Path: ...!news.nobody.at!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Phil Hobbs 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) Organization: A noiseless patient Spider Lines: 105 Message-ID: References: <1ccn3jd9ql2fms3jufgolcru50gh83slk1@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Thu, 09 May 2024 01:25:56 +0200 (CEST) Injection-Info: dont-email.me; posting-host="e32ac61c3fa108018fad465cdface15e"; logging-data="264882"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18fgOa1cgGUAAHvQ+yb+0tf" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:0YVwQC2X65WEINqvpzpIVVUHWN4= sha1:wgl0biSvPk9GvnUEv9U5yISEFdA= Bytes: 5618 John Larkin wrote: > On Wed, 8 May 2024 14:45:42 -0000 (UTC), Phil Hobbs > 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 >>>>> wrote: >>>>> >>>>>> On Tue, 7 May 2024 16:26:27 +0200, Jeroen Belleman >>>>>> 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