[time-nuts] Current state of optical clocks and the definition of the second

[Gregory Maxwell]

On Mon, Jan 12, 2015 at 12:34 PM, Attila Kinali <attila at kinali.ch> wrote:
> I just stumbled over this [1] nice article by Fritz Riehle that might be
> of interest to others as well.

I've seen less discussion of non-atomic stable optical oscillators.
Most (all?) of these optical atomic standards are passive atomic
clocks and need a free running oscillator.

Seems that the state of the art in stabilized lasers has improved a
lot lately, e.g. there are commercial available 1550nm devices which
have a <=3Hz line-width: http://stablelasers.com/products.html (well
on a short term basis, the medium term performance is not so
impressive)

Considering the rarity and extreme cost of H-masers, or just really
exceptional quarts oscillators; might it be the case that optical LOs
start looking interesting for applications which just need stability
(or being steered by other sources; e.g. GPSDL)?
(They can be down-converted to microwave frequencies using an optical
comb; a mode-locked laser whos pulses are phase locked to an incoming
beam.)

Certainly just the local oscillator is _closer_ to something a
time-nut might experiment with than a complete optical atomic standard
(if still not quite in reach).