-02-18 11:06, Attila Kinali wrote:
> > On Mon, 17 Feb 2020 18:16:04 -0600
> > magnus <magnus at rubidium.se> wrote:
> >
> >> Hi,In the 5065 and most others, the light intensity is not stabilized.
> >> It should not be too hard to regulate the Rb lamp amplitude and servo
> >> it to light intensity from the detector. Didn't Poul-Henning check this?
> >
> > I still think, replacing the 5065 lamp with a 780nm LED would be worthwhile
> > to try. Yes, the LEDs have a broader spectrum than a lamp, but it is a lot
> > easier to keep it stable than a fluerescent lamp. It would also allow to
> > lower the temperature of the Rb cell to get to the zero tempco point (which
> > seems to be around 60°C for most mixtures).
> 
> Well, as I recall it one has to have a quarter-wave window to remove
> polarization issues, as that too creates light-shift issues. Also, one
> wants a beam-expander to optically cover more of the cavity than the
> direct laser do. I have a bunch of 780 nm LED-lasers for this purpose,
> but it would be fun to try even as quick-hack.
> 
> So, nothing unsolveable, but things to attend to.
> 
> Cheers,
> Magnus
> 
> 
> 
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