[time-nuts] HP5065B !!!

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Apr 28 18:28:55 UTC 2013


Attila Kinali wrote:
> On Sun, 28 Apr 2013 17:50:06 +1200
> Bruce Griffiths<bruce.griffiths at xtra.co.nz>  wrote:
>
>    
>> Has anyone considered a laser pumped variant like:
>> http://tf.nist.gov/general/pdf/1009.pdf
>>
>> Apart from the ECDL laser (can be assembled using readily availalble
>> parts) it looks fairly straightforward.
>>      
> Considered, yes, tried, no. From what i've read sofar, this system
> has the problem of locking the laser wavelength onto the right
> absorbtion line. IIRC the linewidth of Rb in a vapor cell is a couple
> of 10kHz to a few 100kHz. Using an ECDL you get a laser linewidth of
> less than 1MHz easily, usally in the range of a few 100kHz and less.
> Ie. the laser would need to be kept on the absorption line with a stability
> of a couple of 100kHz at most. Using just a laser diode (without the
> external cavity) with its linewidth of>100MHz makes it actually a
> little bit easier to handle.
>    
But the pump laser is then too noisy to allow a low noise rubidium 
standard to be implemented.
With a temperature stabilised ECDL locking the laser to the D1 or D2 
rubidium absorption feature whilst simultaneously stabilising the laser 
beam power can easily be achieved.
> But getting the laser to the right Rb absorption line and detecting whether
> it's off is still not solved. Most of the papers that i've read that do
> something similar use an additional vapor cell to determine the correct
> position of the laser.
>
> I'm quite sure that it could be done with a single vapor cell using
> some sophisticated control loop that steers both the 6.9Ghz signal
> and the laser wavelength, but i doubt it's easy. But then, i didn't
> have an in depth look at this.
>
>
> 			Attila Kinali
>    
Bruce



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