[time-nuts] advice

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Feb 22 21:51:52 EST 2017

Perhaps one could use a laser stabilised to an atomic absorption line to interrogate an atomic absorption cell or equivalent in the other location via optical fiber using the absorption cell as a frequency discriminator. Trapped ion or Bose-Einstein condensates could be used in the absorption "cells".

    On Thursday, 23 February 2017 3:09 PM, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:

 It would be better to lock the laser to a suitable optical absorption line or other optical transition.Long term stability can be better than an optical cavity provided the absorption cell parameters are stabilised. Other techniques such as using  a Bose Einstein condensate can be helpful.

    On Thursday, 23 February 2017 3:02 PM, Attila Kinali <attila at kinali.ch> wrote:

 On Wed, 22 Feb 2017 00:54:34 -0800
Hal Murray <hmurray at megapathdsl.net> wrote:

> How stable is a good laser and/or how hard do I have to work (or how much do 
> I have to pay) to get one stable enough for this experiment?  What's the line 
> width on a typical laser?  How much does it wander with temperature and 
> supply voltage and phase of the moon?

A normal ECDL system gets a line width sub 1MHz pretty easily, the better
ones are in the order of 10-100kHz. With the right stabilization system
sub 1Hz linewidths can be achieved [1,2]. Stability is in the order
of 10^-14 to 10^-16 (ADEV/MDEV) from 1s to a few 100s. Long term seems
to be limited by temperature stability, creep of spacer material and
mirror aging (no particular order).
I haven't had a look at this topic in a while so I cannot tell you
what the current state of the art is.

            Attila Kinali

[1] "Sub-hertz-linewidth diode laser stabilized to an ultralow-drift
high-finesse optical cavity", by Hirata, Akatsuka, Ohtake, Morinaga,

[2] "A sub-40-mHz-linewidth laser based on a silicon single-crystal
optical cavity", Kessler, Hagemann, Grebing, Legero, Sterr, Riehle,
Martin, Chen, Ye, 2012

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