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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: OT: Atomic nucleus excited with laser: a breakthrough
 after decades
Date: Wed, 8 May 2024 14:45:42 -0000 (UTC)
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Martin Brown <'''newspam'''@nonad.co.uk> wrote:
> On 08/05/2024 09:44, Jeroen Belleman wrote:
>> On 5/8/24 01:36, John Larkin wrote:
>>> On Tue, 07 May 2024 12:17:24 -0400, Joe Gwinn <joegwinn@comcast.net>
>>> wrote:
>>> 
>>>> On Tue, 7 May 2024 16:26:27 +0200, Jeroen Belleman
>>>> <jeroen@nospam.please> wrote:
>>>> 
>>>>> On 5/7/24 15:35, Martin Brown wrote:
>>>>>> On 07/05/2024 06:06, Jan Panteltje wrote:
>>>>>>> Atomic nucleus excited with laser: a breakthrough after decades
>>>>>>> ÿÿ <https://www.sciencedaily.com/releases/2024/04/240429103045.htm>
>>>>>>> ÿÿÿ The 'thorium transition', which has been sought after for 
>>>>>>> decades,
>>>>>>> ÿÿÿ has now been excited for the first time with lasers.
>>>>>>> ÿÿÿ This paves the way for revolutionary high precision technologies,
>>>>>>> including nuclear clocks
>>>>>> 
>>>>>> I wonder what the Q value for stimulated nuclear emission is?
>>>>>> 
>>>>> 
>>>>> They state a centre frequency of roughly 2 PHz and a decay time
>>>>> of 630s, which would put the Q in the 1e19 ballpark. Prodigious.
>>>>> No wonder it was hard to find.
>>>> 
>>>> The Time guys have been looking for this forever, so to speak.
>>>> 
>>>> It's the only atomic kernel transition with any degree of coupling to
>>>> electromagnetic radiation.ÿ This will be orders of magnitude better
>>>> than such as lattice clocks.
>>>> 
>>>> There will be a flood of papers.
>>>> 
>>>> Joe Gwinn
>>> 
>>> They aren't tuning to a resonance, but to the difference between two
>>> close resonances.
>> 
>> The current definition of the second uses something similar: Some
>> hyperfine resonance of cesium. Normal resonances are in the optical
>> domain, but hyperfine ones are RF.
> 
> Which puts them in the RF frequency domain where counting cycles of the 
> continuous sine reference waveform is relatively easy.
> 
> Likewise for H-maser another favourite local time reference signal.
> 
>> In nuclei, normal transitions are in the gamma domain, and
>> hyperfine ones are in the domain of optics. It's just a change
>> of scale, if you will.
> 
> Although there will be some big practical difficulties counting cycles 
> of a waveform at 8eV which is up into the UV. What is the current 
> highest frequency that a semiconductor divider is capable of accepting?
> 
> I know that there are some optical logic circuits about but how capable 
> are they at near UV light?
> 
> You can't mix this thing down without losing its fidelity. I know how to 
> double optical frequencies but how do you halve or quarter them?
> 

You mix with an optical frequency comb, possibly with an intermediate
locking step. 

The cleverest part of the Hall-Haensch comb generator is that you can lock
the blue end of the comb to the second harmonic of the red end, one tooth
off, and lock the difference to a good reference. Then all the teeth have
the same phase noise as the reference oscillator, rather than 20 log(600
THz /  100 MHz) ~ 138 dB worse, as it would be in a multiplier.  

That 0.002 Hz line width is going to make the locker design entertaining. 

Cheers 

Phil Hobbs 
-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics