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From: Jeroen Belleman <jeroen@nospam.please>
Newsgroups: sci.electronics.design
Subject: Re: OT: Atomic nucleus excited with laser: a breakthrough after
 decades
Date: Wed, 8 May 2024 23:08:35 +0200
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On 5/8/24 19:11, John Larkin wrote:
> On Wed, 8 May 2024 14:45:42 -0000 (UTC), Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
> 
>> 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
>>>>>>>>> ?tps://www.sciencedaily.com/releases/2024/04/240429103045.htm>
>>>>>>>>> ?e 'thorium transition', which has been sought after for
>>>>>>>>> decades,
>>>>>>>>> ?s now been excited for the first time with lasers.
>>>>>>>>> ?is 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.? 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
> 
> Is there any way to divide a lightwave down into the electronic
> frequency domain?

Not to my knowledge. The usual way is down-mixing. The optical
frequency comb provides a way to generate an accurately known
optical local oscillator, so to speak.

Jeroen Belleman