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

[Magnus Danielson]

Hi,

On 02/22/2018 02:53 PM, Bob kb8tq wrote:
> Hi
> 
> 
>> 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.

780 nm vs 795 nm if I recall correctly. A dash of energy isn't too
critical, but it will de-pump the state and you will suffer with
somewhat worse S/N. For a rubidiumlamp the two "lines" are about the
same strength and fairly wide.

The one thing to care about is polarization, since that will be a
pulling through AC Stark so a quarter-wave window should be used.

Servo the LED to the detected lamp response should help with stabilization.

Cheers,
Magnus