[time-nuts] advice

Attila Kinali attila at kinali.ch
Wed Feb 22 20:19:28 EST 2017

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

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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