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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 23:25:55 -0000 (UTC)
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John Larkin <jjSNIPlarkin@highNONOlandtechnology.com> 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?
> 
> Rubidium clocks use an indirect way that doesn't actually divide.
> 
> 

Not really. There are optical parametric oscillators, but their phase noise
is horrible by comparison. A 1-cm-long crystal produces a nice tunable
output, but its line width will be c/1cm wide. 

Degenerate OPOs exist, whose signal and idler are at the same frequency,
but I believe their phase noise is not that different—there’s an additional
degree of freedom in the signal/idler relationship that would have to be
constrained somehow. 

Cheers 

Phil Hobbs 

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