[time-nuts] LED instead of discharge lamp for Rb vapor cell standards

Attila Kinali attila at kinali.ch
Thu Feb 22 08:22:36 EST 2018

On Wed, 21 Feb 2018 18:10:17 +0000
"Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:

> >So the Rb85 "notch" filter might not get rid of all the unwanted light
> >and some of this might depopulate the excited state of the Rb87
> >that are in the RF cavity.
> I have a hard time seeing how you can not get worse S/N that way.

Well, the question is how much? Keep in mind that an Rb lamp is
anything but a clean light source. 

> If you want to do it with a LED, I think it needs to be a stabilized
> LED-Laser.

The problem with a Laser is that you need to lock it to the
right line. This requires either some significant change to the
electronics of the Rb standard, or an additional vapor cell and
some optics to lock it to that cell. Neither is trivial (apparently,
according to the papers I've read, not difficult, but I don't trust
that until I have tried myself).

			Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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