[time-nuts] Current state of optical clocks and the definition of the second

[paul swed]

Interestingly they use regenerative dividers.
Pretty good read.
Thanks
Paul
WB8TSL

On Tue, Jan 13, 2015 at 4:49 PM, Tom Knox <actast at hotmail.com> wrote:

> I think the key to this concept is an optical comb filter.
> Archita Hati of the Phase Noise measurement Group at NIST has been
> researching ultra low phase noise 5MHz references using an optical
> standard and comb filter
> as well as extensive RF components to down converting to the desired
> frequency.
> In experiments I believe she has achieved phase noise better then -154db @
> 1Hz offset.
> It does appear to be the future but currently is far to large and complex
> for most if any
> practical use. I believe this link is the paper by Archita Hati I referred
> addressing
> State-of-the-Art RF Signal Generation From Optical Frequency Division.
> http://tf.boulder.nist.gov/general/pdf/2646.pdf
> Enjoy;
> Thomas Knox
>
> Thomas Knox
>
>
>
> > From: namichie at gmail.com
> > Date: Wed, 14 Jan 2015 07:00:09 +1100
> > To: time-nuts at febo.com
> > CC: namichie at gmail.com
> > Subject: Re: [time-nuts] Current state of optical clocks and the
> definition   of the second
> >
> >
> > THe stability /accuracy of lasers is entirely dependent on the cavity
> length.
> > Materials used are usually invar or silica, so you are no better off than
> > with a quartz crystals.
> > They are just a resonant cavity.
> > cheers,
> > Neville Michie
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