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

Bob kb8tq kb8tq at n1k.org
Thu Feb 22 08:53:38 EST 2018


> On Feb 22, 2018, at 8:22 AM, Attila Kinali <attila at kinali.ch> wrote:
> 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. 

The point is that it’s clean where it matters. It does not dump a bunch of
energy into the transitions that you want to avoid.


>> 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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