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From: Joe Gwinn <joegwinn@comcast.net>
Newsgroups: sci.electronics.design
Subject: Re: OT: Atomic nucleus excited with laser: a breakthrough after decades
Date: Thu, 09 May 2024 17:56:06 -0400
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On Thu, 09 May 2024 14:26:12 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:

>On Wed, 8 May 2024 23:35:19 -0000 (UTC), Phil Hobbs
><pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>>Joe Gwinn <joegwinn@comcast.net> wrote:
>>> On Wed, 8 May 2024 14:45:42 -0000 (UTC), Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>> 
>>> [snip]
>>> 
>>>> 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.  
>>> 
>>> Hmm.  It had to be true, but I never connected the dots there.  What
>>> is mechanism by which this is achieved?  References?
>>> 
>>> Thanks,
>>> 
>>> Joe Gwinn
>>> 
>>
>>Don’t have the reference handy, but the basic idea is to use a modelocked
>>system Ti:sapphire laser at 750 nm to generate ~100-fs pulses, then use
>>fiber/grating pulse compression to bring that down to a few femtoseconds,
>>followed by a holey fiber to broaden the spectrum to more than an octave. 
>>
>>Jan Hall is one of the best instruments guys ever. 
>
>I'll poke around his publications.  He's bound to have left tracks.

The best source I've found so far is:

Optical and microwave metrology with frequency combs
Tara Fortier
NIST Time and Frequency Division
Oct 10, 2023 

And 

COMMUNICATIONS PHYSICS | (2019)2:153 |
https://doi.org/10.1038/s42005-019-0249-y | www.nature.com/commsphys

These are open access.

Joe Gwinn