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

[Attila Kinali]

On Tue, 18 Feb 2020 14:21:46 +0100
Attila Kinali <attila at kinali.ch> wrote:

> LED, not laser diode. A LED has a bandwidth in the range of 10-40nm,
> enough to cover the necessary frequency/wavelength even with production
> variation. A laser diode is somewhere in the 100MHz range (unless ECDL),
> which means the wavelength has to be tuned to the right one in order
> for the system to work. Advantage of the laser: can be very narrow band
> (order of 100kHz is readily achievable) and thus have less AC Stark shift.
> But you need a lot of electronics and control loops to keep it where it
> should be. LEDs on the other hand are drop-in replacements which need a
> very small bit of electronics (bascially just a constant current source
> is enough). But they need the 85Rb filter to filter out the "wrong"
> wavelength, like the Rb lamps do.

Addendum: Whether you use linear polarized light or circular polarized /
unpolarized light is more a matter of taste, as far as I understand.
It seems that for a double resonance systems, circular/unpolarized is
easier to do, while for CPT/EIT the jury is still out on which one to use.

In case you didn't know: LEDs are (generally) unpolarized, while laser
diodes are usually eliptical polarized ie one polarization axis is 
(usually much) stronger than the other.

				Attila Kinali

-- 
In science if you know what you are doing you should not be doing it.
In engineering if you do not know what you are doing you should not be doing it.
        -- Richard W. Hamming, The Art of Doing Science and Engineering